Quantifying and minimizing radiation exposure during pediatric cardiac catheterization.

This study reports findings from evaluations of new technologies to measure radiation exposure during pediatric cardiac catheterization procedures. A strategy of pulsed fluoroscopy and low power settings resulted in significantly lower patient radiation exposure compared to conventional 60 frames/sec, high-power settings during fluoroscopy. During radiofrequency ablation procedures, thyroid and thoracic skin sites outside the direct fluoroscopic field received minimal radiation exposure. Intrathoracic radiation exposure was measured with the use of an esophageal dosimeter. In conclusion, strategies to reduce total radiation exposure should be employed, radiation dose should be measured, and assessment of radiation skin injury should be included in post-catheterization assessment.

The role of radiofrequency ablation for pediatric supraventricular tachycardia.

Radiofrequency ablation has become frontline therapy for many pediatric patients with common supraventricular tachycardia (SVTs). Rather than long-term treatment with medications, radiofrequency ablation offers the possibility of "cure" for certain SVT substrates. The decision to perform radiofrequency ablation should be made after full disclosure with the patient and parents about radiofrequency ablation (RFA) benefits and risk, alternative therapies, and the natural history of the SVT. This paper presents a discussion about the current status of RFA and common pediatric SVTs, as well as, discussing evolving RFA issues and indications.

Saphenous vein homograft: a superior conduit for the systemic arterial shunt in the Norwood operation.

BACKGROUND: Excessive pulmonary blood flow increases ventricular volume work in the face of inadequate systemic cardiac output, low diastolic blood pressure, and inadequate coronary perfusion. Using the smallest available 3-mm polytetrafluoroethylene shunts have been successful, although catastrophic shunt thrombosis has occasionally been observed. To avoid thrombosis with a smaller conduit, saphenous vein homografts (SVG) were used to construct the modified Blalock-Taussig (BT) shunts. METHODS: From January 1998 to April 1999, 25 patients weighing 3.1 kg (3.0 kg or less, n = 9), at a mean age of 8.9 days, underwent stage I Norwood using an SVG BT shunt. Common heart defects were aortic atresia (n = 8), mitral atresia and double-outlet right ventricle (n = 5), and unbalanced AVC (n = 5). Mean BT shunt size was 3.2 mm, with 12 patients having shunts that were 3 mm or smaller. RESULTS: Thirty-day hospital mortality was 8% (2 of 25). No shunt thrombosis was seen, despite banding the BT shunt in 3 patients. One patient had BT revision because of an anatomic issue not directly related to the shunt material. CONCLUSIONS: Excellent results may be achieved using SVG BT shunts in the Norwood operation. This conduit seems less likely to thrombose, both acutely and chronically, allowing the use of appropriately smaller-sized shunts in small neonates.

The medical therapy of cardioinhibitory syncope in pediatric patients.

A small percentage of pediatric patients with neurally mediated syncope will have an asystolic response during upright tilt table testing. The purpose of this study is to evaluate the incidence of asystole during tilt table testing, and to assess the outcome of medical management of such patients. Of 398 patients undergoing evaluation for recurrent syncope between January 1989 and 1994, 18 (4.5%) experienced asystole lasting > or = 5 seconds during baseline tilt test. Patients had experienced a mean of four episodes of syncope, with a mean age at the time of tilt test of 11.1 +/- 4.0 years. The median duration of asystole was 10 seconds (range 5-40 s). Treatment was individualized to increased fluids and salt intake (3 patients), metoprolol (8 patients), pseudoephedrine (4 patients), disopyramide (1 patient), or combination therapy with fludrohydrocortisone (2 patients). During a median duration of follow-up of 31 months, no additional syncope was experienced by 78% of patients. Recurrent syncope in 4 patients was associated with either noncompliance or discontinuation of therapy in 3 patients; in 1 patient, increasing the dose of metoprolol was effective in preventing recurrences. We conclude that young patients with recurrent syncope and asystole during tilt test may be safely and effectively managed with pharmacological therapy, without resorting to pacemaker implantation.

Evaluation of recurrent pediatric syncope: role of tilt table testing.

OBJECTIVE: To determine the current practice and effectiveness of evaluating recurrent syncope in pediatric patients, and to establish the role of tilt table testing in the evaluation. DESIGN: Retrospective analysis of 54 pediatric patients with the history of syncope referred to cardiologists. Group I consisted of 27 patients examined without tilt table testing; group II consisted of 27 patients whose examination included tilt table testing. RESULTS: Group I had an average of 5.4 studies and group II, 6.6 studies performed per patient. Studies included chest radiograph (16 vs 13), electrocardiogram (24 vs 27), echocardiography (21 vs 27), 24-hour electrocardiogram (14 vs 16), transtelephonic monitor (7 vs 8), electrophysiology study (1 vs 3), complete blood cell counts (11 vs 12), chemistries (10 vs 11), thyroid function test (3 vs 3), neurology consult (12 vs 6), electroencephalogram (12 vs 5), and head computed tomographic scan (5 vs 3). Of the 298 non-tilt studies, the results of only 5 (1.6%) were abnormal. Diagnoses were made in 5 (18.5%) of 27 group I patients (Wolff-Parkinson-White syndrome, 1; conversion reaction, 2; hyperventilation, 1; migraines, 1), whereas diagnosis was made in 27 (100%) of 27 group II patients (neurocardiogenic syncope, 25; conversion reaction, 2). CONCLUSION: An extensive workup is not routinely indicated in syncopal patients with a history consistent with neurocardiogenic syncope. Tilt table testing performed early in the evaluation will increase the probability of a diagnosis, and will often prevent the need for further extensive, expensive anxiety-producing tests.

