Cardiac rhythm following the Mustard procedure for transposition of the great vessels

Outcomes after Arterial Switch Operation for Simple Transposition

Without intervention, babies born with transposed great arteries (TGA) are doomed to a rapid death. Jatene and coworkers deserve the credit for performing the first successful arterial switch operation (ASO) in a patient with TGA and ventricular septal defect (VSD) in 1975. Since then ASO has become the procedure of choice in most medical centers. This review article summarizes the historical aspects of arterial switch operation and assesses this procedure's outcomes.

Electrophysiologic study of dysrhythmias after atrial operations in dogs

Experiments were conducted with 159 dogs to investigate the mechanism of persistent dysrhythmias clinically encountered after atrial-level operations. Those found after incisions to the internodal pathways (INPs) of the right atrium were analyzed using cardiac mapping in an anesthetized or extracorporeally perfused state. Longitudinal incisions of the posterior INP often allowed inducible sustained atrial flutter, with circus movement of excitation around the right atrium near the tricuspid orfice. Sustained atrial flutter thus produced was modified in cycle length by coexisting division of the middle INP but inhibited by that of the anterior INP. Its incidence increased at chronic stage, with marked cicatricial changes. The disrupted anterior INP markedly prolonged conduction time to the atrioventricular node and A-H interval compared with the other disruptions. Persistent atrioventricular junctional rhythm developed in about 50% of the animals after disruption of all three INPs or anterior and posterior INPs; division of the anterior INP was the common potent factor, although no single blocked INP produced persistent junctional rhythm. Our results support the "summation theory." The incidence of junctional rhythm and hypoxia of the sinoatrial node (flow rate of less than 10 mL.100 g-1.min-1) were markedly enhanced by coexisting blockade of atrial feeding arteries in addition to division of the anterior INP. In conclusion, massive posterior INP disruption is a potent anatomic substrate in producing sustained atrial flutter, middle INP division a modifier, and anterior INP division an inhibitor. Division of the anterior INP is a potent anatomic substrate in producing junctional rhythm, and hypoxia involving the sinoatrial node reacts as its synergic factor.

Early identification of patients at risk for sinus node dysfunction after Mustard operation

We studied 60 patients who had survived the Mustard procedure for transposition of the great arteries, performed between the ages of 2 days and 24 months (mean 4.51 +/- 3.79). All patients were given a postoperative 24-hour dynamic electrocardiogram at 15 days, 1 year and 3 years and then every 2 years. Those who were found to have sinus node dysfunction during follow-up, were given a dynamic electrocardiogram every 3-6 months. The average follow-up period was 38.7 +/- 19.8 months, median 36. Sinus node dysfunction was detected during follow-up in 20 patients (33.3% of the total), 8 of whom had had a pacemaker inserted. Risk factors for late development of sinus node dysfunction were found to include prolonged cross-clamping of the aorta during surgery (P = 0.003), especially over 50 minutes (relative risk 3.5:1), and the presence of even transient sinus node dysfunction after surgery (P = 0.006). These observations suggest, first, that sinus node dysfunction may develop after the Mustard operation as a combined effect of extensive atrial surgery and a long period of myocardial ischemia and, second, that the presence of the disease immediately after the operation sometimes indicates that it will recur or persist during follow-up.

Cardiac rhythm after Mustard repair and after arterial switch operation for complete transposition

We compared the prevalence of arrhythmias among the first consecutive 45 patients with complete transposition (concordant atrioventricular and discordant ventriculo-arterial connexions) after arterial switch operation and the last 47 patients after Mustard repair in infancy. Both groups had 24-hour Holter electrocardiographic studies at similar periods of follow up (24 +/- 14 and 25 +/- 18 months). A second group of patients undergoing the Mustard procedure had been repaired at an older age before 1981. They were studied to determine the frequency of disturbances of rhythm during later postoperative follow-up (85 +/- 24 months). Symptomatic brady-/tachyarrhythmia syndrome never occurred after the arterial switch and only once in the group of patients repaired by the Mustard procedure in infancy, but developed at a late stage (69 +/- 28 months); five times in the group of patients having Mustard's repair at an older age. In addition, Holter monitoring did not detect bradyarrhythmias indicating sinus node dysfunction in a single patient after the arterial switch, but did so to a similar extent in both groups having the Mustard procedure (recent: n = 14; older: n = 18). Three cases of the group of older patients undergoing a Mustard operation developed complete atrioventricular block during follow-up. Normal findings were present in 93% of the cases after arterial switch, but in only 51% of the cases with a similar follow-up repaired by the Mustard procedure, and in 29% of the group having the Mustard repair at an older age.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary arteriography using balloon occlusion of the aortic root in infants with transposition of the great arteries

