Clinical significance of late high-degree atrioventricular block in patients with left ventricular dysfunction after an acute myocardial infarction—A Cardiac Arrhythmias and Risk Stratification After Acute Myocardial Infarction (CARISMA) substudy Uffe Jakob Ortved Gang, MD, PhD, a,b,f Christian Jøns, MD, PhD, a,b,f Rikke Mørch Jørgensen, MD, a,f Steen Zabell Abildstrøm, MD, PhD, c,f Marc D. Messier, PhD, d,f Jens Haarbo, MD, DMsc, a,f Heikki V. Huikuri, MD, DMsc, e,f and Poul Erik Bloch Thomsen, MD, DMsc a,f Copenhagen, Denmark; Maastricht, The Netherlands; and Oulu, Finland Background High-degree atrioventricular block (HAVB) is a frequent complication in the acute stages of a myocardial infarction associated with an increased rate of mortality. However, the incidence and clinical significance of HAVB in late convalescent phases of an AMI is largely unknown. The aim of this study was to assess the incidence and prognostic value of late HAVB documented by continuous electrocardiogram (ECG) monitoring in post-AMI patients with reduced left ventricular function. Methods The study included 286 patients from the CARISMA study with AMI and left ventricular ejection fraction of 40% or less. An insertable loop recorder was implanted 5 to 21 days after AMI for incessant arrhythmia surveillance. Furthermore, ECG documentation was supplemented by a 24-hour Holter monitoring conducted at week 6 post-AMI. The clinical significance of HAVB occurring more than 21 days after AMI was examined with respect to development of major heart failure events and major ventricular tachyarrhythmic events. Results During a median follow-up of 1.9 years (interquartile range 0.9-2.0), late HAVB was documented in 30 patients. The risk of major heart failure events (hazard ratio [HR] 4.08 [1.38-12.09], P = .01) and major ventricular tachyarrhythmic events (HR = 5.41 [1.88-15.58], P = .002) were significantly increased in patients who developed late HAVB. Conclusion High-degree atrioventricular block documented by continuous ECG monitoring occurring more than 3 weeks after AMI is a frequent complication in post-AMI patients with left ventricular dysfunction. Furthermore, HAVB is associated with ominous prognostic implications of both potentially lethal arrhythmias and heart failure. (Am Heart J 2011;162:542-7.) Development of in-hospital high-degree atrioventricular block (HAVB) after an acute myocardial infarction (AMI) has been associated with an increased rate of both short- and long-term mortality. 1-13 The incidence of HAVB during hospitalization after AMI is 4% to 7% in the era of acute revascularization therapy. 6-10 Patients with heart failure, preexisting or acutely emerged, are particularly prone to HAVB development. 10-12 In addition, age, female sex, smoking, hypertension, diabetes, and inferiorly located AMI have been identified as risk factors of HAVB. 5-7,10 High-degree atrioventricular block induced by an inferior infarction is most often located above the His-bundle, and the odds of a transient HAVB are better than after an anterior infarction, which more frequently causes a more distally located HAVB. 11,14 Regardless of the location of the AMI and the duration of the conduction disturbance, HAVB development has been associated with both a significantly increased likelihood of ventricular tachyarrhythmias and a From the a Department of Cardiology, Gentofte University Hospital, Copenhagen, Denmark, b Department of Internal Medicine, Glostrup University Hospital, Copenhagen, Denmark, c Department of Cardiology, Bispebjerg University Hospital, Copenhagen, Denmark, d Medtronic Bakken Research Centre, Maastricht, The Netherlands, and e Department of Internal Medicine, Oulu University Hospital, Finland. f On behalf of the CARISMA Investigators. Clinical Trials.gov identifier NCT00145119. Submitted January 4, 2011; accepted June 5, 2011. Reprint requests: Uffe Jakob Ortved Gang, MD, PhD, Copenhagen University Hospital Glostrup, Department of Internal Medicine, Nordre Ringvej 57, 2600 Glostrup, Denmark. E-mail: dr.gang@dadlnet.dk 0002-8703/$ - see front matter © 2011, Mosby, Inc. All rights reserved. doi:10.1016/j.ahj.2011.06.021