Practical Content and Preparation Flashcards

Right bundle branch block (RBBB) is classically identified by which pattern in lead V1?

Answer: RSR' (rabbit ear) pattern

RBBB produces a characteristic RSR' (M-shaped or 'rabbit ear') pattern in V1 with a QRS duration ≥0.12 seconds.

Which lead best visualizes the inferior wall of the left ventricle?

Answer: Leads II, III, and aVF

Leads II, III, and aVF face the inferior surface of the left ventricle and detect changes associated with inferior MI.

A patient's ECG shows P waves at 85 bpm with a QRS rate of 35 bpm, and no consistent PR interval. This finding is consistent with:

Answer: Complete (third-degree) AV block

Complete (third-degree) AV block means the atria and ventricles fire independently with no relationship between P waves and QRS complexes.

Which ECG change is the earliest and most sensitive indicator of acute hyperkalemia?

Answer: Tall, peaked (tented) T waves

Tall, narrow, peaked T waves are the earliest ECG manifestation of hyperkalemia, appearing when serum potassium rises above ~5.5 mEq/L.

For a patient with a heart rate of 150 bpm on a rhythm strip at 25 mm/sec, the R-R interval measures approximately how many large boxes?

Answer: 2 large boxes

At 25 mm/sec, 300 ÷ 150 bpm = 2 large boxes per R-R interval (the '300 method').

Artifact resembling a sinusoidal pattern at a rate close to the respiratory rate is most likely caused by:

Answer: Patient movement of the limb electrodes during breathing

Respiratory artifact occurs when limb electrode movement with each breath creates a slow, cyclical baseline wander synchronized with respiration.

The corrected QT interval (QTc) is calculated using Bazett's formula. A QTc greater than which value is considered prolonged in men?

Answer: 440 ms

A QTc >440 ms in men (>460 ms in women) is generally considered prolonged and associated with increased arrhythmia risk.