Premature "closing" of the foramen ovale in transposition of the great arteries with intact ventricular septum: rare cause of sudden neonatal death.

We report a male neonate who developed severe cyanosis and bradycardia at birth unresponsive to resuscitation. At autopsy he was found to have premature "closure" of the foramen ovale together with transposition of the great arteries and an intact ventricular septum. Reviewing the literature, we found only one case report describing a similar neonate with this lethal combination of cardiac malformations.

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.

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.

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.

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.

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.

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.

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.

Ventricular and pulmonary artery volumes in patients with absent pulmonary valve. Factors affecting the natural course.

Right and left ventricular (RV and LV) volumes were determined in 19 patients with absent pulmonary valve syndrome using Simpson's rule and area-length methods. The volume of the proximal right pulmonary artery (RPAV) was calculated at maximal and minimal size using the area-length method. Patient groups included four newborns who responded to medical management (group 1A), seven critically ill newborns who died (group 1B), four infants ages 1-10 months (group 2) and four children ages 2-8 years (group 3). The RV end-diastolic volume in groups 1B and 2 was significantly greater than that in groups 1A and 3. The RV ejection fraction in groups 1B and 2 was significantly less than that in normal patients and groups 1A and 3. Maximal RPAV correlated well with RV stroke volume and end-diastolic volume. The maximal RPAV in group 1B was significantly greater than that in groups 1A and 3. Pulmonary arterial compliance was greater than normal in all groups, and the compliance in group 1B was more than two times that in the other groups. We conclude that the increased right pulmonary artery compliance and pulmonary regurgitation in patients with absent pulmonary valve contribute to bronchial obstruction and right-heart failure and are the causes of the high morbidity and mortality in these patients. The management should be directed to the alleviation of bronchial obstruction and right-heart failure.

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.

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.

Pulmonary arterial hypertension induced by distention of the main pulmonary artery in conscious newborn, young, and adult sheep.

Distention of the main pulmonary artery by balloon inflation in sheep results in presumably reflex elevation of pulmonary arterial pressure and resistance distal to the balloon. This response to main pulmonary artery distention is significantly greater in newborn lambs than in older lambs or adult sheep. In several of the newborn lambs, pulmonary artery pressure was raised to suprasystemic levels. Further, in some of the newborn animals, these increases in pulmonary artery pressure and resistance were sustained after deflation of teh balloon for periods up to 2 hr. The functional significance of this pulmonary hypertension reflex was not elucidated. However, the data strongly suggest that this reflex may contribute to the maintenance of high pulmonary vascular resistance during fetal and early neonatal life.

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.

Morphologic evidence of accelerated closure of the ductus arteriosus in preterm infants.

In preterm infants, closure of the ductus arteriosus (DA) is often delayed, especially in those with respiratory distress syndrome (RDS). However, it has been suggested that functional closure of the DA may occur as early as 24 hours of age in some preterm infants exposed to intrauterine stress, and this is usually associated with decreased incidence of RDS. This suggests that accelerated maturation of the DA as well as of the lungs occurs in utero. Accordingly, histologic evidence of accelerated maturation of the DA was sought in a prospective autopsy study of 55 preterm infants ranging in gestational age from 19 to 32 weeks. There were four infants with clinically closed DA which showed histologic evidence of closure. The birth weight of these four infants ranged from 750--1,100 gm, the gestational age ranged from 24--32 weeks, and age of death was 39 hours to 6 days. The immediate causes of death were intracerebral hemorrhage or intrapulmonary hemorrhage, or both. Obstetric complications included chronic second trimester vaginal bleeding, abruptio placenta, malnutrition, diabetes, pulmonic stenosis of moderate degree, and chronic hypertension. These findings support the hypothesis that in some preterm infants exposed to chronic intrauterine stress, maturation of the DA is accelerated. This may result clinically in effective postnatal closure of the DA.

Main pulmonary artery distention: a potential mechanism for acute pulmonary hypertension in the human newborn infant.

Balloon-induced distention of the main pulmonary artery causes acute pulmonary hypertension and reflex pulmonary vasoconstriction in animals. Pulmonary artery pressure responses caused by MPA balloon inflation were measured in ten human newborn infants with cardiac failure (n = 5) or persistent fetal circulation (n = 5). During balloon inflation distal mean PAP increased significantly while cardiac rate remained unchanged. MPA distention caused greater increases of PAP in those infants with lower resting PAP. The greatest balloon-induced increases of PAP were observed in infants recovering from PFC. The existence of a pulmonary artery reflex and its possible role in the regulation of the human fetal and neonatal pulmonary circulation is discussed.

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.