Background Slow, nonuniform conduction caused by abnormal gap-junctional coupling of infarct-related myocardium is thought to be a component of the arrhythmogenic substrate. The hypothesis that changes in gap-junctional distribution in the epicardial border zone (EBZ) of healing canine infarcts define the locations of reentrant ventricular tachycardia (VT) circuits was tested by correlating activation maps of the surviving subepicardial myocardial layer with immunolocalization of the principal gap-junctional protein, connexin43 (Cx43).

Methods and Results The EBZ overlying 4-day-old anterior infarcts in three dogs with inducible VT and three noninducible dogs was mapped with a high-resolution electrode array and systematically examined by standard histology and confocal immunolocalization of Cx43. The thickness of the EBZ was significantly less in the hearts with (538±257 μm) than without (840±132 μm; P<.05) VT. At the interface with the underlying necrotic cells, the EBZ myocardium showed a marked disruption of gap-junctional distribution, with Cx43 labeling abnormally arrayed longitudinally along the lateral surfaces of the cells. In the EBZ of all hearts, the disrupted Cx43 labeling extended part of the way to the epicardial surface, with the most superficial epicardial myocytes having the normal transversely orientated pattern. Only in the hearts with inducible VT did the disorganization extend through the full thickness of the surviving layer at sites correlating with the location of the central common pathways of the figure-of-8 reentrant VT circuits.

Conclusions Altered gap-junctional distribution is part of the early remodeling of myocardium after infarction, and by defining the location of the common central pathway of the reentrant VT circuits, it may be a determinant of VT susceptibility.