omplex information, making them “smart” devices that are

more responsive to changing patient needs.

Pacemaker Response

There are two basic ways in which pacemakers can initiate

impulses:

Triggered: These are fixed-rate pacemakers that fire

according to a predetermined plan, regardless of

the patient’s underlying cardiac activity.

Inhibited: These pacemakers are demand pacemakers—

they fire only when needed. They are capable

of inhibiting their stimulus when they sense a

patient’s complex.

It is possible for pacemakers to be both triggered and

inhibited. That is, they ignore atrial complexes but hold back

if they sense a ventricular beat.

Electrode Placement for

Temporary Pacemaker

When a patient is unstable and the EKG indicates that an

artificial pacemaker is needed, temporary pacing can be

initiated. The most common electrode placement for temporary pacemaker placement in acute settings is via external

pacing pads. Both pads can be placed on anterior chest wall,

or one pad can go on the front chest and the other on the

back. The key point when positioning the electrodes is to

ensure that the heart is well situated between the two pads

(Figure E2).

Temporary pacing can also be achieved transvenously

by inserting a special pacing wire cannula through a large

vein like the internal jugular or subclavian. Generally, this is

done only in settings where a sterile field can be maintained

and imaging is available to guide wire placement.

EKG Analysis

The electrical impulses produced by the pacemaker appear on

the EKG tracing as unnaturally sharp spikes superimposed

on the patient’s underlying rhythm. Pacemaker spikes can

be small and difficult to detect, so EKG machines often

augment the signal to make spikes more visible.

When the pacemaker captures, it produces an EKG

wave consistent with the chamber being paced. That is, if

it’s an atrial pacemaker, the spike will be followed immediately by a P wave, but if the pacemaker is stimulating the

ventricles, the spike will be followed immediately by a wide

QRS similar to a PVC. If both chambers are paced, there will

be two spikes for each cardiac cycle. See Figures E3–E5.

Properly Functioning

Pacemakers

In Figures E3–E7, the sharp spikes produced by pacemakers

are marked with a P .

Figure E2 Pacemaker Placement

TEMPORARY

PACEMAKERS

Transvenous PERMANENT PACEMAKERS

FRONT BACK

Transcutaneous

Pacemakers 537

Figure E3 Paced Complexes

A B F

P P C D E P G

Pacemakers often supplement, rather than supplant, the patient’s own rhythm. This rhythm strip shows a ventricular

demand pacemaker that fires occasionally to supplement the patient’s underlying atrial fibrillation.

The narrow complexes (C, D, E, and G) are the patient’s normally conducted beats.

The wider complexes (A, B, and F) are pacemaker-initiated (note spikes preceding each QRS).

Figure E4 Pacemaker Rhythms

P P P P P P

P

P

P

P

P

P

P

P

P

P

P

P

P

P

(a)

(b)

A properly functioning pacemaker will show a sharp spike, followed immediately by depolarization of the chamber it is

intended to pace. (a) Ventricular Pacemaker: This rhythm strip shows ventricular pacemaker capturing every beat. Note

absence of mappable P waves and sharp spikes followed immediately by wide QRS complexes. (b) AV Synchronous

Pacemaker: This rhythm strip shows an AV synchronous pacemaker capturing every beat. Note pacemaker spikes

preceding both atrial and ventricular depolarization.

538 Appendix E

Figure E5 Properly Functioning Ventricular Demand Pacemaker

P P P P

This pacemaker is set to fire whenever the patient’s intrinsic rate falls below 60 bpm. The first three complexes show

the patient’s heart depolarizing at about 68 bpm, so the pacemaker inhibited itself. It kicked in at the fourth complex

when the rate dropped and continued to pace at a rate of 60 bpm.

Figure E6 Failure to Capture/Failure to Sense

P P P P P

The underlying rhythm is atrial fibrillation, and the ventricular pacemaker is set at an unusually slow rate of 44 bpm. It

fails to sense the patient’s own complexes and continues to fire regularly, regardless of underlying ventricular activity.

When the pacemaker stimulus finds the ventricles refractory, it fails to capture.

Pacemaker Malfunction

Today’s pacemakers are generally reliable, but they still

experience occasional problems. Some of the more common

malfunctions are listed below.

Failure to Capture: Occasionally, a pacemaker fires

normally but no capture occurs; this is called a

non-capturing pacemaker. This is seen on the

EKG as pacemaker spikes that are not followed

by depolarization complexes.

Competition: If a demand pacemaker fails to sense

an underlying rhythm, it can fire in complete

disregard to the patient’s own rhythm, thereby

competing for control of the heart. Competition

can also occur if the heart’s intrinsic pacemaker

fires in a patient with a fixed-rate pacemaker, thus

allowing competition between the two pacemakers.

In either case, there is danger that the pacemaker

spike can fall during the heart’s relative refractory

period (downslope of the T wave) and instigate a

rapid, repetitive rhythm such as VT or VF.

Less common pacemaker problems include:

Runaway Pacemaker: This occurs when the pacemaker

fires too rapidly but still captures, causing the heart

to respond in a tachycardia. The problem is usually

caused by a malfunctioning impulse generator.

Battery Failure: As with all battery-operated products,

the pacemaker is useless when the battery fails.

This would appear on the EKG as the complete

absence of pacemaker spikes in a rhythm that

would normally be paced.

Pacemakers 539

Figure E7 Competition

P P P P P P P P P P

This strip shows pacemaker spikes at a rate of 100 bpm, with an underlying ventricular tachycardia/fibrillation. The

pacemaker is competing for control of the heart, but the irritable ventricular foci are winning.

