Artikel
Symbolic dynamics for the prediction of ventricular tachyarrhythmias
Symbolische Dynamik für die Vorhersage Ventrikulärer Tachyarrhythmien
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Veröffentlicht: | 10. August 2005 |
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Implantable cardioverter-defibrillators (ICDs) are the standard therapy in patients with ventricular tachyarrhythmia (VTA) and provide a unique opportunity to analyse beat-to-beat (RR)-interval variability (HRV) before the onset of such life-threatening event. In a pilot study, published in 2000, we found that the symbolic dynamics parameter POLVAR10 was able to differentiate significantly between HRV time series before a VTA and at a control time. Therefore, the MARITA study was conducted to validate these results prospectively. In 186 patients (153 men, mean age 61.0±10.4) with an implanted ICD (Biotronik ICDs, 9000 RR-intervals capacity) 257 heart rate recordings before a VTA (from 94 patients) and 645 series during control conditions (recordings at follow-up date without VTA) were recorded. From these time series 107 VTA and 422 control recordings were in sinus rhythm, being longer than one hour and having less 10 % ectopy. For HRV analysis standard time- and frequency parameters as well as nonlinear dynamical measures were calculated. The mean RR-interval in the VTA group was significantly decreased than in controls (752.4±13.9 vs. 819.1±8.1, p<0.0001), whereas the number of ventricular premature beats (VPBs) was increased (230.5±19.7 vs. 147.7±10.5, p<0.00001). To determine the time of sympathetic activation we calculated all HRV parameter for successive 5 minutes intervals up to 90 minutes before the onset of VTA. Heart rate and ventricular ectopy rate are significantly increased already 90 minutes before VTA, suggesting a state of sympathetic excitation. The symbolic dynamics parameter POLVAR10 was the only parameter which could detect precursors of VTA. Our result suggests that the myocardium becomes susceptible to VTA by a more complex mechanism dependent on variable neurohumoral regulatory systems, rather than solely by sympathetic activation.