Does competitive flow reduce internal thoracic artery graft patency?

BACKGROUND: In coronary arteries with moderate stenosis, competitive flow may lead to internal thoracic artery (ITA) graft occlusion. The goals of this study were to determine if competitive flow reduces ITA patency, and if there is a degree of coronary stenosis below which ITAs should not be used. METHODS: From 1972 to 1999, 50,278 patients underwent primary coronary artery bypass grafting (CABG). Of these, 2,002 had at least one ITA graft and postoperative angiography before coronary reintervention; 2,999 angiograms of 2,121 ITAs were made. Time-related ITA occlusion was modeled using longitudinal analysis to identify its risk factors while accounting for lack of independence introduced by repeated angiography and multiple ITA anastomoses per patient. Proximal coronary stenosis (maximum preoperative stenosis between ITA anastomosis and aorta) was the surrogate for competitive flow. RESULTS: Unadjusted ITA patency was 93%, 89%, 90%, and 92% at 1, 5, 10, and 15 years after CABG. Risk factors associated with ITA occlusion were lesser degree of proximal coronary stenosis (p < 0.0001); longer time from CABG in grafts to non-left anterior descending coronary arteries (p < 0.0001); female sex (p = 0.0003); later date of CABG (p = 0.01); right ITA (p < 0.0001); and smoking (p < 0.0001). In all arteries, as preoperative proximal coronary stenosis decreased, ITA patency declined; however, at no degree of stenosis was there a sharp decline. CONCLUSIONS: Internal thoracic artery patency decreases as coronary competitive flow increases. However, the nature of this relationship indicates ITAs should not be abandoned at moderate grades of stenosis.     

Does wrapping of the right internal thoracic artery to the left anterior descending artery always protect?

We report about a 72-year-old woman with coronary artery disease. Surgical revascularization was performed using three grafts. One of them was the right internal thoracic artery (RITA) to left anterior descending. This graft was covered by a PRECLUDE IMA Sleeve. Wound healing was impaired and became to a chronic sternal osteomyelitis and mediastinitis. Thirty-three months after the primary operation, the PRECLUDE IMA Sleeve was explanted, the sternum was partially resected and the resulting cavity reconstructed with an omentum flap. During that operation, the RITA bypass was damaged. Interposition of a venous segment was necessary to reconstitute the graft.     

Does skeletonization compromise the integrity of internal thoracic artery grafts?

BACKGROUND: There are few reports that demonstrate the chronologic changes in the functional integrity of the internal thoracic artery (ITA) wall after skeletonization. We investigated the impact of skeletonization on ITA wall integrity by immunohistochemical analyses in acute and chronic phases. METHODS: Nine mongrel dogs underwent bilateral ITA dissection with one skeletonized vessel and the other pedicled. The following studies were performed 1 week (acute phase, n = 3) and 12 weeks (chronic phase, n = 6) after ITA harvesting. All specimens of the ITAs were stained by antibodies against von Willebrand Factor (VWF), endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), and proliferating cell nuclear antigen (PCNA). After observation with confocal laser scanning microscopy, quantitative analyses of the staining signal for VWF and eNOS expressed on endothelial cells were performed. RESULTS: There were significantly more microvessels positive for VWF in the adventitia of skeletonized ITAs than in the adventitia of pedicled ITAs but the expression of PCNA in both groups was minimal, as in normal vessels. iNOS was not detected in any specimen. The intensity of VWF and eNOS expressed by endothelial cells had no significant differences between groups at either phase. CONCLUSIONS: The functional integrity of skeletonized ITA was similar to that of pedicled ITA in both acute and chronic phases. Although skeletonization induced neovascularization in the adventitia it did not induce proliferation of smooth muscle cells in the media, which is supposed to be a feature of vascular remodeling.     

Is the mid-term outcome of free right internal thoracic artery with a proximal anastomosis modification inferior to in situ right internal thoracic artery?

Background

We investigated the mid-term results of free right internal thoracic artery (RITA) grafts used in an aorto-coronary fashion with a modified proximal anastomosis.

Methods

The subjects were 214 patients who underwent coronary artery bypass grafting with anastomosis to the left circumflex arteries using the RITA as a free graft (Group A: 158 patients) or an in situ graft (Group B: 56 patients). In Group A, the proximal end of the free RITA was anastomosed onto the ascending aorta interposing free graft tissue or to part of its own tissue as a cuff.

Results

The number of RITA anastomoses was 1.38?±?0.50 in Group A and 1.04?±?0.19 in Group B (P?P?=?0.159), however, the number of cardiac events was decreased in Group A (Hazard Ratio 2.55, 95?% CI 1.03?C6.33, P?=?0.043). The graft patency was evaluated in 187 of 214 patients, and at 1, 3 and 5?years was 97.0, 97.0 and 97.0?% in Group A, and 97.9, 92.5 and 80.5?% in Group B (P?=?0.378), respectively.

