How common is asymptomatic paroxysmal atrial fibrillation in chronic heart failure?

To the Editor,

We are writing in response to the original article by Corell et al. entitled “Paroxysmal atrial fibrillation in outpatients with chronic heart failure” 1 in which the presence of paroxysmal atrial fibrillation (PAF) was determined from a single period of external loop recording for 48 hours in patients with confirmed heart failure.

We feel that the validity of Corell et al.'s conclusions that ‘in outpatients with heart failure due to LV dysfunction PAF is uncommon’ is questionable since it is likely that the methodology used may have led to a gross under-estimation of the incidence of asymptomatic PAF in their cohort studied.

It is now well established that asymptomatic episodes of AF can be identified on dual chamber or biventricular pacemakers by episodes of mode-switching with an atrial rate of >200 for more than 30s 2. By adopting such detection strategies in patients with known history of paroxysmal AF Israel et al. demonstrated via pacemaker that 88% of patients had paroxysms of AF of which 38% were completely asymptomatic and only 46% were documented by ECG or holter monitoring. We have recently completed a study in heart failure patients thought to be in sinus rhythm in which we report that 27% of the patients thought to be constantly in sinus rhythm were having asymptomatic episodes of PAF through analysis of biventricular pacemaker downloads 3 and that the burden of AF in these patients is in the order of 1% 4. It is therefore likely that using 48hr holter monitoring will miss this relatively low burden of AF and lead to under reporting of this problem, as probably happened in this study.

However, we appreciate that the clinical relevance of such low burden asymptomatic paroxysms of AF remains largely unknown. Yours sincerely, Jane Caldwell, Mamas Mamas, Clifford Garratt and Ludwig Neyses