Mechanisms of cardiac arrhythmias after the Mustard operation for transposition of the great arteries

To determine the mechanisms of the cardiac arrhythmias frequently seen after the Mustard operation for transposition of the great arteries, intracardiac electrophysiologic studies were performed in 52 children 1 to 8 years after the Mustard operation. Sinus nodal automaticity as judged from the response to rapid atrial pacing was abnormal in 28 of the 52 children. Sinoatrial conduction (conduction of the sinus impulse to the atrium) was found to be abnormal in three of nine patients studied with the atrial extrastimulus method. Conduction of the sinus impulse from the high right atrium to the atrioventricular (A-V) node was abnormally delayed in only 2 of 41 subjects. The low lateral wall of the right atrium was depolarlzed late in 3 of 11 subjects (including the preceding 2). Two subjects showed delayed A-V nodal conduction and one delayed His-Purkinje conduction. The mechanism of supraventricular tachycardia induced in the laboratory was determined to be sinoatrial nodal reentry in four subjects and atrial muscle reentry in four. Two of the four with atrial muscle reentry had prolonged high right atrium to low lateral right atrium intervals during sinus rhythm.

Thus, damage to the sinus node remains the most common cause of arrhythmias after the Mustard operation. In addition, delayed atrial conduction may predispose to atrial muscle reentrant tachycardia.     

Echocardiographic evaluation of left ventricular function in children with congestive cardiomyopathy

Echocardiography was used to study left ventricular function in 37 children with congestive cardiomyopathy. Left atrial and left ventricular diameters were approximately 1.5 times that predicted by body weight, whereas systolic decrease in left ventricular diameter (shortening fraction) and increase in posterior wall thickness were half that of normal children. The ratio of left ventricular preejection period to ejection time was increased in 25 patients and normal in 10. The mean velocity of circumferential fiber shortening was decreased in 30 of 34 patients and averaged 52 percent of that predicted by heart rate.

The shortening fraction was higher in the 12 patients who were asymptomatic at the time of study than in the 25 who had symptoms of congestive heart failure (19.6 ± 2.4 standard error of the mean versus 14.6 ± 1.2) (P < 0.05). In 11 patients whose condition improved after therapy with digoxin and diuretic drugs, serial echocardiograms showed significant increases in shortening fraction and posterior wall thickening and decreases in left atrial diameter and the ratio of preejection period to ejection time. However, one or more indexes of left ventricular function remained abnormal, despite the resolution of symptoms and a return of heart size to normal as judged from the chest roentgenogram.     

Prognosis of symptomatic coarctation of the aorta in infancy

Medical and surgical advances have improved the outlook for infants with symptomatic coarctation of the aorta. To help predict the clinical course of individual patients and to aid in individualizing their treatment, a 10-year experience with this condition was reviewed. Of 97 infants with symptomatic coarctation, 10 had isolated defects. In these patients, medical treatment was successful and surgical intervention could be postponed to allow for growth. The 87 other patients with associated cardiac defects were generally sicker at presentation and required earlier operation. Eleven of these died before surgical correction, 10 died at the time of repair, and 13 died later. The overall survival rate after 8 years was 62%, with most deaths occurring in the first 6 months of life. Late surgical results are flawed by a 32% rate of residual coarctation. Late postoperative hypertension is uncommon, and is usually attributable to a residual coarctation.     

Echocardiographic pulsed doppler features of absent pulmonary valve syndrome in the neonate

M mode echocardiography was used to evaluate nine neonates with absent pulmonary valve syndrome. Six were also studied with two dimensional echocardiography and two with pulsed Doppler echocardiography. M mode echocardiography demonstrated a large, overriding great artery and right ventricular dilation in all nine patients and abnormal septal motion in eight. Two dimensional echocardiography demonstrated aneurysmal dilation of the main pulmonary artery in all six patients studied. Pulsed Doppler echocardiography in the two infants studied demonstrated anterograde systolic and retrograde diastolic flow in the main pulmonary artery and right ventricular outflow tract. The echocardiographic features of absent pulmonary valve syndrome appear to be unique and allow the diagnosis to be made noninvasively, thus obviating or delaying the need for potentially high risk cardiac catheterization.     

