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Force and oxygen consumption in the immature rabbit heart
1Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas 75335.
Insights
Newborn rabbit hearts show improved force development economy at higher heart rates and pressures compared to adults. This age-related difference in cardiac efficiency is crucial for understanding heart function across development.
Area of Science:
- Cardiovascular Physiology
- Developmental Biology
- Cardiac Metabolism
Background:
- The economy of left ventricular force development, reflecting efficiency, may differ with age.
- Understanding these age-related changes is vital for pediatric cardiology and understanding cardiac aging.
Purpose of the Study:
- To investigate age-related differences in the economy of left ventricular force development in isolated rabbit hearts.
- To assess how heart rate, inotropic stimulation, and preload affect cardiac efficiency across different age groups.
Main Methods:
- Isolated, isovolumic hearts from newborn, juvenile, and adult rabbits were studied.
- Measurements included myocardial oxygen consumption and force development under varying heart rates, isoproterenol, and end-diastolic pressures.
Main Results:
- No significant baseline differences in force development economy were observed.
- Newborn hearts showed a 37% increase in economy with a 20% heart rate increase, unlike juveniles and adults (27% decrease).
- Newborn hearts exhibited a 300% increase in economy with elevated end-diastolic pressure, compared to 160% in adults.
Conclusions:
- Significant age-related differences exist in left ventricular force development economy.
- These differences become apparent under conditions of increased heart rate and end-diastolic pressure, highlighting developmental adaptations in cardiac efficiency.
Abstract:
We speculated that there are important age-related differences in the economy of left ventricular force development in the isolated heart. To assess this, we evaluated oxygen consumption and force development in newborn (less than 1 wk old) (n = 26), juvenile (4-6 wk old) (n = 26), and adult (5-7 mo old) (n = 26) isolated, isovolumic rabbit hearts. Measurements were obtained with three different interventions, including 1) changes in heart rate, 2) inotropic stimulation with isoproterenol, and 3) changes in end-diastolic pressure. We found no significant baseline differences in the economy of force development. However, when heart rate was increased by 20%, the force/oxygen consumption ratio (economy) increased in newborn hearts by approximately 37%, whereas there was a decrease in juvenile and adult hearts of approximately 27%. In addition, with increases in end-diastolic pressure above 10 mm Hg, newborn hearts increased their force/myocardial oxygen consumption ratio to 300% of the baseline value, whereas adults increased to only 160% of baseline. Isoproterenol produced no significant age-related differences in the force/myocardial oxygen consumption ratio. We conclude that there are important age-related differences in the economy of left ventricular force development in this model, but these differences are apparent only at higher heart rates and end-diastolic pressures.