Sustained Ventricular Tachycardia
1919CHAPTER 254
Acknowledgment
Roy M. John and William G. Stevenson contributed to this chapter in
the 20th edition, and some material from that chapter has been retained
here.
■ FURTHER READING
Al-Khatib SM et al: 2017 AHA/ACC/HRS guideline for management
of patients with ventricular arrhythmias and the prevention of sudden cardiac death: A report of the American College of Cardiology/
American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. Heart Rhythm 15:e73, 2018.
Callans DJ: Josephson’s Clinical Cardiac Electrophysiology: Techniques
and Interpretations, 6th ed. Philadelphia, Wolters Kluwer, 2021.
Cronin EM et al: 2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias. EP
Europace 21:1143, 2019.
Jalife J, Stevenson W (eds): Zipes and Jalife’s Cardiac Electrophysiology: From Cell to Bedside, 8th ed. Philadelphia, Elsevier, 2022.
Sustained monomorphic ventricular tachycardia (VT) is a ventricular
arrhythmia with a wide QRS lasting for 30 s or requiring an intervention for termination. Each QRS complex resembles the others,
indicating either a site of origin from either an automatic focus or
fixed reentry circuit. In structural heart disease, the substrate is most
often an area of patchy replacement fibrosis due to infarction, fibrosis,
inflammation, or prior cardiac surgery that creates anatomic or functional reentry pathways. Less commonly, VT is related to reentry or
automaticity in diseased conduction pathways in the Purkinje system.
While scar-related reentrant VTs are associated with risk of sudden
death, idiopathic VT is a more benign form of VT that occurs in structurally normal hearts and can be due to a focal region of automaticity in
the myocardium or reentry involving a portion of the Purkinje system.
The clinical presentation varies depending on the rate of the
arrhythmia, underlying cardiac function, and autonomic adaptation in
response to the arrhythmia. Rapid VT can produce hypotension that
may present as syncope, particularly in patients with significant ventricular dysfunction. In contrast, patients with normal cardiac function
might tolerate their sustained VT, even presenting with simple palpitations, despite rapid rates. Monomorphic VT that is rapid or associated
with structural heart disease may eventually deteriorate to ventricular
fibrillation (VF), which may be the initial cardiac rhythm recorded at
the time of resuscitation of an out-of-hospital cardiac arrest.
DIAGNOSIS
Sustained monomorphic VT (Table 254-1) has to be distinguished
from other causes of uniform wide QRS tachycardia. These include
supraventricular tachycardia with left or right bundle branch block
aberrant conduction, supraventricular tachycardias conducted to the
ventricles over an accessory pathway, and rapid cardiac pacing, appropriate or inappropriate, in a patient with a ventricular pacemaker or
defibrillator. In the presence of known heart disease, VT is the most
likely diagnosis of a wide QRS tachycardia, independent of QRS morphology. When left ventricular (LV) function is depressed or there is
evidence of structural myocardial disease, scar-related reentry is the
most likely cause of sustained monomorphic VT. Scars are suggested
by pathologic Q waves on the electrocardiogram (ECG), segmental LV
or right ventricular wall motion abnormalities on echocardiogram or
254 Sustained Ventricular
Tachycardia
William H. Sauer, Usha B. Tedrow
TABLE 254-1 Sustained Ventricular Arrhythmias
1. Idiopathic ventricular tachycardia (VT) without structural heart disease
A. Outflow tract origin
• Right ventricular (RV) outflow tract: left bundle branch block pattern in
V1
with inferior axis (tall QRS in inferior leads) and late transition in the
precordial leads
• Left ventricular (LV) outflow tract: similar inferiorly directed axis but
with early precordial transition with prominent R wave in V2
–V3
B. LV fascicular VT: Typical right bundle branch block pattern in V1
with sharp
intrinsicoid deflection and left axis deviation (arising from left posterior
fascicle in its most common form)
C. Papillary muscle VT
• Posteromedial: atypical right bundle branch block pattern in V1
with
monophasic R wave and left axis deviation
• Anterolateral: atypical right bundle branch block pattern in V1
with
positive deflection in lead III and negative deflection in lead I
2. Ischemic cardiomyopathy
• Monomorphic VT is common with prior large myocardial infarction
• Polymorphic VT and ventricular fibrillation (VF) should prompt ischemia
evaluation
3. Nonischemic cardiomyopathy
• Fibrotic scars can cause monomorphic VT, especially with sarcoidosis
or other inflammatory cardiomyopathies, Chagas’ disease, and
familial arrhythmogenic cardiomyopathies such as Lamin A/C genetic
cardiomyopathy
• Polymorphic VT and VF can also occur independently or related to
degeneration of monomorphic VT
4. Arrhythmogenic RV cardiomyopathy
• Monomorphic VT usually of RV origin (left bundle branch morphology in V1
)
• Polymorphic VT and VF can occur independently or related to
degeneration of monomorphic VT
5. Repaired tetralogy of Fallot
• Monomorphic VT of RV origin (usually left bundle branch morphology in V1
)
6. Hypertrophic cardiomyopathy
• Polymorphic VT or ventricular fibrillation
• Less commonly, monomorphic VT associated with myocardial scars,
particularly apical aneurysms
7. Genetic arrhythmia syndromes
A. Long QT syndrome
• Torsades des pointes VT
B. Brugada syndrome
• Ventricular fibrillation episodes, often nocturnal
C. Catecholaminergic polymorphic VT
• Polymorphic VT or bidirectional VT
D. Short QT and early repolarization syndromes
• Ventricular fibrillation
8. Idiopathic polymorphic VT or ventricular fibrillation
• Usually triggered by recurrent premature ventricular contractions; the
most common site of origin is the left posterior fascicle (right bundle
branch block/left anterior fascicular block pattern)
nuclear imaging, and areas of delayed gadolinium enhancement during
magnetic resonance imaging (MRI).
Hemodynamic stability during the arrhythmia does not help distinguish between VT and other mechanisms of wide-complex tachycardia. A number of ECG criteria have been evaluated to distinguish
supraventricular tachycardia with aberrancy from VT. The presence of
ventriculoatrial (VA) dissociation is a reliable marker for VT, provided
the atrial rate is slower than the ventricular rate. Sometimes, P waves
can be difficult to define, and the VA relationship cannot be assessed
in a patient with an ongoing atrial arrhythmia such as atrial fibrillation. A P wave following each QRS does not exclude VT because 1:1
conduction from ventricle to atrium can occur. A monophasic R wave
or Rs complex in aVR or concordance from V1
to V6
of monophasic
R or S waves is also relatively specific for VT (Fig. 254-1). A number of other QRS morphology criteria have also been described, but
1920 PART 6 Disorders of the Cardiovascular System
No
Yes
Yes
Yes
No
No
VT versus Supraventricular Tachycardia (SVT)
with Aberrancy
Possible SVT with aberrancy
VT still possible
No rS or Rs in
any of V1 to V6
aVR = R or Rs
AV dissociation VT
VT
VT
V1 V2 V3 V4 V5 V6
V1 V2 V3
aVR aVR
V4 V5 V6
FIGURE 254-1 Algorithm for differentiation of ventricular tachycardia (VT) from
supraventricular tachycardia with aberration. AV, atrioventricular.
aVR
aVL
aVF
I
II
III
V1
V5
V1
V2
V3
V4
V5
V6
FIGURE 254-2 Monomorphic ventricular tachycardia in a patient with prior myocardial infarction. Shown is a wide-complex tachycardia. Complexes 3, 6, 9, and 18 are
narrower and are examples of fusion beats, proving ventriculoatrial (VA) dissociation and proving that this rhythm is in fact ventricular tachycardia.
all have limitations and are not very reliable in patients with severe
heart disease. In patients with known bundle branch block, the same
QRS morphology during tachycardia as during sinus rhythm suggests
supraventricular tachycardia rather than VT, but even this is not absolutely reliable. Patients with reentry involving the bundle branches of
the Purkinje system can have a VT morphology that resembles their
native QRS in sinus rhythm. An electrophysiologic study is sometimes
required for definitive diagnosis. Occasionally, noise and movement
artifacts on telemetry recordings can simulate VT. Prompt recognition
can avoid unnecessary tests and interventions.
