Benjamin M. Westbrook

Intraoperative Red Blood Cell Transfusion During Coronary Artery Bypass Graft Surgery Increases the Risk of Postoperative Low-Output Heart Failure

Background— Hemodilutional anemia during cardiopulmonary bypass (CPB) is associated with increased mortality during coronary artery bypass graft (CABG) surgery. The impact of intraoperative red blood cell (RBC) transfusion to treat anemia during surgery is less understood. We examined the relationship between anemia during CPB, RBC transfusion, and risk of low-output heart failure (LOF). Methods and Results— Data were collected on 8004 isolated CABG patients in northern New England between 1996 and 2004. Patients were excluded if they experienced postoperative bleeding or received ≥3 units of transfused RBCs. LOF was defined as need for intraoperative or postoperative intra-aortic balloon pump, return to CPB, or ≥2 inotropes at 48 hours. Having a lower nadir HCT was also associated with an increased risk of developing LOF (adjusted odds ratio, 0.90; 95% CI, 0.82 to 0.92; P=0.016), and that risk was further increased when patients received RBC transfusion. When adjusted for nadir hematocrit, exposure to RBC transfusion was a significant, independent predictor of LOF (adjusted odds ratio, 1.27; 95% CI, 1.00 to 1.61; P=0.047). Conclusions— In this study, we observed that exposure to both hemodilutional anemia and RBC transfusion during surgery are associated with increased risk of LOF, defined as placement of an intraoperative or postoperative intra-aortic balloon pump, return to CPB after initial separation, or treatment with ≥2 inotropes at 48 hours postoperatively, after CABG. The risk of LOF is greater among patients exposed to intraoperative RBCs versus anemia alone.

In-hospital outcomes of off-pump versus on-pump coronary artery bypass procedures: a multicenter experience ☆

BACKGROUND Concern about the possible adverse effects of the cardiopulmonary bypass (CPB) pump and advances in retractors and operative techniques to access all coronary segments have resulted in increased interest in off-pump coronary artery bypass (OPCAB) procedures. Four of the Northern New England Cardiovascular Disease Study Group centers initiated OPCAB programs in 1998. We compared the preoperative risk profiles and in-hospital outcomes of patients done off-pump with those done by conventional coronary artery bypass (CCAB) with CPB. METHODS Between 1998 and 2000, 1,741 OPCAB and 6,126 CCAB procedures were performed at these four medical centers. Minimally invasive direct coronary artery bypass grafting procedures were excluded. Data were available for patient and disease risk factors, extent of coronary disease and adverse in-hospital outcomes. RESULTS The OPCAB and CCAB groups were somewhat different in their preoperative patient and disease characteristics. The OPCAB patients were more likely to be female and to have peripheral vascular disease. The CCAB patients were more likely to have an ejection fraction less than 0.40 and be urgent or emergent at operation. However, overall predicted risk of in-hospital mortality, based on preoperative factors, was similar in the OPCAB and CCAB groups; the mean predicted risk was 2.6% (p = 0.567). Crude rates of mortality (2.54% OPCAB versus 2.57%, CCAB), intraoperative or postoperative stroke (1.33% versus 1.82%), mediastinitis (1.10% versus 1.37%), and return to the operating room for bleeding (3.46% versus 2.93%) did not differ significantly. The OPCAB patients did have a statistically significant reduction in the need for intraoperative or postoperative intraaortic balloon pump support (2.31% versus 3.41%; p = 0.023) and in the incidence of postoperative atrial fibrillation (21.21% versus 26.31%; p < 0.001). Adjustment for preoperative risk factors and extent of coronary disease did not substantially change the crude results. Median postoperative length of stay was significantly shorter (5 days versus 6 days, p < 0.001) for OPCAB patients than for CCAB patients. CONCLUSIONS This multicenter study showed that patients having OPCAB are not exposed to a greater risk of short-term adverse outcomes. These data also provided evidence that patients having OPCAB have significantly lower need for intraoperative or postoperative intraaortic balloon pump, lower rates of postoperative atrial fibrillation, and a shorter length of stay.