Patient Assessment

Assessment must begin with the patient. Check pulses and

other perfusion parameters. Remember that the EKG can’t

tell you whether or not the heart is actually pumping blood

in response to the pacemaker’s stimuli.

Next, determine whether the pacemaker is doing what it

was intended to do. By establishing the relationship between

pacemaker spikes and the patient’s complexes, you should

be able to answer the following questions:

1. Does each spike capture?

2. Is the rate reasonable?

3. Are spikes competing with the patient’s rhythm?

4. Are spikes falling near T waves?

5. Is the pacemaker functioning consistently and reliably?

Patient Management

Pacemakers are themselves a treatment; hence, it is a mistake

to try to “treat” a malfunctioning pacemaker. When pacemakers malfunction, treatment is directed at the patient and

the underlying rhythm. See Figures E8–E19.

Sample Pacemaker Rhythm Strips

Figure E8 Fully Functional Atrial Pacemaker Showing 100% Capture

540 Appendix E

Figure E9 Ventricular Pacemaker Showing 100% Capture (with Underlying Complete Heart Block)

Figure E10 AV Sequential (DVI) Pacemaker

Figure E11 Properly Functioning Demand Pacemaker

Pacemakers 541

Figure E12 DDD Pacemaker in AV Sequential Mode

Figure E13 Sinus Rate Accelerates and Regains Control from Ventricular Demand Pacemaker

Figure E14 Pacemaker Fails to Depolarize Consistently, Indicating Lead Fracture or Displacement

542 Appendix E

Figure E15 Ventricular Pacemaker (with Underlying Complete Heart Block) with 100% Capture

Figure E16 Atrial Pacemaker with 100% Capture

Figure E17 Non-Capturing Pacemaker Competing with Supraventricular Rhythm in First Part of Strip,

Converting to Ventricular Tachycardia Competing with Pacemaker at End of Strip

Pacemakers 543

Figure E18 Ventricular Demand Pacemaker (with Underlying Atrial Fibrillation)

Figure E19 Ventricular Pacemaker Showing 100% Capture

544

ACLS: Advanced cardiac life support.

AF: Atrial Flutter.

Af: Atrial Fibrillation.

Atrial Kick: The final push during the last stage of atrial

contraction, during which blood flow increases as the

atrium empties. Loss of atrial kick can reduce cardiac

output by 20–30%.

AMI: Acute myocardial infarction.

ANS: Autonomic nervous system.

Anterior MI: Infarction of the anterior wall of the heart,

most often caused by occlusion of the Left Anterior

Descending coronary artery.

Anterior Surface: The plane of the heart that faces forward,

abutting the chest wall.

Anterobasal MI: Anterior wall infarction localized to the

base (top) of the heart.

Anterolateral MI: Anterior wall infarction localized to the

area of the lateral wall.

Anteroseptal MI: Anterior wall infarction localized to the

area of the septum.

Aorta: Artery that carries oxygenated blood from the left

ventricle to distal parts of the body.

Aortic Valve: The valve that controls passage of blood from

the left ventricle to the aorta.

Apex: The lower point of the heart.

Apical MI: Infarction localized to the apex (bottom) of the

heart.

Arrhythmia: The graphic representation of the heart’s

electrical activity; the term is loosely used to mean an

abnormality of the heart’s electrical function, but it is

also used to categorize patterns of electrical activity, not

all of which are necessarily abnormal or bad; also called

dysrhythmia; it can also be used to mean that a rhythm is not

regular.

Artifact: Electrical activity displayed on graph paper

that is superimposed on cardiac tracings, interfering with

interpretation of the rhythm; can be caused by outside

electrical sources, muscle tremors, patient movement; also

called interference.

Asystole: The absence of any cardiac electrical activity;

appears as a straight line on graph paper.

AT: Atrial Tachycardia.

Atria: The upper two chambers of the heart.

Atrial Arrhythmia: A cardiac arrhythmia originating from

the conduction system within the atria.

Atrial Fibrillation (Af): The cardiac arrhythmia in which

the atria are controlled by numerous irritable foci, thereby

causing ineffectual, chaotic atrial activity and irregular

ventricular response.

Atrial Flutter (AF): The cardiac arrhythmia in which an irritable focus in the atria produces a rapid, repetitive discharge,

resulting in rhythmic atrial depolarizations at a rate of

250–350 bpm, some of which are usually blocked by the AV

node to keep the ventricular rate in a more normal range.

Atrial Hypertrophy: Enlargement of myocardial wall in one

or more of the atria.

Atrial Kick: The increased pressure of atrial contraction

immediately before ventricular contraction; this “priming”

force increases ventricular efficiency, and can account for up

to 30% of cardiac output.

Atrial Pacemaker: An electrical stimulus originating in

the atria that paces the heart; an artificial pacemaker that

stimulates only the atria.

Atrial Tachycardia (AT): The cardiac arrhythmia in which

a single irritable focus in the atria takes over control of the

heart to produce a rate of 150–250 bpm; this arrhythmia

is often paroxysmal in nature—that is, it starts and stops

suddenly; in that instance it is called Paroxysmal Atrial

Tachycardia (PAT).

Atrioventricular Dissociation: A conduction defect that

causes the atria and ventricles to depolarize and function

independently; AV Dissociation.

Augmented Leads: Unipolar leads that measure electrical

flow on the frontal plane from the center of the heart to each

of three limb electrodes: Leads aVR, aVL, and aVF.

