Autonomic modulation of ventricular arrhythmia in cesium chloride-induced long QT syndrome

Abstract

To evaluate autonomic influence on arrhythmogenesis in an animal preparation of triggered activity, we gave increasing doses of cesium chloride (0.125 to 5.0 mmol/kg iv) to 24 dogs distributed equally among four protocols of autonomic intervention: control, total denervation, β-blockade, and left stellate stimulation. All dogs underwent atrioventricular node ablation follwed by ventricular pacing. A left ventricular endocardial monophasic action potential (MAP) catheter allowed for detection of 'MAP early afterdepolarizations' (mEAD). mEAD amplitude was measured relative to MAP amplitude. Cesium chloride (CsCl) increased both MAP duration (132% after 0.125 mmol/kg to 188% after 1.0 mmol/kg; p < .001) and with earlier onset (12 vs 30 sec; p < .001), whereas β-blockade had little effect (39% vs 38%; p = NS). Autonomic intervention as such can affect the arrhythmogenicity of CsCl and similarly alter MAP characteristics. Furthermore, as β-blockade can prevent sustained arrhythmia without eliminating mEADs, autonomic tone appears to modulate the expression of mEADs as sustained VT.