Sick sinus syndrome after surgery for congenital heart disease

Atrial flutter and sick sinus syndrome

BACKGROUND

Sick sinus syndrome (SSS) is a common condition resulting in reduced quality of life, syncope, and permanent pacemaker (PPM) implantation, but predictors have not been elucidated. Whereas atrial arrhythmias are frequently associated with SSS, we hypothesized that atrial flutter (AFL) would strongly predict SSS, given shared relationships with right atrial and particularly crista terminalis fibrosis.

OBJECTIVE

The study aimed to assess the impact of AFL on the occurrence of SSS and associated syncope and PPM implantation.

METHODS

Health care databases were used to identify adults aged ≥18 years receiving hospital-based care in California in 2005-2019. International Classification of Diseases codes were used to identify diagnoses and procedures. Patients were classified on the basis of the presence of AFL and atrial fibrillation (AF). Cox proportional hazards models adjusting for demographics and comorbidities were employed.

RESULTS

We included 29,357,609 individuals (54% female; mean age, 46 years), 101,243 with AFL alone, 1,674,680 with AF alone, and 284,547 with AF and AFL. After adjustment for age, sex, race and ethnicity, and comorbidities, AF, AFL, and both arrhythmias were each associated with increased risk of SSS and associated syncope and PPM implantation (all P < .001). In the population with AF, an additional AFL diagnosis conferred a higher risk for development of SSS (hazard ratio [HR],1.62; 95% confidence interval, 1.59-1.64), syncope (HR, 1.63; 1.54-1.72), and PPM implantation (HR, 1.74; 1.70-1.79).

CONCLUSION

AFL is associated with an increased risk of incident SSS and its adverse consequences, especially in patients with coexisting AF. AFL may be useful for risk stratification strategies to predict, to prevent, and to treat SSS.

Mid-term outcomes after catheter ablation in patients with congenital heart disease

INTRODUCTION

Cardiac arrhythmias are a major concern in patients with CHD. The purpose of this study was to evaluate the long-term outcomes in patients with CHD submitted to catheter ablation.

MATERIALS AND METHODS

Observational retrospective study of patients with CHD referred for catheter ablation from January 2016 to December 2021 in a tertiary referral centre. Acute procedural endpoints and long-term outcomes were assessed.

RESULTS

A total of 44 ablation procedures were performed in 36 CHD patients (55% male, mean age 43 ±3 years). Fifty-four arrhythmias were ablated: 23 cavotricuspid isthmus atrial flutters, 10 atrial re-entrant tachycardias, eight focal atrial tachycardias, eight atrial fibrillations, three atrioventricular re-entrant tachycardias, and two ventricular tachycardias. During a median follow-up time of 37 months (interquartile range 12-51), freedom from arrhythmia recurrence was achieved in 93%, with 1.2 procedures per patient (18% with anti-arrhythmic drugs). There were no adverse events related to catheter ablation. No predictors of recurrence were identified.

CONCLUSION

In patients with CHD, catheter ablation presents a high mid-term efficacy while maintaining a safe profile.

Lead Management in Patients with Congenital Heart Disease

Pediatric patients with congenital heart disease present unique challenges when it comes to cardiac implantable electronic devices. Pacing strategy is often determined by patient size/weight and operator experience. Anatomic considerations, including residual shunts, anatomic obstructions and barriers, and abnormalities in the native conduction system, will affect the type of CIED implanted. Given the young age of patients, it is important to have an "eye on the future" when making pacemaker/defibrillator decisions, as one can expect several generator changes, lead revisions, and potential lead extractions during their lifetime.

Sinus Node Dysfunction

Sinus node dysfunction (SND) is a multifaceted disorder most prevalent in older individuals, but may also occur at an earlier age. In most cases, the SND diagnosis is ultimately established by documenting its ECG manifestations. EPS has limited utility. The treatment strategy is largely dictated by symptoms and ECG manifestations. Not infrequently, both bradycardia and tachycardia coexist in the same patients, along with other diseases common in the elderly (e.g., hypertension, coronary artery disease), thereby complicating treatment strategy. Prevention of the adverse consequences of both bradyarrhythmia and tachyarrhythmia is important to reduce susceptibility to syncope, falls, and thromboembolic complications.

