Surgical Repair Of Congenital Heart Disease Research Articles

Evaluation of Heart Rate Variability in Children with Congenital Heart Diseases before and after Surgical Repair

Background: Surgical repair of congenital heart diseases (CHD) affects heart rate variability (HRV) in different ways. It leads to varying degrees of cardiac autonomic derangement, clinically detectable as depression of HRV parameters. The aim of this work was to evaluate HRV in children with CHDs before and after surgical repair to detect the effect of CHDs (acyanotic or cyanotic) and cardiac surgery on cardiac autonomic function.
 Methods: This observational case-control study enrolled thirty cases with CHD. Cases were divided in two equal groups: group1 included children with CHDs (not repaired) before surgical intervention and group 2 included children after surgical repair of CHDs. Another fifteen healthy children, matched for age and sex, were enrolled as a control group. All children in this study were subjected to full history taking, clinical evaluation, Holter monitor, twenty-four-hour ambulatory electrocardiographic recordings and the seven time-domain indices of HRV.
 Results: There was significant increase of HR in patients before surgical repair as compared to patients after surgical repair as compared to control group. There was significant decrease of PNN50, r MMSD, SDNN index and SDANN of children before surgical repair as compared to children after surgical repair as compared to controls. There was a negative significant correlation between HR and age before surgery, after surgery there was a negative significant correlation between HR and age, pNN50, rMMSD, SDNN index and SDANN, in control there was negative significant correlation with age, SDNN index, SDANN and SDNN.
 Conclusion: HRV parameters increased significantly in children with CHDs after surgical repair as compared to these before surgical repair denoting effect of cardiac surgery on cardiac autonomic function.

Infective Endocarditis with Multiple Valvar Vegetation in Uncorrected Tetralogy f Fallot: A Case Report of Rare Condition

Objective: To describe a case of an adult patient with uncorrected Tetralogy of Fallot (TOF) who suffered from Infective Endocarditis (IE) that involved the tricuspid and aortic valves. Methods: On October 2019, a-twenty-year-old male with uncorrected TOF was admitted to the emergency department of Dr. Hasan Sadikin General Hospital with a chief complaint of fever. The echocardiography showed the presence of vegetation on the tricuspid valve and aortic valve. The patient was given empirical antibiotics therapy for IE treatment. The serial blood cultures did not yield any organism growth and the transthoracic echocardiography evaluation showed healed vegetation after 21 days of antibiotics treatment. Results: A high turbulence in small VSD and valvular stenosis, as found in TOF, can injure the endocardial surface. While bacterial adherence to the injured endocardial surface can cause IE, no specific criteria available for diagnosing IE in congenital heart disease (CHD) patients compared to other population. In CHD patients, it is necessary to consider the diagnosis of IE presenting with signs of infection or fever. Our patient was known to have uncorrected TOF and was admitted to the hospital with a chief complaint of fever. The uncorrected TOF was complicated by an unusual form of aggressive vegetation involving multiple valves. Conclusion: The incidence of IE in uncorrected TOF is around 4%. Patient is advised to receive a corrective surgery for the cardiac anomaly. Surgical repair of CHD with no residual lesion reduces the risk of IE.

Abstract 17205: The Association of Cerebrovascular Autoregulation With Neurodevelopmental Delays Between Infants With and Without Congenital Heart Disease

Background: Children with Congenital Heart Disease ( CHD ) are 5 times more likely to develop neurodevelopmental impairment lasting into adulthood compared to their peers. One theory is that hypoxemia associated with CHD contributes to impaired cerebrovascular autoregulation ( CA ), which in turn may contribute to neurological injuries and impaired neurodevelopmental outcome ( NDO ) in CHD. This study examined the association of CA and NDO between CHD and healthy infants. Hypothesis: Impaired CA will be associated with poorer NDO in CHD infants through 9-month development. Methods: A prospective, longitudinal study was performed at 3, 6, & 9-month time points. CA was indexed by calculating the difference between 2-minute averaged supine and sitting cerebral oxygenation (rcSO 2 ) measured by near-infrared spectroscopy for 3 consecutive tilts (0-90°), resulting in change scores. The Bayley Scales of Infant and Toddler Development III measured NDO. Multiple linear regressions quantified the group-by-CA interaction on NDO at each age. Results: We enrolled 35 CHD and 26 healthy control ( HC ) infants. 3 months: As CA worsened (change score in rcSO 2 increased by 1-unit), cognitive compositive scores decreased by 2.6% in the CHD group compared to the HC during the 3 rd postural change (P=0.003). 6 months: As CA worsened, the language composite scores decreased by 3.7% in the CHD group at compared to the HC for the 1 st postural change (P=0.041). 9 months: As CA worsened, the cognitive composite scores decreased by 2.7% in the CHD group compared to the HC during the 3 rd postural change (P=0.046). See Table 1. Conclusion: We found poorer CA to be significantly associated with worse NDO in CHD infants. These initial results demonstrate the persistence of impaired CA even after surgical repair of CHD, which may be a mechanism of brain injury. Future directions include larger studies and targeted interventions to improve CA to reduce developmental delays in CHD children.

