People who exercise more than 3 hours a week could be at risk of a terrifying misdiagnosis
This happened to me, for about 10 minutes, during the mid 1990s.
I had an upper respiratory/sinus infection, went to the doctor and was prescribed an antibiotic. Later that day while driving home from the office Christmas party, I had a series of tachycardia episodes. My heart rate would hit 140 - 160. I likened it to the experience one gets from leaning back in a chair, and the racing heart went the chair breaks backwards. The difference was this lasted for an hour or more each time. Disturbing to say the least.
It was so disturbing I went in to the ER that night. I looked gray, and felt puny. The doc was initially clueless, and so hooked me up to the christmas tree, and took some electrical tests, and did some imaging if I remember correctly.
When the doctor came back his demeanor was priceless. He was very gentle, and told me I had a seriously enlarged heart, specifically the left ventricle, and . . . it was all worry about how I had a serious heart ailment, or some foolishness. I should have been terrified, but really, this was not a possible medical problem, he just did't realize it. So, I asked him a few questions (ok, as did medical professional Maddogswif), about whether I would have shortness of breath, difficulty with stairs, low energy, problems ambulating, and more. He kindly agreed to each and every one.
Then I told him I was lifting for 45 minutes to an hour 5 days per week, including bench pressing 450 lbs. weekly, 1 -1/2 hours per day 5 days per week, on the stair machine, burning in excess of 1200 calories, waterskiing 100 day each summer, snow skiing 40 days each winter, mountain biking fall, and spring, and sea kayak expedition for 2 weeks to a month each year. I left out the other activities.
He looked a bit startled. So, I said, "450 lbs. weekly." Then he brightened, and said, never mind, you exercise so much you have a normally huge heart, shook my hand and left. The doc actually said he had never seen anything like it. Heh.
We decided I had vertigo without visual disturbance from the sinus infection, and he thought the tachycardia would resolve within a day or so as the antibiotics began to act. He was right.