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Normothermic continuous antegrade blood cardioplegia does not prevent myocardial edema and cardiac dysfunction
U Mehlhorn1, S J Allen, D L Adams
1Department of Anesthesiology, University of Texas-Houston Medical School 77030, USA.
Insights
Normothermic continuous blood cardioplegia (BC) causes myocardial edema and cardiac dysfunction by decreasing lymph flow, despite preventing ischemia during cardiac surgery. Interventions to increase lymph flow may mitigate these negative effects.
Area of Science:
- Cardiovascular Surgery
- Cardiac Physiology
- Myocardial Protection
Background:
- Normothermic continuous blood cardioplegia (BC) is used for myocardial protection during cardiac surgery.
- Previous studies suggest BC may induce myocardial edema, leading to cardiac dysfunction.
- This study investigates the impact of BC on myocardial fluid balance and left ventricular function.
Purpose of the Study:
- To evaluate the effect of normothermic continuous blood cardioplegia on myocardial fluid balance.
- To assess the impact of BC on left ventricular function and cardiac performance.
- To determine the relationship between BC, myocardial edema, and cardiac dysfunction.
Main Methods:
- 11 dogs underwent normothermic cardiopulmonary bypass with BC delivered at high (80-90 mm Hg) or low (40-50 mm Hg) pressures.
- Myocardial water content (MWC) was measured by microgravimetry.
- Myocardial lymph flow rate was measured, and preload recruitable stroke work (PRSW) was calculated to assess left ventricular function.
Main Results:
- BC significantly decreased myocardial lymph flow rate and induced myocardial edema in both high and low-pressure groups.
- Myocardial water content increased significantly during BC administration.
- Left ventricular function, assessed by PRSW, decreased significantly after CPB in both BC groups.
- Increasing myocardial lymph flow rate post-CPB led to reduced edema and improved PRSW.
Conclusions:
- Normothermic continuous blood cardioplegia compromises cardiac function despite preventing ischemia.
- Cardiac dysfunction is attributed to myocardial edema resulting from increased microvascular fluid filtration and reduced lymph flow during BC.
- Strategies to enhance myocardial lymph flow may be crucial for mitigating BC-induced cardiac dysfunction.
Background:
Normothermic continuous blood cardioplegia (BC) has been proposed to completely protect the myocardium during cardiac surgery. However, previous work from our laboratory suggests that BC could cause myocardial edema that produces cardiac dysfunction. The purpose of this present study was to evaluate the impact of BC on myocardial fluid balance and left ventricular function.
Methods And Results:
In 11 dogs, myocardial water content (MWC) was determined by microgravimetry. Myocardial lymph flow rate was measured after cannulation of the major prenodal cardiac lymphatic. Preload recruitable stroke work (PRSW) was calculated by sonomicrometry and micromanometry. The dogs were placed on normothermic cardiopulmonary bypass (CPB), and BC was delivered at either 80 to 90 mm Hg (BChigh; n = 6) or 40 to 50 mm Hg (BClow; n = 5) for 1 hour. Coronary sinus lactate and oxygen saturation monitoring demonstrated ischemia avoidance. BC was associated with substantial myocardial lymph flow rate decrease (P < .05) and myocardial edema development in both groups. MWC increased from 76.0 +/- 1.9% to 79.2 +/- 1.7% (P < .05) after 10 minutes of BChigh and from 75.9 +/- 0.6% to 78.9 +/- 1.4% (P < .05) after 30 minutes of BClow. PRSW decreased to 63 +/- 19% (BChigh) and 69 +/- 15% of control (BClow) at 30 minutes after CPB (P < .05). Myocardial lymph flow rate increases of threefold to fourfold that of control (P < .05) resulted in significant myocardial edema reduction associated with PRSW improvement to 71 +/- 17% (BChigh) and to 78 +/- 11% (BClow) at 2 hours after CPB.
Conclusions:
We conclude that BC is associated with compromised cardiac function despite ischemia avoidance. This cardiac dysfunction is due to myocardial edema caused by the combination of increased myocardial microvascular fluid filtration and decreased myocardial lymph flow rate during BC.