Abstract 21278: Time to Diagnosis of Acute Coronary Obstruction Following Surgical Repair of Congenital Heart Disease is Associated With Improved Transplant-Listing Free Survival

Objectives: Acute coronary artery obstruction (CAO) following surgical repair of congenital heart disease (CHD) is rare but carries a high burden of morbidity and mortality. Prior reports describe the complication in individual populations of CHD, though few have looked at factors associated with outcomes. We hypothesize that increased time from a clinically significant post-operative sentinel event suggestive of coronary ischemia to diagnosis of CAO is associated with worse clinical outcomes. Methods: Single center retrospective review of patients diagnosed with acute post-operative CAO by coronary angiography following surgical repair of CHD between January 2000 and June 2016. Sentinel events were identified and timestamped. Characteristics compared by Fisher’s Exact and Wilcoxon Rank-Sum test. Exact logistic regression used for primary analysis. Results: A total of 34 patients were identified with acute post-operative CAO, n=32 (94%) had an identifiable sentinel event: n=15 (47%) cardiac arrest, n=12 (38%) persistent ventricular dysfunction, n=5 (16%) malignant arrhythmia. Longer sentinel event to angiography time was associated with composite outcome of death or heart transplant listing (OR 1.08 for each additional hour (1.02-1.17), p = 0.03). This association remained when adjusting for significant covariates of HLHS diagnosis (OR 1.06 (1.01-1.15) p=0.01) and surgical coronary manipulation (OR 1.07 (1.01-1.16), p=0.003). Ultimately in the series, n=27 (79%) required ECMO, n=14 (41%) died, and n=9 (27%) were listed for heart transplant. Conclusions: In the largest cohort described to date, time from a significant post-operative event to diagnosis of CAO by angiography was associated with death or heart transplant listing. Given the high burden of ECMO and death in this population, clinicians should maintain a high index of suspicion for CAO in patients who do not follow typical post-operative trajectory and consider early advanced diagnostics.

Long-Term Outcome After Ablation of Right Atrial Tachyarrhythmias After the Surgical Repair of Congenital and Acquired Heart Disease

Atrial myopathy, atriotomies, and fibrotic scars are the pathophysiological substrate of lines of conduction block, promoting atrial macroreentry. The aim of this study was to determine the acute and long-term outcome of radiofrequency catheter ablation (RFCA) for right atrial tachyarrhythmia (AT) in adults after cardiac surgery for congenital heart disease (CHD) and acquired heart disease (AHD) and predictors of these outcomes. Clinical records of adults after surgery for heart disease undergoing RFCA of right-sided AT were analyzed retrospectively. Multivariate analyses identified clinical and procedural factors predicting acute and long-term outcomes. A total of 372 patients (69% men; age 61 ± 15years) after surgical repair of CHD (n= 111) or AHD (n= 261) were studied. Cavotricuspid isthmus-dependent atrial flutter (CTI-AFL) was observed in 300 patients and non-CTI-AFL in 72 patients. Ablation was successful in 349 cases (94%). During a mean follow-up of 51 ± 30months, recurrences were observed in 24.5% of patients. Multivariate analysis showed that non-CTI-AFL (hazard ratio [HR] 1.78, 95% confidence interval [CI] 1.1 to 2.9) and CHD (HR 1.75, 95% CI 1.07 to 2.9) were independent predictors of long-term recurrences. Multivariate analysis showed that female gender (HR 2.29, 95% CI 1.6 to 3.3), surgery for AHD (HR 95% 2.31, 95% CI 1.5 to 3.7), and left atrial dilatation (HR 2.1, 95% CI 1.3 to 3.2) were independent predictors of long-term atrial fibrillation. In conclusion, RFCA of right-sided AT after cardiac surgery is associated with high acute success rates and significant long-term recurrences. Non-CTI-dependent AFL and surgery for CHD are at higher risk of recurrence. Atrial fibrillation is common during follow-up, particularly in patients with AHD and enlarged left atrium.

