ECG ECG Waveform Measurements and Intervals 2

Question 1

How many small squares represent 0.04 seconds at standard ECG paper speed (25 mm/sec)?

Accepted Answer

1 small square

Answer

At 25 mm/sec, each small square is 1 mm wide = 0.04 seconds, so 1 small square = 0.04 sec.

Question 2

Which measurement in the ECG is most commonly used to detect left ventricular hypertrophy?

Accepted Answer

QRS voltage amplitude in precordial leads (Sokolow-Lyon criteria)

Answer

The Sokolow-Lyon criteria (S in V1 + R in V5 or V6 ≥35 mm) uses QRS voltage amplitude to suggest left ventricular hypertrophy.

Question 3

ST elevation ≥1 mm in two contiguous leads is significant because it suggests:

Accepted Answer

Acute myocardial infarction (STEMI) until proven otherwise

Answer

ST elevation ≥1 mm in two or more contiguous leads is the hallmark ECG finding of STEMI (ST-elevation myocardial infarction), requiring urgent intervention.

Question 4

The normal axis of the QRS complex in adults falls between:

Accepted Answer

-30° to +90°

Answer

Normal QRS axis is -30° to +90°, reflecting the predominant left and inferior direction of ventricular depolarization through the His-Purkinje system.

Question 5

A delta wave on the ECG is associated with:

Accepted Answer

Wolff-Parkinson-White (WPW) syndrome pre-excitation

Answer

A delta wave is the slurred upstroke at the start of the QRS caused by accessory pathway pre-excitation in WPW syndrome, bypassing the AV node.

ECG (Electrocardiogram) Practice Test

ECG (Electrocardiogram) Practice Test

ECG ECG Waveform Measurements and Intervals 2