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The effects of verapamil, a slow channel blocker and a potent antiarrhythmic drug, on retrograde V-A conduction were investigated following diagnostic cardiac catheterization in 12 children premedicated with lytic cocktail. Surface EKG, intra-atrial and His bundle electrograms, as well as right ventricular pacing with use of extra stimulus technique were obtained before and after a single intravenous dose of verapamil (0.15 mg/Kg, max 5 mg). Verapamil prolonged the AH interval in 9/12 and abolished or prolonged the retrograde V-A conduction whenever present (abolition in 5/12 and prolongation in 1/12). The duration of retrograde V-A conduction exceeded the antegrade conduction time in all. It is concluded that verapamil abolishes retrograde V-A conduction whenever present and this phenomenon may further explain the antiarrhythmic effects of the drug on retrograde conduction dependent (reentrant) arrhythmias.

Right atrial A-wave, mean and inspiratory pressures were measured serially every 6 h in 36 preterm infants--24 healthy and 12 with respiratory distress syndrome (RDS)--from the 2nd until 24th h of age. In healthy preterm infants, the right atrial A-wave averaged + 4.91 mm Hg with a range of + 2 and + 8 mm Hg and the right atrial mean pressure averaged + 1.62 with a range of -3 to + 4 mm Hg. Preterm infants developed RDS had significantly lower right atrial pressure (RAP) during the first 6 h of life than healthy preterm infants. RAP in preterm infants with RDS subsequently increased to normal range. RAP did not have any correlation with either birth weight or gestational age.

Forty-one children with advanced chronic rheumatic disease of the mitral valve had preoperative and postoperative hemodynamic studies. Twenty-three cases had open mitral commissurotomy, and 20 had mitral valvular replacement. After surgery the average pulmonary arterial systolic pressure in the group with valve replacement decreased from 78 to 42 mm Hg, the pulmonary vascular resistance decreased from 974 to 313 dynes sec cm 5, and the cardiac index rose from 2.29 to 4.15 L/min sq m. In the group with mitral commissurotomy, the average pulmonary arterial systolic pressure decreased from 90 to 63 mm Hg, the pulmonary vascular resistance decreased from 1,201 to 616 dynes sec cm-5, and the cardiac index rose from 2.5 to 3.5 L/min sq m. While all patients with mitral valve replacement showed a drop in pulmonary arterial pressure, the postoperative pressures were higher after commissurotomy in four patients, two of whom required a second operation of valve replacement. The study shows that in children, even severe degrees of pulmonary hypertension secondary to mitral valve abnormality is corrected.

The Frank vectorcardiogram (VCG) and the electrocardiogram (ECG) were used to predict pulmonary arterial pressures in 30 pediatric patients with rheumatic mitral valve disease. The patients' ages ranged from eight to 14 1/2 years. Eleven were male and 19 were female. Sixteen had mitral stenosis, eight had mitral regurgitation and six had mitral stenosis and regurgitation. Mean pulmonary arterial wedge pressure ranged from 5-32 mmHg. All patients underwent complete catheterization and angiocardiographic study. None had significant gradient across the right ventricular outflow tract. Right maximum spatial vector (Rmsv) was calculated using Frank VCG.R in V1 and S in V5 of ECG were also measured. Rmsv, RV1, and SV5 were correlated with pulmonary arterial pressures (systolic, diastolic and mean). Pulmonary artery systolic pressure and Rmsv bear the best correlation (r=0.773). The correlation coefficient for pulmonary artery diastolic pressure and Rmsv was 0.698. Rmsv as calculated from Frank VCG is useful in prediction of pulmonary arterial pressures (systolic and diastolic) in pediatric patients with rheumatic mitral valve disease.

