Response to Drs. Fackrell and Mac Mahon

Abstract

To the Editor: We agree with Drs. Fackrell and Mac Mahon about the importance of a proper diagnosis of cardiac syncope. Cardiac syncope is associated with greater mortality than noncardiac syncope, and a detailed assessment of early symptoms could improve the strategy for reaching diagnosis as quickly as possible.1 However, Drs. Fackrell and Mac Mahon suspect an underdiagnosis of the incidence of cardiac syncope in Italian Group for the Study of Syncope in the Elderly (GIS Study).2 In this study, the prevalence of cardiac syncope was 14.7%, whereas neurally mediated syncope accounted for up to 66.6%. Because only two centers recruited patients from the emergency department in the GIS Study, some arrhythmic and myocardial ischemic episodes of syncope might have been missed, although a recent study of patients referred to emergency departments indicated the prevalence of cardiac syncope to be approximately 16%, a value similar to that obtained in the GIS Study.3 Regardless, the comments of Drs. Fackrell and Mac Mahon raise important questions. An implantable loop recorder (ILR) may be a helpful diagnostic tool, especially in syncope of unknown origin. A recent study demonstrated that, in 140 patients with syncope of unknown origin, ILR found an arrhythmic cause in 33 of 51 patients presenting with syncope during electrocardiogram recording.4 Moreover, the prevalence of unknown syncope was 10.1% in patients in the GIS Study. A clinical implication could be the identification of elderly patients presenting with dyspnea as an early symptom before syncope in those in whom the diagnostic algorithm indicates syncope of unknown origin.5 In these patients, ILR implantation should be strongly encouraged. Another intriguing consideration is that correct diagnosis of syncope in elderly people may be the result of a combination of multiple causes. As suggested by Drs. Fackrell and Mac Mahon, cardiac arrhythmias could be overlooked in some of the patients diagnosed with vasovagal syncope in our study.5 Accordingly, it has been demonstrated that multiple causes of syncope are frequent in elderly people; a single cause of syncope decreases (from 68.7% to 54.3%), whereas a double diagnosis increases (from 9.2% to 23.8%) in old with respect to adult patients.6 However, the majority of syncope resulting from multiple causes belong to the same syncope category (cardiac or noncardiac), and only a few patients (2.2%) appear to have a combination of cardiac (bradycardia) and noncardiac (vasovagal) causes.6 Thus, even if the GIS Study had missed syncopes with double diagnosis, their low prevalence should not invalidate the results and therefore the predictive value of early symptoms. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. Author Contributions: G. Galizia: preparation of letter. P. Abete: preparation of letter. A. Ungar: interpretation of letter. Sponsor's Role: None.