The role of impaired sympathetic nerve function in enhancing coronary vasoconstriction in patients with hypertrophic cardiomyopathy

Abstract

Coronary vasospasm and diminished coronary blood flow reserve have often been reported in patients with hypertrophic cardiomyopathy (HCM). However, the mechanism of coronary spasm in HCM is unknown. Thus, coronary endothelial function and sympathetic nerve function in 11 patients with HCM and 11 control patients matched for age and sex were examined. The diameter of the left anterior descending coronary artery was assessed by quantitative coronary angiography, and the change in coronary blood flow was estimated using an intracoronary Doppler flow wire. To assess myocardial sympathetic nerve function, metaiodobenzylguanidine images - 15 min and 180 min after the injection of (123)I-metaiodoben-zylguanidine at a dosage of 111 MBq - were obtained, and the heart to mediastinum (H/M) count ratio and the washout rate (WR) were calculated. The H/M ratio was significantly lower in patients with HCM (2.1+/-0.3) than in control patients (2.6+/-0.4) (P<0.01). In addition, the WR was higher in patients with HCM (35+/-6%) than in control patients (28+/-3%) (P<0.01). The HCM subjects with coronary spasm had lower H/M ratios and higher WRs than HCM subjects without coronary spasm (P<0.05, respectively). In conclusion, impaired sympathetic nerve function may be associated with coronary vasospasm and diminished coronary blood flow reserve in HCM.

Keywords: Hypertrophic cardiomyopathy; Metaiodobenzylguanidine.

Figure 1

Anterior planar images were obtained 15 min and 3 h after intravenous injection of ¹²³I-metaiodobenzylguanidine. Cardiac uptake of ¹²³I-metaiodobenzylguanidine was measured as heart to mediastinum (H/M) count ratio, using regions of interest positioned over H and upper M

Figure 2

Coronary angiography of a 71-year-old man with hypertrophic cardiomyopathy. Coronary spasm was provoked by the infusion of acetylcholine (ACh). Coronary vasospasm was observed in the proximal left anterior descending coronary artery (#6) and diagonal branch (#9). Left coronary artery from the right anterior oblique view

Figure 3

Resting ¹²³I-metaiodobenzylguanidine anterior planar images in a 71-year-old man with hypertrophic cardiomyopathy. Top Early image (15 min) showing regions of interest for the heart (round outline, number 1), mediastinum (square outline, number 2) and lung (square outline, number 3). Bottom Delayed image (3 h)

Figure 4

Comparison of ¹²³I-metaiodobenzylguanidine parameters (heart [H] to mediastinum [M] ratio and washout rate [WR]) between hypertrophic cardiomyopathy (HCM) subjects and control (C) subjects. Values are mean ± SD

Figure 5

Comparison in ¹²³I-metaiodobenzylguanidine parameters (heart to mediastinum [H/M] ratio and washout rate [WR]) between hypertrophic cardiomyopathy subjects with spasm (Spasm [+]) and hypertrophic cardiomyopathy subjects without spasm (Spasm [–]). Values are mean ± SD