Persistent atrial activity during cardioplegic arrest: suppression by verapamil

Postoperative supraventricular tachyarrhythmia may occur more often in patients with persistent atrial activity during hyperkalemic hypothermic cardioplegic arrest. Cannulation of both venae cavae with simultaneous right atrial intra-cavitary cooling reduces atrial activity but is cumbersome. To evaluate pharmacologically-induced atrial arrest using verapamil, bipolar ventricular and right atrial electrograms were recorded in 12 dogs during one hour of hyperkalemic hypothermic cardioplegic arrest and cardiopulmonary bypass using single caval cannula. Group I (n = 6) received hyperkalemic hypothermic cardioplegic solution (4 degrees C) (20 mEq/1 K+) with verapamil (1 mg/L) by intermittent intra-aortic infusion during systemic hypothermia (28 degrees C). Group II (n = 6) received hyperkalemic hypothermic cardioplegia without verapamil. The percentage of time atrial activity was present (greater than 10 beats/min) in Group I, was significantly less than in Group II. Similarly the total number of atrial beats in Group I was less than in Group II. Recovery of normal sinus rhythm during reperfusion was prolonged in Group I in comparison to Group II. Verapamil induces significant and persistent atrial suppression during hyperkalemic hypothermic cardioplegic arrest but prolongs recovery of normal sinus rhythm during reperfusion. It remains to be established clinically whether verapamil-induced atrial suppression is associated with less postoperative supraventricular tachyarrhythmia. The potential disadvantage of prolonged sinus node recovery time must also be assessed.