Patrick H. Gibson

Relationship between postoperative cardiac troponin I levels and outcome of cardiac surgery.

Background— Cardiac surgery may be associated with significant perioperative and postoperative morbidity and mortality. Underlying pathology, surgical technique, and postoperative complications may all influence outcome. These factors may be reflected as a rise in postoperative troponin levels. Interpretation of troponin levels in this setting may therefore be complex. This study assessed the prognostic significance of such measurements, taking into account potential confounding variables. Methods and Results— One-thousand three hundred sixty-five patients undergoing cardiac surgery underwent measurement of cardiac troponin I (cTnI) at 2 and 24 hours after surgery. The relationship of these measurements to subsequent mortality was established. After taking into account all other variables, cTnI levels measured at 24 hours were independently predictive of mortality at 30 days (odds ratio [OR] 1.14 per 10 &mgr;g/L, 95% confidence interval [CI] 1.05 to 1.24, P=0.002), 1 year (OR 1.10 per 10 &mgr;g/L, 95% CI 1.03 to 1.18, P=0.006), and 3 years (OR 1.07 per 10 &mgr;g/L, 95% CI 1.00 to 1.15, P=0.04). Cardiac TnI levels in the highest quartile at 24 hours were associated with a particularly poor outcome. Conclusions— cTnI levels measured 24 hours after cardiac surgery predict short-, medium-, and long-term mortality and remain independently predictive when adjusted for all other potentially confounding variables, including operation complexity.

Usefulness of Neutrophil/Lymphocyte Ratio As Predictor of New-Onset Atrial Fibrillation After Coronary Artery Bypass Grafting

The neutrophil/lymphocyte (N/L) ratio integrates information on the inflammatory milieu and physiologic stress. It is an emerging marker of prognosis in patients with cardiovascular disease. We investigated the relation between the N/L ratio and postoperative atrial fibrillation (AF) in patients undergoing coronary artery bypass grafting. In a prospective cohort study, 275 patients undergoing nonemergency coronary artery bypass grafting were recruited. Patients with previous atrial arrhythmia or requiring concomitant valve surgery were excluded. The N/L ratio was determined preoperatively and on postoperative day 2. The study end point was AF lasting >30 seconds. Patients who developed AF (n = 107, 39%) had had a greater preoperative N/L ratio (median 3.0 vs 2.4, p = 0.001), but no differences were found in the other white blood cell parameters or C-reactive protein. The postoperative N/L ratio was greater in patients with AF (day 2, median 9.2 vs 7.2, p <0.001), and in multivariate models, a greater postoperative N/L ratio was independently associated with a greater incidence of AF (odds ratio 1.10 per unit increase, p = 0.003: odds ratio for N/L ratio >10.14 [optimal postoperative cutoff in our cohort], 2.83 per unit, p <0.001). Elevated pre- and postoperative N/L ratios were associated with an increased occurrence of AF after coronary artery bypass grafting. In conclusion, these results support an inflammatory etiology in postoperative AF but suggest that other factors are also important.

N-terminal pro-B-type natriuretic peptide levels and early outcome after cardiac surgery: a prospective cohort study

BACKGROUND N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentrations predict cardiovascular outcome in many settings. There are very few data assessing the utility of NT-proBNP concentrations in the prediction of long-term outcome after cardiac surgery. We assessed the ability of NT-proBNP to predict 3 yr mortality compared with validated clinical risk prediction tools. METHODS A secondary analysis of a prospectively recruited patient cohort of 1010 patients undergoing cardiac surgery. Baseline clinical details were obtained including EuroSCORE. Multi-variable modelling, area under the receiver operating characteristic curves (AUCs), and net reclassification improvement were utilized. RESULTS NT-proBNP was a univariable predictor of 3 yr mortality but was no longer a significant predictor in a multivariable model (hazard ratio 1.00 per 250 ng litre(-1), 95% confidence interval 0.98-1.02, P=0.80). The relative and additive predictive values of the preoperative EuroSCORE (both additive and logistic versions) and NT-proBNP concentrations were compared. All were predictive of 3 yr mortality (P<0.001) with almost identical AUCs (0.71 for EuroSCORE, 0.70 for NT-proBNP). When either the EuroSCORE or NT-proBNP concentrations are known, the addition of the other does not improve the ability to predict 3 yr mortality. CONCLUSIONS Preoperative NT-proBNP concentrations and the EuroSCORE have equivalent, and moderate, predictive accuracy for mortality 3 yr after cardiac surgery. EuroSCORE uses clinical data but is not routinely used for individual clinical risk prediction. NT-proBNP measurement would incur additional costs but can be measured quickly and objectively. With such similar predictive accuracy, factors such as the ease of calculation and cost will likely determine their use in clinical practice.

Use of preoperative natriuretic peptides and echocardiographic parameters in predicting new-onset atrial fibrillation after coronary artery bypass grafting: A prospective comparative study

BACKGROUND Atrial fibrillation (AF) is a common complication after coronary artery bypass grafting (CABG). We prospectively compared the ability of echocardiographic parameters and the cardiac neurohormones, brain natriuretic peptide (BNP), and N-terminal pro-brain natriuretic peptide (NT-proBNP) to predict AF in this setting. METHODS We recruited 275 patients undergoing nonemergency CABG. Patients undergoing valve surgery or with prior atrial dysrhythmia (based on clinical history and review of medical records) were excluded. Echocardiography was performed, and natriuretic peptide levels were measured, 24 hours before surgery. The primary end point was postoperative AF lasting >30 seconds. RESULTS The only significant echocardiographic predictors of postoperative AF (n = 107, 39%) were the transmitral E to A-wave ratio and the early mitral annulus velocity. Levels of BNP and NT-proBNP were higher in patients who developed AF. Both natriuretic peptides, but none of the echocardiographic parameters, remained independently predictive in multivariable analysis. The optimum cut points for predicting AF were 31 pg/mL for BNP (odds ratio [OR] 2.74, P = .001) and 74 pg/mL for NT-proBNP (OR 2.74, P = .003). CONCLUSION Levels of BNP and NT-proBNP are independent, though modestly effective, predictors of AF after isolated CABG. In contrast, none of the echocardiographic parameters assessed, including measures of LV systolic function and filling pressure, were independently predictive.

