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Biomedical subjects

W F Friedman

Publications and source records attributed to W F Friedman.

At least 109 records · Page 6Linked to original sources
PubMed1976

Pharmacologic closure of patent ductus arteriosus in the premature infant.

The prostaglandins affect smooth-muscle tone of the ductus arteriosus. Patent ductus often complicates the clinical course of prematurely born infants with respiratory-distress syndrome. In the present study, a single oral or rectal dose of a potent inhibitor of prostaglandin synthesis, indomethacin, was administered to six consecutive premature infants with the syndrome who would otherwise have undergone surgical ligation of the patent ductus. Within 24 hours all the clinical symptoms and physical, echocardiographic and radiographic signs attributable to substantial left-to-right shunting through a patent ductus arteriosus dramatically and permanently disappeared. A transient reduction in renal function was observed in two infants in whom sustained ill-effects did not occur. The observation that constriction and closure of the patent ductus arteriosus may be induced pharmacologically raises important possibilities for the improved treatment of the respiratory-distress syndrome.

Cyclooxygenase Inhibitors↗
PubMed1976

Echocardiographic detection of large left to right shunts and cardiomyopathies in infants and children.

Diagnostic separation of infants with signs of cardiac failure (hypoglycemia, sepsis, myocarditis, hypoxemia) but no congenital cardiocirculatory malformation from those with a large left to right shunt is crucial in newborn management. Echocardiographic studies of 218 infants and children allowed group separation and distinction from normal by the assessment of mean velocity of circumferential fiber shortening (Vcf) and the ratio of left atrial to aortic root diameter at end-systole (LA/Ao). In normal premature and full-term infants, Vcf (1.51 +/- 0.04 [mean +/- standard error]) was significantly lower than in infants with a large shunt (2.12 +/- 0.08, P less than 0.01) and higher than in infants with nonstructural heart disease (1.18 +/- 0.06, P less than 0.001). LA/Ao ratios were comparable in the groups with a large shunt and nonstructural heart disease (1.14 +/- 0.1 and 1.26 +/- 0.2, respectively) and were significantly higher in both groups than in normal subjects (0.77 +/- 0.01, P less than 0.001). Similar echocardiographic distinctions could be made when 10 older children (aged 2 to 10 years) with cardiomyopathy were compared with 45 normal older children. Serial determination of these variables was of major assistance in patient management.

Cardiomyopathies↗
PubMed1976

Cross-sectional echocardiographic localization of sites of left ventricular outflow tract obstruction.

Real time two-dimensional echocardiographic studies of left ventricular outflow tract cross-sectional anatomy were obtained by the multicrystal echocardiographic method (Bom system) in 35 patients with various types of outflow obstruction as delineated by clinical, hemodynamic and angiographic studies. In each patient the noninvasive test allowed prediction of the site of obstruction. In valvular aortic stenosis, echocardiographic diagnostic findings included poststenotic dilatation of the ascending aorta, thickened aortic cusp tissue and increased superior-inferior cusp excursion (doming). The site of supravalvular aortic stenosis was readily observed although echocardiographic findings often underestimated the degree of obstruction recorded at cardiac catheterization. In patients with discrete subvalvular aortic stenosis, the major finding was a localized thickening of the septum and anterior mitral anulus producing a narrowing of the left ventricular outflow tract that was present in diastole and persisted throughout the cardiac cycle.

Adolescent↗
PubMed1976

Age-dependent mechanical and biochemical responses to glucagon.

