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Biomedical subjects

B G Baylen

Publications and source records attributed to B G Baylen.

At least 37 records · Page 2Linked to original sources
PubMed1992

Role of balloon atrial septostomy before early arterial switch repair of transposition of the great arteries.

Preoperative balloon atrial septostomy is the standard therapy for babies with uncomplicated cyanotic dextrotransposition of the great arteries despite the effectiveness of prostaglandin E1 infusion in alleviating systemic hypoxemia and the reported success of arterial switch repair during the 1st weeks after birth. The clinical records and echocardiographic findings of 23 infants (mean birth weight +/- SD 3.3 +/- 0.5 kg) with uncomplicated transposition of the great arteries were analyzed. Fifteen infants (Group I) did not undergo septostomy, and 8 (Group II) underwent septostomy. Before prostaglandin infusion, mean arterial oxygen tension (Po2) in Group I (26 mm Hg) did not differ from that in Group II. After prostaglandin infusion, Po2 increased significantly in Group I (43 +/- 8 mm Hg, p less than 0.001) but not in Group II despite a widely patent ductus and predominant left to right ductal shunt in all. After septostomy, Po2 increased significantly (43 +/- 4 mm Hg, p less than 0.03), and did not differ from that in Group I. Echocardiographic features generally demonstrated a nonrestrictive foramen ovale in Group I and a restrictive foramen ovale in Group II. The latter was associated with persistent hypoxemia after prostaglandin. Thus, the diameter of the foramen ovale was the primary factor influencing arterial oxygenation during prostaglandin infusion. Babies underwent the arterial switch operation at a mean age of 70 +/- 65 h with an overall survival rate of 96%; there was only one postoperative death (Group II). Absence of septostomy had no negative influence on any postoperative variable, including duration of ventilatory and inotropic support, time to discharge, or mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheterization↗
PubMed1991

End-to-end repair of aortic coarctation using absorbable polydioxanone suture.

Based on previous laboratory work, we have used polydioxanone absorbable suture in a variety of vascular and cardiac repairs in pediatric patients. However, some investigators have expressed concern about the potential for aneurysm formation at the anastomotic site. Between March 1983 and June 1989, 15 patients (7 male, 8 female) aged 2.5 months to 9.2 years (mean, 3.7 years) had resection of coarctation of the aorta and end-to-end anastomosis with polydioxanone absorbable suture. Thirteen patients have returned for routine postoperative evaluation, the follow-up time ranging from 11 to 49 months (mean, 23 months). Noninvasive two-dimensional, pulsed-wave Doppler and color echocardiography and magnetic resonance imaging studies demonstrated good anatomical repair and no anastomotic aneurysm formation or residual coarctation of the aorta in any patient after end-to-end anastomosis with polydioxanone. In summary, this intermediate follow-up study has revealed no vascular complications related to the repair of coarctation with absorbable polydioxanone suture.

Abnormalities, Multiple↗
PubMed1990

Pharmacokinetics of dopamine in critically ill newborn infants.

Dopamine pharmacokinetics was investigated in 14 critically ill newborn infants ranging from 27 to 43 weeks of gestational age and from 0.9 to greater than 4 kg birth weight. Plasma clearance rate was determined from dopamine levels during controlled infusions under actual clinical conditions. Dopamine was administered in stepwise increasing doses up to 8 micrograms/kg/min. Dopamine concentration and dopamine clearance rate were determined from duplicate samples drawn during each infusion in each patient. Steady-state plasma dopamine concentrations and plasma clearance rates were observed within 20 minutes at each infusion. Plasma dopamine concentration ranged from 0.5 ng/ml before infusion to almost 70 ng/ml at an infusion rate of 4 to 8 micrograms/kg/min. There was a linear correlation between infusion rate and plasma dopamine concentration (r = 0.68, p less than 0.001). Neither plasma dopamine concentration nor infusion rate had a significant effect on clearance rate. These data are consistent with first-order kinetics for administered dopamine in critically ill neonates over the range of concentrations studied.

