Dan G. McNamara

Evaluation of left ventricular size and function by echocardiography. Results in normal children.

Left ventricular (LV) size and function were studied by echocardiography in 145 normal children. The LV end-diastolic diameter (EDD) and its percentage change with systole (%percnt;ALVD) were measured and mean velocity of circumferential fiber shortening (Vcf) calculated. The LV pre-ejection period (PEP) and ejection time (LVET) were determined from recordings of aortic valve motion. The EDD increased by approximately threefold during childhood and was best correlated with the log of body weight (r = 0.95) and the log of body surface area (r = 0.96). The mean %percnt;lALVD was 36 ± 4 (SD), and this index of LV function was independent of age and heart rate. Mean Vcf was higher, and the absolute values of PEP and LVET shorter, in younger children with a faster heart rate. The mean ratio of PEP/LVET was 0.31 ± 0.003, and was relatively independent of age (r = -0.41) and heart rate (r = 0.37). The %percnt;ZALVD and PEP/LVET appear to be particularly useful indices of LV function because they remain constant during the course of childhood.

Supraventricular tachycardia in children: Clinical features, response to treatment, and long-term follow-up in 217 patients+

We reviewed the records of 217 children whose first episode of supraventricular tachycardia occurred before 18 years (median age 24 months). There were 112 males and 105 females. Of the 49 with congenital heart disease, SVT began before any operation in 26 and greater than 2 weeks postoperatively in 23. Wolf-Parkinson-White syndrome was present on surface ECG in 47/217 (22%). Congestive heart failure accompanied the first episode of SVT in 38% of the patients who were 4 months of age or younger, and in only 19% of those over 4 months (P less than 0.001). Treatment was successful in stopping SVT within 48 hours in 90/142 (63%). Successful short-term treatment included digoxin 57/184 (68%), cardioversion 12/20 (60%), vagal maneuvers 12/19 (63%), phenylephrine 3/9, and overdrive pacing 4/5. SVT recurred at least once in 83% of all patients. On follow-up (mean 4.6 years), episodes of SVT were still present in 56%. Three patients died--two from incessant SVT and one from a CVA after VSD repair. We conclude that long-term status was difficult to predict, but SVT was present in fewer patients whose age at onset was less than 4 months and in those with unoperated CHD. Early recurrence was not a poor prognostic sign. We recommended treatment for at least one year in all patients with SVT, whether or not the first episode terminates spontaneously.

Dysrhythmias after mustard's operation for transposition of the great arteries☆

Abstract Dysrhythmias after Mustards operation for transposition of the great arteries were studied in 60 patients who survived the operation. Only 3 patients consistently had sinus rhythm after the operation. In 54 patients, low voltage atrial waves having the configuration of sinus P waves were seen at one time or another. The incidence of passive dysrhythmias remained nearly the same during the follow-up period. Eight patients showed at various times a specific pattern designated junctional rhythm with right inferior P axis. The mean P axis was directed downward, to the right and anteriorly, occurring either before or after the QRS complex with fixed PR or RP intervals. The characteristics of the junctional rhythm with right inferior P axis remained during subsequent attacks of supraventricular tachycardias. Whereas the incidence of sinus rhythm gradually decreased, the incidence of active dysrhythmias increased during follow-up study. There were no instances of second or third degree atrioventricular (A-V) block. Wolff-Parkinson-White syndrome, type A, developed and persisted in 1 patient. In 5 patients who died, presumably from rhythm disturbances, the histologie features of the sinoatrial (S-A) nodal area were examined. In a control group of normal hearts and 1 specimen with unoperated upon transposition, the S-A node and artery were readily identified. In the necropsy material from patients with transposition who had recently undergone Mustards operation, S-A nodal tissue was identified but fresh hemorrhage and acute inflammation were seen in and about the node. The S-A nodal artery in the 3 patients who died 4 months or more after operation was nearly or completely obliterated by intimai sclerosis and medial hypertrophy. The S-A node was replaced by dense connective tissue and fatty degeneration.

Mechanisms of cardiac arrhythmias after the Mustard operation for transposition of the great arteries.

