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.

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.

Renal function and outcome from coronary artery bypass grafting: impact on mortality after a 2.3-year follow-up.

BACKGROUND: Severe renal dysfunction is associated with a worse outcome after coronary artery bypass graft surgery (CABG). Less is known about the effects of milder degrees of renal impairment, and previous studies have relied on levels of serum creatinine, an insensitive indicator of renal function. Recent studies have suggested that estimated glomerular filtration rate (eGFR) is a more discriminatory measure. However, data on the utility of eGFR in predicting outcome from CABG are limited. METHODS AND RESULTS: We studied 2067 consecutive patients undergoing CABG. Demographic and clinical data were collected preoperatively, and patients were followed up a median of 2.3 years after surgery. Estimated GFR was calculated from the Modification of Diet in Renal Disease equation. The primary outcome was all-cause mortality. Mean+/-SD eGFR was 57.9+/-17.6 mL/min per 1.73 m2 in the 158 patients who died during follow-up compared with 64.7+/-13.8 mL/min per 1.73 m2 in survivors (hazard ratio [HR], 0.71 per 10 mL/min per 1.73 m2; 95% CI, 0.64 to 0.80; P<0.001). Estimated GFR was an independent predictor of mortality in both models with other individual univariable predictors (HR, 0.80 per 10 mL/min per 1.73 m2; 95% CI, 0.72 to 0.89; P<0.001) and the European system for cardiac operative risk evaluation (HR, 0.88 per 10 mL/min per 1.73 m2; 95% CI, 0.78 to 0.98; P=0.02). CONCLUSIONS: Estimated GFR is a powerful and independent predictor of mortality after CABG.

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 microg/L, 95% confidence interval [CI] 1.05 to 1.24, P=0.002), 1 year (OR 1.10 per 10 microg/L, 95% CI 1.03 to 1.18, P=0.006), and 3 years (OR 1.07 per 10 microg/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.

Preoperative neutrophil-lymphocyte ratio and outcome from coronary artery bypass grafting.

BACKGROUND: An elevated preoperative white blood cell count has been associated with a worse outcome after coronary artery bypass grafting (CABG). Leukocyte subtypes, and particularly the neutrophil-lymphocyte (N/L) ratio, may however, convey superior prognostic information. We hypothesized that the N/L ratio would predict the outcome of patients undergoing surgical revascularization. METHODS: Baseline clinical details were obtained prospectively in 1938 patients undergoing CABG. The differential leukocyte was measured before surgery, and patients were followed-up 3.6 years later. The primary end point was all-cause mortality. RESULTS: The preoperative N/L ratio was a powerful univariable predictor of mortality (hazard ratio [HR] 1.13 per unit, P < .001). In a backward conditional model, including all study variables, it remained a strong predictor (HR 1.09 per unit, P = .004). In a further model, including the European system for cardiac operative risk evaluation, the N/L ratio remained an independent predictor (HR 1.08 per unit, P = .008). Likewise, it was an independent predictor of cardiovascular mortality and predicted death in the subgroup of patients with a normal white blood cell count. This excess hazard was concentrated in patients with an N/L ratio in the upper quartile (>3.36). CONCLUSION: An elevated N/L ratio is associated with a poorer survival after CABG. This prognostic utility is independent of other recognized risk factors.

