Introduction
New-onset atrial fibrillation (NOAF) is a common arrhythmia during acute myocardial infarction (AMI), with a incidence ranging from 3 to 20% [
1]. The development of NOAF in AMI patients has been proved as an independent factor of short- and long-term mortality [
1,
2] Therefore, early identification of patients with high risk of NOAF is essential to prevent complications and improve prognosis. Previous studies have demonstrated several risk factors associated with NOAF, such as older age, B-type natriuretic peptide (BNP), high sensitive c-reactive protein (hs-CRP) and left atrium diameter (LAD) [
3‐
6]. However, valid risk stratification model to predict NOAF during AMI remains unclear, especially in elderly AMI population.
The CHADS2 and the CHA2DS2-VASc score have been demonstrated as good predictors of stroke risk in patients with non-valvular atrial fibrillation (NVAF) [
7,
8]. However, the discriminate power seems unsatisfactory when applying these two score models in AMI population for the prediction of NOAF [
9,
10]. The aim of our study was to identify risk factors of NOAF in elderly patients hospitalized for AMI, and determine whether the CHA2DS2-VASc score combined with admission biomarkers, such as hs-CRP, can be a valid model to predict NOAF.
Discussion
The main findings of the present study were: (1) older age and high hs-CRP were two independent risk factors of NOAF in elderly Chinese AMI patients. (2) the CHA2DS2-VASc score system is a convenient model to predict post-AMI NOAF with acceptable but unsatisfactory discriminatory ability. The predictive value of the score can be significantly enhanced by combing with hs-CRP.
Occurrence of NOAF during the course of AMI is a common phenomenon and it is associated with worse prognosis such as increased thromboembolic events, heart failure (HF) and all-cause mortality [
1,
2,
20]. The incidence of post-AMI NOAF was 9.65% in our study, which is consistent with the incidence reported in previous studies (3–20%) [
1,
14]. Moreover, the in-hospital mortality was significant higher in NOAF group (10% vs. 1.06%,
P < 0.001). Most NOAF (7.07%) developed after 24 h after admission (late-NOAF) with the ratio of late-NOAF to early-NOAF was nearly 3 to 1, similar results were reported in former surveys [
14,
21].
Several risk factors of post-AMI NOAF have been reported in previous studies, such as older age, higher Killip class, hs-CRP, BNP, LAD and lower LVEF [
3,
5,
6,
22]. For instance, a study by Wang et al. showed that older age is independently related to NOAF in patients with ACS, and similar conclusions were showed in some other studies [
3,
5,
23]. In the present study, older age was still an independent risk factor of post-AMI NOAF, even we only focused on elderly population. A study by Parashar et al. demonstrated that admission biomarkers such as hs-CRP and NT-proBNP were independently associated with NOAF, irrespective of gender and race [
6]. We observed a similar results in our study as well. However, after multivariate logistic regression analyses, only one admission blood biomarker, hs-CRP, was independent risk factor of NOAF in elderly AMI population.
The mechanisms for the association between increased hs-CRP and NOAF is not entirely clear. Previous studies suggest that inflammation is involved in the development and persistence of AF [
9,
24]. Hs-CRP is a simple biomarker for the magnitude of inflammation and higher hs-CRP level observed in NOAF group may suggest a potential link between the more severe systemic inflammation caused by myocardial necrosis and the development of NOAF after AMI [
25]. Moreover, CRP can bind to the phosphocholine groups exposed in the membrane of necrotic cardiomyocyte, causing the activation of complement and thus leading to more intense CRP deposition and local inflammation, which may facilitate the genesis and development of post-AMI NOAF [
26]. In our study, when elderly AMI patients present with hs-CRP > 21.25 mg/L at admission, they are more likely to develop NOAF during hospitalization.
The CHADS2 and the CHA2DS2-VASc score are used for thromboembolic risk stratification and have been recommended by modern guideline in the management of patients with NVAF [
27]. However, the discriminative value of these two score models in predicting post-AMI NOAF was unsatisfactory [
9,
10]. In the study by Lau et al., when applying the CHADS2 and the CHA2DS2-VASc score for the prediction of post-AMI NOAF, the discriminate power was relatively poor as evidenced by a AUC of 0.632 and 0.676, respectively [
10]. In our study, the CHADS2 and the CHA2DS2-VASc score were significantly higher in NOAF group, and we observed a similar discriminate power evidenced by AUC (0.624 and 0.687, respectively). These evidences also illustrating the need for a scoring model that is more accurate than the CHA2DS2-VASc score in predicting post-AMI NOAF.
For this purpose, we combined the CHA2DS2-VASc score with hs-CRP. The AUC of the combined model was statistically greater than that of the CHA2DS2-VASc score (0.791 vs. 0.687,
P = 0.008) after Z test, suggesting the diagnostic performance of this new model to predict NOAF in elderly AMI patients was relatively high and significantly better than the CHA2DS2-VASc score alone. With the use of this new combined model, it will be convenient to identify elderly patients with AMI who are at higher risk to develop NOAF, and help clinicians in making therapeutic strategies to improve prognosis. For instance, previous studies had proved the protective value of statins use against AF in ACS patients, thus aggressive statin therapy might be beneficial [
28]. Moreover, AF patients benefit from anticoagulant therapy, early identification of patients with higher risk of NOAF and early diagnosis of NOAF has clinical importance for a timely initiation and adjustment of anticoagulant therapy [
27]. However, these beneficial effects should be verified in future randomized controlled trials.
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