Propagation of electrical excitation in isolated rabbit hearts: Influence of stimulation protocol and spatial coupling

Propagation of electrical excitation in the rabbit heart was computed using a simple realistic ionic model. Excitation was initiated by two different stimulation protocols. The simulations were compared to surface electrograms obtained from autonomously beating rabbit hearts in Langendorff perfusion. Additionally the influence of a gap junction blocking drug (palmitoleic acid) was investigated. After filtering the data, they were characterized by surface propagation speed maps. Under influence of the drug the propagation speeds decreased by 10-20% while the QRS time increased by approximately 10%. The first observation could be confirmed by simulations where the speeds were lowered by 10-30%. The QRS time showed a larger increase by up to 33%. The first protocol with a stimulation near the apex showed a more realistic shape of the QRS complex and reproduced the QRS time more accurately. The second, Purkinje type protocol yielded better agreement concerning the propagation speeds.