Supraventricular arrhythmias in children.

Sudden death may occur in children with supraventricular arrhythmias. Sick sinus syndrome, particularly if associated with tachycardia, may result in sudden death in children who have had open heart surgery and rarely in children with a normal heart. Children with supraventricular tachycardia rarely die. Only those with junctional automatic tachycardia or Wolff-Parkinson-White syndrome have died. Patients with a short anterograde refractory period may be at risk of sudden death. Surgical division of the accessory connection can prevent sudden death. Digitalis may accelerate atrioventricular (AV) conduction in patients with Wolff-Parkinson-White syndrome and, thus, should be used only after testing in the electrophysiology laboratory. Sudden death due to complete AV block should be preventable using pacemakers. Neonates with a ventricular rate less than 55 beats/min or children with a rate less than 45 beats/min should receive pacemaker therapy because of the statistical probability of death or syncope. Ventricular ectopic beats, particularly if frequent or multiform, may be an indication for pacemaker insertion. Patients with surgical complete AV block that persists for more than 7 to 10 days should receive physiologic pacemakers for the prevention of sudden death and hemodynamic benefit.

Resolution of dilated cardiomyopathy after surgical ablation of ventricular tachycardia in a child.

Sustained tachycardia may be associated with dilated cardiomyopathy that may improve after medical management of the tachycardia. Ventricular tachycardia due to an ectopic focus is uncommon in children and rarely presents as congestive heart failure. This report documents that severe dilated cardiomyopathy in a child was caused by sustained ventricular tachycardia and that, after cryoablation of the tachycardia focus, ventricular function rapidly returned to normal.

Transvenous catheter ablation of a right atrial automatic ectopic tachycardia.

A 10 year old patient with right atrial automatic ectopic tachycardia underwent successful transvenous catheter ablation after endocardial mapping. Tachycardia had been present for 7 years before ablation and associated with development of dilated cardiomyopathy. A single 50 J discharge at the point of earliest atrial activation was followed by the establishment of sinus rhythm that remains at 10 months' follow-up. This case represents the first reported successful catheter ablation of an atrial automatic ectopic tachycardia. Specific anatomic factors favoring successful ablation and improvement in technique are discussed.

Wolff-Parkinson-White syndrome and supraventricular tachycardia during infancy: management and follow-up.

The records of 90 patients with Wolff-Parkinson-White syndrome who presented with supraventricular tachycardia in the first 4 months of life were reviewed. Among these, 63% were male. Structural heart disease was present in 20%, most commonly Ebstein's anomaly. All patients presented with a regular narrow QRS tachycardia, and pre-excitation became evident only when normal sinus rhythm was established. Only one infant had atrial flutter and none had atrial fibrillation. Type A Wolff-Parkinson-White syndrome was most common (49%), with heart disease occurring in only 5% of these patients. In contrast, heart disease was identified in 45% of those with type B syndrome. Initially, normal sinus rhythm was achieved in 88% of the 66 infants treated with digoxin with no deaths. Normal sinus rhythm resumed after electrical countershock in 87% of the 15 infants so treated. Maintenance digoxin therapy was used in 85 patients. The Wolff-Parkinson-White pattern disappeared in 36% of the patients. Four infants died of cardiac causes during the mean follow-up period of 6.5 years. Two of these four infants had congenital heart disease; the third, with a normal heart initially, developed ventricular fibrillation and died from a cardiomyopathy considered related to resuscitation. The remaining infant, with a normal heart, died suddenly at 1 month of age. All were receiving digoxin. A wide QRS tachycardia later appeared in three patients, all with heart disease, one of whom died.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of cardiac pacing after the Mustard operation for transposition of the great arteries.

