Xiumei Sun

Silent Brain Injury After Cardiac Surgery: A Review: Cognitive Dysfunction and Magnetic Resonance Imaging Diffusion-Weighted Imaging Findings

The appearance of cognitive dysfunction after cardiac surgery in the absence of focal neurologic signs, a poorly understood but potentially devastating complication, almost certainly results from procedure-related brain injury. Confirmation of the occurrence of perioperative silent brain injury has been developed through advances in magnetic resonance imaging (MRI) techniques. These techniques detect new brain lesions in 25% to 50% of patients after both coronary artery bypass graft and valve surgery. Use of post-operative cognitive dysfunction as a marker of brain injury is problematic because of potential difficulties in ascertainment. It can be hypothesized that post-operative appearance of MRI lesions may serve as a more objective marker of brain injury in research efforts. If MRI examination can be used in this way, then 2 vitally important questions can be addressed. 1) What is the frequency of important, but silent, brain injury during cardiac surgery? 2) Does long-term cognitive impairment ensue? This review briefly discusses clinical features of post-operative cognitive dysfunction and reviews the evidence supporting a possible association with MRI evidence of perioperative brain injury and its potential for long-term dementia. We conclude that this association is plausible, but not yet firmly established.

Is incidence of postoperative vasoplegic syndrome different between off-pump and on-pump coronary artery bypass grafting surgery?

OBJECTIVE Postoperative vasoplegic syndrome (PVS) is a potentially lethal condition with increased mortality and other postoperative morbidities. Many previous studies have examined the outcomes associated with on-pump coronary artery bypass grafting (CABG) surgery, little is known about the incidence of PVS after off-pump CABG. METHODS From November 21, 2005 to June 9, 2006, 334 patients underwent isolated on-pump CABG and 362 had off-pump CABG surgery. Perioperative variables were retrospectively compared between on-pump and off-pump CABG surgery using univariate analysis. Significant variables were included into a stepwise regression model to ascertain their independent impact on the incidence of PVS. RESULTS The incidence of PVS in isolated on-pump CABG was 6.9%; in off-pump CABG was 2.8% (p=0.01). However, in multivariable models adjusted for confounders, on-pump CABG did not reach statistical significance as a risk factor of PVS (OR=2.3, 95% CI 0.94-5.78; p=0.07). In on-pump CABG, preoperative left ventricular EF less than 35% (OR=3.6; p=0.02) and increased body mass index (OR=1.1; p=0.04) were identified as risk predictors of PVS; whereas elective surgery (OR=0.2; p=0.02) and preoperative use of beta-blockers (OR=0.21; p=0.02) were associated with a decreased rate of PVS. PVS was associated with longer ICU stay (OR=6.0; p<0.01), postoperative ventilation (OR=4.6; p<0.01), and hospital stay (OR=2.62; p=0.03). There was a stronger association between preoperative ACE inhibitors therapy and increased risk of PVS in off-pump CABG surgery (OR=4.52, 95% CI 0.95-21.67; p=0.06) than in on-pump CABG surgery (OR=1.06, 95% CI 0.35-3.19; p=0.91), but neither of them reaches statistical significance. CONCLUSIONS The incidence of PVS after off-pump CABG surgery was significantly lower than after on-pump CABG surgery.

Is Cardiac Surgery Safe in Extremely Obese Patients (Body Mass Index 50 or Greater)