We previously reported that pulmonary artery pressures can be assessed in children with chronic rheumatic mitral valve disease by measuring right maximum spatial vector from Frank vectorcardiogram. To simplify the calculation, pulmonary artery systolic pressure was correlated with maximum negative deflection on Frank scalar X-lead (SX), maximum negative deflection on scalar Z lead (SZ), sum total of SX and SZ (SX+SZ) and combined SX and SZ. The patient material consisted of 30 children with chronic rheumatic mitral valve disease, aged 8-14 1/2 years. Eleven were male and 19 were female. Sixteen had mitral stenosis, 8 had mitral regurgitation, and 6 had combined mitral regurgitation and stenosis, documented by cardiac catheterization and angiocardiographic study. The results showed a significant correlation between pulmonary artery systolic pressure and SX (r=0.782). As calculation of SX is considerably easier and less time consuming than that of right maximum spatial vector, this simplified method is preferable to right maximum spatial vector for prediction of the pulmonary artery systolic pressure of children with pulmonary hypertension due to chronic rheumatic mitral valve disease.

One of the difficulties for the fetal sonographer is the complete elucidation of structural defects of the cardiovascular system that are associated with intracardiac or great vessel flow disturbances. With the recent introduction of Doppler color flow mapping, in which blood flow is displayed in color superimposed on a real-time image, it has been impossible to identify flow disturbances in the pediatric and adult patient. This study was undertaken to determine whether Doppler color flow mapping could be used in the fetus to identify normal and abnormal cardiovascular anatomy. Thirty-five normal and high-risk fetuses were examined between 16 and 40 weeks of gestation. Doppler color flow mapping identified normal and abnormal anatomy (ventricular septal defect, atrial septal defect, endocardial fibroelastosis, dysplastic pulmonary valve, and tricuspid regurgitation). It appears that Doppler color flow mapping will add a new dimension to fetal cardiovascular imaging.

Fetal and neonatal biophysical and biochemical changes were studied in four preterm infants who developed cardiogenic shock as a result of severe perinatal asphyxia. Fetal distress was documented by the presence of severe late and variable decelerations associated with decreased fetal heart rate variability. Severity of fetal acidosis was decumented by scalp and umbilical cord blood pH. Apgar scores at 1, 5, and 10 minutes were all equal to or less than 5. Although the clinical findings shortly after birth resembled respiratory distress syndrome, it was possible to make a primary diagnosis of cardiac failure with the recognition of cardiomegaly, hepatomegaly, electrocardiographic changes of myocardial hypoxia, decreased myocardial contractility, elevated central venous pressure, and severe lactic acidosis. The treatment of heart failure, including use of inotropic agents, resulted in rapid improvement in the clinical condition, with reversal of the abnormal findings within 24 to 36 hours. Concomitant with this improvement, the increase in arterial blood pressure was paralleled by increase in peripheral (toe) temperature.

M-mode echocardiographic examination of the right and left ventricles was performed on 82 normal fetuses between 18 and 41 weeks of gestation. The diameter of the right and left ventricles correlated with the biparietal diameter. The right/left ratio of the ventricular diameters remained constant (1:1) throughout gestation. Fractional shortening and mean circumferential shortening of both ventricles were independent of gestational age. The data presented in this paper will allow the clinician to evaluate abnormal fetal conditions that might affect cardiovascular structure and/or function.

Radiant heat is known to increase insensible water loss and, to a certain extent, oxygen consumption. Little is known about its cardiovascular effects. We measured cardiac output, stroke volume, heart rate, and lower limb and skin blood flow in 20 preterm newborn infants nursed in an incubator and under a radiant warmer at an abdominal skin temperature of 36.5 degrees C. Mean (+/- SEM) birth weight was 1.57 (0.06) kg, gestational age 31.7 (0.4) weeks, and weight at examination 1.69 (0.02) kg; median postnatal age was 15 days. Skin and limb blood flow measurements increased by 44% to 55% with radiant heat (P less than .001 and P less than .01, respectively). Cardiac output increased by 5.4% (P less than .02) under the radiant warmer secondary to a small but significant (P less than .05) increase in heart rate. The changes in cardiac output during radiant heat administration are comparable to those reported for oxygen consumption.

