Is It True Bilateral Internal Thoracic Artery Harvest for Coronary Artery Bypass Grafting Increase the Risk of Mediastinitis?
coronary artery bypass grafting, mammary arteries, mediastinitis
E Hijazi. Is It True Bilateral Internal Thoracic Artery Harvest for Coronary Artery Bypass Grafting Increase the Risk of Mediastinitis?. The Internet Journal of Cardiovascular Research. 2008 Volume 7 Number 1.
Deep sternal wound infection remains infrequent complication after coronary artery bypass grafting (CABG), and is associated with significant morbidity, mortality, prolonged hospitalization with increased cost of care. Patients with bilateral internal thoracic artery (BITA) grafts had improved freedom from myocardial infarction, recurrence of angina pectoris, percutaneous coronary angioplasty, and repeat operation [1, 2, 3].
A surgical technique was developed a decade ago in which the ITA is dissected as a skeletonized vessel . The advantage of using a skeletonized ITA is the preservation of collateral blood supply to the sternum. The skeletonized artery is gently isolated with silver clip and scissors without the use of cauterization, a factor that probably decreases collateral vessel damage. The advantages of this technique are that a skeletonized artery is distinctly longer and its spontaneous blood flow is greater than that of a pediculated ITA . Clinical studies using technetium-99m methylene diphosphate bone scanning and single photon emission computed tomography provided evidence that dissecting an ITA as a pediculated graft reduced blood supply to the sternum more than harvesting an ITA as a skeletonized vessel [9, 10, 11].
Harvesting of pedicled BITAs has been associated with an increased risk of deep sternal wound infection, especially in diabetic, elderly, and obese patients [5, 6, 12]. Other risk factors for sternal complications include obesity, chronic obstructive pulmonary disease, advanced age, peripheral vascular disease, redo surgery, postoperative low-output syndrome, and reoperation for bleeding . Kouchoukos et al demonstrated sternal wound infection rates of 1.9% and 6.9%, respectively, for single ITA and bilateral ITA . Furthermore, in diabetic patients undergoing CABG the use of BITA has been associated with higher percentages of mediastinitis which can be as high as >10% [14, 15]. Several mechanisms may be involved in poor sternal healing in patients undergoing BITA grafting, but the main one is probably related to decrease sternal blood supply after BITA harvesting. Numerous studies have demonstrated that harvesting of pedicled BITAs causes transient almost complete devascularization of the sternum [16, 17]. A surgical technique was developed a decade ago in which the ITA is dissected as a skeletonized vessel . The use of techniques for skeletonizing the ITAs during preparation, thus minimizing the decrement in sternal blood supply, may decrease the incidence of sternal complications . De Paulis et al  prospectively collected data on patients undergoing coronary artery bypass operations with at least a single internal thoracic artery were reviewed. The last 450 patients receiving bilateral internal thoracic artery grafts were compared with 450 patients who received a single internal thoracic artery during the same period. They concluded that bilateral internal thoracic artery harvesting carries a higher risk of sternal infection than harvesting a single internal thoracic artery. Skeletonization of both internal thoracic arteries significantly decreases this risk. Peterson and collage  reviewed prospectively gathered data on all patients who have undergone coronary artery bypass grafting and received bilateral internal thoracic artery grafts at their institution since 1990. They compared patients with diabetes who received skeletonized (n = 79) versus conventional pedicled (n = 36) internal thoracic artery conduits. They found that Skeletonization of internal thoracic artery conduits lowers the risk of deep sternal wound infection in patients with diabetes undergoing bilateral internal thoracic artery grafting. Calafiore et al  reviewed prospectively one thousand one hundred forty-six patients underwent isolated myocardial revascularization using BIMAs, 304 receiving pedicled grafts (group A, October 1991 through May 1994) and 842 receiving skeletonized conduits (group B, June 1994 through June 1998). Group B had a higher incidence of patients with diabetes (223 versus 40,
The combination of current evidence in the literature and new evidence provided by Boodhwani et al  performed a prospective, randomized, double-blind, within-patient comparison of skeletonized and nonskeletonized ITAs in patients undergoing coronary surgery, and indicates that skeletonized harvesting of the ITA reduces pain and hypoperfusion of the sternum compared with conventional pedicle harvesting. This combined evidence confirms that skeletonized harvesting of the ITA should be indicated in diabetic patients undergoing bilateral ITA revascularization. Kai et al  evaluated the effects of coronary artery bypass with off-pump skeletonized bilateral internal thoracic artery grafting in patients with insulin-dependent diabetes. One hundred eighty-five consecutive patients with insulin-dependent diabetes who underwent isolated coronary artery bypass grafting with bilateral internal thoracic grafts were retrospectively compared according to surgical technique, off-pump grafting with skeletonized internal thoracic artery (n = 162) or on-pump grafting with pedicled internal thoracic artery (n = 23). Their results support the surgical management of coronary artery bypass grafting in insulin-dependent diabetics using off-pump skeletonized bilateral internal thoracic artery grafting.
The current available evidence shows that careful skeletonized harvesting of the internal thoracic artery (ITA) offers many advantages with an acceptable risk of complications compared to pedicled harvesting of the ITA. Skeletonized BITA grafting can be performed with acceptable risk in all patients including higher risk group such as diabetics, but is not recommended for repeat CABG or for patients with COPD. We agree with the authors that all cardiac surgeons should be trained efficiently with regard to skeletonized harvesting of the BITA.