BACKGROUND We investigated the impact of extreme obesity (body mass index [kg/m(2)] 50 or greater) on short-term clinical outcomes and report 1-year mortality. METHODS Fifty-seven patients were found to have a body mass index of 50 or greater among 14,449 patients who underwent cardiac surgery between July 2000 and June 2007. Multivariable logistic regression analyses were used to assess the independent influence of extreme obesity on the major outcomes. RESULTS Of the 57 patients, the mean age was 58 +/- 11 years, mean body mass index was 55.1, and 63% of the patients were women. Forty patients underwent elective surgery. Forty-one patients had isolated coronary artery bypass graft surgery. The overall operative mortality was 9%; the mortality was 5% in isolated coronary artery bypass graft surgery and 5% in elective surgery. Fifteen patients had nonelective isolated coronary artery bypass graft surgery, and 2 patients had emergent active endocarditis surgery. Off-pump coronary artery bypass graft surgery was performed on 23 patients (23 of 41, 54%). After adjusting for known preoperative and operative risk factors through a multivariate logistic model, extreme obesity did not emerge as a significant risk factor for operative mortality (odds ratio, 1.75; p = 0.47) and other adverse outcomes (p > 0.05) after elective surgery; however, extreme obesity was marginally associated with increased mortality (odds ratio, 2.69; p = 0.05) and was a risk predictor for longer intensive care unit stays (odds ratio, 2.43; p = 0.01) in overall surgery. The 1-year survival rate was 82.5%. CONCLUSIONS Extreme obesity is not a contraindication to elective cardiac surgery. Studies stratifying the risk factors of mortality for nonelective surgery in extremely obese patients may be warranted.

Off-pump coronary artery bypass grafting improves in-hospital mortality in patients with dialysis-dependent renal failure

OBJECTIVE Patients with chronic dialysis-dependent end-stage renal disease are increasingly referred for coronary artery bypass grafting (CABG) and their early outcome is less favorable. Off-pump CABG (OPCAB) has achieved encouraging results in high-risk patients. Therefore, we designed this retrospective study to test the hypothesis that OPCAB reduced surgical risks in dialysis patients. METHODS From January 2000 to December 2005, 294 dialysis-dependent patients received isolated CABG at the Washington Hospital Center. Among them, 168 underwent OPCAB (off-pump group), and 126, CABG with cardiopulmonary bypass (CPB) (on-pump group). The in-hospital outcomes were analyzed. RESULTS The two groups were comparable in terms of preoperative characteristics. The Parsonnets Bedside Score of the off-pump group was similar to that of the on-pump group (32.0 vs. 32.0, P=.57). The in-hospital mortality of the off-pump group was significantly lower than that of the on-pump group (5.4% vs. 11.9%, P=.04). Although the percentage of patients who received transfusions was similar, the on-pump group received more total transfusions. Logistic regression analysis revealed that use of CPB independently predicted in-hospital mortality [odds ratio (OR), 5.0; 95% confidence interval, 1.78-13.85; P<.01] and perioperative myocardial infarction (MI; OR, 5.1; 95% confidence interval, 1.18-22.40; P=.03). No significant difference in long-term survival at 4 years was absorbed between the two groups of hospital survivors. CONCLUSIONS Our data suggest that OPCAB is a safe alternative to on-pump CABG in dialysis patients. Avoiding CPB resulted in less perioperative blood utilization, MI, and hospital mortality.

Comparison of Frequency of Atrial Fibrillation After Coronary Artery Bypass Grafting in African Americans Versus European Americans

In the general population, African Americans experience atrial fibrillation (AF) less frequently than European Americans. This difference could also exist in the incidence of this arrhythmia after cardiac surgery, but this possibility has been insufficiently examined. To test the association of such an ethnic difference, we compared the incidence of postoperative AF in a consecutive series of 2,312 African Americans and 6,054 European Americans who underwent isolated coronary artery bypass grafting from July 2000 to June 2007. Raw differences between the cohorts in the incidence of new AF were adjusted to take into account the baseline differences. Postoperatively, new-onset AF developed in 504 (22%) of 2,312 African-American patients and in 1,838 (30%) of 6,054 European-American patients (p <0.01). After adjustment with logistic regression analysis for numerous baseline differences, African Americans remained less likely to develop AF (odds ratio 0.63, 95% confidence interval 0.55 to 0.72; p <0.001). Risk was also adjusted using propensity matching. In that analysis, 457 (22%) of 2,059 African-American patients had postoperative AF, as did 597 (29%) of 2,059 matched European-American patients (p <0.01). In conclusion, AF was significantly less common among African-American patients than among European-American patients after coronary artery bypass grafting.

