increases deep sternal wound infection. Ann Thorac Surg 2007;83:1002–1006.

44. Shroyer AL, Grover FL, Hattler B, et al. On-pump versus off-pump coronary-artery bypass surgery.

N Engl J Med 2009;361:1827–1837.

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coronary artery bypass. Circulation 2000;102:2799–2802.

46. Zhao DX, Leacche M, Balaguer JM, et al. Routine intraoperative completion angiography after

coronary artery bypass grafting and 1-stop hybrid revascularization results from a fully integrated

hybrid catheterization laboratory/operating room. J Am Coll Cardiol 2009;53:232–241.

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2007;37:944–946.

48. de Canniere D, Wimmer-Greinecker G, Cichon R, et al. Feasibility, safety, and efficacy of totally

endoscopic coronary artery bypass grafting: multicenter European experience. J Thorac Cardiovasc

Surg 2007;134:710–716.

49. Bonatti J, Schachner T, Bonaros N, et al. Robotic totally endoscopic double-vessel bypass grafting: a

further step toward closed-chest surgical treatment of multivessel coronary artery disease. Heart

Surg Forum 2007;10:E239–E242.

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following coronary artery bypass surgery. JAMA 2007;297:471–479.

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blood-component transfusion in isolated coronary artery bypass grafting. Crit Care Med

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transfusion requirements in critical care. N Engl J Med 1999;340:409–417.

56. Salamon T, Michler RE, Knott KM, et al. Off-pump coronary artery bypass grafting does not

decrease the incidence of atrial fibrillation. Ann Thorac Surg 2003;75:505–507.

57. Daoud EG, Strickberger SA, Man KC, et al. Preoperative amiodarone as prophylaxis against atrial

fibrillation after heart surgery. N Engl J Med 1997;337:1785–1791.

58. Crystal E, Connolly SJ, Sleik K, et al. Interventions on prevention of postoperative atrial fibrillation

in patients undergoing heart surgery: a meta-analysis. Circulation 2002;106:75–80.

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artery graft patency by coronary system. Ann Thorac Surg 2005;79:544–551.

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survival and other cardiac events. N Engl J Med 1986;314:1–6.

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Study. N Engl J Med 1988;319:332–337.

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1987;44:471–486.

64. Comparison of coronary bypass surgery with angioplasty in patients with multivessel disease. The

Bypass Angioplasty Revascularization Investigation (BARI) Investigators. N Engl J Med

1996;335:217–225.

65. The SoS Investigators. Coronary artery bypass surgery versus percutaneous coronary intervention

with stent implantation in patients with multivessel coronary artery disease: a randomised

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66. Booth J, Clayton T, Pepper J, et al. Randomized, controlled trial of coronary artery bypass surgery

versus percutaneous coronary intervention in patients with multivessel coronary artery disease: sixyear follow-up from the Stent or Surgery Trial (SoS). Circulation 2008;118:381–388.

67. SYNTAX Investigators. Percutaneous coronary intervention versus coronary-artery bypass grafting

for severe coronary artery disease. N Engl J Med 2009;360:961–972.

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Chapter 84

Mechanical Circulatory Support for Cardiac

Failure

Gordan Samoukovic and Francis D. Pagani

Key Points

1 The term “mechanical circulatory support” (MCS*) refers to a broad array of cardiac support devices

distinguished by the following important features: location of the pumping chamber of the device,

ventricle being supported, and pumping mechanism.

2 Indications for MCS include bridge to recovery, bridge to transplantation, and destination therapy

(permanent implantation as an alternative to transplantation).

3 The major types of devices utilized for bridge to recovery are temporary, extracorporeal systems

that can be inserted percutaneously.

4 Devices utilized for bridge to transplantation or destination therapy are durable, long-term devices

requiring major operative implantation that facilitate patient discharge from the hospital with

untethered “hands-free” mobility.

5 Delay in establishing any type of MCS results in a greater acuity and severity of illness increasing

the need for biventricular support (as opposed to just left ventricular support alone). Patients

requiring biventricular support have a decreased survival secondary to a greater degree of organ

failure present at implant.

6 Patient selection is the most important factor in determining outcome of patients who receive MCS.

7 Major adverse events following initiation of MCS are those related to anticoagulation therapy (i.e.,

bleeding and hemorrhagic stroke) necessary during MCS, infection, right-sided heart failure, and the

malfunction of the device (i.e., mechanical or electrical failure and pump thrombosis).

8 The Interagency Registry of Mechanically Assisted Circulatory Support (INTERMACS) is a National

Institutes of Health-funded data registry to study outcomes for patients with durable, long-term

implantable MCS devices.