A simple technique of coronary arteriography using balloon occlusion of the aortic root is described. The technique has greatly helped in the selection of the arterial switch operation for infants with transposition of the great arteries (TGA) in whom accurate recognition of the anatomy of the coronary arteries is important and yet selective coronary arteriography is technically difficult. The technique has been used in 13 consecutive infants and has proved very helpful in 12, with no serious adverse effects.

Predictors of rhythm disturbances and subsequent morbidity after the Fontan operation

The electrocardiographic, hemodynamic and surgical data of 30 patients who underwent a Fontan operation between 1977 and 1986 were retrospectively reviewed to identify the incidence and predictors of immediate and late postoperative arrhythmias and associated morbidity in long-term survivors. Of 4 patients who died less than 1 year after operation (mortality 13%), 1 death was related to an arrhythmia. Three patients were not in sinus rhythm before operation and were excluded from the statistical analysis that examined predictors of arrhythmias. The remaining 23 long-term survivors have been followed 6.3 +/- 2.6 years (mean +/- standard deviation) since surgery and all remain in New York Heart Association functional class I or II. Ten patients (43%) developed immediate postoperative arrhythmias (less than or equal to 30 days) whereas 11 (48%) had late arrhythmias. With up to 10.7 years of follow-up, the proportion of patients free from late arrhythmias continues to decline. Arrhythmias included bradyarrhythmias, atrial tachyarrhythmias, the tachy-brady syndrome and supraventricular ectopic activity. Immediate postoperative arrhythmias predicted late arrhythmias (p = 0.022). The preoperative electrocardiogram was the only variable useful in predicting both immediate and late postoperative arrhythmias. A more negative P-wave deflection in lead V1 (-2.4 +/- 0.7 vs -1.4 +/- 1.2 mV, p = 0.02) predicted patients with immediate postoperative arrhythmias, whereas both greater P-wave duration and a more negative deflection in this lead predicted late arrhythmias (103 +/- 14 vs 83 +/- 20 ms, p = 0.01, and -2.5 +/- 0.8 vs -1.3 +/- 1.0 mV, p = 0.005, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

The asymptomatic child a long time after the Mustard operation for transposition of the great arteries

We studied 36 asymptomatic children 7.7 +/- 2.5 years after a Mustard operation. Fifteen children had sinus rhythm on all electrocardiograms made during follow-up. Only 2 had normal 24-hour Holter recordings throughout follow-up, 6 had periods of supraventricular tachycardia, and 3 had periods of atrial flutter. The electrophysiological evaluation of sinus node function was normal in 5 of the 31 children who were studied. The behavior of the atrial myocardium was electrophysiologically abnormal in most of the children. Atrioventricular node function, on the contrary, was normal in nearly all of the children. Eleven children had normal hemodynamics. Four had severe or complete obstruction of the superior vena cava, 1 had a severe pulmonary venous obstruction, 3 had a severe left ventricular outflow tract obstruction, and 2 had a large left-to-right shunt. Only 3 children had normal hemodynamic and electrophysiological studies. We conclude that the absence of symptoms and a normal routine examination of children a long time after a Mustard operation does not exclude hemodynamic and electrophysiological abnormalities, which can sometimes be severe. In view of these disappointing results, we decided to replace the Mustard operation with the arterial switch operation in children with transposition of the great arteries.

