Infantile hypertrophic cardiomyopathy of glycogenosis type IX: isolated cardiac phosphorylase kinase deficiency

Glycogen storage disease confined to the heart due to cardiac phosphorylase kinase deficiency causes a fatal infantile cardiomyopathy. Cardiomegaly can be detected in utero and is progressive. Electrocardiographic and echocardiographic findings are characteristic but not specific; these include large QRS complexes, short PR interval, and a hypertrophic nonobstructive pattern. Conclusive diagnosis requires biochemical analysis of myocardium, which may not be possible premortem due to the amount of tissue required. Pathologic examination of a standard cardiac biopsy can provide a presumptive diagnosis. There is no current treatment except a heart transplant. Infants succumb to heart failure and/or respiratory compromise due to pulmonary compression. This is a rare entity; only three cases have been reported to our knowledge. We report two additional cases.

Fetal tissue typing in anticipation of neonatal heart transplantation

BACKGROUND

Hypoplastic left heart syndrome is among the most common major congenital cardiac anomalies. Fetuses with this anomaly survive but require either reconstructive surgery or heart transplantation postnatally.

CASE

A woman whose fetus was diagnosed with hypoplastic left heart syndrome underwent funipuncture for fetal tissue typing. The fetus then was listed for heart transplantation. Once an ABO-compatible donor heart was procured, the fetus was delivered and immediately underwent transplantation.

CONCLUSION

In candidates for neonatal heart transplantation, fetal tissue typing allows the search for an ABO-compatible donor heart to begin earlier. This approach minimizes the morbidity associated with postnatal waiting and allows transplantation to take place while the neonate is less immunocompetent.

Doppler echocardiographic evaluation of pulmonary vascular resistance in children with congenital heart disease

Noninvasive assessment of pulmonary vascular resistance has not been well defined. Cardiac catheterization findings in 33 patients with congenital heart disease (mean age 1.4 years) were compared with Doppler echocardiographic parameters. The right ventricular pre-ejection period (RVPEP), ejection time (RVET), and the ration RVPEP/RVET correlated better with pulmonary vascular resistance than with pulmonary artery pressure. A highly significant correlation with a small standard error of estimate (SEE) was demonstrated between pulmonary vascular resistance and a newly derived parameter RVPEP/velocity time integral (VTI) [r = 0.87, p < 0.0001, SEE = 2]. An RVPEP/VTI value of < 0.4 seconds/meter (M) was able to select patients with pulmonary vascular resistance < 3 Wood Unit.M2, even in the presence of pulmonary artery hypertension caused by increased pulmonary blood flow, with 97% accuracy (100% sensitivity, and 92% specificity). An RVPEP/VTI value of 0.4 to 0.6 seconds/M identified patients with pulmonary vascular resistance between 3 to 7.5 Wood Unit.M2 with 91% accuracy, and a value of > or = 0.6 seconds/ M selected patients with total pulmonary vascular resistance > or = 7.5 Wood Unit.M2 with 94% accuracy.

Surgical treatment for cardiac rhabdomyomas in children

Cardiac rhabdomyomas are the most common cardiac tumor in children. These tumors may cause obstruction to blood flow, valvular insufficiency, and cardiac arrhythmias. We present two cases of cardiac rhabdomyomas in infants that were managed surgically and review the literature. Without surgical intervention, the prognosis for symptomatic cardiac rhabdomyomas is dismal, with eventual death likely due to heart failure or arrhythmias. As our two cases indicate, surgical treatment may improve this prognosis. Pediatric cardiac rhabdomyomas should be resected when the tumors cause hemodynamic compromise or cardiac arrhythmias.

Choreoathetosis after surgery for congenital heart disease

Choreoathetosis developed in three patients after cardiopulmonary bypass with hypothermia. None had significant hypotension or hypoxemia; all had hypocapnia and respiratory alkalosis during the rewarming period. We postulate that hypocapnia-induced cerebral vasoconstriction may have contributed to ischemic damage in focal central nervous system areas.

