ENHANCED DISPERSION OF EPICARDIAL ACTIVATION-RECOVERY INTERVALS AT SITES OF HISTOLOGICAL INHOMOGENEITY DURING REGIONAL CARDIAC ISCHEMIA ANDREPERFUSION

Objective-To examine how epicardial activation and repolarisation patt erns change in the course of ischaemia, and how these changes are rela ted to the underlying histological structures. Methods-Langendorff per fused isolated rabbit hearts were submitted to 30 minutes of left ante rior descending coronary artery occlusion followed by 30 minutes of re perfusion. A 256 channel epicardial map was plotted during the various experimental phases. Activation time points were determined as t(dU/d t(min)) and repolarisation time points as t(dU/dt(max)). From these da ta the local activation-recovery interval (ARI), its dispersion (SD of ARI), and the geometry of the activation spread could be analysed. Af ter the experiments the hearts were processed histologically and the m apping data were projected onto histological slides. Results-There was elevation of the ST segment within the occluded area, which recovered during reperfusion. Within this area, ARI:was significantly shortened and its dispersion was maximally enhanced. The enhancement of dispers ion was pronounced at sites of histological inhomogeneity like fat, co nnective tissue, or vessels. There was also a change in the preferenti al direction of activation spread within the occluded zone with a mark ed transverse propagation of the activation wavefront, whereas under n ormal conditions the activation followed the longitudinal fibre axis. In addition, the total activation time in the occluded area was signif icantly prolonged. Conclusions-Ischaemia alters the local activation p attern with enhanced dispersion, especially at sites of histological i rregularity, transverse shift of the activation waves, and a general s lowing of conduction, which may explain the increased susceptibility t o arrhythmia in hearts with enhanced histological irregularities-for e xample, an infarct or in multi-infarcted hearts, or after myocarditis.