Electrophysiologic residua and sequelae of surgery for congenital heart defects

Longitudinal ECG changes in tetralogy of Fallot and association with surgical repair

Background

ECG abnormalities have been linked to adverse changes in right ventricular (RV) morphology and poor clinical outcomes in repaired Tetralogy of Fallot (rTOF). Our aim was to describe how ECG changes progress in early and intermediate follow-up and whether types of surgical strategy at the time of primary repair affected these changes.

Methods

We studied patients with rTOF born 2000-2018 operated at our institution. Seven time points in relation to primary repair, follow-up, and pulmonary valve replacement (PVR) were identified. Patients correct with valve sparing repair (VSR), trans-annular patch (TAP) including with a monocusp valve (TAP + M) and with at least 3 ECGs were included. PQ interval, QRS duration, dispersion, and fragmentation, QTc duration and dispersion, JTc as well as presence of a right bundle branch block (RBBB) were analyzed. Medical records were reviewed for demographic and surgical data.

Results

Two hundred nineteen patients with 882 ECGs were analyzed with a median follow-up time of 12.3 years (8.4, 17) with 41 (19%) needing PVR during the study period. QRS duration increased at time of primary repair to discharge from 66 msec (IQR 12) to 129 msec (IQR 27) (p < 0.0001) and at 1- and 6- year follow-up but showed only a modest and temporary decrease after PVR. QTc increased at the time of primary repair as well as prior to PVR. PQ interval showed a small increase at the time of primary repair, was at its highest prior to PVR and decreased with PVR. Type of surgical repair affected mainly QTc and JTc and was consistently longer in the TAP + M group until PVR. In VSR, QTc and JTc were prolonged initially compared to TAP but were similar after 1 year. After PVR, there were no differences in adverse ECG changes between surgical groups.

Conclusions

PQ interval and QRS duration best correspond to the assumed volume load whereas the relationship with QTc and JTc is more complex, suggesting that these represent more complex remodeling of the myocardium. Before PVR, QTc and JTc are longer in the TAP + M group which may be due to a longer surgical incision.

Preventing Arrhythmic Death in Patients With Tetralogy of Fallot: JACC Review Topic of the Week

Patients with tetralogy of Fallot are at risk for ventricular arrhythmias and sudden cardiac death. These abnormalities are associated with pulmonary regurgitation, right ventricular enlargement, and a substrate of discrete, slowly-conducting isthmuses. Although these arrhythmic events are rare, their prediction is challenging. This review will address contemporary risk assessment and prevention strategies. Numerous variables have been proposed to predict who would benefit from an implantable cardioverter-defibrillator. Current risk stratification models combine independently associated factors into risk scores. Cardiac magnetic resonance imaging, QRS fragmentation assessment, and electrophysiology testing in selected patients may refine some of these models. Interaction between right and left ventricular function is emerging as a critical factor in our understanding of disease progression and risk assessment. Multicenter studies evaluating risk factors and risk mitigating strategies such as pulmonary valve replacement, ablative strategies, and use of implantable cardiac-defibrillators are needed moving forward.

Morphological Substrates for Atrial Arrhythmogenesis in a Heart With Atrioventricular Septal Defect

Due to advances in corrective surgery, congenital heart disease has an ever growing patient population. Atrial arrhythmias are frequently observed pre- and post-surgical correction. Pharmaceutical antiarrhythmic therapy is not always effective, therefore many symptomatic patients undergo catheter ablation therapy. In patients with atrioventricular septal defects (AVSD), ablation therapy itself has mixed success; arrhythmogenic recurrences are common, and because of the anatomical displacement of the atrioventricular node, 3-degree heart block post-ablation is a real concern. In order to develop optimal and safe ablation strategies, the field of congenital cardiac electrophysiology must combine knowledge from clinical electrophysiology with a thorough understanding of the anatomical substrates for arrhythmias. Using image-based analysis and multi-cellular mathematical modeling of electrical activation, we show how the anatomical alterations characteristic of an AVSD serve as arrhythmogenic substrates. Using ex-vivo contrast enhanced micro-computed tomography we imaged post-mortem the heart of a 5 month old male with AVSD at an isometric spatial resolution of 38 μm. Morphological analysis revealed the 3D disposition of the cardiac conduction system for the first time in an intact heart with this human congenital malformation. We observed displacement of the compact atrioventricular node inferiorly to the ostium of the coronary sinus. Myocyte orientation analysis revealed that the normal arrangement of the major atrial muscle bundles was preserved but was modified in the septal region. Models of electrical activation suggest the disposition of the myocytes within the atrial muscle bundles associated with the "fast pathway," together with the displaced atrioventricular node, serve as potential substrates for re-entry and possibly atrial fibrillation. This study used archived human hearts, showing them to be a valuable resource for the mathematical modeling community, and opening new possibilities for the investigations of arrhythmogenesis and ablation strategies in the congenitally malformed heart.