Prophylactic indomethacin for prevention of intraventricular hemorrhage in premature infants

The impact of early prophylactic use of intravenous indomethacin on the incidence and severity of periventricular-intraventricular hemorrhage and patent ductus arteriosus in 199 oxygen-requiring premature infants (less than or equal to 1300 g birth weight) was prospectively investigated. The trial was controlled, the infants were randomized, and the investigators were unaware of the group assignments. Patients with minimal (grade I) or no periventricular-intraventricular hemorrhage determined by prestudy echoencephalography were randomized within two birth weight subgroups (500 to 899 and 900 to 1300 g) to receive either prophylactic indomethacin (n = 99) or an equal volume of saline-vehicle placebo (n = 100). The first dose (0.2 mg/kg) was given within 12 hours of delivery and two subsequent doses (0.1 mg/kg) were administered at 12 hourly intervals. Prophylactic indomethacin significantly reduced the incidence of grades II to IV periventricular-intraventricular hemorrhage. Intraventricular hemorrhage was half as common in infants given prophylactic indomethacin as in control infants (23% v 46%, P less than .002). The reduction was manifested in both birth weight subgroups. Results of this study also confirmed a lower incidence of clinically significant patent ductus arteriosus in infants who received prophylactic indomethacin in contrast to those who received placebo (11% v 42%, P less than .001). No significant differences were found between treatment and control groups in the duration of oxygen therapy, mechanical ventilation, or hospitalization or in the incidence of pneumothorax, chronic lung disease, sepsis, necrotizing enterocolitis, retinopathy of prematurity, or death. Early prophylactic indomethacin initiated within 12 hours of delivery is effective in reducing the incidence of intraventricular hemorrhage as well as clinically significant patent ductus arteriosus in very low birth weight premature infants.

M-mode echocardiographic findings in children with idiopathic restrictive cardiomyopathy

The M-mode echocardiographic findings in five pediatric patients, ages 4-15 years, with primary idiopathic restrictive cardiomyopathy, diagnosed by cardiac catheterization, and of 12 normal children (control group) are presented. The M-mode echocardiographic findings in patients with restrictive cardiomyopathy were (1) normal left and right ventricular end-diastolic dimension, (2) normal left ventricular posterior wall and interventricular septal thickness (three patients) or mild concentric hypertrophy (two patients), (3) normal opening and closing velocity of the mitral valve, (4) consistently enlarged left atrium (more than 40 mm) in all, and (5) right ventricular systolic time intervals compatible with pulmonary artery hypertension. The left ventricular ejection phase parameters (systolic time intervals, shortening fraction, and mean velocity of circumferential fiber shortening) were normal. Left ventricular relaxation phase parameters (diastolic function) were abnormal. The isovolumic relaxation time index was prolonged, 68 +/- 40 ms (+/- SD), in the study group as compared with 11 +/- 6 ms (+/- SD) in the control group (P less than 0.001). Percent relaxation of left ventricular posterior wall endocardium at 50% of diastole was decreased, 58 +/- 4% (+/- SD), in the study group as compared with 85 +/- 6% (+/- SD) in the control group (P less than 0.005). We conclude that M-mode echocardiography provides a relatively useful and specific noninvasive method for the diagnosis of primary restrictive cardiomyopathy in pediatric patients.

Detection of pulmonary venous flow by pulsed Doppler echocardiography in children

Parasternal pulsed Doppler echocardiographic examinations of the left atrium were prospectively performed in 14 pediatric patients, aged 2 weeks to 8 years, in order to characterize the left atrial flow pattern in children. None of the patients had clinical or cardiac catheterization evidence (9 of 14 patients) of either mitral regurgitation, right-to-left shunts at the atrial level, or anomalies of pulmonary venous drainage. In all 14 patients, a systolic-diastolic positive velocity pattern could be recorded within the left atrium. Furthermore, this pattern was more readily detected in those children with left-to-right shunts. We conclude that continuous positive velocity patterns are commonly recorded in the left atria of children and probably represent pulmonary venous return. Demonstration of this signal is contingent on proper orientation of the transducer with respect to pulmonary venous flow.

Benign nature of atrial dissociation in pediatric patients

Atrial dissociation is defined electrocardiographically by the presence of an ectopic atrial rhythm depolarizing independently of the basic sinus rhythm, and is characterized by entrance and exit block. Atrial dissociation is most often observed as an ominous sign in adults with severe myocardial dysfunction. We have observed atrial dissociation in 3 pediatric patients, aged 5 to 22 years, who were essentially asymptomatic from this arrhythmia. All 3 patients are well, without therapy for atrial dissociation, during a follow-up period of 1 to 5 years. The benign nature of atrial dissociation in the pediatric patient as compared with the adult is stressed.

