Robert M. Gow

Risk factors for atrial tachyarrhythmias after the fontan operation

OBJECTIVESnThe purpose of this study was to define the incidence and risk factors for atrial tachyarrhythmias after the Fontan operation.nnnBACKGROUNDnAtrial tachyarrhythmias cause morbidity after the Fontan operation. Causative factors may be affected by the type of systemic to pulmonary connection.nnnMETHODSnThe Fontan operation was performed in 270 consecutive patients between 1982 and 1992. The mean age at operation was 7.0 +/- 4.3 years. Direct atriopulmonary connection was used in 138 patients (51%), total cavopulmonary connection in 94 (35%) and right atrial to right ventricular connection in 38 (14%).nnnRESULTSnAtrial tachyarrhythmias were seen early postoperatively in 55 patients (20%), preoperative atrial tachyarrhythmia being the only risk factor. Follow-up was achieved for 228 early survivors (97%) at a mean interval of 4.4 years. There were 20 late deaths. Late atrial tachyarrhythmias were noted in 29% of patients who received an atriopulmonary connection, 14% of those who received a total cavopulmonary connection and 18% of those who received a right ventricular connection (p < 0.02). Significant risk factors as determined by univariate and multiple logistic regression analysis were atriopulmonary connection type (odds ratio 0.40 for total cavopulmonary relative to atriopulmonary connection [p < 0.05] and 0.37 for right ventricular relative to atriopulmonary connection [p = 0.08]), longer follow-up interval (odds ratio 1.32 for each consecutive year [p < 0.002]) and atrial tachyarrhythmia in the operative period (odds ratio 6.31 [p < 0.0001]).nnnCONCLUSIONSnEarly postoperative atrial tachyarrhythmias, length of follow-up and atriopulmonary connection are significant independent risk factors for the presence of late atrial tachyarrhythmias.

Five-year experience with implantable defibrillators in children

Cardioverter-defibrillators were implanted in children aged 4 to 16 years over a 5-year period with no mortality and eventual clinically appropriate shocks in 6 of 11 patients. Both transvenous and epicardial implantable cardioverter-defibrillators were safe and effective in children resuscitated from sudden death or at high risk for sudden death.

Chaotic atrial rhythm in children

Chaotic atrial rhythm (CAR) usually occurs as a sequela of chronic obstructive lung disease in adults. We report the clinical manifestations and response to therapy in nine children with CAR treated predominantly with propafenone or amiodarone. Age at presentation ranged from 1 day to 30 months; six patients were < or = 2 weeks old. Six patients had tachycardia, and three had congestive heart failure. The atrial rate was 200 to 500 (mean 369 +/- 71) beats/min and the ventricular rate 150 to 300 (mean 251 +/- 37) beats/min. Eight patients had cardiac abnormalities. Intravenous drug therapy was not successful in converting CAR to sinus rhythm in any patient. A mean of four (range three to five) drugs was used in each patient; amiodarone and propafenone, alone or in combination, proved most successful. Seven patients were discharged from the hospital: full control was achieved in three (digoxin and amiodarone in two and digoxin, amiodarone, and procainamide in one), good control in three (digoxin, amiodarone, and propafenone in two and digoxin and propafenone in one), and ventricular rate control in one (digoxin, amiodarone, and propafenone). Two neonates with hypertrophic cardiomyopathy died. Long-term follow-up showed that CAR had resolved in five patients but persisted in two. We conclude that CAR remains difficult to control despite the use of newer antiarrhythmic agents but may resolve during long-term follow-up.

Neonatal supraventricular tachycardia: outcomes over a 27-year period at a single institution

Aim: To establish prognosis in neonatal supraventricular tachycardia.

Coarctation of the aorta or subaortic stenosis with atrioventricular septal defect

Thirty patients are reported with atrioventricular (AV) septal defect and either coarctation of the aorta (C of A) or subaortic stenosis (SAS) or both. All patients had normal left ventricles as assessed by angiography (21 of 30 patients) or necropsy (9 of 30). Three groups were recognized. Groups I and II included 19 patients with AV septal defect (12 complete, 7 partial) and C of A with or without SAS, 11 patients with AV septal defect (5 complete, 6 partial) and SAS. In Group I, preductal C of A was diagnosed in 16 of 19 patients. Concomitant angiographic evidence of SAS was present in 2 cases, the mechanism being exaggerated anterior displacement of the left AV valve. In Group III, at the time of diagnosis left ventricular-aortic peak systolic pressure gradients of greater than 20 mm Hg were present in 9 patients, 2 of whom had gradients greater than 50 mm Hg. Angiographic diagnoses were: discrete fibrous diaphragm in 4, fibromuscular obstruction in 5, dynamic tunnel in 1, and chordae from left AV valve to LV outflow tract in 1. Thus, SAS in AV septal defect is most often due to a discrete anatomic lesion. Hemodynamic data show that SAS can be progressive, both before and after the surgical management of the AV septal defect.

