Possible pathophysiology of torsade de pointes evaluated by a realistic heart computer model

A realistic computer model that closely simulates the behaviour of the cardiac conduction system and myocardium in producing electrocardiographic records was used to evaluate some hypotheses of the pathophysiological mechanisms causing torsade de pointes tachycardia. Five different groups of experiments showed that pathological phenomena of different natures can either directly cause the usual pattern of torsade de pointes or contribute to its occurrence. The phenomena investigated were coincidence of two or more pathological foci with slightly changing periods of impulse generation; periodical disturbances of the conduction velocities of the main branches of the conduction system; a single pathological focus changing its position by slowly moving around the whole heart or around a local area of the myocardium; combination of a pathological ventricular tachycardia focus with a one way (ventriculoatrial) direct atrioventricular accessory pathway allowing atrioventricular re-entry; and different repolarisation periods of separate areas of heart muscle in the presence of a pathological ventricular focus with a fixed or oscillating rate of impulse generation. Future extended versions of the model could be used for testing other hypotheses of the origin of torsade de pointes, such as situations in which the intramuscle or local re-entry occurs.