AMCA EKG / Electrocardiography — Questions and Answers
Question 1: How many leads are recorded in a standard 12-lead ECG?
- 6
- 10
- 12 (Correct answer)
- 16
Correct answer: 12
A 12-lead ECG records 12 electrical views of the heart (I, II, III, aVR, aVL, aVF, and V1–V6), even though only 10 electrodes are physically placed on the patient.
Question 2: Which ECG lead is placed on the fourth intercostal space at the RIGHT sternal border?
- V1 (Correct answer)
- V2
- V3
- V4
Correct answer: V1
V1 is placed at the fourth intercostal space to the right of the sternum. V2 mirrors it on the left side, and the remaining precordial leads continue across the chest.
Question 3: A patient's ECG shows a sawtooth pattern at approximately 300 bpm with no discernible P waves. This finding is most consistent with:
- Ventricular fibrillation
- Atrial flutter (Correct answer)
- Normal sinus rhythm
- Atrial fibrillation
Correct answer: Atrial flutter
Atrial flutter characteristically produces a sawtooth (flutter wave) baseline at ~250–350 bpm. Atrial fibrillation produces an irregularly irregular baseline, while ventricular fibrillation is a chaotic, life-threatening rhythm.
Question 4: Somatic tremor artifact on an ECG tracing is MOST likely caused by:
- Improper grounding of the machine
- Patient movement or muscle activity (Correct answer)
- Incorrect lead placement
- Low electrode gel conductivity
Correct answer: Patient movement or muscle activity
Somatic tremor artifact results from skeletal muscle movement — the patient shivering, trembling, or moving during recording. Asking the patient to lie still and relax resolves this artifact.
Question 5: Which interval on an ECG represents the total time for ventricular depolarization AND repolarization?
- PR interval
- QRS complex
- QT interval (Correct answer)
- ST segment
Correct answer: QT interval
The QT interval spans from the start of ventricular depolarization (Q wave) through the end of repolarization (T wave). A prolonged QT interval raises the risk of dangerous arrhythmias such as Torsades de Pointes.
Question 6: When a limb lead electrode falls off mid-recording, the BEST immediate action is to:
- Continue recording and note the artifact in the chart
- Stop the recording, reattach the electrode, and retake the tracing (Correct answer)
- Switch to a different lead configuration
- Increase the machine sensitivity to compensate
Correct answer: Stop the recording, reattach the electrode, and retake the tracing
A detached electrode creates lead-off artifact, rendering that lead's data invalid. The correct action is to stop, reattach the electrode with fresh gel if needed, ensure good skin contact, and repeat the tracing to ensure a clean, diagnostic-quality recording.
AMCA EKG / Electrocardiography
How many leads are recorded in a standard 12-lead ECG?