DC Dysrhythmia Pathophysiology & Electrophysiology 2

Question 1

Which arrhythmia mechanism involves an impulse reentering previously depolarized tissue through an alternative pathway?

Accepted Answer

Reentry via a circular conduction circuit

Answer

Reentry occurs when an impulse reenters depolarized tissue through an alternative pathway before full repolarization, creating a self-sustaining circular electrical circuit responsible for many tachyarrhythmias.

Question 2

Why is the peak of the T wave considered the 'vulnerable period' of the cardiac cycle?

Accepted Answer

Ventricular repolarization is inhomogeneous, making the heart susceptible to VF induction

Answer

During the T wave peak, ventricular repolarization is uneven across myocardial cells, creating dispersion of refractoriness that makes the heart highly susceptible to R-on-T phenomenon triggering VF.

Question 3

Which ion is primarily responsible for the rapid depolarization phase (phase 0) of the ventricular action potential?

Accepted Answer

Sodium (Na+) influx

Answer

Phase 0 (rapid depolarization) of the ventricular action potential is driven by the rapid influx of sodium ions through fast voltage-gated sodium channels, producing the steep upstroke.

Question 4

Which arrhythmia most directly results from enhanced automaticity in an ectopic focus?

Accepted Answer

Premature ventricular contractions originating from an irritable focus

Answer

Enhanced automaticity occurs when ectopic foci outside the SA node develop an abnormally accelerated spontaneous depolarization rate, generating premature beats or sustained tachyarrhythmias.

Question 5

What is the primary electrophysiologic mechanism underlying Wolff-Parkinson-White (WPW) syndrome tachycardia?

Accepted Answer

Reentry using an accessory pathway (Bundle of Kent)

Answer

WPW tachycardia is caused by reentrant conduction using an accessory pathway (Bundle of Kent) that bypasses the AV node, creating an atrioventricular circuit capable of sustaining rapid tachycardia.

(DC) Dysrhythmia Certification Practice Test

(DC) Dysrhythmia Certification Practice Test

DC Dysrhythmia Pathophysiology & Electrophysiology 2