Birth Weight↗
PubMed1990

A reconsideration of risk factors for the Fontan operation.

We reviewed our experience in 38 patients who underwent a Fontan operation. In the first five patients ages 7.5 to 23 years (mean, 15 years), a conduit was placed from the right atrium to the small right ventricle or the pulmonary artery (PA). The remaining 33 patients, ages 7 months to 14 years (mean, 4.8 years), had a modified Fontan operation with direct systemic venous or right atrial to PA anastomosis. The diagnoses were tricuspid atresia (n = 14), single ventricle (n = 10), hypoplastic right or left ventricle (n = 9), double-outlet right ventricle with inlet ventricular septal defect and pulmonary atresia or stenosis (n = 3), criss-cross ventricles and transposition of the great arteries (n = 1), and atrioventricular canal and anomalous pulmonary venous connection (n = 1). Thirty-two patients had previous surgery. Other procedures included PA banding (n = 7), systemic to PA shunts (n = 25), Norwood operation (n = 3), and a Damus-Kaye-Stansel anastomosis (n = 1), repair of total anomolous pulmonary venous connection (n = 1), a Blalock-Hanlon atrial septectomy (n = 1), and enlargement of a restrictive ventricular septal defect (n = 1). There were four operative deaths (10.5%), three from low cardiac output and one from subaortic obstruction. There were no deaths in patients younger than 3 years of age (n = 13). Subaortic obstruction developed in six of the seven patients who had pulmonary artery banding and resulted in three deaths. In our experience, diagnosis, previous surgery, type of previous operation, PA pressure, and younger age are not risk factors for early or late death. Subaortic obstruction is a major risk factor for late death. Accordingly we now perform a Damus-Kaye-Stansel anastomosis combined with a systemic to PA shunt in those children with excessive pulmonary blood flow who anatomically are likely to develop subaortic obstruction. A modified Fontan operation can be performed any time after 1 year of age and in some patients after 6 months of age, providing the anatomy and physiology of the patient are acceptable.

Adolescent↗
PubMed1989

Hemodynamic and neuroendocrine adaptations of the preterm lamb left ventricle to acutely increased afterload.

The birth process is associated with dramatic alterations of left ventricular (LV) volume loading, pressure loading, and contractile state. The preterm LV has considerable volume loading reserve. We have assessed neuroendocrine and related hemodynamic responses of the preterm lamb LV at 0.8 gestation during acute pressure loading within the first 2-4 h after birth. We measured plasma catecholamines and hemodynamic and cineangiocardiographic parameters of LV pump performance and contractility at basal levels and during rapid LV pressure loading by partial balloon obstruction of the ascending aorta before and after propranolol. A relatively high level of propranolol (3 mg/kg) was required to produce beta-adrenoceptor blockade associated with reduction of heart rate and blood pressure, but after atrial pacing there was no detectable difference of basal LV pump performance or contractility at comparable heart rate, preload, and afterload. The LV pump performance was maintained and plasma catecholamines and LV contractility were increased when aortic systolic pressure was augmented 60% over baseline. The increased contractile state at greater afterload was minimally blunted by propranolol. Thus the preterm LV is relatively hypercontractile soon after birth and is capable of an integrated augmentation of pump performance and contractile state during pressure loading. These findings are relevant to the maintenance of adequate LV performance and successful adaptation to the acute alterations of afterload associated with the transitional circulation at birth.

Animals↗
PubMed1988

Surgical management of coronary insufficiency in a child with Kawasaki's disease: use of bilateral internal mammary arteries.

Coronary insufficiency is an important sequela of Kawasaki's disease. Successful myocardial revascularization with saphenous vein grafts and, more recently, with internal mammary artery grafts has been performed. We report a case of Kawasaki's disease with chronic coronary insufficiency in which complete myocardial revascularization was accomplished using bilateral internal mammary arteries, and we present a review of the literature.

Child↗
PubMed1987

Dopamine pharmacokinetics in critically ill newborn infants.

