Sinus node dysfunction unmasked during dobutamine stress echocardiography.

Sinus bradycardia and associated isorhythmic AV dissociation may be seen during dobutamine stress echocardiography. This phenomenon is usually considered a benign peri-procedural event and is thought to be secondary to the Bezold-Jarisch reflex, with profound heart rate decrease secondary to a marked increased in vagal efferent discharge. To the best of our knowledge, dobutamine stress echocardiography unmasking clinically relevant sinus node dysfunction has never been reported. We report a case of a 50-year-old man presenting with chest pain and a history of syncope, who had worsening sinus bradycardia with isorhythmic AV dissociation during dobutamine stress echocardiography. An invasive electrophysiological study revealed marked sinus node dysfunction. The patient was referred for the insertion of a permanent pacemaker for sinus node dysfunction, chronotropic incompetence and symptomatic bradycardia. Dobutamine-associated bradycardia may not always be a benign peri-procedural physiologic effect, as in this case it may unmask clinically significant sinus node dysfunction.