Automaticity: The unique ability of cardiac pacemaker cells

to initiate spontaneous excitation impulses.

Autonomic Nervous System: The system responsible for

control of involuntary bodily functions, including cardiac

and vascular activity; branches are sympathetic nervous

system and parasympathetic nervous system.

AV: Atrioventricular.

aVF: Augmented voltage, foot (left leg).

AV Heart Block: Arrhythmias caused by disturbances in

conduction through the AV node.

AV Junction: That part of the cardiac conduction system

that connects the atria and the ventricles; contains the AV

node and the non branching part of the Bundle of His.

aVL: Augmented voltage, left.

AV Node: A part of the cardiac conduction system located

within the AV junction; does not contain pacemaking cells;

its purpose is to slow conduction of impulses through the

AV junction.

aVR: Augmented voltage, right.

AV Sequential Pacemaker: A type of artificial pacemaker

that senses ventricular activity and, in its absence, paces

atria and ventricles in a normal sequence.

AV Synchronous Pacemaker: A type of artificial pacemaker

that senses both atria and ventricles and paces the ventricles

when a spontaneous P wave is not followed by a QRS.

Glossary

Glossary 545

The ventricles are depolarized in synchrony with P waves so

that atrial and ventricular contractions are coordinated.

Axis: Sum direction of electrical flow through the heart.

The axis of a given lead is the lead axis. The sum direction

of electrical flow through the heart as a whole is the mean

QRS axis.

Axis Deviation: Shift in mean QRS axis reflecting

myocardial damage, enlargement, or conduction defect.

Base: The upper end of the heart.

Baseline: The isoelectric line; the line on EKG graph paper

that indicates lack of electrical activity and from which all

other cardiac wave impulses deviate.

BBB: Bundle branch block.

Bigeminy: A pattern of cardiac electrical activity in which

every other beat is an ectopic, usually a PVC.

Biological Death: The second phase of death, following

clinical death; defined by brain death, usually following

4–6 minutes of cardiac arrest if no resuscitation is instituted.

Biphasic: A single EKG wave that has two deflections, one

upright and the other inverted.

Bipolar Lead: A lead composed of one positive and one

negative electrode.

Block: A defect in conduction within the heart’s electrical

system.

Bolus: A single loading dose of a drug; used to achieve a

rapid high therapeutic blood level prior to instituting IV drip

therapy.

bpm: Beats per minute.

Bradyarrhythmia: Any cardiac arrhythmia with a rate below

60 bpm.

Bradycardia: A heart rate less than 60 bpm.

Bundle Branches: The portion of the cardiac conduction

system within the ventricles that conducts impulses from the

Bundle of His to the Purkinje fibers; consists of right and left

bundle branches.

Bundle Branch Block (BBB): A conduction disturbance that

prevents or delays passage of impulses from the Bundle of

His through to the Purkinje network; can involve the right or

left bundle branch or, less frequently, both.

Bundle of His: That part of the cardiac conduction system

that conducts impulses from the AV Junction through to the

bundle branches.

Ca: Calcium.

CAD: Coronary artery disease.

Calibration: The act of standardizing the graphic display of

electrical activity; the calibration mark should measure

1 millivolt on the graph paper.

Capture: The heart responding to an electrical stimulus with

depolarization; generally refers to an arrhythmia’s response

to an artificial pacemaker.

Cardiac Arrest: The cessation of cardiac function, resulting

in sudden drop in perfusion and resultant clinical death.

Cardiac Cycle: The interval from the beginning of one

heartbeat to the beginning of the next; on the EKG it

encompasses the PQRST complex.

Cardiac Output (CO): The amount of blood pumped by the

left ventricle in one minute; it is calculated by multiplying

the stroke volume by the heart rate and is measured in liters

per minute.

Cardioversion: A maneuver used to convert various

tachyarrhythmias to more viable rhythms; consists of

application of electrical countershock (DC current) to the

chest wall; the electrical discharge is usually synchronized

to fall on the R wave, thus avoiding the relative refractory

period.

Carotid Sinus Massage: A maneuver used to convert

various supraventricular tachycardias to a more viable

rhythm; consists of gentle massage with fingertips over the

carotid sinus in the neck.

Central Terminal: An electrically neutral reference point

created by combining two or more electrodes. It is used to

oppose the positive electrode in unipolar leads.

CHB: Complete Heart Block.

CHF: Congestive Heart Failure.

Chordae Tendineae: Specialized fibers that connect heart

valve leaflets to papillary muscles to prevent backflow

during contractions.

Classical Second-Degree Heart Block: The term formerly

used to describe the type of AV heart block that is now called

Type II Second-Degree Heart Block, in which the AV node

intermittently blocks sinus impulses, preventing them from

being conducted through to the ventricles.

Clinical Death: The absence of pulse and blood pressure;

occurs immediately following cardiac arrest.

CO: Cardiac output.

Compensatory Pause: The time lag following an ectopic beat

before the next normal beat occurs; is identified by measuring

the interval from the R wave immediately preceding the

ectopic to the R wave immediately following it; a fully

compensatory pause (such as occurs following most PVCs)

will be exactly two times the normal R–R interval.

Competition: Condition in which an artificial pacemaker

competes with the patient’s intrinsic pacemaker for control

of the heart.

Complete Heart Block (CHB): Third-Degree AV Block; a

form of AV dissociation.