Sinus Node Dysfunction

Sinus node dysfunction (SND) is a multifaceted disorder most prevalent in older individuals, but may also occur at an earlier age. In most cases, the SND diagnosis is ultimately established by documenting its ECG manifestations. EPS has limited utility. The treatment strategy is largely dictated by symptoms and ECG manifestations. Not infrequently, both bradycardia and tachycardia coexist in the same patients, along with other diseases common in the elderly (e.g., hypertension, coronary artery disease), thereby complicating treatment strategy. Prevention of the adverse consequences of both bradyarrhythmia and tachyarrhythmia is important to reduce susceptibility to syncope, falls, and thromboembolic complications.

Sick sinus syndrome and atrial fibrillation in older persons - A view from the sinoatrial nodal myocyte

Sick sinus syndrome remains a highly relevant clinical entity, being responsible for the implantation of the majority of electronic pacemakers worldwide. It is an infinitely more complex disease than it was believed when first described in the mid part of the 20th century. It not only involves the innate leading pacemaker region of the heart, the sinoatrial node, but also the atrial myocardium, predisposing to atrial tachydysrhythmias. It remains controversial as to whether the dysfunction of the sinoatrial node directly causes the dysfunction of the atrial myocardium, or vice versa, or indeed whether these two aspects of the condition arise through some related underlying pathological mechanism, such as extracellular matrix remodeling, i.e., fibrosis. This review aims to shed new light on the myriad possible contributing factors in the development of sick sinus syndrome, with a particular focus on the sinoatrial nodal myocyte. This article is part of a Special Issue entitled CV Aging.

Congenital cardiac surgery without routine placement of wires for temporary pacing

OBJECTIVE

Temporary pacing wires have been associated with serious postoperative complications. Recommendations for their routine use after open heart surgery are decades old, and may not reflect current surgical techniques and outcomes.

METHODS

The electronic web-enabled medical records of all patients undergoing congenital cardiac surgery from February, 2002, through December, 2005, were reviewed, excluding patients undergoing implantation of pacemakers as a primary procedure, or those undergoing ligation of a patent arterial duct.

RESULTS

There were 1193 surgical procedures performed, 1041 with cardiopulmonary bypass. Median age of the patients was 5.8 months, with a range from 0 days to 54 years, weighing 6.2 kilograms, with a range from 1 to 114 kilograms. Mortality prior to discharge was 2.5%, and median postoperative stay was 6 days. No deaths were attributed to arrhythmias. Temporary pacing wires were placed 14 times (1.2%). Indications for placement included sinus nodal dysfunction in 8 patients, preoperative in 4 and intraoperative in 4, high degree atrioventricular block in 4 patients, and intraoperative atrial flutter in 2 patients. Of these patients, 4 (0.3%) eventually underwent permanent implantation of a pacemaker, 2 for persistent sinus nodal dysfunction, and 2 for persistent atrioventricular block. Postoperative junctional ectopic tachycardia requiring antiarrhythmic therapy occurred in 9 patients (0.8%). All recovered without incident, and none were treated with temporary pacing.

CONCLUSIONS

The diminished risk of unexpected postoperative arrhythmias in the current era alleviates the necessity for routine placement of temporary pacing wires. Those institutions with experienced surgical and cardiac critical care teams may be able to predict the need for temporary pacing wires preoperatively or intraoperatively.

Pacemaker Implantation as a Risk Factor for Heart Failure in Young Adults with Congenital Heart Disease

AIM

Complete postoperative heart block following open-heart surgery and sinus node dysfunction are indications for permanent cardiac pacing in children with congenital heart defects. The purpose of our study was to evaluate if cardiac pacing is a risk factor of heart failure during longtime follow-up of grown ups with congenital heart disease (GUCH).

METHODS

For an objective assessment of heart failure, NT-Pro brain natriuretic peptide (BNP) and maximal oxygen uptake index (VO2max) during the cardiopulmonary exercise testing were measured in 346 consecutive GUCH patients during a longtime follow-up examination.