The most frequent complication of the venous redirection (Mustard or Senning) operation for transposition of the great arteries is cardiac arrhythmia. Drug treatment of tachyarrhythmia often worsens bradyarrhythmia. Pacemakers can now treat both arrhythmias. The technique for implantation of pacemakers after redirection for transposition has changed over time from thoracotomy to subxiphoid to transvenous. Atrial pacing is almost always the mode of choice since the electrophysiologic abnormality is sinus node dysfunction with intact atrioventricular conduction. Twenty-nine patients aged 3 to 19 years (mean 9.6) had implantation of a pacemaker a mean of 5.5 years (range 1 to 14) after undergoing the Mustard operation for transposition of the great arteries. Symptoms referable to bradycardia were eliminated in each case. Four patients who received an antitachycardia pacemaker no longer have symptomatic tachycardia. Four patients have required reoperation, three because of lead problems and one because of traumatic erosion of the pacemaker. Pacemakers provide excellent relief of symptoms after the Mustard or Senning operation. Transvenous atrial automatic antitachycardia pacemakers offer the best combination of ease of implantation and symptomatic relief.

Transcatheter ablative techniques for treatment of the permanent form of junctional reciprocating tachycardia in young patients.

Five patients with medically refractory incessant supraventricular tachycardia due to a posterior septal, slowly conducting accessory connection underwent transcatheter closed chest ablative treatment. The tachycardia characteristics were consistent with the permanent form of junctional reciprocating tachycardia. In each patient the ablative attempts resulted in independent interruption of either the anterograde limb (atrioventricular node-His bundle conduction) or the retrograde limb (accessory connection) of the tachycardia circuit. Permanent retrograde pathway ablation was achieved in only one patient and followed separate permanent transcatheter His bundle ablation. In three of the other four patients the ablation attempt caused temporary interruption of retrograde conduction. Each patient had improved control of tachycardia related to the ablation attempt. Of the five patients, four required pacemaker implantation. With further refinements, selective ablation of the retrograde limb of the tachycardia circuit may be possible. This experience confirms the anatomic independence of the anterograde and retrograde limbs of the tachycardia circuit.

Proarrhythmia, cardiac arrest and death in young patients receiving encainide and flecainide. The Pediatric Electrophysiology Group.

The potential for proarrhythmic responses to the class IC sodium channel-blocking drugs encainide and flecainide has not been well described in young patients. Therefore, data were retrospectively collected from 36 institutions regarding 579 young patients who were administered encainide or flecainide for treatment of supraventricular tachycardias (encainide 86 patients, flecainide 369 patients) or ventricular arrhythmias (encainide 21 patients, flecainide 103 patients) to assess the frequency of proarrhythmia, cardiac arrest and death during therapy (adverse events). The two drugs were similar in regard to efficacy (flecainide 71.4%, encainide 59.8%) and rate of proarrhythmic responses (flecainide 7.4%; encainide 7.5%). However, patients receiving encainide more frequently experienced cardiac arrest (encainide 7.5% vs. flecainide 2.3%, p less than 0.05) or died during treatment (encainide 7.5% vs. flecainide 2.1%, p less than 0.05). Detailed data were provided for 44 patients experiencing one or more adverse events. Patient age, previous drug trials, concomitant therapy and days of inpatient monitoring were similar for patients receiving encainide or flecainide. However, echocardiographic left ventricular shortening before treatment was lower among patients receiving encainide (0.23 +/- 0.09) than among those receiving flecainide (0.34 +/- 0.06, p less than 0.05). Plasma drug concentrations were rarely elevated. Cardiac arrest (12 patients) and deaths (13 patients) occurred predominantly among patients with underlying heart disease, particularly among patients receiving flecainide for supraventricular tachycardia (8.3% vs. 0.3%, p less than 0.001). Fifteen patients with an ostensibly normal heart and normal ventricular function experienced proarrhythmia during treatment for supraventricular tachycardia, but only 3 of the 15 had a cardiac arrest or died. The relatively high incidence of adverse events should be considered when contemplating treatment with encainide or flecainide, particularly among patients with underlying heart disease.

Transesophageal echocardiography detects thrombus formation not identified by transthoracic echocardiography after the Fontan operation.

