**7. Radial artery grafts as a second arterial conduit**

tively, patient scores in all areas of the questionnaire were significantly lower than that of the results of the standardized Danish population. Post-operatively, both revascularization groups showed significant improvement in all areas at 3 months and 11 months, with the TAR group showing improvement in the 'social functioning' category that was significantly higher than the conventional revascularization group. There was no significant difference in postoperative improvement in the categories 'physical component summary,' 'bodily pain,' and

**6. Incidence of sternal wound infection, subset of patients benefiting from BIMA, IMA harvesting techniques, and operative time in BIMA CABG**

One of the main concerns amongst surgeons regarding the use of BIMA in CABG procedures is the occurrence of sternal wound infections (SWI). When both internal mammary arteries are harvested, blood supply to the sternum may be more severely compromised than in single IMA procedures, thus increasing the risk for developing SWI. Various pre-operative and intraoperative techniques have been used to prevent the incidence of SWI, such as the use of prophylactic antibiotics, double gloving, and skeletonized IMA harvesting [7]. Skeletonized IMA harvesting is thought to preserve the collateral blood supply to the sternum and reduce

Patients who are insulin-dependent diabetics, morbidly obese, or who have severe COPD are at a higher risk of developing SWI (DSWI = deep sternal wound infection, definition varies)

In a study performed by Pevni *et al.*, 1,515 consecutive patients underwent CABG procedures with skeletonized BIMA grafting. In earlier studies, the authors state that, in their past experience, patients with chronic lung disease, diabetic females, and obese diabetics repre‐ sented absolute contraindications to BIMA grafting for CABG procedures because of the risk of SWI. However in this study, the authors found that there was no evidence of a relationship between diabetes mellitus and DSWI in patients receiving skeletonized BIMA grafts, even with

In a meta-analysis of 13 studies regarding BIMA CABG procedures and the harvesting technique for the IMAs, Saso *et al.* found that skeletonizing the IMA as opposed to harvesting it in a pedicled manner lowered the incidence of SWI by 60%. An even greater benefit of skeletonized harvesting was noted in groups at an increased risk for SWI, such as in diabetic patients. The authors also found that these decreased rates of SWI applied to the entire

Kurlansky *et al.* found a slightly higher incidence of SWI amongst diabetic patients receiving BIMA grafting compared to diabetic patients receiving LIMA grafting, but the difference was not significant. However, amongst patients receiving BIMA grafts, the presence of diabetes did affect the occurrence of SWI. This suggests that, while the presence of diabetes mellitus

and, in general, bilateral harvesting of the IMAs is avoided in these patients [7, 8].

a prevalence of diabetes mellitus of 34% in their patient population [23].

spectrum of sternal infections, including mediastinitis [22].

'vitality' between the two revascularization groups [21].

the risk of infection [22].

124 Artery Bypass

The success of the LIMA in CABG procedures has lead surgeons to search for other arterial conduits. The radial artery has become a popular choice as an additional arterial conduit in attempts to achieve total arterial revascularization of the myocardium. There are numerous advantages to using the radial artery, including its long length, exposure to systemic blood pressures, and the fact that it is seldomly affected by atherosclerosis. However, the radial artery has a thicker tunica media, which is thought to contribute to its greater vasoconstrictor response than the IMA and could possibly lead to vessel occlusion. Thus, care must be taken during operative harvesting and the use of calcium-channel blockers may ameliorate a vasospastic response [24].

Like the LIMA, the radial artery has been shown to have significantly better short and longterm patency results and outcomes than vein grafts. In the radial artery patency study (RAPS), Desai *et al*. randomized 561 patients to receive a radial artery graft to either the inferior (right) coronary territory or to the lateral (circumflex) coronary territory, with a saphenous vein graft anastomosed to the opposite territory in each group as a control. All patients also received a LIMA graft to the LAD, with the main endpoint of the study being 1-year angiographic complete occlusion of the radial artery versus saphenous vein. In this definition of occlusion, grafts displaying the string-sign would be considered patent. At the mean follow-up of 10.9 months, 13.6% of saphenous vein grafts were completely occluded and 8.6% of radial artery grafts were completely occluded (p = 0.009). The authors also found that the patency of radial artery grafts depends on the severity of the native vessel stenosis, with better patency results corresponding with higher grades of stenosis. Thus, the authors recommend using the radial artery for the most highly occluded coronary vessel after the LAD [25].

In a follow-up to the original RAPS study, Deb *et al.* extended the mean angiographic followup time to 7.7 years, with 269 patients of the original 561 undergoing late angiography. The primary endpoint was functional graft occlusion; vessels displaying narrowing or reduced flow were considered occluded as well as vessels that were completely occluded. 12.0% of radial artery grafts were determined to be functionally occluded compared with 19.7% of saphenous vein grafts (p = 0.03). For the secondary endpoint of complete occlusion, 8.9% of radial artery grafts were completely occluded compared with 18.6% of saphenous vein grafts (p = 0.002) [26].