Electrophysiologic consequences of the arterial switch repair of d-transposition of the great arteries

Electrophysiologic studies were performed at 12.7 +/- 4 months postoperatively in 20 patients who had the arterial switch repair at 1 to 120 days (mean 13 +/- 26 [SD]) for d-transposition of the great arteries. Preoperative electrocardiograms (ECGs) at rest revealed an ectopic atrial rhythm in one patient. Postoperative rest ECGs revealed transient postoperative ectopic atrial or junctional rhythms in two patients, intermittent ectopic atrial rhythms in two and right bundle branch block in nine with a normal QRS axis. In addition, ambulatory monitor recordings revealed infrequent premature ventricular complexes in five patients. Catheter endocardial mapping revealed sinus rhythm in 18 patients and ectopic atrial rhythm in 1 patient. Atrial activation after the switch repair was comparable with normal atrial activation. Activation of all low atrial sites was significantly earlier after the switch repair than after the Mustard repair. Mild abnormalities of sinus node function were present and consisted of slight prolongation of corrected sinus node recovery time in six patients and slightly increased sinoatrial conduction time in four. The ratio of sinus node recovery time to sinus cycle length was normal in all 20 patients. Atrial effective and functional refractory periods were normal in all patients and no atrial arrhythmias could be induced by programmed stimulation. Atrioventricular (AV) node conduction was excellent with normal AV node effective and functional refractory periods. The only electrophysiologic abnormality of His-Purkinje function was distal right bundle branch block in nine patients. Programmed stimulation of the ventricle produced repetitive ventricular responses in four patients: bundle branch reentry in three and intraventricular reentry in one.(ABSTRACT TRUNCATED AT 250 WORDS)

Inducible atrial flutter after the Mustard repair of complete transposition of the great arteries

Atrial flutter is a common postoperative arrhythmia in patients with complete transposition of the great arteries (d-TGA) after the Mustard repair. Sixty patients with d-TGA who had the Mustard repair were evaluated by electrophysiologic studies. Thirty-three (55%) had inducible sustained atrial flutter; 17 of them developed spontaneous clinical episodes of atrial flutter (clinical atrial flutter group) and 16 did not (nonclinical atrial flutter group). In 6 of the 17 patients (35%) with clinical inducible atrial flutter, the condition was first documented in the electrophysiologic laboratory with subsequent development of spontaneous clinical episodes. Catheter endocardial mapping, used to determine atrial activation sequences and and conduction intervals, revealed intraatrial conduction delays with late activation of the low atrial sites in all patients. Abnormalities of atrial refractoriness were present, with a greater dispersion of atrial refractoriness found in the clinical atrial flutter group. Severe abnormalities of sinus nodal function appeared to a significantly greater degree among patients who had clinical episodes of atrial flutter. These electrophysiologic abnormalities and associated arrhythmias may predispose patients with d-TGA to sudden death.

Electrophysiologic consequences of the Mustard repair of d-transposition of the great arteries

This study describes the electrophysiologic effects of the Mustard repair of d-transposition of the great arteries on the sinus node and on conduction and refractoriness in the atrium, atrioventricular (AV) node and ventricle. Seventy-two electrophysiologic studies were performed on 64 patients after the Mustard operation. Standard rest and 24 hour ambulatory electrocardiograms were evaluated. Catheter endocardial atrial mapping, available in 67 of the 72 studies, revealed that sinus rhythm was present in the atria in 33 patients, ectopic atrial rhythm in 26 and junctional rhythm in 8. Intraatrial conduction delays with very late activation of the low medial, low lateral or low right atrium at the AV junction were present in 53 of 59 patients with atrial or sinus rhythm. Sinus node function was normal in only nine patients. Prolonged refractory periods were found in the right atrial portion of the new right atrium when compared with the left atrial portion of the new right atrium. Forty-one percent of the patients had prolongation of atrial refractoriness with shortening of the paced cycle lengths. Fifty-one percent developed sustained intraatrial reentry with programmed atrial stimulation. Forty-eight percent of these patients with inducible atrial tachycardia have since developed clinical episodes of atrial flutter. In summary, electrophysiologic studies revealed significant abnormalities of sinus node function and atrial conduction and refractoriness. Alone or in combination, these abnormalities, which result in severe bradycardia or rapid atrial arrhythmias, may lead to sudden death. The Jatene or arterial switch procedure may provide an appropriate alternative operation in this group of patients.

Transposition of the great arteries: late results in adolescents and adults after the Mustard procedure

A selected group of 18 patients aged 15-27 years with transposition of the great arteries and a previous Mustard procedure were evaluated to determine their functional ability and clinical state. Arrhythmias were common, occurring at some time in 16/18 (89%). Arrhythmia was serious in four; two of them required pacing and two had cardiac arrests, one resulting in death. Seven (41%) had right ventricular dysfunction; this was progressive in three. Tricuspid regurgitation was present in seven (41%); it occurred in patients with normal and reduced right ventricular ejection fractions. Regurgitation became progressively worse as the right ventricle dilated. Left ventricular function was well preserved in most patients. Fourteen (82%) of this pioneer group were leading normal lives (ability index 1 or 2). Although these results are acceptable concern remains about the probability of deteriorating right ventricular function.

