Oswaldo Valencia

Monitoring the results of cardiac surgery by variable life-adjusted display

BACKGROUND Conventional assessment of the outcome of cardiac surgery usually takes the form of retrospective mortality figures and, at best, indicates an average performance over time. Summary tables conceal good and bad runs, and without risk adjustment they are difficult to interpret. We developed a refinement of the cumulative sum method that weights death and survival by each patients risk status and provides a display of surgical performance over time. METHODS The variable life-adjusted (VLAD) plot shows the difference between expected and actual cumulative mortality. VLAD shows whether a surgeons performance is above or below what might be expected. This mortality-scoring system accumulates penalties for each death and rewards for every survivor, based on the inherent risk of perioperative death of each case concerned. FINDINGS We illustrate the results of three performance reviews, displayed as VLADs. The first shows the results of an individual surgeon for 547 consecutive cardiac-surgical cases. The overall mortality was 36% less than that predicted by the Parsonnet scoring system. The second displays the results for 5000 consecutive patients who underwent cardiopulmonary bypass between 1992 and 1996, divided into six contemporaneous series. The predicted mortality was 9% compared with 6% actual mortality. The third is a plot for a trainee surgeon and clearly shows how a period of poor performance was identified and then substantially improved, which would not have been revealed by conventional tables of summary statistics. INTERPRETATION VLAD provides a graphical display of risk-adjusted survival figures for individual surgeons or units over time and could be modified to monitor performance over a range of treatments and outcomes.

Resternotomy for bleeding after cardiac operation: A marker for increased morbidity and mortality

Over a 2-year period from January 1, 1992, to December 31, 1993, of 2,221 patients undergoing cardiac operations in our unit, 85 (3.8%) were reopened for the control of bleeding (9 patients more than once). The incidence of resternotomy in coronary cases was 2.3%, but resternotomy was more than three times as likely in valve cases (odds ratio, 3.4; 95% confidence interval, 2.1 to 5.4). Previous cardiac operation was more common among resternotomy patients than among the remainder (18% versus 9%, respectively; p = 0.018). An identifiable source of bleeding was found in 57 of the 85 patients (67%), but a concurrent coagulopathy was common (45 patients). Resternotomy patients, as a group, had higher preoperative risk scores (Parsonnet) than did the other patients (p < 0.0001), stayed longer in the intensive care unit (p < 0.0001), and had greater requirements for intraaortic balloon counterpulsation (14% versus 3%) and hemofiltration (9% versus 3%) (p < 0.0001 and p < 0.01, respectively). Nineteen resternotomy patients (22%) died in the hospital, a proportion significantly greater than the risk assigned to this group of patients preoperatively (12.8%) (p = 0.008). In contrast, the observed mortality for the other 2,136 patients (5.5%) was significantly less (8.3%) (p < 0.00006). Multiple forward stepwise logistic-regression analysis confirmed resternotomy for excessive bleeding after cardiac operation to be a significant independent predictor of a prolonged stay in the intensive care unit (p < 0.0001), the need for intraaortic balloon counterpulsation (p < 0.0001), and death (p < 0.0001).

