The sequence of regional ventricular motion

The chronology of electrical events that mechanically activate the myocardium has been described as initiating at the level of the septum, spreading to the apex, then to the bodies of both ventricles and eventually to the base of the heart (apex-to base activation). It has recently been suggested that the myocardium is a single muscular band that conforms a double-loop helicoid. Contraction of the myocardium would follow the trajectory of the muscular fibers that originate at the pulmonary artery towards the body of the left ventricle and to the aorta (base-to apex contraction). This would explain the movements of the base of the heart and the twisting motion of the ventricles seen at magnetic resonance studies.