Despite favorable radial wall stress, percent systolic wall thickening was smaller at the hypertrophied myocardium (23.0%) than the nonhypertrophied myocardium (70.5%) in patients with HCM.
Observational (n=27)
Does hypertrophied myocardium in HCM have impaired contractile capability despite a globally hyperdynamic state when considering regional wall stress?
In HCM, the hypertrophied myocardium exhibits impaired contractility despite lower wall stress, and the globally hyperdynamic state (high fractional shortening) is primarily driven by a smaller end-diastolic dimension rather than true hypercontractility.
Absolute Event Rate: 23% vs 70.5%
In hypertrophic cardiomyopathy (HCM) a hyperkinetic state is sometimes observed in spite of impaired systolic function in the hypertrophied myocardium. The aim of the present study was to determine the mechanism of this paradox. Seventeen patients with HCM and 10 normal subjects underwent cine magnetic resonance (MR) imaging to measure percent systolic wall thickening and percent fractional shortening. The ratio of systolic radial wall stress of the LV at the hypertrophied myocardium over that at the nonhypertrophied myocardium was evaluated to describe the focal advantageous condition for wall thickening. The ratio was 0.66 +/- 0.36 at the start of contraction and 0.78 +/- 0.31 at early-systole, indicating consistently smaller radial wall stress at the hypertrophied myocardium. Although the condition for contraction was favorable (a ratio less than 1.00), percent systolic wall thickening at the hypertrophied myocardium (23.0 +/- 11.8%) was smaller than that at the nonhypertrophied myocardium (70.5 +/- 32.3%). Smaller end-diastolic dimension (HCM group; 45.2 +/- 4.2 mm, reference group; 48.9 +/- 4.1 mm, P = 0.04) with a statistically identical value of systolic decrease in intraventricular dimension (HCM group; 19.7 +/- 3.9 mm, reference group; 18.9 +/- 3.2 mm, P = 0.60) yielded high percent fractional shortening in patients with HCM (43.5 +/- 7.6%). Although contractile impairment was proven at the hypertrophied region with low radial wall stress in the HCM group, the smaller end-diastolic dimension in this group resulted in high percent fractional shortening.
Yamazaki et al. (2006) conducted an observational in Hypertrophic cardiomyopathy (n=27). Cine magnetic resonance imaging vs. Normal subjects / Nonhypertrophied myocardium was evaluated on Percent systolic wall thickening at hypertrophied vs nonhypertrophied myocardium. Despite favorable radial wall stress, percent systolic wall thickening was smaller at the hypertrophied myocardium (23.0%) than the nonhypertrophied myocardium (70.5%) in patients with HCM.