Year : 2014  |  Volume : 17  |  Issue : 3  |  Page : 182--187

Prediction of postoperative atrial fibrillation after coronary artery bypass grafting surgery: Is CHA 2 DS 2 -VASc score useful?


Deepak Borde1, Uday Gandhe1, Neha Hargave1, Kaushal Pandey2, Manish Mathew2, Shreedhar Joshi3,  
1 Department of Cardiac Anaesthesia, P. D. Hinduja National Hospital, Lilavati Hospital, Fortis Hospital, Mumbai, India
2 Department of Cardiac Surgery, P. D. Hinduja National Hospital, Lilavati Hospital, Fortis Hospital, Mumbai, India
3 Department of Cardiac Anaesthesia, Sri Jayadeva Institute of Cardiovascular Sciences and Research Institute, Bengaluru, Karnataka, India

Correspondence Address:
Deepak Borde
Department of Cardiac Anesthesia, P. D. Hinduja National Hospital, Veert Sawarkar Marg, Mahim, Mumbai - 400 022, Maharashtra
India

Abstract

Aims and Objectives: Postoperative atrial fibrillation (POAF) is the most common arrhythmia after coronary artery bypass grafting (CABG) surgery. The identification of patients at risk for POAF would be helpful to guide prophylactic therapy. Presently, there is no simple preoperative scoring system available to predict patients at higher risk of POAF. In a retrospective observational study, we evaluated the usefulness of CHA 2 DS 2 -VASc score to predict POAF after CABG. Materials and Methods: After obtaining approval from Institutional Review Board, 729 patients undergoing CABG on cardiopulmonary bypass (CPB) were enrolled. Patients were followed in the postoperative period for POAF. A multiple regression analysis was run to predict POAF from various variables. The area under the receiver operating characteristic (ROC) curve was calculated to test discriminatory power of CHA 2 DS 2 -VASc score to predict POAF. Results: POAF occurred in 95 (13%) patients. The patients with POAF had higher CHA 2 DS 2 -VASc scores than those without POAF (4.09 ± 0.90 vs. 2.31 ± 1.21; P < 0.001). The POAF rates after cardiac surgery increased with increasing CHA 2 DS 2 -VASc scores. The odds ratio for predicting POAF was highest with higher CHA 2 DS 2 -VASc scores (3.68). When ROC curve was calculated for the CHA 2 DS 2 -VASc scores, area of 0.87 was obtained, which was statistically significant (P < 0.0001). Conclusions: The CHA 2 DS 2 -VASc score was found useful in predicting POAF after CABG. This scoring system is simple and convenient to use in the preoperative period to alert the clinician about higher probability of POAF after CABG surgery.



How to cite this article:
Borde D, Gandhe U, Hargave N, Pandey K, Mathew M, Joshi S. Prediction of postoperative atrial fibrillation after coronary artery bypass grafting surgery: Is CHA 2 DS 2 -VASc score useful?.Ann Card Anaesth 2014;17:182-187


How to cite this URL:
Borde D, Gandhe U, Hargave N, Pandey K, Mathew M, Joshi S. Prediction of postoperative atrial fibrillation after coronary artery bypass grafting surgery: Is CHA 2 DS 2 -VASc score useful?. Ann Card Anaesth [serial online] 2014 [cited 2020 Jul 3 ];17:182-187
Available from: http://www.annals.in/text.asp?2014/17/3/182/135841


Full Text

 INTRODUCTION



Postoperative atrial fibrillation (POAF) is the most common arrhythmia after coronary artery bypass grafting (CABG) surgery. [1],[2] Patients with POAF tend to have longer hospital stay, increased perioperative morbidity and greater early and long-term mortality. [2],[3],[4],[5] Although prophylaxis with antiarrhythmic drugs can decrease the incidence of POAF; however, such an approach in all patients is not cost-effective and may even have adverse effects. [2] At present, there is no simple preoperative scoring system available to predict patients at higher risk of POAF. The identification of patients at risk for POAF would be helpful. CHA 2 DS 2 -VASc score is recommended to guide antithrombotic therapy in patients with AF or atrial futter. [6],[7] All the components of this score are known to be associated with increased incidence of POAF. There is recent interest in this scoring system to predict POAF. [8],[9] Therefore, we tested the hypothesis that CHA 2 DS 2 -VASc score is useful to predict POAF after CABG surgery.