RESULTS

Thirty-nine of these patients who had pacemaker implantation had significantly increased BNP levels (448.2 +/- 76.8 vs 123.8 +/- 9.7 pg/mL, P < 0.0001) and significantly decreased VO(2max) (22.5 +/- 0.9 vs 27.4 +/- 0.4, P < 0.0001). Heart failure in pacemaker patients was associated with significantly prolonged QRS complex durations (171.1 +/- 8.3 ms vs 108.7 +/- 1.8 ms, P < 0.0001), increased right ventricular end diastolic diameters (38.7 +/- 2.1 mm vs 27.8 +/- 0.5mm, P < 0.0001), lower heart rates at rest (69.5 +/- 1.9/min vs 82 +/- 1/min, P < 0.0001), and at exercise (140.3 +/- 5.8/min vs 163.5 +/- 1.2/min, P < 0.0001). Mean fractional shortening of the left ventricle was normal in both patient groups.

CONCLUSION

Pacemaker implantation may be associated with heart failure during longtime follow-up of GUCH indicated by significantly elevated BNP levels and decreased VO2max. Possible explanations are prolongation of QRS complex duration, decreased maximal heart rates during exercise, and dilatation of the right ventricle.

Use of DDDRP Pacing Device in Prevention and Treatment of Tachy-Brady Syndrome After Mustard Procedure

A 13-year-old male patient, who underwent Mustard operation for a very complex congenital heart disease (CHD), after palliation presented a decrease of the sinus node function, developing a tachy-brady syndrome and a mild dysfunction of atrioventricular (AV) conduction. He was successfully treated using a DDDRP pacemaker, which ensured a suitable atrial rhythm and was able to interrupt supraventricular tachycardia episodes. Until now, hospitalization related to episodes of heart failure or symptomatic arrhythmia, has not been necessary.

Pharmacotherapy of atrial fibrillation

Atrial fibrillation (AF) remains a widespread health problem and the drugs available for its treatment suffer from several drawbacks, including potentially lethal proarrhythmia, serious non-cardiac toxicity and limited efficacy. The evidence for efficacy of currently available anti-arrhythmic agents for sinus rhythm restoration and maintenance is reviewed, with emphasis on randomised trials when available. The current approach to thromboembolism prophylaxis in AF is summarised.

Electrophysiological abnormalities before and after surgery for atrial septal defect

The authors evaluated the electrophysiological parameters, atrial-His interval, His-ventricular interval, Wenckebach cycle length, corrected sinus node recovery time (CSNRT), and sinoatrial conduction time (SACT) before and after operation in 28 children with atrial septal defect (ASD). Before operation, electrophysiological abnormalities were detected in 20 (79%) of the 28 patients. Preoperative comparison of the mean value in each parameter between the two age groups showed higher values in all parameters in the older group. In 17 patients who underwent operation, atrial-His interval, Wenckebach cycle length, CSNRT, and atrial effective refractory period (AERP) significantly decreased after operation; preoperatively abnormal Wenckebach cycle length, CSNRT, and AERP values were normalized in many of them. Thus, electrophysiological abnormalities were already present before operation in the ASD children and were severer in the older children, but were improved to some degree following operation.

Permanent cardiac pacing after cardiac operations

From January 1980 through December 1990, implantation of a permanent pacemaker was performed in 34 patients following open heart surgery. The patients were divided into two groups according to the clinical indications for implantation of permanent pacemakers. Group 1 (9 patients) had surgical atrioventricular block, and Group 2 (25 patients) had sick sinus syndrome. Tricuspid valve surgery was involved in 67% of Group 1 and 64% of Group 2. Adams-Stokes syncopal attack was the prime indication for permanent pacing in 100% of Group 1 and in 72% of Group 2. There were 2 operative deaths in Group 1, and no deaths in Group 2 (22% in Group 1 vs. 0% in Group 2, p < 0.005). Causes of the deaths were not related to the pacemaker implantation but to congestive heart failure following surgery. Among 32 survivors, there were 2 late deaths in Group 1, and 4 deaths in Group 2 (25% in Group 1 vs. 16% in Group 2, p < 0.05). The overall actuarial survival rate at 10 years was 82.1 +/- 2.8%. However, the actuarial survival rate of patients in Group 1 is 70.2 +/- 4.1%, which is statistically less than 85.4 +/- 2.2% in Group 2 (p < 0.01). As judged by these results, patients in Group 1 should be followed on a regular out-patient basis even if they are asymptomatic and there is no evidence of pacemaker failure.

