Coronary Revascularization With Single Versus Bilateral Mammary Arteries: Is It Time to Change?

BACKGROUND: Arterial conduits are preferred to venous conduits for coronary artery bypass grafting because of longer patency. A single internal mammary artery (SIMA) is used routinely. Bilateral internal mammary arteries (BIMA) are used less frequently. We sought to determine whether BIMA were superior to SIMA. METHODS: From our regional registry of consecutive open heart operations, we identified 47,984 patients who underwent isolated coronary artery bypass grafting from 1992 to 2014. Of the 1,482 BIMA patients, 1,297 were propensity matched to a cohort of SIMA patients. Short-term outcomes were compared using standard statistical techniques. Long-term survival was compared using Kaplan-Meier estimators and compared using a log-rank test. RESULTS: BIMA patients were younger and had fewer comorbid conditions than SIMA patients. After propensity weighting, BIMA and SIMA patients were well matched. There was no difference in in-hospital outcomes for BIMA versus SIMA patients for mortality (1.2% [n = 15] vs 0.8% [n = 10], p = 0.315), stroke (0.7% [n = 9] vs 0.7% [n = 9), p = 1.000), bleeding (2.2% [n = 28] vs 2.8% [n = 36], p = 0.311), or mediastinitis (0.8% [n = 10] vs 0.9% [n = 12], p = 0.667). The median follow-up was 12 years. Survival was better for BIMA than SIMA (adjusted hazard ratio, 0.79; 95% confidence interval, 0.69 to 0.91; p < 0.001). Survival curves began to separate after 5 years. At 15 years, the absolute difference in survival was 8.4%. CONCLUSIONS: In a large regional experience, BIMA is associated with no upfront risk of adverse events and improved long-term survival compared with SIMA. Our results indicate that BIMA conduits should be considered more frequently during coronary artery bypass grafting due to their demonstrated survival advantage.

Should Diabetes Be a Contraindication to Bilateral Internal Mammary Artery Grafting?

BACKGROUND: This study evaluates the influence of bilateral internal mammary artery (BIMA) versus single internal mammary artery (SIMA) grafting on postoperative morbidity and long-term survival among diabetic patients undergoing coronary artery bypass grafting (CABG). METHODS: A multicenter, retrospective analysis of 47,984 consecutive CABGs performed from 1992 to 2014 at 7 medical centers was conducted. Among the study population, 1,482 CABGs with BIMA were identified, and 1,297 BIMA patients were propensity-matched to 1,297 SIMA patients. The study cohort for this analysis, drawn from matched data, included 430 diabetic patients: 217 SIMA and 213 BIMA. The primary endpoint was long-term survival. Secondary endpoints included postoperative morbidity, length of stay, and in-hospital mortality. RESULTS: The median duration of follow-up was 9.3 (range, 4.3 to 13.9) years. Among propensity-matched diabetic patients, there was no significant difference in age, body mass index, or major baseline comorbidities. The groups were also well matched on the number of diseased coronary arteries and number of distal anastomoses performed. There was no difference in the rate of mediastinitis or sternal dehiscence (p = 0.503) or in-hospital mortality (p = 0.758) between groups. Both groups had a similar median length of stay of 5 (range, 4 to 7) days. Diabetic patients who received a BIMA had significantly improved long-term survival when compared with SIMA patients (hazard ratio 0.75 [95% confidence interval 0.57 to 0.98], p = 0.034). CONCLUSIONS: Among diabetics undergoing CABG, use of BIMA grafting does not result in increased in-hospital morbidity or mortality and confers a long-term survival advantage when compared with SIMA grafting. Thus, diabetic patients should be considered for BIMA grafting more frequently.

Does Use of Bilateral Internal Mammary Artery Grafting Reduce Long-Term Risk of Repeat Coronary Revascularization? A Multicenter Analysis.

