Strain analysis during exercise in patients with left ventricular hypertrophy: impact of etiology
Résumé
BACKGROUND: Hypertrophic cardiomyopathy (HCM) and aortic stenosis (AS) may influence left ventricular (LV) systolic function, despite preservation of LV ejection fraction. The aim of this study was to determine the relative importance of cardiac afterload and myocardial hypertrophy in the potential dysfunction of myocardial deformation, at rest and during standardized exercise. METHODS: Patients with moderate to severe (≤ 1.5 cm(2)) asymptomatic AS and patients with HCM in sinus rhythm were prospectively studied using resting and exercise echocardiography during submaximal exercise. Myocardial deformations were assessed using two-dimensional strain. Exclusion criteria were altered LV ejection fraction (\textless50%), coronary artery disease, intra-LV obstruction \textgreater 30 mm Hg at rest, diastolic LV thickness ≥ 30 mm, and New York Heart Association class \textgreater II. Thus, 50 patients (25 with AS, 25 with HCM) were selected and matched for age, sex, rest and exercise blood pressure, degree of LV hypertrophy (defined by maximal wall thickness), and LV ejection fraction. RESULTS: Mean resting global longitudinal strain (GLS) was -14.9 ± 4.7% in patients with AS and -16.1 ± 3.9% in those with HCM (P = .30). During exercise (mean heart rate, 110 ± 10 beats/min), mean GLS was -13.9 ± 4.2% in patients with AS and -18.1 ± 5.4% in those with HCM (P = .004). GLS decreased in patients with AS but increased in those with HCM (ΔGLS, 0.9 ± 3.1% and -1.9 ± 3.2%, respectively, P = .003). The same results were observed for global circumferential strain. Mean resting global circumferential strain was -16.4 ± 5.8% in patients with AS and -17.9 ± 4.5% in those with HCM (P = .36). During exercise, mean global circumferential strain was -13.8 ± 4.1% in patients with AS and -18.6 ± 5.3% in those with HCM (P = .011). Afterload was higher, particularly during exercise, in patients with AS than in those with HCM. CONCLUSIONS: Longitudinal and circumferential LV deformation during exercise was lower in patients with AS compared with those with HCM, despite similar resting characteristics. The greater afterload observed in patients with AS led to reduced contractile reserve.