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.

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.