Conclusion

By modifying the proximal anastomosis of the free RITA, cardiac events may be decreased, while survival and graft patency comparable with in situ RITA can be obtained, and a significantly larger number of targets can be revascularized.     

Does bilateral internal thoracic artery harvest increase the risk of mediastinitis?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether bilateral internal thoracic artery (BITA) coronary bypass increases the risk for mediastinitis. Using the reported search 140 papers were identified. Twenty-four papers represented the best evidence on the subject and the author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study comments and weaknesses were tabulated. In general, BITA grafting carries a 2.5- to 5-fold higher risk for mediastinitis after CABG. This risk is about 1.3-4.7% in non-diabetic patients compared to 0.2-1.2% for single internal thoracic artery (SITA) grafting. For diabetic patients with BITA grafting the risk of mediastinitis is significantly increased and can be as high as >10% in some series. However, for patients who undergo BITA harvest using skeletonization the risk is significantly lower and may be similar to patients receiving SITA graft only at around 0.4-2.6%. BITA grafting can be performed with acceptable risk in all patients including higher risk patients such as diabetics, in whom skeletonization of the internal thoracic arteries should be strongly considered rather than pedicled harvest.     

Free right internal thoracic artery composite graft: an option in left anterior descending artery grafting?

Myocardial revascularization using bilateral internal thoracic arteries (ITA) decreases the risk of reinterventions and provides potential survival benefit. From May 1996 to April 2000, 1,057 patients underwent myocardial revascularization using skeletonized bilateral ITAs. A free right ITA as a composite graft was used for the left anterior descending artery grafting in 38 (3.6%) cases when the left ITA was not long enough to reach the left anterior descending artery. Operative mortality was 2.6% (1 patient). There was no observable reversible myocardial ischemia on the postoperative thallium single-photon emission computed tomography study. Myocardial revascularization with the use of a skeletonized free right ITA as a composite graft to the left anterior descending artery is an alternative option in cases when an in situ ITA cannot be used.     

Does the radial artery provide better long-term patency than the saphenous vein?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether the radial artery provides better long-term patency than the saphenous vein. Altogether 379 papers were found using the reported search, of which 12 presented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. We concluded that there is evidence that radial artery grafts have a higher rate of patency than saphenous vein grafts. Surgeons can confidently use the radial artery as a second arterial bypass graft, particularly in patients with severe native-vessel stenosis.     

What is the patency of the short saphenous vein when used for coronary artery bypass grafting?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was what the patency of the short saphenous vein is, when used for coronary artery bypass grafting. Altogether 347 papers were found using the reported search, of which nine represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. We conclude that small reports give a two-year patency of 77% and a six-year patency of 65% and duplex studies show that the short saphenous vein may be from 2.8 mm to 4.2 mm in diameter. However, caution should be applied when considering these patency rates as they are derived from individual studies of <40 patients. The lesser saphenous vein may be considered as an alternative to brachial or cephalic vein in patients with unsuitable long saphenous vein, and unsuitable mammary, radial or gastroepiploic arteries.     

Should the internal thoracic artery be skeletonized?

Traditionally, the internal thoracic artery is harvested as a pedicle. In contemporary cardiac surgical practice, however, certain surgeons practice the internal thoracic artery-skeletonization technique. A systematic review of clinical studies reporting on the use of skeletonized internal thoracic arteries (SKT-ITA) has not yet been performed. The primary aim of this review article is to examine comprehensively the entire body of evidence regarding the use of SKT-ITA. In particular, we aimed to analyze the effects of skeletonization on sternal blood supply, wall damage and blood flow in the harvested vessel, postoperative graft patency, and clinical outcome. Advantages and disadvantages of the skeletonization technique are highlighted and discussed.     

Does minimally invasive vein harvesting technique affect the quality of the conduit for coronary revascularization?

The effect of minimally invasive great saphenous vein harvest on patient morbidity (wound infection and other healing disturbances) has been extensively investigated, yet its impact on the quality of the venous conduit is less well known. This study aims to review the literature with regard to macroscopic quality, postoperative myocardial infarction rates, and angiographic patency of the minimally invasive versus conventionally harvested vein using meta-analytic techniques where appropriate. Results suggest that conduits are comparable in macroscopic quality with minimally invasively harvested veins requiring more repairs prior to grafting. Postoperative myocardial infarction rates were not significantly different between groups, which is supported by the limited evidence on angiographic patency.