7-year-old presents to ER with recurrent SVT

Case

Sorry to bother you, I’m calling from the emergency room at Blank Regional Hospital, we’re about 90 miles from your institution. We had a 7-year old female who has a history of supraventricular tachycardia (SVT) that presented with breakthrough tachycardia today at 220 bpm. I tried having her blow through an occluded straw and she was unable to break the tachycardia- this usually works for her. I was able to obtain an ECG and I am sending that to you now. I was going to give her adenosine 6 mg IV but the tachycardia broke as we were getting an IV. The reason I am calling you is that this is her fourth visit to the ER for this SVT. She was seen by a local adult cardiologist who had put her on a calcium channel blocker after her second visit, but it really hasn’t worked. According to the mother, she is having breakthrough episodes nearly every day at school and they self-resolve after sitting in the nurse’s office for about 30 minutes. They were told that anything longer she should seek medical attention. Her dose on the calcium channel blocker is pretty good for her weight and she has had some significant constipation issues with it. I’m wondering if I should try a different medication or have her come see you?