Dale Dublin's Rapid Interpretation of EKG's: Core Vocabulary and Concepts

Vocabulary practice flashcards covering fundamental electrophysiology, waveforms, leads, rate, rhythm disturbances, conduction blocks, axis determination, chamber hypertrophy, myocardial infarction localization, and miscellaneous clinical conditions from Rapid Interpretation of EKG's by Dale Dubin, MD.

Electrocardiogram (EKG)

A permanent record of cardiac electrical activity inscribed on ruled graph paper that provides essential diagnostic information about the heart's function, structure, rate, and rhythm.

Depolarization

An advancing wave of positive charges carried through the myocardium by fast-moving $\text{Na}^+$ ions that causes the interiors of resting, negatively polarized myocytes to become positive and contract.

Repolarization

The recovery phase following depolarization during which cardiac myocyte interiors regain their resting negative charge through the controlled outflow of potassium ($\text{K}^+$) ions.

P Wave

The initial positive waveform recorded on the EKG representing the spreading wave of biatrial depolarization and the simultaneous mechanical contraction of both atria.

QRS Complex

The waveform on an EKG that represents the rapid depolarization of the entire ventricular myocardium and marks the initiation of ventricular contraction.

Q Wave

The initial downward deflection of the QRS complex that is never preceded by an upward deflection; when significant, it serves as the diagnostic hallmark of myocardial necrosis.

R Wave

The first upward deflection within the QRS complex, produced when a wave of ventricular depolarization advances toward a positive recording electrode.

S Wave

Any downward deflection in the QRS complex that is preceded by an upward R wave.

ST Segment

The horizontal segment of baseline following the QRS complex that represents the early plateau phase of ventricular repolarization.

T Wave

A broad hump following the ST segment that represents the final rapid phase of ventricular repolarization, accomplished by potassium ($\text{K}^+$) ions leaving the myocytes.

QT Interval

The duration measured from the beginning of the QRS complex to the end of the T wave, representing total ventricular systole; it is normally less than half of the R-to-R interval at normal heart rates.

Bipolar Limb Leads

Standard limb leads (Leads I, II, and III) recorded by utilizing two active electrodes—one designated as positive and one as negative—positioned on the right arm, left arm, and left leg (forming Einthoven's triangle).

Augmented Limb Leads

Unipolar leads ($\text{AVR}$, $\text{AVL}$, and $\text{AVF}$) introduced by Dr. Emanuel Goldberger that amplify the voltage recorded from a single positive electrode relative to a common negative ground formed by the other two electrodes.

Precordial (Chest) Leads

Six standard unipolar leads ($\text{V}_1$ through $\text{V}_6$) introduced by Dr. Frank Wilson that record electrical activity in the horizontal plane using a positive suction-cup electrode positioned across the chest.

Lateral Leads

Leads I and $\text{AVL}$, which utilize a positive electrode placed laterally on the patient's left arm to detect electrical activity directed toward the left side of the heart.

Inferior Leads

Leads II, III, and $\text{AVF}$, which utilize a positive electrode positioned inferiorly on the patient's left foot to detect depolarization moving downward toward the base of the heart.

Sympathetic Nervous System (Cardiac Effects)

The autonomic division that secretes norepinephrine to stimulate cardiac $\beta_1$ adrenergic receptors, increasing the SA Node pacing rate, accelerating conduction velocity, increasing contractile force, and raising focus irritability.

Parasympathetic Nervous System (Cardiac Effects)

The autonomic division that releases acetylcholine via the vagus nerves to activate cardiac cholinergic receptors, resulting in inhibition of the SA Node pacing rate, depression of the AV Node, and diminished contractile force.

Vagal Maneuvers

Physical techniques (such as induced gagging or carotid sinus massage) that elicit a reflex parasympathetic response to slow AV Node conduction or depress irritable supraventricular foci.

Sinus Arrhythmia

A normal physiological mechanism wherein the SA Node pacing rate minimally accelerates during inspiration via sympathetic stimulation and decelerates during expiration via parasympathetic inhibition.

Overdrive Suppression

The fundamental characteristic of all automaticity centers in which the center with the fastest pacing rate suppresses the spontaneous pacemaking discharge of all lower, slower automaticity foci.