TREATMENT AND PROGNOSIS
Initial management follows Advanced Cardiac Life Support (ACLS)
guidelines. If hypotension, impaired consciousness, or pulmonary
edema is present, QRS synchronous electrical cardioversion should
be performed, ideally after sedation if the patient is conscious. For
stable tachycardia, a trial of adenosine is reasonable as this may clarify
a supraventricular tachycardia with aberrancy. Adenosine should not
be used if the patient has a heart transplant or if the wide-complex
rhythm is irregular or unstable. Intravenous amiodarone is the drug
of choice if heart disease is present. Following restoration of sinus
rhythm, hospitalization and evaluation to define underlying heart
disease are required. Assessment of cardiac biomarkers for evidence
of myocardial infarction (MI) is appropriate, but acute MI is rarely a
cause of sustained monomorphic VT. Elevations in troponin or creatine kinase (CK)-MB are more likely to indicate myocardial damage
that is secondary to hypotension and ischemia from fixed coronary
lesions during the VT. Subsequent management is determined by the
underlying heart disease and frequency of VT. If VT recurs frequently
or is incessant, administration of antiarrhythmic medications or catheter ablation may be required to restore stability. More commonly,
sustained monomorphic VT occurs as a single episode but with a high
risk of recurrence. Implantable cardioverter defibrillators (ICDs) are
warranted for secondary prevention of sudden death in patients who
present with sustained VT associated with structural heart disease
(Fig. 254-2).
SUSTAINED MONOMORPHIC VT IN
SPECIFIC DISEASES
■ CORONARY ARTERY DISEASE
Patients who present with sustained monomorphic VT associated with
coronary artery disease typically have a history of a remote prior large
MI. Patients typically present years after the acute infarct with a remodeled ventricle and markedly depressed LV function. Even when there
is biomarker evidence of acute MI, a preexisting scar from previous
MI should be suspected as the cause of the VT. Infarct scars provide
a durable substrate for sustained VT, and up to 70% of patients have
a recurrence of the arrhythmia within 2 years. Scar-related reentry is
not usually dependent on recurrent acute myocardial ischemia, so coronary revascularization is unlikely to prevent recurrent VT, although
it may be appropriate for treatment of angina or other indications.
Depressed ventricular function, which is a risk factor for sudden death,
is usually present. Implantation of an ICD is clearly indicated for secondary prevention provided that there is a reasonable expectation of
survival for 1 year with acceptable functional status. Compared with
Sustained Ventricular Tachycardia
1921CHAPTER 254
antiarrhythmic drug therapy, ICDs reduce annual mortality from 12.3
to 8.8% and lower arrhythmic deaths by 50% in patients with hemodynamically significant sustained VT or a history of cardiac arrest. Antiarrhythmic drugs may have some utility for palliation of VT symptoms
and prevention of ICD therapies, such as shocks and antitachycardia
pacing; however, without an ICD, these drugs do not improve survival.
Following ICD implantation, patients with depressed ejection fraction remain at risk for clinical heart failure, recurrent ischemic events,
and recurrent VT, with a 5-year mortality that exceeds 30%. Attention
to guideline-directed medical therapy for patients with heart failure
and coronary artery disease, including β-adrenergic blocking agents
and angiotensin-converting enzyme inhibitors, is important.
ICD therapies, whether shocks or antitachycardia pacing, constitute
an adverse event for the patient and are associated with increased rates
of heart failure, mortality, and psychological stress. For this reason,
recurrent VT episodes in patients with an ICD warrant treatment with
medications or catheter ablation. In a randomized study of catheter
ablation versus escalated medical therapy (Ventricular Tachycardia
Ablation versus Escalation of Antiarrhythmic Drugs [VANISH]),
patients receiving catheter ablation fared better than those receiving
increasing doses of antiarrhythmic drugs, in particular, amiodarone.
Another randomized trial (BERLIN VT) examined a preventative
versus deferred ablation strategy in patients who had not yet failed
an antiarrhythmic drug. This trial was stopped early for futility, with
more procedural complications but fewer VT episodes in the catheter
ablation group. For this reason, the most recent consensus statement
most strongly recommends catheter ablation for patients with ischemic
cardiomyopathy failing or intolerant of antiarrhythmic drugs but also
allows for consideration of catheter ablation when long-term therapy
with an antiarrhythmic drug (such as amiodarone, which has significant long-term toxicities) is not desired.
■ NONISCHEMIC DILATED CARDIOMYOPATHY
Sustained monomorphic VT associated with nonischemic cardiomyopathy is usually due to scar-related reentry. The etiology of scar is often
unclear, but progressive replacement fibrosis is the likely cause. Patients
with nonischemic cardiomyopathy (NICM) have historically been
presumed to have a postviral etiology, although increasingly, genetic
causes are found in many. Inflammatory etiologies (myocarditis, sarcoidosis) are also increasingly appreciated. On cardiac MRI, scars are
detectable as areas of delayed gadolinium enhancement and are more
often intramural (Fig. 254-3) or subepicardial in location as compared
with patients with prior MI. Scars that cause VT are often located
adjacent to a valve annulus and can occur in either ventricle. Any cardiomyopathic process can cause scars and VT, but cardiac sarcoidosis,
Chagas’ disease, and cardiomyopathy due to Lamin A/C mutations are
particularly associated with monomorphic VT. An ICD is indicated for
patients with a history of sustained VT, syncope, or New York Heart
Association class II or III heart failure symptoms, with additional
drugs or catheter ablation for control of recurrent VT. In addition, for
patients with malignant familial arrhythmogenic cardiomyopathies, an
ICD may be considered earlier in the clinical course.
Overall, there are fewer studies of catheter ablation for VT in
NICM. Reported success rates are lower than VT ablation in ischemic
cardiomyopathy in most observational series. Additionally, inability to
reproduce the clinical VT at ablation attempts and epicardial and intramural reentry circuits are important causes of failure of endocardial
VT ablation in NICM. Imaging with MRI or computed tomography
(CT) scans with late contrast administration to define areas of fibrosis
can be useful to guide ablation.
