Conversion of fiber stress to global left ventricular pump work

Abstract

In the present study, muscle fiber stress (Tf) and strain in the wall of the left ventricle is expressed as a function of left ventricular pressure (plv) and the ratio of cavity volume (Vlv) to wall volume (Vw). Muscle fiber stress is assumed to be homogeneously distributed within the wall. The left ventricle may be represented by a thick-walled cylinder as well as by a thick-walled sphere. For both cases: Tf = 3 plv/1 n(1 + Vw/Vlv). From the latter equation, a relation is derived between cavity volume and fiber strain. The ratio of cavity to wall volume appears to be the only relevant geometric parameter. The real geometry of the left ventricle is close to an ellipsoid, which is in between a cylindric and a spherical geometry. So, the relation found may be valid for a wide variety of realistic cardiac shapes. Fiber stress calculated with the present model appears to be 1.5 to 2 times higher than circumferential stress calculated with existing models, depending on the assumed geometry. This difference is in agreement with our current understanding of fiber stress in relation to circumferential stress.KeywordsLeft VentricleFiber StressLeft Ventricular VolumeLeft Ventricular PressureCircumferential StressThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.