Very long-term outcome of catheter ablation of post-incisional atrial tachycardia: Role of incisional and non-incisional scar

BACKGROUND

The arrhythmogenicity of right atrial (RA) incisional scar after cardiac surgery could result in atrial tachycardia (AT). Radiofrequency catheter ablation is effective in the treatment of such tachycardia. However, data regarding long-term outcomes are limited.

METHODS AND RESULTS

A total of 105 patients with prior RA incision who underwent radiofrequency catheter ablation of AT were included. In the first procedure, electroanatomic mapping (EAM) revealed a total of 139 ATs in 105 patients, including 88 cavotricuspid isthmus dependent atrial flutters (IDAFs), 5 mitral annulus reentrant tachycardias (MARTs), 44 intra-atrial reentrant tachycardias (IARTs) and 2 focal ATs (FATs). AT was successfully eliminated in 101 (96.1%) patients. During a mean follow-up period of 90 ± 36 months, recurrent AT was observed in 23 patients and 21 underwent a second ablation. A total of 23 ATs were identified in redo procedures including 4 IDAFs, 2 MARTs, 12 IARTs and 5 FATs. The time to recurrence was significantly different among various AT types. Acute success was achieved in 20 of 23 redo procedures. Taking a total of 21 patients presenting atrial fibrillation during follow-up into account, 85 patients (81.9%) were in sinus rhythm. No complications except for a case of RA compartmentation occurred.

CONCLUSION

RA incisional scar played an essential role in promoting both IDAF and IART, while non-incisional scar contributed to a substantial rate of late recurrent AT in forms of both macroreentry and small reentry. Catheter ablation using EAM system resulted in a high success rate during long-term follow-up.

Arrhythmias in adult congenital heart disease

Recent advances in pediatric cardiology and cardiac surgery have allowed a rapidly expanding population of patients with congenital heart disease to thrive well into their adult years. Often after prolonged uneventful clinical courses as children and adolescents, arrhythmias may surface later in life. These arrhythmias are a major source of morbidity. In addition, sudden death is the leading cause of mortality in adult patients with congenital heart disease. This review highlights the various types of brady- and tachyarrhythmias encountered in the more common forms of adult congenital heart disease and explores prognostic implications and therapeutic options.

QTc Prolongation after Ventricular Septal Defect Repair in Infants

Background and Objectives

Prolonging of the corrected QT interval (QTc) has been reported after cardiac surgery in some studies. However, there have not been many studies on infant open cardiac surgery for ventricular septal defect (VSD) repair. This study was performed to define the changes in QTc and to find related post-surgery factors in this patient group.

Subjects and Methods

From 2008 to 2012, 154 infants underwent VSD repair at the Severance Cardiovascular Hospital. This study includes 105 of these cases. QTc was measured in these patients retrospectively. Demographic data and peri-procedural data, such as Aristotle score, cross-clamp time and bypass time, were analyzed. The exclusion criteria included multiple and small VSDs that underwent direct closure.

Results

Mean post-operative QTc was increased compared to the pre-operative measurements (from 413.6±2.3 to 444.9±2.5, p<0.001). In multiple linear regression, the comprehensive Aristotle score was associated with increasing QTc (p=0.047). The incidence of transient arrhythmia, such as atrial tachycardia, junctional ectopic tachycardia, premature atrial contraction, or premature ventricular contraction, was associated with QTc prolongation (p=0.005). Prolonged QTc was also associated with cross-clamp time (p=0.008) and low weight (p=0.042). Total length of stay at the intensive care unit and intubation time after surgery were not associated with QTc prolongation.

Conclusion

Prolonged QTc could be seen after VSD repair in infants. This phenomenon was associated with peri-procedural factors such as the Aristotle score and cross-clamp time. Patients with QTc prolongation after cardiac surgery had an increased tendency towards arrhythmogenicity in the post-operative period.

Long-term outcome after ablative therapy of postoperative atrial tachyarrhythmia in patients with congenital heart disease and characteristics of atrial tachyarrhythmia recurrences

BACKGROUND

Catheter ablation has evolved as a possible curative treatment modality for atrial tachyarrhythmia (AT) in patients with congenital heart defects (CHD). However, data on long-term outcome are scarce. We examined characteristics of recurrent AT after ablation of postoperative AT during long-term follow-up in CHD patients.