The age-dependent relationships between glucagon-induced alterations in myocardial mechanics and adenylate cyclase activity in fetal and newborn lambs and adult sheep were evaluated. Glucagon substantially augmented the force of contraction of ventricular myocardium isolated from the adult but not from the fetus or newborn. Similarly, substantial increases in the spontaneous frequency of contraction and tension were observed in adult atrial strips, but not in the fetus or newborn. Comparable activities of phosphodiesterase were observed in extracts from fetal and adult myocardium and were unaltered by the addition of glucagon. Adenylate cyclase activity in adult myocardial homogenate and particulate fractions was comparable to that of fetal tissue. Glucagon stimulation of the particulate fraction produced no change in fetal adenylate cyclase activity whereas a 43% increase in activity was observed in preparations from adult tissue. Sodium fluoride and epinephrine augmented adenylate cyclase activity in both fetal and adult myocardium. Thus, glucagon produced age-dependent, parallel changes in heart rate, active tension development, and particulate fraction adenylate cyclase activity, suggesting that these chronotropic and inotropic responses are indeed mediated by adenylate cyclase and that lack of response in the fetus reflects the absence of mature glucagon receptor sites.

Adenylyl Cyclases↗
PubMed1976

Distribution of fetal cardiac output: importance of pacemaker location.

Important questions exist about the relative roles of changes in heart rate versus extent of myocardial shortening in regulating fetal cardiac output, because increases in heart rate created by left atrial pacing have been shown to increase right ventricular output and decrease left ventricular output. Since the pacemaker site could importantly influence foramen ovale flow and, hence, each ventricle's output, changes in individual ventricular outputs were examined when both the right and left atria were paced at a rate of 270 beats/min in five acute and in eight chronically instrumented fetal lamb studies. With pacing of either atrium, total cardiac output was unchanged compared to control values. However, the right ventricle contributed more to total cardiac output with left atrial pacing (73% acute, 65% chronic) than with right atrial pacing (51% acute, 57% chronic). Converse changes were observed in left atrial pacing (27% acute, 35% chronic) as compared to right atrial pacing (49% acute, 43% chronic). Thus the disparity that exists normally in the contributions of the right and left ventricles to total cardiac output is accentuated with left atrial pacing and minimized with right atrial pacing. Pressure measurements demonstrated changes in the atrial pressure relations that would be expected to alter flow across the foramen ovale depending on the chamber initially activated. Previous experimental differences can, therefore, be attributed to changes in the magnitude of shunting across the foramen ovale and depend on pacemaker location.

Animals↗
PubMed1976

Frank-Starling relationship as an important determinant of fetal cardiac output.

The importance of the Frank-Starling mechanism was evaluated in seven chronically instrumented fetal lambs (128-141 days gestation). Continuous determinations of left ventricular (LV) internal dimensions and pressures were obtained while LV end-diastolic diameter (LVEDD) was reduced by superior vena cava occlusion and increased by infusion of fetal blood into left atrium. A highly significant relationship was found to exist between stroke volume and LV extent of shortening (delta D) (r = + 0.99, P less than 0.001). Altering LVEDD from 10,5 to 13mm or LV end-diastolic pressure from 2.5 to 8 mmHg resulted in a 68% augmentation, in delta D. Spontaneous respiratory efforts resulted in frequent beat-to-beat variations in LVEDD and delta D, which maintained cardiac output constant over a wide range of respiratory rates. Moreover, LV output determined by indicator-dilution techniques remained unchanged over a wide range of spontaneous heart rates (114-180 beats/min) as a result of changes in delta D appropriate to alterations in LVEDD. Thus, changes in resting myocardial fiber length are of fundamental importance in fetal cardiovascular homeostasis and, within physiologic limits, it is quite clear that the Frank-Starling mechanism is operative and effective in the fetal lamb;

Animals↗
PubMed1976

Indications for and results of surgery in congenital aortic stenosis.

All of the follow-up data indicate that aortic valvotomy is a safe and effective means of treatment. No instances of sudden death have been observed during the postoperative follow-up period. Of course, additional long-term studies of the results of surgery are indicated and it is certainly possible that the current criteria relating to indications for hemodynamic study and operation may well require modification in the future.

Adolescent↗
PubMed1976

Mitral valve prolapse in children: a problem defined by real-time cross-sectional echocardiography.