To compare clinical responses with plasma concentrations of dopamine and to compare dopamine pharmacokinetics in infants of different gestational age or clinical condition, dopamine was administered under carefully controlled conditions of dose and rate of infusion. The dose was increased stepwise from 1 to 2, to 2 to 4, and 4 to 8 micrograms/kg/min. Plasma concentrations of catecholamines, including dopamine, were compared with blood pressure, heart rate, and Doppler cardiac output. The data were analyzed to determine the threshold or minimal plasma concentration of dopamine necessary to produce discernible effects. Plasma clearance rate was calculated from steady-state plasma concentrations. The average threshold for increases in mean arterial pressure was 50% below that for increases in heart rate. Improvements in arterial pressure were noted before and at lower thresholds than for increases in heart rate. Serial echocardiographic data showed dose-dependent increases in cardiac output and stroke volume without significant change in heart rate or systemic vascular resistance. Thresholds and plasma clearance values were similar in infants of gestational age 27 to 42 weeks and birth weights 900 to 4300 g. Administration of dopamine at initial dosages lower than commonly recommended, followed by incremental increase in dose, may be associated with improved left ventricular performance with avoidance of undesirable tachycardia and arrhythmias.

Dopamine↗
PubMed1986

Hemodynamic effects of high frequency ventilation in surfactant-treated preterm lambs.

We compared the hemodynamic status and left ventricular (LV) performance in 7 twin pairs of preterm lambs delivered at 124 days gestational age (83% of term gestation) and ventilated by either conventional ventilation (CV) or high frequency ventilation (HFV) at 15 Hz. The lambs were treated with suspensions of natural sheep surfactant to permit ventilation and survival, and ventilatory settings were adjusted to maintain physiologic blood gas values. The ductus arteriosus was occluded with a balloon catheter at 40-45 min of age to eliminate the variable of a left to right ductal shunt. Cineangiocardiographic, pressure, and blood flow measurements were made 1 and 2 h after ductal occlusion. At the same mean airway pressures, the heart rates, LV end-diastolic volumes, and mean arterial pressures were similar in both groups. LV stroke volumes, ejection fractions, LV outputs, and organ blood flows also did not differ between the two groups. When compared with CV, HFV provides comparable ventilation with no apparent deleterious hemodynamic effects in preterm surfactant-treated lambs with occluded ductus arteriosus.

Acid-Base Equilibrium↗
PubMed1986

Left ventricular performance and contractility before and after volume infusion: a comparative study of preterm and full-term newborn lambs.

We studied left ventricular performance and contractility after volume loading in lambs at 122 days (group I, n = 9) and 139 days gestational age (group II, n = 9) and in 8-day-old full-term lambs (group III, n = 7). All were mechanically ventilated; each preterm lamb was treated with surfactant to stabilize pulmonary function and the ductus arteriosus was occluded with an inflated catheter balloon. Cineangiograms, left ventricular and vascular pressures, and the isovolumetric index of contractility, first derivative of left ventricular pressure (dP/dt), were recorded before and after three successive whole blood volume infusions of 10 ml/kg (total 30 ml/kg). The left ventricular end-diastolic volume per kilogram and stroke volume per kilogram increased significantly in all groups after volume infusion; these measurements and heart rate and systemic vascular resistance did not differ significantly between the groups either before or after the infusions. The left ventricular peak dP/dt did not change significantly within the groups during the volume infusions. The left ventricular stroke work was greatest in full-term animals and increased significantly in all groups after volume infusion. Thus, the left ventricles of the preterm and full-term lambs had quantitatively similar Frank-Starling responses and there was no increase in contractility during the infusions of whole blood. However, the left ventricle of the full-term lamb is capable of generating greater stroke work than that of the preterm lamb. These findings may contribute to the understanding of development aspects of postnatal circulatory adaptation.

Animals↗
PubMed1985

The contractility and performance of the preterm left ventricle before and after early patent ductus arteriosus occlusion in surfactant-treated lambs.