Late results of the Mustard procedure in transposition of the great arteries

Thirty-five patients were discharged from the hospital after a Mustard procedure and have been followed a mean of 4.5 years. Thirty remain in a stable atrial or sinus rhythm, 3 have required hospitalization and medication to control atrial dysrhythmias, 1 is in a junctional rhythm, and 1 requires a pacemaker. In no patient has there been clinical evidence of systemic or pulmonary venous baffle obstruction. Twenty-two patients have had an elective postoperative cardiac catheterization, which has confirmed the absence of baffle obstruction. We attribute the lack of baffle obstruction and the low incidence of atrial dysrhythmias to several technical points in the operation including: direct high cannulation of the superior vena cava, aggressive resection of the atrial septum except in the region of the atrioventricular node, an extremely large pericardial baffle trimmed in the manner of Brom, sharp divergence of the upper and lower limbs of the inferior suture line away from one another and toward the caval orifices once they enter the right atrium, and very superficial endocardial bites of the baffle suture line in the region of the sinoatrial and atrioventricular nodes.

Atrial dissociation: an electrophysiologic finding in a patient with transposition of the great arteries

Complete interatrial block with two independent atrial rhythms is demonstrated by intracardiac electrograms in a patient with transposition of the great arteries who had undergone a Mustard operation. The atrial conduction abnormalities produced by the Mustard procedure with subsequent baffle revision are related to damaged anatomic interatrial connections and are similar to conduction abnormalities produced in experimental models of interatrial block.

Transesophageal study of recurrent atrial tachycardia after atrial baffle procedures for complete transposition of the great arteries

Transesophageal study was used for diagnosis and treatment of 51 episodes of tachycardia in 13 patients with complete transposition of the great arteries who had undergone atrial baffle procedure. At the time of atrial baffle procedure, patients were 6 to 36 months old (mean 23). Tachycardia (1 to 17 episodes per patient) first occurred 1 to 23 days (4 patients) or 1.8 to 12 years (9 patients) after atrial baffle. Transesophageal study was performed using a bipolar silicone rubber-coated catheter. Tachycardia conversion was accomplished with stimulation bursts using 4 to 10 stimuli 9.9 ms in duration at 20 to 28 mA and an interstimulus interval of 50 to 100 ms less than the atrial cycle length. All tachycardia episodes had regular atrial cycle lengths ranging from 200 to 350 ms. In 12 patients, second-degree atrioventricular (AV) block was observed during tachycardia, suggesting primary atrial tachycardia. However, in 1 patient, occurrence of AV block always resulted in tachycardia termination, suggesting the presence of AV reentrant tachycardia. Transesophageal stimulation converted 48 of 51 tachycardia episodes to sinus/junctional rhythm. Ten tachycardia episodes in 6 patients were transiently converted to atrial fibrillation lasting 3 seconds to 28 minutes before spontaneous conversion to sinus junctional rhythm. Conversion attempts were unsuccessful on 3 occasions. Acceleration of ventricular rate after stimulation necessitated DC cardioversion on 1 occasion. Conversion was not achieved in 2 tachycardia episodes using stimuli less than 10 mA. Transesophageal study is a safe and effective minimally invasive technique for diagnosis and treatment of tachycardia in infants and children who have had atrial baffle for transposition of the great arteries.

Arrhythmias after the Mustard operation for transposition of the great arteries: a long-term study

This study presents follow-up data on 95 patients with transposition of the great arteries who underwent a Mustard intraatrial baffle operation. The patients were followed up serially by means of scalar electrocardiograms and 24 hour Holter monitoring studies. The latter study was effective in documenting abnormal rhythm patterns when the standard electrocardiogram was within normal limits. Twenty percent of the patients had atrial arrhythmias at the time of hospital discharge. new rhythm disturbances were recognized during each year of follow-up; 75% of the patients had atrial rhythm disorders by the sixth year. Slow junctional rhythm was the most common rhythm disturbance found. Complete heart block did not occur. Supraventricular tachycardia occurred within the context of the tachycardia/bradycardia syndrome in 8 of 10 patients, and in all it was documented after hospital discharge. The incidence of sudden death in this series was 3%. Six of the patients have had pacemaker insertions and there have been no deaths among these individuals. It was observed that the slow atrial or junctional rhythms that appeared after intraatrial correction of transposition of the great arteries rarely progressed to life-threatening rhythm disorders in childhood or adolescence, but the prognosis in adult life remains unknown. The three deaths in the series occurred in patients with a history of supraventricular tachyarrhythmias. Elimination of arrhythmias caused by extensive intraatrial surgery is one of the potential advantages of the arterial switch operation for correction of transposition of the great arteries.