The purpose of our study was to quantitate left ventricular outflow obstruction in the infant of the diabetic mother (IDM) through estimation of cardiac output by pulsed Doppler ultrasound. We evaluated 42 IDMs (White class B, C, or D) and compared them with two control groups, one similar in birth weight and the other similar in gestational age. Ventricular septal hypertrophy was found in 18 (43%) of 42 of the IDMs, but in none of the control infants. Morbidity increased with advancing septal thickness. None had hyaline membrane disease. Twenty-nine IDMs were asymptomatic, 11 of whom had septal hypertrophy. Thirteen IDMs developed congestive heart failure, seven of whom had septal hypertrophy. Cardiac output per kilogram diminished linearly with increasing septal thickness (r = -0.78, P less than 0.001) secondary to reduced stroke volumes at comparable heart rates. The IDMs had higher left atrial/aortic ratios and greater right ventricular systolic time intervals than the control infants. We conclude that cardiac output is significantly reduced in IDMs with septal hypertrophy. This reduction is secondary to reduced stroke volume and is directly related to the degree of septal hypertrophy.

The incidence of clinically detectable patient ductus arteriosus (PDA) in a group of preterm infants whose birth weights were less than 2,000 g was compared with that of a similar group of infants whose mothers received antenatal glucocorticoids. A PDA was diagnosed on the basis of a typical heart murmur, increased precordial activity, and bounding peripheral pulses beyond the third day of life. Whereas 14 (44%) of 32 infants who were not exposed to antenatal glucocorticoids showed evidence of a PDA, only one (6.5% of 15 infants whose mothers received antenatal glucocorticoids had similar findings. The incidence of ruptured membranes (greater than 72 hours), the number of infants who were small for gestational age, and clinical management of the infants in the two groups were similar.

Tetralogy of Fallot has increased in incidence during the past decade. Although abnormalities of the four-chamber screening examination of the fetal heart identifies structural anomalies associated with semilunar and atrioventricular valve hypoplasias, the anomalies associated with tetralogy of Fallot are not as readily identifiable from the four-chamber view alone. This study was designed to determine whether aortic root dilatation, commonly observed in the newborn with tetralogy of Fallot, is a marker for tetralogy of Fallot diagnosed in utero. In 45 normal (control) fetuses the biparietal diameter, head circumference, abdominal circumference, and femur length were measured and M-mode measurements were made of the biventricular outer dimension and aortic root dimension. The aortic root dimension from seven fetuses (18, 19, 20, 23, 32, 33, and 34 weeks' gestation) with tetralogy of Fallot was increased in dimension when compared with cardiac (biventricular outer dimension) and noncardiac biparietal diameter, head and abdomen circumferences, and femur length parameters. In conclusion, incorporation of aortic root imaging with the four-chamber view of the fetal heart during a routine screening examination allows for identification of fetuses with tetralogy of Fallot.

Ouabain-induced tachyarrhythmias in cats can be abolished by bolus injection of NaHCO3 solution. This effect is consistent, rapid and of short duration. The antiarrhythmic effect appears to be due to high sodium concentration of this solution, as hypertonic NaCl solution with equal concentration of sodium exerts the same effect. Alkalinity and hyper-osmolality cannot account for the antiarrhythmic effect of NaHCO3 as respiratory alkalosis and mannitol solution with equal osmolality did not relieve the arrhythmias. Overdrive suppression is not responsible for this effect as the heart rate slows down during normalization of the cardiac rhythm. It is postulated that high Na+ concentration abolished ouabain-induced arrhythmias by competition with calcium ion in the myocardial cell sarcotubular system thus replacing it. This hypothesis is supported by the known effect of other agents such as sodium-EDTA and magnesium chloride, in digitalis-induced arrhythmias, which exert their antiarrhythmic properties by removal or displacement of calcium in the myocardial cells.

Four infants with the severe form of the syndrome of tetralogy of Fallot and absent pulmonary valve are described. All had severe respiratory distress due to bronchial compression from massively dilated pulmonary arteries. The clinical diagnosis was confirmed by cardiac catheterization and angiocardiography. The infants died at age 3, 5, 30 and 90 days, respectively. Autopsy revealed, in addition to the usual components of the syndrome, absence of the ductus arteriosus or its remnants. The possible relation of "agenesis" of the ductus arteriosus to the pathogenesis of the severe form of this syndrome is discussed and pertinent studies are reviewed.

Eighty-two normal fetuses were scanned from 18 to 41 weeks of gestation. The following M-mode measurements were correlated with the femur length: end-diastolic right ventricular (r = 0.93), left ventricular (r = 0.92), biventricular outer (r = 0.94), and biventricular inner (r = 0.94) dimensions; tricuspid (r = 0.93) and mitral (r = 0.92) valve opening excursion; right (r = 0.76) and left (r = 0.70) ventricular wall thickness; and interventricular septal thickness (r = 0.75). Polynomial regression demonstrated that linear regression best described the data from which the mean and 5% and 95% confidence limits for predicted M-mode measurements were computed for the femur length.

