20 years ago today two pivotal papers were published in the New England Journal of Medicine. The BENESTENT and the Stent Restenosis Study compared balloon angioplasty to coronary stenting in people with stable angina. What people remember is that stents were superior to balloons and the rest as they say is history. But the story is more complex than that as the trials show.
Stents had been around since the late 1980's and they were effective in treating acute vessel closure due to balloon-induced dissection. This complication was the Achilles heel of interventional cardiology and led patients to emergency bypass grafting when their coronary artery closed off during or shortly after the procedure. Unfortunately Achilles had two heels and the other one was restenosis. Some people thought that stents might be useful to reduce the rate of restenosis but there was a problem. Stents were metal which required use of combinations of aspirin, dipyridamole, heparin and then for three months warfarin. This therapy exposed the patient to a risk of major bleeding and vascular complications prolonging hospital stay. In those days vascular access was via the femoral artery and the sheaths were about 3mm wide.
Read today the results of the trials are interesting. Take the BENESTENT trial, the rate of in-hospital events was similar in both groups (6.2% in the balloon vs. 6.9% in the stent group). There was no difference in the incidence of myocardial infarction or in the need for urgent or elective cardiac surgery or second angioplasty during the hospital stay. Stent thrombosis occurred in 3.5% and subacute vessel closure after balloon angioplasty in 2.7%. The incidence of bleeding and vascular complications was 4 times higher at 13.5% after stent implantation than after balloon angioplasty. Hospital stay was 8.5 days after a stent and 3.1 days after a balloon.
Now reading this is I am surprised. Stents were not so much better than plain old balloon angioplasty. Acute vessel occlusion was swapped for stent thrombosis and because of the anticoagulation patients had more complications and stayed much longer in hospital. There was no early gain.
But the differences was seen later with less clinical events by 7 months and less re-stenosis of the artery. So stents in stable angina had a rate of immediate clinical success similar to that of balloon angioplasty, but a lower rate of re-stenosis. Although they were a treatment for the coronary dissection problem there major value was reducing the re-stenosis. The next problem that needed to be solved was the thrombosis issue and vascular access site complications.
20 years on an a coronary stent is a day case procedure done through a tube less than 2mm wide via the wrist and with a complication rate less than 1% and re-stenosis rates almost as low. The requirement for on site surgery is a thing of the past.
The speciality of interventional cardiology is now mature. Where will it be in another 20 years?