Recent experimental studies showed a protective effect of the
renin inhibitor aliskiren regarding atrial structural remodeling. Purpose of this study was to assess acute electrophysiologic effects of
aliskiren in a whole-heart model of
atrial fibrillation (AF) and to investigate its impact on the ventricle. Twelve rabbit hearts were excised, retrogradely perfused, and paced at different cycle lengths. To enhance atrial vulnerability, a combination of
acetylcholine (ACh) and
isoproterenol (Iso) was infused and significantly reduced atrial action potential duration (aAPD90) and atrial effective refractory period (aERP). Additional infusion of
aliskiren prolonged aAPD90 but did not alter aERP. A triangulation of action potential with ACh/Iso and a further triangulation
after treatment with
aliskiren were noted. Vulnerability to AF was tested by employing trains of burst pacing. Administration of ACh/Iso provoked more episodes of AF (baseline: 26 episodes, Iso/Ach: 48 episodes). Additional treatment with
aliskiren induced AF significantly more often (108 episodes). Another nine hearts were perfused with
aliskiren to examine its ventricular effects. Infusion with
aliskiren abbreviated ventricular APD90 and ERP. Utilizing programmed ventricular stimulation, a trend towards more ventricular arrhythmias in
aliskiren-treated hearts was observed. Though
aliskiren did not reduce aAPD90 or aERP, acute treatment with
aliskiren promoted AF. Triangulation of atrial action potentials, which is an established risk factor for ventricular proarrhythmia, may contribute to the increased atrial vulnerability. This effect may interfere with its recently demonstrated beneficial properties in
atrial remodeling. Of note,
aliskiren might have a proarrhythmic effect on the ventricular level.