Paroxysmal atrial fibrillation : prognostic implications

Abstract

This thesis is based on data from the Stockholm Cohort on Atrial Fibrillation (SCAF). This cohort consists of all 2912 patients with atrial fibrillation or flutter who were treated as in or outpatients at South Hospital in Stockholm or at Gustavsberg Primary Care Centre during 2002. The patients have been followed prospectively through medical records complemented by information from national registers of hospitalisations and mortality.

In Study I we evaluated the incidence of ischaemic and haemorrhagic stroke in 855 patients with paroxysmal atrial fibrillation (PxAF). We found that the stroke incidence was approximately twice as high as in the general population and similar to that of permanent atrial fibrillation (PermAF). Warfarin prophylaxis appeared to be as efficient in Px AF as in PermAF. The incidence of cerebral bleedings was low and not higher in patients using warfarin than in patients using aspirin.

In Study II we investigated the mortality among patients with PxAF and found it to be higher than expected from age and sex adjusted specific rates in the general population. The standardized mortality ratio (SMR) was 1.6. Patients with PxAF died more often than expected from myocardial infarction (SMR 2.4), heart failure (SMR 2.6) and cardiovascular disease in general (SMR 2.1). The increased mortality in PxAF appears to be present mainly in subjects with concomitant cardiovascular co-morbidity. Treatment with warfarin was found to be associated with improved survival in PxAF patients.

In Study III we studied how current guideline recommendations are translated into clinical practice. We found that approximately half of the patients who ought to have warfarin also had received such treatment. Undertreatment was particularly common in patients with PxAF and in patients aged >80 years. Important risk factors for stroke did not increase the likelihood of warfarin treatment.

In Study IV we investigated whether patients who remain in sinus rhythm after DCcardioversion obtain any prognostic benefit from having normal sinus rhythm restored. From the SCAF-cohort 361 patients who had been DC-cardioverted were studied. Patients without known relapse to atrial fibrillation within three months after cardioversion had a lower incidence of all-cause mortality (HR 0.5, 95% C.I. 0.3-1.0) as well as a lower incidence of the composite end point consisting of death, ischaemic stroke, myocardial infarction or hospitalization for heart failure (HR 0.5, 95% C.I. 0.3-0.8) after multivariable adjustment.

Conclusions: PxAF is associated with increased morbidity and mortality which is similar to that of PermAF. Underlying cardiovascular disease seems to account for most of this. Therefore it is essential to diagnose and treat any underlying cardiovascular disease in PxAF-patients. Warfarin seems to be helpful, not only against stroke but also against premature cardiovascular death. Therefore it is essential to provide PxAF-patients with adequate anticoagulant treatment unless there are clear contraindications for such therapy. Our results suggest that restoration and maintenance of sinus rhythm may improve the prognosis in patients with atrial fibrillation. Therefore, we propose that eligible patients should be given an opportunity to be restored to sinus rhythm before atrial fibrillation is accepted as permanent.