Atrioventricular valve abnormalities in infancy: two-dimensional echocardiographic and angiocardiographic comparison

The results of two-dimensional echocardiography and biplane angiocardiography from 47 infants with congenital atrioventricular (AV) valve abnormalities were compared. Eleven patients had atresia of the right AV valve, 10 had atresia of the left AV valve, 4 had hypoplasia of the right AV valve and 5 had hypoplasia of the left AV valve. Twelve patients had endocardial cushion defect, three had single ventricle and two had straddling of the left AV valve. There was agreement between the two techniques as to the number of AV valves present in each patient. The echocardiographic estimate of valve anular diameter was below normal in seven of the eight patients thought to have a hypoplastic anulus by angiocardiography. In 10 of the 12 patients with endocardial cushion defect, there was agreement between the two techniques as to the presence or absence of atrial and ventricular septal defect. The chordal attachments of straddling valves were better visualized by echocardiography; flow patterns and effective orifice size were better demonstrated by angiocardiography. The subcostal four chamber echocardiographic views and cranially angulated oblique angiocardiographic views were comparable and provided the best images for determination of the size and number of AV valves and their relation to the atrial and ventricular septa.     

Atrioventricular valve anular diameter: Two-dimensional echocardiographic-autopsy correlation

To study the accuracy of 2-dimensional echocardiography (2-D echo) in estimating mitral and tricuspid anular diameter, 2-D echo estimates were compared with autopsy measurements of anular diameter in 21 children studied by echo within 30 days of death. The mitral anulus was measured from the left parasternal long axis view and the apical or subcostal 4-chamber image and the tricuspid anulus from the 4-chamber view. Comparable measurements were made from the autopsy specimen with calipers. The correlation coefficient for echocardiographic vs autopsy measurements was 0.79 (standard error of the estimate 2.8 mm) (mitral long axis r = 0.76, mitral 4-chamber r = 0.85, tricuspid 4-chamber r = 0.76). Echo measurements exceeded the corresponding autopsy measurements by an average of 17%; this was at least partially attributed to shrinkage of the specimen during fixation. Thus, 2-D echo may be used to provide a reasonable estimate of mitral and tricuspid anular diameter.     

Ventricular septal defect in infancy: Detection with two dimensional echocardiography

To determine the sensitivity and specificity of two dimensional echocardiography in detecting ventricular septal defect two dimensional echocardiograms were performed on 53 infants under 1 year of age. The diagnosis of ventricular septal defect was confirmed by cardiac catheterization in 27 patients; an intact ventricular septum was confirmed by catheterization in 18 and clinically in 8. Using a 35 ° mechanical sector scanner with a 3.5 megahertz transducer, we imaged the ventricular septum in the long axis and in a four chamber view (apical or subcostal, or both). Images were recorded on videotape and reviewed independently by two observers unaware of the diagnosis. Interobserver agreement was 94 percent. Among the 27 patients with a ventricular septal defect, the lesion was correctly identified in 20 (74 percent) and was undetected in 7 (3 of whom had a defect less than 4 mm in diameter, as determined by angiography). No defect less than 4 mm in diameter was detected. Among the 26 patients with an intact septum, a defect was correctly excluded in 23 (88 percent); a false positive diagnosis was made in 3. The apical and subcostal views demonstrated the greatest number of defects (20 of 20), but also gave the highest number of false positive diagnoses (3 of 3). The long axis view was helpful when positive, but showed only 9 of 20 of the defects.In this study, two dimensional echocardiography detected approximately three fourths of ventricular septal defects large enough to warrant cardiac catheterization in the 1st year of life. False positive diagnoses were related to dropout of echoes in the membranous septum when imaged in the four chamber views.     