ARRHYTHMOGENIC RIGHT VENTRICULAR
CARDIOMYOPATHY
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a rare
genetic disorder most commonly due to mutations in genes encoding for cardiac desmosomal proteins; however, it is increasingly
appreciated that other cardiomyopathic processes may produce a
similar phenotype. Approximately 50% of patients have a familial
transmission with autosomal dominant inheritance. A less common,
autosomal recessive form is classically associated with cardiocutaneous
syndromes that include Naxos disease and Carvajal syndrome. The
former is most commonly related to mutations in plakophilin-2 and
plakoglobin, while the latter is most commonly due to a mutation in
desmoplakin. Patients are typically diagnosed between the second and
fifth decades with palpitations, syncope, or cardiac arrest owing to
sustained monomorphic VT, although polymorphic VT can also occur.
Fibrosis and fibrofatty replacement most commonly involve the right
ventricular myocardium and provide the substrate for reentrant VT
that usually has a left bundle branch block–like configuration in ECG
lead V1
, consistent with the right ventricular origin, and can resemble
idiopathic VT. The sinus rhythm ECG suggests the disease in >85%
of patients, most often showing T-wave inversions in V1
–V3
. Delayed
activation of the right ventricle may cause a widened QRS (>110 ms)
in the right precordial leads (V1
–V3
) and a prolonged S-wave upstroke
in those leads and, occasionally, a notched deflection at the end of
the QRS known as an epsilon wave. Cardiac imaging may show right
ventricular enlargement or areas of abnormal motion or reveal areas of
scar on contrast-enhanced MRI.
LV involvement can occur and can occasionally precede manifest
right ventricular disease. Clinical heart failure is rare except in late
stages, and survival to advanced age can be anticipated provided that
VT can be controlled. An ICD is recommended. When VT is exercise
induced, it may respond to β-adrenergic blockers and limiting exercise. Sotalol, flecainide, and amiodarone have been used to reduce
ventricular arrhythmias. Catheter ablation prevents or reduces VT
episodes in 70% of patients, but epicardial mapping and ablation are
often required.
ADULT CONGENITAL HEART DISEASE
Among all patients with adult congenital heart disease (ACHD), sustained monomorphic VT is quite rare. However, the most common
substrate for sustained VT is seen in those with repairs of a ventricular
septal defect, in particular tetralogy of Fallot (TOF). The prevalence of
VT after TOF repair is estimated to be 3–14%, and risk of sudden cardiac death may reach as high as 1% per year in adulthood by the fourth
or fifth decade of life. The greatest risk for ventricular arrhythmias is
posed via two potential mechanisms: (1) those who have undergone
repair involving a ventriculotomy and (2) those with long-standing
FIGURE 254-3 Cardiac magnetic resonance image (MRI). Shown is an MRI of the
heart with the right ventricle on the left and the left ventricle on the right. Between
the ventricles (arrows) is a stripe of late gadolinium enhancement, indicating
midmyocardial fibrosis in the interventricular septum. This type of scar pattern
is often seen in patients with nonischemic cardiomyopathies and ventricular
tachycardia.
1922 PART 6 Disorders of the Cardiovascular System
hemodynamic overload causing ventricular dysfunction and/or hypertrophy independent of surgical incisions.
Monomorphic VT in TOF most commonly occurs in stereotyped
circuits due to reentry around areas of surgically created scar in the
right ventricle. Factors associated with VT risk include age >5 years at
the time of repair, high-grade ventricular ectopy, inducible VT on an
electrophysiologic study, abnormal right ventricular hemodynamics,
and sinus rhythm QRS duration >180 ms. An ICD is usually warranted
for patients who have a spontaneous episode of VT, but ICDs are also
considered for patients with multiple risk factors. Catheter ablation
or antiarrhythmic drug therapy is used to control recurrent episodes.
BUNDLE BRANCH REENTRY VT
Reentry through the Purkinje system occurs in ~5% of patients with
monomorphic VT in the presence of structural heart disease. The
reentry circuit typically revolves retrograde via the left bundle and
anterograde down the right bundle, thereby producing VT that has a
left bundle branch block configuration. The VT QRS morphology may
closely resemble the QRS morphology in sinus rhythm. Catheter ablation of the right bundle branch abolishes this VT. Bundle branch reentry is usually associated with severe underlying heart disease. Other
scar-related VTs are often present and often require additional therapy.
IDIOPATHIC MONOMORPHIC VT
Idiopathic VT in patients without structural heart disease usually
presents with palpitations, lightheadedness, and, rarely, syncope. Episodes and can be provoked either by sympathetic stimulation or acute
withdrawal of sympathetic tone, as in the immediate postexercise
period. The QRS morphology of the arrhythmia suggests the diagnosis
(see below). The sinus rhythm ECG is normal. Family history suggests
no familial cardiomyopathy or sudden death. Cardiac imaging, including echocardiography and cardiac MRI, shows normal ventricular
function and no evidence of ventricular scar. Occasionally, a patient
with structural heart disease is found to have concomitant idiopathic
VT unrelated to the structural disease, in which case, the underlying
disease should be treated as per the guidelines, separate from the VT.
Repeated bursts of nonsustained VT, which may occur incessantly,
are known as repetitive monomorphic VT and can cause a tachycardia-induced cardiomyopathy with depressed ventricular function
that recovers after suppression of the arrhythmia. Sudden death in
isolated idiopathic VT is rare, and an ICD is not recommended.
Outflow tract VTs originate from a focus near the pulmonic or
aortic valve annuli, usually with features consistent with triggered
automaticity. The arrhythmia may present with sustained VT, nonsustained VT, or premature ventricular contractions (PVCs). Most originate in the right ventricular outflow tract, which gives rise to VT that
has a left bundle branch block configuration in V1
and an axis that is
directed inferiorly, with tall R waves in II, III, and aVF. Idiopathic VT
can also arise in the LV outflow tract or in sleeves of myocardium that
extend along the aortic root. LV origin is suspected when lead V1
or V2
has prominent R waves. Although this typical outflow tract QRS morphology favors idiopathic VT, some cardiomyopathies, notably ARVC,
can cause PVCs or VT from this region. Excluding these diseases is an
initial focus of evaluation (Fig. 254-4).
LV fascicular VT, sometimes referred to as Belhassen’s VT or
verapamil-sensitive VT, is the second most common form of idiopathic
VT after outflow tract VTs. It often presents with sustained VT that
has a right bundle branch block–like configuration and is negative in
the inferior leads. It is often exercise induced and occurs more often in
men than women. The mechanism was originally thought to be focal
but has been demonstrated to be due to a small reentry circuit in or
near the septal ramifications of the LV Purkinje system. There can be
an LV false tendon associated with this rhythm.
Other sites of origin for idiopathic VT exist, including papillary
muscles, mitral and tricuspid valve annuli, and the moderator band
in the right ventricle. Even focal sites from the epicardial surface
have been described. The presence of VT from these more unusual
sites should prompt even more careful assessment for structural heart
disease.
