Heart rate variability patterns before ventricular tachycardia onset in patients with an implantable cardioverter defibrillator☆
Section snippets
Patient population
From September 1, 1997, to December 1, 1998, the stored electrographic time series before detected arrhythmic events of 60 patients implanted with Medtronic 7220 to 7223 devices (Minneapolis, Minnesota) were collected. This procedure was performed at the time of device interrogation after an arrhythmic event perceived by the patient, during a scheduled control examination or after the patient’s admission to the emergency room (35%, 50%, and 15% of the cases, respectively). A control recording
Arrhythmic events
Sixty-eight episodes of VT were analyzed. Most of the episodes (77%) occurred during daytime while the patients were not engaged in physical activity; a few episodes (7%) occurred during some form of exercise, whereas the remaining events occurred during the night. The mean cycle length of VT was 322 ± 6 ms. Antitachycardia pacing effectively treated most of the episodes (71%). Cardioversion terminated VT in 29% of cases.
Analysis of short-term recordings
The period immediately before VT onset was compared with control and VT20.
Discussion
Our study describes for the first time the changes in HRV before VT in patients with an implantable defibrillator. Three major findings are notable and distinguish the minutes before VT onset from control periods: a reduction in cycle length duration and in total power, an increase in LF/HF ratio, and a more negative scaling exponent β.
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This study was partially supported by a grant from Ministero dell’Università e della Ricerca Scientifica, Rome, Italy. Manuscript received March 9, 2000; revised manuscript received and accepted May 5, 2000.
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The participating centers are listed in the .