[An experimental model of helicoid ventricular tachycardia (torsades de pointes). Preliminary report].

Studies on twenty dogs were performed. With open thorax, aconitine was injected into the thickness of the interventricular septum. D2 and direct derivations were registered in the epicardium of the right atrium, on right and left septal surfaces and in the His bundle. As the experiment ended, the heart was taken out to determine the placement of the electrodes and the site of application of aconitine. "Torsades de pointes" were obtained in 15 dogs, with a rotation of 180 degrees during the episode. The rotation of A QRS occurred with a beat of intermediate direction which corresponded to a ventricular capture of a sinus beat or a ventricular echo after that beat, and a sequence of activation of AHV established in various beats, the first of which had a prolonged AH (p less than 0.01). The consecutive change of direction of QRS happened when that sequence of activation disappeared, and there was an A-V dissociation as in the beginning of the episode. In conclusion, in this experimental model, the Torsades de pointes were produced by double mechanism, an increased focus of automatism and a macro-re-entry that involves the two branches of the His bundle, the A-V node and the atrium.