MANAGEMENT OF IDIOPATHIC VT
Treatment is required for symptoms or when frequent or incessant
arrhythmias depress ventricular function. Symptoms can be controlled
with medications including beta blockers, calcium channel blockers,
and sodium channel blockers such as flecainide. Although flecainide is
not typically recommended in patients with structural heart disease, it
has been used successfully to resolve tachycardia-induced cardiomyopathy in the setting of idiopathic PVCs and VT. Catheter ablation is also
I
II
III
aVR
aVL
aVF
V1
V2
V3
V4
V5
V6
FIGURE 254-4 Idiopathic monomorphic ventricular tachycardia (VT). This is a 12-lead electrocardiogram showing the onset of idiopathic VT in a young patient without
structural heart disease. The VT has a left bundle branch block configuration in V1
and an inferiorly directed axis consistent with an outflow tract origin. Note that the narrow
(normal sinus) beats have a normal QRS configuration, consistent with the patient’s lack of structural heart disease.
Polymorphic Ventricular Tachycardia and Ventricular Fibrillation
1923CHAPTER 255
FIGURE 254-5 Stereotactic body radiation therapy. Shown is a planning computed tomography scan for noninvasive cardiac ablation delivered with stereotactic radiation.
The region of interest is determined by analysis of presenting arrhythmias, underlying structural heart disease, and proximity to adjacent structures such as coronary
arteries, the phrenic nerve, and the gastrointestinal tract. Radiation is delivered to the chosen treatment volume in order to create conduction block in the culprit scar region.
indicated for control of symptoms, has an overall success rate of 80%,
and is recommended for those with symptomatic VT in whom medications are ineffective or not preferred by the patient. Efficacy and risks
of catheter ablation vary with the specific site of origin of the VT, being
most favorable for arrhythmias originating in the right ventricular outflow tract. Failure of ablation is most often due to inability to initiate
the arrhythmia for mapping in the electrophysiology laboratory.
LV interfascicular VT can be terminated by intravenous administration of verapamil, although chronic therapy with oral verapamil is
not always effective. Catheter ablation is recommended if β-adrenergic
blockers or calcium channel blockers are ineffective or not desired.
FUTURE DIRECTIONS
Treatment of monomorphic VT, especially in the setting of structural
heart disease, is an important cause of morbidity and mortality. Limitations of current therapies include toxicities of antiarrhythmic drugs
and inability to successfully perform catheter ablation of the substrate
for arrhythmias. Advances in imaging and intracardiac mapping techniques are likely to improve success rates over time. In addition, the
inability of ablative energy to reach deep intramural substrates is a
current limitation. Innovations in delivery of ablative energy, including bipolar ablation, needle catheter ablation, and electroporation,
are ongoing. In addition, noninvasive ablation is a promising area of
investigation. Proton beam or stereotactic radiation can be used to target VTs identified by advanced cardiac imaging or by a multielectrode
ECG vest. Early multicenter studies suggest durable control of VT with
noninvasive ablation (Fig. 254-5).
Acknowledgment
Roy M. John and William G. Stevenson contributed to this chapter in the
20th edition, and some material from that chapter has been retained here.
■ FURTHER READING
Al-Khatib SM et al: 2017 AHA/ACC/HRS guideline for management
of patients with ventricular arrhythmias and the prevention of sudden cardiac death: A report of the American College of Cardiology/
American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. Heart Rhythm 15:e73, 2018.
Callans DJ: Josephson’s Clinical Cardiac Electrophysiology: Techniques
and Interpretations, 6th ed. Philadelphia, Wolters Kluwer, 2021.
Cronin EM et al: 2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias. EP
Europace 21:1143, 2019.
Jalife J, Stevenson W (eds): Zipes and Jalife’s Cardiac Electrophysiology:
From Cell to Bedside, 8th ed. Philadelphia, Elsevier, 2021.
Sapp JL et al: Ventricular tachycardia ablation versus escalation of antiarrhythmic drugs. N Engl J Med 375:111, 2016.
Willems S et al: Preventive or deferred ablation of ventricular tachycardia in patients with ischemic cardiomyopathy and implantable
defibrillator (BERLIN VT): A multicenter randomized trial. Circulation 141:1057, 2020.
POLYMORPHIC VENTRICULAR
TACHYCARDIA
Sustained polymorphic ventricular tachycardia (VT) has a continuously
changing QRS configuration from beat to beat, indicating a continually
changing ventricular activation sequence. However, unlike sustained
monomorphic VT, polymorphic VT does not necessarily indicate a
fixed structural abnormality or focus of automaticity. Reentry can occur
with continually changing reentrant paths, spiral wave reentry, and
multiple automatic foci as potential mechanisms. This type of reentry
255 Polymorphic Ventricular
Tachycardia and
Ventricular Fibrillation
William H. Sauer, Usha B. Tedrow
1924 PART 6 Disorders of the Cardiovascular System
can occur near fibrotic areas of myocardium, potentiated by proximity
to damaged Purkinje cells or ventricular hypertrophy. Abnormal transmural dispersion of repolarization can occur in the setting of channelopathies or antiarrhythmic drugs in the absence of structural heart
disease. Sustained polymorphic VT usually degenerates into ventricular
fibrillation (VF). Polymorphic VT is typically seen in association with
acute myocardial infarction or ischemia (MI), ventricular hypertrophy,
and a number of genetic mutations that affect cardiac ion channels.
POLYMORPHIC VT ASSOCIATED WITH
ACUTE MYOCARDIAL INFARCTION/
ISCHEMIA
Acute MI or ischemia is a common cause of polymorphic VT and
should be the initial consideration in management. Approximately
10% of patients with acute MI develop VT that degenerates to VF,
likely related to reentry through the infarct border zone. The risk is
greatest in the first hour of acute MI. More rarely, surviving Purkinje
cells with automaticity can initiate polymorphic VT. Following defibrillation as per the Advanced Cardiac Life Support (ACLS) guidelines,
management is as for acute MI. β-Adrenergic blockers, correction
of electrolyte abnormalities, and prompt myocardial reperfusion are
required. Repeated episodes of polymorphic VT may suggest ongoing
MI and warrant assessment of adequacy of myocardial reperfusion.
Polymorphic VT and VF that occur within the first 48 h of acute MI
are associated with greater in-hospital mortality, but patients who
survive past hospital discharge are not at increased risk for arrhythmic
sudden death. Long-term therapy for postinfarct ventricular arrhythmia is determined by residual left ventricular (LV) function, with an
implantable cardioverter defibrillator (ICD) indicated for persistent
severe LV dysfunction (LV ejection fraction <35%).
REPOLARIZATION ABNORMALITIES AND
GENETIC ARRHYTHMIA SYNDROMES
■ ACQUIRED LONG QT SYNDROME
Abnormal prolongation of the QT interval is associated with the polymorphic VT torsades des pointes. The VT often has a characteristic
QT = 680 ms
Sinus
beat
I
II
III
II
V1
aVR
aVL
aVF
V1
V2
V3
V4
V5
V6
II
V1
V1
PVC
Long interval Short
interval
Initiating beat of
polymorphic VT
A
B
FIGURE 255-1 Torsades des pointes ventricular tachycardia (VT) in a patient with bradycardia and marked QT prolongation. A. Twelve-lead electrocardiogram showing 2:1
atrioventricular block (P waves marked by blue arrows) with a heart rate of 40 beats/min and QT interval of 680 ms and corrected QT of 550 ms. B. The bottom panel shows
a telemetry rhythm strip with periods of self-limiting torsades des pointes polymorphic VT. Following a normally conducted sinus beat, a premature ventricular contraction
(PVC) causes a compensatory pause, leading to a long RR interval. A PVC after the next sinus beat initiates VT. This is the classic pause-dependent mode of initiation of
torsades des pointes VT with long–short intervals.
initiation sequence of a premature ventricular beat that induces a pause,
followed by a sinus beat that has a longer QT interval and interruption
of the T wave by the premature ventricular contraction (PVC) that is
the first beat of the polymorphic VT (Fig. 255-1). This characteristic initiation is termed pause-dependent. Causes of QT prolongation
include electrolyte abnormalities, bradycardia, and a number of
medications that block repolarizing potassium currents, notably the
antiarrhythmic drugs sotalol, dofetilide, and ibutilide, but also a number of other medications used for noncardiac diseases, including erythromycin, pentamidine, haloperidol, phenothiazines, and methadone.
