Prognostic Value of Coronary Artery Blood Volume to Myocardial Mass Mismatch in Patients with Hypertrophic Cardiomyopathy

Background: In patients with hypertrophic cardiomyopathy (HCM) a mismatch between increased left ventricular mass (LVM) and blood supply may create an ischemic substrate conducive to non-sustained ventricular tachycardia (NSVT), and may provoke myocardial fibrosis. This mismatch may offer new insights for future clinical risk stratification in patients with HCM.

Objectives: We investigated whether the ratio of epicardial coronary blood volume (CBV) to left ventricular mass (LVM), determined by computed tomography (CT), correlate with NSVT and late gadolinium enhancement (LGE), determine by magnetic resonance imaging (MRI), in patients with HCM.

Methods: Forty four patients with HCM (mean age 57 ± 12) and 5 normal subjects (mean age 45 ± 12) underwent contrast enhanced ECG-gated CT. The clinical data of the studied cohort were obtained from chart review. Myocardial fibrosis was assessed in 10 patients with HCM and 5 normal subjects referred for magnetic resonance imaging (MRI). In 44 with HCM the entire epicardial coronary tree was detected to calculate CBV, LVM was calculated, and the CBV/LVM ratio was evaluated for its correlation with NSVT and myocardial fibrosis.

Results: In patients with HCM, CBV index and LVM index was significantly higher; however, CBV/LVM ratio was significantly lower compared to normal subjects. NSVT occurred in 25% of patients. In patients with NSVT, CBV index and LVM index tended to be higher (CBV index: 3.7 ± 0.9 ml/m² vs. 3.4 ± 0.9 ml/m², retrospectively, P = 0.32; LVM index: 129 ± 33 g/m² vs. 111 ± 33 g/m² respectively, P = 0.10); however, CBV/LVM ratio was lower (0.029 ± 0.004 ml/g vs. 0.033 ± 0.007 ml/g; P = 0.051) compared to patients without NSVT. CBV/LVM ratio tended to correlate inversely with myocardial fibrosis (r = - 0.45, P = 0.08) in patients with HCM.

Conclusion: This ongoing study demonstrates that quantification of muscle mass, its vascular supply, and the ratio of both may be important components of the risk attributable to HCM. CBV/LVM ratio, as demonstrated by contrast CT, may be an important factor contributing to myocardial fibrosis and NSVT in patients with HCM.