 MATERIALS AND METHODS



This is a retrospective observational study of patients who had undergone CABG on CPB with or without valve replacement or repair surgery, operated by a single surgical team from January 2012 to June 2013. The Institutional Review Board approved the study with waiver of consent. A total of 789 patients underwent surgery during this period and were considered eligible for inclusion in the study. Fifty-one patients were excluded because of various reasons such as incomplete or nonavailability of medical records, preoperative history of AF, and preoperative use of pacemaker and antiarrhythmic drugs. Another nine patients were excluded because antiarrhythmic medications were administered for ventricular arrhythmias in early postoperative period. The final analysis included 729 patients. Demographic and procedural data abstracted from medical records included medical history, clinical examination, investigations and use of preoperative medication (β-blockers, angiotensin converting enzyme inhibitor [ACEI]/angiotensin receptor blockers [ARB], and statins), details of cardiopulmonary bypass [CPB], aortic cross clamp time, number of grafts, use of inotropes and blood transfusion in perioperative period.The CHA 2 DS 2 -VASc scores were calculated for each patient [6] [Table 1]. In addition, data on the principal outcome, new onset POAF defined as new electrocardiography evidence of AF requiring treatment was determined, including its timing and treatment.{Table 1}

General anesthesia was induced with midazolam, fentanyl and etomidate. Rocuronium was used as a muscle relaxant. After induction, intravenous methyl prednisone 500 mg bolus was given to all patients. Anesthesia was maintained by titrated doses of sevoflurane, infusion of fentanyl and midazolam. All patients were operated through median sternotomy. CPB was established with aortocaval cannulation after adequate heparinization (activated clotting time > 400 s). Normothermia (35-37°C) was maintained throughout the surgery. Extracorporeal circuit consisted of membrane oxygenator, roller pump, tubings and crystalloid prime solution. Warm blood cardioplegia was used to achieve cardiac arrest and to provide myocardial protection during aortic clamp. After completion of the distal anastomoses the aortic clamp was released, and proximal anastomoses were completed with a partial side-clamp on the aorta. The preoperative medications like β-blockers, ACEI/ARBs, statins were re-started in the early postoperative period unless medically contraindicated.

Statistical analysis

Continuous variables are described as means with standard deviations and are compared between groups by using Student's t-test (parametric data) or Mann-Whitney U-test (nonparametric data). Dichotomous variables were presented as percentages and compared between groups by Chi-square test or Fisher exact test. For primary analysis all demographic, surgical, and medication utilization variables with a P 0≤ 0.2 in univariate analysis were entered into a stepwise forward multivariate logistic regression model with POAF as the binary dependent outcome. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for all independent variables retained in the multivariate logistic regression model with P ≤ 0.05 was considered as significant. The area under the receiver operating characteristic (ROC) curve was calculated to test discriminatory power of CHA 2 DS 2 -VASc score to predict POAF.

 RESULTS



Baseline clinical characteristics of patients with and without POAF are summarized in [Table 2]. Of the 729 study patients, 95 (13%) had POAF after CABG. The patients with POAF were older and had a significantly higher prevalence of hypertension, diabetes mellitus (P < 0.0001) and vascular disease (peripheral and carotid artery disease; P = 0.0005) compared to patients without POAF. The patients with POAF had significantly higher rates of blood or blood product transfusion and inotrope use in the perioperative period (P < 0.0001). The first choice of inotrope was adrenaline (58% of total 230 patients in which inotropes were used) followed by dopamine/noradrenaline. Combined inotrope therapy was used in 20% of patients. The patients with POAF had higher CHA 2 DS 2 -VASc scores than those without POAF (4.09 ± 0.90 vs. 2.31 ± 1.21; P < 0.0001).{Table 2}

A multiple regression was run to predict POAF from various variables. CHA 2 DS 2 -VASc score, ejection fraction, peripheral vascular disease (PVD), statin use, left main coronary artery disease and inotrope use predicted POAF (P < 0.0005, R 2 =0.281). However only, CHA 2 DS 2 -VASc score and use of inotrope added to the prediction, which was statistically significant (P < 0.05). The OR for predicting POAF was highest with a higher CHA 2 DS 2 -VASc scores (3.68), and inotrope use (3.83). Preoperative statin usage with OR of 0.45 appeared to be protective against POAF [Table 3].{Table 3}