Individual susceptibility may be related to genetic polymorphisms or
mutations that influence repolarization. The website crediblemeds.org
is an excellent resource for the clinician to determine whether a given
medication has been reported to prolong the QT interval.
Patients typically present with near-syncope, syncope, or cardiac
arrest. Sustained episodes degenerate to VF requiring defibrillation.
PVCs and nonsustained VT often precede episodes of sustained VT.
Intravenous administration of 1–2 g of magnesium sulphate usually
suppresses recurrent episodes. If magnesium alone is ineffective,
increasing heart rate with isoproterenol infusion or pacing, to a rate
of 100–120 depolarizations/min as required to suppress PVCs, usually
suppresses VT recurrences. These maneuvers allow time for correction
of associated electrolyte disturbance (hypokalemia and hypocalcemia)
and bradycardia and removal of any causative drugs (Table 255-1).
Drug interactions that elevate levels of the offending agent are often
a precipitating factor. Patients who experience a polymorphic VT
induced by QT prolongation should be considered to have a susceptibility to the arrhythmia and should avoid all future exposure to medications known to prolong the QT interval.
■ CONGENITAL LONG QT SYNDROME
The congenital long QT syndrome (LQTS) is caused by mutations in
genes coding for cardiac ion channels responsible for ventricular repolarization. The corrected QT (QTc) is typically prolonged to >440 ms
in men and 460 ms in women. Symptoms are due to torsades des
pointes VT. Several forms of congenital LQTS have been identified, but
three groups of mutations that lead to LQTS-1, LQTS-2, and LQTS-3
Polymorphic Ventricular Tachycardia and Ventricular Fibrillation
1925CHAPTER 255
syndromes account for 90% of cases. The most frequently encountered
mutations (LQTS-1 and LQTS-2) are due to abnormalities of potassium channels, but mutations affecting the sodium channel (LQTS-3)
and calcium channels have also been described.
Typical presentation is with syncope or cardiac arrest, usually during childhood. In LQTS-1, episodes tend to occur during exertion,
particularly swimming. In LQTS-2, sudden auditory stimuli or emotional upset predisposes to events. In LQTS-3, sudden death tends to
occur during sleep. Asymptomatic patients may be discovered in the
course of family screening or on a routine electrocardiogram (ECG).
Genotyping can be helpful for family screening and to provide reassurance regarding the diagnosis. Correlations of genotype with risk and
response to therapy are beginning to emerge. In most patients with
LQTS-1 or LQTS-2, adequate doses of beta-blocker therapy (the nonselective agents nadolol and propranolol are favored) are sufficient protection from arrhythmia episodes. Markers of increased risk include
QTc interval exceeding 500 ms, female gender, and a history of syncope
or cardiac arrest. Recurrent syncope despite beta-blocker therapy or
a high-risk profile merits consideration of an ICD. Avoidance of QTprolonging drugs is critical for all patients with LQTS, including those
who are genotype positive but have normal QT intervals.
■ SHORT QT SYNDROME
Short QT syndrome is very rare compared to LQTS. The QTc is <360 ms
and usually <300 ms. The genetic abnormality causes a gain of function
of the potassium channel (IKr) or reduced inward depolarizing currents.
The abnormality is associated with atrial fibrillation, polymorphic VT,
and sudden death.
■ BRUGADA SYNDROME
Brugada syndrome is a rare syndrome characterized by >0.2 mV of
ST-segment elevation with a coved ST segment and negative T wave
in more than one anterior precordial lead (V1
–V3
) (see Fig. 253-1) and
episodes of syncope or cardiac arrest due to polymorphic VT in the
absence of structural heart disease. Cardiac arrest may occur during
sleep or be provoked by febrile illness. Males are more commonly
affected than females. Mutations involving cardiac sodium channels
are identified in ~25% of cases. Distinction from patients with similar
ST elevation owing to LV hypertrophy, pericarditis, myocardial ischemia or MI hyperkalemia, hypothermia, right bundle branch block, and
arrhythmogenic right ventricular cardiomyopathy is often difficult.
Furthermore, the characteristic ST-segment elevation can wax and
wane over time and may become pronounced during acute illness and
fever. Administration of the sodium channel–blocking drugs flecainide, ajmaline, or procainamide can augment or unmask ST elevation in
affected individuals. An ICD is indicated for individuals who have had
unexplained syncope or been resuscitated from cardiac arrest. Quinidine and catheter ablation of abnormal regions in the epicardial right
ventricular free wall have been used successfully to suppress frequent
episodes of VT.
■ EARLY REPOLARIZATION SYNDROME
Patients resuscitated from VF who have no structural heart disease or
other identified abnormality have a higher prevalence of J-point elevation with notching in the terminal QRS. A family history of sudden
death is present in some patients, suggesting a potential genetic basis.
J-point elevation is also seen in some patients with the Brugada syndrome and is associated with a higher risk of arrhythmias. An ICD is
recommended for those who have had prior cardiac arrest. It should be
noted that J-point elevation is commonly seen as a normal variant in
patients without arrhythmias, and in the absence of specific symptoms,
the clinical relevance is not known.
■ CATECHOLAMINERGIC POLYMORPHIC VT
This rare familial syndrome is due to mutations in the cardiac ryanodine receptor and, less commonly, the sarcoplasmic calcium binding
protein calsequestrin 2. These mutations result in abnormal sarcoplasmic calcium handling and polymorphic ventricular arrhythmias that
resemble those seen with digitalis toxicity. The VT is polymorphic or
has a characteristic alternating QRS morphology termed bidirectional
VT. Patients usually present during childhood with exercise or emotioninduced palpitations, syncope, or cardiac arrest. β-Adrenergic blockers
(e.g., nadolol and propranolol) and an ICD are usually recommended.