Uric acid levels and outcome from coronary artery bypass grafting.

OBJECTIVE Elevated uric acid levels have been associated with an adverse cardiovascular outcome in several settings. Their utility in patients undergoing surgical revascularization has not, however, been assessed. We hypothesized that serum uric acid levels would predict the outcome of patients undergoing coronary artery bypass grafting. METHODS The study cohort consisted of 1140 consecutive patients undergoing nonemergency coronary artery bypass grafting. Clinical details were obtained prospectively, and serum uric acid was measured a median of 1 day before surgery. The primary end point was all-cause mortality. RESULTS During a median of 4.5 years, 126 patients (11%) died. Mean (+/- standard deviation) uric acid levels were 390 +/- 131 micromol/L in patients who died versus 353 +/- 86 micromol/L among survivors (hazard ratio 1.48 per 100 micromol/L; 95% confidence interval, 1.25-1.74; P < .001). The excess risk associated with an elevated uric acid was particularly evident among patients in the upper quartile (>or=410 micromol/L; hazard ratio vs all other quartiles combined 2.18; 95% confidence interval, 1.53-3.11; P < .001). After adjusting for other potential prognostic variables, including the European System for Cardiac Operative Risk Evaluation, uric acid remained predictive of outcome. CONCLUSION Increasing levels of uric acid are associated with poorer survival after coronary artery bypass grafting. Their prognostic utility is independent of other recognized risk factors, including the European System for Cardiac Operative Risk Evaluation.

Socio-economic status and early outcome from coronary artery bypass grafting

Objective: To determine the effects of socio-economic status (SES) on the outcome of coronary artery bypass grafting (CABG). Design: Prospective cohort study. Setting: Regional cardiac surgical unit. Patients: 1994 consecutive patients undergoing non-emergency CABG. Measures: SES was determined from the patient’s postcode using Carstairs tables. The primary end-point was all-cause mortality at 30 days. Results: There were 50 deaths (2.5%) within 30 days of surgery. A higher Carstairs score demonstrated a trend towards increased 30-day mortality (odds ratio (OR) 1.09 per unit, 95% CI 1.00 to 1.20, p = 0.06). In a backward conditional model, including other predictors of early mortality, Carstairs scores were independently predictive (OR 1.12 per unit, 95% CI 1.01 to 1.24, p = 0.02). In a model including only Carstairs scores and the EuroSCORE, both were independent predictors of this outcome (OR for Carstairs score 1.11 per unit, 95% CI 1.00 to 1.22, p = 0.04). The 30-day mortality increases in each quartile of Carstairs scores, with patients in quartile 4 (most deprived) at significantly higher risk compared with quartile 1 (uncorrected OR 2.53 per unit, 95% CI 1.04 to 6.15; OR corrected for EuroSCORE, 2.56 per unit, 95% CI 1.03 to 6.34, p = 0.04 for both). Similarly, patients in the least affluent quartile were twice as likely to suffer a serious complication as those in the most affluent quartile (OR 2.14 per unit, 95% CI 1.32 to 3.46, p = 0.002). This increased risk was also independent of the EuroSCORE. Conclusions: Lower SES is associated with a poorer early outcome following CABG and is independent of other recognised risk factors.

The relationship between renal function and outcome from heart valve surgery

BACKGROUND The prognostic importance of renal function in patients undergoing surgery for valvular heart disease is poorly defined. The current study addresses this issue. METHODS Baseline demographic and clinical variables, including the European system for cardiac operative risk evaluation (EuroSCORE), were recorded prospectively from 514 consecutive patients undergoing heart valve surgery between April 2000 and March 2004. Patients with active infective endocarditis and/or requiring emergency surgery were excluded. The glomerular filtration rate was estimated (eGFR) using the Modification of Diet in Renal Disease equation. The primary outcome was all-cause mortality. RESULTS During a median follow-up of 2 years, 87 patients died. In univariable analysis, both eGFR (hazard ratio [HR] 0.69 per 10 mL/min per 1.73 m2, P<.001) and creatinine (HR 1.04 per 10 micromol/L, P<.001) predicted mortality. Estimated GFR was a stronger predictor and was used in subsequent multivariable models. It remained a powerful independent predictor of death in a multivariable model including all study variables (HR 0.70 per 10 mL/min per 1.73 m2 increase, P<.001) and in a model including EuroSCORE (HR 0.64 per 10 mL/min per 1.73 m2 increase, P<.001). After correction for preoperative EuroSCORE, an eGFR of <60 mL/min per 1.73 m2 was associated with an excess hazard of death of 2.31 (P=.001). CONCLUSION Renal function, particularly the eGFR, is a powerful predictor of outcome in patients undergoing heart valve surgery. This prognostic utility is independent of other recognized risk factors and the EuroSCORE.

Adverse Psychological Effects and Costs Associated with Waiting for Radiofrequency Ablation

Radiofrequency ablation (RFA) is undertaken as a potentially curative treatment for a variety of heart rhythm disturbances. Previous studies have demonstrated improved quality of life and reduced symptoms after ablation. In many health care environments waiting lists exist for scheduling of procedures. However, the psychological effects of waiting for radiofrequency ablation have not previously been assessed. We hypothesized that waiting for this intervention may be associated with increased psychological morbidity and health care costs.