There are actually plenty of cardiologists who do only diagnostic caths. Not every lesion seen on angio is fixable by angiographic means (angioplasty, recanalization and stenting). A certain share of patients who do have lesions will go to a CT surgeon instead to receive some form of coronary artery bypass grafting. Also, not every hospital that has a cath lab is equipped and certified to perform coronary intervention. For elective interventions, it is still required to have a CT surgery service who could potentially bail you out if things go south during an intervention. In emergency settings, hospitals without CT surg backup will perform coronary intervention. There are more patients who can benefit from primary coronary intervention, only a small number of patients will suffer untoward effects due to the unavailability of a CT surg backup. (I know a group of 4 cards 2 are invasive, 2 interventional. The 2 interventional cards back up the invasive guys. If a patient needs an intervention, the one who did the diagnostic cath leaves a sheath in and the interventional guy comes in from his lake house to do the fix).
Lots of call, busy call.
Yes. For all other vascular and non-vascular interventions outside of the heart (renals, hepatic, peripheral, renal, carotids).