DC Dysrhythmia Cardiac Rhythm Interpretation 5

Question 1

A patient with a permanent pacemaker set at 60 bpm shows pacemaker spikes not followed by QRS complexes. What problem does this indicate?

Accepted Answer

Failure to capture

Answer

Failure to capture occurs when the pacemaker delivers an electrical stimulus (spike) but the myocardium does not depolarize in response, producing a spike without a following QRS.

Question 2

On monitoring, a pacemaker-dependent patient's ECG shows the pacemaker firing at the programmed rate even though the patient's intrinsic rate exceeds 60 bpm and each native QRS is followed by another pacemaker spike. What malfunction is occurring?

Accepted Answer

Failure to sense (undersensing)

Answer

Undersensing (failure to sense) occurs when the pacemaker does not detect intrinsic cardiac activity and fires competitively, risking R-on-T phenomenon.

Question 3

Multifocal atrial tachycardia (MAT) is distinguished from atrial fibrillation by which ECG characteristic?

Accepted Answer

P waves with at least 3 distinct morphologies at a rate >100 bpm

Answer

MAT requires at least 3 different P-wave morphologies in the same lead at a rate >100 bpm, reflecting multiple ectopic atrial foci firing in an irregular pattern.

Question 4

Which criterion on the ECG distinguishes accelerated idioventricular rhythm (AIVR) from ventricular tachycardia?

Accepted Answer

Rate of 40–100 bpm (below the tachycardia threshold)

Answer

AIVR has the same wide QRS morphology as VT but runs at 40–100 bpm, just below the 100 bpm threshold that defines tachycardia.

Question 5

A 68-year-old patient's ECG shows ST elevation in leads II, III, and aVF with new-onset complete heart block. Which coronary artery is most likely occluded?

Accepted Answer

Right coronary artery (RCA)

Answer

The RCA supplies the inferior wall (II, III, aVF) and the AV node in most patients; occlusion can cause inferior MI with AV block.

(DC) Dysrhythmia Certification Practice Test

(DC) Dysrhythmia Certification Practice Test

DC Dysrhythmia Cardiac Rhythm Interpretation 5