Sinus node dysfunction in pediatric and young adult patients: treatment by implantation of a permanent pacemaker in 39 cases

To examine the clinical course of sinus node dysfunction that necessitates permanent pacing in the pediatric and young adult populations, we studied the records of the 39 patients 40 years of age or younger (mean age, 23 years) who underwent implantation of a permanent pacemaker for treatment of this disorder at our medical center between 1960 and 1983. The tachycardia-bradycardia syndrome was the most common rhythm disturbance, and syncope was the most frequent initial symptom. All symptomatic patients noted resolution of symptoms after pacemaker implantation. Twenty-five of the 39 patients (64%) had associated cardiovascular disease, most commonly transposition of the great arteries. In each of the 11 patients with this anomaly, sinus node dysfunction developed after a surgical procedure for correction of the defect. Of the total patient population, 20 patients (51%) had previously undergone a cardiac operation. The mean interval between pacemaker implantation and the previous operation was 105 months. After a mean follow-up of 50.5 months, the patients with no obvious underlying heart disease have done well. Each of the eight patients who have died had underlying cardiovascular disease. None of the deaths was thought to be pacemaker related. Sinus node dysfunction should be considered in the differential diagnosis of young patients with syncope or dizziness, especially if they have undergone a reparative cardiac surgical procedure. If symptomatic sinus node dysfunction is confirmed, permanent pacing is an effective therapeutic modality. In the absence of associated heart disease, the prognosis seems to be excellent.

Surgery for transposition of the great arteries: recent experience in the west of Scotland

From January 1980 to May 1983, 38 children underwent corrective surgery for transposition of the great arteries using the Mustard operation at the Royal Hospital for Sick Children in Glasgow. Twenty-nine children (Group 1) had 'simple' transposition, four (Group 2) had transposition and ventricular septal defect and five (Group 3) presented with complex anomalies. Operative mortality was zero for Groups 1 and 2. In Group 3, two children died within 30 days of operation. In the follow-up period of between three months and three and a half years there have been three late deaths. This report outlines the presentation, management and short term follow-up of children who have undergone the Mustard operation in this hospital since 1980.

Clinical experience with atrial inversion using a Gore-Tex baffle in 52 cases of transposition of the great arteries

Atrial inversion was achieved by a modified Mustard operation in 334 patients with various types of transposition of the great arteries (TGA) between January, 1974, and January, 1983, in Hannover, West Germany. The overall mortality was 4.2% (N = 14). Between March, 1978, and January, 1983, 197 of the patients were operated on using a new design of a Gore-Tex prosthetic baffle. In February, 1982, a new step was integrated into our modification of the Mustard operation. It consisted of creating a pericardial flap that serves to enlarge the pulmonary venous atrium. This article describes the modified Mustard operations with Gore-Tex baffle used in 52 children with TGA between October, 1981, and January, 1983. Special attention is focused on operative techniques and on postoperative dysrhythmias and hemodynamics.

Cardiac rhythm after the Mustard operation for complete transposition of the great arteries

The Mustard operation corrects the effects of congenital transposition of the great arteries by creating an intraarterial baffle to direct pulmonary venous blood to the tricuspid orifice and systemic venous blood to the mitral orifice. To identify the long-term effects of this procedure, we followed 372 patients with complete transposition of the great arteries who survived the Mustard operation for at least three months. The mean follow-up period was 4.5 years (range, 0.4 to 15.9); the mean age at operation was 2.0 years. Mean resting heart rates were consistently lower than those for age-matched normal children. Seventy-six per cent of the patients had sinus rhythm during the year of operation--a figure that decreased to 57 per cent by the end of the eighth postoperative year. Twenty-five patients died during the follow-up period, nine suddenly. Life-table analysis revealed a cumulative survival rate of 91 per cent for 11 years and 71 per cent for 15 years after the operation. No strong risk factor for sudden unexpected death identified. This study demonstrates that extended survival among patients with transposition can be expected after the Mustard operation. However, over time there is a decreasing prevalence of normal sinus rhythm in survivors, as well as a small risk of sudden death.

