Lower-Shumway technique (atrioatrial anastomosis) is the most frequently used technique for orthotopic heart transplantation and such a patient has two right atria and two sinus nodes. Sinus node dysfunction (SND) is a frequent finding in pts. after OHT; taking advantage of the frequency of innervated sinus node of recipient's atrial remnant as a natural biosensor for triggered pacing of donor atrium is an interesting option for these pts. THE AIMS OF OUR STUDY: 1. the analysis of possibility of utility of recipient atrial sinus node as natural biosensor for triggered donor atrium permanent pacing in transplanted patients with SND. 2. the evaluation of pacing and sensing conditions of the recipient's atrium in the some pts.. 3. long-term observation of effectiveness A2A2T(/D) pacing mode. METHODS: 10 out of 37 pts. received A2A2T (8 pts.) and A2A2T/D (2 pts) pacing systems. In pts. with NSR of recipients atrium, we evaluated acceleration of its frequency during slight exercise and atropine. RESULTS: In recipient's atrium among 37 pts we recognized NSR only in 15/37 pts.; in the remaining 22 pts. we found: sinus bradycardia--in 3, atrial flutter--in 3, low voltage AF--in 12 and no electrical activity--in 4 pts. Positive response to isometric exercise and atropine was observed in 12/15 pts. and 8 of them received A2A2T or A2A2T/D pacing system. We found much better sensing and pacing conditions in donor (A wave 2.1 mV, p. threshold 0.8 V) than in recipient atrium (1.1 mV and 1.4 V respectively). We observed some problems with sensing of recipient atrium in 4 of 10 pts. and changes SST to AAI-R mode solved the problem without loss of atrial resynchronization. 9 out of 10 pts. preferred AAT to AAI-R pacing program. One dislodged lead required revision during postoperative period (1/44, 2%). There was no dislodgement related to endomyocardial biopsy. In one patient, atrial flutter in recipient atria was transmitted to atrium of transplanted heart by pacing system with 2:1 conduction; arrhythmia was interrupted with drugs and did not return. CONCLUSIONS: 1. Atrial resynchronization is possible only in about 1/4 patients with SND after OHT due to frequently noted electrophysiological changes in recipient atrium. 2. In transplanted heart patients sensing and pacing conditions are much more favorable in donor's than recipient's atrium. 3. Atrial resynchronization can be subjectively (positively) recognised by most of patient after OHT and it still remains a promising pacing mode for selected patients after OHT with SND.

Keywords: Arrhythmias, Cardiac - surgery, Arrhythmias, Cardiac - therapy, Atrioventricular Node - surgery, Cardiac Pacing, Artificial, Electric Countershock, Electrocardiography, Heart, Heart Rate - physiology, Heart Transplantation - adverse effects, Heart Transplantation - physiology