Prevalence of Myocardial Bridging in Patients with Hypertrophic Cardiomyopathy: A Coronary Computed Tomography Study

Gideon Shafir Mithal Nassar 2 Daniel Monakier 2 Ziad Arow 2 Ran Kornowski 2 Ashraf Hamdan 2
1Radiology Department, Rabin Medical Center, Israel
2Cardiology, Rabin Medical Center, Israel

BACKGROUND: Reported prevalence of coronary artery bridges (CBs) in patients with hypertrophic cardiomyopathy (HCM) varies between 15% and 55% in autopsy and in invasive coronary angiography, their prevalence has never been reported using computed tompgraphy (CT).
OBJECTIVES: The objective of this study was to evaluate the frequency and pattern of CBs as assessed by CT in patients with HCM and to evaluate their possible association with non sustained ventricular tachycardia (NSVT).
METHODS: The study population consisted of 85 patients with HCM (56.4 ± 12.4 years; 77% male), and 79 aged and sex matched normal subjects (52.8 ± 12.5 years; 77% male), who were referred for coronary CT angiography. The following parameters were measured: number, length, and depth of CBs within left ventricular (LV) myocardium; and their course in relation to the left and right ventricular and atrial myocardium. The association between CBs and NSVT was evaluated using Fischer's exact test.
RESULTS: Myocardial bridges were more common in HCM than in normal subjects (59/85; 69% vs. 26/79; 33%; retrospectively, P < 0.001). As compared with normal subjects CBs in HCM patients were longer (25.3 ± 13.1mm vs. 18.5 ± 14.9mm; P = 0.045) and deeper within LV myocardium (2.9 ± 1.7mm vs. 1.6 ± 1.1mm; P = 0.001). No difference was evident between HCM with or without CBs in regard to LV mass (238 ± 88g vs. 235 ± 88g; retrospectively, P = 0.92) or coronary blood volume (6.95 ± 2.1ml vs. 7.12 ± 1.8ml; retrospectively, P = 0.96). In a subgroup of 38 patients with HCM the prevalence of CBs was similar in patients with and without NSVT (16/38; 42% vs. 22/38; 58% retrospectively; P = 0.67).
CONCLUSION: The frequency of myocardial bridging in patients with HCM observed by coronary CT angiography was 69%, higher than in angiographic and pathologic series, but was not associated with increased risk of NSVT. The number, length, depth, and course of CBs differ between patients with HCM and normal subjects.

Gideon  Shafir
Gideon Shafir