**2. IMAS versus BIMAS**

Arterial and vein grafts are used to perform the CABG surgery. Most patients receive three grafts in a combination of an arterial (LIMA) and vein grafts. [4]

Unfortunately, in the course of time, the atherosclerotic graft disease obstructs vein grafts. It has been shown that approximately 3 months after surgery is developed hyperplasia of the inner lining of the vascular grafts. The atherosclerotic disease of the grafts is characterized by adipose infiltration at the sites of intimal hyperplasia. Indicatively 12% of the vein grafts are occluded within 1 year, 25% within 5 years and 50% within 12 years following surgery. [5], [6] This contributes to the fact that 3% of the patients after undergoing a by-pass surgery require re-surgery in 5 years, 10% in 10 years and 25% in 20 years after the surgery. [7]

Arterial grafts started being systematically used in the 70's. The focus was on the internal mammary artery, which presents great biological properties:


Indicatively, with the coronary artery bypass, survival is related to the ejection fraction, according the Cardiothoracic surgeries database of Emory University, where 23960 patients

So, the main benefit from the bypass (CABG) is not only the symptomatic improvement and avoidance of the risk of a stroke, but also the evident prolongation of the patient's survival. On the other hand, it is obvious that even with CABG, long-term survival is decreasing. Even

when reviewing the sudden death risk as a result of CABG, there are three (3) stages.

**Years after CABG Loss (×1000)** ½ 3.4 1 0.87 5 1.2 10 3.5 15 9.0

There is an early, high-risk period, a period with rapid decrease of the risk and a period after 5 years, with an ascending risk rate. This late phenomenon is related to the atheromatosis of

Arterial and vein grafts are used to perform the CABG surgery. Most patients receive three

Unfortunately, in the course of time, the atherosclerotic graft disease obstructs vein grafts. It has been shown that approximately 3 months after surgery is developed hyperplasia of the inner lining of the vascular grafts. The atherosclerotic disease of the grafts is characterized by adipose infiltration at the sites of intimal hyperplasia. Indicatively 12% of the vein grafts are occluded within 1 year, 25% within 5 years and 50% within 12 years following surgery. [5], [6] This contributes to the fact that 3% of the patients after undergoing a by-pass surgery require

re-surgery in 5 years, 10% in 10 years and 25% in 20 years after the surgery. [7]

grafts in a combination of an arterial (LIMA) and vein grafts. [4]

EF "/> 50% 95 80 65 EF 30-50% 78 60 50 EF <30% 58 38 15

**5 years 10 years 15 years**

are registered as follows:

162 Artery Bypass

**Table 1.** Mortality as per Ejection Fraction

**Table 2.** Risk of death following CABG

the saphenous vein graft.

**2. IMAS versus BIMAS**


For all these reasons, the internal mammary artery, contrary to other vascular grafts, is not affected by intimal hyperplasia.

IMA's attrition rate compared to the saphenous vein is given in the following table:

**Table 3.** IMA and SVG attrition rate over 10 year period

It was only a decade after the systematic use of the internal mammary artery and specifically in 1986 that a benchmark publication came from the Cleveland Clinic [9]: In an extensive retrospective study they compared the clinical outcomes and angiography findings of 2306 patients who received single internal mammary artery (IMA) graft on the left anteriordescending artery (LAD) with additional vein grafts and 3265 patients who received only vein grafts. The mean follow-up time was 8.7 years. It was found that patients on whom the internal mammary artery had been used as a graft had lower perioperative mortality rates, less re-surgery rates, smaller chances of recurrent angina or infraction and higher 10-year survival.

**3.** A Belgian study [14] showed 97% patency of the 2 internal mammary arteries as shown

The Impact of Arterial Grafts in Patients Undergoing GABG

http://dx.doi.org/10.5772/54621

165

**4.** Buxton [15] analyzed 962 patients and found that the patency of the right internal mammary artery is better when used for left coronary by-pass. Moroever, he underlined that arterial grafts shall by-pass a coronary artery with stenosis over 90% (to avoid the risk of competitive flow). Passing the RITA to the left, either anterior to the aorta or

**5.** The same conclusions, meaning the use of the BIMAS on the left coronary system, were

**6.** B. Lytle [17] from Cleveland showed that the use of 2 internal mammary grafts is better than the use of a single mammary artery, regarding longer survival and lower re-surgery & recurrent angina or infraction rates. In addition, the study mentions that the benefit of the second internal mammary artery is evident 12 years after by-pass and offers a cumulative benefit. In patients with diabetes and those with a low LV ejection fraction the

**7.** The BIMA shows no benefits in the first 4 years, however after 15 years occurrence of

**8.** Finally, the statistically strongest study comes from Oxford [19]. It is an extensive metaanalysis of seven studies. Taggard et al compared 11,200 patients with a single internal mammary artery graft versus 4,700 patients with BIMA. This study as well reached the

same conclusions and showed prolonged survival when BIMA grafts were used.

Finally, it shall be underlined that all the above studies are retrospective and no prospective control studies exist till now for the single internal mammary VS the bilateral internal mam‐

The fact that radial artery grafts were patent for over 18 years after surgery [20] has been the basis to re-recruit the RA (radial artery) as a graft for CABG. There is low in situ atherosclerosis incidence for this artery, however the thickened middle lining, with the abundant cells of smooth muscle fibers (contrary to the internal mammary artery) increased intimal hyperplasia

Angiography studies of middle time duration showed 90% patency rate in 1 year [21], 83% in

Although these results are encouraging, the databases should be interpreted with caution. The majority of the studies are retrospective analyses and the rate of the grafts used for follow-up via angiography varies in these studies. The recent study by Possati [23] with 92% angiographic

follow-up for over 8 years, contains the most well-documented database to this day.

in angiographies in 161 patients at 7.5 years after by-pass.

through the transverse sinus, did not influence patency

study showed even greater benefit regarding survival.

recurrent angina is decreased from 36% to 27%. [18]

reached in a study by Schmidt [16].

mary grafting.

of this vessel.

**3. The radial artery**

5 years [22] and over 80% in 8 years.

A second study followed, by Acinapura et al [10] in which 2100 patients were followed-up for 5 years. The study showed that:


#### **Table 4.**

Ten-year mortality rate was 10% for the IMA group and 22% for the vein grafts group.

On the same grounds, Cameron and colleagues [11] compared 479 patients with single internal mammary artery graft to 4888 patients with solely vein grafts over a period of more than 15 years. They showed that the use of a single internal mammary artery graft was an independent prognosis factor that promoted survival, especially in older patient, with a reduced LV function.

Conclusively, the use of the internal mammary artery on the anterior descending branch is indicated irrespectively to the age and to the ejection fraction. Moreover, the use of the IMA in patients with a low ejection fraction improves long-term survival.

Because of the ostensible biological similarity of the left and right internal mammary artery, many were those who believed that the use of the two internal mammary arteries as grafts could yield additional benefits.

The patency of the 2 internal mammary (left & right) artery grafts is over 90% in 10 years. The reasonable question posed is: "Why don't we use more arterial grafts during a by-pass surgery?"

Let's answer through a short review of the recent literature:


Finally, it shall be underlined that all the above studies are retrospective and no prospective control studies exist till now for the single internal mammary VS the bilateral internal mam‐ mary grafting.
