RecruitingPhase 4Drug trialUse of Adenosine to Determine the Electrophysiological Mechanism of Premature Ventricular ContractionsUnblinded, controlled, non-randomized, mechanistic study to determine whether physiological mechanisms underlying PVC are sensitive to adenosine. One hundred subjects undergoing clinically-indicated, standard-of-care cardiac electrophysiology study (EPS) procedure for PVCs will receive adenosine and/or verapamil to learn if their arrhythmias are inducible similarly to sustained ventricular tachycardia.