[Course of contraction during physiological and ventricular pacemaker stimulation].

Phase imaging of gated radionuclide ventriculography was applied to the identification of cardiac activation patterns in patients with sinus rhythm (n = 14) or with ventricular (VVI)- (n = 28), atrial (AAI)- (n = 3) or AV-sequential (DDD)-pacing (n = 17). In patients with sinus rhythm, AAI- or DDD-pacing, analysis revealed homogeneous distribution of phase across both ventricles. In VVI-pacing a left bundle branch block configuration of the ventricular activation was found in 21 of 28 patients. In 7 of 28 patients phase distribution indicated a simultaneous activation of both ventricles (with or without delimitation of the apex of the right ventricle). This is of clinical importance because artificial spread of excitation and asynchronous contraction during VVI-pacing may be responsible for higher myocardial oxygen demand. Retrograde conduction in VVI-pacing was found in 9 of 28 patients. Phase analysis provides a reliable method for evaluation of pacing-induced activation patterns.