Dynamic coupling between ventricular repolarization duration and RR-interval phase-rectification analysis in Chagas disease

Dynamic ventricular repolarization duration (VRD) and phase-rectification-driven RR-interval coupling was investigated aiming at assessing myocardial electrical stability in healthy and chronic Chagas disease (ChD) subjects. All 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 500 ms to 1200 ms. For each class, mean of normal RR-intervals (MRR) and mean of the peak-to-peakR-to-T wave interval (MRT), representing VRD, 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 MRT vs. MRR were computed in the whole series, and in DC and AC phases, and respective slopes calculated (sMRT
T
, sMRT
DC
and sMRT
AC
). Student t-test compared groups. RT-interval was larger in ChD group. sMRT
T
, sMRT
DC
and sMRT
AC
function showed no difference between groups, and all increased directly to MRR. In both groups, MRT increased as a linear function of MRR. In ChD, RT-interval analysis was not able to confirm loss of sympathetic driven RR-interval variation.