Microvascular dysfunction in hypertrophic cardiomyopathy has been associated with poor clinical outcome. Several studies have demonstrated a reduced perfusion reserve proportional to the magnitude of the hypertrophy. We investigated the utility of stress perfusion cardiac MRI to detect microvascular dysfunction in children with hypertrophic cardiomyopathy.

From January 2016 to January 2017, 13 patients, with a mean age of 15.3 years, with hypertrophic cardiomyopathy underwent regadenoson stress perfusion cardiac MRI (1.5-T Siemens Aera). A single-shot, T1-weighted saturation recovery gradient echo was used for first-pass perfusion in a multiple-slices group, including three short-axis slices and one four-chamber slice. Coronary vasodilatory stress was achieved using bolus injection of regadenoson (lexiscan 0.4 mg/5 ml) and dynamic perfusion during rest and stress performed by administering 0.05 mmol/kg of gadolinium contrast agent (gadoteridol) injected at a rate of 3.5 ml/s, followed by assessment of viability using two-dimensional phase-sensitive inversion recovery of the entire myocardium.

All patients completed protocols with no interruptions. In all, seven patients developed perfusion defects after the administration of regadenoson. Asymmetric septal hypertrophy was the most common pattern of hypertrophic cardiomyopathy (n=4) in those with abnormal perfusion. A total of four patients with perfusion defects had a maximum wall thickness <30 mm. The finding of perfusion defects in areas without late gadolinium enhancement in some of our patients indicates that gadolinium enhancement by itself could underestimate the true extension of microvascular disease. Out of seven patients, five patients with positive stress cardiac MRI have undergone implantable cardioverter defibrillator placement based on current guidelines.

Regadenoson stress cardiac MRI is feasible and clinically valuable in paediatric patients. It is particularly effective in unmasking abnormal myocardial perfusion in the presence of microvascular dysfunction in children with hypertrophic cardiomyopathy.