Heart Rate Turbulence Slope Reduction in Imminent Ventricular Tachyarrhythmia and its Implications

Introduction: The aim of this study was to see whether heart rate turbulence (HRT) parameters change preceding imminent ventricular tachyarrhythmias (VT/VF). Methods and Results: The Spontaneous Ventricular Tachyarrhythmia Database (Medtronic Version 1.0) consisting of 83 paired (control and pre‐VT/VF) sets of 1,000 RR intervals recorded by the Medtronic Jewel Plus ICD was used. Sixty‐one control records and 69 pre‐VT/VF records had two or more ectopic beats, allowing calculation of six HRT indices: means and standard deviations (SD) of turbulence slope (TS), turbulence onset (TO), and turbulence timing (TT). The only index found to be different between control and pre‐VT/VF records was SD of TS (4.2 ± 3.0 control vs 3.1 ± 1.9 pre‐VT/VF, P < 0.05). Thirty‐one datasets classified as having normal HRT in control demonstrated a decrease of both TS mean (P < 0.01) and SD (P < 0.01), and loss of correlation between TS mean and left ventricular ejection fraction (LVEF) preceding VT/VF (P < 0.0001 control, P = 0.8 pre‐VT/VF). Conclusion: Both mean and SD of TS are reduced before VT/VF, but only in patients who have normal baseline HRT, and are capable of manifesting reduction. This may be why previous studies could not agree on pre‐arrhythmia characteristics.