Biomedical subjects
Publications and source records attributed to R M Gow.
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.
We reviewed 40 infants and young children with VT. Median maximum VT rate was 214 beats/min (range 152 to 375 beats/min). A cause was defined in 20 (50%), the most common being cardiomyopathy or myocarditis in 8 (20%). There were six deaths (15%) related to VT, three of which occurred at diagnosis and in patients less than 1 week old. In 5 of 6 deaths related to VT, a cause was defined. At follow-up, 31 (91%) of 34 survivors did not have VT. The presence of symptoms was a predictor of death related to VT. The outlook for asymptomatic patients and those who survived more than 6 months after diagnosis and who do not have progressive myocardial disease appears good.
To obtain normative data for the childhood signal-averaged ECG (SAECG), we obtained SAECGs in 155 volunteers, aged 5-15 years, using Frank leads and a Fourier transform filter. Unfiltered QRS duration (QRSDU) and filtered QRS duration (QRSDF) were significantly longer in males, and the root mean square of the terminal 40 ms (RMS40) was significantly higher in females. There were no gender differences in the duration of high frequency low amplitude signals < 40 microV (DHFLA). All SAECG variables were significantly related to body surface area (BSA). Regression models were established for SAECG variables. For males, the predicted mean + 1.96 standard deviations (SD) for QRSDF (97.5th centile) ranged from 114 ms at BSA 0.70 m2 to 123 ms at 1.90 m2. For females, the predicted mean + 1.96 SD for QRSDF ranged from 110 ms at BSA 0.70 m2 to 119 ms at 1.90 m2. For males and females, the predicted mean + 1.96 SD for DHFLA ranged from 34 ms at 0.70 m2 to 38 ms at 1.90 m2. For males, the predicted mean - 1.96 SD (2.5th centile) for RMS40 (based on natural logarithm model) ranged from 30 microV at 0.70 m2 to 15 microV at 1.90 m2. For females, the predicted mean -1.96 SD for RMS40 ranged from 42 microV at 0.70 m2 to 20 microV at 1.90 m2. In children 5-15 years of age, both gender and BSA need to be taken into account when interpreting the SAECG.
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After spontaneously acquiring complete heart block, two children presented with torsade de pointes as a result of inappropriate prolongation of the QT interval. Although both remain well following pacemaker insertion, their cases illustrate the importance of QT interval assessment in patients with atrioventricular block, and demonstrate that syncopal episodes, and possibly sudden death, in children with acquired heart block can be due to bradycardia-induced ventricular tachyarrhythmias, rather than extreme bradycardia per se.
Cardiac fibromas in infants and children may present as intramural or intracavitary masses. Total or partial resection as well as transplantation have been reported as treatment for symptomatic patients. We report an infant, diagnosed prenatally, who underwent partial excision of a massive obstructive right ventricular fibroma and creation of a bidirectional cavopulmonary shunt. The palliative approach has allowed the child to be followed up with the option of transplantation should the tumor continue to increase in size.
This review summarizes the clinical aspects of sudden cardiac death in the pediatric population. The scope of the problem is defined by examining findings from autopsy series and from clinical series of survivors of out-of-hospital cardiac arrest. Representative lesions from different etiological categories serve as discussion points.
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.
Nineteen infants < 6 months old who had atrial ectopic tachycardia (AET) were treated with antiarrhythmic drugs. AET was controlled with digoxin in 1 patient, propafenone in 2, digoxin with propafenone in 9, digoxin with amiodarone in 4, and digoxin with propafenone and amiodarone in 2; radiofrequency ablation was performed in 1 drug-resistant case. AET resolved in 14 of 15 infants within 1 year. Drug side effects occurred in 5 patients. We conclude that AET in infants < 6 months old can be successfully treated with antiarrhythmic drugs, and we recommend a three-step approach with digoxin, a class 1C antiarrhythmic drug, and a class 3 drug. Resolution of AET in infants is frequent.
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Cardiac sequelae account for the major morbidity and mortality related to Kawasaki disease, and subclinical myocarditis is a frequent finding. The unusual finding of ventricular arrhythmia in a 2.5-year-old patient during the acute phase of Kawasaki disease is reported. The arrhythmia resolved during empirical treatment with oral steroids.
OBJECTIVE: To review retrospectively a 31-year experience with pediatric cardiac pacing at the University of Toronto, with an emphasis on the changing trends in pacemaker implantation in infants and children. DATA SOURCE: Data were obtained from the pediatric pacemaker follow-up clinic at The Hospital for Sick Children, Toronto, Ontario or from the referring pediatric centre. Follow-up was normally continued until the death of the child or referral to an adult hospital at age 18 years. PATIENT SELECTION: The study comprised 397 children (under 18 years of age) who underwent initial pacemaker implantation at The Hospital for Sick Children between January 1962 and December 31, 1992. Follow-up was 99% complete (five children lost) and ranged from one month to 32 years (mean 6.5 years). DATA SYNTHESIS: The use of endocardial versus epicardial leads increased significantly over time (P < 0.001). In addition, significantly more children receiving pacemakers had sick sinus syndrome (P < 0.001). No difference in survival was found between children paced by endocardial versus epicardial leads or between children paced for sick sinus syndrome versus atrioventricular block. The frequency of exit block, by lifetable analysis, did not differ between children who received epicardial versus endocardial leads. CONCLUSIONS: Guidelines for permanent pacemaker implantation in children continue to evolve as developments in lead technology alter trends in pediatric cardiac pacing.
