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

Triggered activity from afterdepolarizations

Answer

Enhanced automaticity of an ectopic focus

Answer

Abnormal phase 4 depolarization

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

The AV node is completely refractory during this time

Answer

All ventricular cells are simultaneously depolarized

Answer

Ischemia is most likely to manifest during this phase

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

Potassium (K+) efflux

Answer

Calcium (Ca2+) influx

Answer

Chloride (Cl-) influx

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

Atrial flutter sustained by macroreentry

Answer

Second-degree AV block from structural disease

Answer

Sinus bradycardia induced by vagal stimulation

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

Enhanced SA node automaticity

Answer

Triggered activity from early afterdepolarizations

Answer

Abnormal slow pathway conduction within the AV node

Question 6

Which electrophysiologic property describes the inability of cardiac cells to respond to a new stimulus immediately after depolarization?

Accepted Answer

Refractoriness

Answer

Automaticity

Answer

Conductivity

Answer

Excitability