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Abstract

The aim of this study was the assessment of the Regional Myocardial Work (RMW) by measuring the stress-strain relationships in the left myocardium, under basic and ischemic conditions. In 11 swines, 4 Sonometrics crystals were placed in the region perfused by the left anterior descending artery (LAD) circumscribing a tetrahedral myocardial volume (TMV). The 1st crystal was situated 45mm below the pulmonary artery, beside the LAD. Under control of the acquisition device, the 2nd was placed 10mm below the 1st following the LAD, the 3rd 10mm at the left side of the 1st and the 4th in equidistant point between the 1st and the 2nd, 5mm deep within the myocardium. A Millar, omnidirectional pressure catheter was placed within the TMV. The 6 distances and intramyocardial pressure measured were digitized and mathematically synthesized. The variation in TMV strain (µv) and stress (µp) was calculated throughout the cardiac cycle, resulting in 2 equations. The relationships between µp and µv result in a stress-strain loop, from which RMW was calculated. Simultaneously, Pulsed Doppler Tissue Imaging (DTI) assessed systolic (VS), early-diastolic (VE) and latediastolic (VA) myocardial velocities. Measurements were performed under basic (B), during ischemia by occlusion LDA for 40 seconds, after 1 and 15 minutes of reperfusion (Occlusion (O), Reperfusion1 (R1) and 2 (R2) periods). The average of RMW, under basic conditions, wa