Electrophysiologic cardiac function before and after surgery in children with atrioventricular canal.

Thirty-two children with atrioventricular (AV) canal underwent electrophysiologic studies: 18 underwent preoperative studies at a median age of 3 years (range 6 months to 16 years); 14 underwent postoperative studies at a median age of 4 years (range 2 to 19); and 2 underwent both preoperative and postoperative matched studies. In the preoperative group the following abnormalities were observed: first-degree AV block in 5 patients (due to internodal conduction delay in 1, AV nodal conduction delay in 2 and normal intracardiac intervals in 2); internodal conduction delay but normal PR interval in 4; and disease of the sinus node in only 1. In the postoperative group the following abnormalities were observed: first-degree AV block in 9 (due to AV nodal conduction delay in 2, His-Purkinje system conduction delay in 1, upper normal intracardiac intervals in 3 and unidentified in 3); prolongation of the right ventricular apical activation time in 11 of 13 with right bundle branch block; abnormal sinus node function in 3; and abnormal AV nodal function in 4 (1 of whom had associated sinus node disease). Atrial and ventricular functions were normal in all preoperative and postoperative patients. Electrophysiologic dysfunction is rare in preoperative patients with AV canal; in postoperative patients electrophysiologic abnormalities occur in 38% and involve the sinus and AV nodes in 19 and 25%, respectively.

Anomalous origin of the left anterior descending coronary artery from the pulmonary artery.

Three children were identified as having anomalous origin of the left anterior descending coronary artery (LAD) from the pulmonary artery (PA). Two had had congestive heart failure in infancy with clinical diagnosis of endocardial fibroelastosis and all had abnormal ECGs. The correct diagnosis was delayed in each case, and two patients required selective coronary angiography. Surgery was accomplished in the three children although ECG abnormalities have persisted and one child has dyskinesis of the left ventricular apex. Because this diagnosis may be difficult to make when intercoronary anastomoses are inadequate to outline the left anterior descending coronary flow into the PA, patients with clinical findings suggestive of anomalous coronary artery may require selective coronary studies to exclude this anomaly.

Induction of nonsustained atrial flutter by programmed atrial stimulation in children: incidence, mechanisms, and clinical implications.

Nonsustained atrial flutter was induced by programmed atrial extrastimulation in 6 (4%) of 137 children with preoperative congenital heart defects, who underwent electrophysiologic evaluation as part of cardiac catheterization. None of these patients had ECG or clinical evidence of arrhythmias. Atrial reentry was induced by programmed atrial extrastimulation in these six patients at coupling intervals slightly longer than the coupling interval at which flutter was induced. The flutter cycle length was similar to the atrial refractory periods. The duration ranged between 0.4 second and 60 seconds. The PA interval and the duration of the P wave were normal in all of the patients. Five of the six had normal PR intervals. It is concluded that nonsustained atrial flutter may be induced by programmed atrial extrastimulation in dysrhythmia-free children. The cycle length is determined by atrial refractoriness and, contrary to adults with clinical atrial flutter, prolonged PA and P wave duration are not predisposing factors.

Benign nature of atrial dissociation in pediatric patients.

Atrial dissociation is defined electrocardiographically by the presence of an ectopic atrial rhythm depolarizing independently of the basic sinus rhythm, and is characterized by entrance and exit block. Atrial dissociation is most often observed as an ominous sign in adults with severe myocardial dysfunction. We have observed atrial dissociation in 3 pediatric patients, aged 5 to 22 years, who were essentially asymptomatic from this arrhythmia. All 3 patients are well, without therapy for atrial dissociation, during a follow-up period of 1 to 5 years. The benign nature of atrial dissociation in the pediatric patient as compared with the adult is stressed.

Right ventricular apical activation time in children. Reference standards for clinical use.

To differentiate proximal from peripheral right bundle-branch block, several investigators have used the right ventricular apical (RVA) activation time, but there is a lack of reference standards for infants and other children. Using intracardiac electrography, His bundle and RVA electrograms were recorded in 123 children before surgery for various types of congenital cardiac malformations. None had evidence of conduction defects on their surface ECG. The average RVA activation time was 15 +/- 7 msec (+/- SD) linearly increasing with age from infancy to adolescence. The values found in this large population may be useful as reference standards for right bundle-branch conduction times in other infants and children.

Left isomerism and complete atrioventricular block: a report of six cases.

Six children, aged 12 days to 13 years, with left isomerism and complete atrioventricular (A-V) block are presented. In all six patients the diagnosis of left isomerism was suggested by an interrupted inferior vena cava found during cardiac catheterization and angiocardiography; four patients had complex heart disease consisting of endocardial cushion defect, five had a common atrium, three had pulmonary stenosis, three had patient ductus arteriosus and two had dextrocardia. Further anatomic abnormalities included situs inversus of the viscera (four patients) as well as partial malrotation of the bowel. Of the six patients, four had congenital complete A-V block, whereas the remaining two had A-V conduction disturbances documented during early infancy that progressed to complete A-V block later in life. All six patients required pacemaker implantation and five of the six patients died. This report discusses the clinical presentation of complete AV block and left isomerism and reviews the literature.

Echocardiographic assessment of right bundle branch injury after repair of tetralogy of Fallot.

Nineteen patients, ages 3 1/2-18 years, with electrocardiographic evidence of right bundle branch injury after intracardiac repair of tetralogy of Fallot, underwent invasive intracardiac electrophysiologic evaluation 1-13 years (mean 4.4 years) postoperatively. Categorization of the site of right bundle branch injury as proximal or distal was made by determining the V-RVA interval. In 11 of the patients, the V RVA interval was prolonged (> 35 msec), indicating proximal right bundle branch injury and in the other eight it was normal (< 35 msec), indicating distal bundle branch injury. Within 24 hours of the study, all patients were studied by M-mode echocardiography. Measurements were made of the tricuspid valve closure, mitral valve closure and the difference between the two, or the delta value. All but one patient with distal bundle branch injury had delta values of less than 40 msec (range 8-38 msec), while 10 or 11 patients with proximal bundle branch injury had delta values greater than 40 msec (range 41-116 msec). there was a significant positive correlation (r = 0.74, p < 0.001) between V-RVA and the delta value. We conclude that the delta value is an indicator of relative activation delay of the right ventricle, and therefore, in most cases, proximal vs distal bundle branch injury can be diagnosed noninvasively.

Age-related differences in the protein binding of quinidine.

The in vitro serum protein binding of quinidine was determined in 26 pediatric patients. Group I consisted of 6 cord blood samples obtained at the time of delivery, group II of 8 infants aged 8-18 months, and group III of 12 children over the age of 2 years. The percentage of free quinidine in group I was 39.2 +/- 10.8, group II 24.4 +/- 10.6 and group III 16.6 +/- 6.5, demonstrating a larger proportion of unbound quinidine in the newborn group and an increase in protein binding with age (p less than 0.0001). Therefore, the protein binding of quinidine is diminished in the neonate and young infant and may result in enhanced quinidine activity.