William Berman

Effect of patent ductus arteriosus on left ventricular output in premature infants

A 5 MHz range-gated portable pulsed Doppler velocity meter was used to measure mean ascending aortic blood flow velocity noninvasively. Studies were performed from a suprasternal approach in 18 preterm infants with patent ductus arteriosus. Measurements were made in each patient before and after medical or surgical closure of the PDA. The internal ascending aortic diameter was determined echocardiographically and aortic cross-sectional area calculated according to the equation AAo = pi d2/4. Ascending aortic blood flow was computed as QAo (ml/min) = VAo (cm/sec) x AAo (cm2) x 60 (sec/min). Prior to PDA closure, QAo averaged 343 ml/min/kg, well above predicted normal values. After PDA closure, QAo fell to 252 ml/min/kg, significantly lower than the preclosure level (P less than 0.001), but slightly higher than the mean cardiac output of healthy newborn infants. The mean QAo after surgical ligation of the PDA was closer to the predicted normal value than after treatment with indomethacin alone. This study reflects the effect of left-to-right ductus shunting on left ventricular output and emphasizes the demands placed on the neonatal left ventricle by PDA.

Long-term follow-up of bronchopulmonary dysplasia

We observed 10 children with bronchopulmonary dysplasia, evaluated initially by cardiac catheterization (mean age 18 months), for an average of 4.4 years. Age at last evaluation averaged 5.8 years; subjects reside in and around Albuquerque, N.M. (altitude 5000 ft). At initial cardiac catheterization, mean pulmonary artery pressure was 40 mm Hg, pulmonary vascular resistance index 8.9 units, and intrapulmonary shunt fraction was high; pulmonary wedge angiograms were normal. Over the period of follow-up the group has done poorly. Four of the 10 continue to receive home oxygen therapy, but none requires inotropic or diuretic therapy; four children have marked developmental or motor delays. Nine of 10 patients have abnormalities of respiratory function on spirometric testing. Four patients underwent recatheterization because of clinical indications; two had large atrial level left-to-right shunts not found on initial study. Reductions in pulmonary artery pressure (55 to 37 mm Hg) and pulmonary vascular resistance (11.9 to 7.8 units) occurred between the two studies in these four patients (average study interval 4.0 years); the still elevated levels of pressure and resistance fell further in response to 40% O2 administration. Pulmonary wedge angiograms were abnormal in each restudied patient. Although not uniformly bleak, the long-term outlook for children with severe bronchopulmonary dysplasia is diverse and guarded.

Effects of Acute Preload and Afterload Stress on Myocardial Function in Newborn and Adult Sheep

Unanesthetized, chronically instrumented newborn and adult sheep were subjected to acute circulatory preload stress (rapid administration of 30 ml X kg-1 isotonic saline) and afterload stress (intravenous administration of 0.2 mg X kg-1 methoxamine). Variables of circulatory status and myocardial function were monitored continuously during experimental manipulations. Preload stress elevated arterial and venous pressures, reduced the preejection period (PEP) to left ventricular ejection time (LVET) ratio (PEP/LVET), and increased the rate of left ventricular pressure rise (dp/dt) to a comparable extent in newborn and adult subjects. Afterload stress increased arterial and venous pressures to a comparable extent in newborns and adults; the percent changes in PEP (25), LVET (16), PEP/LVET (12) and dp/dt (-21) in newborns were more pronounced than those in adults.

Electrophysiologic effects of propranolol on sinus node function in children.

Little is known regarding the effects of propranolol (P) on sinus node function in children. In this study, corrected sinus node recovery time (CSNRT) and estimated sinoatrial conduction time (SACT) were measured in 10 children (ages 3 to 16 years; mean 8.3 years) without clinical evidence of sinus node dysfunction before and after intravenous P. The spontaneous sinus cycle length (SCL) increased after P(0.1 mg/kg) in all patients. Mean SCL increased 13.4% from 635 +/- 200 msec (+/- SD) to 720 +/- 202 msec (p less than 0.01). Maximum CSNRT increased in nine patients after P and mean CSNRT increased 63% from 203 +/- 61 msec to 330 +/- 190 msec (p less than 0.05). SACT changed in a random fashion after P. Mean SACT did not change significantly. We conclude that P significantly suppresses sinus node automaticity in children with normal sinus node function but has little or no effect on sinoatrial conduction.

Communicating Hydrocephalus: A Reversible Complication of the Mustard Operation with Serial Hemodynamics and Long-term Follow-up

Severe superior vena caval (SVC) obstruction following the Mustard operation resulted in substantially increased intracranial pressure in 3 patients. A pathophysiological mechanism is postulated to explain the cerebral edema in 1 and the communicating hydrocephalus in 2. Following surgical relief of the obstruction in the latter 2, there was a decrease in both the rate of head growth and the ventricular size. It is of note that despite the angiographic appearance of azygous decompression, the pressure elevation from the SVC obstruction was transmitted to the brain. The long-term follow-up at three and four years of the 2 infants with communicating hydrocephalus suggests that aggressive treatment is compatible with a favorable outcome.