Phototherapy is known to increase peripheral blood flow in neonates, but information on the associated cardiovascular effects is not available. Using pulsed Doppler echocardiography we evaluated cardiac output and stroke volume in 12 preterm and 13 term neonates during and after phototherapy. We concomitantly measured arterial limb blood flow by strain gauge plethysmography and skin blood flow by photoplethysmography. Cardiac output decreased by 6% due to reduced stroke volume during phototherapy, whereas total limb blood flow and skin blood flow increased by 38% and 41%, respectively. Peripheral blood flow increments tended to be higher in the preterm than in the term infants. The reduced stroke volume during phototherapy may be an expression of reduced activity of the newborn during phototherapy. For healthy neonates the reduction in cardiac output is minimal, but for sick infants with reduced cardiac output, this reduction may further aggravate the decrease in tissue perfusion.

VVLBW infants pose a challenge in the management of their hemodynamic changes. Data are just accumulating regarding the hemodynamic variables in this very special group. We have described several newly developed methods of monitoring hemodynamic variables in infants less than 1000 gm. In the coming decade, some of these methods may become more refined and routine.

The cardiovascular effects of theophylline were studied in 11 clinically stable preterm infants. Theophylline was given as aminophylline using a loading dose of 6.8 mg/kg and a maintenance dose of 2 mg/kg every 8 hours intravenously. Cardiac output, stroke volume, and heart rate were measured using a combination of pulsed Doppler ultrasound and M-mode echocardiography. Compared with day 0, an increase was found in both cardiac output (P less than 0.01) and stroke volume (P less than 0.02) on days 1, 2, and 3. By day 7, stroke volume was comparable to pretreatment values, whereas cardiac output was still increased. Heart rate was augmented significantly (P less than 0.01) throughout the treatment period. Mean arterial blood pressure did not change. All but one of the neonates had serum theophylline concentrations between 6 and 13 mg/L. We conclude that both inotropic and chronotropic effects are evident during the first days of theophylline therapy. The metabolic cost of the increased cardiac output in the preterm infant with theophylline therapy deserves further attention.

The authors evaluated transcutaneous PCO2 (PtcCO2) and PO2 (PtcO2) electrodes in 25 infants. Their diagnosis were severe hyaline membrane disease (HMD) (18), aspiration syndrome (3), severe hydrops, (3) persistent fetal circulation (6), and the others, congenital pneumonia, congenital plural effusion, pulmonary hemorrhage. In most all, the cardiovascular system was compromised, i.e., PDA with congestive heart failure and shock. PtcO2 electrode was heated to 43.5 degrees C while PtcCO2 electrode was not heated. Simultaneous arterial blood pressure (ABP), pH, arterial blood gases were obtained with the transcutaneous gas measurements. The data were analyzed first dividing all the paired arterial and transcutaneous gas tensions into those with and without cardiovascular drugs (dopamine, isoproterenol), and second, the paired values were divided into those taken (a) during severe acidosis (pH less than 7.25), (b) hypotension (less than 2 SD) of normal, and (c) hypotension and acidosis. These data show: (1) the unheated PtcCO2 and heated PtcO2 accurately correlated with the simultaneous arterial measurements: (2) PtcCO2 reflects tissue PCO2; (3) drugs affect both the PtcCO2 and PtcO2; (4) elevated PtcCO2 dissociating from the simultaneous PaCO2 in neonates with cardiovascular compromise results from decreased tissue perfusion. These data suggest that transcutaneous gas sensors perform dual functions; first, as gas monitors in patients without cardiovascular alterations, and second, in patients with cardiovascular compromise, PtcCO2 reflected tissue perfusion and PtcCO2 monitored oxygen delivery to the tissues.

