Left Ventricular Contractance: A New Measure of Contractile Function

Aims: Myocardial contractility is poorly defined and difficult to compare between studies. Contractance or myocardial active strain energy (MASED) measures the mechanical work done per unit volume (with units of KJ/m³) of any cardiac tissue in generating contractile stress and undergoing strain. Contractance is an ideal candidate for measuring contractile function as it combines information from stress and strain.<br><br>Methods and results: Data obtained from a previously published experimental study by Guccione and colleagues on trabecular tissue was used to provide contemporaneous nominal stress and strain data and calculate the contractance in twelve different scenarios with different loading conditions. Contractance varied in the differing loading conditions with values of 1.16 (low preload), 2.02 (high afterload) and 3.76 KJ/m³(normal).<br><br>Conclusion: We showed that calculating contractance was feasible and provided a measure of energy production (work done) per unit volume of myocardium during contraction. The new term for contractile function, contractance, can be defined and quantified by MASED. The highest values for contractance were obtained when preload and afterload were normal. The method of measuring active strain energy density is transferable to assessment of global and regional systolic function.