Conduction Ratio: The number of P waves to QRS

complexes. One P wave for every QRS complex is a 1:1

conduction ratio. Three P waves for every QRS complex

would be a 3:1 conduction ratio.

Conduction System: The pathways of conductive tissues

within the heart that facilitate passage of electrical impulses

throughout the myocardium.

Conductivity: The property of some cardiac cells that

enables them to transmit electrical impulses.

Contractility: The ability of heart muscle to contract in

response to electrical stimulation.

Conventional 12-Lead EKG: Electrocardiogram that

provides images of cardiac electrical activity from 12

perspectives simultaneously.

Coronary Arteries: Those blood vessels that supply the

heart muscle itself. The major branches are the Left Coronary

546 Glossary

Artery (with the Left Anterior Descending branches and the

Circumflex branch) and the Right Coronary Artery.

Coronary Sinus: The reentry point within the right atrium

where deoxygenated blood returns after having supplied the

heart muscle itself.

CPR: Cardiopulmonary resuscitation.

CT: Central terminal.

DDD: Double paced, double sensed, double response

(optimal pacemaker).

Defibrillation: Application of electrical countershock

(DC current) to the chest wall to terminate ventricular

tachyarrhythmias.

Demand Pacemaker: Pacemaker that senses patient’s

intrinsic complexes and fires only when needed.

Depolarization: The electrical process of discharging

polarized cells, usually resulting in muscle contraction.

Diaphragmatic Surface: The plane of the heart that faces

downward, resting against the diaphragm.

Diastole: The phase of the cardiac cycle in which chambers

are relaxing.

Digitalis Toxicity: Excessive blood levels of the heart drug

digitalis; also called dig-toxicity.

Dissociation: Independent function of two parts, generally

the atria and ventricles.

Dual-Chamber Pacemaker: Paces both atria and ventricles.

DVI: Double paced, ventricle sensed, inhibited response (AV

sequential pacemaker).

Dysrhythmia: Arrhythmia.

ECG: Electrocardiogram; see EKG.

Ectopic: Originating from a focus other than the primary

pacemaker.

Einthoven’s Triangle: The triangle created by an imaginary

line connecting the three chest electrodes used to create the

standard limb leads.

EKG: Electrocardiogram; electrocardiograph.

Electrocardiogram (EKG; ECG): Graphic representation of

the electrical activity in the heart.

Electrode: Metal wire attached to the patient’s body for the

purpose of conveying electrical impulses to a machine for

recording or displaying.

EMD: Electromechanical dissociation.

Endocardium: The inner layer of the heart wall, which

contains the branches of the heart’s electrical system.

Epicardium: The outside layer of the heart wall, which

contains the coronary blood vessels and nerves.

Equiphasic: A single EKG wave that has two deflections of

equal magnitude, one upright and the other inverted.

ERAD: Extreme right axis deviation.

Escape: The mechanism that allows a lower pacemaker

site to assume pacemaking responsibilities when a higher

site fails.

Evolving Infarction: The changing EKG picture associated

with the passage of time following myocardial infarction.

Failure to Capture: Situation in which the pacemaker fires

but the patient’s heart does not respond with depolarization.

Fibrillation: Chaotic, ineffective movement of the heart muscle.

First-Degree Heart Block: A type of AV heart block

characterized by prolonged but consistent conduction of

atrial impulses through to the ventricles.

Fixed-Rate Pacemaker: Pacemaker that is set at a

predetermined rate and fires regardless of the patient’s

underlying rhythm.

Flutter: Rhythmic, rapid beating of the heart muscle.

F waves: Flutter waves.

f waves: Fibrillatory waves.

Gallop Rhythms: Heart sounds that are grouped together so

they sound like galloping horses.

Heart Block: AV heart block.

Heart Rate (HR): The number of heart beats per minute.

Heart Sounds: Sounds associated with flow of blood

through heart chambers and closing of heart valves. The four

components are S1: closure of mitral and tricuspid valves;

S2: closure of aortic and pulmonic valves; S3: abnormally

rapid ventricular filling; S4: abnormally forceful atrial

contraction.

His–Purkinje System: The lower part of the cardiac

conduction system that transmits impulses throughout

the ventricles; located in the interventricular septum and

ventricular walls.

HR: Heart rate.

Hyperkalemia: High blood potassium level.

Hypertrophy: Enlargement of myocardial wall in one or

more of the chambers of the heart.

Hypokalemia: Low blood potassium level.

IAS: Interatrial septum.

Idioventricular Rhythm: A ventricular escape rhythm;

characterized by a rate less than 40 bpm.

Impulse Formation: The process by which cardiac electrical

cells create an electrical impulse without stimulation from

another source. See Automaticity.

Inferior MI: Infarction of the inferior wall of the heart, most

often caused by occlusion of the right coronary artery.

Inferior Vena Cava (IVC): Vein that carries deoxygenated

blood from the lower body back to the right atrium.

Interference: See Artifact.

Interpolation: The placement of an ectopic (especially PVCs)

between two normal beats without disturbing the regularity

of the underlying rhythm.

Interval: Distance between two points on an EKG tracing.

Interventricular Septum (IVS): The muscular wall dividing

the right and left ventricles.

Intraatrial Pathways: Branches of the cardiac conduction

system that service the atria.

Intraventricular Conduction Defect (IVCD): Disturbance

in conduction involving one or more of the bundle branches.

Also called Bundle Branch Block.

