Regional work of the human left ventricle calculated by wall stress and the natural logarithm of reciprocal of wall thickness

Department of Cardiovascular Surgery, Tokyo Women's Medical College, Japan.

Regional left ventricular work is a more precise indicator of function than is simple shortening fraction. Regional work of the ventricle normalized to a unit volume of myocardium (RWM) is given by the following equation: RWM = - intergral of sigma d[ln(1/H)], where sigma is the mean wall stress and ln(1/H) is the natural logarithm of reciprocal of wall thickness. This method has been previously validated in animal experiments and it is now extended to the clinical setting for the first time. In 10 normal subjects and 6 patients with anteroseptal myocardial infarction, ventricular minor axis and wall thickness were measured by echocardiography and recorded simultaneously with high fidelity left ventricular pressure. Then, regional work of the interventricular septum and of the posterior wall of the left ventricle was calculated from the measured pressure and dimension data. In normal subjects, regional work of the septum and posterior wall was 6.1 +/- 1.7 and 7.0 +/- 1.8 mJ/cm3, respectively; the average of the septal and posterior wall regional work multiplied by the left ventricular myocardial volume correlated well (r = 0.93) with the total mechanical work done by the entire left ventricle. In patients with anteroseptal infarction, septal regional work was greatly reduced (0.6 +/- 1.7 mJ/cm3), compared with posterior wall regional work in the same patients (6.1 +/- 1.8 mJ/cm3). This simple method can be applied clinically in assessing the functional state of different regions of the myocardium.

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