Atrial fibrillation may be a hidden factor for the development of cognitive impairment in patients with heart failure.

To the editor

We read the article entitled ‘Cognitive impairment in heart failure patients’ by Leto, et al.[1] with great interest. In this review, they demonstrated pathophysiological determinants of cognitive impairment in heart failure (HF) population.

HF prevalence is increasing in the general population throughout the world. As HF is a complex clinical entity, underlying mechanisms with HF and cognitive impairment are mixed and intertwined. HF is a well known risk factor for dementia and functional brain abnormalities. Co-morbidities such as hypertension and diabetes are main reasons for the association between HF and cognitive impairment as well as decreased cerebral perfusion due to systolic dysfunction. Medications in HF populations also play a role in development of cognitive impairment through side effects on cerebral perfusion.[2]

In the present review, the authors pointed out important variables that can be related with HF and cognitive impairment such as left ventricular ejection fraction, systolic and diastolic blood pressure, NYHA functional class and B-type natriuretic peptide. However, atrial fibrillation (AF) which is a most prevalent arrhythmia in general population has also shown to be related to cognitive decline.[3] Furthermore, due to the silent attacks, undiagnosed episodes of paroxysmal AF have been frequently encountered in this subjects. The incidence of AF was increased in the elderly patients. The prevalence of AF was found to be 9% in individuals > 80 years of age and 0.1% in subjects < 55 years of age.[4] These data are derived from the trials in which the diagnosis was based on a 12-lead electrocardiogram obtained during an office visit. According to the duration of the episodes, AF is classified into 3 types: paroxysmal AF, persistent AF, and permanent AF. While the other types of AF can be easily diagnosed with routine 12-lead ECG, paroxysmal AF may be overlooked. In order to determine attacks of paroxysmal AF, ambulatory monitoring is required. Therefore, it is presumed that the real-world prevalence of AF is higher than those determined in the trials.

The cognitive impairment due to AF in elderly patients is both related with micro-emboli and a decline in cerebral perfusion. It seems that AF may exacerbate HF and subsequent cerebral blood flow reduction. Independently from its type, AF increases the risk of thromboembolism five times.[4] CHADS-VASc scoring system has been using in patients with AF in order to quantify the risk for thromboembolism. According to this scoring system, existence of congestive heart failure, hypertension, age 65 to 74 years, age ≥ 75 years (doubled risk), diabetes mellitus, prior stroke or transient ischemic attack or thromboembolism (doubled risk), vascular disease and female gender are risk factors for thromboembolic stroke in patients with AF.[5] It has been particularly indicated in this scoring system that the embolic risk of the elderly people with AF is as high as the patients with prior stroke. With the aging population in our modern world, it is obvious to be an incremental rise in the prevalence of AF. Furthermore, it is important to shed light on the relationship between cognitive impairment and AF as a main problem in patients with HF, so that preventative efforts will lead way to reduce the burden of cognitive impairment in HF patients. Therefore, in a review addressing cognitive impairment in HF population, we believe that discussing AF might be useful for researchers dealing with this group of patients.