Drug-eluting Stents and LIMA to LAD: The Future of Coronary Revascularization
March 2005
Combining minimally invasive coronary artery bypass grafting (CABG) with percutaneous coronary intervention (PCI), often referred to as the hybrid procedure, or integrated coronary revascularization (ICR), was first described in the mid 1990’s. The goals for the first procedures then are essentially the same for hybrid procedures now: to retain the long-term durability of CABG, but lessen the procedural morbidity and trauma in favor a minimalist approach, akin to PCI. The concept of combining the best of both worlds from the catheterization lab and the operating room stems from the plain truth that in its present form, PCI is inferior to CABG with respect to target vessel revascularization, freedom from angina and long-term survival in those patients receiving a left internal mammary artery (LIMA) graft to the left anterior descending (LAD) coronary artery. On the other hand, CABG is highly invasive, traumatic, and possesses a higher procedural morbidity and longer recovery time when compared to PCI. Additionally, despite the superior long-term benefits of CABG, patients more often opt for the shorter-term fix offered by PCI because of its very low level of invasiveness.
Integrated coronary revascularization offers the patient a third option beyond the either/or approach to coronary artery disease: improved survival, vessel patency and less invasiveness. The hybrid procedure theoretically achieves this ambitious goal by combining a minimally invasive LIMA to LAD arguably the single most valuable procedure the coronary surgeon has to offer with drug-eluting stent (DES) implantation of the non-LAD targets, currently the best the interventional cardiologists have to offer. In truth, it is a theoretical advantage, as we do not have long-term data from a prospective randomized trial to support the use of the hybrid approach in all patients. However, it is clear that in patients with a plethora of co-morbidities and at high operative risk for standard CABG, the hybrid approach makes sense.
From a logistical standpoint, issues of anti-coagulation often dictate the surgeon perform the LIMA to LAD procedure before the stenting of the non-LAD targets. Most surgeons would prefer not to perform a procedure while the patient is on clopidogril (Plavix) for the risk of increased peri-operative bleeding. In contrast, discontinuing the drug soon after DES implantation runs the risk of stent thrombosis. The surgical part consists of essentially three phases:
(1) The thoracoscopic harvesting of the LIMA;
(2) Determination and creation of the access port for the anastomosis;
(3) Performing the LIMA to LAD anastomosis off-pump.
Under general anesthesia and using a double-lumen endotracheal tube, the left lung is collapsed to create working space in the left pleural cavity (Figure 1). Utilizing three 5mm ports along the patient's left side, the LIMA is harvested from the chest wall, leaving the artery intact proximally with the left subclavian artery. The pericardium is then opened and the epicardial surface exposed. Considerable care is then taken to clearly identify the LAD and diagonal branches and determine the optimal site for grafting. A 3cm access port is then created directly over the anticipated area of grafting. This working port is made as atraumatic as possible by preserving the pectoralis major and minor muscles and not spreading or manipulating the ribs in any way. Through this tunnel, the harvested LIMA is sutured to the side of the LAD while the heart continues to beat. The small area of the epicardial surface involving the graft is kept motionless by using a stabilizing device. This device allows the surgeon to place the sutures accurately but also minimizes the effects on cardiac contractility so as to maintain safe hemodynamic parameters. The flow through the graft is then measured using a transit time Doppler.
At the conclusion of the procedure, the patient is extubated and observed overnight in the intensive care unit. On the second postoperative day, the patient goes to the catheterization lab for stenting of the non-LAD targets. The interventional cardiologist also catheterizes the ostium of the LIMA first and takes several shots of the graft throughout its entire length as well as the anastomosis. The patient is then discharged later that day or the morning of the third postoperative day. Overall, 80% of the patients have returned to work and/or normal activity within three weeks, many within ten days.
At Emory University Hospital, we have performed 35 hybrid procedures in the last 14 months, with 30 patients undergoing a LIMA to LAD graft and five patients receiving a LIMA to LAD and diagonal sequential graft. A total of 46 stents were implanted in 42 non-LAD target vessels for a mean of 1.1 stents per vessel and 1.3 stent per patient. Thirty-five of the 46 stents (76.1%) were drug-eluting: 20 with paclitaxil (Taxus, Boston Scientific Corporation, Maple Grove, MN) and 15 with sirolimus (Cypher, Cordis Corporation, Miami Lakes, FL). There were no ninety-day major adverse cardiac events (MACE) including all-cause mortality, non-fatal myocardial infarction or stroke. All patients underwent post-operative angiograms that revealed patency scores of FitzGibbon A, 95% and FitzGibbon A+ B, 100%. The target vessel failure rate (TVF) rate for stent implantation was 7.1%. Three patients required repeat stenting. No patients required repeat CABG.
Our patient with three-vessel disease at the beginning of the discussion underwent a minimally invasive LIMA to LAD, followed two days later by implantation of the left main and PDA with two paclitaxil-eluting stents. She was discharged on the third postoperative day and since her procedure, one month ago, has been pain-free and walking nearly a mile every day.
In summary, the safety and feasibility of performing a hybrid approach to coronary artery revascularization has been established at our institution as it has in several centers across the world. The rational for an integrated approach is logical and appears to offer significant advantages to patients, especially high-risk cases. However, many questions remain unanswered regarding the long-term results of the hybrid procedure. Despite the short-term clinical success of the minimally invasive LIMA to LAD and drug-eluting stents in several elite centers, are the results applicable to the real world? In order to justify a more liberal use of the hybrid approach, clinical data will be required to support a superiority claim of the hybrid over standard bypass surgery with respect to procedural morbidity and a non-inferiority claim with respect to clinical events and target vessel revascularization. Ultimately, these are questions that can only be answered adequately by a controlled clinical trial.
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