ECG ECG Troubleshooting 5

Question 1

An ECG shows a wide complex tachycardia at 180 bpm with AV dissociation. What is the most likely diagnosis?

Accepted Answer

Ventricular tachycardia

Answer

AV dissociation (P waves marching through QRS independently) in a wide complex tachycardia is a hallmark of ventricular tachycardia.

Question 2

When recording a right-sided ECG (V3R-V6R), what is the primary clinical indication?

Accepted Answer

Suspected right ventricular MI in the setting of inferior STEMI

Answer

Right-sided leads are obtained when inferior STEMI is present to detect right ventricular involvement, which changes management (avoid nitrates and diuretics).

Question 3

A patient's ECG shows a QRS duration of 140 ms with a broad, notched R wave in leads I, aVL, V5, and V6, and absence of septal Q waves. What is the diagnosis?

Accepted Answer

Left bundle branch block

Answer

Left bundle branch block (LBBB) produces broad, notched R waves (M-shaped) in lateral leads (I, aVL, V5-V6) with absent septal Q waves and QRS ≥ 120 ms.

Question 4

What is the most common cause of pseudo-Q waves (QS pattern) in leads V1-V2 in an otherwise healthy patient?

Accepted Answer

Incorrect precordial electrode placement (too high)

Answer

Placing V1 and V2 electrodes one or two intercostal spaces too high is the most common technical cause of QS patterns mimicking anteroseptal infarction.

Question 5

A patient on digoxin therapy has an ECG showing scooped ST depression in lateral leads, shortened QT, and slow ventricular rate. What is the most likely finding?

Accepted Answer

Digitalis effect (therapeutic digoxin changes)

Answer

The digitalis effect refers to the characteristic scooped (reverse tick) ST depression, QT shortening, and bradycardia seen with therapeutic digoxin levels.

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ECG ECG Troubleshooting 5