Inducible polymorphous ventricular tachycardia following Mustard operation for transposition of the great arteries

A 22-year-old woman with chronic atrial tachycardia following Mustard's operation for transposition of the great arteries presented with dizziness and ventricular tachycardia documented with dynamic 24-h electrocardiogram. During intracardiac electrophysiology study, programmed ventricular extrastimulation induced polymorphous ventricular tachycardia (torsades de pointes). This was prevented by intravenous administration of procainamide. We postulate that polymorphous ventricular tachycardia is a possible cause of death in patients with Mustard's operation. Postoperative electrophysiologic study may define those patients at risk to develop this potentially fatal arrhythmia.

Comparative electrophysiological evaluation of atrial activation and sinoatrial node function following Senning and Mustard procedures: an experimental study

We compared several electrophysiological variables before and after Mustard and Senning procedures in 14 mongrel dogs and made the following three observations. First, after the Senning operation, the atrial activation in the areas of the anterior and middle internodal tracts is undamaged. After the Mustard procedure, however, conduction through the interatrial septum is practically abolished. Both techniques damage the area of the posterior internodal tract. On the whole, there is greater dispersion of atrial epicardial mapping with the Senning operation. Second, several degrees of depression in the sinus node automatism and intraatrial conduction were observed with both techniques. Third, atrioventricular block in various degrees was observed only after the Mustard procedure. The atrioventricular dissociation observed after the Senning operation was dependent on sinus pacemaker dysfunction only. We think that from the electrophysiological point of view, the Senning procedure is a valid alternative for repair of transposition of the great arteries.

Cardiac rhythm and conduction before and after anatomic correction of transposition of the great arteries

To assess pre- and postoperative arrhythmias associated with anatomic correction of transposition of the great arteries, 34 patients had 145 standard electrocardiograms (ECGs) and 24 of these patients had 46 24-hour ECGs from 11 months before to 54 months after anatomic repair. Twenty-two patients underwent balloon atrial septostomy and 7 surgical atrial septectomy before the initial 24-hour ECG. Anatomic correction included repair of a large ventricular septal defect in 16 patients and an aortopulmonary window in 1 patient. The preoperative standard ECG showed sinus rhythm in every patient. Preoperative 24-hour tapes revealed sinus arrhythmias in 2, sinus bradycardia at a rate of less than or equal to 50 beats/min in 1, junctional rhythm in 1 and rare premature ventricular contractions (PVCs) in 1. The postoperative 24-hour ECG showed atrioventricular dissociation in 1 patient, rare premature atrial contractions in 7, rare PVCs in 8 and sinus bradycardia with junctional escape in 1. Eight patients had PVCs on the postoperative ECG that were not noted on preoperative tapes. No patient had prolonged bradycardia (less than or equal to 50 beats/min), life-threatening arrhythmias or sudden death. Except for 1 patient with atrioventricular dissociation believed to be secondary to a preventable cause, 34 patients followed for 890 patient-months after anatomic correction for transposition of the great arteries had no significant arrhythmias.

Dysrhythmias after atrial surgery in children

A retrospective study was done in 50 patients after Mustard's operation (group A) and in 204 patients after closure of a secundum atrial septal defect (group B) to analyze the postoperative dysrhythmias and to relate them to surgical factors. Forty-two percent of the patients in group A had dysrhythmias at the end of the follow-up, compared to 23% of group B patients. There was a high late mortality in group A (16%) significantly related to AF and AVJ. In group A a significant correlation was found between dysrhythmias and age at operation, use of cardioplegia, perfusion time, and the type of cannulation. In group B there was a significant relation between the location of the defect and the presence of abnormal pulmonary venous drainage. After ASD closure using hypothermia instead of cardiopulmonary bypass, the incidence of dysrhythmias was significant lower. Damage to the sinus node by cannulation and by suturing in the sinus node area is the main cause of the high incidence of dysrhythmias after atrial surgery. This high incidence should be a factor in the consideration of new types of operations.

