**3.3. Use of LIMA and SVG grafts**

Use of internal mammary artery (IMA) grafts in patients undergoing CABG have been asso‐ ciated with improved short and long-term survival, increased patency and decreased perio‐ perative mortality. However, in patients with significant PAD, it could be the major source of collateral flow to the lower extremities in patients with aorto-iliac disease. The finding that the mammary artery collateralized the iliac artery led to major treatment changes in all patients undergoing CABG [73]. Therefore, it is advisable to perform angiography of this conduit before referral for CABG in patients with PAD.

In a study on 21,873 patients among whom 87% underwent grafting of left IMA, and were followed for 7 years, there was a significantly decreased risk of mortality in all subgroups. Additionally, the incidence of stroke, repeat intervention, bleeding compli‐ cations, mediastinitis or sternal dehiscence requiring surgery was less with use of IMA grafts. The adjusted mortality rate was 2.2% vs. 4.9%, and rate of stroke was 1.6% vs. 1.9% in patients undergoing IMA versus no IMA grafting, respectively. Infective me‐ diastinitis or sternal dehiscence was seen in 1.1% of the LIMA group and 1.3% of the non-LIMA group [74].

It has been shown that use of LIMA grafts is even associated with lower in hospital mortality even in patients with a higher number of risk factors such as age greater than 70 years, elevated left ventricular end-diastolic pressure, left ventricular ejection fraction less than 40%, small body mass index, or clinical presentation in acute or emergency setting. So, there is a proven consistent trend of protective LIMA effect in high risk groups as well [75].

### **3.4. Impact of PAD on graft failure in CABG**

stenosis (p = 0.0072). Also the risk of hemispheric stroke was 5.3% in patients with unilateral 80% to 99% stenosis, or bilateral 50% to 99% stenosis, or unilateral occlusion with contralateral 50% or greater stenosis. Patients with a unilateral 50% to 79% steno‐

In a study of 3344 patients undergoing CABG who were followed over a three year period to assess the effect of carotid artery stenosis on perioperative stroke and mortality, it was found that the clinical outcomes were directly related to the degree of carotid stenosis. Pa‐ tients with carotid stenosis <60% had a significantly less risk of suffering perioperative stroke and mortality when compared to patients with >60% stenosis, especially patients with

These studies signify carotid artery disease as an important subset of patients with PAD which can adversely affect post CABG outcomes in terms of incidence of stroke

Microvascular disease, such as that which occurs in diabetic patients has also been shown to adversely affect outcomes after CABG. These complications generally stem from a cumula‐ tive poor glycemic control. In a study on 223 patients with diabetic retinopathy followed 11 years post-CABG, it was found that diabetic retinopathy was a strong independent predic‐ tor of overall mortality (relative risk [RR], 4.0), and repeat revascularization (RR, 3.0) [72].

Use of internal mammary artery (IMA) grafts in patients undergoing CABG have been asso‐ ciated with improved short and long-term survival, increased patency and decreased perio‐ perative mortality. However, in patients with significant PAD, it could be the major source of collateral flow to the lower extremities in patients with aorto-iliac disease. The finding that the mammary artery collateralized the iliac artery led to major treatment changes in all patients undergoing CABG [73]. Therefore, it is advisable to perform angiography of this

In a study on 21,873 patients among whom 87% underwent grafting of left IMA, and were followed for 7 years, there was a significantly decreased risk of mortality in all subgroups. Additionally, the incidence of stroke, repeat intervention, bleeding compli‐ cations, mediastinitis or sternal dehiscence requiring surgery was less with use of IMA grafts. The adjusted mortality rate was 2.2% vs. 4.9%, and rate of stroke was 1.6% vs. 1.9% in patients undergoing IMA versus no IMA grafting, respectively. Infective me‐ diastinitis or sternal dehiscence was seen in 1.1% of the LIMA group and 1.3% of the

It has been shown that use of LIMA grafts is even associated with lower in hospital mortality even in patients with a higher number of risk factors such as age greater than 70 years, elevated left ventricular end-diastolic pressure, left ventricular ejection

sis did not suffer a stroke in this study [70].

**3.2. Impact of microvascular disease on CABG**

conduit before referral for CABG in patients with PAD.

a totally occluded carotid artery [71].

**3.3. Use of LIMA and SVG grafts**

non-LIMA group [74].

and mortality rates.

450 Artery Bypass

A major cause of short-term mortality post CABG and therefore, poor surgical out‐ come is graft failure. In 1972, Lesperance et al reported that out of a total of 105 sa‐ phenous vein grafts (SVG) used during CABG, 20% had early occlusion [76]. In a review of SVG disease, Motwani and Topol showed an early SVG occlusion rate of 15% and elucidated the diverse etiology of SVG closure [77]. At one month post CABG, the major cause of graft failure is thrombosis. From a month to one year post CABG, intimal hyperplasia is the chief contributor while after one year, atherosclerotic changes have been primarily implicated. They also demonstrated that arterial runoff was the single most important determinant of short-term graft survival. Occluded ves‐ sels distal to the SVG anastomosis resulted in thrombosis and graft failures.

