ECG Interpretation & Analysis Flashcards

A patient has irregularly irregular R-R intervals with no discernible P waves. The most likely diagnosis is:

Answer: Atrial fibrillation

Atrial fibrillation produces chaotic atrial activity (no distinct P waves) with an irregularly irregular ventricular response.

Which ECG finding indicates complete (third-degree) AV block?

Answer: P waves and QRS complexes firing independently

In complete heart block, the atria and ventricles depolarize independently due to complete failure of AV conduction, producing AV dissociation.

Left ventricular hypertrophy (LVH) by the Sokolow-Lyon criterion requires:

Answer: S in V1 + R in V5 or V6 ≥35 mm

The Sokolow-Lyon criterion for LVH is S wave depth in V1 plus the tallest R wave in V5 or V6 equaling ≥35 mm.

Which of the following best describes multifocal atrial tachycardia (MAT)?

Answer: Irregular rate with ≥3 distinct P wave morphologies

MAT requires a rate >100 bpm, an irregular rhythm, and at least three different P wave morphologies, reflecting multiple ectopic atrial foci.

ST elevation in leads V1–V4 with reciprocal depression in inferior leads most likely represents:

Answer: Anterior STEMI

The anterior precordial leads V1–V4 overlie the anterior left ventricular wall, and ST elevation in these leads indicates an anterior STEMI, typically from LAD occlusion.

A corrected QT interval (QTc) is calculated using Bazett's formula. Which formula is correct?

Answer: QTc = QT / √RR

Bazett's formula corrects the QT interval for heart rate by dividing the measured QT by the square root of the RR interval (in seconds): QTc = QT/√RR.

Which ECG change is associated with hypokalemia?

Answer: Prominent U waves and flattened T waves

Hypokalemia prolongs repolarization, manifesting as flattened or inverted T waves, prominent U waves, and a prolonged QU interval on ECG.