Background Resting left ventricular outflow tract obstruction (LVOTO) occurs in 25% of patients with hypertrophic cardiomyopathy (HCM) and is an important cause of symptoms and disease progression. The prevalence and clinical significance of exercise induced LVOTO in patients with symptomatic non-obstructive HCM is uncertain.
Methods & results 87 symptomatic patients (43.3 ± 13.7 years, 67.8% males) with HCM without previously documented LVOTO (defined as a gradient ≥ 30mmHg) underwent echocardiography during upright cardiopulmonary exercise testing: 54 (62.1%; 95% CI = 51.5, 71.6) patients developed LVOTO during exercise (latent LVOTO); 33 (37.9%; ; 95% CI = 28.4, 48.5) had neither resting nor exercise LVOTO (non-obstructive). Patients with latent LVOTO were more likely to have SAM at rest (relative risk 2.1, 95% CI=1.2, 3.8; p = 0.01), and higher peak oxygen consumption (mean difference: 10.3%, 95% CI = 2.1, 18.5; p = 0.02) than non-obstructive patients. The only independent predictors of Δ gradient during exercise were a history of presyncope/syncope, incomplete/complete SAM at rest and Wigle score (all p < 0.05). Subsequent invasive reduction of LVOTO in 10 patients with drug refractory symptoms resulted in improved functional class and less syncope/presyncope (all p < 0.05)
Conclusions Approximately two thirds of patients with symptomatic non-obstructive HCM have latent LVOTO. This study suggests that all patients with symptomatic non-obstructive HCM should have exercise stress echocardiography.
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