To determine the mechanisms of the cardiac arrhythmias frequently seen after the Mustard operation for transposition of the great arteries, intracardiac electrophysiologic studies were performed in 52 children 1 to 8 years after the Mustard operation. Sinus nodal automaticity as judged from the response to rapid atrial pacing was abnormal in 28 of the 52 children. Sinoatrial conduction (conduction of the sinus impulse to the atrium) was found to be abnormal in three of nine patients studied with the atrial extrastimulus method. Conduction of the sinus impulse from the high right atrium to the atrioventricular (A-V) node was abnormally delayed in only 2 of 41 subjects. The low lateral wall of the right atrium was depolarized late in 3 of 11 subjects (including the preceding 2). Two subjects showed delayed A-V nodal conduction and one delayed His-Purkinje conduction. The mechanism of supraventricular tachycardia induced in the laboratory was determined to be sinoatrial nodal reentry in four subjects and atrial muscle reentry in four. Two of the four with atrial muscle reentry had prolonged high right atrium to low lateral right atrium intervals during sinus rhythm. Thus, damage to the sinus node remains the most common cause of arrhythmias after the Mustard operation. In addition, delayed atrial conduction may predispose to atrial muscle reentrant tachycardia.

Stress-induced ventricular arrhythmia after repair of tetralogy of fallot

The combination of ventricular arrhythmias found on routine electrocardiography at rest and elevated right ventricular pressures may be associated with sudden death in patients after repair of tetralogy of Fallot. In this study data were reviewed from 104 patients who underwent treadmill exercise testing with a modified Bruce protocol at a mean age of 13.8 years, an average of 7 years after repair of tetralogy of Fallot. The frequency and form of ventricular arrhythmias as manifested in an electrocardiogram at rest as well as before, during and after treadmill exercise tests were tabulated for each patient. Cardiac catheterizatlon was performed within 1 week of the treadmill test in 82 of the 104 patients and the right ventricular systolic pressure, right ventricular end-diastolic pressure, pulmonary arterial systolic pressure and pulmonary to systemic flow (QpQs) ratio were compared in patients with and without ventricular arrhythmias. In 15 (14 percent) of the 104 patients, ventricular arrhythmia was evident in the electrocardiogram at rest and in 31 (30 percent) it was induced by treadmill exercise; 5 of the 15 with arrhythmia at rest had no arrhythmia during exercise. Compared with the remaining 73 patients, the 31 patients who had ventricular arrhythmias during treadmill testing (1) were older (16.2 versus 12.8 years, p < 0.01, t test) and were tested at a longer interval after repair of tetralogy of Fallot, (2) had greater right ventricular systolic pressure (52.7 versus 41.3 mm Hg, p < 0.005), (3) had greater right ventricular end-diastolic pressure (8.0 versus 6.1 mm Hg, p < 0.001), and (4) had no difference in pulmonary arterial systolic pressure or QpQs ratio. Uniform premature ventricular complexes were found in 28 patients, multiform premature ventricular complexes in two and ventricular tachycardia in one. Patients whose ventricular arrhythmia appeared with exercise had similar hemodynamic findings to-those whose arrhythmia disappeared with exercise. Two patients, each with elevated right ventricular systolic pressure and multiform premature ventricular complexes, had cardiac arrest at home. It is concluded that (1) treadmill exercise testing is a sensitive method for detecting ventricular arrhythmia in patients after repair of tetralogy of Fallot; (2) ventricular arrhythmia during treadmill exercise is related to abnormal hemodynamic status; (3) multiform premature ventricular complexes, couplets or ventricular tachycardia with exercise testing are highly associated with abnormal hemodynamic status and sudden death; (4) suppression of ventricular arrhythmia with exercise is neither the characteristic nor necessarily the benign response in these patients; and (5) ventricular arrhythmia may be a late developing phenomenon and may increase with longer postoperative intervals. Patients after repair of tetralogy of Fallot should be treated for ventricular arrhythmia detected in the electrocardiogram at rest or during treadmill exercise testing.

Heritable Q-T Prolongation Without Deafness

The family, reported on, have a syndrome of prolonged Q-T interval, potentially fatal episodes of ventricular arrhythmias, and normal hearing. The direct familial transmission demonstrated in this pedigree is consistent with an autosomal dominant mode of inheritance. To protect other members of the family from the consequences of ventricular arrhythmia experienced by the irreversibly brain-damaged index patient, a series of physiologic investigations was undertaken on this patient in a search for a suitable prophylactic medical regimen. The attacks of ventricular arrhythmia were found to be precipitated by increase in systemic pressure, sinus tachycardia, and extrasystoles occurring in the supernormal phase of repolarization (R in T syndrome). Propranolol was demonstrated to be an effective agent in preventing the ventricular arrhythmia in the index case and in other family members. Since administration of the beta-adrenergic stimulator isoproterenol did not produce ventricular fibrillation, it is assumed that the action of propranolol in preventing ventricular arrhythmia is not mediated through beta-adrenergic blockade, but through its direct antiarrhythmic properties. The subject experienced no ill effect from the series of investigations.