Verapamil, flecainide, or surgical left cardiac sympathetic denervation
reduces or prevents recurrent VT in some patients. The use of ICDs
is controversial because of the fear that an ICD shock could initiate a
TABLE 255-1 Causes of QT Prolongation and Torsades des Pointes
1. Congenital long QT syndromes
Long QT syndrome type 1: Reduced repolarizing current IKs due to mutation in
KCNQ1 gene
Long QT syndrome type 2: Reduced repolarizing current IKr due to mutation in
KCNH2 gene
Long QT syndrome type 3: Delayed inactivation of the INa due to mutations in
SCN5A gene
Others: Several other types of long QT syndromes have been described; long
QT syndrome types 1, 2, and 3 account for 80–90% of cases
2. Electrolyte abnormalities: Hypokalemia, hypomagnesemia, hypocalcemia
3. Drug-induced acquired prolongation of QT interval
Antiarrhythmic drugs
Class IA: Quinidine, disopyramide, procainamide
Class III: Sotalol, dronedarone, ranolazine, amiodarone, ibutilide, dofetilide
Antibiotics
Macrolides: Erythromycin, clarithromycin, azithromycin
Fluroquinolones: Levofloxacin, moxifloxacin
Trimethoprim-sulfamethoxazole
Clindamycin
Pentamidine
Chloroquine
Antifungals: Ketoconazole, itraconazole
Antivirals: Amantadine
Antipsychotics
Haloperidol, phenothiazines, thioridazine, trifluoperazine, sertindole,
zimelidine, ziprasidone
Tricyclic and tetracyclic antidepressants
Antihistamines (histamine 1-receptor antagonists)
Astemizole, diphenhydramine, hydroxyzine
Other drugs
Citrate (massive blood transfusions)
Cocaine
Methadone
Hydroxychloroquine
4. Cardiac conditions
Myocardial ischemia and infarction
Myocarditis
Marked bradycardia
Stress cardiomyopathy
5. Endocrine disorders
Hypothyroidism
Hyperparathyroidism
Pheochromocytoma
Hyperaldosteronism
6. Intracranial disorders
Subarachnoid hemorrhage
Thalamic hematoma
Cerebrovascular accident
Encephalitis
Head injury
7. Nutritional disorders
Anorexia nervosa
Starvation
Liquid protein diets
Gastroplasty and ileojejunal bypass
Celiac disease
1926 PART 6 Disorders of the Cardiovascular System
vicious cycle of adrenergic output and escalated ventricular arrhythmias, leading to death.
■ HYPERTROPHIC CARDIOMYOPATHY
Hypertrophic cardiomyopathy (HCM) is the most common genetic
cardiovascular disorder, occurring in 1 in 500 individuals, and is a
prominent cause of sudden death before the age of 35 years. Sudden
death can be due to polymorphic VT/VF. Rarely, sustained monomorphic VT occurs related to areas of ventricular scar, most commonly
in patients who develop an apical aneurysm. Risk factors for sudden
death in this disease include young age, nonsustained VT, failure of
blood pressure to increase during exercise, recent (within 6 months)
syncope, ventricular wall thickness >3 cm, and possibly the severity
of LV outflow obstruction. An ICD is generally indicated for high-risk
subjects, but the specific risk profile warranting an ICD continues to be
debated. Surgical myectomy, performed to relieve outflow obstruction,
has been associated with a sudden death rate of <1% per year. The
reported annual rate of sustained VT or sudden death after transcoronary ethanol septal ablation done to relieve outflow obstruction has
been reported to range between 1 and 5%.
■ GENETIC DILATED CARDIOMYOPATHIES
Genetic dilated cardiomyopathies account for 30–40% of cases of
nonischemic dilated cardiomyopathies. Some are associated with
muscular dystrophy. Autosomal dominant, recessive, X-linked, and
mitochondrial inheritance patterns are recognized. Mutations in genes
coding for structural proteins of the nuclear lamina (Lamin A/C) and
the SCN5A gene are particularly associated with conduction system
disease and ventricular arrhythmias. Patients can experience polymorphic VT and cardiac arrest or develop areas of scar causing sustained
monomorphic VT. ICDs are recommended for those who have had a
sustained VT, are at high risk due to significantly depressed ventricular
function (LV ejection fraction <35% and associated with heart failure),
or have a malignant family history of sudden death.
■ VENTRICULAR FIBRILLATION
VF is characterized by disordered electrical ventricular activation
without identifiable QRS complexes (Fig. 255-2). Spiral wave reentry
and multiple circulating reentry wavefronts are possible mechanisms.
Sustained polymorphic or monomorphic VT that degenerates to VF is
a common cause of out-of-hospital cardiac arrest. Treatment follows
ACLS guidelines with defibrillation to restore sinus rhythm. If resuscitation is successful, further evaluation is performed to identify and
treat underlying heart disease and potential causes of the arrhythmia,
including the possibility that monomorphic or polymorphic VT could
have initiated VF. If a transient reversible cause such as acute MI is not
identified, therapy to reduce the risk of sudden death with an ICD is
often warranted.
FUTURE DIRECTIONS
The role for catheter ablation in polymorphic VT and VF is rapidly
evolving, with some investigators making use of simultaneous electrical recordings from basket catheters to define critical sites for the
arrhythmia and correlating these with detailed cardiac imaging to
identify typical vulnerable sites for ablation.
Acknowledgment
Roy M. John and William G. Stevenson contributed to this chapter in
the 20th edition, and some material from that chapter has been retained
here.
■ FURTHER READING
Al-Khatib SM et al: 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of
sudden cardiac death: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice
Guidelines and the Heart Rhythm Society. Heart Rhythm 15:e73,
2018.
Callans DJ: Josephson’s Clinical Cardiac Electrophysiology: Techniques
and Interpretations, 6th ed. Philadelphia, Wolters Kluwer, 2021.
Cronin EM et al: 2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias. EP
Europace 21:1143, 2019.
Jalife J, Stevenson W (eds): Zipes and Jalife’s Cardiac Electrophysiology: From Cell to Bedside, 8th ed. Philadelphia, Elsevier, 2021.
FIGURE 255-2 Fascicular ectopy triggering ventricular fibrillation. Shown is a multilead monitor from a patient with recent inferoposterior myocardial infarction and
surgical revascularization. Purkinje fibers can often survive acute infarction due to greater cellular glycogen stores and oxygenation from the left ventricular cavity. Upon
revascularization, these now surviving but poorly coupled Purkinje fibers can trigger premature ventricular contractions and ventricular fibrillation as shown in this strip.
Electrical Storm and Incessant Ventricular Tachycardia
1927CHAPTER 256
ELECTRICAL STORM
Electrical storm or ventricular tachycardia (VT) storm refers to the
occurrence of three or more episodes of VT or ventricular fibrillation
(VF) within 24 h requiring intervention for termination. This severe
electrical instability is associated with a high mortality and requires
prompt therapeutic intervention. Electrical storms occur in 4% of
patients with a primary prevention implantable cardioverter defibrillator (ICD) but in as many as 20% of patients with a history of known
VT or resuscitated sudden death. Catheter ablation in electrical storms
can be life-saving.
INCESSANT VT
VT is designated incessant when VT continues to recur shortly after
electrical, pharmacologic, or spontaneous conversion to sinus rhythm
(Fig. 256-1). Typically, VT is monomorphic. Rarely, a slow incessant
monomorphic VT will fail detection by an ICD because it falls outside
of the programmed detection parameters. If the arrhythmia is hemodynamically stable acutely, patients can present with symptoms of
gradual cardiac decompensation. VT may become incessant due to the
proarrhythmic effect of an antiarrhythmic drug such as amiodarone or
a sodium channel blocker such as flecainide. Hemodynamic support
may be required acutely until the precipitating factors can be corrected.
Urgent catheter ablation is often warranted.
