PRESERVED HEART RATE TURBULENCE SLOPE IDENTIFIES LOW-RISK POSTINFARCTION PATIENTS WITH LEFT VENTRICULAR DYSFUNCTION

Background: Implantable cardioverter defibrillator (ICD) therapy has recently been expanded for the prevention of sudden cardiac death based primarily on the results of SCD-HeFT trial. Microvolt T-wave alternans distinguishes low-risk MADIT-II-like patients unlikely to benefit from ICD therapy. We assessed the hypothesis that preserved heart rate turbulence is a potent negative predictor of mortality in postinfarction patients with LVEF<=35%.
Methods: Turbulence slope (TS) was calculated from 24-h Holter recordings in the placebo population of EMIAT trial (LVEF<=35%, n=444). Low-risk patients were defined by indeterminate TS (due to absence of ventricular premature complexes) or by TS>8 ms/RR interval. This dichotomy was determined by maximizing the log-rank statistics for the total mortality. Survival analysis (Kaplan-Meier; proportional hazard Cox regression) was performed for dichotomized population.
Results: Total 73 patients died during follow-up period of 22 months. Deaths were classified as cardiac in 63 patients and arrhythmic in 36 patients. Total 122 (27.5%) patients belonged to low-risk group. Only 4 deaths (2 non-cardiac, 1 cardiac non-arrhythmic, and 1 arrhythmic) were observed in this group. Actuarial mortality (for all modes of death) and corresponding relative risks for low- and high-risk patients are shown in the Table.

	low-risk group (n = 122)	rest of population (n = 322)	relative risk	95% CI	p
all-cause mortality	3.3 %	21.4 %	7.2	2.6 - 19.8	0.0001
cardiac mortality	1.6 %	18.9 %	12.7	3.1 - 52.0	0.0004
arrhythmic mortality	0.8 %	10.9 %	14.5	2.0 - 106.0	0.008

Conclusion: Preserved heart rate turbulence is comparable to microvolt T-wave alternans at identifying low-risk postinfarction patients unlikely to benefit from ICD therapy.