title: Method for stable measurement of the electrocardiogram in isolated guinea pig heart. Evaluation of the RR-QT relationship and the effect of quinidine.
abstract: A method for stable measurement of ECG in an excised guinea pig heart was presented. The effects of quinidine and its major metabolite, 3-OH quinidine, on QT interval were compared using excised guinea pig hearts with A-V nodal rhythm paced at a constant frequency (190 beats/min). The relative potency of 3-OH quinidine to its parent drug was about one-fourth. Taking into account the fact that the free fraction of 3-OH quinidine in blood is larger than quinidine, this metabolite may contribute to the effects of quinidine in man. Changing the frequency of electrical pacing in excised hearts with A-V nodal rhythm, the RR-QT relation was determined to be rather linear, and this relation became more curvilinear after addition of quinidine (2 mg/liter), suggesting that the Bazett's formula for correcting QT interval with the heart rate is not applicable to guinea pig heart and/or after an addition of drug.
mesh_terms: D000818:Animals; D004562:Electrocardiography; D005260:Female; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D011802:Quinidine / Q000031:analogs & derivatives / Q000494:pharmacology*
chemical_list: C013569:3-hydroxyquinidine; D011802:Quinidine