Cardiac Unit 2 Exam Prep

Vocabulary flashcards covering cardiac electrophysiology, cell junction structures, conduction pathways, ECG leads and waveforms, heart sounds, arrhythmias, diagnostic tests, and associated echocardiographic findings.

Gap Junctions

Electrical connections located in intercalated discs that act like tiny communication tunnels between neighboring heart cells, allowing ions and electrical impulses to pass directly to enable coordinated depolarization.

Desmosomes

Mechanical connections in intercalated discs that act as strong spot welds physically holding heart cells together to prevent them from pulling apart during powerful cardiac contractions.

Depolarization

The electrical process wherein the movement of ions (such as sodium and calcium) across the cell membrane changes the negatively charged cell membrane to positive, leading to cardiac muscle contraction.

Repolarization

The process wherein ions (specifically potassium moving out of the cardiac cell) return to their starting place to restore membrane polarity, allowing the muscle to relax and prepare for the next excitation.

Sinoatrial Node (SA Node)

The primary pacemaker of the heart, located in the right atrium near the superior vena cava, composed of specialized cells that initiate electrical impulses by spontaneous depolarization at an intrinsic rate of $60$ to $100\text{ bpm}$.

Atrioventricular Node (AV Node)

The gatekeeper of the electrical system located in the right atrium near the opening of the coronary sinus; it delays the electrical impulse (intrinsic rate of $40$ to $60\text{ bpm}$) to allow the atria to empty and ventricles to fill.

Bundle of His

Specialized cardiac muscle fibers located in the interventricular septum that transmit electrical action potentials down toward the heart's apex at an intrinsic rate of $20\text{ bpm}$.

Cardiac Conduction System

The specialized pathway consisting of the SA node, AV node, Bundle of His, left/right bundle branches, and Purkinje fibers that transmits electrical signals through the heart to coordinate contractions.

Purkinje Fibers

Specialized cardiac muscle fibers located in the heart's apex that conduct electrical impulses to the innermost layer (endocardium) of the ventricular walls, initiating ventricular contraction from the apex upward.

Bachmann's Bundle

The specialized interatrial conduction path that disperses the electrical impulse from the SA node across to the left atrium.

Coronary Sinus

A collector vessel that receives blood from cardiac veins and empties into the right atrium, serving as an anatomical landmark near which the AV node is situated.

Ground Lead (RL)

The electrode placed on the right leg during a 12-lead ECG that reduces interference and acts as a reference without contributing to heart activity recordings on the graph paper.

Lead II

The rhythm strip tracing that displays electrical activity from the right arm to the left leg, providing the clearest view of overall heart rhythm and conduction.

P Wave

The ECG waveform representing atrial depolarization, an electrical event that results in atrial contraction (systole).

PR Interval

The ECG time interval measured from the start of atrial depolarization (beginning of P wave) to the start of ventricular depolarization (beginning of QRS complex), reflecting impulse conduction through the AV node.

QRS Complex

The large ECG waveform representing ventricular depolarization, which leads to the mechanical contraction of the ventricles.

ECG Waveform

The graphic representation of electrical activity in the heart recorded over time, consisting of P waves, QRS complexes, ST segments, and T waves.

ST Segment

The flat ECG segment representing the period when the ventricles are fully depolarized and actively pumping blood; its elevation above baseline can indicate myocardial infarction.

T Wave

The ECG waveform representing ventricular repolarization, which corresponds to the mechanical relaxation of the ventricles.

R-R Interval

The duration between consecutive R wave peaks on an ECG representing one complete cardiac cycle ($\approx 0.8\text{ seconds}$ at rest).

Systole

The period of the cardiac cycle occupying approximately $0.3\text{ seconds}$ during which the heart chambers (typically referring to ventricles) actively contract and pump blood.

Diastole

The period of the cardiac cycle occupying approximately $0.5\text{ seconds}$ during which the ventricles relax and fill with blood under lower pressure.

S1

The first heart sound ("lubb"), caused by the closure of the atrioventricular valves (mitral and tricuspid) at the beginning of isovolumic contraction when ventricular pressure exceeds atrial pressure.