11 fetal lambs with gestational age of 116-135 days were studied while connected to a membrane-oxygenator replacing the ventilatory function of the placenta. Progressive increase in arterial oxygen tension from 20 to 220 mm Hg resulted in progressive decrease in baseline heart rate and baseline arterial blood pressure indicating presence of chemoreceptor activity over this wide range of arterial oxygen tension. The effect of 60 sec complete umbilical cord occlusion was studied at progressively higher arterial oxygen tension and it was concluded that the chemoreceptor activity at fetal normoxic condition is very brisk and is markedly attenuated at hyperoxic levels. Although it was not possible to completely separate baroreceptor and chemoreceptor reflexes involved in cardiovascular response to umbilical cord occlusion, it is postulated that the chemoreceptor and baroreceptor reflexes are complimentary during cardiovascular responses to umbilical cord occlusion.

Neonatal heart rate variability (NHRV) was studied in 92 preterm infants (birth weight, 750 to 2,500 gm; gestational age, 28 to 36 weeks). Each infant was monitored continuously during the first 6 hours and for one hour at 24, 48, and 168 hours of life. During each hour NHRV was quantified and related to the following parameters: sex, gestational age, postnatal age, heart rate, and the presence and severity of respiratory distress syndrome (RDS). NHRV in healthy preterm infants was inversely related to heart rate level and directly related to the infant's postnatal age. In healthy babies with gestations of 30 to 36 weeks there was no significant correlation between NHRV and gestation. Decrease in NHRV was significantly related to the severity of RDS, and the reappearance of NHRV in infants with RDS was associated with a good prognosis. Decreased NHRV significantly differentiated the infants with RDS who survived after the fifth hour of life. The data reveal that NHRV (1) should be corrected for heart rate level and postnatal age; (2) is decreased in RDS; and (3) can be used as an indicator of morbidity and mortality in preterm infants with RDS.

Decreased cardiac output is a common presumption in left ventricular myocardial dysfunction in neonates, but because of a lack of reliable noninvasive techniques, data on cardiac output are missing. We measured cardiac output by pulsed Doppler echocardiography in 22 newborn infants with left ventricular myocardial dysfunction diagnosed by M-mode echocardiography. Eleven neonates had severe perinatal asphyxia, seven had tachypnea, two hypoglycemia, and one septic shock; one had no symptoms. Right ventricular function was abnormal in 13 of the 22 infants. Hypotension was found in eight; cardiac output and stroke volume were low in 20. The abnormalities were more pronounced in infants with asphyxia. Six such infants were given dopamine (4 to 10 micrograms/kg/min). Within 1 hour, arterial blood pressure, cardiac output, stroke volume, and heart rate increased sharply, with normalization of the myocardial contractility; the other echocardiographic abnormalities normalized over 24 to 48 hours. Pulsed Doppler echocardiography is an advance in the detection and evaluation of therapy for left ventricular myocardial dysfunction in the neonate.

A comparative morphometric study was performed on the aortomitral valve apparatus of the embryonic and adult chicken hearts. It was found that the thickness of the aortic and mitral valve cusps diminishes dramatically as the embryo matures, however the relative length of the aortic valve, mitral valve and subaortic conus remains constant. A comparison of the aortomitral valve apparatus in chicken and man revealed that the subaortic conus is not completely resorbed in the fowl, whereas this process is well documented in the mammalian hearts. The implications of this observation on "the differential conal growth hypothesis" of transposition of the great arteries are discussed.

A heart specimen is presented which showed a rare combination of atrioventricular valve atresia with single ventricle, truncus arteriosus communis with an anteriorly placed trunk, ie transposition. Because of the problems involved in the classification of this heart, the types of single ventricle are revised with particular attention to the rare cases of atrioventricular valve atresia and single ventricle reported in the literature. Also the rare type of truncus arteriosus communis with truncoatrioventricular valve discontinuity is excluded from the so-called transposition complexes, and properly classified as a form of truncus. The literal meaning of transposition is stressed and it is urged to approach congenital heart defects in a purely anatomic sense with definition of each segment as accurately as possible. Thus the present confusion in terminology and further plethora of new terms are avoided.

