Symptomatic First-degree AV Block — EECC MCQ

Correct answer: E — Pacing is generally NOT indicated for isolated first-degree AV block, even if markedly prolonged; however, if symptoms are clearly attributable to the long PR interval (atrial contraction against a closed mitral valve causing 'pacemaker syndrome'-like symptoms), pacing may be considered

Isolated first-degree AV block (PR >200 ms) is generally benign and does NOT require pacing. However, markedly prolonged PR intervals (>300 ms) can occasionally cause symptoms similar to 'pacemaker syndrome' — because the P wave occurs so early that atrial contraction occurs against a closed mitral valve (during ventricular systole), causing: cannon A waves, reduced diastolic filling time, reduced cardiac output, and symptoms (dyspnoea, exercise intolerance, presyncope). The 2021 ESC Pacing Guidelines state: (1) pacing is generally not indicated for first-degree AV block (Class III); (2) pacing may be considered (Class IIb) when symptoms are clearly attributable to the long PR interval, confirmed by improvement with temporary AV-sequential pacing. Investigation should exclude other causes of syncope before attributing symptoms to first-degree AV block.

Reference: ESC (2021): Pacing Guidelines