The influence of left-right ductal shunting on early hemodynamic responses, namely left ventricular performance, contractility, and systemic perfusion was evaluated in nine preterm lambs (120 days gestational age) treated with surfactant. Blood gases were maintained in the physiological range using mechanical ventilation; hemodynamic and blood flow measurements (radionuclide labeled microspheres) were obtained before and after occlusion of the patent ductus arteriosus with a catheter balloon. The mean left-right ductal shunt before occlusion (1.2 h postnatal age) was 59 +/- 11% SD. Left ventricular output was increased in all lambs with PDA (pre: 306 +/- 106 versus post: 155 +/- 31 ml/min/kg; p less than 0.001); effective systemic blood flow and organ blood flows did not change. The left ventricle end-diastolic volume was increased in all and decreased following ductal occlusion (pre: 2.0 +/- 0.4 versus post: 1.5 +/- 0.2 ml/kg; p less than 0.01). Cardiac rate, ejection fraction, and contractility (peak dP/dt) did not change. Right-left ductal shunting was not detected in six similarly treated lambs. Thus, during the 1st h of life the hemodynamic profile of preterm lambs with patent ductus arteriosus was characterized by large magnitude left-right shunt and a "high" cardiac output state sufficient to maintain unchanged systemic perfusion. The increased left ventricle output was accomplished by increasing end-diastolic volume (Frank-Starling mechanism), but left ventricle contractility remained unchanged. We speculate that the preterm left ventricle may be unable to sustain the high level of pump performance and contractility required to compensate for the ductal "steal" of systemic blood flow.

Animals↗
PubMed1984

Accurate internal correction for the magnification of cineangiocardiography in infants with congenital heart disease.

Correction for x-ray magnification at cineangiocardiography (cine) requires accurate localization of the level of the left ventricle (LV). This study compared LV volumes calculated using a standard external reference object (area grid) with volumes calculated using an intracardiac radiopaque catheter balloon in cine studies of casts (n = 26), normal lambs (n = 15), and infants with congenital heart disease (n = 11). Comparisons of LV volumes calculated using both correction methods with true cast displacement volumes were excellent (r = 0.99). Correlations of both methods were highly significant (p less than 0.001) in casts (r = 0.99), normal lambs (r = 0.97), and in infants (r = 0.83). The absolute percent difference (17.6 +/- 2.4 SE%) between LV volumes calculated by both methods was greatest in infants. Thus external localization of the LV may be more difficult in infants. The radiopaque balloon provides convenient accurate correction for cine x-ray magnification and calculation of LV volumes, particularly since flow-directed catheters are widely used for diagnostic cine ventriculography in infants.

Animals↗
PubMed1983

Ventricular systolic time intervals by simultaneous echocardiographic recording of the semilunar valves during the first days of life: a study of normal newborn infants.

A modified ultrasonic method was used to image simultaneously the semilunar valves in order to study comparative neonatal right and left ventricular systolic time intervals (STI) and phasic respiration. We obtained 72 serial M-mode echocardiograms from 24 normal term infants during the first 3 days of life. Right and left ventricular pre-ejection period (RPEP, LPEP), ejection times (RVET, LVET), and STI ratios (RPEP/RVET, LPEP/LVET) did not vary with respiratory variation during the first days of life; aortic (Q-Ac) and pulmonic valve (Q-Pc) closure intervals were uninfluenced by respiration. Widening of Ac-Pc interval beyond 15 msec was present in 56% by day 3. The RPEP/LVET was greater than LPEP/LVET on the first day--a finding previously described in infants with dextro-transposition of the great arteries. Relatively fixed duration of right ventricular systole (Q-Pc) and the absence of inspiratory widening of the Ac-Pc interval, despite decreasing pulmonary vascular resistance, may be related to differences of right ventricular compliance and pulmonary vascular capacitance in the newborn infant.

Aortic Valve↗
PubMed1983

Left ventricular performance and regional blood flows before and after ductus arteriosus occlusion in premature lambs treated with surfactant.