BACKGROUND: Although previous studies have demonstrated that patients receiving bilateral internal mammary artery (BIMA) conduits during coronary artery bypass grafting have better long-term survival than those receiving a single internal mammary artery (SIMA), data on risk of repeat revascularization are more limited. In this analysis, we compare the timing, frequency, and type of repeat coronary revascularization among patients receiving BIMA and SIMA. METHODS: We conducted a multicenter, retrospective analysis of 47 984 consecutive coronary artery bypass grafting surgeries performed from 1992 to 2014 among 7 medical centers reporting to a prospectively maintained clinical registry. Among the study population, 1482 coronary artery bypass grafting surgeries with BIMA were identified, and 1297 patients receiving BIMA were propensity-matched to 1297 patients receiving SIMA. The primary end point was freedom from repeat coronary revascularization. RESULTS: The median duration of follow-up was 13.2 (IQR, 7.4-17.7) years. Patients were well matched by age, body mass index, major comorbidities, and cardiac function. There was a higher freedom from repeat revascularization among patients receiving BIMA than among patients receiving SIMA (hazard ratio [HR], 0.78 [95% CI, 0.65-0.94]; P=0.009). Among the matched cohort, 19.4% (n=252) of patients receiving SIMA underwent repeat revascularization, whereas this frequency was 15.1% (n=196) among patients receiving BIMA (P=0.004). The majority of repeat revascularization procedures were percutaneous coronary interventions (94.2%), and this did not differ between groups (P=0.274). Groups also did not differ in the ratio of native versus graft vessel percutaneous coronary intervention (P=0.899), or regarding percutaneous coronary intervention target vessels; the most common targets in both groups were the right coronary (P=0.133) and circumflex arteries (P=0.093). In comparison with SIMA, BIMA grafting was associated with a reduction in all-cause mortality at 12 years of follow-up (HR, 0.79 [95% CI, 0.69-0.91]; P=0.001), and there was no difference in in-hospital morbidity. CONCLUSIONS: BIMA grafting was associated with a reduced risk of repeat revascularization and an improvement in long-term survival and should be considered more frequently during coronary artery bypass grafting.

Effect of preoperative pulmonary hypertension on outcomes in patients with severe aortic stenosis following surgical aortic valve replacement.

Pulmonary hypertension (PH) is prevalent in patients with aortic stenosis (AS); however, previous studies have demonstrated inconsistent results regarding the association of PH with adverse outcomes after aortic valve replacement (AVR). The goal of this study was to evaluate the effects of preoperative PH on outcomes after AVR. We performed a regional prospective cohort study using the Northern New England Cardiovascular Disease Study Group database to identify 1,116 consecutive patients from 2005 to 2010 who underwent AVR ± coronary artery bypass grafting for severe AS with a preoperative assessment of pulmonary pressures by right-sided cardiac catheterization. PH was defined as a mean pulmonary artery pressure of ≥25 mm Hg, with severity based on the pulmonary artery systolic pressure-mild, 35 to 44 mm Hg; moderate, 45 to 59 mm Hg; and severe, ≥60 mm Hg. We found that PH was present in 536 patients (48%). Postoperative acute kidney injury, low-output heart failure, and in-hospital mortality increased with worsening severity of PH. In multivariate logistic regression, severe PH was independently associated with postoperative acute kidney injury (adjusted odds ratio 4.1, 95% confidence interval [CI] 1.7 to 10, p = 0.002) and in-hospital mortality (adjusted odds ratio 6.9, 95% CI 2.5 to 19.1, p <0.001). There was a significant association between PH and decreased 5-year survival (adjusted log-rank p value = 0.006), with severe PH being associated with the poorest survival (adjusted hazard ratio 2.4, 95% CI 1.3 to 4.2, p = 0.003). In conclusion, severe PH in patients with severe AS is associated with increased rates of in-hospital adverse events and decreased 5-year survival after AVR.

Long-term outcomes of endoscopic vein harvesting after coronary artery bypass grafting.