Multivariable Prediction of Renal Insufficiency Developing After Cardiac Surgery

Background— Renal insufficiency after coronary artery bypass graft (CABG) surgery is associated with increased short-term and long-term mortality. We hypothesized that preoperative patient characteristics could be used to predict the patient-specific risk of developing postoperative renal insufficiency. Methods and Results— Data were prospectively collected on 11 301 patients in northern New England who underwent isolated CABG surgery between 2001 and 2005. Based on National Kidney Foundation definitions, moderate renal insufficiency was defined as a GFR <60 mL/min/1.73m2 and severe renal insufficiency as a GFR <30. Patients with at least moderate renal insufficiency at baseline were eliminated from the analysis, leaving 8363 patients who became our study cohort. A prediction model was developed to identify variables that best predicted the risk of developing severe renal insufficiency using multiple logistic regression, and the predictive ability of the model quantified using a bootstrap validated C-Index (Area Under ROC) and Hosmer-Lemeshow statistic. Three percent of the patients with normal renal function before CABG surgery developed severe renal insufficiency (229/8363). In a multivariable model the preoperative patient characteristics most strongly associated with postoperative severe renal insufficiency included: age, gender, white blood cell count >12 000, prior CABG, congestive heart failure, peripheral vascular disease, diabetes, hypertension, and preoperative intraaortic balloon pump. The predictive model was significant with &khgr;2 150.8, probability value <0.0001. The model discriminated well, ROC 0.72 (95%CI: 0.68 to 0.75). The model was well calibrated according to the Hosmer-Lemeshow test. Conclusions— We developed a robust prediction rule to assist clinicians in identifying patients with normal, or near normal, preoperative renal function who are at high risk of developing severe renal insufficiency. Physicians may be able to take steps to limit this adverse outcome and its associated increase in morbidity and mortality.

Arterial inflow via an axillary artery graft for the severely atheromatous aorta

BACKGROUND Strategy for severe aortic atheromatous disease identified by intraoperative epiaortic ultrasound remains to be determined. We used axillary artery inflow through graft interposition in an attempt to avoid potential embolization. METHODS Between July 1995 and June 1997, axillary artery inflow was used in 29 patients. Procedures performed were coronary artery bypass in 21 patients (3 with combined carotid endarterectomy), aortic valve replacement in 2, valve replacement plus coronary artery bypass in 4, atrial septal defect repair in 1, and arch replacement in 1 patient. Fibrillatory arrest was used in 16 patients and circulatory arrest was used in 16 patients for excision of mobile atheroma or arch reconstruction. Antegrade cerebral perfusion through the axillary artery graft was carried out in 11 patients. RESULTS There were no brachial neurovascular complications. Two operative deaths occurred. Two patients had operative strokes and 2 more had postoperative stroke, all with resolution at late follow-up. There were no strokes in the subset of patients who had antegrade cerebral perfusion during circulatory arrest. CONCLUSION The axillary artery is an excellent site for arterial inflow. Furthermore, antegrade cerebral perfusion is easily accomplished during periods of circulatory arrest. Finally, graft placement avoids potential local neurovascular complications.

Trends in Rates of Reexploration for Hemorrhage After Coronary Artery Bypass Surgery

BACKGROUND While mortality rates associated with coronary artery bypass grafting (CABG) have been declining, it is unknown whether similar improvements in the rates of morbidity have been occurring. This study examines trends in reexploration rates for hemorrhage, one of the serious complications of CABG surgery. It also explores changes in patient characteristics and several surgeon practice patterns potentially related to bleeding risks that may explain variations in these rates. METHODS We performed a regional observational study of all of the 12,555 consecutive patients undergoing isolated CABG surgery in northern New England between 1992 and 1997. The rates of reexploration and patient characteristics were examined between two time intervals: period I (January 1, 1992 to June 1, 1994) and period II (June 1, 1995 to March 31, 1997). All of the regions 23 practicing surgeons responsible for these patients were surveyed to assess changes in practice patterns potentially related to bleeding risks. RESULTS The adjusted rates of reexploration for bleeding declined 46% between periods I and II (3.6% versus 2.0%, p < 0.001). All of the five cardiac centers in northern New England showed similar trends with adjusted risk reductions ranging from 32% to 48% between the two time periods. This decline occurred despite the patients in period II having higher percentages of risk factors for reexploration for bleeding compared to patients in period I. From the surgeon survey, the number of surgeons using antifibrinolytics markedly increased from period I to period II. More surgeons were also using preoperative aspirin and heparin up until the time of surgery in period II. CONCLUSIONS Similar to the rates of mortality, the rates of reexploration for bleeding following CABG surgery are substantially declining. This decrease in the reexploration rates occurred despite higher patient risks.

