BACKGROUND

Although patients with hypertrophic cardiomyopathy (HCM) have normal ejection fractions at rest, the investigators hypothesized that these patients have differentially abnormal systolic function reserves, limiting their exercise capacity compared with patients with hypertension (HTN).

METHODS

Forty patients with HCM (mean age, 39.1 ± 12 years), 20 patients with HTN with LVH, and 33 healthy individuals underwent resting and peak exercise echocardiography using two-dimensional strain imaging. Peak longitudinal systolic strain (εsys) and strain rate were measured in apical views. Circumferential εsys and left ventricular (LV) twist were analyzed from short-axis views. LV systolic dyssynchrony was measured from regional longitudinal strain curves as the standard deviation of time to peak strain (time from the beginning of the Q wave on electrocardiography to peak εsys) between 12 segments. The differences between resting and peak exercise values were analyzed, and functional reserve was calculated as the difference divided by the resting value.

RESULTS

In patients with HCM, resting values for longitudinal εsys, systolic strain rate, early diastolic strain rate, and atrial diastolic strain rate were significantly lower, while circumferential εsys and twist were higher, compared with patients with HTN and controls (P < .0001). Functional systolic reserve increased during exercise in controls (17 ± 6%), increased to a lesser extent in patients with HTN (10 ± 16%), and was markedly attenuated in patients with HCM (-23 ± 28%) (P < .001). At peak exercise, even with augmented circumferential εsys and twist in patients with HCM (P < .01) compared with those with HTN, both remained lower than in controls (P < .001). LV dyssynchrony was amplified during exercise in patients with HCM compared with those with HTN (P < .001). Within the entire population, exercise capacity was clearly correlated with systolic functional reserve. However when taken separately, it was mainly related to resting LV dyssynchrony and diastolic function in patients with HCM, whereas it was linked to age and LV wall thickness in those with HTN.

CONCLUSIONS

Patients with HCM have significantly limited systolic function reserve and more dynamic dyssynchrony with exercise compared with those with HTN. Two-dimensional strain imaging during stress may provide a new and reliable method to identify patients at higher cardiovascular risk.