Glossary 547

Intrinsicoid Deflection: Reflection of the time it takes for peak

voltage to develop within the ventricles; measured from the onset

of the QRS to the peak of the R wave; a prolonged intrinsicoid

deflection (> 0.06 sec) is considered a “late R wave.”

Ischemic Changes: Changes on the EKG that reflect

myocardial ischemia: ST elevation, ST depression, Q wave

deepening, and T wave inversion.

Isoelectric Line: The line created on EKG graph paper when

no electrical current is flowing; see also Baseline.

IV: Intravenous.

IVC: Inferior vena cava.

IVCD: Intraventricular conduction defect.

IVS: Interventricular septum.

J Point: The demarcation between the end of the QRS

complex and the beginning of the ST segment.

JT: Junctional Tachycardia.

Junction: See AV Junction.

Junctional Escape Rhythm: An arrhythmia resulting from

failure of a higher pacemaker site, allowing the AV junction

to pace the heart at a bradycardia rate.

Junctional Tachycardia (JT): A rapid arrhythmia originating

in the AV junction.

K: Potassium.

LA: Left atrium; left arm.

LAD: Left axis deviation; left anterior descending branch of

the left coronary artery.

LAE: Left atrial enlargement.

Lateral MI: Infarction of the lateral wall of the heart, most

often caused by occlusion of the Left Anterior Descending

coronary artery.

Lateral Surface: The plane of the heart that faces the side,

just above the diaphragmatic surface.

LBB: Left bundle branch.

LBBB: Left bundle branch block.

LCA: Left coronary artery.

Lead: An electrocardiographic view of the heart, gained

by recording the electrical activity between two or more

electrodes.

LV: Left ventricle.

LVE: Left ventricular enlargement.

MCL1: Modified Chest Left; a monitoring lead that mimics

V1 and is useful in differentiating tachycardias.

MI: Myocardial Infarction.

Millivolts (mV): A measure of electricity; 1 volt equals

1,000 millivolts.

Mitral Valve: The valve that controls passage of blood from

the left atrium to the left ventricle.

mm: Millimeter.

Monitor: The machine on which electrocardiographic

impulses are displayed; oscilloscope.

Monitoring Lead: A lead that clearly shows individual wave

forms and is useful for monitoring cardiac rhythm, most

often Lead II or MCL1.

Multifocal: Term used to describe ectopic beats that

originate from more than one irritable focus. Also called

Multiformed.

Murmurs: Heart sounds caused by abnormal turbulence

associated with high flow rates, damaged valves, dilated

chambers, or backward flow.

mV: Millivolt.

Myocardial Infarction (MI): Tissue death caused by lack of

oxygen to the myocardium.

Myocardial Injury: Heart tissue damage caused by

sustained lack of oxygen.

Myocardial Ischemia: Initial heart tissue response to lack of

oxygen.

Myocardium: The center layer of the heart wall, consisting

of cardiac muscle fibers.

Na: Sodium.

Noise: Electrical interference displayed on graph paper that

interferes with interpretation of the underlying arrhythmia;

see Artifact.

Non-Q Infarction: Myocardial infarction that fails to

produce classic Q wave changes, most often because

the infarcted area is limited to partial thickness of the

myocardium; subendocardial infarction.

Normal Sinus Rhythm (NSR): The usual cardiac electrical

pattern of healthy people.

NSR: Normal Sinus Rhythm.

Oscilloscope: Display device with a screen for viewing EKG

and other physiological information; monitor.

PAC: Premature Atrial Complex.

Pacemaker: The source of electrical stimulation for cardiac

rhythm.

Pacemaker, Artificial: A device used to provided artificial

electrical stimuli to myocardial tissue to cause myocardial

depolarization.

Pacemaker Electrode: The conducting wire that connects to

the myocardium to deliver the pacemaker stimulus.

Pacemaker Site: The site of origin of the electrical

stimulation that is causing the cardiac rhythm.

Palpitations: The feeling the patient senses when the heart is

beating abnormally.

Papillary Muscles: Specialized muscles in the ventricles that

attach to heart valves by way of chordae tendineae, enabling

the valves to open and close.

Parasympathetic Nervous System: A branch of the

autonomic nervous system involved in control of

involuntary bodily functions; depresses cardiac activity

in opposition to the sympathetic branch of the ANS;

effects include slowing of heart rate and conduction and

diminished myocardial irritability.

Paroxysmal: Sudden onset and cessation; often used to

describe Atrial Tachycardia if it is characterized by abrupt

onset and termination.

Paroxysmal Atrial Tachycardia (PAT): The term used to

describe an Atrial Tachycardia characterized by abrupt onset

and cessation.

548 Glossary

PAT: Paroxysmal Atrial Tachycardia.

PEA: Pulseless Electrical Activity. A condition in which the

EKG shows a viable rhythm, but no pulse is detectible in the

patient. The electrical activity in the heart is not producing a

mechanical response (pulse).

Pericarditis: Inflammation of the pericardial sac

surrounding the heart. Causes ischemic changes on EKG and

can thus be misinterpreted to be MI.

Pericardium: A thin layer of tissue that forms the pericardial

sac to encase the heart in lubricating fluid.

Permanent Pacemaker: Pacemaker that is surgically

implanted within the patient’s body for an extended time.

PJC: Premature Junctional Complex.

Posterior Surface: The plane of the heart that faces

backward, abutting the spine.

PQRST: A single cardiac cycle on the EKG graph paper;

includes the P wave, QRS complex, and T wave and any

segments and intervals between.

