Despite its association with cardioembolic stroke, atrial fibrillation (AF) appears to be inconsistent as a risk factor for postoperative strokes in patients who underwent cardiac surgery. Furthermore, the relation between AF and the CHA 2 DS 2 VASc score has not been definitively established with respect to postoperative stroke. We retrospectively analyzed the records of all cardiac surgery performed at our institution between January 2008 and July 2013. Baseline characteristics, operative data, and postoperative outcomes were compared in patients who developed stroke with those who did not. Previously recognized stroke risk factors, including AF, were analyzed along with the CHADS 2 and CHA 2 DS 2 VASc scores. A total of 3,492 consecutive patients were identified, of which 2,077 (60%) underwent valve surgery, 915 (26%) had coronary artery bypass grafting, 399 (11%) underwent combined coronary artery bypass grafting and valve procedures, and 101 (3%) had other cardiac operations. Postoperative ischemic strokes occurred in 44 patients (1.2%). The development of a stroke was associated with older age (74 ± 12 vs 69 ± 12, p = 0.008), preoperative antiplatelet medication use (38.6% vs 24.5%, p = 0.043), congestive heart failure (37% vs 20%, p = 0.002), and greater CHADS 2 (2.48 ± 1.3 vs 1.98 ± 1.1, p = 0.015) and CHA 2 DS 2 VASc scores (4.2 ± 1.8 vs 3.4 ± 1.6, p = 0.002). Multivariable analysis demonstrated that the CHA 2 DS 2 VASc score was the only independent predictor of postoperative strokes (odds ratio 1.25; 95% confidence interval 1.05 to 1.5, p = 0.014). In conclusion, the CHA 2 DS 2 VASc score appears to predict postoperative strokes independent of the presence of AF.
The CHADS 2 and CHA 2 DS 2 VASc scores have been validated as clinical tools to stratify the risk of stroke in patients with nonvalvular atrial fibrillation (AF). Additionally, these scores appear to predict postoperative strokes in patients who underwent coronary artery bypass grafting (CABG). This evidence is limited and has not addressed the relation between the CHA 2 DS 2 VASc score and preoperative AF, with respect to postoperative strokes. Furthermore, data are limited in its application in valvular and other cardiac operations and different surgical approaches. The purpose of the present study was to evaluate the ability of the CHADS 2 and CHA 2 DS 2 VASc scores in predicting postoperative strokes in patients who underwent various cardiac surgeries.
Methods
After obtaining approval from the institutional review board, we analyzed the data of all cardiac surgery performed at our institution from January 2008 to July 2013. The baseline characteristics, operative data, and postoperative outcomes were compared among patients who developed a stroke with those who did not. The definitions and variables from the Society of Thoracic Surgeons Adult Cardiac Surgery database were used. Postoperative AF was defined as new-onset AF lasting more than 5 minutes, as documented by continuous telemetry, or 12-lead electrocardiogram, necessitating treatment. Stroke was defined as any confirmed neurologic deficit of abrupt onset that did not resolve within 24 hours, with new structural changes detected on computed tomography or magnetic resonance imaging. The strokes were considered postoperative, if they occurred in the period between the beginning of the operation and the patient’s death or discharge from the hospital. The CHADS 2 and CHA 2 DS 2 VASc scores were calculated using the preoperative variables of congestive heart failure, hypertension, age, diabetes mellitus, previous stroke, vascular disease (including peripheral artery disease, myocardial infarction, and aortic plaque), and gender category.
Continuous variables with a parametric distribution are reported as a mean ± standard deviation, whereas those with a nonparametric distribution are reported as a median and interquartile range (IQR or 25% to 75%). To compare continuous variables with a parametric distribution between groups, an independent samples t test was used. Continuous variables not following a parametric distribution were compared using the Mann–Whitney U test. Categorical variables are reported as frequencies and percentages. For comparing these variables, a Fisher’s exact test or Pearson chi-square test was used. Binary logistic regression analyses were performed to identify variables related to stroke. After univariable analysis, variables with p values ≤0.2, including preoperative antiplatelet medication use and the CHA 2 DS 2 VASc score, and those previously associated with stroke, such as AF (both preoperative and postoperative), were analyzed using a multivariable logistic regression model. Variables that were already a component of the CHA 2 DS 2 VASc score, including congestive heart failure and the CHADS 2 score, were excluded from the analysis. A p value <0.05 was considered statistically significant. All statistical analyses were performed using Statistical Program for the Social Sciences software, version 17 (SPSS Inc, Chicago, Illinois).