Transesophageal echocardiography demonstrated six instances of venous thrombus formation in the inferior vena cava, right atrium and caval-pulmonary anastomosis region in four children after a modified Fontan operation. Transthoracic surface echocardiography failed to identify these thrombi in five of the six cases because of the posterior location of the thrombus or imaging interference from surgical hardware. These thrombotic episodes occurred 2 days to 5 years after the Fontan operation in children 25 to 168 months of age. Clinical features of compromised cardiac performance with cyanosis or inadequate perfusion were present during four of the six episodes. In two patients, thrombi occurred around transvenous permanent atrial pacing leads. Therapy to eliminate thrombus included surgery (two cases), anticoagulation with warfarin (three cases) and streptokinase thrombolysis (one case). Disappearance of the thrombus was confirmed by transesophageal study in three of the four cases with follow-up echocardiography. Transesophageal echocardiographic demonstration of atrial and pulmonary thrombi that could not be seen by transthoracic imaging suggests that these thrombi occur with greater frequency in patients who have undergone the Fontan operation than was previously suspected.

Cardiomyopathy and myocarditis in children with ventricular ectopic rhythm.

OBJECTIVE: The objective of this study was to evaluate the histologic features of the myocardium in children with abnormal ventricular ectopic rhythm but a structurally normal heart. BACKGROUND: Abnormal ventricular ectopic rhythm in children with a structurally normal heart is an uncommon but serious condition. Previous studies in adults with these findings have shown that approximately 10% have "primary electrical disease" and that 40% to 100% of these have abnormal histologic findings. METHODS: Endomyocardial biopsy samples were obtained prospectively in 33 subjects presenting with ventricular ectopic rhythm but a structurally normal heart by physical examination and noninvasive studies. Biopsy specimens were evaluated for histologic changes consistent with dilated cardiomyopathy or myocarditis and these results were compared with noninvasive and invasive clinical findings. RESULTS: Of the 33 subjects, 16 (48%) had normal myocardial histologic features (Group A), 14 (42%) had changes similar to the histologic features seen with idiopathic dilated cardiomyopathy (Group B) and 3 (9%) had lymphocytic myocarditis (Group C). Presenting clinical symptoms, surface electrocardiograms (ECGs), exercise stress testing and electrophysiologic stimulation tests failed to predict the biopsy results. Twenty-four-hour ambulatory ECGs showed a statistical difference between sustained and nonsustained ventricular tachycardia in Group A versus Group B (p less than 0.007), with Group A having more sustained ventricular tachycardia. Left ventricular function measured by fractional shortening on echocardiography did not differ between groups, but left ventricular end-diastolic dimension was greater in the subjects with abnormal histologic findings (Group B) (p less than 0.03). CONCLUSIONS: These results provide evidence that approximately 50% of children with abnormal ventricular ectopic rhythm but a structurally normal heart may have subclinical cardiomyopathy or unsuspected myocarditis.

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.

Surgical management of refractory supraventricular tachycardia in infants and children.

Sixty-seven children underwent attempted surgical correction of refractory supraventricular arrhythmias using a combination of intraoperative electrophysiologic mapping followed by surgical division or cryoablation of an aberrant conduction pathway or atrial ectopic focus. The patients ranged in age from 4 months to 18 years (mean 11.4 years). Fifty-five patients (82%) had an abnormal conduction pathway crossing the atrioventricular junction (Kent bundle). Thirty-six (65%) of these 55 patients had classic Wolff-Parkinson-White syndrome with a delta wave of pre-excitation on the surface electrocardiogram. Nineteen (35%), however, demonstrated only retrograde conduction across the Kent bundle and had a normal surface electrocardiogram when tachycardia was not present. Kent bundles were isolated to the following locations: right anterior or lateral in 19 (34.5%), left posterior or lateral in 22 (40%), posteroseptal in 10 (18%), anteroseptal in 2 (4%) and both right and left in 2 (4%). Follow-up evaluation of as long as 8 years (mean 34.9 months) has shown seven immediate failures and one late recurrence of arrhythmia (14.5%). Recent refinements in technique and the use of cryoablation for septal aberrant pathways have improved these results. There have been two failures (8%) in the last 25 attempts. Twelve patients underwent surgery for an atrial ectopic focus by the following techniques: cryoablation in seven patients, excision in one patient and both excision and cryoablation in four patients. At a mean follow-up of 16.6 months, there was one late recurrence in the group with an atrial ectopic focus.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of atrial automatic tachycardia by ablation procedures.

