AV node reentry tachycardia in infants.

The purpose of this study was to determine the frequency of atrioventricular (AV) node reentry tachycardia in infants undergoing transesophageal electrophysiological study for paroxysmal tachycardia. The records of all 52 infants < 1-year-old with structurally normal hearts who underwent transesophageal study for paroxysmal tachycardia over a 3-year period were reviewed. Those with a diagnosis of AV node reentry tachycardia underwent complete data review, and follow-up of > 12 months was obtained. Six of 52 infants had a diagnosis of the common type of AV node reentry tachycardia. Tachycardia was diagnosed at a mean age of 2.1 months (range 1 day to 10 months), and 3 of 6 underwent transesophageal study within the first month. Although no patient had structural heart disease, three patients had significant noncardiac disease. Follow-up of 15-38 months (mean 24 +/- 7.8) revealed recurrences in 2 of 6 patients. The mean tachycardia cycle length was 240 ms (range 200-310 ms), and the transesophageal ventriculoatrial intervals ranged from < 30 to 55 ms. All patients had a inducible reentrant tachycardia with a ventriculoatrial interval that remained constant even when tachycardia cycle length increased following verapamil or adenosine administration, or decreased following isoproterenol infusion. Five of 6 had evidence for discontinuous AV node conduction curves. In our patients the substrate for AV node reentry tachycardia was present early in life, and AV node reentry tachycardia can be a clinical problem even in the newborn period.

Therapeutic and diagnostic utility of adenosine during tachycardia evaluation in children.

Adenosine has become the drug of choice for termination of regular, normal QRS tachycardia. Initial studies in adult and pediatric patients have shown that the drug is effective for tachycardias using the atrioventricular (AV) node as an integral part of the tachycardia circuit and has few serious side effects. Experience with adenosine administration in children was reviewed to examine the diagnostic and therapeutic usefulness, effective dose, and adverse effects of adenosine. Adenosine was administered to 38 children during 50 separate electrophysiologic evaluations. Eleven patients had structural or acquired heart disease. Tachycardia mechanisms included orthodromic-reciprocating tachycardia using an accessory AV connection (23 patients), primary atrial tachycardia (6 patients), AV node reentrant tachycardia (3 patients), ventricular tachycardia (2 patients), postoperative junctional tachycardia (1 patient), and antidromic-reciprocating tachycardia (1 patient). Adenosine successfully terminated 51 of 53 episodes (96%) of tachycardia using the AV node, 5 of 10 primary atrial tachycardias, 1 of 1 junctional tachycardia, and 1 of 3 ventricular tachycardias. Reinitiation of tachycardia was seen after 16 of 58 successful terminations (28%), reducing the effectiveness to 39 of 53 (74%) for tachycardia requiring the AV node. Average effective dose was 132 micrograms/kg, range 50 to 250 micrograms/kg, and was slightly higher for peripheral (147 micrograms/kg) than for central (120 micrograms/kg) administration. Significant complications occurred in 4 of 38 patients, including atrial fibrillation, accelerated ventricular tachycardia, apnea, and 1 minute of asystole. Although adenosine is useful therapeutically and diagnostically in children with tachycardia, its effectiveness is limited by tachycardia reinitiation and adverse effects. Higher doses may be required for peripheral intravenous administration.

A naturalistic study of 24-hour electrocardiographic recordings and echocardiographic findings in children and adolescents treated with desipramine.

OBJECTIVE: Recent studies assessing cardiovascular effects of desipramine (DMI) in pediatric patients consistently have found small, clinically benign, but statistically significant, increases in heart rate and electrocardiographic (ECG) conduction parameters. However, single, routine ECG recordings cannot fully assess potential infrequent rhythm disturbances. METHOD: We analyzed data from 24-hour ECG monitoring, two-dimensional Doppler echocardiography, and expert clinical cardiac examination of DMI-treated patients. Subjects were 71 children (N = 35) and adolescents (N = 36) receiving long-term treatment (means +/- SD = 1.5 +/- 1.2 years, median = 1.0 year) with DMI (means +/- SD = 3.5 +/- 1.6 mg/kg). RESULTS: Compared with previous observations in untreated healthy children. DMI-treated patients had significantly lower rates of sinus pauses and junctional rhythm, but significantly higher rates of single or paired premature atrial contractions and runs of supraventricular tachycardia. There was an association between DMI serum levels and paired premature atrial contractions, but no other associations were detected. CONCLUSIONS: These findings support the impression from previous ECG studies that DMI-associated cardiac effects in pediatric patients are quite benign. Nevertheless, it remains to be ascertained whether even minor cardiac abnormalities may predict later, evidently rare, adverse cardiovascular effects that may include sudden death.

