A new implantation technique in the upper lateral part of the right atrium has reduced the complication rate of atrial electrodes to less than 4% at 11 months' follow-up. P-wave amplitude and acute and chronic threshold are in the order of conventional ventricular electrodes. In 10 of 56 patients with atrial-triggered ventricular pacemakers the cardiac output at rest and during exercise was found to be respectively 8% and 17% higher than with fixed-rate ventricular pacing. This hemodynamic benefit is longlasting, in contrast to findings with non-atrial synchronized pacing.