Efficacy of alpha-adrenergic agonist therapy for prevention of pediatric neurocardiogenic syncope.

OBJECTIVES: The purpose of our study was to determine whether alpha-adrenergic agonist therapy could prevent neurocardiogenic syncope in pediatric patients. BACKGROUND: Recent reports from adult patients suggest that withdrawal of alpha-sympathetic stimulation contributes to neurocardiogenic syncope. METHODS: Sixteen young patients (mean age 13.1 years, range 7 years 10 months to 17 years 10 months) with recurrent syncope and a positive baseline head-up tilt response were studied. After a positive baseline tilt response, phenylephrine was infused and repeat tilt was performed for 30 min or until the test result was positive. At discharge, patients were followed up on a regimen of oral pseudoephedrine to evaluate treatment effectiveness and side effects. RESULTS: During baseline tilt, seven patients experienced vasodepressor syncope, seven had mixed vasodepressor-cardioinhibitory syncope and two had cardioinhibitory responses. All patients became symptomatic, reproducing their clinical symptoms. Baseline mean arterial pressure decreased slightly immediately on tilt testing and significantly at the end point (82 +/- 13 vs. 77 +/- 18 vs. 30 +/- 14 mm Hg, respectively, p < 0.0001). Although heart rate varied, the changes were not statistically significant (78 +/- 17 vs. 105 +/- 19 vs. 87 +/- 46 beats/min, respectively, p = NS). Phenylephrine was infused (mean 1.74, range 0.6 to 3.0 micrograms/kg per min) as patients underwent follow-up tilt testing. Fifteen patients remained asymptomatic without hemodynamic changes; the remaining patient manifested a blunted mixed response. During phenylephrine infusion, heart rate (64 +/- 12 vs. 81 +/- 17 vs. 76 +/- 16 beats/min, respectively, p = NS) and mean arterial pressure (96 +/- 15 vs. 83 +/- 19 vs. 80 +/- 18 mm Hg, respectively, p = NS) did not change. During outpatient oral pseudoephedrine treatment (mean 11.7, range 6 to 14) 15 of 16 patients reported that their clinical condition was controlled without side effects. CONCLUSIONS: Alpha-adrenergic stimulation prevents pediatric neurocardiogenic syncope. Intravenous phenylephrine prevents neurocardiogenic syncope during head-up tilt, despite reflex vagal bradycardia. Oral pseudoephedrine alleviates symptoms in patients with neurocardiogenic syncope without causing significant side effects.

Effects of venovenous extracorporeal membrane oxygenation on cardiac performance as determined by echocardiographic measurements.

We evaluated the effects of venovenous extracorporeal membrane oxygenation (ECMO) on cardiac performance by echocardiographic measurements in 15 infants. Heart rate and blood pressure were also recorded. Echocardiographic measurements included aortic and pulmonary peak blood flow velocities, pulmonary time to peak velocity, left ventricular shortening fraction, velocity of circumferential fiber shortening corrected for heart rate, and peak systolic wall stress before, during, and after venovenous ECMO. Pre-ECMO echocardiograms showed borderline or normal indexes of cardiac function. After initiation of venovenous ECMO, all infants had normalization and no infant had deterioration of cardiac performance. The inotropic agents dopamine and dobutamine were decreased from average doses of 12 and 3.6 micrograms/kg per minute, respectively, to 3.7 and 1.3 micrograms/kg per minute, respectively, within 8.8 hours of the institution of venovenous ECMO. During this time the mean arterial pressure remained stable, and the heart rate decreased (169 +/- 21 vs 136 +/- 15 beats/min; p < 0.001). During the course of ECMO there were no changes in left ventricular shortening fraction, velocity of circumferential fiber shortening corrected for heart rate, or aortic peak blood flow velocities. Pulmonary artery peak blood flow velocity (69 +/- 22 vs 92 +/- 28 cm/sec; p = 0.04) and pulmonary time to peak velocity improved (47 +/- 11 vs 65 +/- 16 msec; p = 0.026). We conclude that venovenous ECMO does not have deleterious effects on cardiac performance.

Efficacy of venovenous extracorporeal membrane oxygenation for neonates with respiratory and circulatory compromise.

We report a 12-month experience at Egleston Children's Hospital in Atlanta, Ga., with a protocol under which venovenous extracorporeal membrane oxygenation (ECMO) was used instead of venoarterial ECMO. Fifty-five newborn infants were referred for ECMO, four of whom had disqualifying conditions (all four died). Thirty-one infants were supported without recourse to ECMO, one of whom died. Of the 20 remaining patients, three were placed on a venoarterial ECMO regimen because of our early uncertainty about the efficacy of venovenous ECMO or because of technical constraints. All other patients (n = 17), including three with congenital diaphragmatic hernia, were supported with venovenous perfusion. No patient begun on a venovenous ECMO regimen required conversion to venoarterial bypass. Before ECMO, venovenous patients required an average dopamine dose of 16 micrograms/kg per minute and an average dobutamine dose of 6 micrograms/kg per minute. Of 15 patients studied before ECMO, three had significantly impaired contractility, and all had evidence of pulmonary hypertension on an echocardiogram. Mean blood pressure did not change while heart rate fell from 172 to 146 beats/min during the first 2 hours of ECMO and vasoactive drug doses were reduced. Of the 17 venovenous ECMO patients, 15 (88%) survived. We conclude that neonatal patients with severe hypoxia and substantial circulatory compromise can be effectively supported by venovenous ECMO in most cases.