Why the study?
Does opening the chest and pericardium alter the external pressure and diastolic filling of the left ventricle in euvolemic anesthetized dogs?
Does opening the chest and pericardium alter the external pressure and diastolic filling of the left ventricle in euvolemic anesthetized dogs?
In a euvolemic canine model, the undisturbed pericardium exerts negligible pressure, and the external pressure of the left ventricle is determined by the negative intrathoracic pressure.
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Negligible pericardial pressure in euvolemic dogs warrants caution in open-chest models; extends determinants of external LV pressure.
We evaluated the contribution of the thorax and the undisturbed pericardium to the external pressure of the euvolemic left ventricle in thirteen anesthetized dogs. Left ventricular (LV) end-diastolic pressure (EDP) in the euvolemic state was 7 +/- 2 mmHg initially and increased to 10 +/- 2 mmHg after the chest and pericardium were opened. LV end-diastolic volume (conductance catheter) was 43 +/- 20 ml initially and did not change after the chest or the pericardium was opened. Intrathoracic (PIT) and pericardial (PPER) pressures were calculated as the difference in LV chamber pressure before and after opening these spaces. Thus for the LV, PIT was -3 +/- 1 mmHg, and PPER was 0 +/- 2 mmHg. Isovolumic relaxation, early diastolic filling, and total diastolic filling were not significantly altered after the chest or pericardium was opened. Thus under euvolemic conditions in this model pericardial pressure is negligible, and the external pressure of the undisturbed left ventricle is negative and equal to intrathoracic pressure.
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Applegate et al. (1990) studied this question.
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