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.

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.