title: Concealed Sinus Node Dysfunction and Paradoxical Effect of Atropine during Arrhythmia Diagnostic Pharmacological Testing.
abstract: A 78-year-old male patient presented with repetitive fainting episodes. His electrocardiogram showed sinus rhythm with persistent ventricular bigeminy. Concealed sinus node dysfunction (SND) with consecutive bradycardia-induced ventricular hyperexcitability was suspected. Pharmacological testing with atropine resulted in accelerated junctional rhythm along with nearly total disappearance of the ventricular ectopy. The diagnosis of SND was retained, a dual chamber pacemaker was implanted, and consequently, ventricular hyperexcitability disappeared. The junctional rhythm was a paradoxical effect of atropine, and many explanations were provided. Discussion was made accordingly taking into account relevant data from the literature.
authors.affiliation: Anesthesia and Critical care Department, University Hospital Notre Dame de Secours, St Charbel street, Byblos, Lebanon.
authors.forename: Myriam
authors.initials: M
authors.lastname: Karam
authors.affiliation: Electrophysiology Unit, Cardiology Department, University Hospital Notre Dame de Secours, St Charbel Street, Byblos, Lebanon.
authors.forename: Antoine
authors.initials: A
authors.lastname: Kossaify
keywords: atropine; concealed; paradoxical; sinus node dysfunction; ventricular ectopy