Mortality Predicted by Preinduction Cerebral Oxygen Saturation After Cardiac Operation

BACKGROUND An intraoperative decline in regional cerebral oxygen saturation (rSO2) has been associated with postoperative injury to the central nervous system. Wide individual variation in steady-state cerebral oxygen saturation limits the clinical use of rSO2 to monitoring during anesthesia and surgical procedures. Recently, low preoperative rSO2 has been proposed as a predictor of adverse postoperative outcomes in cardiovascular operations. We compared the sensitivity and specificity of preinduction rSO2 as a predictor of adverse operative events and compared this to the widely accepted risk index developed by the Society for Thoracic Surgeons. METHODS 2,097 consecutive white patients who underwent cardiac operations from 2010 through 2012 were included. In 1,496 patients (group 1) the preinduction rSO2 was equal to or greater than 60%, whereas in the remaining 601 patients (group 2) it was below 60%. We compared the predictive accuracy of preinduction rSO2 with that of the STS mortality risk score by means of standard statistical techniques, including a receiver operating curve characteristic analysis. RESULTS Patients with a preinduction rSO2 below 60% had significantly higher STS mortality risk scores than did patients with an rSO2 equal to or greater than 60% (2.0 vs 4.0, p<0.001). Those with an rSO2 below 60% experienced higher operative mortality (p<0.001) and after adjustment this determination emerged as an independent predictor of increased mortality (p<0.001). Receiver operating characteristic curve analysis demonstrated that the rSO2 was slightly less accurate as a mortality predictor (area under the curve: 0.71 vs 0.85). CONCLUSIONS Measurement of rSO2 is considerably less complex than calculation of the STS score and is only slightly less accurate as a predictor of operative mortality. It may be useful when the STS mortality risk score cannot be calculated.

Is vasoplegic syndrome more prevalent with open-heart procedures compared with isolated on-pump CABG surgery?

Postoperative vasoplegic syndrome (PVS) is a frequent complication and can affect the early postoperative course. Our study investigated the incidence and risk factors of PVS after on-pump isolated coronary artery grafting bypass (CABG) and on-pump open-heart surgery. A total of 629 patients underwent on-pump cardiac surgery from November 21, 2005, to June 9, 2006, at our institution. Of those, 334 patients underwent on-pump isolated CABG and 295 patients had open-heart surgery. PVS was defined based on the recognized criteria. Multivariate logistic regression analysis was used to identify the risk factors for PVS. The overall incidence of PVS was 11.7%. The incidence in isolated on-pump CABG surgery was 6.9% and 17.0% in open-heart surgery (P<.01). In multivariate analysis, isolated CABG reduced by half the incidence of PVS [odds ratio (OR)=0.45, P=.02]; preoperative left ventricular ejection fraction (EF) <35% was identified as an independent predictor of PVS (OR=2.1, P=.01), and a protective effect of female gender for PVS was observed (OR=0.4, P=.01). The association between angiotensin-converting enzyme inhibitors and other preoperative medical treatments was not confirmed by our study. In conclusion, PVS occurred less often after isolated CABG surgery than after open-heart surgery. Advanced age and low preoperative EF strongly predicted PVS.

Early readmission of low-risk patients after coronary surgery.

BACKGROUND Early readmission after coronary artery bypass grafting (CABG) is an expensive adverse outcome. Although the perioperative experience of high-risk CABG patients has been studied extensively, little attention has been paid to low-risk CABG patients. The primary goal of this study was to identify the preoperative characteristics and to define risk predictors of readmission and preventive factors for readmission in low-risk isolated-CABG patients. METHODS We identified 2157 patients who underwent CABG between January 2000 and December 2005 at Washington Hospital Center, Washington, DC, and defined as low risk patients who had a Parsonnet bedside risk score lower than the 25th percentile. Patients who were rehospitalized within 30 days after surgery were compared with those who were not rehospitalized during this period. RESULTS The overall readmission rate for this study cohort was 6.3%. Compared with non-readmitted patients, early-readmitted patients were more likely to have diabetes mellitus (27.94% versus 20.88%, P = .05) and less likely to have hypertension (42.65% versus 51.36%, P = .05). Blood product transfusion (P < .01), postoperative length of intensive care unit stay (P = .01), and length of hospital stay (P = .05) were all significantly increased in the readmitted patients. The use of beta-blockers (P = .03) and angiotensin-converting enzyme inhibitors (P = .04) was significantly lower at discharge in this group of patients; however, multivariate regression analysis demonstrated diabetes (odds ratio, 1.59; 95% confidence interval, 1.08-2.42) to be the only independent predictor of early readmission. CONCLUSIONS For low-risk CABG patients, diabetes mellitus is the risk predictor of early readmission. Early discharge was not associated with early readmission.

