Introduction
With the recent and rapid advances in percutaneous coronary intervention (PCI) using drug-eluting stents, the number of high-risk patients with several comorbidities referred for coronary artery bypass grafting (CABG) has been increasing. Among these, patients are those with diffusely diseased coronary arteries, including severe calcifications or soft plaques in the vessel wall. Coronary endarterectomy (CE) has been introduced to treat severely or diffusely diseased coronary arteries in the mid-1950s . However, early experiences with this method were not satisfactory in terms of the clinical results compared with conventional bypass grafting . As the surgical techniques and technologies have evolved, the benefits of CE for the treatment of the diseased left anterior descending (LAD) artery have gradually become recognized . Thus today, CE complements conventional bypass grafting as a surgical revascularization method for patients with diffusely diseased coronary arteries. In this chapter, we review the technical aspects and surgical outcomes of CE for the diffusely diseased LAD.
Operative indications
CE is usually performed for diffusedly diseased coronary arteries that have long segmental stenosis because of severe calcification or atheromatous plaque. CE is planned in patients with diffusely diseased distal vessels with luminal diameters ≤1.0 mm, as determined on preoperative angiography. Occasionally, the decision to perform CE is made intraoperatively, when conventional anastomosis cannot be carried out because of the presence of large soft plaques, which would be at high risk of distal embolism. This situation cannot be anticipated by preoperative angiography. With an endarterectomy, an anastomosis site can be obtained when there are complex intimal lesions, severe calcifications, or soft plaques, all of which rule out the establishment of conventional distal anastomosis.
Nowadays, the target coronary artery for performing CE is mainly the LAD, though historically, CE had been initially performed for the right coronary artery (RCA). CE for the diffusely diseased LAD has the advantage of providing a blood supply to the side branches such as diagonal branches and septal perforators, which can relieve ischemia in the anteroseptal territories of the heart. This cannot be achieved by conventional bypass grafting to the distal LAD alone, because it cannot exclude the diffusely diseased segments. CE, by eradicating the chain of plaques, can directly ensure blood flow to the side branches of the LAD. The advantage of CE for the LAD over conventional bypass grafting is particularly important because its incomplete revascularization is a predictor of a higher mortality after CABG . By contrast, CE for the left circumflex or RCA is seldom performed because the patency rates of the conduits grafting for these vessels are worse than those for the LAD. Actually, CE to the RCA is reported to be associated with increased postoperative myocardial infarction (POMI) .
Furthermore, the techniques of CE can be applied not only to diffusely diseased coronary arteries but also to in-stent restenosis (ISR) after PCI. Long-segment ISR in the LAD after multiple stenting (full-metal jacket) involving side branches affects myocardial perfusion of anteroseptal region. In our experience, CE with concomitant stent removal for ISR can restore the blood supply to the myocardium in the anteroseptal region and provides excellent clinical and angiographic outcomes with favorable symptomatic results .
We do not perform CE when the myocardium supplied by the target coronary artery has no viability due to large areas involved by previous myocardial infarction. Therefore preoperative evaluation of myocardial viability is performed in patients with areas of akinetic or dyskinetic myocardium due to its supply by the diffusely diseased coronary artery.
Surgical techniques of coronary endarterectomy
In most cases, atheromatous plaques and calcifications in the middle portion of the LAD can be observed through the adventitia by inspection. CE is performed manually, without the use of forced carbon dioxide or excimer laser. We have two ways to remove the atheromatous plaque, the closed (traction endarterectomy) and open (direct-vision endarterectomy) methods, and both have pros and cons. Closed endarterectomy is carried out by traction of the distal endarterectomized intima through a small proximal arteriotomy. This method is relatively fast but it has several disadvantages, including possible severance of the intima of the diagonal branches and septal perforators (a “snow-plow” effect) and occlusion of the distal end of the lumen by a dissection, due to an insufficient endarterectomy. On the other hand, although the open direct-vision endarterectomy is more time-consuming, the openings of the side branches and the distal end of the LAD can be observed directly. We therefore prefer the open method with a long segmental incision rather than the closed traction method ( Fig. 14.1 ) .
In the open method as performed by our group , the incision is initially made in the middle, but relatively distal, portion of the LAD and then extended proximally and distally. The atheromatous core is carefully dissected from the adventitia with a fine spatula and forceps ( Fig. 14.2 ). All side branches involved in the atheroma are observed directly and their intimae are carefully dissected and removed. The proximal atheromatous core is sharply divided to avoid removing the most proximal stenotic lesion to prevent flow competition. The distal end of the atheromatous core is also sharply divided at the intact intima, with the distal side completed before the intimal diameter reaches 1 mm. The posterior wall of a divided intima of the distal LAD is tacked with an 8-0 polypropylene suture. Saline irrigation is performed on the adventitial surface to remove the fragments of atheromatous core or media since these can be the cause of distal embolism.
