Narrow-Complex Supraventricular Tachycardia Lecture Review

Flashcards covering the classification, diagnostic criteria, and physiological mechanisms of narrow-complex supraventricular tachycardias (SVT).

Supraventricular Tachycardia (SVT)

A rhythm with a ventricular rate greater than or equal to $100\,BPM$ where the rhythm starts or is maintained by tissue located in the sinus node, atria, atrioventricular (AV) node, bundle of His, or a combination of these sites.

Narrow-Complex SVT

An SVT with a QRS complex duration of less than $0.12\,s$, occurring because the ventricular depolarization wave uses the normal electrical conduction system.

Wide-Complex Tachycardia (WCT)

A rhythm with a QRS complex duration greater than or equal to $0.12\,s$, caused by ventricular depolarization traveling through aberrant pathways or direct cell-to-cell transmission.

AV Nodal Reentry Tachycardia (AVNRT)

The most common narrow-complex SVT, accounting for approximately $60\%$ of clinical cases, typically involving dual pathways in the AV node.

Orthodromic AV Reentry Tachycardia (AVRT)

A reentry tachycardia, accounting for approximately $30\%$ of SVTs, where the impulse travels down the AV node normally and returns to the atria via an accessory pathway (bypass tract).

Focal Atrial Tachycardia (Focal AT)

A rhythm originating from increased automaticity at a single ectopic atrial focus, accounting for approximately $10\%$ of clinical SVT cases.

Physiologic Sinus Tachycardia

Sinus tachycardia that develops normally as a response to stressors such as exercise, fever, or caffeine, with a maximum heart rate calculated as $220 - \text{patient's age}$.

Inappropriate Sinus Tachycardia

The presence of sinus tachycardia where no physiologic cause or stressor can be found to account for the rapid heart rate.

Multifocal Atrial Tachycardia (MAT)

A rhythm caused by at least three different pacemakers firing throughout the atria, typically associated with patients suffering from severe chronic obstructive pulmonary disease (COPD).

Atrial Flutter

A rhythm created by an atrial macroreentry circuit, characterized by a sawtooth baseline pattern of F waves at atrial rates typically between $250\,BPM$ and $350\,BPM$.

Atrial Fibrillation

The most common pathologic arrhythmia, characterized by an irregularly irregular rhythm with fibrillatory f waves at rates between $400\,BPM$ and $600\,BPM$ and the absence of observable P waves.

Junctional Tachycardia

An SVT triggered by increased automaticity at the level of the AV node, frequently seen after acute myocardial infarction, digoxin toxicity, or cardiac surgery.

Cannon A Waves

A physical finding of abrupt elevation in jugular venous pressure occurring when the right atrium contracts against a closed tricuspid valve.

Delta Wave

A slurred upstroke of the QRS complex seen in preexcitation states, indicating early ventricular activation via an accessory tract.

Preexcitation

Conduction of an atrial impulse to the ventricles via an accessory pathway rather than the normal AV node-His-Purkinje system, often evidenced by a delta wave and short PR interval.

Relative Ischemia

An imbalance where myocardial oxygen demand exceeds supply, often caused by the increased heart rate of a tachycardia rather than atherosclerotic disease.

Atrial Kick

The small amount of extra ventricular overfilling produced by atrial contraction at the end of diastole, which helps maximize stroke volume.

RP Interval

The distance from the beginning of the QRS complex to the beginning of a retrogradely conducted P wave.

AV Node-Dependent SVTs

A classification of SVTs, including AVNRT and AVRT, that require the AV node to function as part of the circuit to maintain the arrhythmia.

Isoelectric Segment

A portion of an ECG lead that appears invisible or as a straight baseline because the positive and negative deflections perfectly cancel each other out.

Electrical Alternans (QRS Alternans)

A variability in the amplitude of the R wave height, potentially suggesting cardiac tamponade in the presence of hemodynamic compromise.

Adenosine

An ultra-short-acting pharmaceutical agent that causes a slowdown of sinus node automaticity and marked slowing of AV nodal conduction for less than $5\,s$.

Diagnostic Trial

The use of a procedure or pharmaceutical agent (such as adenosine or a Valsalva maneuver) specifically to assist in identifying a diagnosis.