Assessment of myocardial function by calculation of two energetic parameters from pressure-volume relations and wall...

For defining myocardial performance in chronic cardiac diseases and during acute pharmacological interventions we created a new index of performance based on myocardial mechanical and energetic counterparts. From angiocardiographic pressure-volume data the pressure-volume integral is analyzed and divided by left ventricular muscle mass, yielding work done by a unit of myocardium (E1). From pressure-volume data the stress-time integral integral of sigma.t is evaluated by using an ellipsoidal calculation model. In order to compare E1 with the integral of sigma.t the integral of sigma.t is transformed into energetic units on the basis of new physiologic myothermal findings (E2). Then, the sum of E1 and E2 (i.e.,the maximum of mechanical performance), the ratio of E1 to the sum of E1 and E2 can be defined (i.e., the myocardial work related to the energy consumed during a contraction). By calculating E1 and E2, we are able to analyze the myocardial efficiency of work production. These parameters are proposed for judging the myocardial performance and efficiency in congestive heart failure and the effects of positive inotropic substances and vasodilators.