Electrical Propagation in the Mechanisms of Torsion and Suction in a Three-phase Heart

Background: The hypothesis of Torrent Guasp considers that the ventricular myocardium consists of a continuous muscular band that begins at the level of the pulmonary valve and ends at the level of the aortic root, limiting both ventricular chambers. This anatomy would provide the interpretation for two fundamental aspects of left ventricular dynamics: the mechanism of left ventricu- lar torsion and rapid diastolic filling due to the suction effect. Objectives: The aim of this study was to investigate the electrical activation of the endocardial and epicardial bands to understand ventricular torsion, the mechanism of active suction during the diastolic isovolumic phase and the significance of the residual volume. Methods: Five patients underwent three-dimensional electroanatomic mapping. As the descending band is endocardial and the ascending band is epicardial, two sites of puncture were used. Results: Three-dimensional endo-epicardial mapping demonstrates an electrical activation sequence in the area of the apical loop in agreement with the synchronic contraction of the descending and ascending band segments. The simultaneous and opposing radial activation of the ascending band segment, starting in the descending band segment, in the area in which both band segments inter- twine, is consistent with the mechanism of ventricular torsion. The late activation of the ascending band segment is consistent with its persistent contraction during the initial period of the isovolumic diastolic phase (the basis of the suction mechanism), and takes place without need of postulating further electrical activation after the QRS complex. Conclusions: This study explains the process of ventricular torsion and the suction mechanism, and demonstrates that the activation of the ascending band segment completes the QRS, ruling out the traditional concept of passive relaxation during isovolumic diastole.