Prevention of chronic atrial fibrillation by pacing in the region of Bachmann's bundle: results of a multicenter randomized trial.

INTRODUCTION: Atrial pacing locations that decrease atrial activation and recovery time may be preferable in patients with a history of atrial arrhythmias. This multicenter prospective randomized study compared the efficacy of Bachmann's bundle (BB) region pacing to right atrial appendage (RAA) pacing in patients with recurrent paroxysmal atrial fibrillation (AF). METHODS AND RESULTS: Patients with standard pacing indications (n = 120, 70+/-11 years) were randomized to atrial pacing in either the RAA (n = 57) or BB region (n = 63). Implantation time was similar between groups (88+/-36 min [n = 38] for BB vs 83+/-34 min [n = 34] for RAA). No differences in pacing threshold, impedance, or sensing between BB and RAA groups were observed at implantation or after the 6-week, 6-month, and 1-year follow-up periods. Average length of follow-up was 12.6+/-7.4 months for the BB group and 11.8+/-8.0 months for the RAA pacing group. The percentage of atrial pacing was similar between groups (61%+/-34% RAA vs 65%+/-31% BB at 2 weeks after implant). BB atrial pacing significantly (P < 0.05) shortened p wave duration compared with sinus rhythm (123+/-21 msec vs 132+/-21 msec, n = 50) 2 weeks after implant. In contrast, p wave duration was longer during atrial pacing from the RAA position compared with sinus rhythm (148+/-23 msec vs 123+/-23 msec, n = 37). Additionally, p wave duration was shorter during BB pacing than during RAA pacing. Patients with BB pacing had a higher (P < 0.05) rate of survival free from chronic AF (75%) compared with patients with RAA pacing (47%) at 1 year. CONCLUSION: BB region pacing is safe and effective for attenuating the progression of AF.

Syncope: causes, clinical evaluation, and current therapy.

Syncope is a common clinical problem comprising the sudden loss of both consciousness and postural tone, with a subsequent spontaneous and relatively prompt recovery. Often it is difficult to differentiate a true syncopal spell from other conditions, such as seizure disorders, or from some simple accidents. Even more difficult is the identification of the cause of syncopal episodes. Nonetheless, establishing a definitive diagnosis ia an important task given the high risk of recurrent symptoms. Careful use of noninvasive and invasive cardiovascular studies (including electrophysiologic testing and tilt-table testing) along with selected hematologic, biochemical, and neurologic studies provides, in the majority of cases, the most effective strategy for obtaining a specific diagnosis and for directing therapy.

Cardiorespiratory mobilization and endurance performance.

Twenty subjects performed for 11 min on a bicycle ergometer 30 sec following 5 min of prior exercise (PE) at each of four different intensities. PE was adjusted to maintain a heart rate of 110, 140, and 170 beats/min. The 4th treatment was no PE. Heart rate was an estimate of the mobilization of the cardiorespiratory system during exercise. The criterion task (CT) included cycling for 10 min against 3 kg resistance at 68 rpm followed by 1 min of an all-out work bout where subjects tried to complete as many rpm's as possible against 3 kg. The 11th minute was used to assure the complete exhaustion of energy reserves following the paced part of the task. Overall performance following PE-170 was significantly worse than that following no PE, PE-110, and PE-140, which was probably due to a build up of anaerobic metabolites such as lactate during the PE. Total work appeared to be greatest following PE-110, which showed a slight tendency toward better performance especially after the 6th minute. However, no clear cut evidence was produced to support the hypothesis that light to moderate PE would sufficiently improve performance by mobilizing the cardiorespiratory system, thereby reducing the initial oxygen deficit in the CT and thus allowing more work to be performed.