Young patients with hypertrophic cardiomyopathy, but not subjects at risk, show decreased myocardial perfusion reserve quantified with CMR.

AIMS To determine if myocardial perfusion (MP) during hyperaemia is decreased in young patients with hypertrophic cardiomyopathy (HCM). Also, to determine if an MP decrease is associated with diastolic dysfunction, and to investigate if young subjects at risk of HCM show differences in MP compared with controls. METHODS AND RESULTS This study included 10 HCM patients (age 22.3 ± 6.4 years), 14 subjects at risk for HCM 'HCM risk' (age 18.9 ± 3.8 years), and 12 controls (age 22.8 ± 4.5 years). HCM patients were examined at rest and during hyperaemia (adenosine 140 µg/kg/min) with cardiovascular magnetic resonance (CMR) and echocardiography. MP was calculated as the ratio of coronary sinus flow and left ventricular mass (LVM) from CMR. Myocardial fibrosis was assessed using late gadolinium enhancement. Diastolic function was quantified with both echocardiography and CMR. At rest, MP (mL/min/g) was similar in the control, HCM risk, and HCM patients (0.8 ± 0.1, 1.0 ± 0.1, and 0.9 ± 0.1, respectively, P = ns). During adenosine, MP was lower in HCM patients (2.5 ± 0.4, P < 0.05) compared with both HCM risk (5.0 ± 0.5) and controls (3.9 ± 0.3). Subjects at HCM risk showed no significant difference in MP during adenosine compared with controls. One HCM patient showed mild diastolic dysfunction. Neither controls nor HCM risk individuals showed any sign of myocardial fibrosis, whereas 7/10 HCM patients had fibrosis (5 ± 1% of the total LVM). CONCLUSION Young individuals with HCM, but not those at risk, show decreased MP during hyperaemia compared with controls even in the absence of diastolic dysfunction or LV outflow obstruction. These results may suggest that microvascular disease contributes to the decreased MP in the investigated population.