Sinus and atrioventricular nodal function: Preoperative and early postoperative assessment in children

Ninety-three rapid atrial pacing studies were performed in 38 children to compare preoperative and early postoperative function of the sinus and atrioventricular (AV) nodes. The interval between the preoperative and postoperative studies was under 6 months in the majority of patients. Postoperative studies were performed within 48 hours of operation and between 4 and 8 days after operation. Sinus nodal function as measured by sinus nodal recovery time (SNRT) was an unreliable index in determining depression since the number who improved postoperatively (10/55) was nearly equal to the number that worsened (12/55). The majority who had abnormal function postoperatively demonstrated a junctional rather than sinus recovery focus. This finding appears a more definitive and more reproducible indicator of sinus node depression in the postoperative patient. Postoperative AV nodal function was decreased (as measured by the cycle length [CL] at which Wenckebach periodicity occurred) in 15 of 55 studies (27%) of the entire group. There was nearly an equal chance for improvement (24%) in function. This also applied to those patients who had sequential studies. Therefore, this method of assessment for AV nodal function was unreliable, or else the operation did not affect the node significantly. The latter is unlikely in view of late postoperative data. The greatest utility of this test was to determine the capability for AV conduction in certain patients with slow escape rhythms in the absence of surface P waves, and to differentiate complete heart block from AV dissociation when atrial activity was absent. Despite the variability of effects on the sinus and AV nodes in these patients, those who demonstrated depression had a significantly higher incidence of dysrhythmias (80% of patients with sinus nodal depression and 100% of patients with AV nodal depression).

Right ventricular apical activation time in children. Reference standards for clinical use

To differentiate proximal from peripheral right bundle-branch block, several investigators have used the right ventricular apical (RVA) activation time, but there is a lack of reference standards for infants and other children. Using intracardiac electrography, His bundle and RVA electrograms were recorded in 123 children before surgery for various types of congenital cardiac malformations. None had evidence of conduction defects on their surface ECG. The average RVA activation time was 15 +/- 7 msec (+/- SD) linearly increasing with age from infancy to adolescence. The values found in this large population may be useful as reference standards for right bundle-branch conduction times in other infants and children.

Pulsed Doppler echocardiographic detection of coronary artery to right ventricle fistula

The pulsed Doppler echocardiographic (PDE) findings in a case of coronary artery right ventricle fistula are described. The PDE examination revealed normal flow patterns within the right atrium, pulmonary artery, and left ventricle, thus excluding these structures as the distal site of the fistula. Sampling within the right ventricular inflow revealed a turbulent, continuous, systolic-diastolic flow pattern that suggested the right ventricle was the distal end of the fistula. Postoperatively, the PDE examination of the right ventricle reverted to a normal, nonturbulent, phasic flow pattern. We conclude that PDE may be a useful noninvasive method of defining the site of drainage in cases of coronary artery fistula.

Left isomerism and complete atrioventricular block: a report of six cases

Six children, aged 12 days to 13 years, with left isomerism and complete atrioventricular (A-V) block are presented. In all six patients the diagnosis of left isomerism was suggested by an interrupted inferior vena cava found during cardiac catheterization and angiocardiography; four patients had complex heart disease consisting of endocardial cushion defect, five had a common atrium, three had pulmonary stenosis, three had patient ductus arteriosus and two had dextrocardia. Further anatomic abnormalities included situs inversus of the viscera (four patients) as well as partial malrotation of the bowel. Of the six patients, four had congenital complete A-V block, whereas the remaining two had A-V conduction disturbances documented during early infancy that progressed to complete A-V block later in life. All six patients required pacemaker implantation and five of the six patients died. This report discusses the clinical presentation of complete AV block and left isomerism and reviews the literature.

