Paroxysmal Supraventricular Tachycardia with QRS Duration Alternans, Electrical Alternans, and Pulsus Alternans but without Cycle Length Alternans.

UNLABELLED: We reported a 60-year-old male patient who had a paroxysmal supraventricular tachycardia with QRS duration alternans (alternation between narrow QRS and wide QRS beats) and electrical alternans, but without any cycle length alternans. In the laboratory, slow-fast atrioventricular nodal reentrant tachycardia was easily induced by an atrial extrastimulus, and the arterial pressure recordings displayed a simultaneous pulsus alternans during tachycardia. The patient also underwent coronary angiography which revealed a total occlusion of the left anterior descending artery. In this report, we have proposed that the QRS duration alternans, electrical alternans and pulsus alternans during the paroxysmal supraventricular tachycardiamay have been due to the prolongation of the effective refractory period of the right bundle branch, caused by myocardial ischemia. KEY WORDS: Electrical alternans; Myocardial ischemia; Supraventricular tachycardia.