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Can non-invasive parameters of sympatho-vagal modulation derived from Holter monitoring contribute to risk stratification for primary implantable cardiac-defibrillator implantation?

This editorial refers to ‘Relationship between cardiac autonomic function and sustained ventricular tachyarrhythmias in patients with implantable cardioverter defibrillators’ by I. Battipaglia et al ., Europace 2010;12:1725–31. 

Today, we face two major challenges in risk stratification for primary prevention of sudden cardiac death (SCD) to better select patients who really benefit from implantable cardiac-defibrillators (ICDs). First, among patients with impaired left ventricular ejection fraction (LVEF), the reduction in mortality ranged from 23 to 55%, depending on the risk group, in patients treated with ICD therapy compared with optimal medical therapy; thus about half the patients benefit from primary prevention ICD implant.1–3 Secondly, among patients with prior myocardial infarction (MI) and with preserved LVEF, although the risk of SCD is lower, the total number of SCD is large;4 thus, it is necessary to identify high-risk subgroups among post-MI patients with preserved LVEF, where primary ICD implantation could prevent sudden unexpected deaths.

Current indications for ICD implantation for primary prevention of SCD are based mainly on a haemodynamic parameter, left ventricular dysfunction (LVEF <30–40%) both in post- MI and in non-ischaemic cardiomyopathies.1–3,5–7 Among electrophysiological parameters, only non-sustained ventricular tachycardia (NSVT), defined as three or more consecutive ventricular beats during Holter monitoring and induction of VT on electrophysiological testing, is recognized in current guidelines as predictors of benefit from ICD implant for primary prevention of SCD.1

Consistent evidence have shown that low heart rate variability (HRV) in combination with reduced LVEF contribute to identification of patients at high risk of SCD.8–11 However, according to current guidelines for the prevention of SCD, HRV was useful for risk stratification (Class IIb recommendation), but evidence was not robust enough to include HRV as a predictor in risk stratification for primary ICD implantation. …