Hypertrophic cardiomyopathy is associated with more severe dipyridamole-induced left ventricular systolic dysfunction and mechanical dyssynchrony: a cardiac CZT study

Objectives Chest pain and myocardial ischemia are common features in patients with hypertrophic cardiomyopathy (HCM). Recently introduced SPECT cameras with solid-state cadmium-zinc-telluride (CZT) detectors have been shown to decrease imaging time and improved the imaging quality of gated myocardial perfusion imaging (MPI). This study is to examine the spatial distribution of stress perfusion abnormalities and tissue injury in patients with HCM using a CZT SPECT camera.

Methods We retrospectively evaluated myocardial perfusion patterns and cardiac function with Tl-201 gated dipyridamole MPI in patients with clinical diagnosis of HCM and patent coronary angiography between January 2013 and June 2015. The inclusion criteria included a spade-like configuration on left ventriculogram or echocardiographic findings suggestive of HCM. The patients were divided into the following 3 groups: apical, concentric and septal forms. Regional perfusion were analyzed using a 17 segment model from 0-4 degree (0=normal, to 4=absent perfusion); and summed stress score (SSS), summed rest score (SRS) and summed difference score (SDS) were calculated. Gated SPECT was processed by QGS software (Cedars-Sinai Medical Center, Los Angeles, CA, USA), left ventricular volume, and ejection fraction phase analysis.

Results A total of 40 patients were included for analysis, and classified as apical form in 5 patients, septal form in 14 and concentric form in 21. The myocardial ischemia was not uncommon with mean SSS was 5.30±5.40, but no significant difference of SSS, SRS, or SDS in different groups. Although LVEF at post-stress and rest were similar between groups, transient deterioration of LVEF after stress was common in apical form. On the other hand, the phase analysis showed significantly higher post-stress skewness and kurtosis in concentric form and lowest in the apical form; however, not significantly different between groups at rest state.

Conclusions Even with patent coronary arteries, mild ischemia is common in patients with HCM. The transient stress-induced LV systolic dysfunction and left ventricular mechanical dyssynchrony are both prominently seen in apical forma. Despite the limitation of nuclear MPI in the diagnosis of epicardial coronary stenosis due to prevalent microvascular dysfunction, gated MPI could provide detailed information on cardiac function, myocardial perfusion, tissue injury, and is a valuable method for exploring the inter-relationship between the morphological, pathophysiological and functional changes in HCM. Table. Characteristics according to types of HCM