Arrhythmias in transposition of the great arteries after the Mustard operation

Disorders of rhythm or conduction in patients with transposition of the great arteries (TGA) after the Mustard operation have been widely reported. This study provides a systematic evaluation of the electrophysiologic function of 87 survivors of the Mustard operation at a single institution. Surface electrocardiograms were reviewed in all 87 patients, Holter monitoring data in 26 patients, exercise electrocardiograms in 21 patients, and invasive electrophysiologic data in 61 patients. Surface electrocardiograms showed normal sinus rhythm in 52%, sinus node dysfunction in 27%, and atrioventricular block in 16%. Holter monitoring was obtained in an unselected subgroup of 26 patients who had a mean age of 12 years and a mean interval from operation of 9 years. Sinus node dysfunction was found in 58%, atrioventricular block in 27% ventricular ectopy in 50%, supraventricular ectopy in 27%, and no abnormalities in only 8%. Intracardiac electrophysiologic evaluation showed a high frequency of abnormal sinus node recovery times and suboptimal response of the atrioventricular-conduction system to rapid atrial pacing. When all modalities used in this study were considered, sinus node dysfunction occurred in 47%, ectopy in 34% and atrioventricular block in 23%. Although only 30% of patients had no evidence of arrhythmia, symptoms of rhythm or conduction disturbances were rare.

Pacemaker treatment of sick sinus syndrome in children

The sick sinus syndrome is being recognized with increasing frequency in children. Although it is sometimes benign, it can be serious or have fatal consequences. Fifty-one patients (mean age 10.5 years) underwent permanent cardiac pacing for sick sinus syndrome. Twenty patients had epicardial ventricular pacing and 12 had an epicardial atrial implant. Seven had endocardial atrial pacing, six epicardial atrioventricular (AV) sequential pacing, four epicardial universal pacing and two endocardial universal pacing. Of the 49 symptomatic patients, 45 had relief of symptoms. Eleven of 18 patients with associated tachyarrhythmias had amelioration of their tachycardia. There were no early but two late deaths unrelated to the pacemakers. Seven patients during a mean follow-up period of 26 months required reoperation for pacing lead or sensing problems. Permanent pacing for sick sinus syndrome in children is a safe and symptomatically effective procedure.

Electrophysiologic residua and sequelae of surgery for congenital heart defects

Postoperative arrhythmias may occur in any patient who undergoes intracardiac surgery for a congenital heart defect. The correction of certain intracardiac heart defects predisposes to a large incidence of cardiac arrhythmias. Ventricular arrhythmias and conduction disturbances are seen after correction of tetralogy of Fallot, ventricular septal defect and atrioventricular canal defect. Supraventricular arrhythmias and sinus nodal dysfunction may be seen after surgery for transposition of the great arteries or atrial septal defect. The identification, evaluation and treatment of these patients are discussed.

Long-term results after atrial repair of transposition of the great arteries in early infancy

Fifty-two patients younger than age 100 days who had an intact interventricular septum or a small ventricular septal defect underwent atrial repair of d-transposition of the great arteries (d-TGA). No patient died. To assess long-term results, we evaluated all 36 patients who had been followed for at least 1.5 years (mean 2.7 years) after surgery. The physical findings, chest roentgenograms, ECGs and echocardiograms were reviewed. Catheterization was done 6-60 months (mean 15 months) after surgery in 28 patients. Growth was normal in all but three patients. Neurologic development was abnormal in six patients (delayed speech in one patient, learning disability in three patients and preoperative cerebral infarction in two patients). The ECG showed sinus rhythm in 24 patients, minor abnormalities in nine and major dysrhythmias in three. Catheterization showed a normal cardiac index in all 28 patients. No intracardiac shunt was detected in 19 of 24 patients in whom complete oximetry data were available. One patient required reoperation for persistent atrial shunt and subsequent pacemaker placement. Two patients required baffle revision for symptoms related to superior vena caval obstruction. Right ventricular end-diastolic pressure was less than 15 mm Hg in all of 18 patients evaluated. We conclude that atrial repair of d-TGA in early infancy can be performed with a low mortality rate and a low incidence of late complications.

