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CRT Response Predictors — EECC MCQ

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ModerateHeart FailureCRT Response PredictorsEECC

A 58-year-old man with HFrEF (LVEF 20%) and LBBB (QRS 155 ms) undergoes CRT-D. What QRS morphology and duration are associated with the greatest CRT response?

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Correct answer: C — True LBBB morphology with QRS ≥150 ms — this combination predicts the best response to CRT, with the strongest evidence for mortality reduction (Class I, LOE A)

CRT response is strongly predicted by QRS morphology and duration. The ESC 2021 Pacing/CRT Guidelines stratify: (1) LBBB + QRS ≥150 ms = strongest indication (Class I, LOE A) — ~70% response rate; (2) LBBB + QRS 130-149 ms = Class I, LOE B; (3) non-LBBB + QRS ≥150 ms = Class IIa — response rates lower (~40%); (4) non-LBBB + QRS 130-149 ms = Class IIb — limited evidence. True LBBB (defined by Strauss criteria: QRS ≥140 ms men/≥130 ms women, mid-QRS notching in ≥2 of V1/V2/V5/V6/I/aVL) represents electrical dyssynchrony that CRT can correct. RBBB indicates RV conduction delay, which LV pacing does not address — CRT evidence in RBBB is weak.

Reference: ESC (2021): Guidelines on Cardiac Pacing and CRT