S2

The second heart sound ("dupp"), caused by the closure of the semilunar valves (aortic and pulmonary) at the start of isovolumic relaxation when ventricular pressure falls below arterial pressure.

S3

A third heart sound ("ventricular gallop") caused by rapid ventricular filling and wall vibration; normal in young individuals, but associated with volume overload/congestive heart failure in older adults.

S4

A fourth heart sound ("atrial gallop") occurring just before S1 when the atria contract to force blood into a stiff or non-compliant ventricle.

Heart Murmur

An extra auditory sound heard between normal heart sounds (S1 and S2) caused by turbulent blood flow, graded 1 to 6, which may be innocent or indicative of valve pathology.

Normal Sinus Rhythm (NSR)

The regular cardiac rhythm originating from the SA node with a rate between $60$ and $100\text{ bpm}$ in adults, characterized by equal R-R intervals and P waves preceding every QRS complex.

Sinus Bradycardia

A regular heart rhythm originating from the SA node at a rate below $60\text{ bpm}$; rates below $40\text{ bpm}$ are classified as severe.

Sinus Tachycardia

A regular heart rhythm originating from the SA node at a rate above $100\text{ bpm}$; sustained rates exceeding $120\text{ bpm}$ at rest warrant physician notification.

Sinus Arrhythmia

A cardiac rhythm where the distance between QRS complexes (R-R interval) varies beat-to-beat, though P waves remain consistently present before each QRS complex.

Left Bundle Branch Block (LBBB)

An electrical conduction delay in the left bundle branch leading to delayed activation of the left ventricle, causing a wide QRS complex on the ECG and often associated with left-heart conditions or septal bounce on echocardiography.

Right Bundle Branch Block (RBBB)

A conduction delay in the right bundle branch resulting in late right ventricular activation and a wide QRS complex, typically associated with pulmonary or right-heart pathology.

Ectopic Beat

A premature contraction or extrasystole originating from an abnormal focus outside the SA node, such as Premature Atrial Contractions (PACs) or Premature Ventricular Contractions (PVCs).

Bigeminy

A rhythm pattern in which an ectopic beat occurs regularly every second beat.

Trigeminy

A rhythm pattern in which an ectopic beat occurs regularly every third beat.

Supraventricular Tachycardia (SVT)

A rapid heart rhythm ($>100\text{ bpm}$, typically $140$–$180\text{ bpm}$) originating above the ventricles due to an accessory pathway, producing narrow QRS complexes and sometimes managed via Valsalva maneuvers, medications, or ablation.

Atrial Fibrillation

An arrhythmia characterized by rapid, uncoordinated quivering of the atria from multiple ectopic sites, absence of P waves, variable QRS spacing, risk of atrial dilatation, and blood stasis leading to thrombus formation.

Atrial Flutter

An atrial arrhythmia caused by a circular re-entry loop firing at $250$–$350\text{ bpm}$, producing a classic uniform saw-tooth pattern on ECG between QRS complexes.

Ventricular Tachycardia

A potentially life-threatening arrhythmia characterized by wide QRS complexes occurring at a fast rate ($>100\text{ bpm}$); runs of $\ge 3$ complexes require image documentation and physician notification.

Ventricular Fibrillation

A medical emergency marked by rapid, chaotic, uncoordinated ventricular contraction appearing as a squiggly line on ECG, leading to rapid loss of consciousness and requiring immediate defibrillation and code activation.

Asystole

The complete absence of electrical and mechanical cardiac activity, represented by a flat line on the ECG.

Holter Monitor

A portable ECG recording device worn by a patient for at least $24\text{ hours}$ to detect sporadic or intermittent arrhythmias during normal daily activities.

Exercise Stress Test (EST)

A diagnostic procedure in which a patient walks on a treadmill with increasing speed/incline while monitored on an ECG to detect exercise-induced arrhythmias or ischemia; excessive blood pressure elevation requires stopping the test.

Septal Bounce

An abnormal, jerky motion of the interventricular septum seen on echocardiography, commonly caused by asynchronous ventricular contraction due to a left bundle branch block.

Wall Motion Abnormalities

Echocardiographic findings where segments of cardiac muscle show reduced or absent contraction, frequently reflecting local myocardial ischemia that may also disrupt the cardiac conduction system.