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  • 1
    ISSN: 1615-2573
    Keywords: Disease models, animal ; Coronary disease pathology ; Ventricular function, left physiology ; Swine ; Echocardiography methods ; Radionuclide ventriculography ; Hemodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In ischemic heart disease, left ventricular function is affected by a diffuse and segmental loss of myocardium. The decline in the incidence of myocardial infarction and improved early revascularization in acute transmural ischemia predict a change in the natural history of ischemic heart disease. It is now believed that, minor ischemic episodes, which are known to induce multifocal myocardial degeneration, will predominate in the near future. The objective of the present study was to develop a clinically relevant experimental model for investigation of the pathophysiological significance of diffuse ischemic myocardial lesions. Cardiac performance was gradually depressed by selective intracoronary microembolization in 13 pigs. Left ventricular function was quantitated by ejection fraction (EF), pulmonary pressure, cardiac output, and derivatives of left ventricular pressure. Left ventricular volume was estimated by epicardial echocardiography, using a new, unbiased stereological volume estimator. A chronic substudy was performed in order to characterize the histological changes and to evaluate the feasibility of establishing a chronic preparation of the model. Embolization induced acute left ventricular dysfunction; left ventricular pressure change decreased from 966 ± 274 to 637 ± 146mmHg/s, and early diastolic relaxation from 1403 ± 515 to 824 ± 344mmHg/s, respectively. Ejection fraction decreased by 45% ± 5% and cardiac output by 29% ± 11%. End-diastolic volume increased significantly, from 66.1 ± 13.2 to 77.0 ± 19.4 cm3, and end-systolic volume increased from 35.9 ± 13.9 to 52.3 ± 7.6 cm3. No change in heart rate or left ventricular filling pressure was observed. Diffuse ischemic myocardial injury was identified after a mean follow-up of 40 days. Intracoronary microembolization induces acute left ventricular dysfunction due to microinfarcts. Increased left ventricular end-diastolic volume is the initial compensatory response to the acute impairment of cardiac performance in nontransmural myocardial ischemia. This model is suitable for the evaluation of the hemodynamic changes secondary to acute and chronic diffuse loss of functional myocardium.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1615-2573
    Keywords: Pulmonary artery ; Hemodynamics ; Blood velocity ; Pulsed Doppler ultrasound ; Pigs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The aim of this study was to provide detailed data on velocity profile development in the normal porcine main pulmonary artery and its main branches. Under spontaneous hemodynamic conditions in twelve open-chest 90kg pigs, perivascular pulsed Doppler ultrasound was used for blood velocity measurements in the entire cross-sectional area in three axial locations in the main pulmonary artery and along one diameter in the main branches. Computerized threedimensional visualizations of the spatial and temporal development of velocity profiles were made throughout the heart cycle. The results were similar one and two diameters downstream of the pulmonary valve. In the early systolic acceleration phase, the velocity profile became skewed, with the highest velocities (132.7 ± 19.4cm · sec−1) towards the inferior to right superior vessel wall, and rotated counterclockwise 45°–90° during the late acceleration to early deceleration phase in 9 out of 11 pigs. Maximum retrograde velocities (31.4 ± 14.9cm · sec−1) were observed at the inferior to the right superior vessel wall in the late systolic deceleration phase and in early diastole. During diastole, low retrograde to insignificant antegrade velocities were observed. Immediately upstream of the pulmonary bifurcation, the velocity profile disclosed two peaks at locations corresponding to the two main branches. A confined area with retrograde velocities was seen at the right vessel wall in late systole. Low-scale antegrade velocities were observed throughout diastole in the entire cross-sectional area. In the left main branch, the velocity profiles were found to be somewhat skewed towards the left vessel wall, corresponding to the smaller curvature of the left main branch, while the velocity profile in the right main branch was skewed against the superior vessel wall throughout systole. This study thus disclosed that the blood velocity profiles in the main pulmonary artery system were skewed and that mean velocity varied 26%–50% between measuring points, exhibiting an as yet unexplained rotational phenomenon. The skewed velocity profile in the porcine pulmonary trunk indicates that single-point blood velocity measurements can only serve as a basis for cardiac output estimations when used with considerable caution.
    Type of Medium: Electronic Resource
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