QT interval analysis in electrograms of isolated guinea pig hearts treated with haloperidol

The influence of antipsychotic drug haloperidol on repolarization defined by QTc interval was analyzed in electrograms of 8 isolated guinea pig hearts. Each experiment consisted of four phases: stabilization (S). first haloperidol administration (Hi). washout (W). and second haloperidol administration (H2). QTc was computed according to three correction models: Bazett´s, Fridericia´s and dynamic model based on transfer function (TRF). Mean value and standard deviation of QTc were assigned from the interval of 2000 beats in the middle of all four experimental phases. The inaccuracy of QTc given as STD/mean over all phases and experiments was 0.016±0.013, 0.015±0.010 and 0.0039±0.0024 for Bazett, Fridericia and TRF, respectively. The QTc prolongation by haloperidol was confirmed by TRF model. Relative QTcT prolongation caused by haloperidol was (H2-W 0.0062±0.0054, P=0.07) and shortening (H1-W -0.0038±0.0037, P=0.07) caused by washout. The QTcB and QTcF changes were given more by RR changes than haloperidol influence. The dynamic, subject specific model of QT/RR coupling must be used in drugs analysis.