Exercise echocardiography in the evaluation of obstructive types of hypertrophic cardiomyopathy

OBJECTIVE: To assess the condition of left ventricular outflow tract obstruction (LVOTO) under resting conditions and physiological exercise in hypertrophic cardiomyopathy (HCM) patients. METHODS: A total of 60 patients with HCM and left ventricular outflow tract gradient (LVOTG) <50 mm Hg (1 mm Hg = 0.133 kPa) at rest were enrolled consecutively, and LVOTG at rest and exercise were measured by echocardiography. Of 51 patients with gradients <30 mm Hg at rest, 26 were latent LVOTO with exercise peak value LVOTG ≥ 30 mm Hg, 25 were non LVOTO with exercise peak value LVOTG < 30 mm Hg, and 9 were resting obstruction with LVOTG 30-49 mm Hg. The morphological characteristics of different types of obstruction were analyzed. RESULTS: Patients with latent LVOTO were more likely to have SAM (73.1% vs 8.0%) , narrow of LVOT (46.2% vs 4.0%) , higher resting gradients [(16.9 ± 7.2) mm Hg vs (7.1 ± 4.3) mm Hg] and mitral regurgitation grade at rest than patients with non-obstructive (all P values <0.05). The distribution of septal hypertrophy were different in the two groups (P < 0.05). Multivariate logistic regression analysis showed independent predictors of latent LVOTO were SAM (OR 6.431, 95%CI 2.323-291.112, P = 0.002) at rest and distribution of septal hypertrophy(OR 0.011, 95% CI 0.001-0.179, P = 0.008). CONCLUSIONS: Approximately half of patients with non-obstructive HCM at rest have latent LVOTO. SAM and distribution of septal hypertrophy may be useful to identify patients with latent obstruction.