Electrophysiological effect of the maze procedure on canine sinoatrial node function

The maze procedure is an operation that has had great initial success in curing atrial fibrillation. This procedure includes several right atrial incisions that may interrupt the integrity of the sinoatrial node or its arterial supply. To assess the effect of the maze procedure on sinus node function (SNF), the following studies were performed: sinus node recovery times (SNRT), corrected SNRT (CSNRT), CSNRT under autonomic blockade maximal heart rate and intrinsic heart rates. Thirty-four dogs underwent a right thoracotomy with cardiopulmonary bypass (CPB). The dogs were divided into three groups. Group 1 (n = 9), the sham group, underwent CPB without any incisions. Group 2 (n = 8) underwent CPB and one of the right atrial incisions. Group 3 (n = 18) underwent CPB and all three of the right atrial incisions. SNF was determined before and after the procedure. Groups 1 and 2 had no significant difference in measured SNF acutely after the procedure. In Group 3 the mean SNRT increased from 552 msec to 1,984 msec (P = 0.005). Sinus node dysfunction was corroborated by all studies. In the chronic studies, a trend toward recovery of SNF was observed. The maze procedure results in significant acute sinus node dysfunction. This dysfunction may resolve spontaneously over the ensuing months. Modifications of the maze procedure that avoid the sinus node or its blood supply area may reduce procedure related sinus node dysfunction.

Ventricular arrhythmias in postoperative tetralogy of Fallot

Ventricular arrhythmias in patients after total surgical repair of tetralogy of Fallot have been associated with late sudden death. In this large multicenter retrospective study of 359 patients with postoperative tetralogy of Fallot, spontaneous ventricular premature complexes (VPCs) on 24-hour ambulatory electrocardiographic monitoring and laboratory-induced ventricular tachycardia (VT) by electrophysiologic stimulation were analyzed. The mean age at surgical repair was 5 years and the mean follow-up duration after repair was 7 years. Spontaneous VPCs on ambulatory monitoring were found in 48% and induced VT on electrophysiologic stimulation was found in 17% of patients. Both spontaneous VPCs and induced VT were significantly related to delayed age at repair, longer follow-up interval, symptoms of syncope or presyncope and right ventricular systolic hypertension (greater than 60 mm Hg) (p less than 0.05), but not to right ventricular diastolic pressure greater than 8 mm Hg. The VPCs on ambulatory monitoring were more complex with increasing age at repair and follow-up duration. Induction of VT on electrophysiologic stimulation correlated with spontaneous VPCs including VT on 24-hour ambulatory electrocardiographic monitoring. The electrophysiologic stimulation protocol varied and the induction of VT increased with a more aggressive stimulation protocol. While induced sustained monomorphic VT was related to all forms of spontaneous VPCs, induced nonsustained polymorphic VT was related to more complex forms of VPCs on ambulatory monitoring. VT was not induced in asymptomatic patients who had normal 24-hour ambulatory electrocardiographic monitoring and normal right ventricular systolic pressure. (ABSTRACT TRUNCATED AT 250 WORDS)

Recording of the electrocardiogram from the sinus node and direct measurement of the sinuatrial conduction time in children

Using a simple technique, the electrocardiogram from the sinus node, which had been previously recorded in adults, was for the first time derived successfully in 27 of 31 children (87%). The values of the sinuatrial conduction time were then precisely measured directly according to the electrocardiogram from the sinus node. The sinuatrial conduction time measured directly was significantly longer in 6 children with sick sinus syndrome (138.3 +/- 10.3 msec, mean +/- standard deviation) than in 21 normal children (66.9 +/- 14.4 msec, mean +/- standard deviation). No overlap was found between them. Furthermore, comparison was made between the children and the adults (7 cases with sick sinus syndrome, 32 cases with normal sinus nodal function). The results suggested that the electrocardiogram recorded from the sinus node may be a valuable and promising technique for the evaluation of sinus nodal function and in the accurate diagnosis of the sick sinus syndrome in children.

Problems with permanent atrial pacing in the Fontan patient

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

Conduction system in sudden unexpected death a considerable time after repair of atrial septal defect

The cause of sudden death in young people with congenital heart disease, months or years postoperatively following total surgical correction, is today unknown despite complete autopsy. This is a study of the conduction system in four cases of atrial septal defect of the fossa ovalis type (secundum) who died suddenly several months to years following surgical repair and who were living a normal life. The study suggests that changes in the sinoatrial node and its approaches produced by surgery aided by a pulling effect of a floppy mitral valve on the central fibrous body and hence, on the conduction system, and the unknown familial genetic arrhythmic effect on the conduction system contributed to the sudden death of these patients.

