The Clinical Impact of Drug-eluting Stents in Changing Referral Practices for Coronary Surgical Revascularisation

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Abstract

From the mid-1960s until the late 1970s, surgical revascularisation was the only effective treatment for multi-vessel coronary artery disease (CAD). In 1977, Gruentzig initiated a major advance when he performed the first percutaneous transluminal coronary angioplasty (PTCA). The advent of PTCA captured the imagination of surgeons and cardiologists very differently.

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Surgeons viewed PTCA with natural skepticism. Through the use of magnifying loops, surgeons had become accustomed to seeing and finely manipulating small arteries in the operating room. Because of their knowledge, to date, of need for delicate skills, they questioned how anyone would be able to introduce a small catheter into the femoral artery and subsequently navigate such via the left main coronary artery into small distal vessels to dilate them.

Cardiologists, due to their medical base as internists, did not regularly see arteries in the operating room, but rather envisioned them as two-dimensional conduits through the dye introduced via the catheter. PTCA represented an incredible opportunity for the cardiologists to treat their patients with CAD in a much less invasive manner.

As a result of PTCA, by the late 1970s, referral patterns for bypass surgery had already changed to include fewer patients with single vessel CAD. This represented a slowing in the growth of coronary artery bypass graft (CABG) surgery volume that was partially offset by an increasing number of referrals for emergency bypass as a result of PTCA procedural complications. The latter directly resulted from two parallel and interdependent issues that often arise at the time of medical breakthroughs. Cardiologists were on the early part of the learning curve of catheter-based procedures and were also using primitive and bulky first-generation devices 1.

At the time, Surgeons felt uncertain as to the future of this new procedure. Many believed that an epidemic of either acute failures or stenoses would erupt over the short- or long-term, overburdening the already crowded operating rooms. As a result of this line of thinking, it was suggested that there might be the need to increase the number of operating rooms in some hospitals, to prepare for an onslaught of patients in need of urgent myocardial revascularisation. Fortunately, for many reasons, this never happened.

Subsequently, throughout the 1980s and 1990s, the PTCA equipment became more sophisticated as did the skills of the cardiologists. The introduction of coronary stents has all but eliminated the need for an emergent CABG as a bailout for PTCA complications, further jeopardising surgical referrals. Trials in the late 1990s proved the benefits of primary stenting over PTCA alone. Also, the systematic use of stents has decreased the need for repeat revascularisation to about 18% to 20% in nondiabetic patients. 2

PTCA received a boost in the eyes of the medical community, when the results of the Bypass Angioplasty Revascularisation Investigation (BARI) were released. This study represented one of the first largescale trials that examined five-year cardiac mortality and MI rates in patients with multi-vessel disease randomised to either CABG or PTCA (without stenting). This landmark trial revealed no significant differences overall for the composite end point of cardiac mortality or MI between treatment groups, or for cardiac mortality in non-diabetic patients regardless of symptoms, left ventricular function, number of diseased vessels or stenotic proximal left anterior descending artery. This shocked cardiac surgeons and encouraged cardiologists to further explore improving such procedures. However, the BARI trial did illustrate that additional revascularisation procedures and hospital admissions were more common when PTCA was selected as the initial treatment modality. 3

A subsequent study, the Arterial Revascularization Therapy Study (ARTS) trial, randomised patients with multivessel disease to either stenting or bypass surgery. ARTS showed no difference in mortality between the two strategies after one year. Target vessel revascularisation (TVR) rates were lower with stenting than they had been in previous trials of balloon angioplasty – however, the CABG arm of the trial still had a significantly lower rate of TVR. The diabetic cohort did have a higher mortality in the stenting arm than in the CABG arm of the trial. 4,5/>/>/>/>/>/>/>/>/>/>/>/>

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References

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