Relation of Interatrial Block to New-Onset Atrial Fibrillation in Patients With Chagas Cardiomyopathy and Implantable Cardioverter-Defibrillators Andres Enriquez, MD a , Diego Conde, MD b , Francisco Femenia, MD c , Antoni Bayés de Luna, MD d , Antonio Ribeiro, MD e , Claudio Muratore, MD f , Mariana Valentino, MD g , Enrique Retyk, MD h , Nestor Galizio, MD i , Wilma M. Hopman, MA a , and Adrian Baranchuk, MD a, * Chagas cardiomyopathy is an endemic disease in Latin America. A significant proportion of patients develop atrial fibrillation (AF), which may result in stroke and increased morbidity or mortality. Interatrial block (IAB) has been associated with the development of AF in different clinical scenarios. The aim of our study was to determine whether IAB can predict new-onset AF in patients with Chagas cardiomyopathy and implantable cardioverter- defibrillators (ICDs). We conducted a retrospective study of patients with Chagas cardio- myopathy and ICDs from 14 centers in Latin America. Demographics, clinical, and device follow-up were collected. Surface electrocardiograms were scanned at 300 dpi and maxi- mized 38. Semiautomatic calipers were used to determine P-wave onset and offset. Partial IAB was defined as a P wave of >120 ms and advanced IAB as a P wave of >120 ms with biphasic morphology (–) in inferior leads. AF events and ICD therapies were reviewed during follow-up by 2 independent investigators. A total of 80 patients were analyzed. Mean age was 54.6 – 10.4 years, and 52 (65%) were male. Mean left ventricular ejection fraction was 40 – 12%. IAB was detected in 15 patients (18.8%), with 8 (10.0%) partial and 7 (8.8%) advanced. During a follow-up of 33 – 20 months, 11 patients (13.8%) presented with new AF. IAB (partial D advanced) was strongly associated with new AF (p <0.0001) and inappropriate therapy by the ICD (p [ 0.014). In conclusion, IAB (partial D advanced) predicted new-onset AF in patients with Chagas cardiomyopathy and ICDs. Ó 2014 Elsevier Inc. All rights reserved. (Am J Cardiol 2014;-:-e-) Chagas disease, caused by the parasite Trypanosoma cruzi, affects 8 to 10 million subjects in Latin America, and almost 25% of them will develop chronic myocardial dis- ease after years or decades. 1 Up to 1/5 of patients will develop atrial fibrillation (AF), 2 which is associated with systemic thromboembolism and poor prognosis. 3,4 Intera- trial block (IAB), defined as a prolonged P wave (>120 ms) on a 12-lead electrocardiogram (ECG), has been associated with the development of AF in many clinical settings, probably through delayed and heterogeneous electrical activation of the left atrium (LA). 5e10 The aim of our study was to determine whether IAB can predict new-onset AF in patients with Chagas cardiomyopathy and implantable cardioverter-defibrillators (ICDs). Methods The present study was a retrospective analysis of patients with Chagas cardiomyopathy and an ICD implanted for pri- mary or secondary prevention at 14 Latin American centers included in the Fragmented ECG in Chagas Cardiomyopathy Study. 11 The inclusion criteria were (1) Chagas cardiomyopathy diagnosed by positive serologic tests and classic criteria, including living in endemic areas, ECG, and chest x-ray criteria, (2) ICD implanted for primary or secondary pre- vention of sudden cardiac death, and (3) sinus rhythm. Patients with history of AF were excluded. Demographics, clinical, and device follow-up were collected. The study protocol was approved by the ethics committee of each institution. A standard 12-lead ECG (filter 150 Hz, 25 mm/s, 10 mm/ mV) was obtained in all patients before the device implan- tation. The ECGs were directly scanned at 300 dpi and reviewed at a core laboratory center in Queen’s University by 2 blinded investigators (AE and AB). Disagreement was solved by consensus. The images were amplified 10 and the P-wave duration was measured using semiautomatic calipers (Iconico, New York). The onset of the P wave was identified as the point of initial upward or downward deflection from the baseline and the P-wave offset as the returning point of the waveform to the baseline. Partial IAB was defined as a P-wave duration of >120 ms without a Queen’s University, Kingston, Ontario, Canada; b Instituto Cardiovas- cular de Buenos Aires, Buenos Aires, Argentina; c Santa Clara Red de Clínicas, Mendoza, Argentina; d Cardiovascular Research Center, CSIC- ICCC, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain; e Universidade Federal de Minais Gerais, Belo Horizonte, Brazil; f Hospital Fernandez, Buenos Aires, Argentina; g Sanatorio Delta, Rosario, Argentina; h Hospital Castex, Buenos Aires, Argentina; and i Fundacion Favaloro, Buenos Aires, Argentina. Manuscript received January 27, 2014; revised manuscript received and accepted February 21, 2014. See page 4 for disclosure information. *Corresponding author: Tel: (613) 549-6666x3801; fax: (613) 548- 1387. E-mail address: barancha@kgh.kari.net (A. Baranchuk). 0002-9149/14/$ - see front matter Ó 2014 Elsevier Inc. All rights reserved. www.ajconline.org http://dx.doi.org/10.1016/j.amjcard.2014.02.036