Circulatory Response to Release of Chronic Pulmonary Artery Constriction

Abstract

• During investigations of the effects of excercise 1 and sympathomimetic amines on right ventricular function in unanesthetized dogs with normal or hypertrophied right ventricles, a circulatory state characterized by a supernormal stroke volume and cardiac output and by a decreased systemic vascular resistance was demonstrated in dogs studied 10 to 14 days after the release of chronic pulmonary artery constriction. The purpose of this report is to record this phenomenon and to discuss its nature and possible significance. MethodsEleven mongrel dogs (12 to 20 kg body weight) were used. After preliminary observations (study I*), the main pulmonary artery of each dog was tightly banded as described previously 2 for a minimal period of three months. Each animal was reinvestigated while its pulmonary artery was constricted (study II). Then, the constricting bands were removed, and observations were made two weeks (study III) and two months (study IV) later.After study IV, each animal was killed and necropsy was performed. The cleaned and fixed ventricular muscle mass was separated by Herrmann's method, 18 and the right ventricular weight was expressed as a ratio of right ventricular weight (RVW) to left ventricular weight (LVVV). In 11 dogs, two months or more after the release of pulmonary artery constriction, the mean ratio of RVW to LVVV of 0.885 exceeded significantly the ratio, 0.715, derived from Herrmann's data for 200 normal dogs.From the Mayo Clinic and Mayo Graduate School of Medicine, Rochester, Minnesota.Supported in part by Research Grants HE-06249 and HE-09374 from the National Institutes of Health, U. S. Public Health Service.Dr. Tobin was a Special Fellow, National Institutes of Health, U. S. Public Health Service.Accepted for publication March 10, 1963. *Study I was not done in the five dogs used for exercise studies. PREPARATION OF DOGSNo general anesthetic or premedication was used. Dogs were familiarized with the laboratory, restrained on an animal board, and trained to run without restraint on a horizontal treadmill on several occasions before the experiments. Only those animals who tolerated the animal board and were able to run freely were selected. With the dog under generous local anesthesia (2% lidocaine (Xylocaine) in saline), one carotid artery and one jugular vein were exposed. Size 6F Lehman catheters were introduced and manipulated under fluoroscopic and manometric control into the pulmonary artery, right ventricle, right atrium, and aortic arch, as required. Size 5F Lehman catheters were introduced into the superior vena cava for the injection of indocyanine green and into the jugular vein for the infusion of drugs. INSTRUMENTATIONSimultaneous pressures were recorded from the same base line by means of Statham strain gauge transducers with equal sensitivities. The zero reference level was fixed at midthorax. 4The catheter-manometer systems had frequency responses uniform to between 15 and 20 cycles/ sec.Cardiac output was measured by the indicator dilution technic. Indocyanine green (...

Estimating Right Ventricular Stroke Work and the Pulsatile Work Fraction in Pulmonary Hypertension

“…The strong link documented between msePAP and sPAP was consistent with the strong relationship previously documented between sPAP (or systolic RV pressure) and the pressure-time index. [42][43][44] …”

Relation of Increase in Muscle Mass to Performance of Hypertrophied Right Ventricle in the Dog

“…It has been found also that the infusion of sympathomimetic amines into such an animal induces an increase of right ventricular stroke and minute work exceeding that elicited by severe exercise. 2 The object of this investigation was to define the relation of the maximal work of the hypertrophied right ventricle of the conscious intact dog to the maximal work of the normal right ventricle and to the absolute change in muscle mass.…”