How to Tackle ECG Questions in Under 45 Seconds

A structured reading framework that works on USMLE, PLAB, MRCP, MCCQE, and PMDC NLE.

ECG questions are the most skippable-looking questions on every medical licensing exam — but they are also the questions that separate pass-level candidates from high-pass candidates. Most students spend 2 to 3 minutes on a single ECG question, burning time they can't recover. This tip shows you a five-step reading pattern that gets you to the correct answer in about 45 seconds.

The five-step ECG read

You always read an ECG in the same order. Memorize this sequence and practice it on every ECG strip you see, clinical or exam:

  1. Rate. 300 divided by the number of big squares between two R waves. Tachycardia above 100, bradycardia below 60.
  2. Rhythm. Regular or irregular? Narrow-complex or wide-complex? P waves before every QRS?
  3. Axis. Lead I and aVF positive = normal. Lead I positive, aVF negative = left-axis deviation. Both negative = extreme right.
  4. Intervals. PR (0.12 to 0.20 seconds), QRS (under 0.12), QT (under half the RR interval).
  5. ST segment and T wave. ST elevation above 1 mm in two contiguous leads, or ST depression, or T-wave inversion.

For exam questions, 80 percent of the time the abnormality jumps out at step 2 or step 5. You rarely need to compute axis if the stem is pointing to an acute MI.

Pattern recognition beats theory

On test day, you are not going to re-derive principles. You are going to match patterns. These are the high-yield ECG patterns that show up on every exam:

  1. Wide-complex tachycardia + AV dissociation — VT until proven otherwise.
  2. Irregularly irregular, no P waves — atrial fibrillation. Then ask: rate control or rhythm control? CHA₂DS₂-VASc for anticoagulation.
  3. Delta wave + short PR — Wolff-Parkinson-White. Key answer choice: avoid AV-nodal blockers (adenosine, verapamil) if atrial fibrillation is present.
  4. ST elevation in II, III, aVF — inferior MI. Check for right-ventricular involvement (V4R). Avoid nitrates in RV infarction.
  5. ST elevation in V1 to V4 — anterior MI, LAD occlusion.
  6. Saddle-shape ST elevation across multiple leads — pericarditis (diffuse) or Brugada (V1 to V2 with specific morphology).
  7. Tall, tented T waves — hyperkalaemia. Progression: peaked T → wide QRS → sine wave → asystole.
  8. Long QT — congenital, drug-induced, or electrolyte-induced. Torsades de pointes risk.
  9. Low-voltage QRS with electrical alternans — cardiac tamponade.
  10. Left-axis deviation + S1Q3T3 pattern — classic (though insensitive) for pulmonary embolism.

Memorize these ten. They cover the vast majority of exam-level ECGs.

The trap: spending too long on "interesting" ECGs

Examiners sometimes include an unusual ECG — say a second-degree heart block, type 1 vs type 2 Mobitz — that looks educational. The trap is that you spend 3 minutes confirming you're right, and then bail on an easier question at the end. If you have the pattern at 30 seconds, commit. Move on.

How to drill this skill

Open your qbank, filter to cardiology questions only, set tutor mode, and commit to solving 25 questions in under 20 minutes. That is 48 seconds per question. You will miss a few the first time. By the third session, you will be within pace and your accuracy will climb to 75 percent or above.

Free 7-day MedLumen trial includes full cardiology filtering. See pricing and start free.