Electrophysiological properties of the recipient atrial remnant after human orthotopic cardiac transplantation

Aims The recipient atrial remnant has been used as a control in studies of chronotropic response following orthotopic cardiac transplantation and as a trigger for the donor heart. It is not known, however, whether its function is normal. We investigated the electrophysiological properties of the recipient atrial remnant. Methods and Results Fifty patients were studied, mean age 49 years (range 20-63) and mean time post-orthotopic cardiac transplantation of 31 months (range 1-107). Recipient atrial rhythm, spontaneous cycle length and sinus node function were determined. Atrial fibrillation/flutter was identified in 10/50 (20%). Of those in sinus rhythm, significant bradycardia was present in 12/40 (30%). The mean spontaneous cycle length was 929 +/- 188 ms. Three patients demonstrated variable atrial electrocardiogram morphology and a further three patients had marked variations in resting cycle length. The sinus node function was abnormal in 2/34 (6%). Conclusions Only 56% recipient atria had normal sinus rhythm, with 21% of these demonstrating features consistent with a wandering atrial pacemaker. The recipient atrial remnant is not normal in the majority of transplant recipients and should be used with caution in studies involving its use as a control or as a trigger for the donor heart.