Sixteen cases of atrial focus tachycardia are described clinically, electrophysiologically and hemodynamically. In each case multiple attempts at drug treatment (average 2.5 drugs) had failed. After delineation of the electrophysiologic mechanism, the patients were treated by surgical removal or cryoablation or catheter electroablation of the focus. In two of four patients catheter ablation was successful and without complication. Surgical treatment was successful in 13 of 14 patients. Left ventricular function, which had been abnormal in 10 patients, normalized in all but 1 patient whose echocardiographic shortening fraction improved from 10 to 27%. There have been no recurrences in a follow-up period of 6 months to 5 years (mean 2.2 years). It is recommended that any atrial automatic focus tachycardia that produces hemodynamic compromise undergo definitive treatment. Patients with chronic tachycardia rates of more than 140 beats/min should be followed up closely.

New approaches to treatment of incessant ventricular tachycardia in the very young.

It was assumed that the availability of new antiarrhythmic drugs and new surgical techniques might allow medical or nonexcisional surgical treatment in many young children with incessant ventricular tachycardia. Fourteen infants and young children less than 5 years of age were evaluated and treated for incessant ventricular tachycardia. Medical treatment was pursued up to the use of amiodarone with a type Ib or Ic antiarrhythmic drug unless the patient became hemodynamically unstable. Patients underwent surgery when these drug regimens failed or when moderate congestive heart failure was present. Seven patients were successfully treated medically and seven underwent surgical treatment. Of those treated surgically, five had cryothermic lesions and two had excisions. Five of the surgically treated patients required temporary additional medical treatment. Follow-up ranged from 12 to 53 months (mean 28). Eleven of the 14 patients are currently not taking any antiarrhythmic medication. No patient required a pacemaker, none received anticongestive medications and none died.

Neurocardiogenic syncope in children with a normal heart.

OBJECTIVES: The purpose of this study was to review the results of investigation and management of children with syncope and a structurally normal heart. BACKGROUND: Syncope is a common clinical problem and has many etiologies. Autonomic testing and, in particular, the tilt/orthostatic test have helped to positively diagnose neurocardiogenic syncope in a high proportion of such patients. METHODS: Patient case notes and autonomic test charts were reviewed in 162 children aged 1 to 20 years (mean age 12.8 years) with syncope. The autonomic test consisted of orthostatic maneuver, carotid sinus massage, diving reflex, Valsalva maneuver and dose response to intravenous boluses of isoproterenol and phenylephrine. Serum levels of epinephrine and norepinephrine were drawn during the orthostatic test. After confirmation of neurocardiogenic syncope, treatment was begun with fludrocortisone and salt, and beta-adrenergic blocking agents were used as a second line of therapy when indicated. RESULTS: The orthostatic test was positive for neurocardiogenic syncope in 100 patients (62%) and negative in 62 (38%). Patients in the former group were older, were more often female and had a diminished response to carotid sinus massage, a higher Valsalva ratio and a higher supine epinephrine level. Both groups showed an increase in epinephrine and norepinephrine levels at 5 min of standing. In the orthostatic positive group at the time of syncope, norepinephrine levels decreased, whereas epinephrine levels increased. Patients in this group were also more sensitive to the vasodilating effect of isoproterenol but not to its chronotropic effects. Eleven patients had cardioinhibitory syncope (asystole > or = 3 s). Of these, three had pacemaker implantation. Fludrocortisone and salt used in 84 patients in the orthostatic positive group produced resolution of symptoms in 55 patients (65%) and improvement in 14 (17%). Ten patients received beta-blockers, with resolution in four and improvement in four. CONCLUSIONS: Patients with orthostatic test-proved neurocardiogenic syncope show evidence of autonomic dysfunction. They also show beta-adrenergic hypersensitivity. Treatment initiated on the basis of the protocol was associated with amelioration of symptoms in the majority of patients.

Management of atrial flutter after the Fontan procedure.

