Predictors of impaired heart rate variability and clinical outcome in patients with acute myocardial infarction treated by primary angioplasty

Abstract

To investigate the determinants and prognostic value of heart rate variability (HRV) in acute myocardial infarction (AMI) patients treated by percutaneous coronary intervention (PCI). We studied 64 patients with AMI (58.4 +/- 10 years, 56 men), treated by PCI within 12 h of symptom onset. Patients underwent 24-h electrocardiographic Holter recording before discharge. HRV was measured in the time- and frequency-domain. Cardiac events were assessed at 6 months. At univariate analysis, Thrombolysis in Myocardial Infarction (TIMI) flow grade < 3 was significantly predictive of reduced frequency-domain variables. On multivariate analysis, diabetes and pre-PCI time > 6 h were the strongest predictors of depressed HRV, with peak creatine kinase myocardial-type and lower left ventricular ejection fraction being also variably correlated with impaired HRV. At 6-month follow-up, seven patients (10.1%) had cardiac events (one AMI, six revascularization procedures). A low standard deviation of RR intervals was a significant predictor of events (P = 0.009), although only age was associated with the endpoint (P = 0.05) on multivariate analysis. Our study shows that, in AMI patients treated by primary PCI, a delay in coronary revascularization and AMI extension are key factors for determining depressed HRV.