Fibrillation Threshold of Premature Ventricular Responses

The degree of temporal dispersion of recovery of excitability of premature ventricular responses, estimated as the range of local refractory periods at various points on the surface of the right ventricle, is greater within a radius of 10 to 15 mm from the stimulated site than at greater distances. The fibrillation threshold of early premature beats is significantly lower than that of responses initiated in fully excitable tissue. The effect of prematurity on the fibrillation threshold is greater at points near the site of origin of the premature response. The observed spatial and temporal relationships suggest that the fibrillation threshold is related inversely to the degree of asymmetry in the excitable field.