Delayed Left Ventricular Untwisting in Hypertrophic Cardiomyopathy

Background

Almost all patients with hypertrophic cardiomyopathy (HCM) have some degree of left ventricular (LV) diastolic dysfunction. Nevertheless, the pathophysiology remains incompletely characterized. Conceptually, an ideal therapeutic agent should target the underlying mechanisms that cause LV diastolic dysfunction. Assessment of diastolic LV untwisting could potentially be helpful to gain insight into the mechanism of diastolic dysfunction. The purpose of this study was to investigate LV untwisting in patients with HCM and control subjects.

Methods

LV untwisting parameters were assessed using speckle-tracking echocardiography in 75 consecutive patients with HCM and compared with those from 75 healthy control subjects.

Results

Untwisting at 5%, 10%, and 15% of diastole was lower in patients with HCM (all P values < .001) compared with control subjects. Peak diastolic untwisting velocity (−92 ± 32°/s vs −104 ± 39°/s, P < .05) and untwisting rate from peak systolic twist to mitral valve opening (MVO) (−37 ± 20°/s vs −46 ± 22°/s, P < .01) were lower, while the for diastolic duration normalized time-to-peak diastolic untwisting velocity (17 ± 9% vs 13 ± 9%, P < .05) was higher in patients with HCM. Untwisting rate from peak systolic twist to MVO was negatively correlated with the E/A ratio (R² = 0.15, P < .01). Peak diastolic untwisting velocity and untwisting rate from peak systolic twist to MVO were increased in mild but decreased in moderate and severe diastolic dysfunction compared with control subjects.

Conclusion

LV untwisting is delayed in HCM, which probably significantly contributes to diastolic dysfunction.

Keywords: Hypertrophic cardiomyopathy, Pathophysiology, Diastolic dysfunction, Left ventricular untwisting, Speckle-tracking echocardiography