16 yrs old..Holter monitor results.

I'm 16 and last week , I wore a holter monitor for 24 hours and was found to have frequent arrhythmias. He showed me on the ECG/paper where I had the arrhythmias and what I was was a few normal beats( normal sinus rhythm) and then I saw waves that lookes like repeated mountains or upside down W's but or rounded on the edges. By this description, was this V-tach? Echo was normal expect for mitral regurgitaion and stress test did not induce arrhythmia ( although I usually get arrhythmias during rest, not WHILE I'm running. ) I didn't tell the doctor that.
Also, while I was sleeping, my heart rate went down to 33. I am not athletic at all and may be considered a couch potato. I'm not overweight, though. I also have idiopathic hypertension.

The doctor now wants an MRI. His working diagnosis is arrhythmogenic w/ dysplasia. Is he referring to arrhythmogenic right ventricular dysplasia? Does the Holter monitor/computer tell them WHERE the arrhythmias came from? For example, left or right ventricle? I mean, why would he want to rule out ARVD?

[ed34]

Yes an ecg will show which ventricle/atria is affected. For example, an ecg can detect left bundle branch block or right bundle branch block. It can detect a-fib and all kinds of things.