Catheter ablation of tachycardia arising from the pulmonary venous atrium after surgical repair of congenital heart disease.

Tachycardia arising from the pulmonary venous atrium (PVA) has not been adequately characterized in the setting of surgically repaired congenital heart disease (CHD). The purpose of this study was to determine the mechanisms, approach, and outcomes of catheter ablation of PVA tachycardia after CHD repair. The adult CHD procedural database was searched for consecutive ablation procedures over a 4-year period. Procedural characteristics of the population with tachycardia arising from the PVA were compared to those without PVA tachycardia. Groups were classified as (1) biventricular CHD, (2) single ventricle, or (3) d-transposition of the great arteries (DTGA)-baffle. Complete 3-dimensional mapping was possible for 113 of 124 sustained tachycardias during 81 procedures. Of these, 31 (19%) arose from the PVA, including 11 (15%) tachycardias in biventricular CHD, 8 (31%) in single ventricle, and 12 (80%) in DTGA-baffle procedures. Intra-atrial reentrant tachycardia was less frequently observed in the PVA vs the systemic venous atrium (SVA) (P = .012). Independent predictors of PVA tachycardia were absence of biventricular CHD (odds ratio 0.19, confidence interval 0.05-0.64, P = .010) and ipsilateral atrial surgery (odds ratio 15.7, confidence interval 4.8-59.9, P <.001). PVA procedure duration was greater than SVA-only procedures (median 5.3 hours vs 4.0 hours, P = .012), but acute success was similar (87% vs 82%, respectively, P = NS). PVA tachycardia is not unusual after surgical repair of CHD. Predictors include ipsilateral atrial surgery and absence of biventricular CHD. Such procedures involve increased complexity and unique tachycardia substrates but appear equally amenable to catheter ablation.

Abstract 69: Diminished T-Tubule Density in Newborn Human Ventricular Cells Is Associated with Heterogeneity of Calcium Transients

For children with congenital heart disease (CHD), therapies developed for adults may have different effects on immature myocardium. Thus, it is critical to understand calcium handling in the young human ventricle. Methods: Human ventricular cells were isolated from tissue removed as part of the surgical repair for CHDs from two age groups: newborns (&lt;1 week old) and infants (2-12 months old). Developmental changes in t-tubules were examined in live cells with Di-8 ANEPPS which highlights the cell membrane. We measured the T-index (percent of cell interior occupied by t-tubules), averaged for at least 3 confocal z-sections per cell. Changes in calcium transients were measured by confocal line scans in cells loaded with Fluo-4 and field stimulated (37°C). Results: Newborn human myocytes have very few t-tubules whereas infant myocytes have a range of t-tubule densities. The T-index in newborn myocytes was significantly less than in infant myocytes (4.4±0.2%, n=8 cells, 3 newborns vs. 9.1±0.9%, n=55 cells, 7 infants). Furthermore, there was sizable heterogeneity in the T-index for each patient in the infant group, in which some cells had few t-tubules and others had many t-tubules. We calculated the coefficient of variation (CV=SD/mean*100) for each patient and compared CV values for newborns vs. infants. CV was significantly greater in infants compared to newborns (46.5±7.4%, n=7, vs. 9.4±1.9%, n=3, p&lt;0.02). In addition, calcium transients from newborn cells had a ‘U’ shaped wavefront with calcium first increasing at the outer edge of the cell then propagating toward the center. In contrast, infant cells had a homogenous calcium wavefront. The delay of peak calcium from the edge to center was significantly longer in newborns compared to infants (61.7±8.9 ms, n=8 cells, 3 newborns vs. 10.6±1.6 ms, n=6 cells, 4 infants, p&lt;0.001). Conclusions: There are heterogeneous calcium transients in newborn human myocytes that correspond to a lack of t-tubules. Furthermore, t-tubule development occurs in a heterogeneous manner throughout the first year of life with cells from the same patient exhibiting different degrees of t-tubule development. This is the first study to examine t-tubule development and calcium transients in the very young human ventricular myocardium.