Direct systolic, diastolic, and mean arterial blood pressure was continuously recorded during the first 64 min of life in 150 newborn infants. The data were analyzed at 4, 8, 16, 32, and 64 min. The highest blood pressure values were noted during the first few minutes of life in all newborn infants, with a rapid drop within 4 to 8 min. Decline in blood pressure was more gradual throughout the remainder of the observation period. Blood pressures of depressed newborn infants at birth (Apgar scores 6 or less at 1 and 5 min) were compared to those of normal newborn infants (Apgar scores 7 or greater at 1 and 5 min). The former demonstrated generally higher systolic pressures during the first 16 min and diastolic pressures at 4 min when infants were compared by their 1 min Apgar scores and higher diastolic pressures at 4 min when the infants were compared by their 5 min Apgar scores.

Changes in pulmonary resistance, dynamic compliance, tidal volume, and transcutaneous PO2 and PCO2 after nebulized administration of metaproterenol were evaluated in eight newborn infants (birth weight 650 to 1060 g, gestational age 25 to 28 weeks) with chronic lung disease receiving mechanical ventilation. The infants were monitored continuously before and for 15 minutes after nebulization of metaproterenol during 3 consecutive days at mean age 34 days. There were significant increases in compliance, tidal volume, and tcPO2, and significant decreases in pulmonary resistance and tcPCO2. These data show that bronchospasm contributes significantly to the high pulmonary resistance in preterm infants with chronic lung disease and that metaproterenol is beneficial in the therapy of infants with chronic lung disease requiring mechanical ventilation.

Noninvasive monitoring of cardiac output can greatly facilitate the clinical assessment and management of neonates with cardiovascular compromise. To assess normal values of cardiac output in neonates, mean blood flow velocity was measured in the ascending aorta from a suprasternal approach using a range-gated, pulsed Doppler velocity meter, and aortic root diameter was determined from an M-mode echocardiogram. These techniques were combined, and cardiac output was evaluated in 59 healthy premature and 62 term newborn infants during the first week of life. Birth weights ranged from 780 g to 4,740 g and gestational age from 27 to 42 weeks. Cardiac output values increased linearly with advancing birth weight (r = +.94, P less than 0.001) and gestational age (r = +.95, P less than .001). Mean cardiac output values (+/- SD) per kilogram of body weight were 249 +/- 34 mL/min/kg and decreased with advancing birth weight: less than 1,500 g = 265 +/- 32 mL/min/kg; 1,500 to 2,500 g = 253 +/- 34 mL/min/kg; and greater than 2,500 g = 241 +/- 33 mL/min/kg. For clinical use, 325 mL/min/kg and 200 mL/min/kg can be used as upper and lower limits of normal, respectively. Doppler cardiac output estimates compared favorably with studies using invasive techniques.

A 10-month-old boy is presented who had isolated unilateral absence of the right pulmonary artery. He suffered from hemoptysis and severe congestive heart failure. The patient underwent prosthetic anastomosis of the right to the main pulmonary artery. Although the hemodynamic response was favorable, his oxygenation did not improve due to diffuse pulmonary arteriovenous fistulae of the affected lung. The patient succumbed 3 months after operation due to massive uncontrollable hemoptysis from the right lung. Isolated unilateral absence of the pulmonary artery is a rare lesion. In our review of the world literature as of November 1976, 47 cases (including this report) of the unilateral absence of the pulmonary artery have been reported. Of these 25.5% had pulmonary hypertension and only 4 cases underwent successful repair of the lesion. Though repair of this defect can be carried out, the result may not be always gratifying. Our experience with this case has led us to consider a lung biopsy before proceeding to the surgical repair of the lesion. If the affected lung shows arteriovenous abnormalities the operation should not be recommended.

High left ventricular output (LVO) values are associated with symptomatic left-to-right ductal shunting in preterm infants. However, LVO data prior to the occurrence of symptomatic patent ductus arteriosus (SPDA) are lacking. To determine whether serial measurements could predict a SPDA, we measured LVO from day 1 until day 10 with pulsed Doppler echocardiography in 25 preterm infants with birth weights of less than 1,250 g and hematocrits of more than 0.40. Eleven infants never developed patent ductus arteriosus symptoms and had LVO values within the normal range (190-310 ml/min/kg) with only minimal daily variations. The remaining 14 infants developed SPDA which required treatment with indomethacin, ductal ligation, or fluid restriction on days 2-5. From day 1 until day 5 their mean LVO values were significantly higher compared to the group without left-to-right ductal shunt and this increase was secondary to higher stroke volume values. An increase in LVO of more than 60 ml/min/kg consistently preceded SPDA by at least 24 h. Serial measurements of LVO using a single-pulsed Doppler approach can be used for early prediction of SPDA.

