Learned control of ventricular rate in patients with atrial fibrillation

Six patients with chronic atrial fibrillation (AF) and rheumatic heart disease on stable digitalis regimens were trained to slow and to speed ventricular rate (VR). Two subjects were more consistent in their ability to slow VR; two subjects were more consistent in their ability to speed VR; and the remaining two subjects were able to slow and to speed VR reliably. All subjects were able to control VR differentially during sequential slowing and speeding phases of experimental training sessions. Analyses of R R interval histograms revealed that all subjects significantly changed the statistical frequency distributions of their R R intervals. During VR slowing one subject generated a junctional escape rhythm. Another subject produced frequent premature ventricular contractions during speeding of VR under effective β adrenergic blockade with propranolol. This control of VR in AF is neurally mediated at the level of the atrioventricular node. Studies with autonomic drugs indicate that this central nervous system control of VR in this arrhythmia usually occurs through activation of efferent cholinergic pathways.