Telemetric detection of cardiac allograft rejection. Correlation of electrophysiological, histological, and biochemical changes during unmodified rejection.

Intra-abdominal mismatched heterotopic cardiac allograft transplantation without immunosuppression was performed in eight pigs. Postoperatively, daily electrophysiological studies were carried out either with exteriorized temporary epicardial pacing wires (n = 4) or by a telemetrically controlled implanted pacemaker connected to permanent epicardial pacing leads (n = 4). Electrophysiological studies data were correlated with histopathologic and biochemical findings from daily myocardial biopsies. Electrophysiological studies revealed no significant alteration of sinus or atrioventricular node function, refractoriness, or ventricular pacing threshold. However, ventricular voltage amplitude, measured through the electrodes, decreased steadily with time in all donor hearts and was significantly correlated with histopathologic rejection grade (p less than 0.001) and with adenosine 5'-triphosphate (ATP) depletion (p less than 0.001). Ventricular voltage amplitude less than 75% of baseline occurred 4.5 +/- 1.5 days after transplantation, and this decreased voltage amplitude coincided with a moderate to severe (Grade 2 or 3) histological rejection pattern with a sensitivity of 89% (17 of 19) and a specificity of 77% (17 of 22). Similar changes in voltage amplitude were not found in control hearts. Myocardial tissue ATP values fell significantly from control values with early (Grade 1) rejection (p less than 0.05). Evidence for oxygen free radical injury was indicated by a rise in conjugated dienes of free fatty acids; this increase in diene level occurred 4.3 +/- 1.2 days postoperatively and then regressed during the terminal stages.(ABSTRACT TRUNCATED AT 250 WORDS)

Ventricular tachycardia related to transcutaneous pacing.

A 3-year-old child with Haemophilus influenzae endocarditis and aortic route abscesses presented with sudden cardiovascular collapse. During resuscitation, the child was noted to be in complete heart block. Transcutaneous pacing was instituted three times, and ventricular dysrhythmias were associated with each pacing attempt. When pacing was discontinued, the patient spontaneously reverted to complete heart block without ventricular ectopy. An emergency thoracotomy revealed rupture of the aortic route, and the patient died during surgery. Transcutaneous pacing may precipitate serious dysrhythmias; appropriate precautions are recommended.

Noninvasive transcutaneous cardiac pacing in children.

Noninvasive transcutaneous cardiac pacing is an emergency pacing modality with proven benefits for adult patients. During induction of anesthesia for heart surgery, we externally paced 22 children (aged 0.9-17.9 years and weighing 6.96 to 51 kg) using a commercially available device to pace approximately 10 beats per minute faster than the spontaneous heart rate. Three pacing electrode sizes were used (the standard adult size and two specially manufactured smaller sizes). A total of 56 pacing trials were conducted, 53 of which were successful in obtaining capture. A mean output of 63 +/- 14 mA (range, 42-98) at threshold using the large electrodes was comparable to published adult requirements. Lower current outputs were needed with the medium (53 +/- 12 mA; range, 36-92) and small electrodes (51 +/- 11 mA; range, 29-82). In any given patient, the large electrodes required more current (p less than 0.01) to obtain capture, but delivered less current density (p less than 0.01) and exhibited less impedance (p less than 0.01) than the smaller electrodes. The mean threshold energy requirement was 0.12 +/- 0.01 joules/beat regardless of pad size. Output, current density, impedance and energy requirements did not vary with age, weight or chest size. No complications of external pacing were noted. We conclude that noninvasive transcutaneous pacing can be used safely and effectively in children, and that chest size might necessitate the use of smaller electrodes in children weighing less than 15 kilograms.

Results with the Mustard operation in simple transposition of the great arteries 1963-1985.

