Atrial fibrillation in patients hospitalized with acute myocardial infarction: analysis of the china acute myocardial infarction (CAMI) registry

CAMI registry was the largest nationwide observational study to date for hospitalized patients with AMI throughout China. The major findings of present analysis were: 1) the overall incidence of AF was 3.0% in Chinese patients with AMI during hospitalization; 2) the risk of baseline profile was higher in patients with AF than patients without AF; 3) patients who developed AF were at a 1.88-fold higher risk of in-hospital mortality than patients without AF; and 4) although the majority of AMI patients complicated with AF received anticoagulation and antiplatelet therapy during hospitalization, only 5.1% of them were discharged on warfarin, and 1.7% were discharged on both warfarin and DAPT.

In this nationally representative study, it firstly defined an AF incidence of 3.0% in contemporarily treated AMI patients in China. It was much lower compared to the reported data in other countries, ranging from 2.3 to 21% [1–12]. It may be resulted from some possible explanations. First, age was the most commonly reported risk factor for AMI complicated with AF [21, 22], and the low rate of AF in CAMI patients may be associated with an overall lower mean age of 63 years in samples. Second, 48.0% of overall patients in CAMI received reperfusion therapy (42.2% PCI). In previous studies, widespread use of reperfusion therapy, especially PCI, was associated with a notable decline of AF incidence [11, 23]. Third, the majority of patients in CAMI were treated with angiotensin-converting enzymes/angiotensin receptor inhibitors or ?-blockers, and trials evaluating the effects of these drugs in patients with AMI have reported lower incidence rates of AF, although mainly making effects on late developing AF [24, 25]. Fourth, ethnic differences may also account for the wide incidence range of AMI complicated AF among different countries. A recently published study reported a low AF incidence of 2.7% in Arabian Gulf patients with acute coronary syndrome (ACS) [4].

Consistent with previous studies [1–12], in CAMI registry, higher-risk baseline clinical characteristics could be observed in AMI patients complicated with AF during hospitalization, including older age, a greater cardiovascular risk factor burden, more comorbidities, poorer left ventricular function, and higher clinical risk scores. The present study also documented that AMI patients with AF were less likely to receive reperfusion/revascularization than those without AF. For the patients with older age and more comorbidities, more conservative management approach would be selected by the physicians [26].

It indicated that AF increased the risk of morbidity and mortality in patients with ACS, and that this association would be mediated to a greater or lesser extent by various comorbidities [1]. However, because of differences in study design and data availability, including study population, AF classification, sample size, and follow-up duration, the association between AF development in ACS and increased in-hospital mortality remained to be controversial. Some variables were reported to be independently associated with AF [2–9], while others reported no association [10–12]. In present analysis, the data was obtained from the CAMI registry, which was a large-scale, national and contemporary registry project for AMI patients in China [20]. The in-hospital mortality was significantly higher in patients with AF in unadjusted analysis. In addition, AF was also an independent multivariate risk factor of mortality after adjusting for possible confounders, although to an attenuated extent. With the consistency of findings, the association was further underscored in unadjusted and adjusted analyses.

The risk of bleeding may be increased by the anticoagulants treatment combined with DAPT therapy for stroke prevention in ACS patients with AF [27, 28]. However, current guidelines and consensus recommend a combination of warfarin and DAPT (triple therapy), with adjustment of duration according to hemorrhagic risk [13, 14]. Nonetheless, in previous studies, it documented that this triple therapy was largely underused, with a frequency ranged from 5.7 to 15.6% [15–17]. In the CAMI national registry, only 5.1% of AMI patients with AF were discharged on warfarin, and the proportion of warfarin in combination with DAPT was even as low as 1.7%. The latter striking gap in China might be secondary to many factors: the uncertainty about the benefits of intense anticoagulation in these high risk patients, inadequate provider knowledge, structural inadequacies of healthcare delivery systems, and/or concern about potential violence and litigation from patients or their families due to complications associated with treatment [29–31]. In addition, although new direct oral anticoagulants (dabigatran, rivaroxaban, and apixaban) have been approved for stroke prevention in non-valvular AF patients [13], the CAMI registry indicated that these new anticoagulants have not been applied yet in AMI patients with AF in China.

CAMI registry was compared with REAL (REgistro regionale AngiopLastiche dell’Emilia-Romagna) registry. REAL registry was a multi-center, large scale, prospective study [32–35]. It aimed to collect the clinical data of coronary interventional cases from 4 million residents in Emilia- Romagna. 13 hospitals participated in this registry. The data could be retrieved in database. Many studies were performed based on this database [36]. Similar to REAL registry, CAMI has collected information of patients with acute myocardial infarction (AMI), including the clinical data, treatment, efficacy and prognosis. It aimed to improve the overall treatment efficacy of AMI in China. However, CAMI has only focused the patients from China. Different from REAL registry, CAMI has involved 108 hospitals in Chinese mainland and the hospitals differed in levels in CAMI registry. In addition, the population base was larger in CAMI registry in China. Finally, the involved cases were updated (since 2013). The study based on CAMI would be promising in improving the treatment efficacy of AMI in China.