ECG Cheat Sheet 2026

The 30 highest-yield ECG facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. What document or agreement does a patient typically sign before an ECG is performed in a clinical setting? → HIPAA acknowledgment / consent to treat
2. Papillary muscles attach to the valve leaflets via which structures? → Tendinous cords (chordae tendineae)
3. The 'vulnerable period' of the cardiac cycle, when an R-on-T phenomenon can trigger ventricular fibrillation, corresponds to which ECG feature? → The ascending limb of the T wave (relative refractory period)
4. During ECG acquisition, the technician notices the calibration pulse measures 5 mm instead of the standard 10 mm. What does this indicate? → The gain is set to half standard (5 mm/mV)
5. Which finding on a 12-lead ECG is most suggestive of left ventricular hypertrophy (LVH)? → S wave in V1 plus R wave in V5 or V6 exceeding 35 mm
6. Why is a baseline ECG important before starting certain medications? → To detect pre-existing QT prolongation or other abnormalities
7. Which of the following candidates would typically NOT meet the standard eligibility requirements for an ECG certification exam? → A high school dropout with 5 years of ECG experience
8. A technician notices 60-Hz electrical interference on the ECG tracing. The most appropriate first step is to: → Check and improve electrode-skin contact and grounding
9. A candidate fails the NHA CET exam. What is the minimum waiting period before retaking it? → 30 days
10. Which of the following is TRUE about a left bundle branch block (LBBB) on ECG? → QRS duration ≥120 ms with broad notched R in V5/V6
11. What is first-degree AV block characterized by? → PR interval greater than 0.20 seconds with all P waves conducted
12. A patient's Holter recording shows frequent motion artifact during a specific 30-minute period. What is the BEST first step in analysis? → Correlate the time period with the patient's activity diary to identify the cause
13. Which autonomic input slows SA node firing by increasing K+ conductance and hyperpolarizing the cell? → Parasympathetic stimulation via muscarinic (M2) receptors
14. The QT interval on an ECG represents which electrophysiological event? → Total ventricular electrical systole (depolarization + repolarization)
15. A patient's ECG shows PR interval of 320 ms that is constant across all beats. How is this classified? → First-degree AV block
16. An ECG technician credential is best described as which level of healthcare worker? → Entry-level allied health professional
17. ST segment elevation most commonly indicates: → Acute myocardial injury
18. What is the normal resting membrane potential of a cardiac myocyte? → -90 mV
19. What is the recommended minimum number of leads monitored continuously in a telemetry unit? → 2
20. What is the function of the coronary sinus? → Collects deoxygenated blood from cardiac veins
21. On telemetry, a patient's rhythm suddenly shows fine, chaotic baseline deflections with no identifiable P waves, QRS complexes, or T waves. What is this rhythm? → Ventricular fibrillation
22. Which AAMI/IEC standard governs ECG electrode performance requirements in the US? → AAMI EC12
23. What is the most common cause of pseudo-Q waves (QS pattern) in leads V1-V2 in an otherwise healthy patient? → Incorrect precordial electrode placement (too high)
24. Which ECG feature distinguishes atrial flutter from atrial fibrillation? → Sawtooth flutter waves at ~300 bpm
25. What is the passing score threshold for the NHA CET exam expressed as a scaled score? → 400
26. On an ECG, the QT interval measures 480 ms at a heart rate of 60 bpm. What is the corrected QT (QTc) and its significance? → QTc = 480 ms; prolonged, risk of Torsades de Pointes
27. What is the primary function of an EKG technician during an ECG procedure? → Set up the equipment and ensure accurate lead placement
28. Which patient activity should be specifically avoided during standard Holter monitoring? → Showering or immersing in water
29. When a certification body requires 'documented clinical hours,' what does this typically mean? → Hours of hands-on patient care verified by a supervisor or employer
30. What is the significance of lead reversal on a 12-lead ECG? → It can mimic pathological conditions and lead to misdiagnosis