METHODS AND RESULTS

CHD patients (n=53; 27 men; age, 38+/-15 years) referred for catheter ablation of AT were studied during a follow-up period of 5+/-3 years. After ablative therapy of the first AT (n=53, 27 atrial flutter, cycle length=288+/-81 ms; 22 intra-atrial reentrant tachycardia, cycle length=309+/-81 ms; 5 focal atrial tachycardia, cycle length=380+/-147 ms; success rate, 65%), AT recurred (59% within the first year) in 29 patients; 15 underwent repetitive ablative therapy. Mechanisms underlying recurrent AT were similar in 7 patients (intra-atrial reentrant tachycardia, 2; atrial flutter, 5). The location of arrhythmogenic substrates of recurrent AT (intra-atrial reentrant tachycardia, focal atrial tachycardia) was different for all but 1 patient. After 5+/-3 years, 5 patients died of heart failure, 3 were lost to follow-up, and the remaining patients had sinus rhythm (n=31), AT (n=5), or atrial flutter (n=14). Antiarrhythmic drugs were used by 18 (57%) sinus rhythm patients.

CONCLUSIONS

Successive postoperative AT in CHD patients developing over time may be caused by different mechanisms, including focal and reentrant mechanisms. Recurrent AT originated from different locations, suggesting that these new AT were not caused by arrhythmogenicity of previous ablative lesions. Long-term outcome is often complicated by development of atrial fibrillation. Despite frequent need for repeat ablative therapy, most patients are in sinus rhythm.

Long term results after operative treatment of isolated ventricular septal defect in adolescents and adults

A series of 125 consecutive patients with isolated ventricular septal defect (VSD) aged 10 or over, were followed until death or beyond the age of 30 (31-73) years. A prospective restudy was performed after a mean follow-up of 15 (3-21) years. Forty-one patients (group 1) were treated with surgical repair of VSD at a mean age of 23 (10-51) years, and early mortality was 10%, i.e. 3 with severe aortic insufficiency and one with systemic pulmonary artery pressure. Surgery was initially not regarded indicated in 70 patients with small defects (group 2). A further 14 patients were judged inoperable (group 3). Long-term mortality was 5% in group 1, 9% in group 2 and 71% in group 3. When restudied, group 2 patients had significantly higher (p less than 0.01) and group 1, lower (p less than 0.01) pulmonary artery pressures than initially. A moderate deterioration in NYHA-rating was noted in group 2 (p less than 0.05) vs. a slight improvement in group 1 (p less than 0.05). The non-operated patients had a higher incidence of valvular lesions (19% vs. 13%) and bacterial endocarditis (4.3% vs. 2.7%) than the operated but not to a statistically significant level. Spontaneous closure was 6% in group 2 whereas mostly small residual defects were found in 34% of the operated. Patients with uncomplicated VSDs (absence of valvular lesions or coronary heart disease) had subnormal exercise tolerance as judged from a standardized ergometer bicycle test. These patients also had impaired left ventricular function based upon haemodynamic studies during moderate supine exercise. No major differences were noted between groups 1 and 2, but operated patients with residual VSDs tended to have the poorest cardiac performance. Non-cardiac disease represented only a minor problem and no significant differences in psychosocial function were observed between groups 1 and 2. Only 50% in group 1 and 60% in group 2 attended a regular medical clinic. Antibiotic prophylaxis had only been practiced by 50% in both groups. Although small, but differences between groups 1 and 2 favour surgery. This must be regarded as a positive result of surgical treatment since those operated on had basically larger and thus more severe defects than the others. In view of the very low operative risk associated with modern surgical technique one should direct patients with significant shunts to operative treatment.

Postoperative ventricular tachycardia in patients with congenital heart disease: diagnosis and management

Ventricular tachycardia (VT) after palliative repair of congenital heart disease is relatively rare. Despite this rarity, VT is a known cause of early, intermediate and late morbidity and mortality in these patients. A number of factors have been linked to the development of VT in this unique patient population. The purpose of this article is to provide a concise overview regarding the etiology, diagnosis and treatment of VT in patients with congenital heart disease. In-depth information will be provided to aid diagnosis and the treatment of early postoperative VT. The use of additional diagnostic methods such as echocardiography, cardiac catheterization and electrophysiology studies to risk assess patients with postoperative VT will also be discussed. In addition, I examine the long-term management strategies for VT in these patients, from medical management and cardiovascular surgery to implantation of cardioverter-defibrillators.

Guidelines for the outpatient management of complex congenital heart disease

An increasingly complex group of children is now being followed as outpatients after surgery for congenital heart disease. A variety of complications and physiologic perturbations, both expected and unexpected, may present during follow-up, and should be anticipated by the practitioner and discussed with the patient and family. The purpose of this position article is to provide a framework for outpatient follow-up of complex congenital heart disease, based on a review of current literature and the experience of the authors.

[Results of the surgical closure of ventricular septal defects of various ages: report of 30 cases]

OBJECTIVE

To appreciate short and midterm results of patients after surgical closure of the ventricular septal defect.