Automaticity Foci

Potential backup pacemaking sites located in the specialized conduction pathways of the atria ($60\text{--}80/\text{min}$), the AV Junction ($40\text{--}60/\text{min}$), and the ventricles ($20\text{--}40/\text{min}$).

Sinus Bradycardia

A regular cardiac rhythm originating in the SA Node with a pacing rate slower than $60/\text{min}$ (fewer than one beat per second).

Sinus Tachycardia

A regular rhythm originating in the SA Node that paces at a rate exceeding $100/\text{min}$, commonly induced by exercise or increased sympathetic stimulation.

Wandering Pacemaker

An irregular rhythm with a rate under $100/\text{min}$ caused by pacemaking activity wandering from the SA Node to multiple nearby atrial automaticity foci, producing varying cycle lengths and different $\text{P}^\prime$ wave shapes.

Multifocal Atrial Tachycardia (MAT)

A rapid, irregular rhythm with a rate exceeding $100/\text{min}$ common in patients with COPD, characterized by $\text{P}^\prime$ waves showing three or more distinct morphological signatures from competing, unsuppressed atrial foci.

Atrial Fibrillation

A chaotic, irregular rhythm caused by the simultaneous rapid firing ($350\text{--}450/\text{min}$) of multiple parasystolic atrial foci, resulting in an erratic baseline of tiny spikes without P waves and an irregular ventricular response.

Escape Rhythm

A sustained backup rhythm produced when an automaticity focus escapes overdrive suppression to pace at its inherent rate following the complete failure or cessation of the dominant higher pacemaker.

Escape Beat

A single spontaneous discharge emitted by a lower automaticity focus in response to a transient pause (such as one missed cycle) before regular SA Node pacing resumes.

Sinus Arrest

The failure of a sick SA Node to generate pacemaking stimuli, leaving the heart electrically silent until an automaticity focus escapes to assume pacing responsibility.

Premature Atrial Beat (PAB)

An early beat originating in an irritable atrial automaticity focus that produces an unexpected $\text{P}^\prime$ wave, depolarizes the atria, and resets the SA Node pacing cycle.

Aberrant Ventricular Conduction

The temporary non-simultaneous depolarization of the ventricles that occurs when an early supraventricular impulse encounters one bundle branch that is still refractory, resulting in a slightly widened QRS complex.

Premature Ventricular Contraction (PVC)

A giant, widened, and bizarre ventricular complex originating prematurely from an irritable ventricular automaticity focus, commonly provoked by cardiac hypoxia.

Ventricular Parasystole

A dual rhythm occurring when an entrance-blocked ventricular focus cannot be overdrive-suppressed and continuously paces at its inherent rate alongside the dominant Sinus Rhythm.

Paroxysmal Tachycardia

A sudden, rapid tachyarrhythmia originating in a very irritable automaticity focus with a typical rate range of $150\text{--}250/\text{min}$.

Paroxysmal Atrial Tachycardia (PAT) with Block

A tachyarrhythmia characterized by rapid, spiked $\text{P}^\prime$ waves and a $2:1$ conduction block through the AV Node, strongly indicative of digitalis excess or toxicity.

Supraventricular Tachycardia (SVT)

An umbrella designation for rapid rhythms ($150\text{--}250/\text{min}$) originating from irritable foci located above the ventricles, including Paroxysmal Atrial Tachycardia and Paroxysmal Junctional Tachycardia.

Ventricular Tachycardia (VT)

A life-threatening tachyarrhythmia originating from a very irritable ventricular focus pacing at $150\text{--}250/\text{min}$, characterized by consecutive wide PVC-like complexes, AV dissociation, and occasional capture or fusion beats.

Torsades de Pointes

A peculiar form of rapid ventricular rhythm ($250\text{--}350/\text{min}$) presenting in spindle-shaped bursts with complexes that twist around the baseline, typically caused by hypokalemia, potassium channel blockers, or long QT syndrome.

Atrial Flutter

A rapid tachyarrhythmia originating in an irritable atrial focus that paces at $250\text{--}350/\text{min}$, producing consecutive, identical saw-tooth flutter waves without an intervening baseline.

Ventricular Flutter

A rapid rhythm ($250\text{--}350/\text{min}$) produced by a single ventricular automaticity focus that generates smooth, regular sine waves of uniform amplitude, which typically deteriorates into ventricular fibrillation.

