Evaluation of right atrial and biatrial temporary pacing for the prevention of atrial fibrillation after coronary artery bypass surgery.

OBJECTIVES: The purpose of this study was to determine if atrial pacing is effective in reducing postoperative atrial fibrillation (AF). BACKGROUND: Atrial fibrillation after coronary artery bypass grafting (CABG) is a common problem for which medical management has been disappointing. Atrial-based pacing has become an attractive nonpharmacologic therapy for the prevention of AF. METHODS: Sixty-one post-CABG patients (mean age = 65 years) were randomized to one of three groups: no atrial pacing (NAP), right atrial pacing (RAP) or biatrial pacing (BAP). Each patient had one set of atrial wires attached to both the right and left atria, respectively, at the conclusion of surgery. Patients in the RAP and BAP groups were continuously paced at a rate of 100 pulses per minute for 96 h or until the onset of sustained AF (>10 min). All patients were monitored with Holter monitors or full disclosure telemetry to identify the onset of AF. The primary end point of the study was the first onset of sustained AF. RESULTS: There was no significant difference in the proportion of patients developing AF in the three groups (NAP = 33%; RAP = 29%; BAP = 37%; p > 0.7). However, for the subset of patients on beta-adrenergic blocking agents after CABG, there was a trend toward less AF in the paced groups. There were no serious complications related to pacing, although in three patients the pacemaker appeared to induce AF by pacing during atrial repolarization. CONCLUSIONS: Continuous right or biatrial pacing in the postoperative setting is safe and well tolerated. We did not find that post-CABG pacing prevented AF in this pilot study; however, the role of combined pacing and beta-blockade merits further study.

Automated VO2max calibrator for open-circuit indirect calorimetry systems.

The complete calibration of indirect calorimetry systems involves simultaneous checks of gas analyzers, volume device, and software, and this requires a machine that can mimic accurately and precisely the ventilation and expired gases of an athlete. While previous calibrators have been built successfully, none have matched the ventilatory flows produced by athletes during high intensity exercise. A calibrator able to simulate high aerobic power (VO2max calibrator) was fabricated and tested against conventional indirect calorimetry systems that use chain-compensated gasometers to measure expired volume (VE systems) and calibrated electronic gas analyzers. The calibrator was also checked against a system that measures inspired volume (VI system) with a turbine ventilometer. The pooled data from both VE and VI systems for predicted VO2 ranging from 2.9 to 7.9 L.min-1 and ventilation ranging from 89 to 246 L.min-1 how that the absolute accuracy (bias) of values measured by conventional indirect calorimetry systems compared with those predicted by the calibrator was excellent. The bias was < 35 mL.min-1 for VO2 and carbon dioxide production, < 0.50 L.min-1 for ventilator (VE BTPS), -0.02% absolute for the percentage of expired O2 and +0.02% absolute for the percentage of expired CO2. Overall, the precision of the measured VO2, VCO2, and VE BTPS was approximately 1%. This VO2max calibrator is a versatile device that can be used for routine calibration of most indirect calorimetry systems that assess the ventilation and aerobic power of athletes.

Cross-species transplantation: NK cell number and function are normal in fully xenogeneic chimeras (rat----mouse).

When untreated F344 rat bone marrow is transplanted into B10 mouse recipients conditioned with total body irradiation, stable fully xenogeneic chimerism (rat----mouse) results. Chimeras are specifically tolerant to the donor strain of rat, survival is excellent (greater than 80% at 8 months), and all stem-cell-derived lineages are produced by the rat stem cell. We have previously demonstrated normal function of T-lymphocytes in these chimeras, but have not examined the immune function of natural killer (NK) cells present. Because NK cells play a critical role in immune surveillance, absence of function could result in a serious immunodeficiency state. We present data here to suggest that rat NK cells that have developed in a mouse stromal environment are normal in function as well as number. In all fully xenogeneic chimeras tested from 8 weeks to 8 months following bone marrow transplantation, NK cells were present at a normal level (10% to 16%). NK cells function in these chimeras, as tested by spontaneous lysis of YAC tumor cell targets, was normal or superior to normal F344 rat and B10 mouse NK cells.

Electromyographic biofeedback for tension control during fine motor skill acquisition.

The presence of residual muscular tension has been implicated as a deterimental influence on the performance and learning of motor skills. A method for reducing muscular tension has been provided by the the advent of biofeedback training. This study investigated the effects of tension-control training by electromyographic (EMG) biofeedback on learning and performance of the pursuit-rotor backing task. Thirty young adult males were pretested for pursuit-rotor (PR) tracking skill, ranked by performance scores, and divided into identical triplicates to form two experimental groups and a control group. After a total of 3 hours of EMG biofeedback training for the experimental groups, all subjects were reevaluated on the PR test. One experimental group received biofeedback during the posttests. Analysis of variance of pretest-posttest difference means and t tests of scores representing performance and tension indicated that the EMG biofeedback training (1) significantly reduced tension induced by the novel motor skill and (2) significantly improved performance of the motor skill. Transfer of tension-control training was shown to facilitate learning and performance more than direct EMG biofeedback during performance. Residual tension reduction during learning was particularly facilitated by EMG biofeedback training, a profound implication for the management of stress in a variety of situations.

Electromyographic biofeedback for tension control during gross motor skill acquisition.

This study investigated the effects of tension-control training by electromyographic biofeedback on learning and performance of a stabliometer balancing task. 30 young adult males were pretested for stabilometer balancing skill, ranked by performance scores, and divided into identical triplicates to form two experimental groups and a control group. All subjects were reevaluated on the stabilometer test following feedback training of the experimental subjects. Analysis of variance of difference means, scores representing performance and tension, indicated that the biofeedback training significantly reduced tension induced by the novel motor skill and significantly improved performance of the motor skill.