Biomedical subjects

P Steendijk

Publications and source records attributed to P Steendijk.

56 records · Page 4Linked to original sources

PubMedDate not supplied

Effect of coronary occlusion and reperfusion on local electrical resistivity of myocardium in dogs.

The effect of coronary occlusion and reperfusion on myocardial electrical resistivity was studied in nine anesthetized open-chest dogs. Anisotropic resistivity was measured on the anterior free wall of the left ventricle (LV) before (control) and during transient occlusion of the left anterior descending (LAD) coronary artery, and during reperfusion. To measure local resistivity longitudinal (RL) and transverse (RT) to epicardial muscle fiber direction, a sensor was developed based on the four electrode (FE) technique with an electrode distance of 1 mm. Previous calculations showed that measurements with this system were confined to a 2-mm-thick epicardial layer. Control values for RL and RT were 243 +/- 32 ohms.cm and 358 +/- 45 ohms.cm (mean +/- SD, n = 9) respectively. During a 2-min LAD occlusion, RL increased gradually by 12.4% (p < 0.05) and RT by 7.8% (p < 0.05) above the preceding control values. During a 5-min reperfusion period resistivities returned towards control values, but tended to remain elevated. RL showed a slight initial further increase during the first min of reperfusion and remained significantly above control values during 3 min of reperfusion. RT returned to values not significantly different from control after about 1 min of reperfusion.

Animals↗

PubMedDate not supplied

Differential response of the right and left ventricle to beta-adrenergic stimulation: an echo planar MR study in intact animals.

PURPOSE: The purpose of this study was to compare the response in contractility of the right (RV) and left (LV) ventricle of the heart to beta-adrenergic stimulation using an echo planar MR technique. METHOD: In six sheep, RV and LV pressure-volume (P-V) relationships were constructed simultaneously using intraventricular pressures and volumes measured with echo planar MRI at rest and during dobutamine stress. Contractility changes were quantified by assessment of the end-systolic P-V relationship (ESPVR) and the preload recruitable stroke work (PRSW). RESULTS: Both the ESPVR the the PRSW showed a significant increase in contractility for both ventricles after dobutamine administration. The increase in contractility was significantly larger for the LV than for the RV, both measured wit the ESPVR (p < 0.0003) and the PRSW (p < 0.007). CONCLUSION: This study shows the usefulness of echo planar MRI to assess myocardial contractility of both ventricles simultaneously. Furthermore, the study shows that beta-adrenergic stimulation has a significantly greater positive inotropic effect on LV contractility than on RV contractility.

Adrenergic beta-Agonists↗