Precordial Leads: Leads that measure electrical flow on the

horizontal plane, from the center of the heart to locations

around the anterior and lateral chest walls. The V leads: V1,

V2, V3, V4, V5, and V6.

Premature Atrial Complex (PAC): An ectopic beat

originating from an irritable focus in the atria.

Premature Junctional Complex (PJC): An ectopic beat

originating from an irritable focus in the AV Junction.

Premature Ventricular Complex (PVC): An ectopic beat

originating from an irritable focus in the ventricles.

PR Interval (PRI): The time interval on EKG graph paper

measured from the beginning of the P wave to the beginning

of the R wave; includes both the P wave and the PR segment;

indicates time of atrial depolarization.

PRI: P–R interval.

PR Segment: The time interval on EKG graph paper

measured from the end of the P wave to the beginning of the

R wave; indicates delay in the AV node.

Pulmonary Artery: Artery that carries deoxygenated blood

from the right ventricle to the lungs.

Pulmonary Vein: Vein that carries oxygenated blood from

the lungs back to the left atrium.

Pulmonic Valve: The valve that controls passage of blood

from the right ventricle to the pulmonary artery.

Pulse Deficit: The situation in which the heart is contracting,

but not all of the pulsations are reaching the periphery; the

difference between heart beats heard with a stethoscope and

the pulse rate measured at the periphery.

Pulseless Electrical Activity: A condition in which the EKG

shows a viable rhythm, but no pulse is detectible in the

patient. The electrical activity in the heart is not producing a

mechanical response (pulse).

Pulse Generator: The power source (battery unit) that drives

an artificial pacemaker.

Pump (Sodium): See Sodium Pump.

Purkinje System: The part of the cardiac conduction system

that transmits impulses from the bundle branches to the

myocardial cells in the ventricles; consists of Purkinje fibers

and terminal branches.

PVC: Premature Ventricular Complex.

P Wave: The first wave form in the normal cardiac cycle;

indicates atrial depolarization.

QRS Complex: The wave form on an EKG that represents

ventricular depolarization; includes the Q, R, and

S waves.

QT Interval: The time interval from the beginning of the

QRS complex to the end of the T wave; varies with

heart rate.

Quadrigeminy: A cardiac rhythm in which ectopics replace

every fourth normal beat, resulting in a cycle of three normal

beats and one ectopic, repeated continuously.

Q Wave: The first negative deflection following the P wave,

but before the R wave.

RA: Right atrium; right arm.

RAD: Right axis deviation.

RAE: Right atrial enlargement.

RBB: Right bundle branch.

RBBB: Right bundle branch block.

RCA: Right coronary artery.

Reciprocal Changes: EKG deflections seen in leads that

are opposite of each other and thus are mirror images.

For example, ST elevation in a facing lead would be ST

depression in an opposite lead. Reciprocal changes in

anterior leads are used to locate posterior infarctions.

Refractory: The state wherein the electrical cells are unable

to respond to electrical stimulation because they have not yet

recovered from the previous discharge.

Refractory Period: That portion of the cardiac cycle in

which the heart is unable to respond to electrical stimulation

because it has not yet recovered from the preceding

depolarization; consists of the Absolute Refractory Period

(QRS complex and upslope of the T wave) and the Relative

Refractory Period (downslope of the T wave).

Relative Refractory Period: The terminal portion of the

cardiac refractory period, during which a strong enough

electrical stimulus could discharge the heart, resulting in

inefficient and potentially dangerous arrhythmias; located

on the downslope of the T wave.

Repolarization: The process of recharging depolarized cells

back to their “ready” (polarized) state.

Retrograde Conduction: Electrical current that arises from

the area of the AV junction and travels backward up toward

the SA node to depolarize the atria in the opposite direction

of normal.

Rhythm: The regularity of a cardiac pattern; generally used

to refer to the arrhythmia itself, rather than its rhythmicity

(i.e., “The patient’s rhythm is Atrial Fibrillation”), even

though Atrial Fibrillation is an irregular arrhythmia;

synonymous with arrhythmia.

“R on T” Phenomenon: The situation in which the R wave of

a PVC occurs on or near the downslope of the preceding

T wave, thereby falling in the vulnerable phase of the cardiac

cycle, the Relative Refractory Period, and threatening to cause

Glossary 549

premature discharge and result in an ineffective pattern, such

as Ventricular Tachycardia or Ventricular Fibrillation.

Runaway Pacemaker: A malfunction of an artificial

pacemaker that causes it to fire at an excessive rate.

RV: Right ventricle.

RVE: Right ventricular enlargement.

R Wave: The first upright deflection following the P wave, or

the first positive wave of the QRS complex.

S/S: Signs/symptoms.

SA: Sino-atrial.

SA: Sinus Arrhythmia.

SB: Sinus Bradycardia.

sec: Second.

Second-Degree Heart Block, Type I: A type of SecondDegree Heart Block in which sinus impulses are delayed at

the AV node for increasingly long periods, until conduction

is blocked completely, then the cycle repeats itself;

Wenckebach. (Formerly called Mobitz Type I.)

Second-Degree Heart Block, Type II: A type of SecondDegree Heart Block in which the AV node selectively

blocks some beats while allowing others to pass through

to the ventricles. The EKG shows more P waves than

QRS complexes; some P waves are not followed by QRS

complexes. (Formerly called Classical Second-Degree Heart

Block, or Mobitz Type II.)

Septum: The wall that divides the heart into right and left

sides. The thin wall between the atria is called the interatrial

septum. The thicker wall between the ventricles is the

interventricular septum.

