Tissue doppler-derived indices predict exercise capacity in patients with apical hypertrophic cardiomyopathy

Background: Although impaired left ventricular (LV) diastolic function is a prominent feature of hypertrophic cardiomyopathy (HCM), diastolic function and its relation to exercise capacity in apical HCM (ApHCM) has not been explored previously. This study was sought to determine the relationship between diastolic mitral annular velocities combined with conventional Doppler indexes and exercise capacity in patients with ApHCM. Patients: Twenty-nine patients with ApHCM (24 men; mean age ± SD, 57 ± 10 years) underwent supine bicycle exercise with simultaneous respiratory gas analysis and two-dimensional and Doppler echocardiographic study. Results: The mitral inflow velocities (early filling [E], late filling, and deceleration time) were traced and measured. Early diastolic mitral annular velocity (E') was measured at the septal corner of mitral annulus by Doppler tissue imaging (DTI) from the apical four-chamber view. Pro-brain natriuretic peptide (proBNP) was measured at the time of echocardiography using a quantitative electrochemiluminescence immunoassay. E/E' ratio correlated inversely with maximal oxygen uptake (V̇O₂max) [r = - 0.47, p = 0.0106]. There was a significant positive correlation between E' and V̇O₂max (r = 0.41, p = 0.024). However, no correlation was found between conventional two-dimensional, Doppler indices, and proBNP and V̇O₂max). Of all the echocardiographic and clinical parameters assessed, E/E' ratio had the best correlation with exercise capacity (r - 0.47) and was the strongest independent predictor of V̇O₂max by multivariate analysis (p = 0.0106). Conclusions: DTI-derived indexes (E', E/E' ratio), an estimate of myocardial relaxation and LV filling pressures, correlate with exercise capacity in patients with ApHCM, suggesting that abnormal diastolic function may be a factor limiting exercise capacity.