Mortality in patients with atrial fibrillation: improving or not?

Abstract

This editorial refers to ‘Mortality in patients with atrial fibrillation has significantly decreased during the last three decades: 35 years of follow-up in 1627 pacemaker patients’ † by S. Asbach et al. on page 391 Atrial fibrillation (AF) is the commonest sustained arrhythmia, with an increasing incidence. 1 With the increasing elderly population, the prevalence of AF is estimated to rise, conferring a significant mortality and morbidity. In the Framingham study, the presence of AF independently increased mortality in men by 1.5-fold and in women by 1.9-fold. 2 Given that the average lifetime risk of developing AF is 25% 3 and the high economic cost associated with AF, 4 it is clear that we are dealing with a condition with major public health implications. The mortality and morbidity associated with AF are probably not homogeneous when taking into consideration related co-morbidities, complications, and treatment strategies. The lowest risk group is probably that with the so-called ‘lone AF’, which is essentially a diagnosis of exclusion, where AF is associated with no obvious pre-disposing factor on thorough clinical history and examination, with a structurally normal heart on echocardiography, normal ECG (except for AF), normal blood tests, and normal chest X-ray. 5 As we recently highlighted, some series even report an increased mortality with lone AF patients. 6 This may reflect how hard we look for associated co-morbidities, and furthermore, as patients get older, new co-morbidities will intervene. 5 At the other extreme, the presence of AF in patients with acute coronary syndromes, 7 congestive cardiac failure, and in the post-operative setting conditions associated with greater risk of adverse events. For example, an analysis from the TRAndolapril Cardiac Evaluation (TRACE) 7 study reported AF to increase total mortality by 33%, with a risk ratio for sudden cardiac death (SCD) of 1.31 (95% CI: 1.07– 1.60; P , 0.009). Furthermore, the adjusted risk ratio of AF for non-SCD was 1.43 (95% CI: 1.21–1.70; P , 0.0001). Similarly, data from the Framingham Heart Study 8 reported that AF associated with the subsequent development of heart failure resulted in an increased mortality [men: hazard ratio (HR) 2.7, 95% CI: 1.9–3.7 and women: HR 3.1, 95% CI: 2.2–4.2]. Clearly, AF in association with heart disease is not a good combination. Perhaps what has attracted much interest in AF is the morbidity and mortality associated with stroke and thrombo-embolism. 9 Overall, AF increases the risk of stroke by up to 5-fold, but this risk is not homogeneous. 9,10 Stroke risk in AF is increased with the presence of associated stroke risk factors such as previous stroke, increasing age, hypertension, diabetes mellitus, and so on—with the risk being cumulative with increasing co-morbidities. 11,12 For example, this risk increases with age, with stroke occurring in 1.5% of the under 60 year olds and rising to 23.5% in the over 80s 11 and is further increased (for example) by concomitant hypertension. Given the improvements in the recognition and management of the co-morbid conditions associated with AF— especially hypertension, heart failure, and coronary artery disease—one would expect an improvement in the clinical outcome and prognosis of this arrhythmia. Is this really the case?