Single-Chamber Pacemaker: Paces only the atria or the

ventricles, but not both.

Sinus Arrhythmia (SA): The arrhythmia in which the

pacemaker is located in the SA node but discharges

irregularly; usually correlated with respirations; rate

increases on inspiration, and decreases on expiration.

Sinus Bradycardia (SB): The arrhythmia in which the

pacemaker is located in the SA node but discharges at a rate

less than 60 bpm.

Sinus Node: The normal pacemaker of the heart; located at

the junction of the superior vena cava and the right atrium;

SA node; sinoatrial node.

Sinus Rhythm: Any rhythm that originates in the sinus (SA)

node; used loosely to refer to Normal Sinus Rhythm.

Sinus Tachycardia (ST): The arrhythmia in which the

pacemaker is located in the SA node but discharges at a rate

greater than 100 bpm.

Sodium Pump: The chemical phenomenon that takes place

at a cellular level within the cardiac electrical conduction

system, in which sodium and potassium trade places across

the cell wall, thereby initiating the flow of electrical current

within the heart.

Standardization: The act of calibrating the EKG machine or

oscilloscope to a standard (1 millivolt).

Standard Limb Leads: The bipolar leads showing the frontal

plane: Leads I, II, and III.

Stroke Volume: The amount of blood ejected with each

contraction of the left ventricle.

ST: Sinus Tachycardia.

STEMI: ST Elevation Myocardial Infarction.

ST Segment: The portion of the cardiac cycle between the S

wave and the T wave.

Subendocardial Infarction: Infarcted area too small to

extend all the way through the ventricular wall; also called

a less-than-transmural infarction, or non-Q infarction, since

the damage is often insufficient to create the classic Q wave

changes seen with larger infarctions.

Superior Vena Cava (SVC): Vein that carries deoxygenated

blood from the upper body back to the right atrium.

Supraventricular (SV): Originating above the ventricles.

Supraventricular Tachycardia (SVT): Term used to describe

a rapid arrhythmia that is regular, has no visible P waves,

and has a rate range common to other arrhythmias, thereby

making more accurate identification impossible; commonly

applied to Atrial Tachycardia, Junctional Tachycardia, Sinus

Tachycardia, and Atrial Flutter with 1:1 response; loosely

used to refer to any tachycardia that originated above the

ventricles.

SV: Supraventricular.

SVC: Superior vena cava.

SVT: Supraventricular tachycardia.

S Wave: The second negative deflection following the P

wave, or the first negative deflection following the R wave.

Sympathetic Nervous System: One of the two main

branches of the autonomic nervous system, which controls

involuntary bodily functions; stimulates cardiac activity

in opposition to the parasympathetic branch; effects

include increased heart rate and conduction and increased

myocardial irritability.

Systole: The phase of the cardiac cycle in which the

chambers are contracting.

Tachyarrhythmia: Any cardiac arrhythmia with a

ventricular rate greater than 100 bpm.

Tachycardia: Heart rate greater than 100 bpm.

Temporary Pacemaker: An artificial pacemaker used in

acute setting to stabilize and maintain patient for short

periods.

Third-Degree Heart Block: The arrhythmia in which all

atrial impulses are prevented from reaching the ventricles

because of a complete block at the AV node; constitutes a

form of AV dissociation because atria and ventricles function

totally independent of each other; Complete Heart Block

(CHB).

Transcutaneous Pacemaker: Pacemaker stimulus delivered

across the skin via external pads.

Transmural Infarction: Infarcted area large enough to

extend completely through the wall of the ventricle.

Transvenous Pacemaker: Pacemaker wire inserted through

a vein.

Tricuspid Valve: The valve that controls passage of blood

from the right atrium to the right ventricle.

550 Glossary

Trigeminy: A pattern in which ectopics occur every third

beat, producing a repetitive cycle of two normal beats and

one ectopic.

Unifocal: Refers to ectopic beats that originate from a single

irritable focus. Also called Uniformed.

Uniphasic: A single EKG wave that has only one phase,

either upright or inverted.

Unipolar Lead: A lead that has only one charged electrode

(positive electrode). The opposing pole is created by

combining other electrodes into an electrically neutral

reference point (the central terminal).

U Wave: Low-voltage wave following the T wave, having

the same polarity as the T wave. Usually not apparent but

becomes more pronounced in hypokalemia.

Variable Conduction: A changing conduction ratio within

a given strip. For example, rather than having a consistent

ratio of 2 Ps for every QRS complex (a 2:1 ratio) across an

entire strip, a variable conduction would show 2:1, then 3:2,

then back to 2:1, or maybe 4:3, all within the same strip.

VDD: Ventricle paced, double sensed, double response (AV

synchronous pacemaker).

Vector: Direction of flow of cardiac electrical activity;

represented by an arrow with the point indicating the positive

pole and the size of arrow indicating magnitude of current.

Ventricles: The lower two chambers of the heart.

Ventricular Depolarization: Discharge of electrical

activity throughout the ventricles to stimulate ventricular

contraction; produces the QRS complex on an EKG.

Ventricular Fibrillation (VF): The arrhythmia in which

the ventricles are controlled by numerous irritable foci,

producing chaotic, ineffective muscle activity rather than the

normal contraction.

Ventricular Flutter (VF): The arrhythmia in which a single

irritable focus in the ventricles depolarizes the heart at a rate

greater than 250 bpm; usually considered to be a rapid form

of Ventricular Tachycardia.

