Hi, long time reader, first time poster.
Firstly, I hope that everything pans out well for you. Heart trouble is always going to make you sit up and take notice. You mentioned about the heart possibly adapting to weight training and you're quite right, it does. The correct term is cardiac hypertrophy and is a thickening of the myocardial walls, mostly between the ventricles. In the majority of cases, it isn't too much of an issue because the ventricles also grow in size with the myocardia. However, in some cases, the thickening of the heart muscle leads to a reduction in the ventricles' space and in even more rare cases, the atria as well. This limits the amount of red blood cells the body can process, which means in turn, less oxygen transported to the body. The heart has to beat more per minute than it would do if the spaces between the atria and the ventricles was of a normal size. In extreme cases, hypertrophic myocardia is possible, though research on this is limited at present. The advice to stop your cycles above is sound advice. It seems that you may be one of the unlucky ones. It's also worth noting that cardiovascular exercise can help increase the ventricles' size (reduced heart rate is down to the heart being able to "fill up" with more blood) so some more cardiovascular at a moderate intensity might be an idea, but check with your doctor. Best of luck.
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