His-Purkinje responses and refractory periods during atrial extrastimulation in children with heart defects

During atrial extrastimulation, split His potentials, prolonged His-to-ventricular (H2V2) intervals and block distal to the His bundle deflection were observed in both preoperative and postoperative children with heart defects. His-Purkinje responses and refractoriness were identified in 31 of 78 (40%) pediatric patients (20 of 51 preoperative and 11 of 27 postoperative) during atrial extrastimulation coupled to sinus and/or paced cycle lengths. Split His potentials were found in 14 patients (eight preoperative and six postoperative) and His bundle relative refractory periods ranged from 250--490 msec. Prolonged H2V2 intervals were found in these and in an additional 16 patients (11 preoperative and five postoperative) and the relative refractory period of the His-Purkinje system ranged from 230--500 msec. Block distal to the His deflection occurred in seven patients (five preoperative and two postoperative) and the effective refractory period ranged from 230--510 msec. Split His potentials, long H2V2 intervals and block distal to the His bundle deflection produced by atrial extrastimulation were found in peroperative as well as postoperative children. These responses probably represent functional electrophysiologic characteristics of the pediatric cardiac conduction system.

Echocardiographic assessment of right bundle branch injury after repair of tetralogy of Fallot

Nineteen patients, ages 3 1/2-18 years, with electrocardiographic evidence of right bundle branch injury after intracardiac repair of tetralogy of Fallot, underwent invasive intracardiac electrophysiologic evaluation 1-13 years (mean 4.4 years) postoperatively. Categorization of the site of right bundle branch injury as proximal or distal was made by determining the V-RVA interval. In 11 of the patients, the V RVA interval was prolonged (> 35 msec), indicating proximal right bundle branch injury and in the other eight it was normal (< 35 msec), indicating distal bundle branch injury. Within 24 hours of the study, all patients were studied by M-mode echocardiography. Measurements were made of the tricuspid valve closure, mitral valve closure and the difference between the two, or the delta value. All but one patient with distal bundle branch injury had delta values of less than 40 msec (range 8-38 msec), while 10 or 11 patients with proximal bundle branch injury had delta values greater than 40 msec (range 41-116 msec). there was a significant positive correlation (r = 0.74, p < 0.001) between V-RVA and the delta value. We conclude that the delta value is an indicator of relative activation delay of the right ventricle, and therefore, in most cases, proximal vs distal bundle branch injury can be diagnosed noninvasively.

Dual atrioventricular nodal pathways: a benign finding in arrhythmia-free children with heart disease

The incidence and significance of dual atrioventricular (A-V) nodal pathways are described in 78 children with associated congenital or acquired heart disease. None of these patients had clinical or electrocardiographic evidence of arrhythmia. Dual A-V nodal pathways were observed in 35 percent of the preoperative group and in 33 percent of the postoperative group. Despite this substrate for A-V nodal reentry, supraventricular tachycardia was neither induced during electrophysiologic evaluation nor did it develop clinically over a follow-up period of 1 month to 15 years. It is concluded that dual A-V nodal pathways are common and may be a benign finding in arrhythmia-free children with heart disease.

Normal pulmonary vascular resistance and left ventricular hypertrophy in young infants with bronchopulmonary dysplasia: an echocardiographic and pathologic study

To evaluate the cardiac anatomy and functional hemodynamics in young infants with chronic lung disease, nine patients, aged 2 to 7 months, with a clinical diagnosis of bronchopulmonary dysplasia (BPD) underwent echocardiographic examination. All infants required supplemental O2 (mean FIO2 35%) to maintain adequate systemic oxygenation (Pao2 greater than 50 mm Hg). None of the infants had evidence of a patent ductus arteriosus at the time of examination. Echocardiographic measurements of left and right ventricular systolic time intervals revealed normal systolic time interval ratios suggesting pulmonary vascular resistances. However, echocardiographic evidence of left ventricular hypertrophy was found in eight of the nine infants, while right ventricular anterior wall thickness and right ventricular diastolic dimensions were not increased. Two infants died; marked left ventricular hypertrophy was noted at the time of postmortem examination while the right ventricular wall thickness was normal. The findings of left ventricular hypertrophy led to a retrospective review of autopsy material of seven patients who died with BPD over the past year. In six of seven cases examined, left ventricular posterior wall thickening was noted (range 7 to 11 mm); while the right ventricular wall thickness was normal (range 2 to 5 mm). These data suggest that (1) as assessed by echocardiography, the pulmonary vascular resistance is not significantly elevated in young infants with BPD, and (2) a hypertrophic left ventricle evolves which may assume importance in the pathogenesis of pulmonary edema in BPD, though the precise etiology remains undetermined.