9 Major technologic advances in device designs for temporary and long-term durable devices have

incorporated continuous-flow rotary pumps with an axial or centrifugal blood flow path.

INTRODUCTION

1 The term “mechanical circulatory support” (MCS) refers to a broad array of cardiac support devices.

These devices are distinguished by the following important features: (1) location of the pumping

chamber of the device (extracorporeal vs. intracorporeal or “implantable”; (Fig. 84-1) (2) ventricle

being supported (left ventricular assist device [LVAD] vs. right ventricular assist device [RVAD] vs.

biventricular assist device [BiVAD] vs. total artificial heart [TAH]); (Fig. 84-2) and (3) pumping

mechanism (pulsatile, volume displacement device vs. continuous-flow rotary device with axial or

centrifugal design (Fig. 84-3). Generally, the pumping chamber of short-term support devices is

extracorporeal or paracorporeal in location, while so-called “durable” long-term systems are generally

intracorporeal (implantable).

INDICATIONS FOR MCS AND DEVICE SELECTION

The spectrum of MCS therapy encompasses several indications for use and a broad range of MCS device

designs. Currently, there are three accepted indications for MCS based upon regulatory oversight by the

U.S. Food and Drug Administration (FDA), reimbursement criteria set by the Centers for Medicare &

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Medicaid Services, and historical use of MCS therapy.

2 3 “Bridge to Recovery” (BTR) refers to the use of MCS in patients who are presenting with acute

cardiogenic shock or decompensated heart failure, where the “optimal” medical therapy, including

intravenous inotropes and/or vasoconstrictors, has failed. These patients are thought to have an

expectation of myocardial recovery following a short period of temporary MCS (generally days to

weeks). The short-term utilization of MCS for BTR is the most common application of MCS in the United

States.1 Examples of reversible forms of myocardial injury include acute myocardial infarction, viral

myocarditis, or postcardiotomy cardiogenic shock with failure to separate from cardiopulmonary bypass

(CPB) following various cardiac surgical procedures. Several types of devices can provide temporary

MCS in these circumstances and include an intra-aortic balloon pump (IABP), extracorporeal ventricular

assist device (VAD), or extracorporeal membrane oxygenation (ECMO)/extracorporeal life support

(ECLS).1 Generally, temporary MCS devices are implanted percutaneously allowing for rapid initiation

of support and facilitating removal once cardiac function returns.1 Certain types of extracorporeal VAD

systems require major operative procedures with sternotomy for insertion. These types of systems are

generally utilized for postcardiotomy support where access to the mediastinum is facilitated by prior

sternotomy performed initially for the open heart operation.

4 The second indication for MCS applies to patients presenting in cardiogenic shock or decompensated

heart failure refractory to optimal medical management where myocardial function is unlikely to

recover and the patient is considered a candidate for heart transplantation. Durable MCS devices

designed for long-term support as a BTT (Bridge to Transplant) and permit untethered patient mobility

with discharge from the hospital are appropriate devices for this indication. Implantation of these types

of MCS devices requires a major operative procedure usually including CPB and is ideal for patients

who are hemodynamically stable with advanced symptoms and/or inotrope dependence in the absence

of significant end-organ dysfunction or cardiogenic shock.

Figure 84-1. Classification of mechanical circulatory support devices by location of the pumping mechanism (extracorporeal,

paracorporeal, and implantable).

The third indication for MCS applies to hemodynamically stable patients with chronic refractory

symptoms of advanced heart failure due to irreversible forms of cardiomyopathy, but who are not

eligible for heart transplantation. The application of long-term, durable MCS in this setting is termed

“destination therapy” (DT). Similar to the BTT group, DT patients require long-term, durable, and

reliable MCS devices permitting untethered “hands-free” patient mobility at home.2 Long-term, durable

MCS devices are implantable and require a major operative procedure for placement and are ideally

placed in patients with significant symptoms of advanced heart failure refractory to optimal medical

management but with stable hemodynamics. The survival, functional, and quality-of-life benefit of MCS

for DT for the treatment of chronic advanced heart failure was established in a prospective, randomized

trial known as the REMATCH Trial (Randomized Evaluation of Mechanical Assistance in the Treatment

of Congestive Heart Failure).2 This prospective, randomized trial evaluated the use of an implantable

LVAD compared with optimal medical therapy for refractory chronic advanced heart failure. LVAD