Impact of perioperative acute kidney injury as a severity index for thirty-day readmission after cardiac surgery.

BACKGROUND Of patients undergoing cardiac surgery in the United States, 15% to 20% are re-hospitalized within 30 days. Current models to predict readmission have not evaluated the association between severity of postoperative acute kidney injury (AKI) and 30-day readmissions. METHODS We collected data from 2,209 consecutive patients who underwent either coronary artery bypass or valve surgery at 7 member hospitals of the Northern New England Cardiovascular Disease Study Group Cardiac Surgery Registry between July 2008 and December 2010. Administrative data at each hospital were searched to identify all patients readmitted to the index hospital within 30 days of discharge. We defined AKI stages by the AKI Network definition of 0.3 or 50% increase (stage 1), twofold increase (stage 2), and a threefold or 0.5 increase if the baseline serum creatinine was at least 4.0 (mg/dL) or new dialysis (stage 3). We evaluate the association between stages of AKI and 30-day readmission using multivariate logistic regression. RESULTS There were 260 patients readmitted within 30 days (12.1%). The median time to readmission was 9 (interquartile range, 4 to 16) days. Patients not developing AKI after cardiac surgery had a 30-day readmission rate of 9.3% compared with patients developing AKI stage 1 (16.1%), AKI stage 2 (21.8%), and AKI stage 3 (28.6%, p < 0.001). Adjusted odds ratios for AKI stage 1 (1.81; 1.35, 2.44), stage 2 (2.39; 1.38, 4.14), and stage 3 (3.47; 1.85 to 6.50). Models to predict readmission were significantly improved with the addition of AKI stage (c-statistic 0.65, p = 0.001) and net reclassification rate of 14.6% (95% confidence interval: 5.05% to 24.14%, p = 0.003). CONCLUSIONS In addition to more traditional patient characteristics, the severity of postoperative AKI should be used when assessing a patients risk for readmission.

Preoperative white blood cell count and mortality and morbidity after coronary artery bypass grafting

BACKGROUND Arteriosclerosis is increasingly viewed as an inflammatory disease. The purpose of these analyses was to examine the preoperative white blood cell (WBC) count, a generalized marker of inflammation, and to assess its association with in-hospital mortality and other adverse outcomes after coronary artery bypass grafting. METHODS Information was collected prospectively on 11,270 consecutive patients who had isolated coronary artery bypass grafting in northern New England from 1996 through 2000. Patients were divided into five categories based on their preoperative WBC count. Crude and adjusted in-hospital mortality rates and adverse event rates were calculated using logistic regression. RESULTS Increasing WBC count across its entire range was associated with a linear increase in the mortality rate. This finding was highly significant (p [trend] < 0.001) and persisted after adjustment for patient and disease characteristics. Patients with preoperative WBC of at least 12.0 x 10(9)/L had an adjusted mortality rate 2.8 times higher than those with a WBC less than 6.0 x 10(9)/L (4.8% versus 1.7%). An increasing preoperative WBC count was also significantly associated with increasing rates of perioperative strokes and the need for an intraaortic balloon pump but was not associated with mediastinitis. CONCLUSIONS The preoperative WBC count across its entire observed range is a statistically significant independent predictor of in-hospital death and other adverse outcomes after coronary artery bypass grafting. Although the cause of the association between increased WBC count and increased morbidity and mortality is unknown, the preoperative WBC count, which is objectively measured, inexpensive, and always available, can serve as a useful marker to help predict risk before coronary artery bypass grafting.

