Cardiac Dysrhythmias and Arrhythmias Flashcards

The R-on-T phenomenon is clinically dangerous because it can trigger:

Answer: Ventricular fibrillation

A PVC firing during the vulnerable repolarization phase (T wave) can precipitate ventricular fibrillation.

Torsades de pointes is a polymorphic ventricular tachycardia associated with:

Answer: Prolonged QT interval

Torsades de pointes occurs in the setting of a prolonged QT interval and is characterized by QRS complexes that twist around the isoelectric baseline.

Which electrolyte abnormality is most commonly associated with life-threatening ventricular arrhythmias?

Answer: Hypokalemia

Hypokalemia lowers the resting membrane potential, increasing myocardial excitability and predisposing to ventricular arrhythmias.

Accelerated idioventricular rhythm (AIVR) is characterized by a ventricular rate of:

Answer: 60-100 bpm

AIVR has a ventricular rate between 60-100 bpm, faster than a ventricular escape rhythm but slower than ventricular tachycardia.

A rhythm strip shows regular P waves at 85 bpm, but every other P wave is not followed by a QRS complex. This represents:

Answer: Mobitz Type II second-degree AV block with 2:1 block

Mobitz Type II can present with 2:1 conduction where every other P wave is blocked, and the PR intervals of conducted beats remain constant.

Which arrhythmia is characterized by a very rapid but organized ventricular rate of 150-300 bpm with wide, regular QRS complexes and no discrete P waves?

Answer: Ventricular flutter

Ventricular flutter appears as a sine-wave pattern with regular wide complexes at 150-300 bpm and is considered immediately life-threatening.

Which of the following best describes a bundle branch block on an ECG?

Answer: QRS duration ≥0.12 sec with aberrant morphology

Bundle branch blocks cause delayed ventricular conduction, widening the QRS to 0.12 sec or greater with characteristic morphology changes.