Ventricular tachycardia in nonpostoperative pediatric patients: role of radiofrequency catheter ablation.

Experience concerning radiofrequency catheter ablation (RFCA) of ventricular tachycardia (VT) in pediatric patients is limited. In adults, success rates vary widely based on the etiology of the VT. Highest success rates have been achieved in patients without structural heart disease. Between March 1998 and December 1999, five young patients (age, 5 months to 15 years; body weight, 5.5-61.6 kg) underwent RFCA for VT at our institution [structurally normal heart (n = 4), preoperative tetralogy of Fallot (n = 1)]. Monomorphic VT was present in four children, and an infant with MIDAS syndrome had polymorphic VT. Clinical presentation varied: palpitations, n = 2, congestive heart failure, n = 3. All patients had been proven to be unresponsive to one to six (median, three) antiarrhythmic drugs. In all five patients, VT could be successfully eliminated by RFCA after a total of nine (range, 1-4) procedures. Activation mapping and pace mapping were used to identify the anatomical substrate, which was located in the right ventricle/right ventricular outflow tract in all four patients with monomorphic VT and in the left ventricular septum/left ventricular free wall in the infant with polymorphic VT. There were no significant complications in any patient. During follow-up (20-42 months), all patients are in normal sinus rhythm. Left ventricular function recovered in all three patients who had initially presented with congestive heart failure. RFCA can be effective, safe, and life saving in children with medically resistant VT who have not been operated on for congenital heart disease, even when the VT is polymorphic. Although the number of patients is small, RFCA may be the treatment of choice for symptomatic VT in pediatric patients.

A technique for conducting noninvasive cardiac electrophysiology studies in conscious swine.

A noninvasive method was developed in swine for conducting cardiac electrophysiology (EP) studies without the potential confounding effects of sedatives or anesthetics. Following a 1-week conditioning regimen in the EP laboratory, 1-month-old Hanford miniature swine underwent transvenous pacemaker (PM) implantation under isoflurane anesthesia. Two bipolar screw-in pacing leads were inserted into the left external jugular vein, with one positioned in the right atrial appendage and one in the myocardium at the right ventricular apex. The leads were attached to a multiprogrammable pulse generator, and the pacing system was placed in a subcutaneous pocket. At weekly intervals following implantation, conscious, unsedated swine were remained in a sling for noninvasive programmed stimulation (NIPS) using a programmable telemetry system. A NIPS protocol to induce arrhythmias was performed separately for the atrium and ventricle. Data for this model are reported. Complications occurred in 6 of 26 animals studied and included one infection of the PM pocket, three cases of dislodgement of the atrial lead, and rotation of the generator within the pocket in two animals, preventing communication with the PM. This technique has been used to perform EP studies successfully in swine and has been utilized in a variety of studies of the cardiac conduction system.

Lack of proarrhythmia as assessed by Holter monitor after atrial radiofrequency ablation of supraventricular tachycardia in children.

The purpose of this study was to assess the short-term arrhythmogenicity of atrial radiofrequency (RF) ablation lesions in children. Patients with the greatest exposure to RF energy comprised the study group. Holter data on 35 RF ablation procedures in 31 patients with a median age of 13.2 years (range 3 months to 20 years) was retrospectively analyzed. Patients received an average of 19.9 (SD = 13.6) RF lesions, all delivered by an atrial approach. Supraventricular ectopy and ventricular ectopy were compared immediately before and after and 4 to 9 weeks after RF ablation by serial Holter monitoring. Factors thought to possibly predispose patients to a proarrhythmic effect were used to define subgroups for separate analysis. No increase in ambient supraventricular ectopy or ventricular ectopy was observed either immediately after or 4 to 9 weeks after RF ablation compared with the baseline Holter recordings. Children exposed to relatively large doses of RF energy may demonstrate transient and asymptomatic nonsustained tachycardias in the short term. However, no new sustained tachycardias and no increase in supraventricular or ventricular ambient ectopy are detected by short-term Holter monitoring.

Learning curve for radiofrequency catheter ablation in pediatrics at a single institution.

We examined the learning curve for radiofrequency ablation in pediatrics at a single institution. The first 146 cases were retrospectively reviewed, including patients < or = 21 years old with a single tachycardia diagnosis who were undergoing radiofrequency ablation for the first time. Data regarding demographics, electrophysiologic properties of the tachycardia, and procedural characteristics were tabulated. Data were then analyzed for evidence of association between these characteristics, success, and experience. Results revealed that success rates improved significantly with experience, reaching 85% success for all cases after < 100 cases attempted. Success for accessory pathway tachycardias alone reached > 93%. The number of cases of nonpathway tachycardias undertaken significantly increased as experience was gained. Fluoroscopy time improved to 34 +/- 27 minutes after < 100 cases. In conclusion, as experience was gained, (1) success rates showed a steep improvement; (2) the population undergoing radiofrequency ablation clearly shifted to include more difficult diagnoses; and (3) fluoroscopy time significantly decreased.

