Abstract 2123: ECG Markers to Predict Cardiovascular Death: Heart Rate Variability, Deceleration Capacity and Morphologic Variability in Non-ST-Elevation ACS from the MERLIN-TIMI 36 Trial

Abstract

Background : ECG parameters such as heart rate variability (HRV), deceleration capacity (DC) and morphologic variability (MV) may help identify patients at high risk post-ACS. These techniques measure specific aspects of cardiac health. HRV studies sympathovagal modulation of heart rate, DC extends heart rate turbulence by measuring acceleration-deceleration patterns, and MV quantifies variability in the shape of the ECG signal associated with myocardial instability. We assessed the relationship among HRV, DC and MV, and cardiovascular (CV) death after NSTEACS. Methods : HRV, DC and MV were calculated in 2164 placebo patients in the MERLIN-TIMI 36 trial using 24 hour Holter ECG after randomization. For each measure, patients were split into high and low risk groups (cutpoints chosen from literature: HRV LF/HF=1.2 [33.5%], DC<2.5 ms [9.7%], MV LF/HF=3.7 [11.6%]). Mean clinical follow-up was 1 year. Results : Each ECG variable was associated with CV mortality when included alone in the multivariate model with the TIMI risk score (TRS) at 30 days (HR 2.8 p=0.008 for HRV, HR 4.5 p<0.001 for DC and HR 5.1 p<0.001 for MV) and at 1 year (HR 2.9 p<0.001 for HRV, HR 2.8 p<0.001 for DC and HR 2.4 p<0.001 for MV). There was a stepwise increase in the risk of CV death at 1 year according to the number of abnormal ECG parameters, even after adjusting for the TRS. Conclusions : HRV, DC and MV are significantly associated with CV death both in the short and medium term following NSTEACS. Patients with multiple ECG abnormalities are at highest risk. These ECG parameters may provide complementary information to better risk-stratify patients following ACS.