Control of late postoperative ventricular arrhythmias with phenytoin in young patients

Ventricular arrhythmias probably initiate the events leading to sudden death in patients who have recovered uneventfully from surgery for congenital heart disease. It is therefore recommended that antiarrhythmic therapy be given to all patients who have had surgery for congenital heart defects and who have ventricular arrhythmias found in a routine electrocardiogram taken after the immediate postoperative period. The response of ventricular arrhythmias to treatment was studied in six ambulatory patients aged 7 to 27 years (mean 16.5) who had had surgery a mean of 10.7 years before the arrhythmia was recognized. Four patients had unsatisfactory repair of the congenital defect; the two other patients had only a palliative operation. Each patient's electrocardiogram was monitored continually by tape recording. Each received phenytoin, 3.75 mg/kg body weight, every 6 hours for four doses, then 1.9 mg/kg every 6 hours until the serum concentration of phenytoin was 15 to 20 μg/ml. This serum concentration was maintained with the daily administration of 2.5 to 3 mg/kg every 12 hours. In the 24 hours before treatment, two patients had ventricular tachycardia, two had paired premature ventricular complexes and two had 10 or more single premature ventricular complexes/hour. After treatment, all patients had “effective control” (one or less premature ventricular complex/hour for 12 consecutive hours). This control was achieved with phenytoin in five patients, but one patient required the addition of disopyramide (2 mg/kg every 6 hours). All five patients undergoing a treadmill test before treatment had premature ventricular complexes during or after exercise; after treatment, only one had premature ventricular complexes after exercise. The patient who required two drugs was unable to perform a treadmill test. The mean effective serum phenytoin concentration, 15.7 μg/ml (range 8.5 to 20.0), was reached at a mean time of 61.2 hours (range 42 to 80) after the start of phenytoin therapy. Ataxia occurred in two patients with serum phenytoin concentrations of 16 and 20 μg, but not in the other four, three of whom had serum concentrations greater than 20 μg/ml. Echocardiographic, hematopoletic, hepatic and renal function indexes remained constant with treatment.It is concluded that (1) phenytoin suppressed ventricular arrhythmias in six children and young adults after surgery for congenital heart disease; (2) the effective serum concentration of phenytoin was approximately 15 μg/ml, but varied widely; and (3) this concentration was achieved within 48 to 72 hours when an oral loading dose was administered.     

Congenital complete atrioventricular block: Clinical and electrophysiologic predictors of need for pacemaker insertion

Because an initial Adams-Stokes attack in the patient with congenital complete atrioventricular (A-V) block may sometimes prove fatal, there is a need to be able to identify the patient at great risk of having such attacks. Twenty-four children with congenital complete A-V block were followed up for 1 to 19 years to determine the efficacy of current methods of predicting risk for Adams-Stokes syncope and the usefulness of pacemaker therapy in relieving symptoms. The heart rate at rest, configuration of surface electrocardiographic complexes, data obtained during intracardiac electrophysiologic study and response to graded treadmill exercise testing were compared in children with and without syncope. One or more Adams-Stokes episodes were experienced by eight children, one of whom died. Only a persistent heart rate at rest of 50 beats/min or less demonstrated any significant (probability [p] < 0.01) correlation with the incidence of syncope. Intracardiac electrophysiologic study was of little benefit because the site of block did not correlate with syncope. Although the increase in heart rate during treadmill exercise testing showed no correlation with prevalence of syncope or location of block, exercise-induced ventricular ectopic beats may have predictive value in older children and young adults.

Ventricular pacemakers were implanted in 10 children. Each child was asymptomatic over a 1 to 10 year follow-up period. Because extreme bradycardia may contribute to the prevalence of Adams-Stokes attacks in children with congenital complete A-V block, careful evaluation of heart rate at rest may be an effective means of differentiating patients at risk of syncope. Pacemaker therapy is a feasible and effective method of treatment in young children and relieves symptoms.     

Surgical treatment of supraventricular tachycardia in infants and children

The technique, indications and results of surgical division of accessory atrioventricular connections in 10 infants and children with drug-resistant Supraventricular tachycardia are described. The patients ranged in age from 6 months to 15 years. Four patients had associated congenital heart disease. Division of accessory connections were performed on free wall pathways in nine patients (seven right atrial, two left atrial) and on a septal pathway in one patient. Four patients had both anterograde and retrograde conduction over the accessory connection (manifest Wolff-Parkinson-White conduction) whereas six had only retrograde conduction (concealed Wolff-Parkinson-White conduction). The manifest Wolff-Parkinson-White conduction was abolished by surgical division in all four patients. In 8 of the 10 patients the procedure stopped the attacks of paroxysmal supraventricular tachycardia for follow-up periods ranging from 9 months to 3 $\text{1}\text{2}$ years; no patient receives medication to date.     