High-dose narcotic anesthesia using sufentanil in swine for cardiac catheterization and electrophysiologic studies.

A protocol for high-dose narcotic anesthesia using sufentanil by intravenous infusion was developed in swine undergoing cardiac catheterization and intracardiac electrophysiologic studies. In experiments involving cardiac conduction system ablation, nine swine received intramuscular ketamine, 33 mg/kg, and intramuscular acepromazine, 1.1 mg/kg, as premedication. An infusion of sufentanil (15 mcg/kg/h) was started followed by a loading dose of sufentanil (7 mcg/kg) given as a bolus intravenously. A continuous infusion of sufentanil (15-30 mcg/kg/h) was used for maintenance anesthesia. Since the development of this protocol, we have been able to achieve stable hemodynamics and cardiac rhythms for intracardiac electrophysiologic studies.

Subcutaneous lidocaine affects inducibility in programmed electrophysiology testing in children: a follow-up study.

Invasive cardiac electrophysiology testing during cardiac catheterization requires local anesthesia at the point of entry for the catheters. Frequently, lidocaine is employed for this purpose. A prospective study completed in 1990 indicated that subcutaneous administration of lidocaine adversely influenced the inducibility of arrhythmias in pediatric patients. Upon completion of that study, lidocaine concentration was reduced from 1% to 0.5%, and extra caution was taken to avoid deep penetration during administration. A follow-up, prospective study was performed to evaluate inducibility under these changed conditions. Because the depressant effect of lidocaine on inducibility was age- and weight-related, the second study group was required to have statistically indistinguishable age and weight distributions from the first group to eliminate these variables as factors in inducibility. A total of 177 subjects were collected in the second group before a periodic random computer match with the first group produced 99 individuals with the required age and weight distributions. Analysis of the electrophysiology tests in the second study revealed that: (1) incidence of inducibility was higher in the second group (58 of 99 versus 43 of 99, p < 0.05); (2) average lidocaine dose per kilogram was lower (1.8 mg/kg versus 3.28 mg/kg, p < 0.0001); (3) average lidocaine serum concentration was also lower (0.58 micrograms/ml versus 1.47 micrograms/ml, p < 0.0003); (4) in contrast to the first study, neither lidocaine dose nor serum concentration had any effect on inducibility. We conclude that the new procedures for lidocaine administration effectively removed lidocaine as a factor in inducibility.

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.

Oral antidiabetic combination therapy with sulphonylureas and metformin.

In a multicentre trial in general practice, a total of 1823 type 2 diabetics, not adequately controlled by diet and maximal sulphonylurea therapy, were treated with additional metformin 850--2 550 mg/d for 12 weeks. The average postprandial blood sugar decreased from 15.48 mmol/l to 10.43 mmol/l, HbA1 fell from 11.0% to 9.1%. Serum triglycerides decreased from an initial level of 2.87 mmol/l to 2.41 mmol/l an mean total cholesterol from 6.76 mmol/l to 6.16 mmol/l. In addition, body weight and blood pressure declined steadily. All the described changes were statistically significant. The metformin-sulphonylurea combination therapy was generally well tolerated. Gastrointestinal side effects occurred in about 7% of patients, but mainly in the first week of treatment, generally disappearing spontaneous as therapy was continued. Side effects led to a discontinuation of the treatment in 4.2% of patients.

Guar and its effects on metabolic control in type II diabetic subjects.

The effect of guar mini-tablets (5 g t.i.d.) on carbohydrate and lipid metabolism of outpatients with overt diabetes mellitus with glycosuria (is greater than 5 g/24 h) was determined in an open-controlled, randomized, multicenter, crossover study. A 4-wk pretreatment period was followed by a 6-wk treatment period. The treatment period consisted of a 2-wk guar period (treatment period II), which was followed by the wash-out period. The other half of the patients received treatment in the reverse order. Out of 93 patient records, 79 (41 sulfonylurea [SU] and 38 insulin-treated) were suitable for statistical analysis. No relevant weight-reducing effect of guar could be found in both 2-wk treatment periods. At the end of treatment period II, the lowering of the 1-h postprandial values of blood glucose (SU 12%, insulin 10%), cholesterol (SU and insulin 25%) was significant after 2-wk of guar treatment compared with the wash-out period. No clinically relevant changes in the safety laboratory parameters were observed during guar treatment. Side effects were observed in 40 of the 93 patients included in the trial. Treatment had to be discontinued in 11% of the patients due to gastrointestinal side effects. On the basis of our results,guar treatment in combination with sulfonylurea and insulin can be recommended for the improvement of carbohydrate and lipid metabolism.