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therapy significantly reduced (relative risk, 0.52; 95% confidence limit, 0.34–0.78 at 1 year) the

mortality seen in the control population treated with optimal medical therapy at both 1-year and 2-year

follow-up. Despite serious adverse events attributable to MCS from infection, bleeding, and device

malfunction, LVAD recipients had an improved survival rate and experienced a superior quality of life

compared to the medical therapy group. Currently, patients evaluated for DT must meet the following

specific criteria: (1) New York Heart Association Class IV or American Heart Association Stage D heart

failure symptoms; (2) a left ventricular ejection fraction of <25%; (3) a peak exercise oxygen

consumption of <14 mL/kg/min (if unable to exercise be dependent on intravenous inotropes for 14

days or intra-aortic balloon pump therapy for 7 days); and (4) significant functional limitations despite

the use of maximally tolerated doses of drugs outlined in the recent guidelines for heart failure

treatment for at least 45 of the last 60 days.3

Figure 84-2. Classification of mechanical circulatory support devices by the ventricle being assisted (A: right ventricular assist, B:

biventricular assist, and C: left ventricular assist).

The intended use and indication for MCS significantly influence MCS device selection and use. The

decision to initiate MCS must be individualized and based upon the intended use, clinical setting, along

with patient variables and condition, type of MCS devices available, and FDA approval and guidelines

for use of each specific device. The paradigms of BTR, BTT, and DT have become integrated into the

MCS-treatment algorithm, currently delivered by clinicians, regulatory agencies, and insurance payers.

These paradigms do not consistently describe all clinical situations and realities of patient care and the

separation of patients into BTT and DT populations has been problematic.4 During an acute illness,

many patients may fall into a gray zone with comorbidities that prevent consideration for heart

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transplantation but may reverse over time. Thus, clinicians may not have a clear assessment of heart

transplant eligibility at the time of MCS device implant. These patients are frequently categorized as

“bridge to decision or bridge to candidacy.” In an attempt to normalize end-organ function that

currently precludes long-term heart replacement therapies, these patients are often supported using

ECMO or short-term single or BiVADs as a bridge to a durable long-term MCS device. In such cases,

even if a contraindication to heart transplant existed at the time of durable MCS device implant, this

contraindication may resolve with long-term MCS therapy and the patient may ultimately receive a

heart transplant. The category of “bridge to candidacy” is currently not recognized by regulatory

agencies but it is likely that indications for MCS will continue to evolve in the future.

TIMING OF MCS INTERVENTION

Cardiogenic Shock and Acute Heart Failure

Although established criteria for initiation of MCS do not exist and there is wide variability in clinical

practice,1 the timing of implant is paramount and directly affects outcomes. Generally, patients

presenting with acute forms of myocardial injury have recognizable hemodynamic changes – a cardiac

index of less than 2.2 L/min/m2, systolic blood pressure less than 90 mm Hg, pulmonary capillary

wedge pressure higher than 20 mm Hg, right atrial pressure higher than 18 mm Hg, and evidence of

tissue malperfusion and multi-organ dysfunction, despite optimal medical therapy. Patient history and

overall clinical setting also need to be considered in the decision to initiate MCS. When patients reach

this degree of hemodynamic compromise, the mortality risk is substantial and frequently exceeds 50%

at 30 days despite the availability of optimal medical therapy, invasive circulatory monitoring,

thrombolysis, and IABP support.5,6

Figure 84-3. Classification of mechanical circulatory support devices by intended duration of support and pumping mechanism

(pulsatile, volume displacement, or continuous-flow rotary pumps). (Impella, Abiomed Corporation, Danvers, MA; Thoratec pVAD,

HeartMate II, HeartMate III, Thoratec Corporation, Pleasanton, CA; CardioWest TAH, Syncardia Systems, Tucson, AZ; TandemHeart

pVAD, CardiacAssist Corporation, Pittsburgh, PA; CentriMag VAD, Levitronix LLC, Waltham, MA; Jarvik LVAD, Jarvik Heart

Corporation, New York, NY; HVAD LVAD, HeartWare Corporation, Miami, FL)

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Algorithm 84-1. Current algorithm for assessing patients with advanced heart failure for heart transplantation and mechanical

circulatory support. Transplant status is initially assessed to determine appropriate indication for MCS use; BTT vs. DT. (Adapted

from Mancini D, Colombo PC. J Am Coll Cardiol 2015; 65(23):2542–2555, with permission.)