MANAGEMENT OF PATIENTS PRESENTING
WITH ICD SHOCKS
A substantial number of patients who receive an ICD can be expected
to have an arrhythmia that is terminated by the ICD, either by a shock
or antitachycardia pacing. Although this is an expected event, it can
be a sign of impending instability, deterioration of cardiac function,
or emergence of a new arrhythmia and therefore requires evaluation.
Interrogation of the ICD is crucial after a patient reports a shock or
symptoms of arrhythmia to confirm that the therapy was indeed delivered for a ventricular arrhythmia and not for lead malfunction or an
atrial arrhythmia. After a shock and in the absence of other symptoms
to suggest arrhythmia or ischemia, patients have the option of waiting
until the next working day or using remote monitoring to transmit
device interrogation data to their physician. However, occurrence of
multiple ICD shocks constitutes a medical emergency and warrants
immediate medical attention by activating the emergency medical
system. Patients should never drive to the hospital themselves after
receiving a shock from their ICD.
Spontaneous arrhythmias, particularly those that are converted
with a shock, are associated with a subsequent increased risk of death
and hospitalization in patients with depressed ventricular function.
256 Electrical Storm and
Incessant Ventricular
Tachycardia
William H. Sauer, Usha B. Tedrow
The occurrence of an arrhythmia, therefore, warrants a reevaluation
for possible decline in cardiac function, emergence of ischemia, or
intercurrent illness.
If the ICD therapy is appropriate for VT or VF, consideration is given
to whether therapy is warranted to reduce further episodes with either
antiarrhythmic drug therapy or catheter ablation. Patients who have a
rare episode of VT that is appropriately terminated and who have no
other evidence of instability may not need any additional therapy, particularly if the VT is terminated by antitachycardia pacing rather than a
shock. Shocks reduce quality of life and can lead to posttraumatic stress
disorder. In many patients, the possibility of a shock can be reduced with
appropriate ICD programming. Studies have shown that antitachycardia pacing effectively terminates >70% of VT episodes, even when VT
is very rapid. Most ICDs can be programmed to attempt overdrive pace
termination during capacitor charge. If the arrhythmia then terminates,
the shock is aborted. Appropriate programming of antitachycardia pacing is therefore critical for reducing shocks. For patients implanted with
ICDs as primary prevention, programming of VF detection zones >220
beats/min significantly reduces unnecessary and inappropriate shocks.
Long detection times will also help avoid unnecessary therapies for VT
episodes liable to terminate spontaneously.
Recurrent symptomatic episodes of VT or VF (Fig. 256-2) warrant
specific therapy with antiarrhythmic drugs or ablation as discussed
for the specific arrhythmia. The beta blockers sotalol and amiodarone
are the most common pharmacologic options. Amiodarone combined
with beta blockers is more effective than sotalol or beta blockers alone.
It is important to recognize that although VT/VF episodes may represent a deterioration of clinical status in these patients, interventions
to control the arrhythmia itself may have adverse effects on outcome.
Most antiarrhythmic drugs have the potential to induce bradycardia
to the point of requiring pacing from the ICD that, in itself, may have
deleterious effects on ventricular function. Catheter ablation is an
important option for patients with monomorphic VT.
MANAGEMENT OF THE PATIENT WITH
ELECTRICAL STORM
Patients should be adequately sedated to allay anxiety and provide pain
relief. Recurrent VT/VF is treated using standard Advanced Cardiac
Life Support guidelines; treatment includes the use of medications such
as beta blockers, amiodarone, and lidocaine with correction of any
metabolic abnormalities. Recordings from electrocardiogram (ECG)
monitoring or an implanted ICD are important to assess whether VT
is monomorphic or polymorphic. The initiation and termination of
tachycardia in the stored ICD electrograms may also suggest possible
precipitating or aggravating factors. Sedation or general anesthesia
should be considered for suppression of recurrent hemodynamically
unstable ventricular arrhythmia. Percutaneous stellate ganglion block
and upper thoracic epidural anesthesia may reduce cardiac sympathetic outflow and have been used to restore stability in some patients.
Rarely, mechanical ventricular support with extracorporeal membrane
oxygenation, percutaneous left ventricular assist device, or intra-aortic
balloon pump may be considered (Fig. 256-3).
In addition to this global strategy of stabilizing the heart rhythm,
reducing sympathetic drive, and relieving any triggering mechanisms for the management of electrical storm, there are some specific
VT Antitachycardia pacing
terminates VT Spontaneous recurrence of VT
II
FIGURE 256-1 Example of incessant monomorphic ventricular tachycardia (VT). In the initial portion of this electrocardiogram tracing, monomorphic VT is present. A train
of antitachycardia pacing (area bracketed by arrows) that is initiated at the fourth VT complex results in ventricular capture with fusion by the eighth beat and termination
of VT at cessation of pacing. The patient has underlying atrial fibrillation. Multifocal premature ventricular contractions are present. VT similar in morphology to the initial
VT restarts spontaneously toward the latter part of the trace (arrow).
1928 PART 6 Disorders of the Cardiovascular System
0.0 sec 6.0 sec
S S • S S S S S S S
6.0 sec 12.0 sec
S S • • S • S S S S
12.0 sec 18.0 sec
• SSSSSS SSSSSS
18.0 sec 24.0 sec
S S S S S S S S S S S S
24.0 sec 30.0 sec
S S • S S SS S S S S S S
120.7 sec 124.3 sec
S S S S S
113.1 sec 120.7 sec
T T T T T T T T T T T T T T T T T C S S S S
30.0 sec 36.0 sec
S S S S • S S S S S S S
36.0 sec 42.0 sec
S S S S T T T T T T T T T T T T • T T T T T T T T T T C
42.0 sec 48.0 sec
S • SSS T T T T T T TTTT T T T T T T T T T T T T T
48.0 sec 55.6 sec
T T T T • • S S S S S T T T C S S S •
55.6 sec 61.6 sec
S S S S S S S S S S S S S
61.6 sec 113.1 sec
S S S S S S S T T T T T T T T T T T T
FIGURE 256-2 Multiple implantable cardioverter defibrillator (ICD) shocks from a subcutaneous ICD. Shown is a tracing from a patient with a subcutaneous ICD with
recurrent episodes of ventricular fibrillation. The first five lines show gradually increasing amounts of ventricular ectopy and then ventricular fibrillation on the sixth line,
which is terminated by a shock (thunderbolt) on the ninth line. The sequence repeats itself, and the patient receives a second shock that successfully terminates the
arrhythmia.
Electrical Storm and Incessant Ventricular Tachycardia
1929CHAPTER 256
• Defibrillation
• Amiodarone
• Lidocaine
• Beta blockers
• Sedation and
intubation
• Anxiolytics
• Quinidine
• Ranolazine
• Procainamide
• Catheter ablation
• Overdrive pacing
• Mechanical support
(ECMO/IABP)
• Electrolyte
management
• Volume removal
• Coronary
revascularization
• Consideration of
biopsy/anti-
inflammatory
therapies
• Cardiac surgical
sympathetic
denervation
• Stellate ganglion
block (SGB)
Stabilize rhythm
Electrical storm treatments
Speed of
Deployment
Rapid
Delayed
Relieve triggers Reduce sympathetic
drive
FIGURE 265-3 Global strategy for managing electrical storm. Shown are considerations for stabilization of
electrical storm with medication strategies and procedures. ECMO, extracorporeal membrane oxygenation; IABP,
intra-aortic balloon pump.