Elective mapping and surgical division of the bundle of Kent in a patient with Ebstein's anomaly who required tricuspid valve replacement

A 14 year old girl with Ebstein's anomaly and Wolff-Parkinson-White syndrome without supraventricular tachycardia underwent closure of an atrial septal defect and tricuspid valve commissurotomy. Her postoperative course was complicated by her first episodes of recurrent debilitating paroxysmal supraventricular tachycardia. Severe tricuspid insufficiency with low cardiac output necessitated a repeat intracardiac operation. At reoperation the patient underwent successful tricuspid valve replacement with concomitent cardiac mapping and division of the bundle of Kent. In patients with heart disease requiring intracardiac repair who also have Wolff-Parkinson-White syndrome, elective surgical division of the anomalous bundle is recommended whether or not preoperative attacks of tachycardia have occurred.     

The surgical decision in tetralogy of Fallot: weighing risks and benefits with decision analysis

The preferred management of the symptomatic infant less than 2 years of age with tetralogy of Fallot remains unsettled. In this study decision analysis was used to assess the risks and benefits of three courses of action: (1) primary intracardiac repair; (2) palliative operation in infancy and delayed intracardiac repair; and (3) treatment with propranolol in infancy and delayed intracardiac repair. For each action the likelihood was determined of three possible outcomes for the patient: (1) death, (2) poor surgical result, or (3) good surgical result. Each outcome was associated with an estimated life expectancy. The best action was defined as that resulting in the longest life expectancy. With use of previously reported data and those from experience at one institution, a range of probabilities was estimated for death before operation, surgical mortality, success of propranolol treatment and hemodynamic result of operation. The choice of action was affected most by the mortality of primary intracardiac repair and the likelihood of a good hemodynamic result from intracardiac repair. Less important factors were the outcome of a palliative operation and the likelihood of success with propranolol therapy. It was found that in the institution studied if the mortality rate of primary intracardiac repair is 10 percent or less, intracardiac repair should be performed; otherwise propranolol treatment, which allows delay in intracardiac repair, should be selected. Both alternatives are preferable to palliative operation. With decision analysis, the clinician can use probabilities and life expectancy appropriate to a given clinical setting in determining the best management for the infant with tetralogy of Fallot.     

Effects of verapamil on supraventricular tachycardia in children

Thirteen patients, aged 6 weeks to 16 years, with uncontrolled recurrent Supraventricular tachycardia were given intravenous verapamil in an attempt to abolish an episode of Supraventricular tachycardia. All patients had had intracardiac electrophysiologic studies to define the mechanism of their tachycardia. In seven patients conversion to sinus rhythm occurred after administration of verapamil: Five of the seven had atrioventricular (A-V) nodal reentry as the mechanism of their supraventricular tachycardia; the other two had reentrant tachycardia involving an accessory pathway. Verapamil was effective in abolishing the Supraventricular tachycardia in these patients, probably by prolonging the A-V nodal refractory period and conduction, thus breaking the reentrant circuit. In six patients there was no conversion to sinus rhythm: Four of the six had automatic atrial ectopic tachycardia and two had automatic junctional ectopic tachycardia. Among the four patients with automatic atrial ectopic tachycardia, a junctional escape rhythm developed in one, and second degree A-V block developed in the others. The two patients with junctional ectopic tachycardia had severe symptomatic arterial hypotension after verapamil and required resuscitation with intravenous calcium chloride. In spite of the good response to intravenous verapamil in the seven patients with reentrant tachycardia, only four of the seven could be maintained successfully on long-term oral therapy. The patients who experienced conversion to sinus rhythm with an intravenous bolus dose of verapamil but in whom Supraventricular tachycardia could still be induced with programmed stimulation could not be maintained successfully on oral therapy.It is concluded that verapamil is an effective antiarrhythmic agent that can (1) abolish the acute episode of Supraventricular tachycardia only in cases due to reentrant mechanisms, and (2) be used as an oral medication to prevent recurrences of supraventricular tachycardia in patients in whom the arrhythmia cannot be induced with programmed stimulation after intravenous doses of the drug.     

