title: Genesis of high frequency notching of QRS complexes in an in vivo cardiac model.
abstract: High frequency notching of the QRS complex is associated with transmural infarction, cardiomyopathies, and ventricular hypertrophy from any cause. The mechanism producing notching is unknown; but the presence of a discrete anatomic lesion is not an essential feature. The hypothesis that notching was produced by activation across, rather than along, myocardial fibers was investigated by stimulation at 12 points around a clock electrode attached to the epicardium while mapping isoschronous lines in the area activated. All fibers at the subendocardial layer beneath the clock electrode were ligated by a pursestring suture. Propagation direction, as measured by isoschronous maps, produced more notched QRS compleses when the path was across, rather than paralled with, the myocardial fibers. Using grouped data and a 5 times 6 table, notches versus the angle formed between fiber direction and orientation of the direction of travel were shown to be related (P less than 0.001). The hypothesis that cross-fiber activation enhances notching was confirmed. retrograde activation did not increase notching nor did ligation of subendocardial fibers.
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D006332:Cardiomegaly / Q000150:complications; D009202:Cardiomyopathies / Q000150:complications; D004195:Disease Models, Animal; D004285:Dogs; D004558:Electric Stimulation / Q000295:instrumentation; D004562:Electrocardiography; D004566:Electrodes; D006329:Heart Conduction System / Q000503:physiopathology*; D009203:Myocardial Infarction / Q000150:complications