Abstract
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.
Highlights
Heart failure (HF) is the inability of the heart to provide enough perfusion to the body to meet metabolic demands
To analyze how the initial design of a circular compressive sleeve would interact with the heart, two axisymmetric left ventricular models were constructed in prolate spheroidal coordinates (Fig 1)
The maximum principal stresses in the compression region were analyzed for both models at the epicardium and endocardium (Fig 3A and 3B) and compared; since local stresses are inherently less accurate than strains or hemodynamics, this comparison is a good test
Summary
Heart failure (HF) is the inability of the heart to provide enough perfusion to the body (and itself) to meet metabolic demands. This syndrome is the number one killer of Americans, contributing to one in every nine deaths in this country and afflicting about 2% (75 million) of the adult population worldwide [1,2,3]. Cardiac transplantation is considered to be the definitive treatment for end stage heart failure, but this option is limited due to the severity of the surgery, the need for lifelong medications and a small donor pool[12]. Implantable ventricular assist devices (VADs) are another alternative for patients needing long-term circulatory support, but conventional VAD therapy has its own limitations when used as “destination therapy.”. Implantable ventricular assist devices (VADs) are another alternative for patients needing long-term circulatory support, but conventional VAD therapy has its own limitations when used as “destination therapy.” VADs implanted for extended periods (months to years) have been, and continue to be, plagued by driveline infections and thromboembolic events, with prevalence as high as 12% and 17% respectively [13]
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