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The effects of cardioplegia washout on myocardial preservation
Insights
Cardioplegia washout by noncoronary blood flow can impair myocardial preservation in vivo. Slow perfusion during preservation at 30°C improved cardiac function and ATP levels, suggesting washout itself isn't detrimental.
Area of Science:
- Cardiovascular Surgery
- Cardiothoracic Research
- Myocardial Preservation
Background:
- Myocardial preservation in vivo is less effective than in vitro, potentially due to cardioplegia washout by noncoronary collateral flow.
- Understanding washout effects is crucial for improving cardiac surgical outcomes and reducing myocardial damage.
Purpose of the Study:
- To investigate the impact of cardioplegia washout via low-flow perfusion on myocardial preservation during hypothermic storage.
- To assess the effects of temperature and perfusion on myocardial function and biochemical markers.
Main Methods:
- Isolated dog hearts underwent 2-hour preservation at 20°C or 30°C with retrograde coronary sinus perfusion.
- Perfusion strategies included blood cardioplegia, normal blood, or no perfusion to simulate washout.
- Evaluated left ventricular function, tissue water/electrolytes, and high-energy phosphates (ATP) pre-, during-, and post-preservation.
Main Results:
- At 20°C, cardioplegia washout did not significantly alter left ventricular function or biochemical markers.
- At 30°C, hearts without washout showed significant ATP loss and impaired recovery of left ventricular function (<30%).
- Low-flow perfusion at 30°C maintained near-normal ATP levels and restored normal cardiac function post-reperfusion.
Conclusions:
- Myocardial warming by noncoronary perfusion negatively impacts myocardial preservation.
- Slow cardioplegia washout itself does not appear detrimental to myocardial preservation, even at higher temperatures.
- Maintaining adequate cardioplegia levels through slow perfusion may be key to preserving cardiac function during hypothermic storage.
Abstract:
Preservation of the myocardium in vitro is more effective than preservation in vitro when preservation conditions are apparently the same. The washout of cardioplegia from the myocardium by noncoronary blood flow has been implicated as a probable cause of the poorer myocardial preservation seen in vivo. Isolated dog hearts were used to study the effects of cardioplegia washout by low flow perfusion (0.05 ml/min/g LV weight) during a 2-hr preservation period. Six experimental groups of five hearts each underwent 2 hr of myocardial preservation at temperatures of 20 degrees C (three groups) or 30 degrees C (three groups). The three groups for each temperature consisted of retrograde coronary sinus perfusion (to simulate cardioplegia washout by collateral flow) with blood cardioplegia (BC), normal blood (NB), or no perfusion at all (No CSP). The quality of preservation in each group was assessed by measuring recovery of left ventricular function, tissue water and electrolyte content, and myocardial high-energy phosphate and adenylate content prior to, during, and following preservation. In hearts maintained at 20 degrees C, cardioplegia washout did not significantly affect left ventricular function or myocardial levels of H2O, Na, K, ATP, or total adenylates. When myocardial temperature was allowed to increase to 30 degrees C, preservation was better with low flow perfusion during the preservation period. Hearts warmed to 30 degrees C with no cardioplegia washout experienced a 50% loss of tissue ATP levels and recovered less than 30% of normal left ventricular function during a 150-min reperfusion period. In contrast, hearts slowly perfused during the preservation period maintained nearly normal levels of ATP and returned to normal function by 150 min of reperfusion. Although myocardial warming by noncoronary perfusion has a detrimental effect on myocardial preservation, the slow washout of cardioplegia per se has no apparent detrimental effect on preservation.