The Law of LaPlace: A dangerous assumption when designing devices for heart failure?

Abstract Introduction: The Myocor Myosplint(r) is designed to reduce left ventricular (LV) wall stress and thereby the stimulus for remodeling (LaPlace's Law). This simplified model does not account for the complex distribution of stress. We hypothesized that the stress at the point of contact between the epicardial pads and the epicardium would be excessively high. Methods: The short axis endocardial and epicardial contours of a reshaped LV were traced from a Myocor marketing brochure and imported into a finite element modeling program. A mesh was generated to create a two-dimensional model of the left ventricular wall. Isotropic, linear material properties were assumed. Two nodes, corresponding to the locations of the epicardial pads, were fixed to simulate the Myosplint. A load was applied to the endocardial surface to simulate pressure, and the resulting strain and reaction forces were recorded. Control data was generated for a normal ventricle. Results: Stress at the contact points between the epicardial pads and the epicardium was 5 times the maximal stress in the control LV and 20 times the stress in the lobes of the reshaped LV. Conclusions: The Law of Laplace does not adequately describe the redistribution of stress in the LV after the application of the Myosplint device. Finite element analysis demonstrates that wall stresses are significantly increased in the region of the epicardial pads. This focal increased wall stress may subvert any possible therapeutic benefit of the Myosplint.