Postoperative Heart Block in Children with Common Forms of Congenital Heart Disease: Results from the KID Database

Cardiac conduction system injury is a cause of postoperative cardiac morbidity following repair of congenital heart disease (CHD). The national occurrence of postoperative complete heart block (CHB) following surgical repair of CHD is unknown. We sought to describe the occurrence of and costs related to postoperative CHB following surgical repair of common forms of CHD using a large national database. Retrospective, observational analysis performed over a 10-year period (2000-2009) using the Kids' Inpatient Database (KID). Visits for patients ≤24 months of age were identified who underwent surgical repair of ventricular septal defects (VSD), atrioventricular canal defects (AVC), and tetralogy of Fallot (TOF). Patients were identified who were diagnosed with postoperative CHB, further identifying those requiring a new pacemaker placement during the same hospitalization. Costs associated with visits were calculated. There were 16,105 surgical visits: 7,146 VSD, 3,480 AVC, and 5,480 TOF. There was a decrease in postoperative mortality (P = 0.0001) with no significant change in postoperative CHB. Hospital stay and cost were higher with CHB and placement of a permanent pacemaker. Repair of AVC (OR 1.77; [1.32-2.38]) was associated with a higher rate of postoperative CHB. Length of hospital stay and total cost were significantly increased with the development of postoperative CHB and increased further with placement of a permanent pacemaker. There has been little change over time in the frequency of postoperative CHB in patients undergoing repair of VSD, AVC, and TOF. Postoperative CHB results in major added cost to the healthcare system.

Impact of congenital heart disease on fetal brain development and injury

Advances in cardiac surgical techniques and intensive care have led to improved survival in babies with congenital heart disease (CHD). Although it is true that the majority of children with CHD today survive, many have impaired neurodevelopmental outcome. Although continuing to improve short-term morbidity and mortality are important goals, recent research has focused on defining the impact of CHD on brain development and brain injury in utero. The impact of CHD on the developing brain of the fetus and infant will be discussed. Neurologic abnormalities detectable prior to surgery will be described and postnatal progression of abnormalities will be highlighted. Potential causes of these findings will be discussed, including altered cerebral blood flow in utero, and brain development and risk for in-utero and postnatal brain injury. Finally, neurologic and developmental outcome after surgical repair of CHD will be reviewed. Neurodevelopmental evaluation preoperatively and postoperatively in CHD patients should be standard practice, not only to identify those with impairments who would benefit from intervention services but also to identify risk factors and strategies to optimize outcome. Fetal management and intervention strategies for specific defects may ultimately play a role in improving in-utero hemodynamics and increasing cerebral oxygen delivery to enhance brain development.

Pulmonary Complications of Congenital Heart Disease

Cardiac and pulmonary pathophysiologies are closely interdependent, which makes the management of patients with congenital heart disease (CHD) all the more complex. Pulmonary complications of CHD can be structural due to compression causing airway malacia or atelectasis of the lung. Surgical repair of CHD can also result in structural trauma to the respiratory system, e.g., chylothorax, subglottic stenosis, or diaphragmatic paralysis. Disruption of the Starling forces in the pulmonary vascular system in certain types of CHD lead to alveolar-capillary membrane damage and pulmonary oedema. This in turn results in poorly compliant lungs with a restrictive lung function pattern that can deteriorate to cause hypoxemia. The circulation post single ventricle palliative surgery (the so called "Fontan circulation") poses a unique spectrum of pulmonary pathophysiology with restrictive lung function and a low pulmonary blood flow state that predisposes to thromboembolic complications and plastic bronchitis. As the population of patients surviving post CHD repair increases, the incidence of pulmonary complications has also increased and presents a unique cohort in both the paediatric and adult clinics.

Arrhythmogenic Substrates and Catheter Ablation of Supraventricular Tachycardia after Surgical Repair of Congenital Heart Disease

Purpose: We investigated the methods of identifying and ablating the substrates of supraventricular tachycardia (SVT) after surgical repair of congenital heart disease (CHD) from the voltage map using CARTO, and to assess the effect of catheter ablation. Methods: Forty-eight patients (22 male, 22±13 years after surgery) with palpitation or symptomatic arrhythmias after surgical repair of CHD (23 TOF, 13 ASD, 6 VSD, 2 Fontan, 2 Mustard, 1 Senning, and 1 Rastelli) were studied. A high density CARTO map of RA was obtained during SVT or SR in each patient. Results: Although 32 patients had SVT previously, SVTs were provoked in 42 patients (87%). Typical AFL and AT were provoked in 12 patients. Only typical AFL was induced in 12 patients. Every AT was macro-reentrant. Thirty patients with AT had scars within low voltage area in RA free wall, which formed a channel. All SVTs were eliminated by catheter ablation in 39 patients (92%). There was no complication and only one recurrence of SVT in all patients during follow-up 34±22 months. Conclusion: Arrhythmogenic substrates of SVT can be identified by high density voltage mapping of RA with CARTO. It is clear that many patients who have any sort of atriotomy are at risk for typical AFL. The results may facilitate catheter ablation of SVT after surgical repair of CHD.

