Prediction of fatal or near-fatal cardiac arrhythmia events in patients with depressed left ventricular function after an acute myocardial infarction

Abstract

Aims: To determine whether risk stratification tests can predict serious arrhythmic events after acute myocardial infarction (AMI) in patients with reduced left ventricular ejection fraction (LVEF < or = 0.40).

Methods and results: A total of 5869 consecutive patients were screened in 10 European centres, and 312 patients (age 65 +/- 11 years) with a mean LVEF of 31 +/- 6% were included in the study. Heart rate variability/turbulence, ambient arrhythmias, signal-averaged electrocardiogram (SAECG), T-wave alternans, and programmed electrical stimulation (PES) were performed 6 weeks after AMI. The primary endpoint was ECG-documented ventricular fibrillation or symptomatic sustained ventricular tachycardia (VT). To document these arrhythmic events, the patients received an implantable ECG loop-recorder. There were 25 primary endpoints (8.0%) during the follow-up of 2 years. The strongest predictors of primary endpoint were measures of heart rate variability, e.g. hazard ratio (HR) for reduced very-low frequency component (<5.7 ln ms(2)) adjusted for clinical variables was 7.0 (95% CI: 2.4-20.3, P < 0.001). Induction of sustained monomorphic VT during PES (adjusted HR = 4.8, 95% CI, 1.7-13.4, P = 0.003) also predicted the primary endpoint.

Conclusion: Fatal or near-fatal arrhythmias can be predicted by many risk stratification methods, especially by heart rate variability, in patients with reduced LVEF after AMI.

Trial registration: ClinicalTrials.gov NCT00145119.

Figure 1

Study Flow Chart. *Major reasons for exclusions from the study were refusal of the patient or the attending physician treating the patient for participation in the study (n = 380), the inability of the patient to participate in the study due to other serious illness (n = 312), planned coronary bypass graft surgery (n = 184) or death (n = 89) before the implantation of a loop-recorder and/or the risk stratification tests. AMI, acute myocardial infarction; EP, electrophysiological; ILR, implantable loop-recorder; SAECG, signal-averaged electrocardiogram; TWA, T-wave alternans.

Figure 2

Clinical presentation, type of documented arrhythmia, and the mode of documentation of primary endpoints. ICD, implantable cardioverter-defibrillator; ILR, implantable loop-recorder; VT, ventricular tachycardia; VF, ventricular fibrillation.

Figure 3

Adjusted hazard ratios (HR) with 95% confidence intervals of the variables as predictors of primary endpoint. HR are calculated from pre-defined threshold values of continuous variables. HR are adjusted for age, prior myocardial infarction, history of congestive heart failure and diabetes The variables are listed in descending order starting with the highest HR for each risk stratification method. Abbreviations: see in Table 3.

Figure 4

Kaplan–Meier estimate of the time from MI to primary endpoint, stratified by inducible sustained monomorphic ventricular tachycardia (MMVT) (panel A) and by reduced very-low frequency spectral component (VLF) of heart rate variability (panel B).