Results
A total of 3,492 consecutive patients were identified. Of these, 2,077 (60%) underwent valve surgery, 915 (26%) had CABG, 399 (11%) underwent combined CABG and valve procedures, and 101 (3%) had other types of cardiac operations. The other types of cardiac operations included septal defect closures, ascending aortic arch surgery, and intracardiac mass resections. A minimally invasive approach was used in 1,942 (56%) of the surgeries.
Of the 50 strokes that occurred postoperatively, 44 (1.2%) were confirmed to be ischemic strokes by imaging. The median number of days from operation to stroke was 7 days (IQR 2 to 9). The development of a stroke was associated with older age, preoperative antiplatelet use, history of congestive heart failure, and greater CHADS 2 and CHA 2 DS 2 VASc scores ( Table 1 ).
| Variable | Stroke | p-value | |
|---|---|---|---|
| No (3448) | Yes (44) | ||
| Age (Years) | 69 ± 12 | 74 ± 12 | 0.008 |
| Women | 1328 (38.5%) | 19 (43.2%) | 0.6 |
| Body mass index (kg/m 2 ) | 28.2 ± 5.3 | 27.5 ± 7.5 | 0.4 |
| Diabetes mellitus | 1111 (32.2%) | 15 (34.1%) | 0.9 |
| Hypertension ∗ | 3119 (90.5%) | 41 (93.2%) | 0.7 |
| Dyslipidemia † | 2576 (74.7%) | 32 (72.7%) | 0.9 |
| Heart failure | 684 (19.8%) | 17 (38.6%) | 0.002 |
| History of atrial fibrillation | 746 (21.6%) | 13 (29.5%) | 0.3 |
| Left ventricular ejection fraction (%) | 53 ± 12 | 54 ± 11 | 0.6 |
| Chronic obstructive pulmonary disease | 717 (20.8%) | 11 (25%) | 0.6 |
| Prior Peripheral vascular disease | 411 (11.9%) | 5 (11.4%) | ‡ |
| Prior Stroke | 304 (8.8%) | 6 (13.6%) | 0.4 |
| Prior Myocardial infarction | 1012 (29.4%) | 18 (40.9%) | 0.1 |
| Prior Percutaneous coronary intervention | 769 (22.3%) | 10 (22.7%) | 1 |
| Prior Renal replacement therapy | 69 (2%) | 1 (2.3%) | ‡ |
| Pre-operative creatinine | 1.13 ± 0.8 | 1.17 ± 0.17 | 0.8 |
| Previous coronary artery bypass grafting | 252 (7.3%) | 4 (9.1%) | ‡ |
| Previous cardiac valve surgery | 223 (6.5%) | 4 (9.1%) | ‡ |
| Prior Infective endocarditis | 117 (3.4%) | 2 (4.5%) | ‡ |
| Pre-operative beta-blocker use | 2371 (68.8%) | 30 (68.2%) | 1 |
| Pre-operative anti-platelet use | 838 (24.5%) | 17 (38.6%) | 0.04 |
| Pre-operative anticoagulation use § | 433 (12.8%) | 8 (18.2%) | 0.4 |
| Pre-operative angiotensin converting enzyme inhibitor use | 1144 (32.2%) | 19 (43.2%) | 0.2 |
| CHADS 2 | 1.98 ± 1.1 | 2.48 ± 1.3 | 0.02 |
| CHA 2 DS 2 VASc | 3.4 ± 1.6 | 4.2 ± 1.8 | 0.002 |
∗ These patients have a documented history of hypertension diagnosed and treated with medication, diet, and/or exercise, or prior documentation of blood pressure >140 mm Hg systolic or 90 mm Hg diastolic for patients without diabetes or chronic kidney disease (blood pressure >130 mm Hg systolic or 80 mm Hg diastolic on at least 2 occasions for patients with diabetes or chronic kidney disease).
† These patients are on treatment for Dyslipidemia or meet any of the National Cholesterol Education Program criteria for Dyslipidemia: Total Cholesterol > 200 mg/dl (5.18 mmol/l), Low Density Lipoprotein (LDL) ≥ 130 mg/dl (3.37 mmol/l), High Density Lipoprotein < 40 mg/dl (1.02 mmol/l) in men and less than 50 mg/dl (1.20 mmol/l) in women.
