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.     

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.     

Twenty-five years of progress in the medical treatment of pediatric and congenital heart disease

In the past 25 years there has been a many-fold increase in the prospect that with early recognition and modern treatment the newborn with critical congenital heart disease will reach adult life in a healthy condition, prepared to earn a living and to function as a spouse and as a parent. Advancements in the medical treatment of congenital heart disease may create less public acclaim than may surgical treatment but many purely medical developments provide the basis for achieving ultimate surgical success and, by judicious use of some forms of medical treatment, operation can be avoided altogether. The eight major contributions to patient care that are discussed in this review and the 35 that are simply listed are merely examples of the many developments that have occurred in the past 25 years. These include: 1) the organization of pediatric cardiology and the contribution of volunteer health organizations, 2) continuing medical education aimed at promoting early diagnosis of congenital heart disease and prompt referral to a cardiac center, 3) advances in the technology of cardiac catheterization, 4) Rashkind's balloon atrial septostomy and other catheter manipulative procedures, 5) pharmacologic manipulation of the ductus, 6) beta-adrenergic blockade for control of a variety of problems, including paroxysmal hypoxemic attacks, certain arrhythmias and relief of symptoms in hypertrophic cardiomyopathy, 7) echocardiography, and 8) advances in arrhythmias, electrophysiologic studies and use of pacemakers.     

Long-term follow-up of patients with malformations for which definitive surgical repair has been available for 25 years or more

The results of long-term follow-up studies of patients with five common congenital heart defects are reviewed. The lesions included are ventricular septal defect, atrial septal defect, patent ductus arteriosus, pulmonary stenosis and coarctation of the aorta. A definitive, rather than palliative, operation has been available for each of these lesions for more than 25 years. Therefore many patients who have undergone operation for one of these lesions are now reaching adulthood.Although most of these postoperative patients live a normal life, many have residuae or sequelae that require close observation or treatment. Other persistent abnormalities of the physical examination, electrocardiogram and chest radiogram are obvious but call for no precaution or treatment. We have drawn on our own experience and the published experience of others to identify those findings and historical factors that best reflect the long-term prognosis of these patients. In addition, recommendations concerning the need for continued prophylaxis against infective endocarditis, and the problems of insurability and employability of these postoperative patients are discussed.     

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.     

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.     

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.     

Prognosis for the newborn with transposition of the great arteries

To determine the prognosis for the newborn with transposition of the great arteries, the clinical course of 112 consecutive neonates with dextro-transposition was reviewed. Patients were managed with balloon atrial septostomy at initial cardiac catheterization, palliative operation if needed in the 1st year of life and Mustard's intraatrial baffle repair.The 1st month of life was the period of greatest risk (8 percent mortality rate). Between balloon septostomy and baffle repair, 14 of 103 patients at risk (14 percent) either died or had a cerebrovascular accident. The mortality rate at baffle repair was 14 percent (10 deaths in 71 patients), and there were 3 late postoperative deaths. Actuarial analysis of the data indicates that with this plan of management, approximately 50 percent of newborns with transposition of the great arteries will survive 5 years with excellent function and an additional 15 to 20 percent will survive with one or more medical handicaps.     

Pulmonary artery sling

Pulmonary artery “sling” indicates the vascular anomaly wherein the left pulmonary artery arises from the right pulmonary artery and traverses between the esophagus and trachea to enter the left lung. Respiratory symptoms may result from compression of the trachea and right mainstem bronchus by the anomalous vessel as well as by associated tracheo-bronchial defects. Six cases are described. The distinctive radiologic features include anterior indentation of the barium esophagogram and a characteristic pulmonary angiogram. Surgery is the usual recommended treatment for life-threatening airway obstruction, but results are often poor. In patients with less severe symptoms the physician's approach may be modified by the presence of associated intracardiac defects and intrinsic airway disease.     

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.     

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.     

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.     

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.     

Stress-induced ventricular arrhythmia after repair of tetralogy of fallot

The combination of ventricular arrhythmias found on routine electrocardiography at rest and elevated right ventricular pressures may be associated with sudden death in patients after repair of tetralogy of Fallot. In this study data were reviewed from 104 patients who underwent treadmill exercise testing with a modified Bruce protocol at a mean age of 13.8 years, an average of 7 years after repair of tetralogy of Fallot. The frequency and form of ventricular arrhythmias as manifested in an electrocardiogram at rest as well as before, during and after treadmill exercise tests were tabulated for each patient. Cardiac catheterizatlon was performed within 1 week of the treadmill test in 82 of the 104 patients and the right ventricular systolic pressure, right ventricular end-diastolic pressure, pulmonary arterial systolic pressure and pulmonary to systemic flow ($\text{Qp}\text{Qs}$) ratio were compared in patients with and without ventricular arrhythmias. In 15 (14 percent) of the 104 patients, ventricular arrhythmia was evident in the electrocardiogram at rest and in 31 (30 percent) it was induced by treadmill exercise; 5 of the 15 with arrhythmia at rest had no arrhythmia during exercise. Compared with the remaining 73 patients, the 31 patients who had ventricular arrhythmias during treadmill testing (1) were older (16.2 versus 12.8 years, p < 0.01, t test) and were tested at a longer interval after repair of tetralogy of Fallot, (2) had greater right ventricular systolic pressure (52.7 versus 41.3 mm Hg, p < 0.005), (3) had greater right ventricular end-diastolic pressure (8.0 versus 6.1 mm Hg, p < 0.001), and (4) had no difference in pulmonary arterial systolic pressure or $\text{Qp}\text{Qs}$ ratio. Uniform premature ventricular complexes were found in 28 patients, multiform premature ventricular complexes in two and ventricular tachycardia in one. Patients whose ventricular arrhythmia appeared with exercise had similar hemodynamic findings to-those whose arrhythmia disappeared with exercise. Two patients, each with elevated right ventricular systolic pressure and multiform premature ventricular complexes, had cardiac arrest at home.It is concluded that (1) treadmill exercise testing is a sensitive method for detecting ventricular arrhythmia in patients after repair of tetralogy of Fallot; (2) ventricular arrhythmia during treadmill exercise is related to abnormal hemodynamic status; (3) multiform premature ventricular complexes, couplets or ventricular tachycardia with exercise testing are highly associated with abnormal hemodynamic status and sudden death; (4) suppression of ventricular arrhythmia with exercise is neither the characteristic nor necessarily the benign response in these patients; and (5) ventricular arrhythmia may be a late developing phenomenon and may increase with longer postoperative intervals. Patients after repair of tetralogy of Fallot should be treated for ventricular arrhythmia detected in the electrocardiogram at rest or during treadmill exercise testing.     

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.