From May 1963 to December 1985, 329 infants and children underwent repair of simple transposition of the great arteries (TGA) using Mustard's technique. To assess improvement, the patients were separated into two groups by date of operation: Group I, May 1963 to December 1973 (N = 106), and Group II, January 1974 to December 1985 (N = 223). The operative mortality was 11 (10.4%) in Group I and two (0.9%) in Group II. The 10-year actuarial survival rate was 73.4% in Group I and 93.7% in Group II. Baffle complications, similar in both groups, were identified in 81 patients; 19 were major, causing death or requiring reoperation. By latest electrocardiogram, 21 of 45 (46.7%) of Group I patients and 129 of 180 (71.7%) of Group II patients were in normal sinus rhythm. Late ambulatory electrocardiography, however, revealed that a majority of patients had sinus node dysfunction or other dysrhythmias. Right ventricular (RV) angiography revealed definite diminution of RV contractility in 14 (11%) of 126 children. At late follow-up, 113 of 148 (76%) children were in New York Heart Association (NYHA) Class I and 35 of 148 (24%) were in NYHA Class II. Thirty-five (21%) patients were on cardiac medication chiefly for dysrhythmia management. There has been significant improvement in the early and late mortality with the Mustard operation, and serious baffle complications are infrequent. Dysrhythmias continue to be a major problem but the surviving patients are clinically well and relatively few have significant RV dysfunction.

Amiodarone therapy effects on childhood thyroid function.

Thyroid function was systematically evaluated in 15 consecutive children (mean age 13.7 years, range 0.5 to 19.5 years) before and serially during treatment with amiodarone (Cordarone), a potent antiarrhythmic agent. Amiodarone is known to affect thyroid homeostasis by competitive inhibition of 5'-monodeiodinase, which converts L-thyroxine (T4) to triiodothyronine (T3) and reverse T3 (rT3) to 3,3'-diodothyronine (T2), and also by the direct effects of its high iodine content (37% by weight). Clinical and/or biochemical evidence of hypothyroidism occurred in three patients, two of whom required treatment with L-thyroxine. An additional patient had persistent hyperthyroxinemia but no clinical evidence of hyperthyroidism. Results from the patients who remained euthyroid showed characteristic alterations in serum thyroid function tests. These included significant increases in serum T4, rT3, basal thyroid-stimulating hormone and thyroid-stimulating hormone response to thyrotropin-releasing hormone testing. These changes were considered to be compensatory adjustments by the pituitary-thyroid axis to competitive inhibition of 5'-monodeiodinase by the amiodarone. Routine screening of thyroid function is needed to allow early detection of hypothyroidism when these compensations fail to occur.

Atrial flutter in the young: a collaborative study of 380 cases.

As children with cardiac disease grow older, atrial flutter becomes more prevalent. A collaborative study was performed in 19 institutions to determine the clinical characteristics of these children and the factors affecting prognosis. There were 380 patients with one or more electrocardiographically documented episodes of atrial flutter that first occurred between ages 1 and 25 years (mean age at onset 10.3). Episodes of flutter continued to occur for a mean of 2.5 years after the onset. Of the 380 patients, 60% had repaired congenital heart disease, 13% palliated congenital heart disease, 8% unoperated congenital heart disease, 8% an otherwise normal heart, 6% cardiomyopathy, 4% rheumatic heart disease and 2% other lesions. Overall, drugs were effective in eliminating atrial flutter in 58% of patients; specifically, amiodarone and digoxin plus quinidine were effective in 53%, digoxin alone in 44% and propranolol in 21%. Amiodarone was effective in seven (78%) of nine patients. Corrective surgery was performed after the onset of atrial flutter in 66 patients; in 52% the atrial flutter was easier to control or it resolved and in only 4% it was worse. At follow-up (mean 6.5 years), 83% of the patients were alive (49% without atrial flutter and 34% with atrial flutter) and 17% died (10% suddenly, 6% of nonsudden cardiac cause and 1% of noncardiac cause). Cardiac death occurred in 20% of those for whom an effective drug could not be found to eliminate atrial flutter compared with 5% of those who were treated with an effective drug (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Permanent cardiac pacing after open heart surgery: congenital heart disease.

A retrospective review of 6,004 patients who underwent open repair of congenital heart defects revealed that 132 patients (2.2%) required permanent cardiac pacing postoperatively. The indications for pacing were early atrioventricular (AV) block in 55%, late onset AV block in 31%, and sick sinus syndrome in 14%. A ventricular septal defect (VSD) was the most common congenital anomaly present alone or in association with other lesions in 67% of the patients. Atrial surgery accounted for 21% of the patients requiring pacing. Ten-year patient survival was found to be 66% (+/- 6%). Thirty-five percent of the deaths were sudden and unexpected, presumably due to an arrhythmia. Reoperation for pacing system failure has occurred too frequently (12% per year). The most common causes for reoperation were battery failure (44%) and exit block (25%).