Is there evidence that fresh frozen plasma is superior to antithrombin administration to treat heparin resistance in cardiac surgery?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was, 'in [patients with heparin resistance] is [treatment with FFP] superior [to antithrombin administration] in [achieving adequate anticoagulation to facilitate safe cardiopulmonary bypass]?' More than 29 papers were found using the reported search, of which six represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. Antithrombin (AT) binds to heparin and increases the rate at which it binds to thrombin. The levels of antithrombin in the blood are an important aspect of the heparin dose-response curve. When the activated clotting time (ACT) fails to reach a target >480, this is commonly defined as heparin resistance (HR). Heparin resistance is usually treated with a combination of supplementary heparin, fresh frozen plasma (FFP) or antithrombin III concentrate. There is a paucity of evidence on the treatment of heparin resistance with FFP, with only five studies identified, including one retrospective study, one in vitro trial and three case reports. AT has been studied more extensively with multiple studies, including a crossover trial comparing AT to supplemental heparin and a multicentre, randomized, double blind, placebo-controlled trial. Antithrombin (AT) concentrate is a safe and efficient treatment for heparin resistance to elevate the activated clotting time (ACT). It avoids the risk of transfusion-related acute lung injury (TRALI), volume overload, intraoperative time delay and viral or vCJD transmission. Antithrombin concentrates are more expensive than fresh frozen plasma and may put patients at risk of heparin rebound in the early postoperative period. Patients treated with AT have a lower risk of further FFP transfusions during their stay in hospital. We conclude that the treatment of HR with FFP may not restore the ACT to therapeutic levels with adequate heparinization, but AT is efficient with benefits including lower volume administration, less risk of TRALI and lower risk of transfusion-related infections.

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.

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.

Preliminary evaluation of the Sternum Screw: a novel method for improved sternal closure to prevent dehiscence.

Sternal dehiscence is a relatively rare but serious complication of sternal closure with an unacceptable mortality and morbidity rate. The 6 mm cannulated Sternum Screws are a novel approach that aims to prevent dehiscence. The screws are placed on either side of the sternotomy and wire threaded through the cannula and closed customarily. The Sternum Screws make the bone non-penetrable at the same time retaining the familiarity of conventional stainless steel wire. This novel technique was tested in sheep sterna to compare its efficacy to conventional wire closure. Using tensile testing in a testing machine, randomised controlled closures of the Sternum Screws and No. 5 stainless steel wires were evaluated until system failure. Seventeen matched pairs were tested. The Sternum Screw closure was on average 36% stronger, 284+/-43 N (mean+/-SD) compared to conventional wire closure alone, 215+/-38 N (mean+/-SD) [p<0.0001 by t-test]. System failure in 82% of Sternum Screw closures, however, was due to wire breakage or untwisting rather than the screw itself. In all these cases the screw remained intact in bone. 71% of conventional wire closures failed by dehiscing through the sterna. The mean forces required for wire dehiscence and wire failure in the Sternum Screws may be achieved in vivo during large coughs. The study shows there is merit in further evaluating the approach as a method of preventing dehiscence. It also highlights the use of alternative wiring techniques increase the tensile strength of the closure yet retain the familiarity and versatility of conventional wire.

Sternum screw: analysis of a novel approach to the closure of the chest after surgery.

BACKGROUND: To show the benefits of using a novel approach to closure of the median sternotomy through a mechanical model and mechanical testing. Simple cannulated screws are placed on either side of the sternotomy. Conventional stainless steel wire is passed through the cannula of each screw and the sternotomy is closed in the usual manner. METHODS: Hertzian contact analysis was used to estimate the stress between the wire and the sternum. Mechanical testing was used to compare using wire on its own with a sternum screw plus wire. Ten samples of balsa wood (sternum substitute) had wire placed through a hole in them, while a further ten samples were fitted with a cannulated screw and had wire passed through the screw cannula. The wire was connected to a materials testing machine, which applied tension to the wire until the wire or screw cut through the wood. RESULTS: The analysis showed that the mean stress between the wire and the sternum decreases with increasing wire diameter. At low diameters of wire the stress in the sternum can be comparable to the failure stress of bone. Using a cannulated screw reduces the stresses in the sternum. The mechanical testing showed that the wire cut through the wood at a mean load of 104 N, whereas the sternum screw cut through the wood at a mean load of 209 N (p = 0.007, Mann-Whitney Test). CONCLUSIONS: Closing a median sternotomy with cannulated screws plus wire should reduce the occurrence of sternal dehiscence.