Systolic anterior motion in hypertrophic cardiomyopathy: a fluid-structure interaction computational model

We present direct numerical simulations for the pathophysiology of hypertrophic cardiomyopathy of the left ventricle of the human heart. This cardiovascular disorder manifests itself through systolic anterior motion (SAM), a drift of the mitral leaflets towards the aortic subvalvular region, sometimes causing ventricular obstruction during systole. This pathology is induced by a combination of factors, including a thickening of the interventricular septum and an elongation of the mitral valve leaflets: we perform a full parametric study to assess their effect on the disease. From our results we observe that SAM occurs when elongated leaflets, hypertrophic ventricles and strong ejection fraction are present at the same time. In contrast, a physiological ventricle with elongated leaflets, an hypertrophic ventricle with physiological leaflets or diseased ventricle and leaflets with a weak ejection fraction do not produce SAM. After verifying that the numerical results are consistent and in agreement with the clinical data from the literature, we virtually test the two standard surgical procedures, leaflet plication and septal myectomy, adopted for the surgical treatment of SAM. For all the considered cases we obtain quantitative confirmation for the reliability of the intraventricular subvalvular pressure drop (or subvalvular pressure gradient for the medical community) as diagnostic indicator of the systolic anterior motion: when this quantity attains the value of 30 mmHg, SAM of the mitral leaflets is observed, while when this threshold is exceeded the SAM becomes obstructive. On the other hand, in all cases for which SAM is not observed the above pressure drop is always below the threshold.