Amiodarone treatment of critical arrhythmias in children and young adults.

The majority of sudden cardiac deaths in children occur in patients with prior arrhythmias and an abnormal heart. Amiodarone was given to 39 young patients (35 with an abnormal heart) with arrhythmias unresponsive to conventional treatment. Their age ranged from 6 weeks to 30 years with nine patients younger than 2 years of age. Atrial flutter was present in 16 patients, ventricular tachycardia in 14 patients and supraventricular tachycardia in 9 patients. The most common diagnosis (14 patients) was postoperative repair of congenital heart disease. The dose ranged from 2.5 to 21.6 mg/kg per day (mean 8.2). Elimination of arrhythmia (on 24 hour electrocardiography) occurred in 15 of 16 patients with atrial flutter, 11 of 14 with ventricular tachycardia and 5 of 9 with supraventricular tachycardia. Symptomatic side effects were: rash (three patients), headache (two patients), nausea (one patient) and peripheral neuropathy (one patient); seven patients had asymptomatic corneal microdeposits which normalized in all after the drug was discontinued. No side effects occurred in patients younger than 10 years of age. The following changed with treatment (p less than 0.05): heart rate decreased (three patients with atrial flutter and sick sinus syndrome required pacemaker implantation for bradycardia) and QTc increased; thyroxine (T4) and serum reverse triiodothyronine (T3) increased. During follow-up study (range 6 months to 3 years), 21 of the 39 patients continued to take amiodarone with complete control of arrhythmias, 9 were no longer taking the drug and 9 died (7 nonsudden and 2 sudden deaths). Amiodarone is an extremely effective treatment for infants and children with tachyarrhythmias resistant to conventional treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Digoxin toxicity associated with amiodarone therapy in children.

The addition of amiodarone to digoxin therapy in nine children caused a sharp increase in digoxin serum concentrations (68% to 800%) in the presence of preserved serum creatinine and BUN concentrations. Digoxin half-life was prolonged. Digoxin accumulation could be attributed in part to the decrease in the renal clearance of digoxin resulting from inhibited tubular secretion of the drug and to the reduction in the distribution volume of digoxin caused by amiodarone. Creatinine clearance was not affected by amiodarone. This interaction appears to be more acute in children than in adults, presumably because of the more important role of the renal tubular secretion of digoxin in children. Whenever digoxin and amiodarone therapy are combined, the digoxin serum concentration should be monitored carefully, with appropriate reduction of the digoxin dose.

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.

Congenital stenosis of individual pulmonary veins: clinical spectrum and unsuccessful treatment by transvenous balloon dilation.

Congenital stenosis of the pulmonary veins is a rare but frequently lethal congenital cardiac abnormality. Eight patients with this malformation were diagnosed, evaluated and treated. All eight patients had associated congenital cardiac defects. Two of the eight died, one of sepsis and one after operative pulmonary venoplasty. In three patients who underwent transvenous balloon catheter dilation of the stenosis the procedure provided immediate but transient relief of the stenosis. The prognosis for symptomatic infants with pulmonary vein stenosis is poor and its treatment an enigma.

Exercise assessment of sinoatrial node function following the Mustard operation.

To screen for sinoatrial node dysfunction following the Mustard procedure for transposition of the great arteries, we studied the chronotropic response to graded maximal treadmill exercise in 29 patients at mean 6.7 years after operation. Although 93% of patients had normal resting heart rate (HR), 83% demonstrated significant depression of maximum HR and/or recovery HR after termination of exercise. These findings were similarly present among a subset of 13 patients with normal exercise tolerance. Resting and exercise-induced HR in 10 patients receiving chronic digoxin therapy were no different than in the 19 patients without medication. Sixteen patients with abnormal chronotropic responses to exercise had intracardiac electrophysiologic evaluation which confirmed sinoatrial node dysfunction in nine. Abnormal HR responses did not correlate with clinical symptoms, cardiac arrhythmias, or postoperative hemodynamics. Maximal exercise testing may be a sensitive noninvasive method to identify sinoatrial node dysfunction in postoperative children.