Dose-Related Effect of Statins on Atrial Fibrillation After Cardiac Surgery

BACKGROUND Atrial fibrillation (AF) is the most common heart rhythm abnormality after cardiac surgery. It increases morbidity and prolongs hospital stay. A role for statins in the prevention of AF has been suggested. We hypothesized that the incidence of postoperative AF due to statin therapy is dose-related. METHODS A retrospective study of 680 consecutive patients undergoing coronary bypass graft surgery and/or aortic valve replacement was done. Excluded were 57 patients (8.4%) with history of AF, permanent pacemakers, and those receiving antiarrhythmic medication. Preoperative statin treatment and occurrence of postoperative AF were examined using propensity score matching to adjust for differences in patient characteristics between the statin and no-statin groups. RESULTS The cohort comprised 623 patients. The statin group had a 27.1% incidence of postoperative AF vs 38.3% in the no-statin group (adjusted odds ratio [OR], 2.00; 95% confidence interval, 1.24 to 3.24; p = 0.004). Simvastatin (40 mg) and atorvastatin (40 mg) demonstrated the greatest effect on postoperative AF at 15.6% and 21.2%, respectively, vs no statins (respective adjusted ORs, 3.89 [p < 0.0001] and 2.76 [p = 0.012]). Intermediate-dose (20 mg) statins were also effective against AF, at 24.4% for simvastatin (adjusted OR, 2.32; p = 0.004) and 26.4% for atorvastatin (adjusted OR, 1.99, p = 0.047). Low-dose statins, simvastatin or atorvastatin (10 mg), did not influence postoperative AF. CONCLUSIONS Statin treatment may reduce the incidence of AF after cardiac surgery. Higher-dose statins have the greatest preventative effect, whereas low-dose statins do not influence postoperative AF.

Analytical methods for calculating the capacity required to operate an effective booked admissions policy for elective inpatient services.

In the UK, hospitals are being encouraged to introduce booked admissions policies for elective inpatient services whereby patients are given a date for hospital admission months in advance rather than being put on a waiting list and then informed of their admission date at short notice. We address the question of what level of capacity is required to operate such a system if cancellations of booked elective patients are to be kept to a low level. Methods are presented for quantifying the day to day variation in bed demand due to emergency admissions, patient initiated cancellations and variable lengths of stay amongst patients.

Low cardiopulmonary bypass perfusion temperatures are associated with acute kidney injury following coronary artery bypass surgery.

OBJECTIVE Acute kidney injury (AKI) is a common complication after coronary artery bypass surgery (CABG). The role of hypothermia in postoperative renal function remains controversial. We set out to examine the effect of varying cardiopulmonary bypass (CPB) temperatures on early postoperative renal function. METHODS Patients undergoing first-time CABG between 2002 and 2006 and without evidence of preoperative renal insufficiency (estimated creatinine clearance >or=50 ml min(-1), calculated by the Cockcroft-Gault formula) were studied. Medical history and intra-operative variables, including lowest nasopharyngeal and arterial CPB perfusion temperatures, were collected prospectively. Primary endpoint was the development of early postoperative AKI (defined as creatinine clearance <50 ml min(-1)), which was assessed using multivariate and propensity score analyses. RESULTS This study included 1072 patients. AKI occurred in 175 (16%). Univariate analysis demonstrated that lower arterial CPB perfusion temperatures, and not nasopharyngeal ones, were significantly associated with renal dysfunction following CABG. Multivariate regression analysis identified reduced arterial perfusion temperature as an independent risk factor for AKI (odds ratio (OR) 0.92, 95% confidence interval (CI): 0.86-0.98, p=0.012), along with age (OR 1.07, 95% CI: 1.04-1.10, p<0.001) and depressed preoperative creatinine clearance (OR 0.89, 95% CI: 0.87-0.91, p<0.001). Propensity score adjustment confirmed that lower CPB perfusion temperatures (<27 degrees C) were associated with postoperative AKI (OR 1.66, 95% CI: 1.16-2.39, p=0.0056). CONCLUSIONS Lower CPB perfusion temperatures are significantly associated with AKI following CABG. In addition to the known age-related decline in renal function, it appears that hypothermia may contribute to renal injury during cardiac surgery.