MATERIAL AND METHODS

The study is retrospective and took place in the department of cardiovascular surgery "B", Ibn-Sina hospital, Rabat, Morocco. Between 1995 and 2005, 30 patients underwent a surgical closure of ventricular septal defect. Eighteen patients (60%) were males and twelve (40%) were females with a mean age of 10 years (18 months-36 years). Seven patients (23%) were older than 16 years. All of ventricular septal defects were type 2, unique and most of them perimembranous (70%). Four patients (13%), were older than 16 years, had a significant aortic insufficiency that has dictated the aortotomy for ventricular septal defect repair. The surgical approach through the right atriotomy was sufficient for complete repair in 22 patients (73%). Closure of the defect has been done using a pericardial autologous patch in 28 patients (93%).

RESULTS

No operative mortality was observed. The mean follow-up was five years. Eight patients (26%) had a residual ventricular septal defect that progressed to spontaneous closure. Two patients (6%) had a residual pulmonary hypertension and two others a moderate aortic regurgitation. The four patients were older than 16 years. Echocardiography showed a significant reduction in left ventricular dimension and systolic pulmonary artery pressure. At last follow-up, 87% of the patients were in NYHA class 1.

CONCLUSION

This study demonstrates that surgical closure of ventricular septal defect ensures a good outcome in short and midterm. Nevertheless, the risk of delayed complications justifies long-term and regular follow-up.

Pacing in adults with congenital heart disease

Adults with congenital heart disease constitute one of the fastest growing populations in cardiology. Pacing is an integral part of their therapy and may reduce their morbidity and mortality significantly. The current generation of pacemakers is more sophisticated and complex, and they are being utilized for indications other than conduction abnormalities, such as termination of tachycardia and improvement of heart failure. The complex anatomy and history of multiple previous surgeries in adults with congenital heart disease, however, pose many limitations and technical challenges related to the placement of a pacemaker. Unique and innovative approaches to endocardial lead placement and improved epicardial leads is making pacemaker implantation more feasible in these patients.

Modification of the radial procedure in a patient with partial atrioventricular septal defect

We successfully cured atrial fibrillation while preserving internodal conduction in a patient with a partial atrioventricular septal defect. Because the anterior and middle internodal tracts are interrupted by the defect, the lower right atrial incision of either the maze or the radial procedure may interrupt the remaining posterior tract, resulting in internodal conduction block. We deleted the posterior septal incision from the radial procedure and replaced it with a right-side left atriotomy. The patient resumed normal sinus rhythm with significant contraction of the right and left atria. The preserved internodal pathway through the posterior interatrial septum was confirmed by electrophysiologic study.

Sinus node dysfunction and atrial tachycardia after the Fontan procedure: The scope of the problem

Similar to other atrial baffling procedures, the Fontan procedure exposes patients to ongoing morbidity and mortality. The development of the bradycardia-tachycardia syndrome can have adverse effects on already-marginal hemodynamics and ventricular function. Patients with Fontan physiology and sinus node dysfunction can be managed with antibradycardic pacemakers. Atrial arrhythmias after "completion Fontan" are difficult to treat and usually require either antiarrhythmic agents, antitachycardic pacemakers, or radiofrequency catheter ablation of the re-entrant circuit. Successful treatment of atrial flutter occurs in only 50% to 70% of patients. There is a high recurrence rate of atrial flutter with any of the accepted management strategies. Copyright 1998 by W.B. Saunders Company

Preventing sudden death after repair of tetralogy of Fallot: complex therapy for complex patients

Sudden arrhythmic death in patients with repaired tetralogy of Fallot or its variants has a variety of causes. Consequently, it can serve as a paradigm for management of potentially malignant arrhythmias in all pediatric patients, particularly with regard to the use of nonpharmacologic therapy for management. Five cases are presented as touchpoints for discussion and demonstrate a number of important issues concerning the assessment and reduction of sudden cardiac death risk in these patients. First, there are no clinical parameters that can be used to accurately assess risk. Second, pharmacologic agents alone rarely are adequate therapy. Third, catheter ablation and antitachycardia devices continue to play an ever increasing role in management of these patients, and, finally, additional data are necessary to establish clear management guidelines in patients with congenital heart disease at risk for arrhythmic death.