The hemodynamic consequences of patent ductus arteriosus (PDA) were studied during the first few hours of life (1.9 +/- 0.7 hours) in 13 mechanically ventilated, surfactant-treated, preterm lambs (gestational age of 120-124 days). Cardiovascular pressures, left ventricular (LV) performance and regional blood flows were measured using cine left ventriculography and radionuclide-labeled microspheres before and after occlusion of the PDA with a catheter balloon. Before occlusion, the left-to-right shunt was 44 +/- 13%; after occlusion the shunt was negligible (2%). Heart rate (164 +/- 17 beats/min), LV end-diastolic pressure (5 +/- 3 mm Hg), ejection fraction (74 +/- 8%) and cardiac output (241 +/- 13 ml . min-1 . kg-1) were normal and did not change after ductus occlusion. However, "effective" systemic blood flow increased significantly after occlusion (130 +/- 53 vs 228 +/- 93 ml . min-1 . kg-1, p less than 0.001), as did blood flow to organs such as the brain, myocardium and gastrointestinal tract. The reduction of systemic blood flow in the presence of a left-to-right PDA shunt may be responsible for many early pathologic manifestations of the PDA "syndrome" of prematurity even in the absence of overt LV dysfunction.

Animals↗
PubMed1982

Precordial contrast echocardiographic detection of patent ductus arteriosus in small preterm infants.

Clinical detection of patent ductus arteriosus (PDA) remains an important and challenging problem in the small preterm infant with respiratory distress. In this study, PDA was diagnosed in 28 small preterms using an improved contrast echocardiographic method. In these infants, the injection of saline into the aorta generated echoes which were imaged at the pulmonary valve. This was accomplished using a conventional M-mode ultrasound transducer applied at the usual precordial position. Contrast echo studies were compared with the degree of ductal patency shown by single film aortography. Ductal patency was detected by contrast echo in 29 of 31 instances of aortographically proven PDA. Indirect echo indices commonly used for detection of PDA (cardiac chamber enlargement) may be limited since factors other than left-to-right shunt can cause cardiac enlargement in distressed small preterms. This direct contrast echo technique is an easily performed, sensitive, qualitative method for confirmation of the diagnosis of PDA in small preterm infants.

Aortography↗
PubMed1981

Structural congenital heart disease in the newborn. Its differentiation from nonstructural cardiac or pulmonary disease.

This article discusses structural congenital heart disease in the newborn. Emphasis is given to the clinical and laboratory diagnosis including the indication for cardiac catheterization and angiography. The discussion includes the group of cyanotic, noncyanotic and other structural congenital heart diseases, as well as the group of neonatal cardiopulmonary distress without structural heart disease. An outline of the general management of these entities is included in the presentation.

Angiocardiography↗
PubMed1980

Anomalous origin of the left coronary artery from the pulmonary artery: a case report with remarkable improvement of myocardial function following subclavian artery-coronary artery anastomosis.

A 3 2/12-year-old boy with anomalous origin of the left coronary artery from the pulmonary artery was successfully treated by anastomosis of the left subclavian artery to the anomalous vessel. A remarkable improvement in left ventricular function and electrocardiogram has occurred postoperatively. This case report supports the postulation that chronically hypoperfused, electrically silent, and minimally contractile myocardial tissue may acquire its electrical activity and function with the establishment of adeqate coronary perfusion.

Cardiopulmonary Bypass↗
PubMed1980

Improved echocardiographic evaluation of the closed-chest canine: methods and anatomic observations.

This report describes an improved and convenient method of obtaining echocardiograms from the precordial surface of the closed-chest conscious dog. All major cardiac structures were identified using contrast echocardiography. Anatomic relations and the orientation of cardiac structures to the ultrasound transducer in the position of study were established by postmortem examinations. Good quality echocardiograms were obtained from nine of 11 conscious dogs. Highly significant correlations were found when comparing left ventricular systolic time intervals measured from simultaneous echo and pressure recordings. This method has advantages over other echo techniques; namely, elimination of surgical intervention, displacement of interfering lung tissue, and wider field available for study with a minimum of reverberation artifact. The ability to obtain echocardiograms from the chronic experimental dog under physiologic conditioins might provide new and improved applications of echocardiography for the evaluation of human cardiac disorders.

Animals↗