904-48 Risk Factors for Venous Obstruction in Children with Transvenous Pacing Leads

To determine the incidence and risk factors for venous obstruction (OBST). we prospectively evaluated with echocardiography 63 of 70 eligible children who had transvenous pacing leads placed between 1985 and 1993. The median (range) age at initial implantation was 7.6 yrs (0.7, 16), and 8 patients had subsequent additional implants. OBST was defined as a combination of Doppler flow abnormalities in the SVC or innominate (InnV) vein and a 2D echo appearance of vessel narrowing and/or the clinical appearance of dilated superficial veins. OBST was noted in 13/63 (21%) patients, with location of OBST at the distal subclavian vein in 5, SVC in 4, InnV-SVC junction in 2, and multiple sites in 2. Venography in 11 of these patients (2 refused) showed that the severity of OBST (as defined by % luminal narrowing) was complete (100%) in 3 patients, severe (g90%) in 4, and moderate (60–90%) in 4. Of the 8 patients who had additional implants, 3 (38%) had OBST. Risk factors for OBST in the remaining 55 single implant patients (10 with OBST; 18%) were explored. Patients with vs. without OBST did not differ regarding date or duration of implant, number of leads, lead material or the presence of associated heart defects Or surgery. Patients with OBST were younger at implant (median 5.6 vs. 8.8 yrs; p l 0.05). Total cross-sectional area of lead(s) was related to body surface area at implant (RATIO). Patients with OBST had higher mean RATIO (7.6xa0±xa01.6xa0mm 2 /m 2 ) than patients without OBST (4.9xa0±xa02.0 mm 2 /m 2 ; pxa0lxa00.0002). After controlling for RATIO in multiple logistic regression, no other variable predicted OBST. Receiver-operator characteristic curves showed a RATIO of g6.6xa0mm 2 /m 2 to best predict OBST, with a sensitivity of 90% and specificity of 84%. Conclusion Since pacing is lifelong, sizing of transvenous leads to the child is important to prevent OBST and preserve venous access.

A Comparison of Two Stab-On Unipolar Epicardial Pacing Leads in Children

The Oscor MP52V and Medtronic 4951 leads have similar construction and intended application. To determine if one of these designs was more suited to pediatric pacing, we reviewed implant, 3 month, and 12 months follow‐up thresholds for all 18 MP52V implants at our institution from December 1989 to April 1991 and compared them to the 4951 implants from fanuary 1982 to October 1989. Lead suirival for tbe MP52V implants was compared to the most recent 36 4951 implants. Patients ranged in ages from 2 days–16 years (median = 4 years) and required antibradycardia pacing for congenital or acquired heart disease. Patients were compared for weigbt and proportion ofatrial leads in each group by t‐test and Fisher exact tests respectively. Energy thresholds were assessed in μJ and compared by t‐test. Lead survival was defined hy abandonment or replacement for any reason. Kaplan 8‐ Meier survival curves were plotted and compared by Gehans Wilcoxan Test There were no significant differences between the MP52V and 4951 groups for age at implant (53 months vs 80 months) or proportion of atrial implants (5/18 vs 11/36). Lead survival was poor but did not differ significantly (70% vs 78% cumulative survival at 3 vears), usuallv failing by exit block. Implant and follow‐up thresholds did not differ significantly between leads. The MP52V did not provide significant improvement in performance over the 4951. New epicardial lead designs are needed to improve lead survival and thresholds in children.

Pharmacokinetics of the active metabolite (MDL 74,156) of dolasetron mesylate after oral or intravenous administration to anesthetized children.

Dolasetron mesylate is a selective 5‐HT3 receptor antagonist under investigation as an antiemetic in children. Published studies indicate that its antiemetic activity results from the active metabolite (MDL 74,156), which is produced within 10 minutes of administration of dolasetron mesylate.

Intravenous and oral propafenone for treatment of tachycardia in infants and children: pharmacokinetics and clinical response.

To elucidate contribution of an active metabolite to overall clinical responses to propafenone, steady‐state disposition of propafenone and its active metabolite and the clinical responses to treatment were examined in pediatric patients receiving intravenous or oral propafenone. There were more than ten‐fold interindividual differences in apparent clearance, resulting in a wide range of the steady‐state trough plasma concentrations of propafenone. The active metabolite, 5‐hydroxypropafenone, was detected in four of the six patients receiving oral propafenone; however, two neonates receiving oral propafenone and all eight receiving intravenous propafenone had no detectable levels of 5‐hydroxypropafenone in plasma. In nine patients for whom electrocardiographic (ECG) data were available, the PQ interval was significantly increased, whereas the QRS duration and the QTc interval were not. There was no close relationship between plasma concentrations of propafenone or 5‐hydroxypropafenone and ECG parameters. Lack of good correlation between serum concentrations and clinical response precludes using a serum‐concentration targeting strategy with propafenone therapy.

Accuracy of surface electrocardiograms for differentiating children with hypertrophic cardiomyopathy from normal children

Most patients with hypertrophic cardiomyopathy have abnormal electrocardiograms. In this study of 37 matched pairs in the pediatric age group, the 12-lead electrocardiogram did not differentiate between affected and normal children reliably enough to allow it to be used as a screening test in the general population.