Electrical Storm (>3 episodes of VT/VF in 24 h)
MMVT PMVT/VF
Beta blockade
Amiodarone
Lidocaine
Sedation
ECMO
SGB
Catheter ablation
Long QT Normal QT/
ischemic PVC-initiated Brugada Inflammatory
Electrolyte repletion
Magnesium
Pacing
Isoproterenol
Lidocaine
SGB
Beta blockade
Amiodarone
Lidocaine
IABP
Revascularization
Beta blockade
Amiodarone
Lidocaine
SGB
Sedation
Catheter ablation
Quinidine
Non-DHP CCB
Isoproterenol
Catheter ablation
Steroid pulse
Amiodarone
SGB
FIGURE 256-4 Management algorithm for electrical storm. Shown is a suggested strategy for managing electrical storm based on the underlying rhythm and substrate.
CCB, calcium channel blocker; DHP, dihydropyridine; ECMO, extracorporeal membrane oxygenation; IABP, intra-aortic balloon pump; MMVT, monomorphic ventricular
tachycardia; PMVT, polymorphic ventricular tachycardia; PVC, premature ventricular contraction; SGB, stellate ganglion block; VF, ventricular fibrillation; VT, ventricular
tachycardia.
therapies to be considered for patients with unique electrophysiologic
substrate (Fig. 256-4).
■ VT/VF IN THE SETTING OF MYOCARDIAL
ISCHEMIA
Ischemia should be considered especially if polymorphic VT or VF is
identified as the primary arrhythmia. If electrical storm is occurring in
the setting of an acute coronary syndrome, emergent revascularization
and alleviation of anginal symptoms should be attempted. Within the
infarcted myocardium, surviving Purkinje cells can exhibit triggered automaticity and lead to recurrent episodes of polymorphic VT/VF requiring
frequent cardioversions before and after revascularization. Catheter ablation of premature ventricular contractions (PVCs) that are observed to
repeatedly initiate the arrhythmia can be effective (Fig. 256-5).
■ PVC-INITIATED
POLYMORPHIC VT/VF
Similar to the post–myocardial infarction
electrical storm, patients without myocardial infarction or ischemia can have PVCinitiated polymorphic VT/VF storm. This
idiopathic form of VF is usually caused by
triggering PVCs originating from fascicular
tissue or papillary muscles. Often, the ventricular ectopy is from scarred myocardial tissue detected on cardiac magnetic resonance
imaging. Catheter ablation is indicated for
this condition when antiarrhythmic medication is ineffective.
■ ACQUIRED OR CONGENITAL
LONG QT SYNDROME
If QT prolongation causing torsades des
pointes (TdP) is possible, intravenous magnesium should be administered for its immediate effect on repolarization. In addition,
electrolyte repletion, especially potassium,
should be aggressively pursued. Increasing
the heart rate can sometimes normalize the
QT interval, and thus, pharmacologic or
pacing support should be considered. Isoproterenol can be used to
increase a patient’s sinus rate, but there is the possibility of increased
ectopy with high doses of isoproterenol possibly exacerbating ventricular arrhythmias. Although lidocaine can reduce the QT interval,
other antiarrhythmic agents should be avoided because of their effect
on repolarization.
■ BRUGADA SYNDROME
If the QT interval is not prolonged and a Brugada pattern of Rsr′ with
ST elevation in leads V1
or V2
is seen on resting ECG, administration
of quinidine and/or isoproterenol may abolish recurrent polymorphic
VT/VF episodes. Nondihydropyridine calcium channel blockers and
isoproterenol have also been used to reduce arrhythmic events. An
epicardial substrate-based catheter ablation over the right ventricular
1930 PART 6 Disorders of the Cardiovascular System
N V V N V V V V V V V V V V V V V V V V V V V V V V V V V V
N
T 1mV
Scale (0.0/40.0/80.0/120.0)
N V V N N V V V N V V V V V V V V V V V V V V V
FIGURE 256-5 Premature ventricular contraction (PVC)–triggered ventricular fibrillation (VF) after myocardial infarction electrical storm. Shown is a series of monitoring
strips from a patient with VF occurring in a PVC-triggered fashion after myocardial infarction. A single electrocardiogram lead and the blood pressure tracings are shown.
The triggering PVCs are indicated with red arrows. The VF results in prompt hemodynamic collapse as evidenced by the blood pressure tracing.
Section 4 Disorders of the Heart,
Muscles, Valves, and Pericardium
257 Heart Failure:
Pathophysiology and
Diagnosis
Michael M. Givertz, Mandeep R. Mehra
CLINICAL DEFINITIONS, EPIDEMIOLOGY,
AND PHENOTYPES
■ DEFINITIONS
Heart failure (HF) is a common final pathway for most chronic cardiovascular diseases including hypertension, coronary artery disease,
and valvular heart disease. The American College of Cardiology
Foundation/American Heart Association (ACCF/AHA) and Heart Failure
Society of America (HFSA) guidelines define HF as a complex clinical
syndrome that results from any structural or functional impairment of
ventricular filling or ejection of blood leading to cardinal manifestations of dyspnea, fatigue, and fluid retention. The European Society
of Cardiology’s (ESC) definition emphasizes typical symptoms (e.g.,
breathlessness, ankle swelling, and fatigue) and signs (e.g., elevated
jugular venous pressure, pulmonary crackles, and peripheral edema)
caused by a structural and/or functional cardiac abnormality, resulting in a reduced cardiac output and/or elevated intracardiac pressures
at rest or during stress. Because some patients present without signs
or symptoms of volume overload, the term heart failure is preferred
over the older term congestive heart failure. Cardiomyopathy and left
ventricular dysfunction are more general terms that describe disorders of myocardial structure and/or function, which may lead to
HF. In pathophysiologic terms, HF has been defined as a syndrome
outflow tract has been described as a strategy for drug-refractory ventricular tachyarrhythmias in Brugada syndrome.
■ INFLAMMATORY CARDIOMYOPATHY
If the patient has no known previous cardiac disease, consideration
should be given to an inflammatory myocarditis causing the frequent
ventricular arrhythmias. Giant cell myocarditis, cardiac sarcoidosis,
and certain viral myocarditis can present with VT/VF storm. An
endomyocardial biopsy should be considered to potentially identify
new-onset inflammatory cardiomyopathies that may require urgent
anti-inflammatory therapy. Once the acute episode is controlled, strategies to prevent recurrent VT or VF should be considered.
Acknowledgment
Roy M. John and William G. Stevenson contributed to this chapter in
the 20th edition, and some material from that chapter has been retained
here.
■ FURTHER READING
Al-Khatib SM et al: 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of
sudden cardiac death: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice
Guidelines and the Heart Rhythm Society. Heart Rhythm 15:e73,
2018.
Callans DJ: Josephson’s Clinical Cardiac Electrophysiology: Techniques
and Interpretations, 6th ed. Philadelphia, Wolters Kluwer, 2021.
Cronin EM et al: 2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias. EP
Europace 21:1143, 2019.
Jalife J, Stevenson W (eds): Zipes and Jalife’s Cardiac Electrophysiology: From Cell to Bedside, 8th ed. Philadelphia, Elsevier, 2021.
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