CMC CMC Cardiac Diagnostics & Imaging 1

Question 1

What does the PR interval on an ECG represent?

Accepted Answer

Conduction time from atrial depolarization through the AV node to ventricular activation

Answer

The PR interval reflects total conduction time from SA node firing through the AV node and His-Purkinje system to ventricular activation.

Question 2

ST elevation in ECG leads II, III, and aVF is most consistent with infarction of which cardiac territory?

Accepted Answer

Inferior wall (RCA territory)

Answer

Leads II, III, and aVF are inferior leads; ST elevation in these leads indicates inferior STEMI, usually from RCA occlusion.

Question 3

A corrected QT interval (QTc) greater than 500ms on ECG significantly increases the risk of which arrhythmia?

Accepted Answer

Torsades de Pointes

Answer

QTc >500ms indicates severe repolarization prolongation, greatly increasing the risk of Torsades de Pointes and sudden cardiac death.

Question 4

Which ECG change is one of the earliest and most characteristic findings in hyperkalemia?

Accepted Answer

Peaked, tall, narrow T waves

Answer

Peaked T waves are the earliest ECG sign of hyperkalemia and result from accelerated ventricular repolarization.

Question 5

Why is new left bundle branch block (LBBB) in a patient with chest pain clinically significant?

Accepted Answer

New LBBB may be a STEMI equivalent requiring emergent catheterization

Answer

New LBBB with ischemic symptoms meets Sgarbossa criteria and should be treated with the same urgency as ST-elevation MI.

CMC - Cardiac Medicine Certification Practice Test