Atrial Fibrillation: Interatrial Block May Be an Underdiagnosed and Easily Recognizable Risk Factor

Abstract

I read with interest the excellent article by Morin et al1Morin D.P. Bernard M.L. Madias C. Rogers P.A. Thihalolipavan S. Estes III, N.A.M. The state of the art: atrial fibrillation epidemiology, prevention, and treatment.Mayo Clin Proc. 2016; 91: 1778-1810Abstract Full Text Full Text PDF PubMed Scopus (100) Google Scholar published in the December 2016 issue of Mayo Clinic Proceedings. As the authors noted, a myriad of risk factors for atrial fibrillation have been identified. Among these risk factors, interatrial block (IAB) should be considered. This type of block has an easily recognizable electrocardiographic pattern2Fernández-Fernández FJ. Prolonged P wave with biphasic morphology in the inferior leads. Eur J Intern Med. In press. http://dx.doi.org/10.1016/j.ejim.2016.09.030.Google Scholar but is frequently underrecognized in clinical practice. Interatrial block is characterized by the presence of a prolonged P wave that equals or exceeds 120 ms.3Bayés de Luna A. Platonov P. Cosio F.G. et al.Interatrial blocks: a separate entity from left atrial enlargement; a consensus report.J Electrocardiol. 2012; 45: 445-451Abstract Full Text Full Text PDF PubMed Scopus (246) Google Scholar This disorder of impaired atrial conduction may be of first (partial), second (transient interatrial block), or third (advanced) degree. A partial block is characterized by a P-wave duration of 120 ms or longer, and an advanced block is indicated by a P-wave duration of 120 ms or longer and a biphasic (+/-) pattern in leads II, III, and aVF. This biphasic morphology is due to retrograde activation of the left atrium caused by a complete block in the Bachmann bundle. In IAB, intra-atrial and interatrial conduction delays lead to dispersion of refractory periods and participate in initiating and maintaining reentry circuits, facilitating reentrant atrial arrhythmias, especially atrial fibrillation and atrial flutter.4Conde D. Baranchuk A. Bayés de Luna A. Advanced interatrial block as a substrate of supraventricular tachyarrhythmias: a well recognized syndrome.J Electrocardiol. 2015; 48: 135-140Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar Interatrial block may be another major underlying etiology for apparently thromboembolic strokes that occur in the absence of clinical atrial fibrillation.5O'Neal W.T. Kamel H. Zhang Z.M. Chen L.Y. Alonso A. Soliman E.Z. Advanced interatrial block and ischemic stroke: the Atherosclerosis Risk in Communities Study.Neurology. 2016; 87: 352-356Crossref PubMed Scopus (65) Google Scholar The association of advanced IAB with atrial arrhythmias constitutes an arrhythmogenic syndrome, also termed Bayés syndrome. Along with abnormal P-wave terminal force in lead V1 and atrial fibrillation, advanced IAB is considered among the most important atrial electrocardiographic predictors of ischemic stroke.6Hughes T.M. Worrall B.B. Acute interatrial block is a distinct risk factor for ischemic stroke.Neurology. 2016; 87: 344-345Crossref PubMed Scopus (7) Google Scholar The State of the Art: Atrial Fibrillation Epidemiology, Prevention, and TreatmentMayo Clinic ProceedingsVol. 91Issue 12PreviewAs the most common sustained arrhythmia in adults, atrial fibrillation (AF) is an established and growing epidemic. To provide optimal patient care, it is important for clinicians to be aware of AF's epidemiological trends, methods of risk reduction, and the various available treatment modalities. Our understanding of AF's pathophysiology has advanced, and with this new understanding has come advancements in prevention strategies as well as pharmacological and nonpharmacological treatment options. Full-Text PDF In Reply—Atrial Fibrillation: Interatrial Block May Be an Underdiagnosed and Easily Recognizable Risk FactorMayo Clinic ProceedingsVol. 92Issue 4PreviewWe appreciate Dr Fernández-Fernández’s interest in our work1 as well as his comments. Full-Text PDF