Ventricular Arrhythmia Identification Flashcards

The morphology of a PVC can provide information about where in the ventricle the ectopic focus is located. A PVC with LBBB morphology (negative QRS in V1) suggests the focus is located where?

Answer: Right ventricle

A PVC with LBBB morphology indicates the focus is in the right ventricle — the right ventricle activates first (making V1 negative as depolarization moves away), and the left ventricle activates later, similar to left bundle branch block pattern.

Idioventricular rhythm (ventricular escape rhythm) is expected to fire at which rate range?

Answer: 20-40 bpm

Ventricular escape pacemakers in the Purkinje fibers have the lowest intrinsic automaticity rate of 20-40 bpm, emerging when all higher pacemakers (SA node and AV junction) fail.

Which clinical condition most commonly causes unifocal PVCs in hospitalized patients without structural heart disease?

Answer: Electrolyte disturbances (hypokalemia, hypomagnesemia)

Electrolyte abnormalities — particularly hypokalemia and hypomagnesemia — are among the most common reversible causes of PVCs in hospitalized patients, as they alter membrane potential stability.

Ventricular flutter is best described by which ECG appearance?

Answer: Regular sinusoidal wide complex tachycardia at 200-300 bpm with no discernible QRS-T separation

Ventricular flutter appears as a regular, sinusoidal (smooth, continuous wave) wide complex tachycardia at 200-300 bpm where QRS complexes and T waves merge into continuous undulation without distinct separation.

In patients with frequent PVCs, which marker is most predictive of adverse outcomes (increased risk of sudden cardiac death)?

Answer: Presence of underlying structural heart disease, particularly reduced left ventricular ejection fraction

The most important prognostic factor for PVC-related adverse outcomes is underlying structural heart disease, particularly reduced LVEF — PVCs in structurally normal hearts carry a relatively benign prognosis.

What is the hallmark ECG finding that distinguishes accelerated idioventricular rhythm (AIVR) from ventricular tachycardia?

Answer: Rate: AIVR is 60-100 bpm while VT is 100 bpm or greater

AIVR has wide QRS complexes (ventricular origin) at 60-100 bpm — faster than the idioventricular escape rate (< 40 bpm) but below the VT threshold of 100 bpm.