Systolic myocardial mechanics in hypertrophic cardiomyopathy: novel concepts and implications for clinical status.

In hypertrophic cardiomyopathy (HCM), malfunctioning sarcomeric protein, myocyte hypertrophy, fiber disarray, and interstitial fibrosis interfere with systolic myocardial mechanics despite clinically hyperdynamic systolic function. We evaluated local left ventricular (LV) mechanics in 72 patients with HCM and 32 control subjects using 2-dimensional velocity vector imaging. Patients had higher circumferential strain (-34 +/- 9 vs -29 +/- 8, P < .05) and lower longitudinal strain (-16 +/- 4 vs -21 +/- 4, P < .05) compared with control subjects. Biplanar strain vector magnitude was similar (-38% +/- 8 vs -36 +/- 7) in both groups, but was circumferentially oriented in HCM (27 +/- 10 vs 39 +/- 9 degrees, P < .05). Mid LV rotation was clockwise (opposite to normal). LV outflow tract obstruction and clinical status were related to more circumferentially directed strain and reduced apical biplanar strain. Patients with HCM have more circumferential myocardial strain and apically displaced systolic twist. Functional status and LV outflow tract obstruction were related to decreased strain vector angle and apical mechanics. These findings provide insights into the pathophysiology of HCM.