BACKGROUND: Use of endoscopic saphenous vein harvesting has developed into a routine surgical approach at many cardiothoracic surgical centers. The association between this technique and long-term morbidity and mortality has recently been called into question. The present report describes the use of open versus endoscopic vein harvesting and risk of mortality and repeat revascularization in northern New England during a time period (2001 to 2004) in which both techniques were being performed. METHODS AND RESULTS: From 2001 to 2004, 8542 patients underwent isolated coronary artery bypass grafting procedures, 52.5% with endoscopic vein harvesting. Surgical discretion dictated the vein harvest approach. The main outcomes were death and repeat revascularization (percutaneous coronary intervention or coronary artery bypass grafting) within 4 years of the index admission. The use of endoscopic vein harvesting increased from 34% in 2001 to 75% in 2004. In general, patients undergoing endoscopic vein harvesting had greater disease burden. Endoscopic vein harvesting was associated with an increased adjusted risk of bleeding requiring a return to the operating room (2.4 versus 1.7; P=0.03) but a decreased risk of leg wound infections (0.2 versus 1.1; P<0.001). Use of endoscopic vein harvesting was associated with a significant reduction in long-term mortality (adjusted hazard ratio, 0.74; 95% confidence interval, 0.60 to 0.92) but a nonsignificant increased risk of repeat revascularization (adjusted hazard ratio, 1.29; 95% confidence interval, 0.96 to 1.74). Similar results were obtained in propensity-stratified analysis. CONCLUSIONS: During 2001 to 2004 in northern New England, the use of endoscopic vein harvesting was not associated with harm. There was a nonsignificant increase in repeat revascularization, and survival was not decreased.

Cerebrovascular response to continuous cold perfusion and hypothermic circulatory arrest.

OBJECTIVE: Clinical and laboratory studies have documented changes in cerebrovascular resistance after hypothermic circulatory arrest, both with and without adjunctive cerebral perfusion modalities. This study was designed to clarify whether these changes are due to cerebral edema, resistance vessel abnormalities, or alterations in the cerebral microcirculation. METHODS: Four mature swine underwent hypothermic circulatory arrest for 60 minutes, and 7 mature swine underwent cold cerebral perfusion for 60 minutes to simulate antegrade selective perfusion. All were rewarmed and weaned from cardiopulmonary bypass. Pial vascular diameter and reactivity were measured in vivo through a cranial window and ex vivo in an organ chamber; cerebral microvascular endothelium was studied in culture for release of vasoactive mediators. Cerebral water content was recorded. RESULTS: Cold perfusion caused pial arteriole and venule constriction, whereas hypothermic circulatory arrest alone caused pial arteriole and venule dilatation. Cold perfusion caused a temporal loss of endothelium-dependent vasodilatation, most notably to bradykinin. Hypothermic circulatory arrest caused a loss of nitric oxide-mediated endothelium-dependent vasodilatation. Endothelium-independent vasoreactivity remained intact in both groups. Endothelial cells from the cold group had a vasoconstrictive secretory phenotype, whereas endothelial cells from the hypothermic circulatory arrest group had a vasodilatory phenotype. Cerebral water content was the same in both groups. CONCLUSION: The increase in cerebrovascular resistance observed after cold cerebral perfusion is caused by resistance vessel constriction and may be promoted by an altered microcirculation. Hypothermic circulatory arrest alone is associated with endothelium-dependent vasoparesis. Both could contribute to cerebral injury in the early hours after operation.

A novel model of blunt thoracic aortic injury: a mechanism confirmed?

BACKGROUND: There is no consensus on the mechanism of traumatic injury to the thoracic aorta and no reproducible animal model. Advances in injury scene analysis suggest that lateral and oblique force vectors cause aortic injury. We hypothesized that the spectrum of aortic injury could be reproduced in an animal model by application of an obliquely directed load to the pressurized aorta. METHODS: Graded air impulses of 80, 100, 110, and 120 pounds per square inch (PSI) were delivered to the descending thoracic aorta of 19 swine with a novel pneumatic device. Aortic isthmus strain was recorded with microminiature probes. Gross and microscopic injury was recorded with digital photography. RESULTS: The spectrum of human aortic injury was reproduced in this model. Deep injuries to the aortic media were common. The majority of injuries occurred within the region of the isthmus. Impulse pressure of 120 PSI caused transections, whereas lower impulse pressure resulted in less severe injuries. Aortic isthmus strain was greater in the animals exposed to 120 PSI than those receiving lower PSI (19.6 +/- 4.9% vs. 8.7 +/- 2.5%, p = 0.067). CONCLUSIONS: Direct loading of the pressurized descending thoracic aorta causes isthmus injury secondary to aortic wall strain. Deep medial lesions are common and could propagate soon after injury to form pseudoaneurysms. A critical load is required to cause complete uncontained transection with exsanguination, which may have relevance to injury scene death.