[Arrhythmias in patients with congenital heart disease and their impact on prognosis]

Patients with congenital heart disease have an increased chance to suffer from brady- as well as tachyarrhythmias. The impact of these on quality of life, morbidity and mortality is more often imperative as compared to heart-healthy individuals. The substrate for these may be either congenital or acquired. Improvements of the surgical management of these patients have led, on the one hand, to improved survival rates with prolonged life expectancy within the last 2 decades, which on the other hand provided the basis for a higher rate of acquired cardiac arrhythmias. Together, this not only challenges diagnostics and therapy but also the prognostic relevance of these arrhythmias. The therapeutic strategies and prognostic markers have until now mostly been based on retrospective studies limited by the low number of patients and inhomogeneous patient selection. Despite these limitations, an increased risk of sudden cardiac death has been substantiated for certain patient groups, e.g., those operated on by the Mustard- or Senning procedures in patients with transposition of the great arteries and patients operated on with correction of the tetralogy of Fallot. However, until now it has not been possible to identify reliable markers for establishing the risk on an individual basis within these patient cohorts. For achieving reliable data on the symptomatic and prognostic effects of present-day--as well as new-coming--therapeutic strategies, it is mandatory to perform prospectively based, randomized multicenter studies. Furthermore, the well-appreciated synergism of hemodynamically and primarily of arrhythmia-based effects on prognosis could potentially be divided into their relative weight to better guide appropriate, substrate-related therapy. In addition, this should help to get better estimates of the risk for sudden cardiac death in different, etiologically homogeneous, groups of patients with congenital heart disease.

Radiofrequency catheter ablation of right ventricular tachycardia late after repair of congenital heart defects

BACKGROUND

Ventricular arrhythmias after repair of congenital heart defects are a common finding and possibly contribute to sudden death in these patients. Optimal antiarrhythmic management has not yet been defined.

METHODS AND RESULTS

The study population consisted of 16 patients in whom ventricular arrhythmias occurred 11 to 42 years after complete surgical repair of congenital heart defects. Fifteen patients had a history of symptomatic sustained or nonsustained ventricular tachycardia, and 1 had frequent nonsustained ventricular tachycardia. The diagnostic mapping procedure to identify the origin of the arrhythmia included pace mapping during sinus rhythm, activation mapping, and pacing interventions during ventricular tachycardia. Catheter ablation was carried out by means of radiofrequency energy in the temperature-controlled mode. The follow-up period was 6 to 33 months (mean, 16 months). A right ventricular origin of the tachycardia in the surgically corrected area could be determined in all patients. Catheter ablation was carried out without complications. Immediate noninducibility was achieved in 15 of the 16 patients. One patient in whom the tachycardia was again inducible at repeat stimulation 1 week later was successfully treated with amiodarone. Eleven patients were taken off antiarrhythmic drugs. During follow-up, none of them had a recurrence of the tachycardia that had been ablated.

CONCLUSIONS

In patients with symptomatic or frequent ventricular tachycardia late after complete surgical repair of congenital heart defects, catheter ablation by means of radiofrequency energy is feasible and safe and thus might be taken into consideration for these patients. Short-term follow-up results are promising.

The adult patient with congenital heart disease

In adults with congenital heart disease who are confronted with noncardiac surgery, perioperative risks can be reduced, often appreciably, when problems inherent to this patient population are anticipated. The first necessity is to clarify the diagnosis and to be certain that appropriate information is obtained from a cardiologist with adequate knowledge of congenital heart disease in adults. Physiology and anatomy can vary significantly among patients who superficially carry identical diagnoses. Elective noncardiac surgery should be preceded by clinical assessment including review of clinical and laboratory data and securing the results of necessary diagnostic studies. Preoperative assessment should be performed far enough in advance of the anticipated date of surgery to allow critical assessment of the data and potential discussions with colleagues. Appropriate cardiovascular laboratory studies to be obtained or reviewed include electrocardiograms, chest radiographs, echocardiograms, and cardiac catheterization data, which may include specialized intracardiac electrophysiologic testing. Congenital heart disease in adults is a new and evolving area of special interest and expertise in cardiovascular medicine. Multidisciplinary centers for the care of these patients are being developed. The 22nd Bethesda Conference recommended that these centers include among their consultants anesthesiologists with special expertise in managing patients with congenital heart disease. These anesthesiologists can have the option of serving either as the attending anesthesiologists when patients require noncardiac surgery or as consultants and resource individuals to other anesthesiologists.

Ventricular tachycardias with left bundle branch block morphology

The differential diagnosis of VTs with LBBB morphology includes several well-defined syndromes. Although the majority of cases are attributable to acquired structural heart disease, including ischemia, prior infarction, or dilated cardiomyopathy, consideration of specific right ventricular processes is essential to proper evaluation and treatment. The approach to older patients or those with evidence for heart disease should begin with an evaluation for coronary artery disease and an assessment of biventricular function. Careful evaluation for bundle branch reentry should be performed during electrophysiological study, especially when there is underlying conduction system disease. Younger patients, those without overt heart disease, or those with isolated right ventricular disease, should receive a complete noninvasive evaluation of right and left ventricular size and function. An abnormal SAECG or identification of intracardiac late potentials suggest right ventricular dysplasia or cardiomyopathy, whereas responsiveness to adenosine and absence of detectable heart disease support the diagnosis of idiopathic right VT. Newer techniques, including MRI, show promise in identifying subtle right ventricular disease not otherwise detectable even in the setting of presumed idiopathic right VT. Following surgical repair of selected congenital heart defects, particularly tetralogy of Fallot, symptoms of recurrent palpitations, near syncope, syncope, or aborted sudden death may be attributable to recurrent VT, and diagnostic electrophysiological study should be considered for these patients. Finally, SVTs with LBBB morphology, particularly cases associated with right-sided or septal accessory pathways, should always be considered in this differential diagnosis.