Spectrum of cardiovascular lesions in mucocutaneous lymph node syndrome: Analysis of eight cases

Eight cases of mucocutaneous lymph node syndrome with cardiovascular complications are described. The clinical presentation in all but one patient conformed to the previously described features of this syndrome. Five patients had cardiac enlargement, six had electrocardiographic abnormalities and three had a murmur of mitral insufficiency. Each of the four patients who died had aneurysms of the coronary arteries, usually associated with organizing thrombi. In addition to involvement of the coronary arteries, the renal, mesenteric, vertebral, splenic, hepatic and iliac arteries were affected in individual cases. One patient required triple aortocoronary bypass surgery and one patient underwent excision of a brachial arterial aneurysm. Further long-term follow-up studies of the patients who have survived the acute stage of the syndrome are indicated to establish the spectrum of late complications and sequelae.     

Electrophysiologic effect of digitalis on sinoatrial nodal function in children

Despite the prevalence of digitalis usage in children, the electrophysiologic effects of digitalis on sinoatrial (S-A) nodal function is unknown in this age group. The purpose of this study was to determine the effect of digitalis on sinoatrial conduction time as well as on S-A nodal automaticity. Ten subjects (mean age 10.5 years) underwent electrophysiologic assessment of S-A nodal function before and 30 minutes after administration of ouabain (0.01 mg/kg). Total S-A conduction time increased in each subject and the mean value after ouabain (182 msec ± 13 standard errors of the mean [SEM]) was significantly higher (P < 0.01) than before (149 msec ± 11). The sinus cycle length was variable after ouabain (P > 0.1). The corrected sinus nodal recovery time also was variable (P > 0.1), decreasing substantially in three subjects. Mechanisms of the effect of digitalis on the S-A node and atrium are proposed and discussed.

It is concluded that digitalis prolongs the S-A conduction time in children with normal S-A nodal function. By prolonging the S-A conduction time, digitalis may artifactually shorten corrected S-A nodal recovery time in some patients.     

Propranolol: the preferred palliation for tetralogy of Fallot

The records of 35 infants with tetralogy of Fallot who received propranolol as palliative treatment to prevent hypoxemic spells were reviewed to examine the effectiveness and safety of this treatment. Propranolol was successful in eliminating spells for at least 3 months in 28 (80 percent) of the patients. Patients in whom the drug failed received a significantly smaller daily dose (1.2 versus 2.6 mg/kg, p <0.01), and were significantly younger when treatment with the drug was initiated (6.1 versus 11.3 months, p <0.05). Further data analysis revealed that drug dose, rather than patient age, was the more significant factor.Cineangiograms of all patients were reviewed to determine if drug success or failure could be related to anatomy of the right ventricular infundibulum, main pulmonary artery or branch pulmonary arteries. There were no significant differences except that the diameter of the proximal right pulmonary artery was smaller in patients in whom treatment with propranolol failed but, even in this measurement, there was overlap between the two groups.Patients in whom propranolol therapy was successful had a delay in operation by a mean of 13.1 months. The only toxic effect was congestive heart failure, which occurred in one patient at a dose of 4.0 mg/kg per day. Intracardiac repair was performed in 16 patients who were receiving propranolol, which was administered up to the morning of operation. There were two operative deaths, neither related to the use of propranolol. It is concluded that (1) propranolol was effective in preventing hypoxemic spells in 80 percent of infants with tetralogy of Fallot. (2) Its effectiveness might have been greater had larger doses been administered. (3) When effective, propranolol delayed surgical intervention by an average of 13 months. (4) Propranolol did not affect surgical mortality of intracardiac repair. Treatment with propranolol (2 to 6 mg/kg per day) is recommended for all small infants with hypoxemic spells due to tetralogy of Fallot.     

