Early results of AV sequential pacing on left ventricular outflow obstruction after Senning procedure

Dual chamber pacing was shown to decrease left ventricular outflow tract (LVOT) obstruction in patients with hypertrophic cardiomyopathy 30 years ago. We report early results of AV sequential pacing from the LV apex in a patient with transposition of the great arteries who is post-Senning procedure. LVOT obstruction resulted from septal deviation and systolic anterior motion of the mitral valve. Pacing was indicated for sinus node dysfunction. AV sequential pacing with a short optimal AV interval of 60 ms demonstrated a 45% reduction in the degree of LVOT obstruction. This article suggests that LVOT obstruction after the Senning procedure can be palliated by asynchronous septal contraction induced by AV sequential pacing, even if the activation is from LV apex, and avoid or postpone surgery in selected situations.

Surgical management of dysrhythmias in infants and small children

Surgery for cardiac dysrhythmias is infrequently reported in infants and children as compared with adults. This report reviews 55 infants and small children (age, less than or equal to 5 years) operated on during the interval July 1, 1984 to December 31, 1991 for Wolff-Parkinson-White Syndrome (41), atrioventricular node reentry (two), atrial automatic tachycardia (two), and ventricular tachycardia (nine). Ages ranged from 3 weeks to 71 (mean, 29) months. Associated congenital heart defects were present in five (10%). Indications for surgery included failure of medical therapy, life-threatening dysrhythmias, and more recently, failure of catheter ablation. There were no hospital or late deaths. One patient sustained perioperative central nervous system injury. Surgery was successful in 52 of 55 (94.5%) (Wolff-Parkinson-White, 38/41 (93%); atrioventricular node reentry, 2/2 (100%); atrial automatic tachycardia, 3/3 (100%); ventricular tachycardia, 9/9 (100%). Ventricular function returned to normal in all 12 patients in whom it was abnormal before operation. Thus, surgical ablation is highly successful in the management of various forms of refractory or life-threatening dysrhythmias in infants and small children. Catheter ablation techniques require significant fluoroscopic time, are more difficult in infants, and as yet do not have adequate long-term follow-up. Accordingly, surgery may continue to play a role in this particular group of patients.

Stability of flecainide acetate in an extemporaneously compounded oral suspension

The stability of flecainide acetate in an oral diluent stored for 45 days under various conditions was studied. A suspension was prepared by triturating 100-mg tablets of flecainide acetate with a commercially available oral diluent. The final theoretical drug concentration was 5 mg/mL. The suspension was poured into 12 2-oz amber glass prescription bottles for a per-bottle volume of 60 mL. Three bottles were refrigerated at 5 degrees C and shaken before analysis, three were stored at room temperature and shaken, three were refrigerated and not shaken, and three were kept at room temperature and not shaken. On days 0, 15, 30, and 45, flecainide acetate concentrations were determined by stability-indicating high-performance liquid chromatography. The concentration of flecainide acetate in the sediment in each bottle was determined on day 46. On day 45, the mean flecainide acetate concentration for each group of bottles remained above 90% of the initial concentration. Mean +/- S.D. flecainide acetate concentrations in sediment ranged from 0.53 +/- 0.30 to 1.18 +/- 0.36 mg per gram. Eight of the 12 samples contained microbial growth on at least one of the test days. Flecainide acetate 5 mg/mL oral suspension was stable for up to 45 days under the conditions investigated.

The effect of exercise on the atrial electrogram voltage in young patients

Atrial electrogram sensing is an important function in active individuals with permanently implanted bipolar dual chamber pacing systems. We undertook to determine the effect of vigorous exercise on the atrial electrogram size in 11 children and young adults (average age 12 years). Using a telemetry signal through a handheld programming wand, nine tracings were completely and clearly recorded for analysis. Six patients had tined/passive fixation atrial leads and three patients had screw-in/active fixation lead systems. All leads were bipolar. The atrial electrogram size for each patient was measured at rest and at each minute of exercise. The atrial electrogram size decreased with exercise from a mean of 5.08 mV to 3.44 mV (range 0.9-4.25 mV) (P = 0.002). The 1.64 mV mean decrease represented a 33.8% reduction (range 19%-56%) (P less than 0.001). There was no difference in the change in atrial electrogram size between the two lead types. Treadmill exercise testing with telemetric data of atrial electrograms showed a decrease in atrial electrogram size produced by exercise and may be helpful in determining appropriate atrial sensitivity settings in selected individuals. Because of the documented decrease in atrial electrogram size produced by exercise, we recommend obtaining maximal atrial electrograms at the time of implant and use of pacing systems that allow maximal flexibility in atrial sensing especially in athletically active individuals.

