Abstract 18541: Morning Surge of Ventricular Arrhythmias in a New Arrhythmogenic Canine Model of Heart Failure is Associated With Attenuation of Heart Rate and Autonomic Adaptation but Reduced Cardiac Chaos
Introduction: Ventricular arrhythmias in heart failure (HF) can be modulated by autonomic stimulation that is reflected by heart rate variability (HRV). Noninvasive measures of nonlinear dynamics (NLD) assess cardiac chaos, decrease of which can be detrimental in patients with HF. Holter monitoring of HF patients (to assess HRV & NLD) is limited by concurrent medication use. The aim of this study was to assess arrhythmia development, heart rate (HR) dynamics and nonlinear dynamics in a new arrhythmogenic canine model of HF.
Methods: HF was induced in dogs (N=25) by aortic insufficiency & aortic constriction and assessed by echocardiography. Holter monitoring was performed to study time-of-day variation in arrhythmias (PVCs, VT), traditional HRV measures, and nonlinear dynamics (including Shannon entropy (SE), detrended fluctuations analysis α1 and α2 (DFAα1 & DFAα2), and correlation dimension (CD)) at baseline, 240 days (240d) and 720 days (720d) after HF induction.
Results: LV fractional shortening decreased from 43.4±0.7 vs 27.5±0.8 % (p<0.01). Both PVCs and VT showed an early morning rise (2.1-fold & 1.9-fold increase at 6AM-noon vs midnight-6AM). An early morning rise in HR at baseline (ΔHR=13.53±1.42 bpm) was attenuated with development of HF (ΔHR=7.06±0.26 and 6.69±2.44 bpm at 240d & 720d; p<0.01, p<0.05), and was shifted to later in the day. Likewise early morning rise in the ratio of low frequency to high frequency (LF/HF, reflecting the ratio of sympathetic to parasympathetic inflow) at baseline was markedly attenuated with HF (p<0.05 at 240d & 720d), suggesting reduced early morning sympathetic adaptation. For nonlinear dynamics, SE, DFAα1, DFAα2, and CD all decreased with HF (3.04±0.02 vs 2.82±0.07, 0.67±0.03 to 0.46±0.03, 0.69±0.02 to 0.56±0.03, all p<0.01; and 1.88±0.13 vs 1.12±0.25, p<0.05 for baseline vs 720d), indicating decreased cardiac chaos in HF dogs.
Conclusions: In this new arrhythmogenic canine model of HF, an early morning surge in ventricular arrhythmias was associated with attenuation of morning HR rise and blunting of autonomic oscillation. Measures of nonlinear dynamics reflected a consistent decrease in cardiac chaos and loss of complexity of heart rate that could be contributing to ventricular arrhythmias in this setting.
- © 2013 by American Heart Association, Inc.