Non-invasive assessment of atrioventricular conduction properties and their effects on ventricular response in atrial fibrillation

This study sought to determine the relation between mean RR intervals as well as its circadian rhythm and non-invasive markers of atrioventricular (AV) node refractoriness and concealed AV conduction obtained from Lorenz-plot (LP) analysis of 10-min and 24-h ECGs. In 29 patients with persistent atrial fibrillation (AF) the 1.0-s intercept of the lower envelope (LE1.0) of the plot and the degree of scatter (S) above the envelope were measured as markers for refractoriness and concealed conduction. Mean 24-h RR was independently associated with LE1.0 and S calculated from 10-min ECGs. In 48% patients, a significant circadian RR rhythm was present, which was independently associated with both S and LE1.0 amplitudes. AV conduction properties obtained from LP analysis of 10-min ECGs are useful for predicting mean 24-h heart rate in AF. The degree of variation in refractoriness and concealed conduction are determinants of significant circadian heart rate variation in AF.