Long-term follow-up (9 to 20 years) after surgical closure of atrial septal defect at a young age

To assess the long-term cardiac status after surgical closure of an atrial septal defect (ASD) at a young age, 104 of 135 children who consecutively underwent surgery (aged 0 to 14 years) at 1 institution between 1968 and 1980 participated in a follow-up study and underwent a complete cardiologic examination. Mean follow-up was 14.5 +/- 2.8 years. Most patients (87%) believed their health to be good or very good. At physical examination, all patients were in good health. Ninety-three patients (89%) were in sinus rhythm. Echocardiography showed that right ventricular dilatation was present in 27 patients (26%), 2 of whom had a residual ASD. Bicycle ergometry revealed that 88 patients (88%) had a normal exercise capacity. Both supraventricular and ventricular arrhythmias were observed in 67% of patients by 24-hour ambulatory electrocardiography, but only 3 (3%) had received antiarrhythmic medication, and 4 (4%) had needed a pacemaker. In the group of patients with right ventricular dilatation, the exercise capacity and prevalence of arrhythmias did not differ significantly from those in the group with a normal sized right ventricule. The outcome in patients with a secundum-type ASD was not different from that of those with a sinus venosus-type ASD. The finding of anatomic, functional or electrophysiologic abnormalities was not associated with a longer duration of follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Ambulatory arrhythmia screening in symptomatic children and young adults: comparative effectiveness of Holter and telephone event recordings

Effective initial identification of potential cardiac arrhythmias in symptomatic children is difficult due to the infrequency, brief duration, and vague nature of subjective complaints in the young. Although both telephone event and Holter monitoring are used for this purpose, no comparative studies of the initial screening efficacy of either have been performed. A total of 202 consecutive symptomatic children (age 11 days to 26 years, mean 10.2 years) were evaluated for potential cardiac arrhythmias with either 24-h Holter (97 patients) or telephone event (105 patients) recorders and grouped according to the presence or absence of congenital heart defects, normal or abnormal resting electrocardiogram (ECG), and presence or absence of cardiac surgery. The results showed 30% of all recordings (61% event; 14% Holter) failed to substantiate any arrhythmias in spite of subjective symptoms. Event recordings showed a better correlation of sensed symptoms with arrhythmias (32%) compared to Holters (5%) (p < 0.01) with 73% of Holter recordings performed during both asymptomatic and arrhythmia-free 24-h periods. Holter monitoring was more effective in detecting nonsensed and asymptomatic events (8% versus 0.5%, (p < 0.01), among high-risk children. This study demonstrates that although both monitoring devices are applicable to children, each has inherent limitations and usefulness. These must be considered in choosing either device to permit their most optimal and cost-effective application.

Supraventricular tachyarrhythmias, congenital heart disease, and sudden cardiac death

The etiologies of sudden cardiac death following the surgical treatment of congenital heart defects remain uncertain. A young patient with prior repair of partial anomalous pulmonary venous return is presented, in whom brief episodes of a supraventricular tachyarrhythmia (rate 170/min) were documented to result in ventricular fibrillation. This unusual sequence may represent a basis for unexplained sudden cardiac death in other patients following atrial surgical procedures for the treatment of congenital heart disease.

Electrophysiologic evaluation of sinus node dysfunction in postoperative children and young adults utilizing combined autonomic blockade

