This case report is kindly provided by Michael Rosengarten from McGill and is part of the McGill Cases. These cases come from the McGill EKG World Encyclopedia.
The recording is interesting as the patient goes from sinus rhythm to at first a wide complex tachycardia at about 130/min. The wide QRS though disappears after nine complexes and is replaced by narrow complexes at a slightly slower rate. No p wave activity is seen. This a supraventricular tachycardia with a from of abberancy. In this case we are probably seeing a rate dependent left bundle branch block or the effect of a left bundle branch block which persists for the nine complexes because of continued block in the left bundle from the depolarizations from the intact right bundle.
