Abstract
BackgroundThe autonomic imbalance during acute ischemia is involved in the occurrence of life-threatening arrhythmias.ObjectiveTo investigate the effect of autonomic nervous system (ANS) modulation by low-level carotid baroreceptor stimulation (LL-CBS) on ventricular ischemia arrhythmias.MethodsAnesthetized dogs were received either sham treatment (SHAM group, n = 10) or LL-CBS treatment (LL-CBS group, n = 10). The voltage lowering the blood pressure was used as the threshold for setting LL-CBS at 80% below the threshold. Treatment started 1 hour before left anterior descending coronary (LAD) occlusion, and continued until the end of experience. Ventricular effective refractory periods (ERP), monophasic action potential duration at 90% (APD90), ventricular arrhythmias, indices of heart rate variability, left stellate ganglion nerve activity (LSGNA) and infarct sizes were measured and analyzed.ResultsVentricular ischemia resulted in an acute reduction of blood pressure, which was not significantly affected by LL-CBS. After 1 hour of LL-CBS, there was a progressive and significant increase in ERP, increase in APD90, and decrease in LSGNA vs the SHAM group (all P<0.05). LL-CBS apparently reduced premature ventricular contractions (PVC, 264±165 in the SHAM group vs 60±37 in the LL-CBS group; P<0.01) during LAD occlusion. Number of episodes of ventricular fibrillation (VF) was 8 in the Control group versus 3 in the LL-CBS group (80% versus 30%, P<0.05). LL-CBS obviously increased high frequency (HF) component (P<0.05) and decreased low frequency/high frequency ratio (P<0.05) compared with the SHAM group. Ischemic size was not affected by LL-CBS between the two groups.ConclusionsLL-CBS reduced the occurrences of ventricular arrhythmias during acute ischemia without affecting blood pressure. The procedure was associated with changes of electrophysiological characteristics, nerve activity and heart rate variability. Therefore, LL-CBS may protect from ventricular arrhythmias during acute ischemic events by modulating ANS.
Highlights
The autonomic imbalance, i.e. the activation of sympathetic nervous system and the reduction of parasympathetic activity, constitutes a fundamental element of acute myocardial ischemic pathophysiology [1]
level carotid baroreceptor stimulation (LL-Carotid baroreceptor stimulation (CBS)) reduced the occurrences of ventricular arrhythmias during acute ischemia without affecting blood pressure
LL-CBS may protect from ventricular arrhythmias during acute ischemic events by modulating autonomic nervous system (ANS)
Summary
The autonomic imbalance, i.e. the activation of sympathetic nervous system and the reduction of parasympathetic activity, constitutes a fundamental element of acute myocardial ischemic pathophysiology [1]. It is associated with progressive ventricular remodeling, disease progression and arrhythmia generation. Carotid baroreceptor stimulation (CBS) can reset autonomic tone, and were used as a promising therapeutic approach to treat refractory hypertension and heart failure [5,6]. We confirmed that CBS may have a beneficial impact on ventricular arrhythmias induced by acute ischemia through modulation of autonomic tone in dogs [8]. The autonomic imbalance during acute ischemia is involved in the occurrence of life-threatening arrhythmias
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