Supra Ventricular Tachycardia

Four months ago while exercising I experienced tachycardia of 180-190 bpm that lasted for 50 minutes after I stopped. Needless to say it distressed me. I have had maybe 2-3 incidents before in the past years but none that lasted more than 20 seconds. It happened 3 times in 1 week the day before my annual check up with my medical system P.A.. He sent me to a cardiac P.A. who signed me up for a Holter monitor and after 2 days it showed nothing unusual. I was told that without an EKG that there was nothing they could do. Two days later another tachycardia event and no monitor so I bought a KardiaMobile to record the events and sent the first EKG to the P.A. and she prescribed Metopro1ol and I explained that I had a bad experience with beta blockers. She old me that I needed to try it first and see if it resolved my tachycardia which it did. I had no further instances of tachycardia or palpitations but all the side effects I had years ago came back. I was so lethargic I could not exercise and spent most of my days sitting on the couch. asked if she could lower the dosage. No, 25 mg a day was the minimum dosage but I could try DILTIAZEM which is a calcium blocker and if I had problems with it ablation was the only alternative. The calcium blocker altered my sense of taste which the P.A. said was not listed as a possible side effect. After 30 days the tachycardia is returning. The P.A. says there is no choice but ablation and I'm scheduled for a consultation in 2 1/2 months.

I was a mechanical engineer and was always taught to question the data by duplicating the data collection and verifying. This time there is no testing just following the assumed protocol and referral to another doctor if it doesn't work. My thyroid level is low but within the normal rang are there no tests that could uncover any other causes of tachycardia BEFORE I have ablation?