The cross-sectional echocardiographic features of mitral valve prolapse were defined in 26 children (ages 2-18 years) using a real-time, multiple-crystal ultrasound scanner. In each patient the physical findings of the mitral valve click-murmur syndrome were present and mitral valve prolapse had been diagnosed previously by conventional single crystal echocardiography. Mitral prolapse occurred in a familial setting in eight patients and was associated with the Marfan syndrome in five. Real-time two-dimensional echocardiography uniformly disclosed maximum mitral arching and the superior-posterior prolapse. These visual observations were confirmed by M-mode recordings derived from single elements within the array of 20 crystals. The method allowed a complete M-mode description of the phasic motion of the entire mitral apparatus and observations of the spectrum of prolapse from discrete late systolic prolapse to "hammock-like" holosystolic prolapse. Further, the recording of multiple systolic M-mode lines occurred when the ultrasound beam intersected the arched leaflets more than once. Pseudosystolic anterior motion was observed often and resulted clearly from a superimposition of echoes from the mitral annulus and from the posterior-superiorly arched prolapsed leaflets. A major finding in 22 patients was the association with prolapse of biconvex enlargement of the aortic sinuses of Valsalva and a significant increase in the diameter of the aortic root. Aortic root dilatation was most marked in, but not confined to, patients with the Marfan syndrome and was a prominent finding in six patients with minor musculoskeletal abnormalities. The presence of aortic root dilatation in children with normal body habitus raises important questions concerning the generalized nature of an abnormality of cardiac connective tissue in patients with mitral prolapse. The cross-sectional approach significantly enhances the noninvasive evaluation of mitral valve prolapse and provides an explanation for many of the single crystal observations reported previously.

Adolescent↗
PubMed1976

A comparison of the active stiffness of fetal and adult cardiac muscle.

This report described the in vitro analysis of the series elasticity of ventricular myocardium isolated from five fetal lambs and six adult sheep. Active compliance measurements were obtained by quick releases utilizing a closed loop servosystem and electromagnetic positioning device to control cardiac muscle length or tension. Right ventricular moderator bands were obtained from five fetuses (average 139 days of gestation, term=147 days), and compared with two adult moderator bands and four adult right ventricular trabeculae carneae. After correction for equipment coupling the experimental load extension data were fit to an exponential expression by a least squares technique: strain=1/b ln (1 + stress/a). When fetal and adult data were compared, no age-related differences in the constants were observed (a=0.185 +/- 0.062 SE (fetal) and 0.159 +/- 0.03 g/mm2 (adult); b=40.4 +/- 5.2 (fetal) and 43.1 +/- 5.2 (adult); and ab=7.39 +/-2.34 (fetal) and 5.27 +/- .99 (adult). However, significant variation existed in the histologically determined amount of contractile tissue present in muscle samples from both fetus (57-85%, average=74.0 +/- 4.9) and adult (64-94%, average=82.3 +/- 5.3). Wihtout regard to age, a signficant correlation was found between the b stiffness constant and the amount of contractile mass present in cardiac muscle. Thus, it is concluded that there is no age-related difference in the stiffness of fetal and adult ventricular muscle. However, there is a significant relationship between active compliance and true muscle mass.

Age Factors↗
PubMed1975

Echocardiographic recognition of ventricular septal aneurysm--a case report.

The noninvasive detection of an aneurysm of the interventricular septum may be predictive of spontaneous closure of a ventricular septal defect. Moreover, in patients with audible systolic clicks the distinction must be made between septal aneurysm and mitral valve prolapse. The current report describes the echocardiographic visualization and pattern of motion of an aneurysm of the membranous ventricular septum. The diagnosis was made by both single crystal and real-time cross-sectional, multiple crystal ultrasound techniques prior to catheterization. These findings from the basis of the present study.

Angiocardiography↗
PubMed1975

Factors influencing neurohumoral control of the heart in the newborn dog.

