Background Hypertrophic cardiomyopathy (HCM) is often associated with reduced exercise capacity. We sought to examine the importance of left ventricular strain, twist and untwist rates as predictors of exercise capacity in HCM patients.
Method 56 HCM patients (31 men, mean age 52 years) and 43 age and gender-matched controls were enrolled. We measured peak oxygen consumption and acquired standard echocardiographic images in all participants. Two-dimensional speckle tracking was applied to measure twist and untwist rates (fig) and longitudinal, radial and circumferential strain and strain rates.
Results HCM patients exhibited marked exercise limitation compared with controls (peak oxygen consumption 23.28 ± 6.31 ml/kg per minute vs 37.70 ± 7.99 ml/kg per minute, p<0.0001). The left ventricular ejection fraction (LVEF) in HCM patients and controls was similar (62.76 ± 9.05% vs 62.48 ± 5.82%, p = 0.86). Longitudinal, radial and circumferential strain and strain rate were all significantly reduced in HCM patients compared with controls. There was no significant difference in left ventricular twist and torsion between HCM patients and controls; however, there was a significant delay in 25% of the untwist and late untwist rate in HCM patients compared with controls. Using multiple stepwise regression analysis, both systolic twist rate and longitudinal systolic strain were independent predictors of exercise capacity (r = 0.5, p = 0.001, r = 0.4, p = 0.002, respectively)
Conclusion Despite normal LVEF, left ventricular strain and strain rate were significantly reduced in HCM patients compared with controls. The systolic twist rate and longitudinal systolic strain were major determinants of exercise capacity.