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MBBS QUESTION #10241
Question 1
Third-degree (complete) atrioventricular block is characterized on ECG by:
  • A fixed, markedly prolonged PR interval with consistent 1:1 AV conduction
  • Complete electrical dissociation between P waves and QRS complexes, each firing at its own independent (atrial vs. ventricular/junctional escape) rate✔️
  • Progressively lengthening PR intervals before an occasional dropped beat
  • A completely normal ECG with only intermittent symptoms
Correct Answer Explanation
In complete heart block, no atrial impulses reach the ventricles, so atria and ventricles beat independently — the atrial (P wave) rate is faster and unrelated to the slower ventricular escape (QRS) rate, often requiring pacemaker implantation.