title: Is regional ventricular wall work determined from regional force and shortening always consistent with the law of conservation of energy?
abstract: Contractile properties of a ventricular wall region have often been analyzed by regional force, shortening, and work. Regional force cannot be measured directly and is often indirectly determined from ventricular pressure and geometry, although regional shortening can be measured directly. Regional work can be calculated from these force and shortening values. We examined whether the calculated regional work, which may be mechanically reasonable, is also reasonable from an energetics viewpoint. We calculated regional contractile power (time rate of work) from the regional force and shortening velocity and integrated it globally over the entire ventricular wall, using some conventional geometric models of the ventricle and assumptions of ventricular wall mechanics. We then compared this globally integrated power with the stroke power of the entire ventricle determined directly from ventricular pressure and volume. Results show that the globally integrated regional power is not always identical with stroke power, depending on the model and assumptions used. Therefore, the regional ventricular wall work determined from the regional force and shortening is not always consistent with the law of conservation of energy.
mesh_terms: D006801:Humans; D008433:Mathematics; D008955:Models, Cardiovascular; D009200:Myocardial Contraction; D013318:Stroke Volume; D016276:Ventricular Function