Ventricular Fibrillation (VF)

A form of cardiac arrest caused by the rapid, uncoordinated discharge ($350\text{--}450/\text{min}$) of multiple parasystolic ventricular foci, producing erratic bag-of-worms twitching without mechanical pumping or identifiable EKG waves.

Wolff-Parkinson-White (WPW) Syndrome

An accessory pathway syndrome caused by the Bundle of Kent, which short-circuits the normal AV delay to prematurely depolarize a portion of the ventricles, inscribing a slurred delta wave on the EKG.

Lown-Ganong-Levine (LGL) Syndrome

A condition in which the AV Node is bypassed by an accessory extension of the anterior internodal tract (James bundle), transmitting atrial depolarizations directly to the His Bundle without PR interval delay.

First-Degree ($1^\circ$) AV Block

A conduction delay in the AV Node that consistently prolongs the PR interval beyond $0.2\,\text{sec}$ (one large square) in every cardiac cycle while maintaining a 1:1 P-to-QRS relationship.

Wenckebach Second-Degree ($2^\circ$) AV Block

A second-degree AV block located in the AV Node characterized by progressive lengthening of the PR interval in successive cycles until a final P wave fails to conduct to the ventricles, producing a dropped QRS.

Mobitz Second-Degree ($2^\circ$) AV Block

A second-degree block located below the AV Node (in the His Bundle or Bundle Branches) characterized by normal PR intervals preceding occasional or regularly dropped QRS complexes in fixed ratios (such as $2:1$ or $3:1$).

Third-Degree ($3^\circ$) AV Block

A complete block of supraventricular conduction to the ventricles causing complete AV dissociation, in which an independent escape focus (Junctional at $40\text{--}60/\text{min}$ or ventricular at $20\text{--}40/\text{min}$) paces the ventricles.

Bundle Branch Block (BBB)

A conduction block in the Right or Left Bundle Branch that prevents simultaneous ventricular depolarization, widening the QRS duration to at least $0.12\,\text{sec}$ ($3$ small squares) and producing two out-of-phase peaks ($R,R^\prime$).

Right Bundle Branch Block (RBBB)

A bundle branch block wherein delayed depolarization of the right ventricle produces a characteristic $R,R^\prime$ pattern in the right chest leads ($\text{V}_1$ or $\text{V}_2$).

Left Bundle Branch Block (LBBB)

A bundle branch block wherein delayed depolarization of the left ventricle produces an $R,R^\prime$ pattern or a widened, notched peak in the left chest leads ($\text{V}_5$ or $\text{V}_6$).

Mean QRS Vector

The single net vector representing the general direction and magnitude of simultaneous ventricular depolarization, originating by convention at the AV Node.

Isoelectric QRS Complex

A QRS complex that records equal magnitudes of upward and downward deflection, indicating that depolarization is oriented perpendicular ($90^\circ$) to that lead.

Right Axis Deviation (RAD)

A frontal plane axis displacement where the Mean QRS Vector points toward the patient's right side ($+90^\circ \text{ to } +180^\circ$), detected by a predominantly negative QRS in lead I.

Left Axis Deviation (LAD)

A frontal plane axis displacement where the Mean QRS Vector points upward and leftward ($0^\circ \text{ to } -90^\circ$), indicated on EKG by a positive QRS in lead I and a negative QRS in lead AVF.

Diphasic P Wave

A P wave exhibiting deflections both above and below the baseline in lead $\text{V}_1$, where a large initial component indicates Right Atrial Enlargement and a wide terminal component indicates Left Atrial Enlargement.

Right Ventricular Hypertrophy (RVH)

Thickening of the right ventricular wall characterized by a tall R wave in lead $\text{V}_1$ (where R is larger than S) that becomes progressively smaller across leads $\text{V}_2$ through $\text{V}_4$, often accompanied by Right Axis Deviation.

Left Ventricular Hypertrophy (LVH)

Thickening of the left ventricular wall diagnosed when the depth of the S wave in lead $\text{V}_1$ plus the height of the R wave in lead $\text{V}_5$ exceeds $35\,\text{mm}$.

