**3. Comparing coronary bypass surgery and PCI**

Shortly after the emergence of PCI as a reliable and durable therapy for CAD, comparisons between angioplasty and CABG were designed in order to determine the relative advantages of each modality. The BARI (Bypass Angioplasty Revascularization Investigation) trial compared balloon angioplasty with CABG in patients with multivessel CAD and severe angina or inducible coronary ischemia. After 5 and 10 years follow-up, no difference in long-term survival was demonstrated [34, 35]. Similar results were noted in other randomized trials of PTCA versus CABG [36, 37]. It was commonly noted in these trials that reintervention for recurrent angina symptoms was significantly more common for patients treated with an initial strategy of PTCA [BARI, RITA, GABI]. However, on subgroup analysis, survival advantage for CABG was demonstrated among diabetic patients in the BARI trial [35]. Finally, a meta-analysis of 13 randomized controlled trials comparing CABG with PTCA showed improved survival for CABG at 5-8 years in those with multivessel CAD and in diabetic patients [38].

Even as studies comparing PTCA with CABG were enrolling, bare-metal stents (BMS) were introduced, and trials to compare the new technology with CABG emerged. The randomized Stent or Surgery (SoS) trial compared multivessel CAD treatment by CABG or by PCI with BMS [39]. At a median follow-up of 2 years, these data showed reduced rates of coronary reintervention and significantly fewer deaths after CABG. Similar trials comparing CABG and PCI with BMS did not demonstrate a survival advantage for either therapy [40], although diabetic patients appeared to have improved survival after CABG in the Arterial Revascularization Therapies Study (ARTS 1) [41].

The US Food and Drug Administration approved DES therapy in 2003, stimulating another round of comparisons between CABG and PCI with the newer technology. Hannan et al reviewed risk-adjusted data from the NY State Dept of Health comparing patients who underwent CABG or PCI with DES for multivessel CAD over a 15-month period shortly after DES approval [5]. At a mean follow-up of 19 months, CABG patients experienced reduced hazard ratio for death, reduced mortality, reduced death/myocardial infarction composite, and less need for repeat revascularization [5]. However, the data were not acquired in the context of a randomized trial. Finally, the SYNTAX trial, a prospective randomized trial conducted across Europe and the US, compared PCI with DES and CABG in patients with 3-vessel CAD, left main CAD, or both [6]. The primary outcomes were major adverse cardiovascular or cerebrovascular events, and follow-up was provided for 12 months after intervention. The SYNTAX data demonstrated increased rates of MACE in the

Conduit Selection for Improved Outcomes in Coronary Artery Bypass Surgery 147

redo coronary surgery [60]. In addition, early vein graft failure is associated with increased perioperative myocardial infarction [10, 61], which consequently affects survival after CABG

Several potential explanations exist for the recently chronicled poor performance of RSVG as aorto-coronary conduits including early technical errors, endothelial injury, and early thrombosis, which may be related to insufficient biologic reaction to aspirin or inadequate antiplatelet effect of aspirin [62-64]. One important contributor to poor RSVG conduit performance, receiving significant recent attention, may be the practice of harvesting the conduit endoscopically (EVH). This technique was introduced and popularized in the 1990s and has been widely adopted due to increased incisional comfort and patient satisfaction, and decreased wound complications compared to open vein harvesting [65, 66] such that at least 70% of CABG patients undergo EVH based on recent Society of Thoracic Surgeons Database reporting [67]. However, EVH has been associated with increased endothelial injury, which may have significant negative consequences including graft patency and possibly long-term survival [68, 69]. Desai et al recently demonstrated using optical coherence tomography that EVH operators had a steep learning curve with regard to subtle RSVG injuries and that vein grafts with four or more intimal or medial dissections showed significantly worse early patency rates than those with fewer intimal injuries (67% vs. 96%)

In contrast, when RSVGs are harvested using a "no touch" technique, better patency results have been noted. The "no touch" method avoids vein stripping, taking surrounding tissue, and avoids over-distending the vein conduit as it is being prepared for coronary anastomosis [71]. This has also been shown recently to preserve the venous vasa vasorum [72]. Perhaps this helps to explain differences in contemporary SVG patency rates versus those reported historically, which were always done by an open surgical technique. Other predictors of improved vein patency include grafting to the LAD coronary artery versus other target sites, smaller venous conduit size, and larger diameter target coronary artery. In contrast, young age and low EF reduced long-term patency [60]. The type of distal anastomosis (sequential, y- or t-grafts, or other composite grafts) did not affect long-term patency [60]. Based on these data, some suggest SVG from the calf/lower leg since size and possible thickness of the vein is better [60]. Additionally, EVH is more difficult to perform on the lower leg; therefore, programs committed to EVH likely neglect this potentially

Current surgical patient cohorts have also been implicated in reduced vein graft patencies. For example, it is generally accepted that contemporary patients referred for surgery are older and more medically complex [73]. For example, many patients referred for CABG are diabetic, a condition that is notorious for more complicated and diffuse CAD [46, 74]. In addition, it has been proposed that venous grafts in elderly may be of inferior quality

Several advantages to arterial grafting have been demonstrated relative to CABG without arterial grafts. Most notably, the LIMA-LAD graft has been shown to be an independent predictor of survival after CABG when compared with patients not receiving LIMA-LAD [76]. In addition, using more than one IMA graft reduces the need for subsequent reintervention and prolongs survival relative to patients receiving only one arterial grafts

[58, 59].

[70].

advantageous conduit.

relative to younger patients [75].

**5. General advantages of arterial grafting** 

PCI group, primarily related to the increased need for repeat intervention. Death and postprocedure MI were not significantly different between the two groups, but there was an increased stroke rate in the CABG group compared with PCI, which is somewhat offset by the fact that surgical patients were not managed with aggressive antiplatelet therapy as compared to the PCI group, and many of the cerebrovascular events occurred outside of the perioperative period. More recently, three-year follow up SYNTAX data were reported confirming advantages of CABG over PCI with regard to MACE. Unlike 12-month data, however, composite safety endpoints were no longer different between the two groups, including a similar stroke rate [42]. The SYNTAX authors concluded that CABG remains the preferred therapy for 3-vessel or left main CAD but recommend longer follow up, as is planned for an additional two years [6].

Despite the favorable data for CABG emanating from carefully designed and conducted randomized trials, rates of CABG referral have decreased consistently since the introduction of PCI with stent technologies [43]. Preference for PCI appears driven by disparate interpretation of PCI-versus-CABG studies, by strong patient preference for less invasive procedures with presumed lower periprocedural risk, and by the promise for faster recovery. As a result, the percentage of patients referred for CABG with previous PCI has increased steadily [44] with higher acuity relative to patients without previous intervention [45]. Additionally, technical details of CABG in current surgical practices are considered more challenging compared with previous eras due to more diffuse CAD, subjectively smaller distal coronary targets, particularly among diabetic patients, and the high incidence of prior PCI [46]. Consequently, contemporary results for CABG following PCI are characterized by worse perioperative outcomes when compared with CABG patients without previous intervention. For example, higher rates of postoperative mortality, MACE, and other perioperative complications following CABG in both diabetic and nondiabetic patients have been observed [47-50]. More importantly, increased mid-term mortality in diabetic patients with prior PCI has been observed after CABG [50], and Rao et al demonstrated increased long-term mortality in patients with prior PCI who subsequently underwent CABG [51].