Protective effect of epicardial adiponectin on atrial fibrillation following cardiac surgery

OBJECTIVE Inflammation has been implicated in the pathogenesis of postoperative atrial fibrillation (AF). Adipose tissue secretes both pro-inflammatory cytokines such as interleukin-6 (IL-6) and anti-inflammatory mediators such as adiponectin. We set out to examine the association of adiponectin and IL-6, both circulating and locally produced by the epicardial adipose tissue, with AF development after cardiac surgery. METHODS A total of 90 consecutive patients undergoing cardiac surgery were evaluated. Blood samples were collected before induction of anaesthesia. Epicardial fat was obtained upon commencement of cardiopulmonary bypass. IL-6 and adiponectin levels were determined in serum and supernatant of epicardial adipose tissue organ cultures with two-site enzyme-linked immunosorbent assay (ELISA). Heart rhythm was assessed with continuous tele-monitoring for 72 h postoperatively, and with 6-hourly clinical examinations and daily electrocardiograms (ECGs) thereafter. RESULTS A total of 36 patients developed postoperative AF (40%). Baseline-serum IL-6 and adiponectin were not associated with AF (p = 0.86 and 0.95, respectively). Epicardial adipose tissue IL-6 levels did not correlate with the development of the arrhythmia either (p = 0.37). However, epicardial adiponectin release was lower in patients who developed AF than in those who remained in sinus rhythm (76 (interquartile range (IQR) 35-98) vs 53 ((IQR) 35-69) ng h(-1)g(-1) of tissue cultured, p = 0.066). Following linear regression, the association of epicardial adiponectin with AF almost reached statistical significance (p = 0.066). Multivariate logistic regression analysis of identified risk factors for AF, with the inclusion of epicardial adiponectin as an independent variable, revealed increased age (odds ratio (OR) 1.09, 95% confidence interval (CI) 1.02-1.17, p = 0.013) and epicardial adiponectin levels (OR 0.98, 95% CI 0.97-1.00, p = 0.054) as independent predictors of postoperative AF. CONCLUSIONS Increased epicardial adiponectin is associated with maintenance of sinus rhythm following cardiac surgery. This reinforces the inflammatory hypothesis in the pathogenesis of postoperative AF and may represent a novel therapeutic target for its effective prevention.

Preoperative high-dose atorvastatin for prevention of atrial fibrillation after cardiac surgery: A randomized controlled trial

OBJECTIVE The preventative effect of statins on postoperative atrial fibrillation has been hypothesized. However, all studies to date have examined patients who did not receive statins before their further allocation to treatment or no treatment. Because guidelines recommend the routine use of statins in patients with coronary artery disease, we set out to examine the effect of intensive statin pretreatment versus continuation of usual statin dose on atrial fibrillation after cardiac surgery. METHODS Patients receiving routine statin treatment and undergoing coronary artery bypass surgery or aortic valve replacement with no history of atrial fibrillation or antiarrhythmic medication were randomized to receive atorvastatin 80 mg or atorvastatin 10 mg for 7 days before surgery in a single-blind fashion. The primary end point was the development of postoperative atrial fibrillation during hospital stay. RESULTS A total of 104 consecutive patients were included. Postoperative atrial fibrillation occurred in 33 patients (32.4%). No significant differences were found in demographics, medical history, or intraoperative variables between treatment groups, with the exception of higher rate of β-blocker use in the atorvastatin 10 mg group (75% vs 53%, P = .002) and previous myocardial infarction (62% vs 42%, P = .049). The incidence of postoperative atrial fibrillation was lower in the atorvastatin 80 mg group when compared with the atorvastatin 10 mg group, but this difference did not reach statistical significance (29% vs 36%, P = .43). CONCLUSIONS High-dose atorvastatin for 7 days before cardiac surgery conferred a nonsignificant reduction in postoperative atrial fibrillation when compared with a low-dose regimen. A larger study would be necessary to confirm the beneficial effect of high-dose statins in this setting.

Surgical Performance Measurement

The need for effective surgical performance measurement has gained an increasingly high profile in recent years, particularly since events at Bristol Royal Infirmary, where apparent poor performance has prompted the UK Department of Health to instigate a major Public Inquiry. This paper describes issues that concern the measuring and monitoring of surgical performance, and methods that have been devised for judging a good surgeon from the less competent. The authors are a collaborative team composed of specialists in Cardiothoracic surgery and Operational Research analysts with experience of monitoring performance in cardiac surgery. This paper describes concrete examples from that knowledge base.

