Dynamic coupling between atrio-ventricular duration and RR-interval histogram phase-rectification analysis in chronic Chagas disease

This study investigated dynamic atrio-ventricular duration (AVD) and phase-rectification-driven RRinterval coupling to assess AV conduction facilitation in healthy and chronic Chagas disease (ChD) subjects. All subjects were in sinus rhythm and underwent 60 min head-up tilt table test under ECG recording. ChD group underwent MIBG scintigraphy and confirmed sympathetic denervation. Histogram of RR-interval series was calculated, with 100 ms class, ranging from 600 ms to 1200 ms. For each class, mean of normal RR-intervals (MRR) and mean of the peak-to-peak P-to-R wave interval (MPR), representing AVD, were analyzed in RR-intervals pairs of acceleration (AC) and deceleration (DC) phases, reflecting sympathetic and parasympathetic influences on heart rate, respectively. Regression lines of MPR vs. MRR were computed in the whole series, and in DC and AC phases, and respective slopes calculated (sMPRT, sMPRDC and sMPRAC). Student t-test compared groups. MRR and MPR were larger in ChD group. In healthy subjects, sMPRT, sMPRDC and sMPRAC significantly increased as a function of MRR in all phases. In subjects with Chagas disease, however, PR-interval increases only in DC phase, confirming loss of sympathetic driven RR-interval variation.