REGIONAL MYOCARDIAL PERFUSION AND MECHANICS - A MODEL-BASED METHOD OFANALYSIS

A new parametric model-based method has been developed that allows epi cardial strain distributions to be computed on the left ventricular fr ee wall in normal and ischemic myocardium and integrated with the regi onal distributions of anatomic and physiological measurements so that underlying relationships can be explored. An array of radiopaque marke rs was sewn on the anterior wall of the left ventricle (LV) in three a nesthetized open-chest canines, and their positions were recorded usin g biplane video fluoroscopy before and 2 min after occlusion of the le ft anterior descending coronary artery. The three-dimensional (3D) ana tomy of the LV and epicardial fiber angles were measured post-mortem u sing a 3D probe. A prolate spheroidal finite element model was fitted to the epicardial surface points (with <0.2 mm accuracy) and fiber ang les (<5 degrees error). Regional myocardial blood flows (MBFs) were me asured using fluorescent microspheres and fitted into the model (<0.3 ml min(-1) g(-1) error). Epicardial fiber and cross-fiber strain distr ibutions were computed by allowing the model to deform from end-diasto le to end-systole according to the recorded motion of the surface mark ers. Systolic fiber strain varied from -0.05 to 0.01 within the region of the markers during baseline, and regional MBF varied from 1.5 to 2 .0 ml min(-1) g(-1). During 2 min ischemia, regional MBF was less than 0.3 ml min(-1) g(-1) in the ischemic region and 1.0 ml min(-1) g(-1) in the nonischemic region, and fiber strain ranged from 0.05 in the ce ntral ischemic zone to - 0.025 in the remote nonischemic tissue. This analysis revealed a zone of impaired fiber shortening extending into t he normally perfused myocardium that was significantly wider at the ba se than the apex. A validation analysis showed that a regularizing fun ction can be optimized to minimize both fitting errors and numerical o scillations in the computed strain fields. (C) 1998 Biomedical Enginee ring Society. [S0090-6964(98)01505-7].