Interventional cardiology: the future beyond the coronaries

It was not long ago that I was a medical student at McGill. I graduated in the class of 1996. When I started to do interventional work as a Cardiology Resident at McGill, we were well into the era of coronary intervention. Almost every balloon angioplasty was followed by the implantation of a stent, which had been shown to improve the immediate and long-term results of interventional therapy. Life was becoming easier, dual antiplatelet therapy had emerged and replaced heparin, dextran, and warfarin which were initially used to treat every patient with a stent to prevent acute thrombosis. Our equipment had improved with better, less bulky balloons that allowed for smaller caliber guiding catheters and arterial access. This allowed vascular complications to diminish significantly. Stents were now being manufactured attached to balloon catheters decreasing the risk of stent embolization. There were also a number of pharmacologic strategies including 2B3A inhibitors which significantly reduced morbidity in high risk patients. It has been about 8 years since I first scrubbed for an angioplasty and much has changed. We now know quite a bit about patient selection, risk management, and the outcomes after coronary interventions. Regular stents are still widely in use but drug eluting stents are being implanted in great numbers. The albatross around the neck of the stent era of coronary intervention was instent restenosis, an aggressive healing response to the arterial injury which occurs with both balloon angioplasty and stent implantation. This process results in renarrowing of the stented segment over the course of the first 6 to 9 months of follow up. Restenosis generally presents as recurrent angina. The risk of restenosis is related primarily to the presence of diabetes, and the length and diameter of the stent implanted. The arrival of drug eluting stents has greatly diminished the risk of patients developing restenosis and thereby requiring repeat procedures and suffering recurrent symptoms. Drug eluting stents have encouraged a more aggressive percutaneous approach to the treatment of coronary artery disease in patients who would have previously been directed toward surgical revasculariztion. When only bare metal stents were available, it was hard to justify pursuing an angioplasty that would almost certainly result in restensosis. Drug eluting stents have been implicated in an increased risk of stent thrombosis (a much more deadly acute occlusion of a stented segment) late after the index procedure. Drugs are likely to delay endothelialization of the stents by blocking the intense healing response which causes restenosis. A prolonged duration of dual antiplatelet therapy with ASA and Clopidogrel, longer than the 3–6 months recommended in the initial trials of these therapies, has been suggested by most interventional practitioners and is thought to be protective. The most recent analyses have suggested no increased risk of drug eluting vs bare metal stents in up to 4 years of follow up after a coronary intervention. They have also shown no difference in the rate of death or death/myocardial infarction in these 2 groups calling into question the cost effectiveness of drug eluting stents, which are three to four times the cost of bare metal stents. Despite the above, I am unaware of any cardiologist who would not want a DES implanted at the time of their own angioplasty. Coronary intervention has been compared to coronary artery bypass surgery in many populations both with bare metal stents and with drug eluting stents. In summary, there is really no evidence of mortality benefit of one of these treatments versus the other. The angioplasty patients generally require repeat procedures versus the surgical patients. Despite an apparent advantage of surgery, most patients who have been given a full informed consent choose angioplasty for its less invasive properties and the shorter recovery times required. A discussion of coronary disease could easily fill volumes with data, conjecture and opinion. Although coronary artery disease by far occupies the most time of any cardiac interventional program, many other interventions are currently being performed to treat cardiac disease and will be the focus of the remainder of this discussion. Structural heart disease is an explosive area of cardiovascular interventional cardiology and can be alternatively defined as non-coronary cardiac intervention. Interventions in structural heart disease occupy increasing time at many scientific meetings and are seeing a rise in the number of practitioners carrying out these interventions.