Exercise assessment of sinoatrial node function following the Mustard operation

To screen for sinoatrial node dysfunction following the Mustard procedure for transposition of the great arteries, we studied the chronotropic response to graded maximal treadmill exercise in 29 patients at mean 6.7 years after operation. Although 93% of patients had normal resting heart rate (HR), 83% demonstrated significant depression of maximum HR and/or recovery HR after termination of exercise. These findings were similarly present among a subset of 13 patients with normal exercise tolerance. Resting and exercise-induced HR in 10 patients receiving chronic digoxin therapy were no different than in the 19 patients without medication. Sixteen patients with abnormal chronotropic responses to exercise had intracardiac electrophysiologic evaluation which confirmed sinoatrial node dysfunction in nine. Abnormal HR responses did not correlate with clinical symptoms, cardiac arrhythmias, or postoperative hemodynamics. Maximal exercise testing may be a sensitive noninvasive method to identify sinoatrial node dysfunction in postoperative children.

Changing indications for pacemakers in children

Permanent pacemakers were implanted in 50 children. Indications were symptomatic sinus node dysfunction in 34 (68%), surgical block in 9 (18%), and congenital block in 7 (14%). Twenty-three (68%) of the 34 children with sinus node dysfunction had undergone prior cardiac operations. Only 4 of the 50 patients (8%) had electrode problems after a mean pacing time of 29.5 months (range, 1 to 96 months). All 35 of the mercury-cell pulse generators used in 28 patients ceased to function after an average useful life of 20.8 months (range, 1 to 51 months). The lithium-powered units in the 45 survivors all show satisfactory pacing after 5 to 44 months (mean, 28.1 months). With improved pacemaker technology, longer survival after complex repairs, and better monitoring techniques, the indications for cardiac pacing in children have broadened. Surgical block now is an indication in only a small fraction of the pediatric pacemaker population. Sinus node dysfunction accounts for an ever-increasing majority of the pacemakers we currently implant in children.

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.

The echocardiographic profile of patients after Mustard's operation

In order to establish an echocardiographic profile of patients with simple transposition after Mustard's operation, we examined the M-mode records of 10 patients who were found to be free of significant abnormalities at follow-up cardiac catheterization. When compared with established normals, right ventricular wall thicknesses and cavity dimensions were increased, while left ventricular wall thicknesses and cavity dimensions fell below the mean. The wall thicknesses, cavity dimensions and ratios of right ventricular preejection period/ejection time and left ventricular preejection period/ejection time were appropriate for the physiologic role of the ventricles rather than their morphologic identity. In each patient, a portion of the intra-atrial baffle was identified behind the pulmonary root. There was variation in baffle position and baffle mobility within the group, as well as in individual echograms. A variety of valve motion abnormalities were noted; these included diastolic flutter of the atrioventricular valves in all 10 patients and systolic anterior motion of the mitral valve in six patients. Paradoxical septal motion was found in nine patients. Although only minimal or no left ventricular outflow gradients were found at catheterization, nine patients had narrowing of the left ventricular outflow tract, 10 had systolic flutter of the pulmonary valve and eight had early partial closure of the pulmonary valve. The finding of a large number of echocardiographic abnormalities in a group of patients with good hemodynamic results suggests that these echocardiographic features are to be expected after Mustard's opration. Furthermore, the reversal of the physiologic role of the ventricles must be considered when interpreting the echocardiographic dimensions and systolic time intervals.

Early and late results with the Mustard operation in infancy

Eighty-one patients, ranging in age from 36 hours to 24 months and in weight from 2.5 to 12 kg had a Mustard operation for D-transposition of the great arteries (D-TGA) (20 with complex D-TGA) using either deep hypothermic circulatory arrest (68 patients) or conventional cardiopulmonary bypass (13 patients). A Dacron patch was used for the intraatrial baffle and pericardium for augmentation of the pulmonary atrium. Ten patients died following operation. Thirty-two patients had cardiac catheterization 1 year after operation. Of 24 patients with D-TGA and intact ventricular septum, 23 had normal pulmonary artery pressures. In 20 patients left ventricular outflow tract gradients decreased from a mean of 32 mm Hg to a mean of 18 mm Hg after operation. Five patients who had D-TGA and ventricular septal defect and systemic pressures in the left ventricle before operation, had a notable decrease in left ventricular pressures after the procedure. Seven patients required reoperation for baffle obstruction. Mortality following Mustard repair was primarily related to the complexity of the lesion, maturity of the infant, and degree of pulmonary vascular changes. Caval obstruction was related to the configuration of the baffle used in the early part of this series.