Adenosine in the pediatric population: nursing implications

Tachydysrhythmias in the neonatal and pediatric age group can present a challenge to pediatric nurses. A new antiarrhythmic drug, adenosine, has proven useful as an acute tool in the termination and diagnosis of these potentially life-threatening dysrhythmias.

The subpectoral pocket: the preferred implant site for pediatric pacemakers

Implantation technique for pediatric pacemaking has evolved from predominantly epicardial to predominantly endocardial. One of the potential problems with endocardial pacing in children is their very thin subcutaneous tissue, which can result in an unpleasant cosmetic result. The superficialness of the pacemaker pulse generator also may render it more susceptible to erosion and infection. A series is presented of pediatric patients who underwent implantation of a transvenous bipolar pacing system in the pediatric catheterization laboratory. The pacemaker was implanted under the pectoralis major muscle after a muscle spreading incision was made. The lead was also introduced into the subclavian vein under the pectoralis muscle. No complications resulted, and the cosmetic result was judged to be good to excellent by the parents and physicians. No infections or erosions occurred. The subpectoral pocket is recommended as the preferred site for implantation of transvenous pacemakers in pediatric patients.

Surgical management of Wolff-Parkinson-White syndrome in infants and small children

Surgical ablation of accessory conduction pathways has rarely been reported in infants and small children with Wolff-Parkinson-White syndrome. In the interval January 1985 to September 1988, 19 infants and children aged 5 or younger have undergone surgical ablation of accessory conduction pathways because of recurrent supraventricular tachycardia. There were 12 (63%) boys and seven (37%) girls. Age ranged from 4 to 66 months (mean 33.8 months). Nine infants were less than 24 months old. Weight ranged from 5.5 to 2.16 kg (mean 13.2 kg). All 19 patients had symptoms, with duration of symptoms ranging from 3 to 63 months (mean 21 months). Accessory conduction pathways were classified preoperatively as left free wall in four (21%), right free wall in nine (47%), and posterior septal in six (32%). No multiple pathways were recognized preoperatively. Left ventricular function was abnormal in four (21%) preoperatively. Free wall pathways (n = 13) were surgically dissected and septal pathways (n = 6) were cryoablated at -70 degrees C. Mean cardiopulmonary bypass time was 60 +/- 4 minutes. Mean crossclamp time was 42 +/- 2 minutes in those undergoing surgical dissection. Mean postoperative stay was 6.4 +/- 0.2 days. There were no deaths, no significant postoperative complications, and no instance of complete heart block. All patients were considered cured at the time of discharge. At a mean follow-up of 12.7 months, 18 (94.7%) remain cured. One patient with Ebstein's anomaly and a right free wall pathway had a recurrent supraventricular tachycardia 3 months postoperatively, and repeat electrophysiologic study has shown a previously unsuspected anterior septal pathway. Ventricular function returned to normal in all four patients who had abnormal function preoperatively. Surgical ablation of accessory conduction pathways can be safely done in infants and small children with results equal to those obtained in adults.

Management strategies for surgical treatment of dysrhythmias in infants and children

To elucidate the role of surgery in the management of refractory pediatric dysrhythmias, the investigators' 1987 experience with this therapy was reviewed. Sixteen patients (8 male, 8 female) had surgery. Age ranged from 3 months to 21 years (mean 7.7 years) with 2 being younger than 1 year of age. Eight patients had Wolff-Parkinson-White syndrome with supraventricular tachycardia (SVT), 6 had SVT alone and 2 had ventricular tachycardia. Patient symptoms fell into 3 distinct categories. Nine patients had frequent non-life-threatening tachycardia episodes despite aggressive medical management, 4 patients had life-threatening symptoms either related to frequent tachycardia episodes or due to side effects of drugs and 3 patients had minimal tachycardia symptoms but were judged to be at risk for sudden death. The mechanisms of the tachycardias included reentrant SVT using an accessory atrioventricular connection in 9, the permanent form of junctional reciprocating tachycardia in 2, atrioventricular node reentrant SVT in 2, atrial ectopic focus in 1 and ventricular ectopic foci in 2. Ablation techniques involved either surgical dissection or cryoablation of the arrhythmogenic substrates. There was no surgical mortality and follow-up shows 15 of 16 patients to have had no recurrence of symptomatic tachycardia without any therapy. Based on this experience, management strategies for surgical control of recalcitrant pediatric dysrhythmias are proposed. Surgery for infant dysrhythmias should be performed only for life-threatening symptoms. Beyond the first year of life, after failing 2 medications, surgical options for SVT should be considered. For patients with ventricular tachycardia, aggressive medical management with class II, IC and III agents should be attempted before surgical therapy.