OBJECTIVES: The purpose of this study was to review the management of atrial flutter occurring after the Fontan procedure. BACKGROUND: Atrial flutter occurs frequently after the Fontan procedure and is often hemodynamically poorly tolerated. METHODS: The patients' charts were reviewed for relevant information. RESULTS: Between 1984 and 1992, 18 patients had atrial flutter after the Fontan procedure. The underlying heart defect was tricuspid atresia in nine, mitral atresia in six and double inlet left ventricle in three. All but three patients had undergone previous palliative surgery. The time interval from Fontan operation to atrial flutter was < 1 day to 16 years (mean 3.7 years). Seven had early atrial flutter before leaving the hospital. Electrophysiologic study in 15 showed sinus node dysfunction in 12. Atrial flutter was inducible in all patients, and 13 had > 1 flutter configuration. Digoxin and a variety of other antiarrhythmic agents (mean 2.7 drugs/patient) were tried with poor results. Only digoxin, amiodarone, flecainide and propafenone showed some benefit when used alone or in combination. Antitachycardia pacemakers were implanted in 16 patients (endocardial 14, epicardial 2) and, with drugs, were useful in 8 (50%). Because atrial flutter was resistant to treatment, right atriectomy was performed in three patients (with benefit in two, one death), successful radiofrequency catheter His bundle ablation in one patient and catheter ablation of atrial flutter in three patients (two failed, one partial success). One patient underwent heart transplantation, and two died suddenly. Another died of complications after an elective epicardial pacemaker replacement procedure. CONCLUSIONS: Atrial flutter after the Fontan procedure is difficult to control. Aggressive drug and antitachycardia pacemaker therapy help about half of the patients. When these measures fail, other options, such as atriectomy, His bundle ablation or catheter ablation of atrial flutter, need consideration. The risk of sudden death justifies the use of such aggressive treatment methods.

Atrial tracking (synchronous) pacing in a pediatric and young adult population.

One hundred pediatric and young adult patients underwent implantation of an atrial tracking pacemaker. Seventy-four pacemakers paced in an atrioventricular (AV) sequential mode at the lower rate limit (DDD) while 26 paced in a ventricular demand mode at the lower rate limit (VDD). Five patients required reoperation during follow-up of 1 month to 2.5 years (mean 1.5 years). Six additional patients required programming to ventricular demand (3) or AV sequential (3) pacing, because of development of sinus bradycardia (2), atrial sensing problems (1) or pacemaker-mediated tachycardia (3). Pulse generators that could sense atrial signals less than 1.0 mV and had a programmable atrial refractory period did not require reprogramming out of the atrial tracking mode. No patient developed atrial flutter or fibrillation. Sensing problems during exercise occurred in 37% of the first 60 pacemakers but in none of the last 40, which had improved electronic components. Atrial tracking pacing is feasible in pediatric and young adult patients.

Radiofrequency catheter ablation of incessant, medically resistant supraventricular tachycardia in infants and small children.

OBJECTIVES: This study retrospectively evaluates initial experience with radiofrequency catheter ablation in a group of seven infants and small children with a history of incessant, medically resistant supraventricular tachycardia. METHODS: Before attempted catheter ablation, all patients had had unsuccessful conventional medical therapy (with digoxin or propranolol, or both) and, in addition, each continued to have daily episodes of supraventricular tachycardia while taking amiodarone or a class IC antiarrhythmic agent alone or in combination. The average patient age was 10 months (range 1 to 27) and the average patient weight was 6 kg (range 3 to 13). Electrophysiologic diagnosis included reentrant supraventricular tachycardia in six patients and atrial ectopic tachycardia in one patient. RESULTS: These seven patients underwent a total of nine catheter ablation procedures. The atrial approach to ablation was employed in eight of the nine procedures. Overall, radiofrequency catheter ablation was totally successful in five of the seven patients, partially successful in one patient and unsuccessful in the remaining patient. The combination of radiofrequency catheter ablation and surgical ablation was successful in controlling tachycardia in all patients; with at least 5 months of follow-up study, no patient has had a recurrence of supraventricular tachycardia or reappearance of a delta wave. CONCLUSIONS: Surgical ablation of arrhythmogenic substrates in the pediatric age group, although rarely indicated, has been found in the past to be safe and effective. Our initial experience with radiofrequency catheter ablation in infants and small children demonstrates that this procedure is a promising nonpharmacologic therapeutic alternative to surgical ablation.

Radiofrequency catheter ablation of right ventricular outflow tachycardia in children and adolescents.