Sinus node dysfunction is a recognized problem following surgery for congenital heart disease. Seven postoperative patients with sinus node dysfunction (5 Mustard, 1 tetralogy of Fallot, 1 Fontan) underwent electrophysiology study of sinus node function during combined autonomic blockade (CAB) utilizing propranolol 0.2 mg/kg i.v. and atropine 0.04 mg/kg i.v. to evaluate intrinsic sinus node function isolated from autonomic control. During CAB, intrinsic heart rate, intrinsic corrected sinus node recovery time, and intrinsic sinoatrial recovery time were measured. These results were compared with age-matched normal intrinsic data from our lab [normal (n = 7, mean age 9 years) IHR 128 +/- 24, intrinsic corrected sinus node recovery time 135 +/- 40 ms, intrinsic sinoatrial conduction time 86 +/- 19 ms]. Among postoperative Mustard patients (n = 5, mean age 13 years, mean years postoperative 11) 2 of 5 had clearly abnormal intrinsic sinus node function with nonsinus rhythm during CAB; 3 of 5 had sinus rhythm during CAB with normal or mildly abnormal intrinsic sinus node function. The postoperative case of tetralogy of Fallot (age 20 years, postoperative 14 years) had mildly abnormal intrinsic sinus node electrophysiology study. The postoperative case of Fontan (age 16 years, postoperative 1.5 years) had sinus rhythm at rest but left atrial rhythm during CAB. Different aspects of sinus node dysfunction may be expressed during resting electrophysiology study vs. electrophysiology study utilizing CAB. The pathophysiology of sinus node dysfunction among postoperative pediatric patients is not homogeneous with regard to the contribution of intrinsic sinus node dysfunction. In those patients with normal or mildly abnormal intrinsic sinus node function, an important pathophysiologic influence of the autonomic nervous system is implicated.

Bradycardia-mediated tachyarrhythmias in congenital heart disease and responses to chronic pacing at physiologic rates

The coexistence of bradycardia and a tachyarrhythmia may preclude effective pharmacologic treatment of 1 arrhythmia without paradoxic aggravation of the other. This study evaluated the potential relation between the 2 types of arrhythmias and the effect of conventional modes and rates of pacing for bradycardia on the frequency of the associated tachyarrhythmias. Twenty-one young patients, aged 2 to 19 (mean 11) years with congenital heart disease and a tachyarrhythmia occurring in the setting of chronic bradycardia were studied. The effects of pacing were evaluated by comparison of the number of episodes of clinical tachycardia during the 12-month intervals before and after pacemaker implantation. During these intervals, antiarrhythmic drug therapy was not altered. Patients were analyzed as independent groups, based on the type of tachyarrhythmia: supraventricular (n = 5), atrial flutter (n = 9) and ventricular (n = 7). The modes of chronic pacing were AAI (n = 4), DDD (n = 6) and VVI (n = 11). The prevention of bradycardia by pacing was associated with a significant decrease in the frequency of supraventricular (p = 0.008) and ventricular (p = 0.02) tachyarrhythmias. However, the frequency of atrial flutter was not altered. Prevention of tachycardia was more frequently associated with the AAI and DDD modes of pacing compared to VVI (p = 0.08). Pacing represents an effective therapy for certain tachyarrhythmias associated with chronic bradycardia, although critical modes may be required.

Atrial pacing to estimate total sinoatrial conduction time in children

No data exist concerning the total sinoatrial conduction time (TSACT) in children that compare values determined by the atrial extrastimulation technique (TSACTS) with those generated by the atrial pacing method (TSACTN). In this study, TSACT in 55 patients, age 0.2-18.5, was measured using both techniques. TSACTN was performed at a mean 90% (TSACTN-90) (n = 32) or a mean 95% (TSACTN-95 and (n = 38) of sinus cycle length (SCL). When data generated during determination of TSACTN-90 and TSACTS were compared, SCL and recovery cycle length (REC) were similar for both techniques. Likewise, TSACTS (128 +/- 40 ms) and TSACTN-90 (126 +/- 74 ms) were not significantly different. Coefficient of correlation was r = 0.82, p less than 0.001. Chi-square analysis demonstrated a strong association of normal and abnormal values between TSACTS and TSACTN-90. In contrast, when values generated during TSACTN-95 and TSACTS were compared, TSACTS exceeded TSACTN-95 (137 +/- 38 vs 105 +/- 58 ms; p less than 0.001). Values for SCL and REC were similar while correlation between TSACT determined by the two techniques remained strong (r = 0.82, p less than 0.001). Despite a good correlation between TSACTN-90 and TSACTS, individual differences in magnitude and direction were noted between the two techniques. In summary, TSACTN-90 approximates TSACTS in children. TSACTN-90 is preferable to TSACTN-95, probably due to more complete sinus node capture during atrial pacing. However, the behavior of the sinus node in response to extrastimuli (single or train) precludes favoring one technique over the other. More precise evaluation of sinoatrial conduction will require direct recording of sinus node activity.