Pulsed Doppler echocardiographic findings in total anomalous pulmonary venous drainage to the coronary sinus

The pulsed doppler echocardiographic (PDE) findings in a premature cyanotic infant with total anomalous pulmonary venous return to the coronary sinus are reported. Features that suggested the diagnosis of total anomalous pulmonary venous return were 1) an area of systolic-diastolic turbulent flow posterior to the apparent left atrial border, which was interpreted as representing the convergence of pulmonary venous return to a common pulmonary vein, and 2) systolic and diastolic turbulent flow within the right atrium suggesting pulmonary venous return through the coronary sinus. We suggest that PDE should be included as part of the evaluation of cyanotic infants in whom the diagnosis of total anomalous pulmonary venous return is considered.

A longitudinal evaluation of blood pressure in children

Blood pressure levels obtained on two occasions, one year apart, were evaluated among 212 children. An overall correlation of .65 was obtained for systolic pressure and .43 for diastolic pressure. The results suggest that adult levels of correlation are not reached in childhood and that screening programs must consider the relative lability of children's measurements in establishing referral criteria.

The fast-slow form of atrioventricular nodal reentrant tachycardia in children

An unusual form of atrioventricular (A-V) nodal reentry is described as the underlying mechanism for incessant tachycardia in two children. During tachycardia a fast pathway was utilized for anterograde conduction and a slow pathway for retrograde conduction. This is the reverse of the usual form of A-V nodal reentrant tachycardia, in which the slow pathway is utilized for anterograde conduction and the fast pathway for retrograde conduction. One patient had a smooth ventriculoatrial (V-A) conduction curve demonstrating exclusive utilization of the slow pathway for retrograde conduction. The other had a discontinuous V-A conduction curve demonstrating failure of retrograde fast pathway conduction with resultant slow pathway conduction. In both cases the retrograde effective refractory period of the fast pathway was longer than that of the slow pathway, resulting in the establishment of this unusual reentry circuit. Both patients had a superior P axis with a P-R interval shorter than the R-P interval during tachycardia, features described in a significant number of children with incessant tachycardia. This unusual form of reentrant tachycardia can be suggested by its electrocardiographic pattern and is another mechanism for reentrant tachycardia not previously documented in children.

High-dose propranolol therapy in the management of supraventricular tachycardia

Five patients, age 3 weeks to 11 years, presented with supraventricular tachycardia that remained uncontrolled following adequate digitalization. Four of these patients underwent invasive electrophysiologic studies to determine the mechanism of the arrhythmias. Of these four patients, three had concealed Wolff-Parkinson-White syndrome, and one patient had evidence of dual A-V nodal pathways. Propranolol was added to the medical treatment and was administered orally in doses ranging from 7 to 14 mg/kg/day (average 9 mg/kg/day). All five children remain free of their tachycardia except for one patient who occasionally has supraventricular tachycardia with febrile illnesses. No adverse reactions to these high doses of propranolol were encountered.

Risk factors for coronary artery disease in children of affected families

Risk factors for coronary artery disease were present to a greater degree in children of men who had experienced premature myocardial infarction when compared to children of unaffected male parents. Levels of cholesterol and body weight, as well as family history of premature CAD, differed significantly between the groups of children. The chance of identifying a child with hyperlipidemia was three times greater if the father had premature CAD. Data regarding familial aggregation of risk factors for CAD are reviewed and their significance discussed.

Applications of diagnostic ultrasound and radionuclides to cardiovascular diagnosis. Part II. Cardiovascular disease in the young

Echocardiography (ECHO) and radionuclide cardiography have had a significant impact on pediatric cardiology because they have proved to be sensitive enough to permit early diagnosis of many forms of heart disease and in some cases to estimate its severity and to provide information concerning ventricular performance. An overview of the anatomic and functional information that can be obtained from these two methods will be presented first, followed by details concerning the indications for their use and their relative clinical value in various acquired and congenital heart diseases. We have stressed particularly those facets of pediatric cardiac disease that differ most from those in the adult.