‡ Sample size too small for adequate statistical comparison.
§ These patients received either heparin or low molecular weight heparin within 48 hours of the surgery.
Of the 44 ischemic strokes, 23 (1.18%) occurred in cases using a minimally invasive approach, whereas 21 (1.35%) occurred in operations using a standard median sternotomy. The stroke rate was 0.99% for those who underwent isolated CABG, 1.35% for those who underwent isolated valve surgery, and 1.5% for those having combined CABG and/or valve procedures. The aortic cross-clamp and cardiopulmonary bypass times were not significantly different in patients who suffered a postoperative stroke when compared with those who did not ( Table 2 ). Similarly, there were no considerable associations between strokes and any of the various cannulation sites ( Table 2 ).
| Variable | Stroke | p-value | |
|---|---|---|---|
| No (3448) | Yes (44) | ||
| Minimally invasive | 1,919 (55.7%) | 23 (52.3%) | 0.8 |
| Isolated coronary artery bypass surgery | 906 (26.3%) | 9 (20.5%) | 0.5 |
| Isolated valve surgery | 2,049 (59.4%) | 28 (63.6%) | 0.7 |
| Other cardiac procedures ∗ | 100 (2.9%) | 1 (2.3%) | 1 |
| Coronary artery bypass graft and valve surgery | 393 (11.4%) | 6 (14%) | 0.8 |
| Re-operative cardiovascular surgery | 420 (12.2%) | 8 (18.2%) | .3 |
| Double valve surgery | 402 (11.7%) | 9 (20.5%) | 0.1 |
| Triple valve surgery | 12 (0.3%) | 0 (0%) | 1 |
| Aortic valve replacement | 1,339 (38.8%) | 18 (40.9%) | 0.9 |
| Mitral valve surgery | 1,366 (39.6%) | 21 (47.7%) | 0.4 |
| Mitral valve repair | 776 (22.5%) | 12 (27.3%) | 0.6 |
| Aorta cross-clamped | 733 (21.3%) | 9 (20.5%) | † |
| Heart fibrillating | 43 (1.2%) | 3 (6.8%) | † |
| Mitral valve replacement | 590 (17.1%) | 9 (20.5%) | 0.7 |
| Aorta cross-clamped | 486 (14%) | 8 (18.2%) | † |
| Heart fibrillating | 104 (3%) | 1 (2.3%) | † |
| Maze procedure | 428 (12.7%) | 5 (11.4%) | 1 |
| Femoral cannulation | 1855 (53.8%) | 22 (50%) | 0.73 |
| Axillary cannulation | 108 (3.1%) | 3 (6.8%) | 0.3 |
| Direct aortic cannulation | 1,395 (40%) | 19 (43.2%) | 0.83 |
| Off-pump coronary artery bypass surgery | 90 (2.6%) | 0 (0%) | 0.54 |
| Aortic cross-clamp time (minutes, median, IQR) | 78 (58-103) | 74 (61-102) | 0.9 |
| Cardiopulmonary bypass time (minutes, median, IQR) | 110 (86-139) | 109 (91-156) | 0.4 |
∗ Other cardiac surgeries included septal defect closures, ascending aortic arch surgery, and intra-cardiac mass resections.
† Sample size too small for adequate statistical comparison.
Multivariable analysis demonstrated that the CHA 2 DS 2 VASc score was the only independent predictor of postoperative strokes, whereas neither a history of preoperative AF nor the presence of postoperative AF were associated with the development of postoperative strokes ( Table 3 ). Furthermore, the risk of postoperative strokes increased with each rise in the CHADS 2 and CHA 2 DS 2 VASc scores ( Figures 1 and 2 ).
| Variable | Multivariate odds ratio | Multivariate confidence interval | p-value |
|---|---|---|---|
| Pre-operative anti-platelet use | 1.83 | 1.0 – 3.4 | 0.058 |
| History of atrial fibrillation | 1.86 | 0.9 – 3.9 | 0.097 |
| Post-operative atrial fibrillation | 1.86 | 0.9 – 3.8 | 0.089 |
| CHA 2 DS 2 VASc | 1.25 | 1.1 – 1.5 | 0.014 |
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