The POAF rates after cardiac surgery increased with increasing CHA 2 DS 2 -VASc scores [Figure 1]. Atrial fibrillation occurred most frequently on the postoperative day (POD) 2 (53%) followed by POD 3 (21%) and POD 1 (13.6%) [Figure 2]. The initial episode was treated pharmacologically; amiodarone was the most common medication administered in about 90% cases during the initial episode of AF. Oral β-blockers were started in the postoperative period as soon as hemodynamic conditions permitted. None of the patients were anticoagulated and overdrive atrial pacing was not used in any patient. No therapy was rendered in 3% patients. ROC curve for the CHA 2 DS 2 -VASc scores showed an area of 0.87, which was statistically significant (P < 0.0001) [Figure 3]. The cut-off for CHA 2 DS 2 VASc score was 3; which showed a sensitivity of 84.21 and specificity of 84.54 with positive predictive value 43.96% (95% CI: 36.3-52.5) and negative predictive value of 97.23 % (95%CI: 95.5-98.4).{Figure 1}{Figure 2}{Figure 3}

 DISCUSSION



The main finding of the present study was that CHA 2 DS 2 -VASc score is useful in predicting POAF after CABG. This scoring system is simple and convenient to use in the preoperative period to alert the clinician about higher probability of POAF after CABG surgery.

Numerous causative factors such as an increase in circulating catecholamine, heightened sympathetic and parasympathetic tone, atrial stretch, transcellular fluid and electrolyte shifts, metabolic abnormalities, inflammation, and pericarditis have been described without any single factor being singled out as cause of this complication. [2],[10] Owing to the complex etiology, it is difficult to predict this complication in the postoperative period. [11] In prospective observational study carried out in 70 centers located within 17 countries with 4657 patients, Mathew et al. [12] developed a multicenter study of perioperative ischemia atrial fibrillation risk index with variables including age, history of AF, chronic obstructive pulmonary disease, concurrent valve surgery, and withdrawal of postoperative β blockers or ACEI/ARBs. These factors were included in a model that assigned points from −25 to +60. A nomogram correlated point score with the probability of developing postoperative AF. In this study, the postoperative variables included were: Withdrawal of β blockers/ACE inhibitors in the postoperative period, postoperative potassium supplementation, and postoperative nonsteroidal antiinflammatory drug use. The inclusion of these postoperative variables limits the applicability of this scoring system in the preoperative period.

Amar et al. [13] studied 1553 patients who underwent isolated on-pump CABG to create a simple risk model for the prediction of POAF. Multivariate analysis showed that greater age (odds ratio [OR] 1.1 per year increment [95% confidence intervals (CI) 1.0 to 1.1], P < 0.0001; estimated coefficient 0.054, point score 1 per one-year increment), history of AF (OR 3.7 [95% CI 2.3 to 6.0], P < 0.0001; estimated coefficient 0.654, point score 12), P-wave duration _110 ms (OR 1.3 [95% CI 1.1 to 1.7], P < 0.02; estimated coefficient 0.142, point score 3), and postoperative low cardiac output (OR 3.0 [95% CI 1.7 to 5.2], P < 0.0001; estimated coefficient 0.547, point score 10) were independently associated with AF risk. A nomogram then correlated point score with AF probability with three risk categories for AF. The area under the ROC curve for the model was 0.69. The inclusion of postoperative low cardiac output and calculation of P-wave duration in this algorithm limit its value as a practical preoperative assessment tool for POAF. In contrast, CHA 2 DS 2 -VASc score can be applied in the preoperative period. Chami et al., [14] constructed a post cardiac surgery AF risk prediction tool using only preoperative variables in a large cohort of more than 18,000 patients and further validated this tool in a sequential cohort of nearly 1400 patients. Their model included different cut-off age, height, weight, and presence of peripheral vascular disease based on gender. Patients were scored on a scale of 0-4 based on these factors. The rate of AF ranged from 10% in the lowest score group (score of zero) to 38.9% in their highest score group (score of four). However, the study is limited to a single center and applicability of this score in a global context may be questionable as demographics of patients differ significantly among regions.