Problems with permanent atrial pacing in the Fontan patient

Transvenous atrial pacing is the preferred method for control of both brady and tachyarrhythmias in the postoperative pediatric patient with normal atrioventricular conduction. We reviewed our experience with the use of permanent atrial pacing for the control of bradycardia and tachycardia in the Fontan patient. We then compared this pacing experience to atrial pacing data compiled for postop Transposition of the Great Arteries (TGA) patients. Out of twenty-five Fontan patients followed at the Medical University of South Carolina, six patients have had atrial arrhythmias necessitating pacing (24%). Underlying congenital heart disease included tricuspid atresia physiology in three and single ventricle in three. The indications for atrial pacing was brady-tachy syndrome in four patients and sick sinus syndrome in two. Pacers were inserted immediately post-op in three patients and 1.5 years, 2 years, and 8 years post Fontan in the other three. These six patients have required a total of nine pulse generator implantations. Five of the nine pacers were inserted transvenously and four via thoracotomy. In contrast to our experience with permanent atrial pacing in post TGA patients, dysrhythmia control with atrial pacing in the Fontan patient has been more difficult to achieve. The Fontan patients have a higher incidence of symptomatic dysrhythmias, hospitalizations, and antidysrhythmic medication requirements after pacer insertion. Implantation thresholds of the Fontan patients are higher than those of the transposition group. While successful atrial demand pacing is attainable in both groups, antitachycardia pacing is more reliable in the post-op TGA patient. The Fontan procedure seems to present a new set of obstacles for successful atrial pacing in the pediatric post-op patient.

Pediatric transvenous pacing: a concern for venous thrombosis?

Transvenous pacing has become the preferred method of pediatric cardiac pacing. Although no clinically important venous thromboses have been reported, concern has arisen about occult venous thrombosis. We evaluated 19 randomly selected children who had transvenous pacing implants. Sixteen were evaluated by venous plethysmography and Doppler while three had venous angiography and one had both. The leads had all been inserted by subclavian vein puncture. Ages at time of implant ranged from 17 months to 25 years; mean 9.8 years, median 9.0 years. Implant weights were from 9.6 kg to 56.0 kg, mean 31 kg, median 31 kg. The interval from implant to time of procedure ranged from 1 month to 46 months, mean 22.5 months, median 24 months. Four patients had one lead while 14 had two and one had four. Eleven leads were unipolar and 25 were bipolar. The bipolar leads were 6.6 French diameter. In the 19 patients evaluated, no thromboses were detected nor any narrowing greater than 10% of proximal diameter as seen by angiography. No disturbances of blood flow in the subclavian vein was noted. Transvenous pacing did not result in venous flow abnormalities in these pediatric patients.

Neonatal cardiac arrhythmias and their potential role in sudden infant death syndrome

A broad spectrum of dysrhythmias effects neonates. With modern monitoring techniques, we are detecting more of them. Modern treatment techniques should allow virtually all infants to be treated successfully and to lead normal lives.

Flecainide for supraventricular tachycardia in children

The clinical efficacy, adverse effects and pharmacokinetics of flecainide were evaluated in 16 pediatric and young adult patients with supraventricular tachycardia (SVT). Patients had received an average of 2.8 drugs before flecainide was tried. The following mechanisms of supraventricular arrhythmias were determined in patients by intracardiac electrophysiologic studies: atrioventricular node reentry, 4; reentry through an accessory connection, 7; atrial automatic focus, 2; atrial flutter, 3. Twelve patients had normal cardiac anatomy and 4 had congenital heart disease. Each patient received 2.8 mg/kg/day of flecainide divided into 2 doses 12 hours apart. After 3 days, the dose was increased to 5.6 mg/kg/day if necessary. In 14 patients, serum flecainide concentrations measured 3 to 4 days after beginning therapy ranged from 0.1 to 0.8 micrograms/ml (mean 0.40). Flecainide successfully controlled SVT in 8 of 16 patients. SVT in 3 of 7 patients with accessory connections and in 3 of 4 patients with atrioventricular node reentry was successfully controlled. In 1 of 2 patients with atrial automatic tachycardia, SVT had been completely controlled over 16 months. Only 1 of 3 patients treated for atrial flutter responded. Follow-up for successfully treated patients ranged from 4 to 16 months (median 9). Seven patients continue to take flecainide. None of the patients had clinical congestive heart failure. No drug-related adverse effects were noted on the resting surface electrocardiogram. Flecainide rarely produced proarrhythmic effects in this series. The 2 that were observed were mild and caused no clinical problems. Noncardiovascular side effects also occurred infrequently.(ABSTRACT TRUNCATED AT 250 WORDS)