Conduction disturbances after correction of tetralogy of Fallot: are electrophysiologic studies of prognostic value?

Late complete heart block may occur after correction of tetralogy of Fallot. Whether postoperative electrophysiologic studies can identify patients at risk of developing this conduction disturbance is unknown. In this study, 57 children who underwent electrophysiologic investigation after correction of tetralogy of Fallot were followed up for 1 to 13 (mean 6.5) years after the investigation. One late death and two cases of late complete heart block occurred. The late death was due to ventricular arrhythmia and not to a conduction disturbance. The cases of late heart block occurred 2 and 5 years, respectively, after electrophysiologic study, and in both cases the patient had a prolonged HV interval; in one patient progressive lengthening of the HV interval could be demonstrated at two subsequent studies 1 year apart. Another five patients with a prolonged HV interval had normally conducted sinus rhythm up to 11 years after study. Atrial pacing at increasing rates (up to the occurrence of second degree atrioventricular block) during electrophysiologic study was the best means of predicting late heart block: of three patients with block below the bundle of His occurring at pacing rates less than 180/min, two developed late complete heart block. Thus, electrophysiologic testing of the conduction system after correction of tetralogy of Fallot is useful in predicting late complete heart block and should be performed in patients with a history of transient heart block after surgery and in those with a prolonged PR interval.

Quinidine syncope in children

Quinidine syncope and factors associated with it are well known among adult patients treated for cardiac arrhythmias. To define factors that may influence the occurrence of syncope in children taking quinidine, the clinical, anatomic, electrocardiographic, roentgenographic and pharmacologic data were compared in six patients with syncope (Group A) and 22 patients without syncope (Group B). There was a significant (chi-square = 10.2, p = 0.001) relation between heart disease and quinidine syncope: all six Group A (syncopal) patients had heart disease whereas 15 of the 22 Group B (non-syncopal) patients had no structural heart disease. In contrast, no significant difference was noted between Group A and Group B patients in mean age (11.4 versus 11.4 years), mean quinidine serum concentration (2.9 versus 2.3 micrograms/ml), mean corrected QT interval before quinidine (0.43 versus 0.40 second) or mean corrected QT interval during quinidine therapy (0.46 versus 0.46 second) or between those taking digitalis and those not. Two of the six Group A (syncopal) patients died during therapy, one 6 days after initiating therapy and one suddenly at home 6 months after beginning quinidine. Another two of the six Group A patients exhibited hypokalemia (both 2.9 mEq/liter) at the time of syncope, 2 weeks and 6 months, respectively, after initiation of quinidine therapy; both survived. Syncope occurred within 8 days of initiation of quinidine therapy in three of the six patients. Sustained ventricular tachycardia was observed during quinidine associated arrhythmia in three of six patients with syncope; nonsustained ventricular tachycardia or complex ventricular ectopic activity while on this therapy was observed before syncope in the other three patients in Group A.(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.

A 20-year review of ostium primum defect repair in children

Between July, 1963, and July, 1983, a total of 69 patients (35 boys and 34 girls) underwent ostium primum defect repair. There were four perioperative deaths and four patients were subsequently lost to follow-up, leaving 61 children followed for 6 months to 20 years (mean 5 years). Results of surgery were assessed by cardiac catheterization in 17 of 61 patients, while the remaining patients were evaluated noninvasively. Postoperative mitral insufficiency was found to be absent in 19 patients, mild to trivial in 35, moderate in four, and severe in two. Four patients were found to have large residual atrial septal defects. Significant late postoperative arrhythmias were found in 14 of 61 patients. The types of arrhythmias included isolated complete atrioventricular block in 5 of 14, complete atrioventricular block with sinus node dysfunction in 2 of 14, and isolated sinus node dysfunction in 7 of 14. Pacemakers have been implanted in 8 of 14 of these patients. Based on this 20-year review of a large number of children: (1) ostium primum defect repair is associated with a low mortality rate, (2) residual mitral insufficiency although common is usually mild to trivial and nonprogressive, and (3) significant arrhythmias are a frequent complication and often require pacemaker implantation.

