Effects of Carvedilol on Suppressing the Premature Ventricular Complex/Ventricular Tachycardia From Outflow Tract

Carvedilol is one of the third‐generation beta‐blockers effective in reducing ventricular arrhythmias and mortality in patients with heart failure. Antioxidative and alpha ‐ blocking effects, along with nonselective beta ‐ blockade, have been described as a mechanism of effect in various diseases. The antiarrhythmic effect of carvedilol inhibiting atrial fibrillation or ventricular arrhythmia has been reported, but its mechanism is not yet clear. Among them, inhibition of store overload‐induced Ca2+ release (SOICR) is suggested as an antiarrhythmic mechanism of carvedilol. Stimulation of the beta receptor leads to the entry of calcium into the sarcoplasmic reticulum (SR) by opening the L‐type calcium channel. The influx of calcium through the L‐type calcium channel also increases the calcium release through the Ryanodine receptor (RyR) in the sarcoplasmic reticulum. This is called Ca‐induced Ca release and is known as a normal physiological response. However, when calcium overload in the myofibrillar body occurs, spontaneous calcium release, known as SOICR, can occur through RyR, which can make triggered activity by inducing Na+/Ca2+ exchanger present in myocardium, leading to severe arrhythmia. Among several beta‐blockers, only carvedilol has been known as a drug that can directly inhibit SOICR in combination with beta‐blockade effect. Ventricular tachyarrhythmia originating from the ventricular outflow tract is an arrhythmia occurring in a patient with normal cardiac function. The mechanism of the arrhythmia is known to be triggered activity which is caused by activation of RyR due to increased cyclic adenosine monophasphate, resulting in calcium overload, eventually causing activation of Na+/Ca2+ exchanger. The aim of this study is to evaluate the efficacy of Carvedilol on PVC/VT originating from outflow tract.