First results of the Canadian and European single lead DDD studies. A report of two multicenter studies on Vena Cava Atrial Stimulation (VECATS)

The first results of a new single lead DDD pacing system consisting of two bipolar combinations of floating atrial ring electrodes, with the proximal ring at the vena cava superior junction, and which can be used separately f or atrial sensing and pacing (VECATS) are reported. Uncomplicated implantat ion of the pacing system was performed in 78 patients with VDD indications. Pacing and sensing parameters were measured at implantation, before discha rge (days 1-3), at 1 and 3 months in various positions and during activity. Atrial pacing threshold (AT) and diaphragmatic stimulation threshold (DT) were 3.3 +/- 1.1 V and 7.2 +/- 2.2 at implant, and 4.3 +/- 0.5 and 7.9 +/- 1.1 V elf 3 months, respectively, in the European group. In the Canadian gr oup AT increased and DT decreased during follow-up, leaving a safety margin of 1 V. Reliable intraoperative atrial pacing was possible in 93% of patie nts. Failures were caused by no capture (3%) or AT > DT (4%). At 3 months, 54% of the atria were consistently paced. Atrial pacing failures were due t o no atrial capture (8%), and AT > DT (38%). We conclude that atrial pacing was safe and initially possible in the majority of patients with the VECAT S pacing system, though diaphragmatic stimulation became more prevalent or er time, due to an increase in AT threshold and a decrease in DT.