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Extravascular water content of heart and lungs after acute myocardial ischemia
Insights
Acute myocardial ischemia, induced by coronary artery ligation, increases heart and lung water content. This suggests ischemia enhances vascular permeability, impacting fluid balance beyond just hemodynamic changes.
Area of Science:
- Cardiovascular Physiology
- Pulmonary Edema Pathophysiology
Background:
- Increased extravascular water in the heart and lungs can indicate serious physiological compromise.
- Hemodynamic factors are traditionally considered primary drivers of fluid shifts in pulmonary and cardiac tissues.
Purpose of the Study:
- To investigate the impact of acute myocardial ischemia and increased left atrial pressure on extravascular water content in canine hearts and lungs.
- To determine if hemodynamic changes alone account for increased lung water following coronary artery ligation.
Main Methods:
- Anesthetized dogs underwent sham operations, circumflex artery ligation, increased left atrial pressure (Pla), or a combination of increased Pla and ligation.
- Extravascular water content in hearts and lungs was measured after 4 hours.
- Left atrial pressure (Pla) and pulmonary microvascular pressure (Pmv) were monitored.
Main Results:
- All experimental groups showed significant increases in heart and lung extravascular water compared to controls.
- Coronary artery ligation alone increased heart water by 29% and lung water by 8% without altering Pla or Pmv.
- Increased Pla significantly elevated heart water, and lung water correlated hyperbolically with Pmv.
- Dogs with coronary artery ligation exhibited greater lung water at equivalent Pmv levels compared to control dogs.
Conclusions:
- Increased extravascular lung water following coronary artery ligation is not solely explained by hemodynamic mechanisms.
- Acute myocardial ischemia appears to play a role in increasing vascular permeability in both the heart and lungs.
- These findings highlight a non-hemodynamic contribution of ischemia to fluid accumulation in cardiovascular tissues.
Abstract:
We measured the extravascular water content of hearts and lungs of anesthetized dogs subjected to one of the following protocols: a)sham operation, b) circumflex artery ligation, c) increased left atrial pressure (Pla), or d) increased Pla and circumflex artery ligation. After 4 h, extravascular water of the heart and lungs increased significantly in the three experimental groups when compared with values from sham-operated dogs. After circumflex artery ligation, extravascular heart water increased 29% and lung water 8%, although Pla and calculated pulmonary microvascular pressure (Pmv) did not change. Extravascular heart water also rose 30% after increasing Pla from 23 to 37 cm H2O by inflating a left atrial baloon. In these dogs, extravascular lung water increased as a hyperbolic function of Pmv. Increasing Pla to 20 cm H2O in dogs with coronary artery ligation resulted in a 16% increase in heart water. Also at each Pmv, extravascular lung water was greater in dogs with coronary artery ligation than in dogs without. These data indicate that the increased extravascular lung water after coronary artery ligation cannot be explained solely by hemodynamic mechansims. We suggest that acute myocardial ischemia contributes to an increase in vascular permeability in the heart and lungs.