Ventricular Hypertrophy: Enlargement of myocardial wall

in one or more of the ventricles.

Ventricular Pacemaker: An electrical stimulus from the

ventricles that controls heart rhythm; an artificial pacemaker

that stimulates only the ventricles.

Ventricular Standstill: The arrhythmia in which the

ventricles are not depolarized by any electrical stimulation

and therefore do not contract; if atrial activity is present, it

is not conducted through the AV node; if no atrial activity is

present, it is called Asystole.

Ventricular Tachycardia (VT): The arrhythmia in which a

single irritable focus in the ventricles depolarizes the heart at

a rate of 150–250 bpm.

VF: Ventricular Fibrillation, Ventricular Flutter.

VT: Ventricular Tachycardia.

Vulnerable Period: The period in the cardiac cycle when

the heart is most susceptible to premature discharge,

with a resultant ineffective pattern if it receives a strong

enough electrical stimulus; the Relative Refractory Period;

corresponds with the downslope of the T wave.

VVI: Ventricle paced, ventricle sensed, inhibited response

(ventricular demand pacemaker).

Wandering Pacemaker (WP): The arrhythmia in which the

pacemaker site shifts from the SA node to the atrium and

back again, sometimes dropping as low as the AV junction.

Waves: Deflections on the electrocardiograph caused by

changes in electrical activity in the heart.

Wenckebach: The form of Second-Degree AV Block in which

the node progressively holds each impulse longer until one

is eventually not conducted, then the cycle starts over; Type I

Second-Degree Heart Block.

WP: Wandering Pacemaker.

551

Chapter 2,

Practice Strips Answers

PART I: LABELING WAVES

Answers Key

2.1

P

S

T

R

2.2

P T

S

R

2.3

R

T

S

Q

P

2.4

R

P

Q

T

2.5

P T

QS

2.6

P

R

T

S

552 Answers Key

2.7

P R T

Q S

2.8

R

T P

2.9

R

T P

Q

2.10

R

T

P

S Q

2.11

T R P

Q S

2.12

R

T

P

Q S

Answers Key 553

Chapter 3

Regularity: regular

Rate: 79 bpm

P Waves: regular

P–P interval; uniform

waves

PRI: 0.16 second and

constant

QRS: 0.08 second

Regularity: regular (very

slightly irregular)

Rate: approximately 90 bpm

P Waves: uniform; regular

P–P interval

PRI: 0.12 second and

constant

QRS: 0.08 second

Regularity: regular

Rate: 63 bpm

P Waves: uniform; regular

P–P interval

PRI: 0.16 second and

constant

QRS: 0.10 second

3.1

3.2

3.3

Regularity: regular

Rate: 125 bpm

P Waves: uniform, regular

P–P interval

PRI: 0.16 second and

constant

QRS: 0.08 second

3.4

Regularity: regular

Rate: 83 bpm

P Waves: uniform; regular

P–P interval

PRI: 0.16 second and

constant

QRS: 0.12 second

3.5

Regularity: regular

Rate: 107 bpm

P Waves: uniform; regular

P–P interval

PRI: 0.20 second and

constant

QRS: 0.10 second

3.6

Regularity: regular

Rate: 79 bpm

P Waves: uniform; regular

P–P intervals

PRI: 0.10 second and

constant

QRS: 0.06 second

3.7

Regularity: regular

Rate: 79 bpm

P Waves: uniform; regular

P–P interval

PRI: 0.16 second and

constant

QRS: 0.10 second

3.8

Regularity: regular

Rate: 83 bpm

P Waves: uniform; regular

P–P interval

PRI: 0.20 second and

constant

QRS: 0.08 second

3.9

Regularity: irregular

Rate: approximately

80 bpm

P Waves: uniform; irregular

P–P interval

PRI: 0.16 second and

constant

QRS: 0.10 second

3.10

Regularity: regular (very

slightly irregular)

Rate: 83 bpm

P Waves: upright and

uniform

PRI: 0.14 second

QRS: 0.10 second

3.11

Regularity: regular

Rate: 50 bpm

P Waves: upright and

uniform

PRI: 0.12 second

QRS: 0.08 second

3.12

Regularity: regular

Rate: 79 bpm

P Waves: upright and

uniform

PRI: 0.12 second

QRS: 0.08 second

3.13

Regularity: irregular

Rate: 70 bpm

P Waves: upright and

uniform

PRI: 0.16 second

QRS: 0.08 second

3.14

Regularity: regular (very

slightly irregular)

Rate: 79 bpm

P Waves: upright and

uniform

PRI: 0.16 second

QRS: 0.08 second

3.15

Chapter 4

Regularity: regular (slightly

irregular)

Rate: 48 bpm

P Waves: uniform and upright; regular P–P interval

PRI: 0.18 second and

constant

QRS: 0.12 second

Interp: Sinus Bradycardia

(with wide QRS)

4.1

Regularity: irregular

Rate: approximately 80 bpm

P Waves: uniform and upright; regular P–P interval

PRI: 0.14 second and

constant

QRS: 0.06 second

Interp: Sinus Arrhythmia

4.2

Regularity: regular

Rate: 75 bpm

P Waves: uniform and

upright; regular

P–P interval

PRI: 0.16 second and

constant

QRS: 0.08 second

Interp: Normal Sinus

Rhythm

4.3

Regularity: regular

Rate: 136 bpm

P Waves: uniform and upright; regular P–P interval

PRI: 0.16 second and

constant

QRS: 0.06 second

Interp: Sinus Tachycardia

4.4