The effectiveness and safety of intravenous amiodarone in children are not well established. This study reviewed its use in 30 infants and children for life-threatening tachyarrhythmias: 18 patients (19 episodes) with supraventricular tachycardia, and 12 with ventricular tachycardia. Eighteen patients had structural heart defects with arrhythmias that occurred after surgery. The mean loading dose was 5 mg/kg infused over 1 hour, with a starting maintenance dose of 5 micrograms/kg/min. In 18 treatment episodes, amiodarone was used alone or in combination with digoxin. Thirteen patients received amiodarone combined with other antiarrhythmic agents. Intravenous amiodarone was effective or partially effective in 94% of patients, achieving a therapeutic effect in a median time of 1 day (range 1 hour to 5 days). The mean effective maintenance dose was 9.5 micrograms/kg/min (13.7 mg/kg/day), and median treatment duration was 5 days (range 1 to 30). Adverse effects occurred in 18 patients (58%), however none necessitated termination of amiodarone therapy. Potentially significant electrocardiographic abnormalities occurred in 5 patients during combination antiarrhythmic therapy with propafenone. Sinus bradycardia requiring temporary postoperative pacing occurred in 3 patients treated with amiodarone alone. Intravenous amiodarone used alone or in combination therapy is an effective treatment for resistant, life-threatening arrhythmias in infants and children. Combination drug therapy with propafenone must be used cautiously. Potential bradycardia pacing may be necessary during administration of amiodarone after surgery.
OBJECTIVES: The purpose of this study was to define the incidence and risk factors for atrial tachyarrhythmias after the Fontan operation. BACKGROUND: Atrial tachyarrhythmias cause morbidity after the Fontan operation. Causative factors may be affected by the type of systemic to pulmonary connection. METHODS: The 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%). RESULTS: Atrial 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]). CONCLUSIONS: Early postoperative atrial tachyarrhythmias, length of follow-up and atriopulmonary connection are significant independent risk factors for the presence of late atrial tachyarrhythmias.
Transposition complex refers to the reversal of the normal connection of the ventricles to the great arteries, and includes both complete transposition of the great arteries (TGA) and congenitally corrected TGA. Adults with complete TGA usually have had an atrial switch (Mustard or Senning), procedures now abandoned in many pediatric centers in favor of the arterial switch (Jatene). The course and treatment of patients with congenitally corrected TGA is much more variable, depending on which associated lesions are present. Such patients share the tendency to complete heart block, systemic tricuspid AV valve regurgitation, and systemic RV dysfunction. Information about these conditions in adults is urgently needed to reduce our reliance on extrapolation from the pediatric experience.
Twenty-three children and young persons with a congenital long QT syndrome were identified; the median age at the time of referral was 10 years (range 4 days to 19 years) and 14 patients (61%) had a family history of the syndrome. Among the 19 patients with symptoms, the initial symptom was syncope in 13 (69%), aborted sudden death in 5 (26%) and near drowning in 1 (5%). There were three deaths during a combined follow-up period of 67 patient-years (average annual mortality rate 4.5%). Patients who did not respond to therapy with a beta-adrenergic blocker and those who died were significantly younger than the remaining patients at the time of diagnosis (p less than or equal to 0.05 for both). Analysis of 44 treadmill exercise tests performed by 16 patients revealed significant prolongation of the median corrected QT (QTc) interval in response to exercise, with maximal prolongation present after 2 min of recovery (median QTc interval 0.52 s versus a baseline value of 0.47 s, p less than 0.001). Characteristic changes in T wave configuration were noted in 8 of 15 patients on at least one occasion during ambulatory Holter electrocardiographic monitoring, including T wave alternation in two patients, both of whom died shortly afterward. It is suggested that the congenital long QT syndrome is associated with a significant mortality rate in childhood despite the use of conventional therapy in symptomatic patients. Ambulatory Holter monitoring and treadmill exercise testing may be helpful, both in confirming the diagnosis of a long QT syndrome and in monitoring the adequacy of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
A newborn infant is described with complete absence of the leaflets of the aortic valve, interruption of the aortic arch and DiGeorge syndrome. This association has not previously been reported, nor has absence of the leaflets of the aortic valve without other features of left ventricular dysplasia. We discuss the possible influence of severe intra-uterine aortic regurgitation on development of the aortic arch.