-Cardiac intramural electrical mapping reveals focal delays but no conduction velocity slowing in the peri-infarct region.

This study characterises, for the first time, the intramural spread of electrical activation in the peri-infarct region of chronic reperfusion MIs. Four sheep were studied 13 weeks after antero-apical reperfusion infarction. Extracellular potentials (ECPs) were recorded in a ~20×20 mm2 region adjacent to the infarct boundary (25 plunge needles <0.5mm diameter with 15 electrodes at 1mm centers) during multi-site stimulation. Infarct geometry and electrode locations were reconstructed from MR images. 3D activation spread was characterized by local activation times and interpolated ECP fields (N=191 records). Control data were acquired in four non-infarcted sheep (N=96 records). Electrodes were distributed uniformly around 15±5% of the intramural infarct boundary. There were marked changes in pacing success and ECP morphology across a functional border zone (BZ) ±2mm from the boundary. Stimulation adjacent to the infarct boundary was associated with low-amplitude electrical activity within the BZ and delayed activation of surrounding myocardium. Bulk tissue depolarization occurred 3.5-14.6 mm from the pacing site for 39% of stimuli with delays of 4-37 ms, both significantly greater than control (p<0.0001). Conduction velocity (CV) adjacent to the infarct was not reduced compared to control, consistent with structure-only computer model results. Insignificant CV slowing, irregular stimulus-site specific activation delays and obvious indirect activation pathways strongly ...
Source: American Journal of Physiology. Heart and Circulatory Physiology - Category: Physiology Authors: Tags: Am J Physiol Heart Circ Physiol Source Type: research