Unmasking Latent Left Ventricular Outflow Tract Obstruction in Hypertrophic Cardiomyopathy: Invasive and Noninvasive Assessment.

BACKGROUND: Dynamic left ventricular outflow tract (LVOT) obstruction in hypertrophic cardiomyopathy may be missed on resting echocardiography, and it requires provocation for detection. CASE SUMMARY: A 41-year-old man with previously classified nonobstructive hypertrophic cardiomyopathy presented with recurrent syncope. Serial echocardiography had demonstrated no significant dynamic LVOT obstruction. During reassessment, repeated Doppler interrogation with Valsalva maneuver revealed variable pressure gradients ranging from 25 to 46 mm Hg. Exercise stress echocardiography further unmasked severe LVOT obstruction, with a peak gradient of 108 mm Hg and worsening mitral regurgitation. Multimodality assessment, including postextrasystolic provocation and invasive hemodynamics, demonstrated comparable augmentation of LVOT gradients. Mavacamten therapy eliminated LVOT obstruction, with no recurrence of syncope. DISCUSSION: Exercise-induced gradients paralleled those obtained with mechanistic provocation, indicating that physiologic stress can reliably reflect the magnitude of latent obstruction. TAKE-HOME MESSAGE: Exercise stress echocardiography, supported by complementary provocation, may provide a practical approach to identify clinically significant latent LVOT obstruction.