The internal diameter of the mid-LAD is approximately1.7 mm, while that of the sa‐ phenous vein is 4-5 mm. This difference leads to variable flow rates and slow flow ve‐ locity in the SVG as compared to mid-LAD. The sluggish flow causes red blood cell sledging and consequent thrombosis. The internal diameter of the IMA is almost equivalent the mid-LAD, and thus there is decreased risk of graft thrombosis. They al‐ so highlighted that LIMA graft in addition to matching favorable dimensions of native LAD, lacks valves, has less endothelial fenestrations, and has a greater resistance to trauma while it is being harvested [78]. Other advantageous physiological characteris‐ tics of the IMA include higher flow reserve and shear stress, greater nitric oxide and prostacyclin production leading to vasodilation and inhibition of platelet aggregation, appropriate relaxation response to thrombin, less vasoconstrictor sensitivity and high vasodilator sensitivity along with decreased number of fibroblast growth factor recep‐ tors thus reducing plaque formation [78].

In a patent population in whom both radial artery and SVG grafts were used for CABG, it was found that radial artery grafts fared worse than SVGs in patients with PAD [79].

#### **3.5. Off pump CABG and standard CABG**

Off pump CABG (OPCAB) is referred to as CABG without use of cardiopulmonary bypass or cardioplegia while on pump CABG is referred to the use of cardiopulmonary bypass and cardioplegia. There have been various studies which generally show benefits of OPCAB as compared to standard CABG. Benefits include less bleeding complications, stroke and renal failure after OPCAB.

In a retrospective analysis of 68,000 patients by Ractz et al, 9000 OPCAB revascularizations were performed with this group comprising many high-risk patients including those with >60 years of age, female gender, low LVEF, previous history of CABG, stroke, PAD, conges‐ tive heart failure, calcified aortic disease, and renal failure. It was seen that the standard CABG group as compared to OPCAB group had higher rates of stroke (2.0% vs. 1.6%), high‐ er bleeding complications (2.2% vs. 1.6%), and prolonged hospital stay by one day. At 3-year follow-up, the need for repeat revascularization was also greater in standard CABG versus the OPCAB group [80].

**Author details**

**References**

Muhammad A. Chaudhry1

, Zainab Omar2

3 University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA

[1] Roques F, Nashef SA, Michel P, Gauducheau E, de Vincentiis C, Baudet E, Cortina J, David M, Faichney A, Gabrielle F, Gams E, Harjula A, Jones MT, Pintor PP, Salamon R, Thulin L. Risk factors and outcome in European cardiac surgery: analysis of the EuroSCORE multinational database of 19030 patients. Eur J Cardiothorac Surg. 1999

[2] Edwards FH, Grover FL, Shroyer AL, Schwartz M, Bero J, Clark RE. The Society of Thoracic Surgeons National Cardiac Surgery Database: current risk assessment Ann

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[4] Levey AS, Bosch JP, Lewis JB, Greene T, Rogers N, Roth D. A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equa‐ tion. Modification of Diet in Renal Disease Study Group. Annals of Internal Medicine

[5] Manjunath G, Tighiouart H, Ibrahim H, MacLeod B, Salem DN, Griffith JL, Coresh J, Levey AS, Sarnak MJ. Level of kidney function as a risk factor for atherosclerotic car‐

[6] Strippoli GF, Craig JC, Manno C, et al. Hemoglobin targets for the anemia of chronic kidney disease: a meta-analysis of randomized, controlled trials. J Am Soc Nephrol

[7] Cozzolino M, Brancaccio D, Gallieni M, et al. Pathogenesis of vascular calcification in

[8] Levin A, Li YC. Vitamin D and its analogues: do they protect against cardiovascular disease in patients with kidney disease? Kidney Int. 2005 Nov; 68(5):1973-81.

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diovascular outcomes in the community. J Am Coll Cardiol. 2003; 41(1):47-55.

\*Address all correspondence to: faisal-latif@ouhsc.edu

1 Scripps Green Hospital, La Jolla, California, USA

2 King Edward Medical College, Lahore, Pakistan

Jun;15(6):816-22; discussion 822-3.

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and Faisal Latif3

Impact of Renal Dysfunction and Peripheral Arterial Disease on Post-Operative Outcomes ...

http://dx.doi.org/10.5772/54417

453

In another retrospective study by Mack et al in which 17401 patients were reviewed and 7283 received OPCAB, it was found that even in patients with PAD among other risk fac‐ tors, patients undergoing OPCAB had improved mortality when compared to patients un‐ dergoing on-pump CABG (1.9% vs. 3.5%). The rate of complications including major bleeding, wound infection, atrial fibrillation, permanent stroke, gastrointestinal and respira‐ tory complications, renal failure, myocardial infarction, and multiorgan failure was higher in standard CABG group [81].

In another study comprising 214 patients at high risk (high EuroSCORE) with >50% of pa‐ tients with significant PAD, it was found that off-pump CABG was safer and was associated with less early post-operative complications including multi-organ failure [82].

Patients with PAD are likely to have complex atheromatous plaques in the arch of aorta which poses a risk for peri-operative stroke during manipulation for on-pump CABG sur‐ gery An analysis of 422 patients demonstrated that there was a significant reduction in postoperative stroke in patients who had OPCAB when compared to patients undergoing onpump surgery (0.9% vs. 5.7%, p=0.007) [83]. Therefore, for patients with PAD needing CABG, OPCAB would help avoid manipulation of aorta and in turn, decrease post-opera‐ tive cerebrovascular complications.

Over a period of time, an increasing body of evidence has indicated that OPCAB is better than on-pump CABG, especially in high-risk groups. This includes a significant benefit of OPCAB in patients with PAD as it reduces the risk of postoperative stroke. As it has been shown in the SYNTAX trial, which is the largest contemporary trial comparing PCI versus CABG, showed that the major risk with CABG appears to be the increased risk of stroke from it [84]. OPCAB can, at least reduce that chance which might improve the overall bene‐ fit of CABG in patients with advanced CAD.
