Hybrid Revascularization: Another Step Forward in Coronary Revascularization

Coronary artery bypass grafting of the left anterior descending coronary artery (LAD) using internal mammary artery (LIMA) has been shown to be more effective than interventional treatment with respect to event-free survival and relief of ischemic symptoms.1,2 Internal mammary graft to LAD has a patency rate of more than 95% at 5 years.3 However, the disadvantages of conventional bypass surgery include neuro-cognitive impairment resulting from cerebral embolization of atherosclerotic plaque, air, fat and platelet aggregates, marked hemodynamic fluctuations, cerebral hyperthermia after the discontinuation of cardiopulmonary bypass and inflammatory and neurohumoral derangements associated with surgery.4,5 Cerebral complications are responsible for an increasing proportion of peri-operative deaths.6,7 Alternative forms of surgery which are minimally invasive are thus being investigated. Innovations in coronary artery bypass surgery techniques involve limiting the incision and/or eliminating the use of cardiopulmonary bypass using one of the following approaches: 1) A series of small holes or “ports” in the chest (referred to as PACAB, or port access coronary artery bypass); 2) a small incision directly over the coronary artery to be bypassed (referred to as MIDCAB, or minimally invasive coronary artery bypass) with or without the use of ports; or 3) off-pump coronary artery bypass (OPCAB) surgery. As with standard coronary artery bypass graft surgery, anesthesia is required. In the PACAB procedure, cardiopulmonary bypass is performed using the femoral vessels. The heart is stopped and bypasses are performed using instruments passed through the ports. The cardiac surgeon views these operations on video monitors rather than directly. The MIDCAB procedure combines both direct and indirect techniques. This procedure is performed through a small left anterolateral incision on a beating heart, without cardiopulmonary bypass. By avoiding extracorporeal circulation and median sternotomy, it offers major advantages, especially in the elderly and patients with comorbid conditions.8 The smaller surgical wounds heal faster, require less post-operative analgesia, result in fewer blood transfusions, reduced mechanical ventilation times, quicker ICU transfers and overall shorter hospital stays.9 However, larger randomized studies establishing the equal patency of bypass grafts when compared with regular sternotomy are lacking at this time. OPCAB involves regular median sternotomy but avoids the use of cardiopulmonary bypass. Robotically assisted minimally invasive surgeries are available at a limited number of referral centers and provide numerous technical advantages to the operating surgeon. The da Vinci® robotic system (Intuitive Systems, Sunnyvale, California) is composed of three major components: 1) The surgical control center (where the surgeon actually sits and performs the operation at a distance from the patient); 2) the instrument rack; and 3) the four robotic arms (in contact with the patient). Since the surgeon is holding the control arms remote from the patient, in contact only through fiber-optic cables with a filtration algorithm, human tremor is not an issue. Only the robotic arm enters the patient’s chest and holds the instruments as well as the video cameras. Another advantage is in the power magnification, available through these newer devices. Classical surgeons utilize the magnification lenses on their operative goggles for a 3- or 4-fold magnification. The robotically assisted surgeons can “dial in” the required magnification (up to 12-fold power) and do so with greater resolution. Recently, the video feed has evolved into a three-dimensional format that has also seen significant improvement over earlier devices. The surgeon remains comfortably seated throughout the operation and has an ergonomic control panel and robotic arm-activated headrest. Each of these developments provides the surgeon with greater comfort, less fatigue and absent tremor, while at the same time providing better visualization. These robots are also now capable of actual “wrist-like” movements, providing greater articulation through smaller incisions and allowing natural movements within a confined space. However, a significant disadvantage of the robotic tele-manipulation is the lack of tactile sensation. Also, patients with severe COPD and intramyocardial course of LAD are not ideal candidates for robotically assisted MIDCAB. Percutaneous interventional treatment of coronary lesions of the circumflex system or the right coronary artery are less frequently associated with subsequent restenosis than treatment of LAD lesions.10–14 Also, it is reasonable to consider surgical alternatives for LAD type C lesions which are considered to represent suboptimal indications for interventional treatment.11 The early restenosis rate of “non-LAD” vessels after percutaneous coronary intervention (PCI) is no longer very different from the early occlusion rate of venous bypasses, but after the initial critical restenosis period of six months, the results of PCI are more stable.15–17 Multiple studies showed that about 10% of the venous bypasses are occluded when the patients leave the hospital.18 At one year, 20% are occluded; at 5 years, less than 50% of the venous bypass grafts remain patent.18 These numbers may be compared with rates of restenosis of “non-LAD” vessels with bare metal stents, which are around 20% at six months and then remain stable up to > 8 years if the patient does not have restenosis.19 These numbers have improved dramatically with PCI using drug-eluting stents which substantially decrease the phenomenon of restenosis, already proven with the sirolimus and paclitaxel coating currently in use.20,21 Hybrid revascularization (HR) as reported in this article, integrated robotically assisted MIDCAB of LAD lesions with PCI of “non-LAD” lesions to provide complete revascularization in selected patients. In discussing the applicability of the hybrid concept, the sequence of the procedure is also important. As presented in this article and other similar studies, some authors perform PCI first, with the option that in case of any interventional complication, surgery will effectively treat the underlying coronary disease as well as the interventional complication in one procedure.22,23 However, improvements in the combined balloon/device/pharmacologic approach to coronary intervention in elective procedures has resulted in angiographic success rates of 96–99%, with Q-wave MI rates of 1–3%, emergency coronary bypass surgery rates of 0.2–3% and unadjusted in-hospital mortality rates of 0.5–1.4%.24 One of the disadvantages of this approach is the interruption of therapy with clopidrogel to allow the surgeons to proceed with CABG. The advantages of performing the LAD revascularization first would be: 1) an opportunity for verification of the LIMA to LAD short-term patency; 2) PCI being performed at a reduced risk as LAD is already revascularized with functioning LIMA; and 3) the patient could be pre-treated with clopidrogel and it would not have to be discontinued due to the CABG procedure. The timing of the two procedures evokes considerable debate with no definite consensus at the current time and perhaps a case-by-case basis would be most appropriate. The hybrid revascularization procedure may be especially useful in complex LAD lesions, restenotic lesions in LAD, acute myocardial infarction in “non-LAD” territory, high-risk elderly patients with multiple comorbidities and patients with severe left ventricular systolic dysfunction who are not ideal candidates for conventional bypass surgery. In this small series of patients, the authors report the feasibility of robotically assisted MIDCAB. A high rate (33%, or 2 out of 6 patients) of LIMA-LAD graft stenosis was noted in this series, which may emphasize the critical role of the learning curve associated with HR. Repeat PCI was required in about 50% of the patients. Also, the use of drug-eluting stents may have altered these results. A favorable overall complication profile was encouraging. A critical test for novel approaches is whether they produce the same long-term patency rates and survival advantage as traditional bypass grafting. At present, we must neither ignore the real potential for these new procedures, nor trivialize innovations. Rather, we must critically evaluate things in terms of time-honored endpoints of immediate and long-term patency and absence of cardiac ischemia. This warrants a prospective randomized trial comparing CABG and HR on a large-scale basis. As new options for and approaches to PCI and surgery continue to evolve, both the interventional cardiologist and the cardiac surgeon should participate in the formulation of a patient’s treatment plan. In doing so, the clinicians involved should consider not only issues related to risks, but also those related to long-term patency and survival of the patient. This approach does promise to be another advancement in our ability to successfully and safely perform coronary revascularization. As further improvements in technology continue, we should expect to see a greater number of patients with multivessel coronary artery disease undergo complete revascularization using either the percutaneous route alone or using the hybrid approach.

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