Everolimus is a mTOR inhibitor that has been increasingly used in high-risk cardiac rhabdomyomas in recent years. There are questions regarding the optimal dose and duration of therapy with everolimus for cardiac rhabdomyomas. The purpose of this study was to examine retrospectively the dosage-efficacy relationship in seven babies diagnosed with rhabdomyoma treated with different everolimus dose regimens retrospectively. Cardiac rhabdomyoma diagnosis was made in six of seven babies during the prenatal period. Indication of everolimus was an obstruction in six patients and supraventricular tachycardia which is resistant to antiarrhythmic drugs in the remaining one patient. The median age was 8 days (range; 2–105 days) at the time of starting everolimus. It was administered at a dose of 0.25 mg twice a day for two days a week in four patients; 0.1 mg/day in two and 0.4 mg/day in one patient. Serum everolimus level was kept between 5 and 15 ng/ml. All seven cases showed significant regression of cardiac rhabdomyoma within four weeks, and supraventricular tachycardia was controlled in two weeks after everolimus administration.

This study demonstrates that everolimus was effective in accelerating regression of the cardiac rhabdomyoma. Dose with 2 × 0,25 mg/day, 2 days a week, seems appropriate. However, lower doses such as 0.1 mg/day are also effective. But dose adjustment should be made according to serum level monitoring.