Prognostic value of heart rate variability after acute myocardial infarction

Abstract

Background: Prognosis after acute myocardial infarction (AMI) may be influenced by autonomic dysfunction that can be evaluated by assessment of heart rate variability (HRV). Its predictive value resulted from studies performed prior to large scale use of reperfusion therapy. We assessed the prognostic value of HRV parameters 1 year after AMI in patients treated conventionally or by a reperfusion method in the first 12 hours from onset.

Material/methods: We included 463 consecutive patients with AMI (312 M, 151 F) 60.6+/-13.0 years old. 211 were treated by thrombolysis or primary PTCA, the other 251 patients receiving conventional therapy. Time-domain (SDNN, rMSSD) and frequency-domain (LF, HF, total power) HRV parameters were calculated from 24-hour Holter ECG recordings 10-20 days after AMI. The primary endpoint was one-year total mortality and sudden cardiac death.

Results: The incidence of cardiac death was 14.7%, while that of sudden death was 4.8%. Both were higher in patients treated conventionally. Patients treated by reperfusion had higher HRV parameters reflecting both vagal and sympathetic activity (SDNN, total spectral power) as well as those expressing only vagal output (rMSSD, HF power) than conventionally treated subjects. The variables independently correlating with 1-year survival were SDNN<50 msec, rMSSD<20 msec, LF/HF>2, non-sustained ventricular tachycardia, and left ventricular ejection fraction <40%.

Conclusions: HRV parameters have prognostic value independent from left ventricular ejection fraction and spontaneous ventricular arrhythmias one year after AMI. Reduction of mortality risk by reperfusion therapy does not decrease the prognostic utility of HRV after AMI.