Electrical current paths in acute pericarditis

The electrocardiographic changes accompanying pericarditis consist of ST elevation in most of the leads of the 12-lead electrocardiogram. The source of this ST elevation is thought to be local inflammatory changes in the epicardium underlying the inflamed pericardium. The current from this area of ST elevation must return to some unaffected region of the heart and this should be associated with a region of ST depression. This current path from the external epicardial surface has been postulated to flow back into the endocardium through the great vessels and atria. To test this hypothesis, 18 patients with pericarditis were studied by body surface potential mapping and inverse epicardial potential distributions were computed. The resultant maps were compared to those of normal people and patients with acute anterior infraction. Epicardial maps from patients with pericarditis showed a region of current flow into the heart over the great vessels and atria in all 18 patients. This pattern was not seen in normal patients or infarction patients and was consistent with the mechanism resulting in ST elevation in pericarditis being one of current flowing from the epicardium out into the thorax and back into the heart through the great vessels and atria.