Aortic root diameter measurements were obtained during the first week of life by M-mode echocardiography using leading edge methodology during early diastole in 172 preterm and 228 term neonates. At least 40 newborns were included in each 500-g birth-weight subgroup from 750 to 4750 g. The aortic root diameter increased linearly from 0.63 +/- 0.04 cm in newborns with birth weights of 750-1249 g to 1.06 +/- 0.06 cm in newborns of 4250-4750 g.

Disopyramide has been successfully used to treat a variety of supraventricular and ventricular arrhythmias. The electrophysiologic effects of this drug were studied following diagnostic cardiac catheterization in 14 children aged 7 months to 14 years, suffering from congential heart disease. Surface EKG, intra-atrial, and His bundle electrogram as well as right atrial pacing with the use of extrastimulus technique were obtained before and after a single intravenous dose of disopyramide (2 mg/Kg, max 50 mg). The drug significantly prolonged the HV interval, effective and functional refractory periods of the atrium and the AV node. The most consistent change was the prolongation of the atrial refractory periods. The electrophysiologic effects of this drug on the conduction system have been variable and this variability has been attributed to the degree of vagal tone. The findings in this age group are similar to adults with simultaneous cholinergic blockade. This might be due to the direct depressant effects of disopyramide on the atrial and AV nodal tissue, and point to the potential usefulness of this drug in the pediatric age group.

Heart rate, blood pressure, transcutaneous gases, and catecholamine changes following intravenous injection of pancuronium were evaluated in seven ill newborn infants (birth weight: 1,280 to 4,500 g; gestational age, 29 to 42 weeks). Each infant was monitored continuously for 30 minutes before and 50 minutes after infusion of the paralyzing agent. There were no significant changes in transcutaneous gases, whereas significant increases in heart rate; systolic, diastolic, and mean blood pressures; and blood norepinephrine and epinephrine levels were found. The increase in heart rate lasted for 30 minutes, and the increase in blood pressure persisted for 50 minutes after administration of the drug. Because of the potential relationship between increased blood pressure and intraventricular hemorrhage and myocardial dysfunction, heart rate and blood pressure must be monitored during infusion of pancuronium in distressed newborns. These data suggest that pancuronium stimulates sympathetic activity in distressed newborns.

A technique that makes use of real-time-directed M-mode echocardiography is described in which the fetal heart is evaluated for suspected cardiac arrhythmias. Simultaneous M-mode recording of aortic, mitral, or tricuspid valvular leaflet excursion and/or atrioventricular wall motion defines timing relationships between atrial and ventricular systole. With the use of the techniques described in this report, normal as well as abnormal atrioventricular contractions can be quantitated and cardiac arrhythmias accurately defined.

During the period from February, 1971 to February, 1973, 30 premature infants underwent surgical ligation of patent ductus arteriosus. The gestational ages ranged from 25 to 36 wk (mean 30), and the birth weights ranged from 760 to 2010 g (mean 1274). The patients were divided into two groups on the basis of the indications for assisted ventilation. Group I consisted of 21 patients with severe hylanine membrane disease who required assisted ventilation during the first 2 days of life and could not be weaned off the respiratory by 10 days of age. Group II was composed of nine infants who required intermittent positive-pressure breathing after a mean age of 8 days because of repeated apneic spells secondary to uncontrollable heart failure. All infants in Group II survived the operation and left the hospital well. Fourteen of the 21 patients in Group I survived; the seven deaths were all due to underlying severe pulmonary disease (bronchopulmonary dysplasia). The value of PDA ligation in premature infants with uncontrollable heart failure is demonstrated in this study; this procedure also appears to be beneficial in neonates with severe respiratory distress syndrome.