Surgical Treatment of Ventricular Tachycardia in Infants

VENTRICULAR tachycardia is a rare arrhythmia in infancy,1 , 2 and is usually associated with the long-QT-interval syndrome,3 myocardial disease such as that found in myocarditis, congestive or hype...

Congenital complete atrioventricular block: Clinical and electrophysiologic predictors of need for pacemaker insertion

Because of initial Adams-Stokes attack in the patient with congenital complete atrioventricular (A-V) block may sometimes prove fatal, there is a need to be able to identify the patient at great risk of having such attacks. Twenty-four children with congenital complete A-V block were followed up for 1 to 19 years to determine the efficacy of current methods of predicting risk for Adams-Stokes syncope and the usefulness of pacemaker therapy in relieving symptoms. The heart rate at rest, configuration of surface electrocardiographic complexes, data obtained during intracardiac electrophysiologic study and response to graded treadmill exercise testing were compared in children with and without syncope. One or more Adams-Stokes episodes were experienced by eight children, one of whom died. Only a persistent heart rate at rest of 50 beats/min or less demonstrated any significant (probability [p] less than 0.01) correlation with the incidence of syncope. Intracardiac electrophysiologic study was of little benefit because of site of block did not correlate with syncope. Although the increase in heart rate during treadmill exercise testing showed no correlation with prevalence of syncope or location of block, exercise-induced ventricular ectopic beats may have predictive value in older children and young adults. Ventricular pacemakers were implanted in 10 children. Each child was asymptomatic over a 1 to 10 year follow-up period. Because extreme bradycardia may contribute to the prevalence of Adams- Stokes attacks in children with congenital complete A-V block, careful evaluation of heart rate at rest may be an effective means of differentiating patients at risk of syncope. Pacemaker therapy is a feasible and effective method of treatment in young children and relieves symptoms

Induction of ventricular tachycardia during electrophysiologic study after repair of tetralogy of Fallot

An association among premature ventricular complexes on routine electrocardiogram, elevated right ventricular systolic pressure and sudden death after repair of tetralogy of Fallot was previously reported. To examine this relation further, noninvasive, hemodynamic and invasive electrophysiologic data were studied in 27 patients who had undergone repair of tetralogy of Fallot 7 months to 21 years (mean 1.75 years) previously. Syncope, which had occurred in four patients, was not significantly related to ventricular arrhythmia on rest electrocardiogram, 24 hour electrocardiogram or treadmill test. All four patients with syncope had either nonsustained (two patients) or sustained (two patients) ventricular tachycardia induced at electrophysiologic study. His bundle to ventricle conduction interval was prolonged in two patients and Q to right ventricular apex interval was prolonged in three of the four patients. All four had abnormal anatomic or hemodynamic findings: two had a right ventricular systolic pressure of 70 mm Hg or more, one had right ventricular dysfunction with tricuspid insufficiency and one a septal aneurysm. The 9 patients with induced nonsustained or sustained ventricular tachycardia were then compared with the 15 patients without induced ventricular arrhythmias. Those with ventricular tachycardia had a greater prevalence of: more complex ventricular arrhythmia on 24 hour electrocardiogram (63 versus 0%, p less than 0.001), long His bundle to ventricle interval (44 versus 0%, p less than 0.001), right ventricular systolic pressure of 70 mm Hg or more (56 versus 0%, p less than 0.01) and reduced right ventricular ejection fraction (33 versus 7%, p less than 0.025). It is concluded that: 1) induction of nonsustained or sustained ventricular tachycardia was associated with a history of syncope; 2) all patients at risk for syncope could not be identified by routine electrocardiogram 24 hour electrocardiogram or treadmill test; 3) hemodynamic alterations may interact with intraventricular conduction abnormalities and predispose to ventricular tachycardia.

Transient hypertrophic subaortic stenosis in infants of diabetic mothers

Three newborn infants with congestive heart failure had hemodynamic, angiographic, and echocardiographic features of hypertrophic subaortic stenosis (hypertrophic obstructive cardiomyopathy). Treatment with digitalis and diuretic drugs was ineffective, but improvement occurred when these agents were withheld in one patient, and when treatment with propranolol was begun in two patients. Echocardiography was helpful in establishing the diagnosis in two patients and showed resolution of the condition during the first six months of life. Serial cardiac catheterizations confirmed resolution of the outflow obstruction in the third patient. Family studies revealed no evidence of familial cardiomyopathy, but the mothers of two infants had insulin-dependent diabetes mellitus and the mother of the third was presumed to be prediabetic.