Matrix metalloproteinase and tissue inhibitor expression in atherosclerotic and nonatherosclerotic thoracic aortic aneurysms.

OBJECTIVES: The altered expression of matrix metalloproteinases and their inhibitors influences the formation of atherosclerotic abdominal aortic aneurysms. Their association with thoracic aneurysms is less clear. This study describes the expression of metalloproteinases and their inhibitors in atherosclerotic and nonatherosclerotic thoracic aneurysms, and compares these with age-matched controls. METHODS: Matrix metalloproteinase-2 and 9 activity were measured by antibody capture, and tissue inhibitor-1 and 2 levels were measured by enzyme-linked immunosorbent assay in 24 patients with atherosclerotic aneurysms and in 63 patients with nonatherosclerotic aneurysms. Gene expression was assessed with reverse transcriptase polymerase chain reaction. The results were compared with 17 controls. RESULTS: Data are in nanograms per milligram of protein. Matrix metalloproteinase-2 activity was greater in controls than in the atherosclerotic and nonatherosclerotic groups (80 +/- 67 vs 49 +/- 50 and 35 +/- 44, P = .002). Matrix metalloproteinase-9 activity was greater in the atherosclerotic group than in the nonatherosclerotic group and controls (11.7 +/- 15.7 vs 2.5 +/- 2.2 and 1.7 +/- 1.9, P = .001). Tissue inhibitor-1 and 2 levels were greater in controls than in either aneurysm group (tissue inhibitor of metalloproteinase-1: 376 +/- 192 vs 234 +/- 233 and 174 +/- 148, P = .003; tissue inhibitor of metalloproteinase-2: 143 +/- 74 vs 14 +/- 13 and 27 +/- 43, P < .001). Atherosclerotic aneurysms expressed more matrix metalloproteinase mRNA than controls. CONCLUSIONS: The metalloproteinase/tissue inhibitor phenotype of atherosclerotic thoracic aneurysms is similar to that of abdominal aneurysms. The diminished expression of metalloproteinases and tissue inhibitors in nonatherosclerotic thoracic aneurysms relative to aged controls may represent a loss of smooth muscle cells.

Matrix metalloproteinase activity in thoracic aortic aneurysms associated with bicuspid and tricuspid aortic valves.

OBJECTIVE: Matrix metalloproteinases are endopeptidases that function in cell matrix turnover. Abnormal matrix metalloproteinase activity has been implicated in the formation of atherosclerotic abdominal aortic aneurysms. Recent studies suggest that abnormal matrix metalloproteinase activity may also be associated with the formation of atherosclerotic and nonatherosclerotic thoracic aortic aneurysms. Bicuspid aortic valves are associated with an intrinsic aortic pathology that predisposes to formation of proximal thoracic aneurysms while tricuspid aortic valves are not. The objective of this study was to compare the activities of matrix metalloproteinases and levels of their inhibitors in thoracic aneurysms of patients with bicuspid and tricuspid aortic valves. METHODS: Endogenous and total activity of matrix metalloproteinase-2 and matrix metalloproteinase-9 were measured in proximal nonatherosclerotic thoracic aortic aneurysms of 16 patients with bicuspid aortic valves and 12 patients with tricuspid aortic valves. Levels of tissue inhibitor metalloproteinase-1 and -2 were also measured. Results were standardized to total protein (mg). RESULTS: Total matrix metalloproteinase-2 activity was greater in aneurysms associated with bicuspid valves when compared with those from tricuspid valves (43 +/- 11 ng/mg vs 14 +/- 2 ng/mg, P =.02). Total matrix metalloproteinase-9 activity was also greater in aneurysms associated with bicuspid aortic valves (4.0 +/- 0.9 vs 1.5 +/- 0.3, P =.02). There was no meaningful difference between groups in levels of tissue inhibitor-1 and -2. CONCLUSION: The increased activity of matrix metalloproteinases in the walls of aneurysms associated with bicuspid aortic valves may partly explain the predilection to aneurysm formation in these patients.

A simple trick for repairing coronary pseudoaneurysm complicating a Bentall operation.

Coronary pseudoaneurysms are a known complication of the Bentall wrap-inclusion method of composite valve grafting. We describe two cases to illustrate a straightforward technique for repair and prevention of coronary pseudoaneurysm formation.