Ventricular Strain Pattern

An EKG abnormality associated with ventricular hypertrophy characterized by an ST segment that is depressed and humped upward in the middle, along with an asymmetrical inverted T wave.

Myocardial Infarction Triad

The electrocardiographic hallmarks of infarction comprising ischemia (inverted T waves), acute injury (ST segment elevation), and necrosis (significant Q waves).

Significant Q Wave

A pathological Q wave indicating myocardial necrosis that measures at least $1\,\text{mm}$ ($0.04\,\text{sec}$) in width or at least one-third the total amplitude of the QRS complex.

Anterior Infarction

An infarction of the anterior wall of the left ventricle caused by occlusion of the Anterior Descending branch of the Left Coronary Artery, diagnosed by significant Q waves in leads $\text{V}_1$, $\text{V}_2$, $\text{V}_3$, or $\text{V}_4$.

Lateral Infarction

An infarction of the lateral left ventricular wall resulting from occlusion of the Circumflex branch of the Left Coronary Artery, diagnosed by significant Q waves in lateral leads I and $\text{AVL}$.

Inferior Infarction

A diaphragmatic infarction involving the inferior left ventricular wall caused by occlusion of a terminal branch of the Right or Left Coronary Artery, identified by significant Q waves in leads II, III, and $\text{AVF}$.

Posterior Infarction

An acute infarction of the posterior wall of the left ventricle usually caused by Right Coronary Artery occlusion, manifested in leads $\text{V}_1$ and $\text{V}_2$ as mirror-image findings: large R waves and ST segment depression.

Anterior Hemiblock

A block of the anterior division of the Left Bundle Branch (often due to an occluded Anterior Descending artery) characterized by Left Axis Deviation, a normal or slightly widened QRS, and a $Q_1S_3$ pattern.

Posterior Hemiblock

A block of the posterior division of the Left Bundle Branch (often associated with inferior infarction) characterized by Right Axis Deviation, a normal or slightly widened QRS, and an $S_1Q_3$ pattern.

Bifascicular Block

A conduction block involving two of the ventricular fascicles, clinically defined as Right Bundle Branch Block combined with either an Anterior Hemiblock or a Posterior Hemiblock.

Brugada Syndrome

A hereditary disorder of cardiac sodium channels predisposing patients to sudden cardiac death, characterized by a Right Bundle Branch Block pattern with elevated, peaked, downsloping ST segments in leads $\text{V}_1$ through $\text{V}_3$.

Wellens Syndrome

A condition characterized by marked, symmetrical T wave inversion in leads $\text{V}_2$ and $\text{V}_3$, alerting to severe high-grade stenosis of the anterior descending coronary artery.

Long QT Syndrome

A hereditary or acquired anomaly wherein the QT interval exceeds half the duration of the cardiac cycle, predisposing patients to dangerous ventricular tachyarrhythmias, particularly Torsades de Pointes.

Pulmonary Embolus EKG Pattern ($S_1Q_3T_3$)

An acute cor pulmonale pattern resulting from a pulmonary embolus, characterized by a large S wave in lead I, a large Q wave and T wave inversion in lead III ($S_1Q_3T_3$), ST depression in lead II, and T wave inversion in leads $\text{V}_1\text{--}\text{V}_4$.

Hyperkalemia (EKG Manifestations)

Elevated serum potassium concentration that produces tall, pointed, peaked T waves, flattening or disappearance of P waves, and progressive widening of the QRS complex.

Hypokalemia (EKG Manifestations)

Decreased serum potassium concentration that causes flattening or inversion of the T wave and the emergence of a prominent U wave.

Digitalis Effect

A characteristic gradual, scooped downward curve of the ST segment resembling Salvador Dalí's mustache, associated with therapeutic digitalis administration and a shortened QT interval.

Demand Pacemaker

An artificial pacemaker programmed with an inherent pacing rate that remains overdrive-suppressed by normal Sinus rhythms but escapes to pace the heart if the patient's intrinsic rate falls below its programmed threshold.

Implantable Cardioverter Defibrillator (ICD)

A self-contained computerized unit implanted under the chest skin with cardiac leads capable of sensing arrhythmias, overdrive pacing ventricular tachycardia, providing cardioversion, or immediately defibrillating ventricular fibrillation.