<<Sunday around noon my heart rate shot up to nearly 170 BPM I wasn't doing anything physical just fussing around in the garage on part of a resto project on my house.>>

Was it tachycardia or atrial fibrillation (afib)? The first time I had afib many years ago, my HR went to 210+, but was irregular. I went to the ER as I didn't know what was happening. After about 24 hours I was back to normal. Since then, about 17 years ago, I've been treated with medication and finally a cardiac ablation, which has almost cured it. I still get bouts, but they only last up to 36 hours and my HR only goes to about 90 (resting is around 42). When I'm riding hard, my HR will sometimes jump from a steady 140 to over 200. If I slow down, it soon goes back to normal and, most importantly, according to my cardiologist, I don't feel faint or have any pain. He won't use beta-blockers on me a)because I'm asthmatic and b)because I alread have a low resting HR (bradycardia) which might be lowered to a dangerous level.