Heparin-Induced Thrombocytopenia in Contemporary Cardiac Surgical Practice and Experience With a Protocol for Early Identification

This analysis was designed to (1) examine the impact of heparin-induced thrombocytopenia (HIT) on contemporary cardiac surgical practice and (2) describe the results of a protocol designed for early identification of the presence of the immune mechanisms involved. Consecutive patients who underwent cardiac surgery were screened postoperatively for thrombocytopenia. Patients with thrombocytopenia were tested for antiplatelet factor 4 (PF4)/heparin antibodies by ELISA and clinical evidence of thrombosis sought. Demographics, co-morbidities, operative details, and outcomes were abstracted from the departmental registry. Of 14,415 consecutive patients undergoing cardiac surgery, 1,849 patients (13%) had thrombocytopenia. Of them, 277 patients (15%) had PF4/heparin antibodies and 76 patients (4%) had both antibodies and clinical thrombosis. Antibodies were more frequent: (1) in women (p = 0.01), (2) in patients with an increased body mass index (p <0.01), and (3) in patients with clinical heart failure before surgery (p <0.01). Thirty-day mortality was greatest among the 76 patients with the triad of thrombocytopenia, antibodies, and clinical thrombosis (30%). Of the 1,849 patients with thrombocytopenia, the presence of PF4/heparin antibodies was an independent predictor of 30-day mortality (odds ratio 2.09, 95% CI 1.46 to 2.49; p <0.001). HIT remains an infrequent but very serious complication of heparin therapy in contemporary cardiac surgical practice. The possibility that the presence of HIT antibodies in patients with thrombocytopenia independently increases operative mortality deserves further study.

The Role of Right Ventricular Function in Mitral Valve Surgery

BACKGROUND An impaired right ventricular function is associated with a poor survival rate in patients with heart failure. Few investigations have analyzed the prognostic value of right ventricular function on the outcomes of mitral valve (MV) surgery. The objectives of this study were to define the effect of right ventricular function on postoperative outcomes after MV repair (MVP) or replacement (MVR). METHODS From September 2007 to February 2012, 335 consecutive patients underwent MVP or MVR at our institution. Preoperative transthoracic and transesophageal echocardiography (TEE) and postoperative TEE were used to define right ventricular function and MV performance. Preoperative right ventricular function was graded as normal to mild (grade 1-2) or as moderate to severe (grade 3-4). MV or tricuspid valve regurgitation was graded as non-trivial to mild (grade 0-2) or as moderate to severe (grade 3-4) preoperatively and postoperatively. Survival rate was evaluated at 1 year after surgery. RESULTS Of the 334 patients in the study, 280 patients showed a normal to a mildly impaired right ventricular function preoperatively (group 1). Fifty-four patients presented with moderate to severe right ventricular dysfunction (group 2). Patients with a compromised right ventricular function were more likely to undergo MVR (28.6% versus 53.7%, P <.001). The mean pulmonary artery pressure was 23.6 mm Hg in group 1 and 34 mm Hg in group 2 (P <.001). The left atrial diameter was 4.6 cm in group 1 and 5.3 cm in group 2 (P <.001). The 2 groups were not different with respect to operative mortality, but the patients in group 2 experienced more transfusion of blood products (588.4 mL versus 1180.6 mL, P <.001), longer intensive care unit stays (83.9 versus 149.6 hours, P <.001), and hospital stays (8.9 versus 12.8 days, P = .005). The rate of postoperative MV regurgitation was significantly higher in group 2 (1.8 versus 14.8%, P <.001). The overall 1-year survival rate was 92.5% in group 1 and 94.5% in group 2 (P = .59). CONCLUSIONS This study has shown that a dysfunctional preoperative right ventricular function uses more resources and is associated with postoperative MV regurgitation, but it is not associated short- and mid-term mortality after MV surgery.