5 Data from the Abiomed BVS 5000 registry demonstrated that delay in initiating temporary MCS for

more than 6 hours in the context of postcardiotomy shock or after failure to separate from CPB is

associated with a significant decrease in survival rate; 44% versus 14%.7 Delay in instituting any type of

MCS with rapid progression of multiorgan failure increases the need for biventricular support as

opposed to LVAD support alone.8–12 Similarly, an episode of cardiac arrest prior to the initiation of MCS

significantly impacts survival rate, decreasing it from 47% to only 7%.7

Chronic Heart Failure

More subtle indications to initiate MCS may be present, particularly in the group of patients suffering

from chronic advanced heart failure who are being evaluated for BTT or DT. These indications include

dyspnea at rest or with any or minimal effort and accompanied by resting tachycardia, progressive

organ dysfunction (reflected in worsening renal or hepatic parameters), limited functional capacity, and

poor quality of life despite optimal medical management with or without inotrope therapy.

Deterioration in end-organ function or progressive decline in functional performance may occur in the

absence of a significant change in hemodynamic parameters due to chronic adaptation to low cardiac

output. In addition, patients who do not tolerate optimal medical management and experience renal

insufficiency or hypotension in the setting of optimal doses of ACE inhibitors or beta blockers, as well

as those who do not tolerate inotrope therapy due to refractory ventricular arrhythmias or have lifethreatening coronary disease may benefit from MCS therapy (Algorithm 84-1).

Dependence on intravenous inotropes has traditionally been considered the threshold that prompts

consideration of MCS13–15 (Fig. 84-4). However, patients with advanced systolic heart failure are

currently eligible for DT therapy even if they are not dependent on inotropes, provided they meet

indications for DT therapy. Only 18% of durable adult LVADs are currently implanted in patients not yet

dependent on intravenous inotropes.13,14 Low implant rates in ambulatory advanced heart failure

(noninotrope dependent) may reflect reluctance of both physicians and patients.15 Ambulatory patients

with advanced heart failure should have ongoing discussions about the trade-offs of living with heart

failure in comparison with undergoing LVAD implantation to identify preferences and thresholds for

considering elective LVAD therapy. Evidence to guide LVAD use before inotrope dependence is

growing.16

PATIENT SELECTION AND INFLUENCE OF COMORBIDITIES ON

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OUTCOMES

6 Patient selection is a paramount in determining outcome in patients requiring MCS. Generally,

patients should be excluded from consideration for MCS in situations where cardiac recovery is unlikely

and/or heart transplantation and DT are not feasible. Under these circumstances, MCS support is

generally considered futile. Other relative contraindications to MCS include irreversible renal, hepatic

or respiratory failure, sepsis, or a significant cognitive deficit.

Renal Function

Renal dysfunction in context of MCS has consistently been associated with increased morbidity and

mortality rates.17,18 It is usually secondary to shock-related malperfusion and high central venous

pressures but may also be worsened by drugs frequently used for heart failure therapy. Acute renal

failure requiring renal replacement therapy is not necessarily a contraindication to short-term MCS but

may be more of an obstacle to successful long-term MCS therapy for BTT or DT. In the setting of

cardiogenic shock complicated by acute renal failure, reestablishing normal hemodynamics may

facilitate resolution of the renal failure in a relatively short period of time. Duration of cardiogenic

shock along with the patient’s baseline renal function, therefore, plays an important role predicting the

probability of recovery of renal function.

Figure 84-4. INTERMACS scale for classifying patients with advanced heart failure. Percent of implants by INTERMACS profile.

Current U.S. Food and Drug Administration (FDA) approval status and acceptance in the medical community. (Adapted from

Mancini D, Colombo PC. J Am Coll Cardiol 2015;65(23):2542–2555, with permission.)

Pulmonary Function

Cardiac failure may result in a restrictive pulmonary limitation that frequently improves as MCS aids

with removal of interstitial fluid and intrathoracic effusions. Patients with a history of smoking or

intrinsic lung disease identified by significant abnormalities on pulmonary function testing warrant

high-resolution computed tomography to characterize the lung disease and exclude thromboembolic

etiology. Echocardiography is used to rule out an intracardiac shunt. Patients with severe pulmonary

disease may have a fixed pulmonary vascular resistance (not responsive to pulmonary artery

vasodilators). High fixed pulmonary vascular resistance (generally >6 wood units) represents a

contraindication to heart transplantation and thus BTT indication. Perioperative hypoxia as a result of

significant underlying lung disease may also contribute to pulmonary vasoconstriction leading to rightsided heart failure following initiation of LVAD support. Moderate elevations in pulmonary vascular

resistance can be encountered in patients with cardiogenic shock and does not preclude the successful

use of MCS if reversibility or significant decrease in the pulmonary vascular resistance is achieved with

inotropes or pulmonary vasodilators.

