Hi Marcus.
There's no particular health condition that's a contraindication for hair transplantation. Local anaesthesia is used, so heart disease shouldn't be an issue. The slight exception is atrial fibrillation, which often requires patients to be on an anticoagulant to reduce the risk of stroke, in which case medication would need to be stopped a few days before the procedure.
In any case, your prospective surgeon should discuss any health issues with you at your consultation.
Cheers,
Postdoc