According to the ACHA, competitive or vigorous swimming and rowing are dangerous exercises for heart disease patients. Swimming, especially swimming alone, can be fatal if you are predisposed to dizziness, fainting or have an ICD implanted. The exercise is strenuous itself, but combined with unexpected injuries or possibly being shocked by an ICD is very dangerous.
The rowing machine is intense with a harder effect on the heart and can cause sudden chest pain or injury. It’s more intense than stepping, spinning, or any other machine.
I’m glad I learned this tidbit of exercise knowledge this weekend.