Neurocardiogenic syncope in children with a normal heart.

OBJECTIVES: The purpose of this study was to review the results of investigation and management of children with syncope and a structurally normal heart. BACKGROUND: Syncope is a common clinical problem and has many etiologies. Autonomic testing and, in particular, the tilt/orthostatic test have helped to positively diagnose neurocardiogenic syncope in a high proportion of such patients. METHODS: Patient case notes and autonomic test charts were reviewed in 162 children aged 1 to 20 years (mean age 12.8 years) with syncope. The autonomic test consisted of orthostatic maneuver, carotid sinus massage, diving reflex, Valsalva maneuver and dose response to intravenous boluses of isoproterenol and phenylephrine. Serum levels of epinephrine and norepinephrine were drawn during the orthostatic test. After confirmation of neurocardiogenic syncope, treatment was begun with fludrocortisone and salt, and beta-adrenergic blocking agents were used as a second line of therapy when indicated. RESULTS: The orthostatic test was positive for neurocardiogenic syncope in 100 patients (62%) and negative in 62 (38%). Patients in the former group were older, were more often female and had a diminished response to carotid sinus massage, a higher Valsalva ratio and a higher supine epinephrine level. Both groups showed an increase in epinephrine and norepinephrine levels at 5 min of standing. In the orthostatic positive group at the time of syncope, norepinephrine levels decreased, whereas epinephrine levels increased. Patients in this group were also more sensitive to the vasodilating effect of isoproterenol but not to its chronotropic effects. Eleven patients had cardioinhibitory syncope (asystole > or = 3 s). Of these, three had pacemaker implantation. Fludrocortisone and salt used in 84 patients in the orthostatic positive group produced resolution of symptoms in 55 patients (65%) and improvement in 14 (17%). Ten patients received beta-blockers, with resolution in four and improvement in four. CONCLUSIONS: Patients with orthostatic test-proved neurocardiogenic syncope show evidence of autonomic dysfunction. They also show beta-adrenergic hypersensitivity. Treatment initiated on the basis of the protocol was associated with amelioration of symptoms in the majority of patients.

Effect of beta-adrenergic stimulation on the QT interval of children with syncope.

The effect of intravenous bolus doses (0.25, 0.5, 1.0 microgram) of isoproterenol on the QT and RR intervals was reviewed in a group of 34 children undergoing autonomic testing for syncope. Twenty-one patients had a positive orthostatic test and 13 were negative. The two groups (positive and negative) were compared. Baseline QT and RR intervals were similar. The RR interval was shortened by isoproterenol in both groups. Isoproterenol shortened the QT interval in the negative group (as seen in normal persons), but produced QT prolongation in the positive group, although neither reached statistical significance when compared to baseline within the respective group. Comparing the values for RR and QT at each dose of isoproterenol (including baseline) between the two groups showed a significant difference in the QT interval after the 1.0-microgram dose of isoproterenol. Thus children with orthostatic positive neurocardiogenic syncope showed a different QT response to beta-adrenergic stimulation. This lends support to the theory of altered beta-adrenergic sensitivity being present in children with neurocardiogenic syncope.

Radiofrequency catheter ablation of incessant, medically resistant supraventricular tachycardia in infants and small children.

OBJECTIVES: This study retrospectively evaluates initial experience with radiofrequency catheter ablation in a group of seven infants and small children with a history of incessant, medically resistant supraventricular tachycardia. METHODS: Before attempted catheter ablation, all patients had had unsuccessful conventional medical therapy (with digoxin or propranolol, or both) and, in addition, each continued to have daily episodes of supraventricular tachycardia while taking amiodarone or a class IC antiarrhythmic agent alone or in combination. The average patient age was 10 months (range 1 to 27) and the average patient weight was 6 kg (range 3 to 13). Electrophysiologic diagnosis included reentrant supraventricular tachycardia in six patients and atrial ectopic tachycardia in one patient. RESULTS: These seven patients underwent a total of nine catheter ablation procedures. The atrial approach to ablation was employed in eight of the nine procedures. Overall, radiofrequency catheter ablation was totally successful in five of the seven patients, partially successful in one patient and unsuccessful in the remaining patient. The combination of radiofrequency catheter ablation and surgical ablation was successful in controlling tachycardia in all patients; with at least 5 months of follow-up study, no patient has had a recurrence of supraventricular tachycardia or reappearance of a delta wave. CONCLUSIONS: Surgical ablation of arrhythmogenic substrates in the pediatric age group, although rarely indicated, has been found in the past to be safe and effective. Our initial experience with radiofrequency catheter ablation in infants and small children demonstrates that this procedure is a promising nonpharmacologic therapeutic alternative to surgical ablation.

Pediatric cardiac pacing.

Cardiac pacing in children has undergone many improvements in the last decade. The differences between adult and pediatric pacing have narrowed. Children are no longer being denied pacemakers because of size. This article discusses techniques for pacing pediatric patients successfully that will allow them to lead normal lives.

Repair of supravalvar aortic stenosis: cardiovascular morphometric and hemodynamic results.

Supravalvar aortic stenosis is associated with normal systolic pressure in the aorta and its branches with the singular exception of the coronary arteries, which are hypertensive. This uncommon lesion has been treated by patch aortoplasty of several types. We examined hemodynamics and morphometrics in 13 patients who underwent operation for supravalvar aortic stenosis from 1979 through 1988. They ranged in age from 2 to 43 years (mean age, 14.5 +/- 3.8 years [+/- standard error of the mean]). There were no operative deaths. Preoperative and postoperative (1 to 5 years) catheterization or echocardiography or a combination of these was done in all but 3 patients (1 died late suddenly without a postmortem examination; 1 was lost to follow-up; and 1 has not yet been restudied). Pressure gradients across the stenosis in patients treated with a single-sinus patch (n = 4) were 65 +/- 18 mm Hg preoperatively and 5 +/- 3 mm Hg postoperatively (p less than 0.05) and in patients with a bisinus patch (n = 6), 83 +/- 15 mm Hg preoperatively and 6 +/- 2 mm Hg postoperatively (p less than 0.05); the two groups were not significantly different. Measurements of the diameters of the coronary arteries, aortic annulus, and descending aorta were made, and calculation of the ratio of the coronary artery and annulus diameters to the descending aortic diameters both preoperatively and postoperatively was possible in 5 patients. The left coronary artery was larger than normal before and after operation. Preoperatively there was a disproportionate increase in left coronary artery and annulus size during systole. Left ventricular wall thickness decreased significantly postoperatively (p less than 0.05). Repair of supravalvar aortic stenosis (localized and diffuse) by both single sinus and bisinus patch repair is safe and hemodynamic results are good.(ABSTRACT TRUNCATED AT 250 WORDS)

Successful treatment of congenital atrial flutter with antitachycardia pacing.

Congential atrial flutter is a condition that rarely requires chronic pharmacological therapy. An unusual case of congenital atrial flutter is described which was resistant to medical therapy, yet responded well to antitachycardia pacing. While most experience with antitachycardia pacing in pediatrics has been with the postoperative congenital heart patient, patients such as the one described with unscarred atria may prove to be the most suitable pediatric candidates for this pacing modality.