Maturation of Small Pulmonary Arteries in Puppies

Abstract

The histologic pulmonary vascular changes and the pulmonary arterial pressure changes which occur during the first 13 weeks of life have been studied in mongrel puppies. The histologic changes were based on measurements of the average lumen to wall ratios of arterial vessels 50 to 200 µ in diameter. The pulmonary arterial pressure changes were recorded by direct needle puncture of the main pulmonary artery in anesthetized thoracotomized animals. The average L/W ratios of all neonatal mongrel puppies from separate litters were less than 4.0, the boundary chosen to distinguish neonatal and adult pulmonary arterial vasculature. All puppies younger than 1 month had average L/W ratios below 4.0. Although average mean pulmonary arterial pressures were found to be near adult levels by age 1 week, the ratio of pulmonary to systemic arterial pressure, expressed as a percentage, did not consistently approach adult levels until 1 month of age. The dimensional evolution of small pulmonary arteries and the gradual decline in the ratio of pulmonary to systemic pressure toward near adult levels at 4 weeks suggested a cause-and-effect relationship between these 2 phenomena. Major operative procedures have been performed on puppies 3 to 5 weeks of age with survival. It is proposed that experimental pulmonary hypertension produced in 4-week-old mongrel puppies would closely approximate the situation of a high pressure congenital cardiac shunt in humans without excessive operative mortality.

Quantitative Analysis of the Thickness of Arterial Walls in Complete Transposition of the Great Arteries

“…This physiological process is consistent with the observation that the pulmonary artery reduces its medial thickness rapidly after birth (Phillips et al 1960;Herzenberg and Eskelung 1961;Naeye 1961) . From our studies it was ascertained that the medial attenuation of infants with normal cardiovascular systems ceased to progress after five months.…”

“…As is now universally accepted, high leveled pulmonary arterial pressure is observed in newborn infants, but subsides to a low mature level within several months (Rowe and James 1957; Phillips et al 1960;Lucas et al 1961; Rudolph and Nadas 1962; Emmanouilides et al 1964). This physiological process is consistent with the observation that the pulmonary artery reduces its medial thickness rapidly after birth (Phillips et al 1960;Herzenberg and Eskelung 1961;Naeye 1961) .…”

Hereditary Patent Ductus Arteriosus and Its Sequelae in the Dog

“…According to previous investigations, the ductus arteriosus in the dog is anatomically closed (no longer probe patent) by the end of the first week of life, although histologic changes in the architecture of the vessel continue for some time after that (13)(14)(15)(16). Gross anatomic or clinical evidence of patency of the ductus arteriosus beyond 1 week of age can thus reasonably be assumed to be abnormal in the dog, but patency prior to 1 week has uncertain significance.…”

Aortic Origin of the Right Pulmonary Artery

“…Previous examinationis in case 3 at 3 and 12 ''adult''-type vasculatiire has replaced the ''fetal' eharaeteristics as defined by lumen-wall ratios. 23 It would be of interest to observe whether t-lie experineniital production of pulmoniary livpertension in one lung of newborn animals conditions the dlevelopment of pulmonary vascular (lisease in the couitralateral lunig in order …”