Long-term follow-up of dysrhythmias following the Mustard procedure

Earlier reports have suggested that the incidence of dysrhythmias after the Mustard procedure can be reduced if the sinoatrial node (SAN) is protected during surgery. To determine if these initial differences continue after longer follow-up, we examined all ECGs available for three groups of patients operated upon from January, 1965, through December, 1977. Group A included 37 patients who survived the operation prior to January, 1972, when surgical modifications were initiated to protect the SAN; group B included 44 patients available for follow-up who were operated upon from 1972 through 1974; and group C consisted of the 39 patients available for follow-up operated upon from 1975 to 1977. Dysrhythmias were classified as passive (failure of initiation or propagation of the SAN impulse), active (atrial flutter or supraventricular tachycardia), or atrioventricular (AV) conduction defects. Results were expressed as the incidence per number of different rhythms during follow-up intervals. The incidence of sinus rhythm in groups B and C (80%) was much greater than in group A (27%) during the first 2 years. However, after 8 years, less than 50% of the rhythms were sinus. Both brady- and tachydysrhythmias were common. Seven patients (6%) required pacemaker insertion for symptomatic sick sinus syndrome. Therefore despite efforts to protect the sinus node, late occurring dysrhythmias remain a significant problem in the postoperative Mustard patient.

Ventricular thrombosis during permanent endocardial pacing in a pediatric patient with hemorrheological disorders

Thrombosis in the right atrium or ventricle is a rare complication of permanent endocardial pacing in adults. To the best of our knowledge, this complication has not been previously reported at all in the pediatric age group. We report on a case of a 7-year-old boy who had large left ventricular thrombi that occurred during permanent endocardial electrical stimulation. Subsequent pulmonary emboli complicated congestive heart failure in this patient. As a diagnostic approach, echocardiography and pulmonary perfusion scintigraphy were used. We comment on possible causes of this serious complication and suggest hemorrheological and platelet activation studies in patients with permanent endocardial pacing.

Electrophysiologic abnormalities of children with ostium secundum atrial septal defect

Sinus node (SN) and atrioventricular node (AVN) function were evaluated in 49 patients with secundum type atrial septal defect (ASD). Automaticity and conduction system function were assessed by intracardiac recording of the AH and HV intervals at rest, corrected SN recovery time, sinoatrial conduction time, AVN refractory period and the ability of the AVN to conduct rapidly paced atrial beats to the ventricles. Electrophysiologic abnormalities were found in 41% of the 34 patients who were studied before surgery. However, no preoperative abnormalities were present in children younger than 2.5 years. If only children older than 2.5 years were analyzed, the incidence of conduction abnormalities was similar for the patients studied before operation (62%) and those studied after operation (71%). The size and ejection fractions of the right and left ventricles, the magnitude of shunt flow and the size of the ASD did not differ between the patients with and those without electrophysiologic abnormalities. AVN dysfunction was present in 40% of the patients who were studied after surgical repair. While this frequency was more than twice the preoperative incidence of AVN dysfunction, it was not statistically significant. The data suggest that patient age is the major factor that influences the presence of conduction system dysfunction in patients with ASD.

Detection of cardiac dysrhythmias by continuous electrocardiographic recording in children undergoing cardiac surgery

The incidence of dysrhythmias was studied using 24-hour ambulatory electrocardiographic monitoring in 65 consecutive cases of children undergoing cardiac surgery. Recordings were made prior to surgery and in the early (1-10 days) and late (3-12 months) post operative periods. Prior to surgery, 25% of the patients displayed supraventricular dysrhythmias (SVD) and 39% ventricular dysrhythmias (VD). Immediately following surgery a dramatic increase in incidence occurred in both SVD and VD. On late follow-up the frequency of ectopy decreased but not to pre-operative levels. Standard 12-lead ECG was much less sensitive than Holter monitoring, detecting less than 25% of all dysrhythmias. Assessment of preoperative rhythm status is necessary to properly interpret postoperative dysrhythmias. Twenty-four hour ambulatory ECG recording is essential for the detection and evaluation of dysrhythmias in children undergoing cardiac surgery.

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.