The incised part of the LAD is reconstructed using the in situ left internal thoracic artery (LITA). Because of its superior patency rate we prefer using the LITA rather than a saphenous vein graft or other arterial grafts. The LITA is dissected in a skeletonized fashion using ultrasonic scalpel and incised to match the length of the LAD. Long reconstruction of the incised LAD using the LITA is performed with several 8-0 polypropylene sutures to prevent purse-string effect. First, the proximal LAD and the heel of the LITA are anastomosed using the parachute technique and an 8-0 polypropylene suture. The distal LAD and the toe of the LITA are then anastomosed to match the length of the latter artery, again using 8-0 polypropylene sutures. Next, the two sides of the LITA and LAD are anastomosed using 8-0 polypropylene sutures. During the anastomosis, care must be taken not to injure the ostium of the side branches of the LAD.
CABG without cardiopulmonary bypass (off-pump CABG) is our first choice for CE . Other investigators have demonstrated that CE without cardiopulmonary bypass can be performed safely . However, patients with severely impaired left ventricular function, intramyocardial coronary arteries or redo surgery were not feasible for the candidate for CE with off-pump CABG.
Postoperative management
The most disastrous complication after CE is early occlusion of the endarterectomized vessel . This is often as a result of local hypercoagulation related to a triggering of the coagulation cascade by the lack of endothelium in the early postoperative phase . Therefore patients underwent CE must be carefully and closely managed with antiplatelet and anticoagulation agents. We start continuous intravenous heparin infusion when the drainage from the mediastinum is less than 100 mL/h. Subsequently, low-dose aspirin (100 mg/day) and clopidogrel (75 mg/day) are prescribed beginning the day after surgery, at which time warfarin, maintained with a target international normalized ratio (INR) of 2.0, is also started. Intravenous heparin infusion is continued until the target INR is achieved. Warfarin and clopidogrel administration are discontinued after 3 and 12 months, respectively, but aspirin is continued indefinitely in all patients. Several reports described that postoperative medication did not have an impact on clinical outcomes among patients undergoing CE : optimal regimen of postoperative medication after CE is controversial.
Early postoperative angiography is performed during the same hospitalization to confirm graft patency in all patients who provided informed consent. Follow-up angiography is carried out 1 year postoperatively.
Early and long-term clinical outcomes
Historically, reported postoperative mortality and morbidity following CE were high (up to 9%) . However, with advances in surgical technique and perioperative management endarterectomy is considered to be a safe procedure and the outcomes are favorable . In a metaanalysis of 30 studies including 63,730 patients, Wan et al. evaluated the early and long-term outcomes of patients undergoing CE . Overall mortality was 5.4%, but the rates reported after 2000 (4.3%) were better than those reported before 2000 (5.9%). In our experience, patients undergoing CE for the LAD had a 30-day mortality rate of 1.1% , similar to those determined by other investigators . The higher mortality associated with CE than with isolated CABG can be attributed to the role played by associated comorbidities and risk factors rather than to the endarterectomy per se . Moreover, previous reports suggested that multiple endarterectomies and closed technique were associated with adverse outcomes such as POMI or operative mortality .
According to the above-mentioned metaanalysis , the long-term survival rate of patients undergoing CE is similar to that of patients treated by isolated CABG (hazard ratio=1.16, 95% confidence interval 0.32–4.22, P =.82). In our experience the overall 5-year survival rate and the free from major adverse cardiac and cerebrovascular events rate in patients undergoing CE for the LAD was 89.3% and 74.0%, respectively . Other comprehensive study shows that open CE with CABG may carry a lower 30-day mortality than closed CE with CABG and utilization of the ITA may improve mortality and graft patency when combined with open CE .
Angiographic outcomes
Qureshi et al. reported that the early and interval patency rate of the endarterectomized artery was 83% and 75%, respectively . In the series of Goldstein et al., the early and late patency rate of the endarterectomized LAD was 100% and 75%, respectively . Nishi et al. reported that the patency rate following endarterectomy is a function of the chosen surgical method. At mid-term follow-up, the grade A patency rates (stenosis- or occlusion-free anastomoses) obtained with the open and closed methods were 76.1% and 38.1%, respectively, although the overall patency rates of the two groups were comparable (89.1% and 81.0%) . Intravascular ultrasound sonography showed that the intima of the LITA became circumferential, with the construction of new intima in vessels endarterectomized using the open method. The angiographic results supported the use of the open over the closed method. In our 10-year experience, patency rate of the LITA grafted to the LAD at early postoperative and follow-up angiography was 91.6% and 96.6%, respectively . Previous reports by our group described that vascular remodeling of the LAD following long segmental reconstruction using the LITA with or without endarterectomy was obtained within 1 year after surgery and that optical coherence tomography revealed that the endarterectomized LAD was completely endothelialized within 1 year after surgery ( Fig. 14.3 ).