Ruttman *et al.* studied 1,001 patients undergoing CABG procedures either receiving RIMA grafts or radial artery grafts as second conduits after LIMA grafts with or without concomitant saphenous vein grafts added when necessary. Propensity-score matched analysis was performed on the two patient groups to examine the short and long-term outcomes of BIMA grafting versus LIMA plus radial artery grafting. Overall, the evidence provides strong support for the use of the RIMA over the radial artery as a second choice arterial conduit. Radial artery graft occlusion and disease rates were significantly higher than both IMA and saphenous vein anastomoses, with occlusion/disease rates of 37.9%, 10.2%, and 20.9%, respectively. Survival rates for BIMA grafting were 98.9% at 1, 3, and 5 years post-operatively, compared with rates for the radial artery group of 96.8%, 96.3%, and 93.0% at the same postoperative years. The BIMA group also had significantly higher rates of major cardiac and cerebrovascular events-free survival than the radial artery group at the same yearly intervals

Total Arterial Revascularization in Coronary Artery Bypass Grafting Surgery

http://dx.doi.org/10.5772/54866

127

In a 10-year prospective, randomized trial, Hayward *et al.* examined angiographic out‐ comes of patients receiving either a radial artery, RIMA, or saphenous vein graft to the second largest coronary target after the LAD, which was grafted with the LIMA. Patients were randomized to two groups: those less than 70 years of age received either a radial artery or RIMA as the second arterial conduit, and those greater than 70 years of age re‐ ceived either a radial artery or saphenous vein. At a mean follow up of 5.5 years, a total of 350 patients between the two groups had angiography performed. In the first group, Kaplan-Meier estimates of graft patency were 89.8% for the radial artery and 83.2% for the RIMA (p = 0.06). In the second group, patency estimates were 90.0% for the radial ar‐ tery and 87.0% for the saphenous vein (p = 0.29). With no significant difference in the pa‐ tency rates between the conduits in each of the two groups, the results show that the choice of conduit for the second largest coronary target does not significantly affect pa‐

The clinical benefits of RIMA and radial artery use have been established, and many studies have indirectly examined the results of TAR in patients receiving BIMA or radial artery grafts without the need of concomitant saphenous vein grafts. However, few studies have specifically

In a prospective study by Muneretto *et al.,* 200 patients over 70 years of age were randomized into two groups either receiving TAR or conventional CABG (LIMA to LAD with additional saphenous vein grafts if needed). Even though 31% of patients in the TAR group received BIMA grafts, the incidence of perioperative sternal wound complica‐ tions was found to be 1% in both groups. At the mean follow up of 15 months, the inci‐ dence of cardiac-related events (MI, angina, coronary angioplasty, and graft occlusion) was significantly higher in the conventional CABG group compared to patients receiving

tency, giving surgeons flexibility in their revascularization plans [33].

compared the clinical outcomes of TAR to conventional CABG procedures.

**9. Total Arterial Revascularization (TAR)**

post-operatively [32].

Zacharias *et al.* compared 6-year outcomes in propensity matched CABG patients receiving LIMA to LAD grafts who also received either radial artery grafts or vein grafts only. The authors found that mortality rates were 67% and 98% greater in vein patients than in radial artery patients after 1 and 6 years, respectively. While LIMA patencies were always signifi‐ cantly greater than both radial and vein patencies, 6-year radial graft patencies were system‐ atically greater than that of vein grafts, although the results failed to reach statistical significance. Overall, the use of the radial artery as a second arterial conduit in LIMA to LAD CABG patients is associated with improved long-term survival [27].

Collins *et al.* compared 142 patients receiving either radial artery or saphenous vein grafted to the left circumflex coronary artery, with the end point being 5-year angiographic patency. 98.3% of radial artery grafts and 86.4% of saphenous vein grafts were found to be patent after the 5-year angiographic study of 103 patients (p = 0.04). The rate of graft narrowing was also significantly less in radial artery grafts compared to vein grafts, with narrowing occurring in 10% of patent radial artery grafts and 23% of patent saphenous vein grafts (p = 0.01) [28].

A smaller study by Cameron *et al.* also examined the 5-year angiographic patency results of radial artery grafts. Grafts that displayed a string sign were considered not patent. With a radial artery graft patency rate of 89%, the authors found that the radial artery had a patency rate similar to that of other grafts, although the study was too small to determine whether or not this result was statistically significant [29]. Acar *et al.* report similar results for radial artery graft patencies when compared to the LIMA [30].

Not all studies of radial artery use have been favorable. In a review of 310 patients receiving radial artery grafts between 1996 and 2001, Khot *et al.* found significantly lower patency rates for radial artery grafts when compared to IMA grafts, and similar patency rates when compared to saphenous vein grafts after a mean follow up of 565 ± 511 days. Patency rates of radial artery grafts, LIMA grafts, and saphenous vein grafts were 51.3%, 90.3%, and 64.0%, respectively. While patency rates were similar between radial artery and saphenous vein grafts, there was a significantly higher incidence of severe disease in radial artery grafts (p = 0.0003). Women were also found to have significantly lower radial artery patency rates than men [31]. However, Desai *et al.* specifically note that this study did not use randomized controls, standardized surgical methods, concurrent pharmacology, or routine angiographic follow-up that could lead to potential bias [25].