Symptomatic sick sinus syndrome in children and adolescents as the only manifestation of cardiac abnormality or associated with unoperated congenital heart disease

Sick sinus syndrome (SSS) occurs infrequently in children who have not undergone cardiac surgery. The symptoms, electrocardiograms, and electrophysiologic data in 11 patients aged 2 to 17 years who had nonsurgical SSS were reviewed. Syncope occurred in 5 patients and sinus bradycardia in 9. Sinus nodal recovery times were prolonged in 6 patients. The atrial effective refractory period was prolonged in 2 patients and the atrioventricular nodal functional or the effective refractory period, or both, was prolonged in 5 patients. Because patients with nonsurgical SSS may have abnormalities not only of the sinus node but also of the atrium and the atrioventricular node, it is recommended that patients with symptomatic SSS be evaluated by electrophysiologic study. The proper choice of antiarrhythmic drug therapy or permanent pacing procedure depends on a complete analysis of the cardiac conduction system.

Ventricular pacing in children

Ventricular pacing was performed in forty-one children ranging from one day to twenty years of age (median age = 10). Weight of the recipient at implant ranged from 2 kg. to 86 kg. Indications included presyncope, syncope, dyspnea on exertion, congestive heart failure, postoperative infra-Hisian heart block, and inadequate cardiac rate during pharmacotherapy. Four patients died during follow-up, but no deaths were attributable to pacemaker management. In contrast, 66% of the patients required more than one pacemaker related-operative procedure, and 43% of leads implanted failed by 48 hours. Indications for permanent cardiac pacing in this population at this time are symptomatic congenital AV block, symptomatic sinus node disease, and AV block in the postoperative period. Technological developments which might reduce complications seen in this population and electrophysiologic techniques which may better define indications for pacing in children are also reviewed.

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.

Electrophysiologic effects of propranolol on sinus node function in children

Little is known regarding the effects of propranolol (P) on sinus node function in children. In this study, corrected sinus node recovery time (CSNRT) and estimated sinoatrial conduction time (SACT) were measured in 10 children (ages 3 to 16 years; mean 8.3 years) without clinical evidence of sinus node dysfunction before and after intravenous P. The spontaneous sinus cycle length (SCL) increased after P(0.1 mg/kg) in all patients. Mean SCL increased 13.4% from 635 +/- 200 msec (+/- SD) to 720 +/- 202 msec (p less than 0.01). Maximum CSNRT increased in nine patients after P and mean CSNRT increased 63% from 203 +/- 61 msec to 330 +/- 190 msec (p less than 0.05). SACT changed in a random fashion after P. Mean SACT did not change significantly. We conclude that P significantly suppresses sinus node automaticity in children with normal sinus node function but has little or no effect on sinoatrial conduction.

Long-term endocardial atrial pacing in children with postoperative bradycardia-tachycardia syndrome and limited ventricular access

Permanent pacing in children, including those with postoperative bradycardia-tachycardia syndrome has been compromised by the availability of pulse generators, electrode leads and implantation techniques designed for the adult patient. Recent technologic improvements and simplified implantation techniques have reduced many of these barriers and have made endocardial as well as epicardial ventricular pacing more feasible. However, in some children, ventricular pacing may be impeded by anatomic abnormalities due to congenital anomalies or prior cardiac operations. In these instances, endocardial atrial pacing may provide an alternative therapeutic approach in selected patients. This report describes the use of endocardial atrial demand pacing in four children with postoperatively bradycardia-tachycardia syndrome and restricted ventricular access. This approach controls symptomatic bradycardia, helps prevent and convert paroxysmal intraatrial tachycardia and overcomes the problems of limited ventricular access.

24-hour electrocardiographic study of heart rate and rhythm patterns in population of healthy children

Twenty-four hour electrocardiographic recordings were made on 104 randomly selected, healthy 7 to 11-year-old children. Ninety-two were technically adequate and suitable for analysis. The mean highest heart rate measured by direct electrocardiographic analysis over nine beats was 164 +/- 17. The mean lowest heart rates were 49 +/- 6 over three beats', and 56 +/- 6 over nine beats' duration. The maximum duration of heart rates less than 55/minute was 40 minutes. At their lowest heart rates 41 children (45 per cent) had junctional escape rhythms, the maximum duration of which was 25 minutes. Nine children showed PR intervals greater than or equal to 0.20 s and included three with Mobitz type I second degree atrioventricular block. Nineteen (21%) had isolated supraventricular or ventricular premature beats (less than 1/hour). Sixty subjects (65%) had sinus pauses that could not be distinguished on the surface electrocardiogram from those previously described as sinuatrial exit block or sinus arrest. The maximum duration of sinus pause measured over 24 hours on each child was 1.36 +/- 0.23 seconds. Thus apparently healthy children show variations in heart rate and rhythm over 24 hours hitherto considered to be abnormal.