The pharmacokinetics of digoxin in newborn and adult sheep

The pharmacokinetics of digoxin were determined in 12 ewes and 13 newborn sheep after bolus drug administration and under steady state drug conditions. After death, tissue distribution of digoxin was determined and normalized to plasma drug concentrations at steady state. Volume of distribution and total drug clearance were lower at steady state than the comparable variables calculated from bolus drug administration. No significant difference between ewes and newborns was shown for drug distribution half-life (0.72 vs. 0.76 hr), drug elimination halflife (15.2 vs. 13.7), or renal drug clearance (0.86 vs. 0.89 liters/kg/hr). Total drug clearance as well as the area derived and steady state volumes of distribution were higher in newborns than in ewes. Digoxin secretion into the urine was limited in newborns, as evidenced by a lower renal digoxin clearance to creatinine clearance ratio in newborns than in ewes (371 vs. 600%). The plasma concentration of digoxin at steady state correlated well with myocardial drug concentrations. Drug distribution was similar in both age groups; however, the tissue to plasma digoxin ratio in kidney was higher in newborns than in ewes (mean 469 vs. 263, respectively). Although agerelated differences in drug clearance and distribution volume existed, intersubject variation was substantial, and the demonstrated variations were not large enough to account for the high doses of digoxin used to treat congestive heart failure in immature subjects.

Late-Onset Pulmonary Venous Pathway Obstruction After Fontan Operation: Presentation Masquerading as Intra-Atrial Baffle Leakage

Fontan type operations are described as palliative because of a progressive decrease in survival with increased length of follow-up [1, 3, 5]. Initial survival rates are dependent on patient selection and vary from 77% to 92%; survival rates at 5, 10, and 15 years after surgery are lower—as low as 60% in the report of Driscoll et al. [1]. Late deaths (>1 year after surgery) are well documented and most often reflect progressive myocardial failure. Pulmonary venous pathway obstruction is an uncommon, sometimes fatal, late-onset problem after Fontan-type surgery [2]. We describe two patients with delayed-onset pulmonary venous pathway obstruction after modified Fontan surgery. In each case transthoracic echocardiographic Doppler studies suggested an intraatrial baffle leak. In the first case, this spurious finding delayed correct diagnosis and complicated patient management.

Assessment of hemodynamic function with pulsed doppler ultrasound

Recent refinements in pulsed Doppler technology have made possible the noninvasive assessment of hemodynamic function. The application of the Doppler frequency shift principle to study discrete velocity events at a measured distance from the transducer is discussed. The accuracy and limitations of Doppler techniques in determining ascending aortic and peripheral blood flow velocities in infants with various cardiac lesions are examined. Noninvasive assessment of myocardial contractility is also described. Most studies performed to date suggest that pulsed Doppler techniques provide a sensitive approach to the measurement of flow velocity and acceleration in appropriate selected circumstances. However, distinctions between volume flow and flow velocity must be considered in the interpretation of data.

Right ventricular contractile function in children with congenital heart disease

Indexes of right ventricular (RV) systolic function were evaluated in 41 patients undergoing cardiac catheterization. High-fidelity tracings were used to determine RV pressure, maximal RV dP/dt and the velocity of contractile element shortening at a developed pressure of 10 mm Hg (VCE10). In 14 children with an RV systolic pressure less than 35 mm Hg, normal RV volume, pulmonary vascular resistance (PVR) less than 3 units X m2 and no shunts (our normal group), mean (+/- standard deviation) RV dP/dt was 437 +/- 116 mm Hg X s-1 and VCE10 was 1.15 +/- 0.33 muscle length X s-1. In patients with RV systolic hypertension due to valvular pulmonary stenosis or isolated increases in PVR, mean values for RV dP/dt and VCE10 were significantly (p less than 0.05) greater than the normal values. In patients with a ventricular septal defect, RV hypertension and normal PVR, VCE10 was normal but RV dP/dt was significantly elevated. Children with chronic RV volume overload had normal RV contractile indexes. No patient in any group had values for RV dP/dt or VCE10 that were less than normal (mean normal - 2 standard deviations). This study establishes for the first time the indexes of RV isovolumic systole in children. It also shows that RV contractile function is preserved in young patients with chronic RV pressure or volume overload who do not have overt congestive heart failure.

Medical management of three asymptomatic infants with severe valvar Aortic stenosis

SummaryWe report on the clinical course and serial hemodynamic studies of three patients with severe valvar aortic stenosis diagnosed in the neonatal period. None of the children were symptomatic in the first year of life. In each case, a conservative initial management approach was adopted. Between the time of initial study (mean age, 1.8 months) and the follow-up at 12–27 months of age (mean, 14.3 months), mean left ventricular systolic pressure decreased from 151 to 125 mmHg, the mean peak systolic pressure gradient across the aortic valve decreased from 61 to 33 mmHg, and the mean calculated aortic valve area index increased from 0.24 to 0.60 cm2/m2. One patient was operated on for symptoms that appeared at 14 months of age. The patient followed longest is now 5 years old, is growing well, has a normal electrocardiogram and an echo-predicted left ventricular systolic pressure of 128 mmHg. This experience suggests that not all asymptomatic neonates with severe valvar aortic stenosis require surgical intervention early in life. In some, the aortic valve orifice may increase in size with somatic growth and obviate the need for surgery in infancy or early childhood.