Introduction: The Multicenter ICD Risk Stratification Study (M2Risk Study) was designed to determine which clinical and novel ECG-based variables will predict arrhythmic events in post-infarction patients with EF?35%.
Methods: Study population consisted of post-infarction patients with EF?35% who received their ICDs for primary prevention of mortality. At enrollment, the following were collected: routine clinical data, 12-lead ECG, 24-hour Holter monitoring (Mortara Instruments), signal-averaged ECG [SAECG] (Arrhythmia Research Technology), and exercise-induced T wave alternans [TWA] (Cambridge Heart). The ECG-based parameters included: heart rate variability, heart rate turbulence, deceleration capacity, ventricular arrhythmias on the 24-hour Holter, QRS duration, QRS complexity, QTc duration, T wave complexity, SAECG-derived:total QRS root mean square voltage (TRMS) and late potentials parameters (fQRSd, RMS, LAS), and TWA presence. Primary endpoints included: VT/VF requiring ICD therapy, death, and VT/VF or death.
Results: Among 484 patients enrolled (mean age 64±10 years), VT/VF occurred in 10%, death in 9%, and VT/VF or death in 19% of patients who were followed for 27±18 months on average. The TRMS<25?V from the SAECG was the strongest predictor of VT/VF with hazard ratio of 2.42 (p<0.01). VT/VF also was predicted by frequent VPBs >500/24hours (HR=1.95; p<0.05).
Abnormal turbulence slope <2.5 RR/ms was independently associated with mortality (hazard ratios of 2.5 = 2.48; p=0.025). Combination of TRMS in SAECG and VPBs in Holter identify patients at high, intermediate and low risk for VT/VF (Figure).
Conclusions: Low QRS voltage on the SAECG is predictor of ventricular arrhythmic events and could help identifying ischemic cardiomyopathy patients benefiting from ICD therapy.