CHA 2 DS 2 -VASc score is recommended to guide antithrombotic therapy in patients with AF or atrial futter. [6],[7] Each component of the CHADS 2 and CHA 2 DS 2 -VASc scores has been associated with the ventricular remodeling, left ventricle diastolic dysfunction, and left atrial enlargement that may lead to atrial arrhythmia. Two recent reports used this score to predict the risk of POAF. Chua et al. [8] in a risk stratification study of 277 patients found that the CHADS 2 and CHA 2 DS 2 -VASc scores were significant predictors of POAF in separate multivariate regression analyses. The Kaplan-Meier analysis indicated a higher POAF rate when based on the CHADS 2 and CHA 2 DS 2 -VASc scores of at least two than when based on scores < two (both log rank, P < 0.001). Similarly, in our study when ROC curve was obtained for the CHA 2 DS 2 -VASc scores, area of 0.87 was obtained, which was statistically significant (P < 0.0001). However in our study, the cut-off for CHA 2 DS 2 -VASc score was three; which showed a sensitivity of 84.21 and specificity of 84.54 with positive predictive value of 43.96% (95% CI: 36.3-52.5) and negative predictive value of 97.23% (95% CI: 95.5-98.4).

In a nested case-control study, Baker et al. [9] , studied a total of 560 patients undergoing CABG and/or valvular surgery from the AF suppression trials I, II, and III. The authors reported POAF in 177 patients (31.6%), with 27%, 23%, and 41% in the low (0-1)-, medium (1-3)-, and high (> 3)-CHA 2 DS 2 -VASc score groups, respectively. The high-score group had 2.3-fold increased odds of developing AF versus the medium-score group (P < 0.0001). Our study also identified CHA 2 DS 2 -VASc score as a significant predictor of POAF with OR of 3.68 on multivariate regression analysis. In contrast to our study, in both the above-mentioned studies, the sample size was small and heterogeneous and included patients with off pump CABG and isolated valvular surgical patients.

Of the 729 patients in the present study, 95 (13%) had POAF after on pump CABG. This incidence is lower as compared with previously reported incidence of 30-40%. [1],[2] There can be various reasons for this difference. First, there are no previous reports on POAF in Indian patients for reference. Second, the incidence of POAF appears to be lower in Asian patients according to a large multicenter study. [12] Third, almost 85% patients were on statin therapy preoperatively. Preoperative statin usage with OR of 0.45 appeared to be protective against POAF in our study and similar to finding of several other investigators. [15],[16] Fourth, only 27.6% patients in the present study were transfused with blood or blood products. Red cell transfusion is known to be associated with an increased risk for POAF. [17] Finally, we used a bolus dose of methyl prednisone after induction of anesthesia in all cases. Although, we have not analyzed the role of steroid supplementation, there are reports which suggest protective effect of steroids against POAF. [16],[18],[19] The other factors which were strongly associated with POAF are inotrope use and PVD. PVD independently predicts mortality after CABG. [20] PVD is also associated with an increased risk for periprocedural complications and with multiple comorbidities, including hypertension and diabetes. These risk factors contribute to the risk for developing AF.

 LIMITATIONS



This study has some notable limitations, including those inherent to any retrospective study design. To minimize confounding, multivariate logistic regression was conducted to control for most known predictors of POAF. Therefore, other predictors that may have been associated with POAF could have been excluded. In addition, detailed data on diastolic function, one of the important determinants of POAF, was unavailable. Our study did not enroll patients undergoing off pump CABG, hence application of this scoring system in that subset is limited.

 CONCLUSIONS



The main finding of this study was that the CHA 2 DS 2 -VASc score is useful in predicting POAF after CABG. This scoring system is simple and convenient to use in the preoperative period to alert the clinician about the probability of POAF after CABG surgery.

 ACKNOWLEDGMENT



The authors would like to acknowledge Dr. Madhav Swaminathan, MD (Duke University, Durham, USA) and Dr. Vijay Shetty, MD (Fortis Hospital, Mumbai) for their guidance in preparing this manuscript.

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