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Exercise CMR in HCM — EECC MCQ

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HardCardiac ImagingExercise CMR in HCMEECC

A 62-year-old man with HCM undergoes exercise CMR. His resting LVEF is 68% but during exercise, LVEF paradoxically decreases to 55% and the LVOT gradient increases from 30 to 95 mmHg. What does this exercise response indicate?

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Correct answer: D — Exercise-induced LVOT obstruction with impaired LV systolic reserve — the dynamic obstruction worsens with exercise (reduced LV volume + increased contractility + decreased SVR), and the apparent LVEF drop reflects the haemodynamic burden rather than myocardial dysfunction

Exercise CMR is an emerging modality for HCM assessment. In obstructive HCM, exercise worsens LVOT obstruction through: (1) reduced LV end-diastolic volume (decreased preload from exercise-induced vasodilatation and shortened diastole); (2) increased contractility (catecholamines); (3) decreased afterload (peripheral vasodilatation). The paradoxical LVEF decrease reflects: (1) the ventricle ejecting against the dynamic obstruction (wasted pressure work); (2) SAM-mediated MR diverting flow to the LA; (3) impaired LV filling. Provocable LVOT gradients ≥50 mmHg during exercise are clinically significant and may trigger intervention (beta-blocker optimisation, mavacamten, septal myectomy, or ASA). The 2023 ESC Cardiomyopathy Guidelines recommend exercise provocative testing (echo or CMR) to detect latent obstruction when resting gradients are <50 mmHg.

Reference: ESC (2023): Cardiomyopathies Guidelines