OBJECTIVES: The current study reviews the safety and efficacy of radiofrequency catheter ablation for the treatment of right ventricular outflow tachycardia in children and adolescents and describes a modified method for mapping the tachycardia focus. BACKGROUND: Although radiofrequency catheter ablation has proved highly effective for the treatment of supraventricular tachycardia during childhood and adolescence, its application in children with idiopathic right ventricular outflow tachycardia has been limited. METHODS: Six children (mean [+/- SD] age 10.6 +/- 2.4 years, range 6 to 16) with right ventricular outflow tachycardia underwent seven radiofrequency catheter ablation procedures. The mean tachycardia cycle length was 323 +/- 24 ms (range 300 to 360). Two multipolar catheters were positioned in the right ventricular outflow tract to map the tachycardia focus. RESULTS: Radiofrequency catheter ablation was successful in five (83%) of the six children (95% confidence interval 36% to 99%). At successful ablation sites, local endocardial activation time preceded the surface QRS onset by 46 +/- 5 ms (range 37 to 57), and there was concordance of the 12-lead pace map and the electrocardiogram (ECG) in 11 (one patient) to 12 ECG leads (four patients). One patient developed complete right bundle branch block during radiofrequency catheter ablation. There were no additional complications and no clinical recurrences over a mean follow-up period of 12.7 +/- 3.8 months (range 9 to 22). CONCLUSIONS: These results suggest that radiofrequency catheter ablation is a safe and effective treatment for right ventricular outflow tachycardia during childhood and adolescence. In addition, tachycardia mapping may be enhanced by use of a multipolar right ventricular outflow catheter technique.

Effect of ouabain on the anterograde effective refractory period of accessory atrioventricular connections in children.

The anterograde effective refractory period of the accessory connection was determined before and after the administration of ouabain (0.015 mg/kg intravenously) during electrophysiologic studies in 21 patients with Wolff-Parkinson-White syndrome. The mean age (+/- standard deviation) was 10 +/- 2 years (range 1 month to 31 years). Each patient had stopped taking all cardiac drugs for more than 36 hours. Determination of the anterograde effective refractory period of the accessory connection was made using the atrial extrastimulus technique. A change in the anterograde refractory period of the accessory connection was defined as an increase or decrease of greater than 10 ms from the value before ouabain administration. The post-ouabain anterograde effective refractory period of the accessory connection increased in 2 (9%) of the 21 patients, decreased in 9 (43%) and was unchanged in 10 (48%). This study demonstrated a decrease in the anterograde effective refractory period of the accessory connection of 43% of patients with Wolff-Parkinson-White syndrome after the administration of ouabain.

Prevention of sudden death after repair of tetralogy of Fallot: treatment of ventricular arrhythmias.

The majority of sudden deaths after repair of tetralogy of Fallot have been presumed to be due to ventricular arrhythmia; however, it remains to be demonstrated that antiarrhythmic medication reduces the incidence of sudden death. Since 1978, ventricular arrhythmias have been treated aggressively; these include any ventricular arrhythmia on routine electrocardiogram and more than 10 uniform premature ventricular complexes per hour on 24 hour electrocardiogram. A review was undertaken of 488 patients followed up for more than 1 month after repair of tetralogy of Fallot (mean follow-up time 6.1 years); 13.5% had ventricular arrhythmia on routine electrocardiogram. Ventricular arrhythmia appeared from 2 months to 21 years postoperatively (mean 7.3 years). Ventricular arrhythmias were significantly (p less than 0.01) related to: longer follow-up duration, older age at follow-up, older age at operation and higher postoperative right ventricular systolic and end-diastolic pressures. Ventricular arrhythmia on routine electrocardiogram occurred in 100% of those who later died suddenly compared with 12% of those who did not die (p less than 0.01). Treatment for ventricular arrhythmia was given to 46 patients and considered "successful" if there were fewer than 10 uniform premature ventricular complexes per hour on 24 hour electrocardiogram. A successful drug was found in 44 of the 46: 30 of 34 given phenytoin, 6 of 9 given propranolol, 1 of 7 given quinidine, 1 of 2 given disopyramide, 8 of 9 given mexiletine and 4 of 5 given amiodarone.(ABSTRACT TRUNCATED AT 250 WORDS)