Liver Function

Previous studies have reported that total bilirubin levels and hepatic cellular enzymes more than three

times normal are independent risk factors for adverse outcomes.18,19 The etiology of the

hyperbilirubinemia may be multifactorial, resulting from any combination of congestive hepatopathy,

cholestasis, primary biliary, or infectious or parenchymal disease. Abnormal liver function is often

associated with abnormal coagulation and low serum albumin. Attempts should be made to normalize

the liver function prior to initiation of durable MCS. The presence of portal hypertension with liver

cirrhosis is a contraindication to MCS. Any history of significant alcohol use should be reviewed in

potential MCS patients, especially in those showing abnormalities in routine liver function tests.

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Patients should also be tested for presence of infectious agents such as hepatitis A, B, or C or other

viruses. Liver ultrasonography is an important screening modality for patients with significant

hepatomegaly and can rule out infiltrative disease, mass or other pathology that may warrant biopsy.

Improvement in hepatic congestion and recovery of synthetic functions of the liver typically occur with

institution of MCS.

Right-Sided Heart Failure

Left ventricular dysfunction frequently leads to coexisting right-sided heart failure. Right-sided heart

failure is an important cause of mortality and morbidity following initiation of MCS and often

necessitates biventricular support.8–12,20–22 Patients with a nonischemic etiology of heart failure are

three to four times more likely to require BIVAD support. These patients tend to present with early

signs of renal, pulmonary, and hepatic dysfunction. BiVAD support is associated with lower survival

during both short- and long-term MCS. Preoperative optimization of RV function with a goal of

lowering the right atrial pressure lower than 15 mm Hg is important in reducing the need for

postoperative RV support. The higher the pulmonary wedge pressure at the time of device implantation,

the greater the benefit of LV decompression and hence, reduction in RV afterload that reduces the need

for BIVAD support. Early adverse influences of LVAD support on RV function include a reduction in LV

pressure over that of RV pressure that causes a leftward shift of the interventricular septum, causing

distention of the RV and impairing systolic function of the RV by reducing the significant septal

contribution to RV contractility.23–25

Coagulation Parameters

Coagulopathy is a common abnormality encountered in patients with refractory heart failure. An

abnormal international normalized ratio (INR) in the absence of warfarin therapy is of added concern,

as it may reflect chronically high right atrial pressures, leading to congestive hepatopathy and

eventually fibrosis and cirrhosis. Prolonged abnormal INR and low platelet count combined with the use

of anticoagulation or antiplatelet therapy are associated with significant perioperative bleeding,

requiring multiple transfusions, which frequently lead to elevation of pulmonary vascular resistance, RV

failure, hemodynamic instability, and multiorgan failure.26,27 In addition, these patients are frequently

malnourished and lack substrates for the liver’s synthetic pathways, including those of coagulation

factors, particularly factor VII. The preoperative screening for coagulation abnormalities should include

prothrombin time (PT), partial thromboplastin time, INR, platelet count, platelet aggregation studies,

and possibly a heparin-induced thrombocytopenia (HIT) assay. The presence or development of HIT is

associated with a high risk of bleeding as well as thrombosis of MCS devices.28

Nutrition

Malnutrition is an important contributor to morbidity among patients on MCS. A serum albumin lower

than 3.3 mg/dL appears to increase the mortality rate 6.6 times in the DT population of LVAD

patients.29,30 Significant nutritional deficiency is often associated with poor wound healing, an increased

risk of infection and impaired T-lymphocyte function. Patients whose body mass index is either less than

22 or more than 36 are at risk for perioperative complications. Generally, survival of MCS patients is

more adversely impacted by cachexia than obesity. Cachexia is often due to poor appetite due to

elevated tumor necrosis factor and other cytokines, limitations in exertion and work of breathing, and

early satiety in those with significant hepatomegaly. Delay in instituting MCS therapy may be

warranted for several weeks when feasible to allow improvement of the nutritional status, preferably

by enteral supplementation. Early aggressive caloric supplementation in the postoperative period is

critical in preventing malnutrition and rebuilding nutritional stores.

OTHER IMPORTANT MEDICAL CONSIDERATIONS WHEN INITIATING

MCS

Valvular Heart Disease

Abnormalities of the cardiac valves have important adverse consequences in patients considered for

MCS and may require repair or replacement in order to successfully initiate MCS and achieve weaning

from support. Mild to moderate aortic stenosis in the absence of insufficiency is not a contraindication

2424