Frank vectorcardiograms (VCGs) in four patients with left ventricular-right atrial (LV-RA) communication were analyzed and compared with published values of VCGs of normal individuals and those from a group of patients with membranous ventricular septal defect. It was observed that the QRS-loops in the frontal and sagittal planes of the patients with LV-RA communication are shifted more superiorly than usual. Thus, almost 50% of the QRS-loop area was superior to the X- and Z-coordinates in the frontal and sagittal planes, whereas in the controls less than 10% of the frontal and sagittal plane QRS-loops were superior to the horizontal axes. The QRS-loops of patients with LV-RA communication thus seem to be halfway between normal and endocardial cushion defect loops. An unusual degree of superior orientation of the QRS-loop in a patient with clinical findings of a ventricular septal defect should arouse suspicion of a LV-RA communication. Also in patients with an isolated ventricular septal defect but with an exaggerated superior orientation of the QRS-loop in the frontal and sagittal planes, the interatrial septum should be examined at the time of operation to exclude the possibility of an associated LV-RA communication.

The aortic root dimension and aortic valve excursion of 43 normal fetuses were recorded with M-mode echocardiography and the measured dimensions correlated with noncardiac measurements (biparietal diameter, head circumference, abdominal circumference, and femur length) and cardiac measurements (diastolic biventricular inner dimension, diastolic left ventricular internal dimension, and mitral valve excursion). The correlation coefficients for the aortic root dimension ranged between 0.87 and 0.95, while those for the aortic valve excursion ranged between 0.78 and 0.87. Regression analysis demonstrated that the best fit of the data was a linear model from which the 5% and 95% confidence limits were computed for individual predictions of aortic root dimension and aortic valve excursion from noncardiac and cardiac measurements.

The combination of 2-dimensional real-time and pulsed Doppler echocardiography provides a noninvasive method of measuring blood flow and has been used to study blood flow at the lower thoracic level in the descending aorta of the human fetus. Using these techniques, we evaluated the proportion of cardiac output distributed through the descending aorta in 20 healthy term newborn infants at 1-6 days of age. Blood flow in the ascending aorta was 759 +/- 135 ml/min (mean +/- S.D.) and in the descending aorta 482 +/- 92 ml/min indicating that 63.8% of the left ventricular output is distributed through the descending aorta. Peak systolic and mean blood flow velocities were comparable at the two sites, whereas the diameter of the descending aorta was 19% smaller than that of the ascending aorta. The changes in aortic blood flow were correlated with the changes in aortic diameter.

The continuous recordings of arterial oxygen saturation (SaO2) and beat-to-beat heart rate before, during, and after tracheobronchial suctioning were studied in eight preterm infants with severe RDS receiving mechanical ventilation. Two suctioning procedures were alternatively performed in each infant; In procedure A, disconnection of the ventilator and preoxygenation preceded suctioning; in procedure B, a special suction adaptor was used without ventilatory interruption or preoxygenation; 128 suctionings were performed with each procedure and the changes in heart rate (HR) and SaO2 during suctioning were compared. Although in both procedures, HR and SaO2 decreased during suctioning, the degree of bradycardia and arterial blood oxygen desaturation were significantly smaller in magnitude and shorter in duration during procedure B. These data indicate advantages of the suction adaptor in minimizing bradycardia and hypoxia from airway suction.

The incidence of persistent patency of the ductus arteriosus beyond the third day of life was prospectively determined in 100 preterm infants with birthweights of 2,000 gm or less and 50 infants with birthweights of 2,001 to 2,500 gm. The overall incidence was 21% and was inversely related to increasing gestational age and birthweight. The data suggest that immaturity is the major determinant of the persistent patency of the ductus arteriosus. Spontaneous delayed closure of the ductus occurred in 79% of patients that survived the immediate neonatal period. There was a high degree of association between the presence of a patent ductus arteriosus (PDA) and respiratory distress syndrome (RDS). Eight infants with severe RDS and PDA developed heart failure and four required surgical ligation of the ductus. None of the infants with birthweights greater than 2,000 gm who had PDA developed heart failure or required surgical ligation of the ductus arteriosus.

This article dicusses emergencies of cardiovascular origin in infants and children. Particular attention is given to congestive heart failure, hypoxic states, arrhythmias, cardiac tamponade, perinatal cardaic emergencies and conditions simulating cardiac crises. An outline of etiologic and therapeutic approach is included, and guidelines are provided for the practitioner who is called to care for such emergency situations.