Microvascular dysfunction in nonfailing arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a nonischaemic cardiomyopathy and leading cause of sudden death in the young. It has been shown that microvascular dysfunction reflected by an impaired myocardial blood flow (MBF) response to stress is present in patients with other forms of nonischaemic cardiomyopathy, e.g. dilated cardiomyopathy, and that the reduced MBF may be related to a poor prognosis. Therefore, we quantified MBF, coronary flow reserve and coronary vascular resistance in patients with nonfailing ARVC using H ₂ ¹⁵ O and PET.

In ten male patients with ARVC (mean age 49 ± 14 years), MBF was quantified at rest and during adenosine-induced hyperaemia using H ₂ ¹⁵ O PET. Results were compared with those obtained in 20 age-matched healthy male control subjects (mean age 46 ± 14 years).

Resting MBF was not significantly different between patients with ARVC and controls (MBF_rest 1.19 ± 0.29 vs. 1.12 ± 0.20 ml/min/ml). However, hyperaemic MBF was significantly lower in patients with ARVC than in controls (2.60 ± 0.96 vs. 3.68 ± 0.84 ml/min/ml; p = 0.005). Consequently, patients with ARVC had a significantly lower coronary flow reserve than control subjects (2.41 ± 1.34 vs. 3.39 ± 0.93; p = 0.030). In addition, hyperaemic coronary vascular resistance was increased in patients with ARVC (36.79 ± 12.91 vs. 26.31 ± 6.49 mmHg × ml^-1 × min × ml; p = 0.007), but was found to be unchanged at rest.

In this small well-characterized cohort of patients with nonfailing ARVC, we found a significantly reduced hyperaemic MBF and increased coronary vascular resistance. Further studies are necessary to corroborate this potential new functional aspect of the pathophysiological mechanisms underlying ARVC.