30 Basic ECG MCQs for NCCT Surgical Technologist Exam Prep

The normal PR interval on an ECG is

0.12–0.20 sec

Which wave on the ECG represents atrial depolarization?

P wave

A widened QRS complex (>0.12 sec) usually indicates:

Bundle branch block

. What is the normal heart rate range for sinus rhythm?

60–100 bpm

Which ECG finding is most consistent with atrial fibrillation?

Irregularly irregular rhythm with absent P waves

In a normal 12-lead ECG, lead II is commonly used to:

Monitor atrial activity

A flat line with occasional QRS complexes indicates:

Complete heart block with ventricular escape rhythm

The T wave on ECG represents:

Ventricular repolarization

The QT interval represents:

Ventricular depolarization and repolarization

Tall peaked T waves are most often seen in:

Hyperkalemia

Which of the following rhythms is characterized by a sawtooth pattern?

Atrial flutter

The ST segment elevation in multiple leads is most consistent with:

Pericarditis

The normal QRS duration is:

0.08–0.12 sec

In complete (third-degree) heart block, the ECG shows:

No relationship between P waves and QRS complexes

Which rhythm is described as chaotic, irregular, with no identifiable P waves or QRS complexes?

Ventricular fibrillation

Which lead is most useful for detecting inferior wall myocardial infarction?

I, aVL

Sinus bradycardia is defined as sinus rhythm with a rate:

<60 bpm

A prolonged PR interval (>0.20 sec) indicates:

First-degree AV block

Which electrolyte abnormality is most associated with U waves?

Hypokalemia

The best lead to monitor for atrial activity (P waves) during anesthesia is:

Lead II

The pacemaker of the heart is normally the:

SA node

A run of ≥3 consecutive ventricular beats at >100 bpm is called:

Ventricular tachycardia

Which rhythm is a shockable cardiac arrest rhythm?

Ventricular fibrillation

A narrow QRS complex tachycardia (>150 bpm) with absent P waves is most consistent with:

Supraventricular tachycardia (SVT)

Which condition is most likely if the ST segment is depressed?

Ischemia or digitalis effect

The R-R interval on the ECG is used to determine:

Heart rate

The small box on ECG paper represents:

0.4 sec

Which leads look at the lateral wall of the left ventricle?

I, aVL, V5, V6

The U wave is best seen in:

Lead V2–V3

Which of the following is the most dangerous rhythm and requires immediate defibrillation?

Ventricular fibrillation