Efficacy of Radiofrequency Catheter Ablation for Intraatrial Reentrant Tachycardia with Congenital Heart Disease

Background: Intraatrial reentrant tachycardia (IART) occurs frequently in patients with congenital heart disease (CHD) and is difficult to treat. Objectives: The objective of this study was to determine the success rates of radiofrequency ablation in reducing clinical arrhythmic events in patients with IART and CHD. Results: From June 2006 to March 2011, 48 consecutive patients (24 males, age [mean ± SD] 27.3±13.4 years; total 57 sessions) with 95 circuits of IART that complicated the surgery for congenital heart disease underwent ablation. The documented events of IART after surgical repair of CHD were 14.2±9.10 years. Success for one or more IART circuits was achieved in 36 patients (75%). The mean follow-up period of these patients was 25.4±17.8 months. IART recurrence was noted after successful catheterization in 9 (25%) of 36 patients. Among these 9 patients, 6 underwent repeat ablations and 3 were readministered antiarrhythmic medications. Conclusions: In patients with successful ablation, the frequency of arrhythmic events reduced compared to that before ablation. However, recurrence of IART in patients who showed clinical improvement was frequent, and careful clinical observation was important.

Impact of Congenital Heart Disease on Brain Development and Neurodevelopmental Outcome

Advances in cardiac surgical techniques and perioperative intensive care have led to improved survival in babies with congenital heart disease (CHD). While it is true that the majority of children with CHD today will survive, many will have impaired neurodevelopmental outcome across a wide spectrum of domains. While continuing to improve short-term morbidity and mortality is an important goal, recent and ongoing research has focused on defining the impact of CHD on brain development, minimizing postnatal brain injury, and improving long-term outcomes. This paper will review the impact that CHD has on the developing brain of the fetus and infant. Neurologic abnormalities detectable prior to surgery will be described. Potential etiologies of these findings will be discussed, including altered fetal intrauterine growth, cerebral blood flow and brain development, associated congenital brain abnormalities, and risk for postnatal brain injury. Finally, reported neurodevelopmental outcomes after surgical repair of CHD will be reviewed.

Multimodality Noninvasive Imaging for Assessment of Congenital Heart Disease

Major advances in the field of pediatric cardiology and cardiac surgery over the last several decades have led to a dramatic improvement in survival rates for most forms of congenital heart disease (CHD). For example, hypoplastic left heart syndrome, a previously lethal defect, now has early survival rates up to 90% at major centers.1 These improved outcomes have produced a growing population of survivors with complex CHD who are now reaching adulthood (Figure 1). During this period, improvements in surgical and medical treatments have been accompanied by developments in diagnostic modalities. Echocardiography has replaced catheterization as the primary diagnostic modality, and it is now uncommon for newborn infants to undergo catheterization for purely diagnostic purposes. Although echocardiography remains the bedrock of noninvasive cardiac imaging, the array of diagnostic modalities and techniques available continue to grow and this has spawned the specialty of “noninvasive cardiac imaging” and the need for the “cardiac imager” to be adept in all the different modalities. Figure 1. Percentage of patients under the age of 1 year (grey bars) and over the age of 18 years (black bars) undergoing echocardiography at Children’s Hospital Boston from 1983 through 2006. Note the reverse trends of these age groups reflecting the steady increase in the proportion of adult patients with congenital heart disease. Although the absolute number of infants undergoing echocardiography during this time period has increased, their proportion has steadily declined. Echocardiography, cardiac magnetic resonance (CMR), and cardiac computed tomography (CCT) are the primary modalities used for noninvasive cardiac imaging in patients with CHD. Nuclear scintigraphy is used in selected circumstances. The Table summarizes the strengths and weaknesses of each modality. Figure 2 shows temporal trends in utilization for the various noninvasive cardiac imaging techniques at our center. It is clear that echocardiography is the most frequently …

Collateral blood flow complicating surgical repair of congenital heart disease

Objective: For neonates with congenital heart disease (CHD) echocardiography is used as diagnostic routine. However large aortopulmonary collateral arteries (APCA) cannot be visualized by echocardiography and may lead to severe complications during surgical repair of CHD. These APCA can easily be identified and occluded with pushing coils by cardiac catherization.

