Determination of Regional Area Stroke Work with High Spatial Resolution in the Heart

Abstract

Coronary artery disease generally leads to regional myocardial dysfunction. This necessitates a high spatial resolution technique that is able to determine whole-field regional myocardial function. We have therefore developed the technique of computer-aidedspeckle interferometry (CASI) for measuring myocardial function in the beating heart. Six isolated rabbit hearts were perfused in a modified Langendorff apparatus, which allowed for the hearts to be perfused in the working mode. A pressure transducer was inserted through the apex into the left ventricular (LV) cavity to measure LV pressure. Silicone carbide particles were placed on the anterior surface of LV and used as displacement markers. The anterior surface of the left ventricle was imaged with a CCD camera at 50 frames per second. The CASI technique was used to determine the displacementof regions of myocardium on the basis of the deformation distribution (via displacement vectors) within the region of interest. From this information, changes in regional area were determined as a function of LV pressure, leading to the determination of regional area stroke work (RASW; the integral of LV pressure with respect to regional area). The average region of interest in the six hearts was 19.7 ± 5.9 mm2. The average RASW over the regions of interest was 3.1 ± 0.7 mmHg (with the regional area normalized to end-diastolic area). The region of interest was further divided into subregions, each representing an average of 1 mm2 of myocardium. Within a subregion, more than 20 displacement vectors were determined, which were used to calculate the change in regionalarea and RASW for a given subregion. CASI is an effective whole-field technique to determine regional function with better than 1-mm spatial resolution in the isolated beating heart.