ECG Clinical Applications 3

Question 1

A patient with WPW syndrome develops atrial fibrillation. Which drug is contraindicated?

Accepted Answer

Adenosine

Answer

Adenosine blocks the AV node but not the accessory pathway in WPW, potentially accelerating conduction and causing ventricular fibrillation.

Question 2

Which ECG finding is associated with right ventricular infarction?

Accepted Answer

ST elevation in right-sided leads (V3R-V4R)

Answer

Right ventricular MI is diagnosed by ST elevation in right-sided leads (V3R-V4R), which are not part of standard 12-lead ECGs.

Question 3

A patient's ECG shows a prolonged PR interval of 280 ms with all P waves conducting normally. This is classified as:

Accepted Answer

First-degree AV block

Answer

A PR interval >200 ms with every P wave conducting to the ventricles defines first-degree AV block.

Question 4

During treadmill stress testing, which ECG finding is considered a positive result?

Accepted Answer

≥1 mm horizontal or downsloping ST depression

Answer

≥1 mm of horizontal or downsloping ST depression during exercise stress testing indicates myocardial ischemia.

Question 5

A patient has complete left bundle branch block (LBBB). Why is diagnosing acute MI difficult?

Accepted Answer

LBBB causes secondary ST-T changes that obscure ischemic patterns

Answer

LBBB produces secondary ST-T wave changes (discordant from QRS) that interfere with the standard ECG interpretation of ischemia.

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