Acute kidney injury after transcatheter aortic valve implantation: incidence, risk factors, and prognostic effects.

ObjectiveAcute kidney injury (AKI) is a common complication after surgical aortic valve replacement and is associated with increased mortality. Transcatheter aortic valve implantation (TAVI) is now considered the criterion standard treatment of patients with severe symptomatic aortic stenosis ineligible for surgery. The aim of this study was to establish the incidence, risk factors, and prognostic consequences of AKI after TAVI and at 1-year follow-up in a single center. MethodsBetween December 2007 and March 2011, a total of 79 patients with severe aortic stenosis who underwent 81 TAVI procedures with the Medtronic CoreValve System or the Edwards SAPIEN heart valve were included. Baseline characteristics and procedural complications were recorded. Acute kidney injury was defined according to the Valve Academic Research Consortium criteria (modified risk, injury, failure, loss, and end-stage kidney disease criteria). ResultsThe mean age was 84 (78–87) years; 49 were men. After TAVI, 10 patients (12.3%) developed AKI, which had completely resolved in 9 patients before hospital discharge. Nine patients (10%) had mild AKI (stage 1) and only one patient (10%) experienced moderate AKI (stage 2) according to Valve Academic Research Consortium definitions. The predictive factors of AKI were diabetes (odds ratio, 6.722; P = 0.004) and preoperative creatinine level greater than 104 &mgr;mol/L (odds ratio, 1.024; P = 0.02). Thirteen patients (16.4%) died within 1 year after TAVI. Three of the nonsurvivors (3.7%) developed AKI postoperatively. Acute kidney injury was, however, not a predictive factor of 1-year mortality after TAVI. ConclusionsAcute kidney injury occurred in 12.3% of the patients after TAVI and persisted in only one patient before hospital discharge. Diabetes and preoperative creatinine level were found to be the main predictive factors of AKI after TAVI. Acute kidney injury was not associated with increased 1-year mortality.

Effect of Valve Suture Technique on Incidence of Paraprosthetic Regurgitation and 10-Year Survival

BACKGROUND The primary objective was to estimate the risk of paraprosthetic regurgitation (PPR) after aortic (AVR) and mitral valve replacement (MVR) using interrupted (IN) or semicontinuous (SC) sutures. The secondary objective was to estimate the risk of redo valve surgery and 10-year survival after valve replacement performed using either suture technique. METHODS Patients who underwent mechanical AVR or MVR using a St. Jude prosthesis between December 1991 and June 1997 were included. Eighteen patients had MVR and 43 had AVR using IN sutures; 49 and 83 patients received MVR and AVR, respectively, using SC sutures. The majority of these patients were part of a randomized controlled trial with different end points, presented elsewhere. Patients were followed for 10 years with annual transthoracic echocardiography, and clinical data were collected retrospectively. Kaplan-Meier survival analysis was performed. Coxs regression analysis was performed to identify factors predicting mortality as a function of time. Forward stepwise logistic regression was performed to analyze risk factors predicting PPR. Mann-Whitney U test was used for continuous and nonparametric data, and chi2 test and Fishers exact test were used for categorical data. A probability value less than 0.05 was considered significant. RESULTS The overall risk of PPR after MVR and AVR was higher in the SC group than in the IN group. The need for redo AVR was significantly higher in the SC group. The suture technique did not affect the 10-year survival after either AVR or MVR. CONCLUSIONS Use of SC technique increases the risk of significant PPR after AVR and MVR compared with IN technique independent of the size of prosthesis, degree of annular calcification, disease of the excised valve, or the implanting surgeon. Although 10-year survival is independent of suture technique, SC technique increases the risk of redo valve replacement after AVR.