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Improved protection of the hypertrophied left ventricle by histidine-containing cardioplegia
K Takeuchi1, P Buenaventura, H Cao-Danh
1Department of Cardiac Surgery, Children's Hospital, Harvard Medical School, Boston, Mass 02115, USA.
Insights
Histidine-containing solution (HBS) improves heart preservation during ischemia by buffering acid and promoting anaerobic glycolysis. This enhances recovery of high-energy phosphates and contractile function in hypertrophied hearts.
Area of Science:
- Cardiology
- Biochemistry
- Physiology
Background:
- Myocardial hypertrophy increases susceptibility to ischemia.
- Ischemia in hypertrophied hearts leads to rapid loss of energy stores and impaired function.
Purpose of the Study:
- To investigate if buffering acid during ischemia improves hypertrophied heart preservation.
- To assess the effect of histidine-containing solution (HBS) on cardiac function and energy levels.
Main Methods:
- Studied hypertrophied rabbit hearts subjected to ischemia and reperfusion.
- Compared HBS with St. Thomas solution and high-potassium Krebs buffer.
- Measured contractile function, high-energy phosphates (PCr, ATP), intracellular pH, and lactate production.
Main Results:
- HBS group showed significantly higher PCr, ATP, and intracellular pH compared to control groups.
- Left ventricular developed pressure recovery was highest (91%) in the HBS group.
- Increased lactate production in the HBS group suggested enhanced anaerobic glycolysis.
Conclusions:
- Histidine-containing cardioplegia improves recovery of high-energy phosphates and contractile function in hypertrophied hearts.
- Promoting anaerobic glycolysis via HBS aids in preserving cardiac function during ischemic events.
Background:
Myocardial hypertrophy has been shown to lead to increased susceptibility to ischemia with accelerated loss of high-energy nucleotides, greater accumulation of H+ and lactate, and earlier onset of contracture.
Methods And Results:
To determine whether promoting anaerobic glycolysis during ischemia by buffering H+ results in improved preservation of the hypertrophied heart, we studied the effect of a histidine-containing solution (HBS) on recovery of contractile function and energetic state. Hypertrophied rabbit hearts (aortic banding at 10 days) were subjected to 40 minutes of 37 degrees C ischemia and reperfusion in an isolated Langendorff model. This group was compared with groups receiving St Thomas solution and high-potassium Krebs buffer solution (KCl). Although both phosphocreatine (PCr) and ATP were lower in hypertrophied hearts by end-ischemia compared with nonhypertrophied age-matched controls, there was significantly higher PCr, ATP, and intracellular pH in the HBS group compared with the St Thomas and KCl groups. Recovery of left ventricular developed pressure was best in the HBS group (91% of preischemic values) as was end-diastolic pressure after 30 minutes of reperfusion. Lactate production was also significantly greater in the HBS group, suggesting augmentation of anaerobic glycolysis.
Conclusions:
We concluded that administration of histidine-containing cardioplegia promotes anaerobic glycolysis and improves recovery of high-energy phosphates and contractile function in hypertrophied myocardium.