A comparison of pressure-volume relations of the fetal, newborn, and adult heart.

ROMERO, TOMAS, JAMES COVELL, AND WILLIAM F. FRIEDMAN. A comparison of pressure-volume relations of the fetal, newborn, and adult heart. Am. J. Physiol. 222(5) : 1285-l 290. 1972.-A marked paucity of information exists concerning the physiological characteristics of the developing heart. The purpose of the present investigation was to analyze and compare the compliance of the right and left ventricles in hearts obtained from 8 fetal and 9 newborn lambs and 10 adult sheep. Moreover, to assess the influence of filling of the contralateral chamber on distensibility, the distensibility of each ventricle was determined both with the opposite ventricle empty and at various fixed pressures. Using various models of left and right ventricular geometry, the pressure-volume data were converted to units of wall tension and percentage change in internal radius, allowing a direct comparison of all of the age groups studied. In addition, the concentrations of ventricular hydroxyproline were determined to evaluate the contribution of connective tissue to compliance at each age level. The major findings of the present study indicate that the pressure-volume and wall tension-radius relations of both the left and right ventricles are comparable in the fetal lamb close to term. In the newborn period, the right ventricle has compliance characteristics similar to the right ventricle of the fetus. The adult right ventricle is significantly more compliant than both the fetus and newborn. In the early postnatal period, the left ventricle alters its pressurevolume and stress-strain characteristics and assumes an intermediate position between fetus and adult. At all ages the right ventricle is more compliant than the left ventricle. When one evaluates the influence of filling one ventricle on reducing the distensibility of the opposite ventricle, the most profound effect is observed in the fetus, followed by the newborn, and then the adult.