Several investigators have documented immaturity of cardiac autonomic innervation in neonates. To evaluate the integrity of afferent and efferent responses and to determine the role of circulating catecholamines in newborns, 50 puppies and 24 adult dogswere studied with the use of chloralose anesthesia. Interventions were: bilateralvagotomy, bilateral carotid occlusion, central vagus stimulation, stellate stimulation, bilateral adrenalectomy, infusion of norepinephrine or isoproterenol, and intravenoustyramine. Newborns exhibited supersensitivity to exogenous norepinephrine, isoproterenol, and stellate stimulation; responses to carotid occlusion and central vagal stimulation were comparable in both groups. Newborns had less resting vagal tone. After adrenalectomy, newborns exhibited a more marked decline in systemic pressureand heart compared to adults. Myocardial catecholamine content in newborns was 1/10 that in adults, whereas plasma catecholamine concentration in newborns was 30-fold greater than in adults. These data demonstrate functional integrity of afferent and efferent cardiac autonomic pathways in the newborn, define in vivo supersensitivity to the sympathetic neurotransmitter, and suggest a dominant role of circulating catecholamines in modulation of cardiovascular events in neonates.

Adrenal Glands↗
PubMed1975

Influence of poststimulation potentiation and heart rate on the fetal lamb heart.

Isolated cardiac muscle techniques and studies of the chronically instrumented fetal lamb heart were employed to evaluate the ability of fetal myocardium to exhibit poststimulation potentiation. Isometric tension development and the response to paired electrical stimulation were significantly reduced in isolated fetal ventricular myocardium when compared to the adult (P less than 0.001). As in the adult, increasing stimulation frequency raised fetal isometric tension via an increase in the rate of rise of tension development in the presence of reduction in time-to-peak tension. In seven fetal lambs the left ventricle was chronically instrumented with endocardial ultrasonic crystals and a high-fidelity micromanometer. After a 2-wk recovery period, heart rate was increased by atrial pacing from an average control level of 150 to 300 beats/min. Left ventricular dP/dt increased progressively and then fell beyond a heart rate of 270/min. When comparable pre- and immediate postpacing beats were analyzed, a step-wise increase in the velocity of left ventricular shortening and the mean rate of circumferential fiber shortening was observed in association with an increase in the extent of shortening. Thus, increases in the frequency of contraction exert a significant positive inotropic effect on the fetal heart.

Animals↗
PubMed1975

Catheter positions in congenital cardiac malformations.

Biplane cineangiocardiograms were examined from a population of patients with diverse forms of congenital heart disease and examples were selected to illustrate catheter positions which may help define and elucidate the anatomy of simple and complex cardiac lesions. Familiarity with the appearance of these typical and atypical catheter positions may be of considerable aid in the course of hemodynamic study and in the evaluation of cineangiocardiograms. The editors suggest that each figure be evaluated as an unknown before reading the caption.

Angiocardiography↗
PubMed1975

Prolonged Q-T interval syndrome. Successful treatment with combined ventricular pacing and propanolol.

A case of the sporadic variety of the prolonged Q-T interval syndrome without deafness is presented. The patient is unusual because of a long survival to age 13, despite progressive worsening of her disease, and the presence of marked atrioventricular conduction abnormalities in addition to the usual ventricular trachyarrhythmias. Successful therapy was finally achieved with a combination of permanent pervenous ventricular pacing and propranolol.

Adolescent↗
PubMed1975

In situ physiological study of the developing heart.

Studies on cardiac muscle and whole heart isolated from the fetal and newborn lamb and adult sheep reveal striking age-dependent differences in cardiac ultrastructure, passive and active length-tension properties, force-velocity relationships, the compliance characteristics of both ventricles, myocardial energetics, and in the development of myocardial autonomic control. Isometric force development and both the extent and velocity of shortening at any load are reduced in the fetus when compared with the adult because of age-related changes in the proportion of myocardial tissue consisting of myofilaments. The distensibility characteristics of both the left (LV) and right ventricles (RV) are comparable in the fetal lamb close to term. In the early newborn period the RV has compliance characteristics similar to the RV of the fetus, whereas the LV alters its stress-strain characteristics to resemble the adult. Most recently, methods have been developed for the chronic evaluation of fetal left ventricular function. Internal LV dimensions and pressures are monitored continuously from midgestation beyond delivery.

Age Factors↗