Hemodynamic effects of dobutamine in children.

Dobutamine is useful for augmenting cardiovasuclar function in adults. However, no information is available on the action of dobutamine in children. To determine its hemodynamic effects in children, we infused dobutamine into 12 children with congenital heart disease during diagnostic cardiac catheterization. We administered dobutamine in two doses: first 2 and then 7.75 microgram/kg per min for 10 minutes each. We meaured heart rate, cardiac output, systemic and pulmonary arterial, right atrial and pulmonary capillary blood pressures before and during the infusion of dobutamine. Systemic and pulmonary vascular resistances, cardiac index and stroke index were calculated. Cardiac output, cardiac index, stroke volume, stroke index and systemic arterial phasic and mean blood pressures increased sugnificantly (P less than 0.05) and pulmonary capillary mean blood pressure decreased significantly (P less than 0.05) during the infusion of each dose of dobutamine compared with control values. Heart rate, pulmonary and right atrial mean blood pressure and systemic and pulmonary vascular resistance were unchanged with either dose of dobutamine. We noted no adverse effect from the drug.     

Relation of the echocardiographic estimate of left ventricular size to mortality in infants with severe left ventricular outflow obstruction

The relation of left ventricular size, as estimated with echocardiography, to mortality was evaluated in three groups of infants with severe left ventricular outflow obstruction. Group I consisted of 17 patients with combined aortic and mitral stenosis or atresia associated with definite hypoplasia of the left ventricle. Group II consisted of eight patients with the primary diagnosis of severe aortic stenosis. Group III consisted of 12 patients with severe coarctation of the aorta. The left ventricular enddiastolic dimension measured with M mode echocardiography and the cross-sectional area of the left ventricular cavity as seen in the parasternal long axis view of the two dimensional echocardiogram were used as indexes of left ventricular volume.All patients with symptomatic outflow obstruction and a left ventricular end-diastolic dimension of less than 13 mm died in infancy. However, five patients with a hypoplastic left ventricle proved at angiography or at autopsy, or both, were found to have a ventricular end-diastolic dimension of 13 mm or greater. Two dimensional echocardiography showed that the left ventricle in these patients was foreshortened and spherical in shape. The cross-sectional area of the left ventricle of each patient in group I was less than 1.6 cm². This was below the range of cross-sectional areas found in a group of normal infants (1.8 to 3.5 cm² ± 2 standard deviations about the mean). Three patients in groups II and III had a slightly reduced left ventricular area (1.7 cm²) and none of these patients survived infancy.Measurement of the cross-sectional area of the left ventricle is a useful method of determining left ventricular size in infants suspected of having the hypoplastic left ventricle syndrome. Patients who have reduced left ventricular volume as assessed by this technique are at very great risk even if surgical relief of the outflow obstruction is attempted.     

Management of surgical complete atrioventricular block in children

Because there is disagreement concerning the efficacy of and indication for permanent pacemaker implantation in children with postoperative complete (third degree) atrioventricular (A-V) block, experience in the management of this problem at one institution was reviewed. Thirty-four patients with postoperative complete atrioventricular block were identified. They ranged In age from 4 months to 22 years and in weight from 4 to 60 kg and were evaluated from 1 month to 20 years postoperatively.

Complete A-V block developed within 24 hours of operation in 28 of the 34 patients. A permanent pacemaker was implanted in 13 of the 28. Death occurred in 4 of these 13 patients and in 5 of the remaining 15 patients who did not have an artificial permanent pacemaker. Complete A-V block developed later than 1 day (2 days to 4 months) postoperatlvely in 6 of the 34 patients; all 6 of these patients survived, and only 3 required permanent pacemaker implantation.

Intracardiac electrophysiologic studies were performed by 14 of the 34 patients. The site of complete block was above the His bundle in 5, within the His bundle in 2, and below the His bundle in 4; it was undetermined in 3. The results of intracardiac electrophysiologic studies are important in delineating the natural history of surgically induced complete A-V block and in the clinical management of this lesion. Permanent pacemaker implantation is indicated if complete A-V block persists longer than 2 weeks postoperatively and if the site of the block is within or below the bundle of His.