Ablation of focal atrial arrhythmia in patients with congenital heart defects after surgery: Role of circumscribed areas with heterogeneous conduction

In patients late after surgical repair of congenital heart disease (CHD), areas with abnormal electrophysiologic properties may serve as slow conducting pathways within a macroreentrant circuit or may be the source of focal atrial tachycardia. The purpose of this study was to evaluate the role of abnormal areas during focal atrial tachycardia prior to ablation. Electroanatomic activation mapping of 62 atrial tachycardias was performed in 43 consecutive patients (37 +/- 12 years) after surgical repair of CHD. The mechanism of atrial tachycardia was scar related intra-atrial reentry (n = 27), cavotricuspid-related atrial flutter (n = 21), atrial fibrillation (n = 2), or focal atrial tachycardia (n = 10). During intra-atrial reentry, channels of slow conduction could be identified in all patients. Subsequent ablation was directed toward connecting two nonconductive borders. The site of origin during focal atrial tachycardia showed fractionated potentials and/or continuous electrical activity. Ablation directed at isolating the source area resulted in termination of focal atrial tachycardia in all cases. In two patients, ablation of an area showing continuous electrical activity giving rise to fibrillatory conduction resulted in termination of atrial fibrillation. Ablation of intra-atrial reentry was successful in 70%. Atrial flutter and focal atrial tachycardia were successfully ablated in all patients. No complications were observed. In patients with surgically corrected CHD, atrial tachycardia most often is caused by a macroreentrant mechanism but in some is the result of a focal mechanism. Areas of abnormal conduction may serve not only as a zone of slow conduction within a macroreentrant circuit but also as the site of origin of a focal atrial arrhythmia. Catheter ablation directed at "source isolation" is effective in eliminating focal atrial tachycardia in patients with CHD.

Quantification of flow dynamics in congenital heart disease: applications of velocity-encoded cine MR imaging.

Velocity-encoded cine (VEC) magnetic resonance (MR) imaging is a valuable technique for quantitative assessment of flow dynamics in congenital heart disease (CHD). VEC MR imaging has a variety of clinical applications, including the measurement of collateral flow and pressure gradients in coarctation of the aorta, differentiation of blood flow in the left and right pulmonary arteries, quantification of shunts, and evaluation of valvular regurgitation and stenosis. After surgical repair of CHD, VEC MR imaging can be used to monitor conduit blood flow, stenosis, and flow dynamics. There are some pitfalls that can occur in VEC MR imaging. These include potential underestimation of velocity and flow, aliasing, inadequate depiction of very small vessels, and possible errors in pressure gradient measurements. Nevertheless, VEC MR imaging is a valuable tool for preoperative planning and postoperative monitoring in patients with CHD.

Characterization of reentrant circuit in macroreentrant right atrial tachycardia after surgical repair of congenital heart disease: isolated channels between scars allow "focal" ablation.

The purpose of this study was to characterize the circuit of macroreentrant right atrial tachycardia (MacroAT) in patients after surgical repair of congenital heart disease (SR-CHD). Sixteen patients with atrial tachycardia (AT) after SR-CHD were studied (atrial septal defect in 6, tetralogy of Fallot in 4, and Fontan procedure in 6). Electroanatomic right atrial maps were obtained during 15 MacroATs in 13 patients, focal AT in 1 patient, and atrial pacing in 2 patients without stable AT. A large area of low bipolar voltage (</=0.5 mV) involved most of the free wall in all patients and contained 2 to 7 dense scars or lines of double potentials, forming 29 narrow channels (width </=2.7 cm) between scars in all but 1 patient, who had a single scar and only focal AT. All 15 MacroATs were propagated through narrow channels. Ablation within the channel eliminated all 15 MacroATs with 1 to 3 (median 1) radiofrequency applications. Ablation was performed in 9 other channels identified during MacroAT (5 patients) and in 5 channels identified during atrial pacing (2 patients). Conduction block was obtained across 28 of 29 channels. After ablation, reproducible sustained right AT was not induced in any patient. During follow-up (median 13.5 months), new MacroATs, atrial fibrillation, or palpitations occurred in 3 of 16 patients. MacroAT after SR-CHD requires a large area of low voltage containing >/=2 scars forming narrow channels. Ablation within the channels eliminates MacroAT.