Frequency of ventricular late potentials and fractionated right ventricular electrograms after operative repair of tetralogy of Fallot

This study was conducted to assess the incidence of abnormalities of ventricular depolarization in sinus rhythm after repair of tetralogy of Fallot and their relation to spontaneous ventricular arrhythmias. Forty-four patients were studied, 10 before surgery (mean age 6.9 years) and 34 after repair (mean age 8.1 years, mean age at surgery 6.5 years, mean interval between surgery and evaluation 11 months). Evaluation was performed by means of body surface and intracavitary signal-averaging techniques, by recording local right ventricular (RV) electrograms at several sites and by 24-hour Holter monitoring (n = 28). No electrophysiologic abnormality was observed in children before surgery. Ventricular late potentials were detected in 18 patients (53%) after repair. Body surface detection of ventricular late potentials was frequently masked by the postoperative right bundle branch block pattern. Local RV electrograms were fractionated in 11 cases (32%) (mean duration 103 +/- 33 ms), most often in the RV outflow tract (n = 9), but no relation was found between fragmentation of RV electrograms and the presence of ventricular late potentials. Spontaneous ventricular arrhythmias occurred in 12 children after repair (43%), but were complex in only 4 patients (14%). There was no correlation between spontaneous ventricular arrhythmias and the presence of ventricular late potentials, presence of fractionated RV electrograms, presence of a proximal right bundle branch block or postoperative hemodynamic status.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

Pre- and postoperative electrophysiologic assessment of children with secundum atrial septal defect

Sinus node (SN) and atrioventricular node (AVN) dysfunction after repair of atrial septal defect (ASD) may be caused by inherent nodal abnormalities and not related to altered hemodynamics. To assess the preoperative prevalence and postoperative persistence of nodal dysfunction, 21 consecutive children, mean age 5.4 years, underwent electrophysiologic evaluations before ASD repair. Preoperative SN recovery time was prolonged in 11 patients and was associated with abnormal AVN response to rapid atrial pacing in 5. There were no significant differences in age, hemodynamic values or shunt size between children with normal and those with abnormal nodal function. Atrial and AVN refractory periods were normal. The ASD was repaired in 9 children with SN dysfunction. Electrophysiologic studies performed 4 to 16 months after surgical correction showed improvement in all electrophysiologic values. However, SN function remained abnormal. Significant decreases were observed in atrial (p less than 0.05) and AVN (p less than 0.05) refractory periods, with increased atrial conduction velocity (p less than 0.01) and AVN Wenckebach response to atrial pacing (p less than 0.01). ASD repair improved nodal and atrial muscle electrophysiologic function, theoretically by relieving stress on atrial impulse propagation. SN and AVN dysfunction may persist as an inherent part of the ASD complex.

Tetralogy of Fallot after surgery: autopsy review of 14 cases

The possible determinants of a fatal outcome following surgical repair of the tetralogy of Fallot were analyzed by postmortem examination in 14 cases. Only one patient died late in the postoperative period, due to patch detachment; the others died shortly after undergoing surgery. Death could not be explained in three cases. In three patients with perimembranous ventricular septal defects, complete atrioventricular block occurred as a consequence of traumatic disruption of the branching bundle. In four cases residual stenosis of the pulmonary outflow tract was shown; in one of these cases adequate relief of obstruction had been prevented by a large conal coronary artery. A residual mitral cleft was found in one patient. Death was not related to the cardiac conditions in two cases; one of these patients died of brain apoplexy and the other of tracheal hemorrhage. These findings stress the need for accurate preoperative diagnosis and precise knowledge of the surgical anatomy of this malformation.

Arrhythmias in pediatric patients

The six most common arrhythmias or conduction disturbances in children are discussed. For each arrhythmia, the electrocardiographic criteria in children, the common clinical situations in which the arrhythmias are see, the diagnostic work-up, the suggested treatment, and prognosis are presented. Throughout, the differences between children and adults are emphasized.

Life threatening ventricular tachycardias in late survivors of surgically corrected tetralogy of Fallot

Electrophysiological tests were performed in three patients with surgically corrected tetralogy of Fallot (mean age at evaluation 25 years, mean age at surgical correction 4 years) who had had either a cardiac arrest or transient neurological disturbances (presyncope, syncope) associated with ventricular arrhythmias. All three patients had an excellent haemodynamic result from surgery as judged by echocardiography and cardiac catheterisation. Ambulatory electrocardiographic monitoring and stress exercise testing were normal in two patients and showed complex ventricular ectopy in one. During invasive electrophysiological evaluation all three patients had inducible ventricular tachycardia (monomorphic QRS in two patients, cycle lengths 230 and 240 ms; polymorphic QRS in one patient, mean cycle length 200 ms) with adverse haemodynamic effects in all three patients. These findings suggest that rapid ventricular tachycardia with detrimental haemodynamic consequences, similar to that induced during laboratory study, was the basis for the presenting symptoms in each patient. This possibility was confirmed in one patient who had identical QRS morphology during both spontaneous ventricular tachycardia and that induced during the laboratory study. Thus sudden death or symptoms of syncope postoperatively in patients with surgically corrected tetralogy of Fallot appear to be due to rapid ventricular tachycardia, which may occur despite an apparently excellent surgical result.