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.

Preoperative White Blood Cell Count and Risk of 30-Day Readmission after Cardiac Surgery

Approximately 1 in 5 patients undergoing cardiac surgery are readmitted within 30 days of discharge. Among the primary causes of readmission are infection and disease states susceptible to the inflammatory cascade, such as diabetes, chronic obstructive pulmonary disease, and gastrointestinal complications. Currently, it is not known if a patients baseline inflammatory state measured by crude white blood cell (WBC) counts could predict 30-day readmission. We collected data from 2,176 consecutive patients who underwent cardiac surgery at seven hospitals. Patient readmission data was abstracted from each hospital. The independent association with preoperative WBC count was determined using logistic regression. There were 259 patients readmitted within 30 days, with a median time of readmission of 9 days (IQR 4–16). Patients with elevated WBC count at baseline (10,000–12,000 and >12,000 mm3) had higher 30-day readmission than those with lower levels of WBC count prior to surgery (15% and 18% compared to 10%–12%, P = 0.037). Adjusted odds ratios were 1.42 (0.86, 2.34) for WBC counts 10,000–12,000 and 1.81 (1.03, 3.17) for WBC count > 12,000. We conclude that WBC count measured prior to cardiac surgery as a measure of the patients inflammatory state could aid clinicians and continuity of care management teams in identifying patients at heightened risk of 30-day readmission after discharge from cardiac surgery.

Regional use of combined carotid endarterectomy/coronary artery bypass graft and the effect of patient risk

INTRODUCTION Although carotid artery stenosis and coronary artery disease often coexist, many debate which patients are best served by combined concurrent revascularization (carotid endarterectomy [CEA]/coronary artery bypass graft [CABG]). We studied the use of CEA/CABG in New England and compared indications and outcomes, including stratification by risk, symptoms, and performing center. METHODS Using data from the Vascular Study Group of New England from 2003 to 2009, we studied all patients who underwent combined CEA/CABG across six centers in New England. Our main outcome measure was in-hospital stroke or death. We compared outcomes between all patients undergoing combined CEA/CABG to a baseline CEA risk group comprised of patients undergoing isolated CEA at non-CEA/CABG centers. Further, we compared in-hospital stroke and death rates between high and low neurologic risk patients, defining high neurologic risk patients as those who had at least one of the following clinical or anatomic features: (1) symptomatic carotid disease, (2) bilateral carotid stenosis >70%, (3) ipsilateral stenosis >70% and contralateral occlusion, or (4) ipsilateral or bilateral occlusion. RESULTS Overall, compared to patients undergoing isolated CEA at non-CEA/CABG centers (n = 1563), patients undergoing CEA/CABG (n = 109) were more likely to have diabetes (44% vs 29%; P = .001), creatinine >1.8 mg/dL (11% vs 5%; P = .007), and congestive heart failure (23% vs 10%; P < .001). Patients undergoing CEA/CABG were also more likely to take preoperative beta-blockers (94% vs 75%; P < .001) and less likely to take preoperative clopidogrel (7% vs 25%; P < .001). Patients undergoing CEA/CABG had higher rates of contralateral carotid occlusion (13% vs 5%; P = .001) and were more likely to undergo an urgent/emergent procedure (30% vs 15%; P < .001). The risk of complications was higher in CEA/CABG compared to isolated CEA, including increased risk of stroke (5.5% vs 1.2%; P < .001), death (5.5% vs 0.3%; P < .001), and return to the operating room for any reason (7.6% vs 1.2%; P < .001). Of 109 patients undergoing CEA/CABG, 61 (56%) were low neurologic risk and 48 (44%) were high neurologic risk but showed no demonstrable difference in stroke (4.9% vs 6.3%; P = .76), death, (4.9 vs 6.3%; P = .76), or return to the operating room (10.2% vs 4.3%; P = .25). CONCLUSIONS Although practice patterns in the use of CEA/CABG vary across our region, the risk of complications with CEA/CABG remains significantly higher than in isolated CEA. Future work to improve patient selection in CEA/CABG is needed to improve perioperative results with combined coronary and carotid revascularization.