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Myocardial protection by intermittent perfusion with cardioplegic solution versus intermittent coronary perfusion
Insights
Buffered cardioplegic solution with potassium arrest offers superior myocardial protection compared to cold blood perfusion during aortic cross-clamping. This method preserves left ventricular function and reduces edema.
Area of Science:
- Cardiovascular Surgery
- Cardiothoracic Research
- Myocardial Preservation
Background:
- Myocardial protection during cardiac surgery is critical.
- Cold blood perfusion is a common method for myocardial protection.
- The efficacy of different myocardial protection strategies requires evaluation.
Purpose of the Study:
- To compare the myocardial protective effects of a buffered, isosmotic potassium cardioplegic solution (CS) versus intermittent cold blood (CB) perfusion.
- To assess myocardial function, compliance, and tissue water content after aortic cross-clamping.
- To evaluate the impact of these methods on myocardial metabolism.
Main Methods:
- A canine model was used with 2 hours of aortic cross-clamping.
- Group CS received cardioplegic solution; Group CB received intermittent cold blood perfusion.
- Myocardial function, compliance, extravascular water content, and metabolism were measured post-reperfusion.
Main Results:
- Cardioplegic solution (CS) maintained left ventricular (LV) function and compliance, unlike cold blood (CB) which showed significant reductions.
- Group CS exhibited normal myocardial ultrastructure, while Group CB showed extracellular edema and higher water content.
- Metabolic markers like lactate and pyruvate consumption were reduced in both groups, more so in Group CB.
Conclusions:
- Buffered, isosmotic potassium cardioplegic solution provides superior myocardial protection compared to intermittent cold blood perfusion.
- Potassium-induced arrest in cardioplegic solution significantly reduces myocardial metabolism, enhancing protection.
- This study highlights the benefits of cardioplegia for preserving myocardial integrity during cardiac procedures.
Abstract:
The myocardial protection provided by cardioplegic solution using buffered, isosmotic potassium (30 mEq. per liter) was compared with intermittent cold coronary perfusion for 2 hours of aortic cross-clamping in dogs. The cardioplegic solution (Group CS) or cold blood (Group CB) was infused every 15 minutes through a cooling coil to reduce the perfusate temperature to 5 degrees C. Myocardial function after 30 minutes of reperfusion and rewarming was reduced in Group CB with a significant reduction in peak systolic pressure at a left ventricular (LV) balloon volume of 20 ml. and a significant reduction of dp/dt. In contrast, in Group CS, LV function was unchanged from the base-line period. LV compliance also was significantly reduced in Group CB while being unchanged in Group CS. Myocardial extravascular water content, obtained by dessication, was significantly higher in Group CB than in Group CS, which may explain the reduction in compliance. Electron microscopy showed normal ultrastructure in Group CS but extracellular edema in Group CB. Total coronary blood flow showed a sustained increase during reperfusion in both groups. Oxygen consumption rose with rewarming to base-line levels in both groups, whereas lactate and pyruvate consumption was reduced in both groups, particularly Group CB. Cardioplegic solution thus appears to be superior to the intermittent perfusion of cold blood for myocardial protection. The addition of potassium arrest, by markedly reducing myocardial metabolism, improves the protection afforded by cold blood perfusion alone.