Sick sinus syndrome in childhood

The clinical and electrocardiographic findings in five children with the sick sinus syndrome and an otherwise normal heart are described. There were three boys and two girls. Their age at onset of either bradycardia or symptoms ranged from 1 day to 7 years. In one patient, the youngest ever reported with this syndrome, bradycardia was noted before birth. Four children presented with neurological symptoms--attacks of dizziness, fainting spells, or syncope. One boy, treated for epilepsy before the underlying arrhythmia ws diagnosed, died suddenly while playing. One child had near-fatal syncope caused by ventricular tachycardia. Continuous 24-hour electrocardiographic monitoring is the best method of assessing the severity of the condition. Sinus bradycardia, sinuatrial block, and periods of sinus arrest up to 4.8 seconds were recorded. Two patients had associated atrioventricular block and were therefore presumed to have binodal disease. Atrial fibrillation or flutter occurred in three patients. Isolated sick sinus syndrome may be a life-threatening condition in childhood for which, in selected cases, the insertion of a permanent pacemaker is indicated.

Method for recording electrical activity of the sinoatrial node and automatic atrial foci during cardiac catheterization in human subjects

A method for recording electrical activity of the sinoatrial (S-A) node and automatic atrial foci in human subjects is described. To record S-A nodal electrograms, an electrode catheter was inserted percutaneously into the femoral vein and advanced under fluoroscopic control to the superior vena caval-right atrial junction. The distal terminal of the catheter was placed in the area of the S-A node and the proximal terminal on the free right atrial wall or in the right atrial lumen. Polarity was reversed from the conventional electrocardiographic recording; high amplification (about 100 microV/cm) and selective filters (0.1 to 20 hertz) were used. S-A nodal electrograms recorded with this method in human subjects were similar to electrograms obtained previously from the dog and rabbit and revealed negatively directed diastolic and upstroke slopes preceding the P wave of the electrocardiogram. Sinoatrial conduction time measured from the S-A nodal electrograms in 15 cases was 34.9 +/- 2.1 ms(mean +/- standard error of the mean) for a sinus cycle length of 736.4 +/- 38.6 ms. The coronary sinus electrograms in a patient with coronary sinus rhythm were recorded by the same technique except that the distal terminal of the catheter was placed at the coronary sinus ostium. A negatively directed diastolic slope preceding the P wave was consistently recorded. This method for recording electrograms of the S-A node and ectopic automatic atrial foci should prove useful in (1) assessment of both normal and abnormal S-A nodal function, (2) direct determination of conduction time from the S-A nodal pacemaker to the atrium, and (3) localization of automatic atrial foci.

Study of cardiac rhythm in healthy newborn infants

Twenty-four-hour electrocardiograms were recorded in the first 10 days of life on 134 healthy full-term infants with birthweights greater than 2.5 kg. The highest heart rate a minute, measured over nine beats, was 175 +/- 19 (SD). The lowest rates, measured over three, five, and nine beats were 82 +/- 12, 87 +/- 12, and 93 +/- 12, respectively. At their lowest rates 109 infants had sinus bradycardia and 25 had junctional escape rhythms. Thirty-three infants showed changes in P wave configuration with or without pronounced variation in PR interval. Atrial premature beats were present in 19 infants but only one had more than 12 per hour. In a randomly selected subgroup of 71 infants sinus pauses were found in 51 (72%). Five (7%) had electrocardiographic patterns and rhythm disturbances that could not be differentiated from those previously described as complete sinuatrial exit block or sinus arrest, eight (11%) had patterns indistinguishable from 2:1 sinuatrial block, and 23 (32%) had pattern indistinguishable from sinuatrial Wenckebach block. This study shows that normal infants have variations in heart rate and rhythm hitherto considered to be abnormal.