Exercise response in hypertrophic cardiomyopathy: blunted left ventricular deformational and twisting reserve with altered systolic-diastolic coupling.

Background: Abnormal left ventricular (LV) deformational mechanics have been demonstrated in patients with hypertrophic cardiomyopathy (HCM) at rest, but there is a lack of information on their adaptation to exercise. The aim of this study was to assess the adaptability of LV strains and torsional mechanics during exercise in HCM patients.

Methods And Results: Twenty nonobstructive HCM patients (age, 48.3±12.3 years; 14 men) and 20 control subjects underwent speckle-tracking echocardiographic measurement of longitudinal, radial, and circumferential strains, systolic twist, and diastolic untwisting rate (UTR) at rest and submaximal exercise. HCM patients showed lower resting longitudinal (-15.7±5.0% versus -19.4±2.6%, P<0.001) and radial (38.1±11.3% versus 44.7±14.4%, P<0.05) strains but higher circumferential strain (-21.9±4.0% versus -18.8±2.3%, P<0.05) and twist (15.7±3.6° versus 9.3±2.6°, P<0.0001) than control subjects. Exercise induced an increase in all strains in control subjects but only a moderate increase in longitudinal strain (to -18.4±5.0%), without significant changes in radial and circumferential strains or twist in HCM patients. Exercise peak UTR was lower (-119.0±31.5°/s versus -137.3±41.1°/s) and occurred later (137±18% versus 125±11% systolic time, P<0.05) in HCM than in control subjects. A significant relationship between twist and UTR was obtained in control subjects (ß=-0.0807, P<0.001) but not in HCM patients (ß=-0.0051, P=0.68).

Conclusions: HCM patients had severely limited strain adaptability and no LV twisting reserve at exercise. They had reduced and delayed UTR with reduced systolic-diastolic coupling efficiency by twist-untwist mechanics.