Spatial properties and effects of ajmaline for epicardial propagation on isolated rabbit hearts: Measurements and a computer study

Time-resolved surface activation time maps recorded from isolated rabbit hearts were analyzed in order to compare them with analogue maps generated by a computer model. Recordings were obtained under normal conditions as well as after the administration of ajmaline. In parallel, the measured quantities were simulated in a realistic computer model of the rabbit heart. The effect of ajmaline was reproduced by reducing the conductivity of sodium channels GNa in the model. It was observed that addition of a given amount of ajmaline leads to an increase of the QRS time of up to 33% and a decrease of typical velocities by 20-40% with respect to the normal conditions. The velocity speeds obtained display large variations. A velocity decrease of about 20% was reproduced in the computer model by a reduction of the parameter GNa by 60%. Such a change in the model induces a corresponding QRS time by 20%.