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Perioperative preservation of myocardial ultrastructure and high-energy phosphates in man
Insights
Hypothermic potassium cardioplegia effectively preserves heart muscle structure but shows imperfect preservation of high-energy phosphates like adenosine triphosphate (ATP) and creatine phosphate (CP). This cardiac preservation technique requires further optimization for energy phosphate levels.
Area of Science:
- Cardiology
- Cardiac Surgery
- Biochemistry
Background:
- Myocardial preservation is crucial during cardiac surgery.
- Hypothermic crystalloid potassium cardioplegia is a common technique.
- Assessing its impact on myocardial ultrastructure and energy phosphates is vital.
Purpose of the Study:
- To evaluate the efficacy of multidose hypothermic crystalloid potassium cardioplegia.
- To determine its effect on myocardial ultrastructure.
- To assess the preservation of high-energy phosphates (ATP and CP).
Main Methods:
- Studied 25 patients undergoing cardiac procedures with preserved ejection fraction.
- Obtained left ventricular apex biopsy specimens at three time points: pre-cross-clamp, post-release, and 30 min post-release.
- Analyzed specimens for adenosine triphosphate (ATP), creatine phosphate (CP), and electron microscopy (mitochondrial grading).
Main Results:
- No significant difference in mitochondrial scores, indicating excellent ultrastructural preservation.
- ATP reduced to 78% and CP to 32% of control post-cross-clamp release.
- In patients with cross-clamp times ≥90 minutes, ATP and CP were significantly reduced (71% and 53% of control, respectively) 30 minutes post-release (p ≤ 0.01).
Conclusions:
- Hypothermic potassium cardioplegia provides excellent myocardial ultrastructure preservation in humans.
- The technique demonstrates imperfect preservation of high-energy phosphates, particularly with longer cross-clamp times.
- Further research may be needed to optimize energy phosphate recovery.
Abstract:
To establish whether hypothermic crystalloid potassium cardioplegia given in multidose fashion provides adequate preservation of myocardial ultrastructure and high-energy phosphates, we studied 25 patients with an ejection fraction of 50% or higher who were undergoing cardiac procedures. Eight patients had three biopsy specimens taken from the left ventricular apex for determination of adenosine triphosphate (ATP) and creatine phosphate (CP). Specimens were taken immediately prior to aortic cross-clamping, immediately after the release of the aortic cross-clamp, and 30 minutes after the release of the cross-clamp. Seventeen patients had six specimens taken form the left ventricular apex at the above-stated times, three for ATP and CP determination and three additional specimens for electron microscopy. One patient had a small perioperative infarction and another patient died on the fifth postoperative day of an aortic dissection. The mitochondria on the electron microscopic specimens were graded on a scale from 0 to 4 (4 = severe changes). There was no significant difference in the mitochondrial scores. The preservation oh high-energy phosphates was less complete. ATP was reduced to 78% (3.4.2) of control and CP was reduced in the immediate postclamp period to 32% (081/2.5)of control. The difference are particularly significant if one looks at patients whose aortic cross-clamp time was 90 minutes or more (12 patients). In this group, ATP an CP preservation were 71% of control (3.33/4.60 mmoles/kg. wet weight) and 53% of control (l.48/2.81), 30 minutes after clamp removal (p equal to or less than 0.01). We conclude that hypothermic potassium cardioplegia gives excellent preservation of the myocardial ultrastructure in man. However, the preservation of high-energy phosphates with this technique is imperfect.