How strong is one's exercise tolerance as an indicator of one's overall cardiac health? I've heard a few different opinions on this matter and wondered what your thoughts are.
For example, I work out daily for 45 - 60 mins at 80% - 85% of my max predicted heart rate. I am able to do so with no issues and have a high tolerance for exercise, so I can easily push to 100% of my max. I am a 52 year old man and have recently had a clean echo and nuclear stress test (within 3 years) and have no other real risk factors other than my BP is controlled with medication. Cholesterol is good, no family history and never smoked, still a little overweight by 40 pounds after losing 80.
How possible is it for someone with a good exercise tolerance to have an underlying Cardiomyopathy or CAD?
Patients who perform at a high level of exercise for age (such as your level) have a very good prognosis with a low chance of heart disease. Heart disease, however, is a combination of many factors, some that can be controlled and others that cannot. Controllable ones include diet, exercise, blood pressure, cholesterol and tobacco use. Others that cannot be controlled include family history. While it is possible to have some underlying disease, it appears that you have given yourself an excellent chance at reducing any possible coronary disease to the lowest level possible. Keep up the good work!
The doctor will answer, but I may share some thoughts.
I think the clean echo will rule out almost any heart muscle disease (cardiomyopathy). If you know your end-diastolic volume and your EF, and this is within normal limits, and the cardiologist didn't find any wall / chamber abnormalities, regional or global, I think you are safe.
Roughly, there are just a few possible cardiomyopathies:
Hypertrophic (too thick heart muscle walls). Can manifest with reduced EDV and relatively high EF (can be caused by high blood pressure but often genetic)
Dilated (stretched heart muscle walls). Can manifest with increased EDV and reduced EF. Can occur with chronic tachycardia / rapid AF
Ischemic (reduced blood supply). Reduced EF during exercise.
Infectional (myocarditis): Often dilated and weakened with reduced EF. Toxic effects on the heart, radiation, and in some cases, extremely frequent PVCs, can give the same effect.
As you can see, most of them can easily be ruled out with echo and especially stress echo/nuclear stress test.
I would say, if you can work out at 100% of max, without symptoms like chest pain and shortness of breath, chance of angina is really low. Some people have "silent ischemia" (no chest pain) but it can often cause shortness of breath, and the blood pressure will not increase as much as it should, I think. We all have plaque in our coronary arteries, but that's how the body works with age. Angina is a pronounced variant of this.
At the gym, you can find exercise bikes with effect measured in watts. There is a formula you can use to check your condition level (note: in European units, you can convert the numbers using various calculators)
The condition level is measured in metabolic equivalents (METs). 1 MET is your metabolism and oxygen uptake at absolute rest (3,5 ml O2/kg)
METs = ((Total watts x 12)+300) / (weight kg x 3,5).
If you achieve more than 10-12 METs, your condition level is good. Athletes achieve 15 METs or more.
I'm not sure if this is relevant, though. I hope the doctor will answer you soon, best wishes to you, and merry christmas to you and your family!
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