Left ventricular simulation of cardiac compression: Hemodynamics and regional mechanics

Heart failure is a global epidemic. Left ventricular assist devices provide added cardiac output for severe cases but cause infection and thromboembolism. Proposed direct cardiac compression devices eliminate blood contacting surfaces, but no group has optimized the balance between hemodynamic benefit and excessive ventricular wall strains and stresses. Here, we use left ventricular simulations to apply compressions and analyze hemodynamics as well as regional wall mechanics. This axisymmetric model corresponds with current symmetric bench prototypes. At nominal pressures of 3.1 kPa applied over the epicardial compression zone, hemodynamics improved substantially. Ejection fraction changed from 17.6% at baseline to 30.3% with compression and stroke work nearly doubled. Parametric studies were conducted by increasing and decreasing applied pressures; ejection fraction, peak pressure, and stroke work increased linearly with changes in applied compression. End-systolic volume decreased substantially. Regional mechanics analysis showed principal stress increases at the endocardium, in the middle of the compression region. Principal strains remained unchanged or increased moderately with nominal compression. However, at maximum applied compression, stresses and strains increased substantially providing potential constraints on allowable compressions. These results demonstrate a framework for analysis and optimization of cardiac compression as a prelude to biventricular simulations and subsequent animal experiments.