Christopher L. Johnsrude

Fontan Conversion To Cavopulmonary Connection And Arrhythmia Circuit Cryoablation

OBJECTIVES We review our surgical experience patients with atriopulmonary Fontan operations who had obstructive or arrhythmia indications for conversion to total cavopulmonary artery connections, arrhythmia circuit cryoablation, and placement of atrial antitachycardia pacemaker. METHODS Fourteen patients (mean age 14 +/- 4 years) had conversion to total cavopulmonary artery connection 8 +/- 3 years after the original atriopulmonary Fontan operation primarily for atrial arrhythmias in 11, obstructive lesions in 2, and bradycardia with cyanosis in 1. Arrhythmia circuit cryoablation was performed on 11 patients and 10 had atrial antitachycardia pacemakers. Preoperative functional New York Heart Association class was IV in 9, III in 4, and II in 1. RESULTS One patient had brain death (7%) presumably caused by resternotomy complications despite an excellent hemodynamic result. Another required reoperation for a maldeployed clamshell device after attempted fenestration closure. Average length of stay was 10 +/- 3 days; chest tubes were removed on day 7 +/- 3. There were no long-term deaths (mean follow-up 1.7 years, range 5 months to 5 years). Postoperative arrhythmias occurred in five patients, three of whom had successful termination by antitachycardia pacemaker and two who had pharmacologic control of their respective junctional ectopic and slow atrial tachycardia. All patients have improved to New York Heart Association class I or II. CONCLUSIONS Total cavopulmonary artery conversion in association with arrhythmia circuit cryoablation and atrial antitachycardia pacemaker placement can be accomplished with low morbidity and mortality, oftentimes resulting in dramatic increases in functional class and control of life-threatening arrhythmias.

Impact of arrhythmia circuit cryoablation during Fontan conversion for refractory atrial tachycardia

Refractory atrial arrhythmias in late postoperative Fontan patients are usually associated with residual hemodynamic abnormalities and result in significant morbidity and mortality. Surgical revision of the Fontan anastomosis may improve hemodynamics without eliminating tachycardia. This study sought to assess the impact of surgical cryoablation of the arrhythmia circuit at the time of Fontan conversion on the clinical recurrence of tachycardia. Sixteen consecutive atriopulmonary Fontan patients with refractory atrial arrhythmias underwent surgical conversion to lateral tunnel total cavopulmonary anastomosis (15) or Fontan revision (1 patient). The initial 4 patients underwent Fontan conversions alone, without specific arrhythmia surgery. The subsequent 12 patients underwent electrophysiologically guided cryoablation of the tachycardia circuits at the time of surgical conversion. The mean age at Fontan revision was 15.6 +/- 3.8 years. Cryoablation was directed to 3 identified major tachycardia circuits: the inferomedial right atrium, the superior rim of the prior atrial septal defect patch, and along the lateral right atrial wall. Transmural antitachycardia pacemakers were implanted in 11 of the 16 patients. There was no surgical mortality in either group, and all patients improved in functional classification. All patients not undergoing cryoablation experienced recurrent symptomatic tachycardia requiring antiarrhythmic therapy (median follow-up, 54 months) versus 2 of 12 patients receiving cryoablation (median follow-up, 25 months; p <0.02). Thus, surgical cryoablation of the arrhythmia circuit at the time of Fontan conversion is highly effective in the management of refractory atrial arrhythmias, and is superior to Fontan conversion alone.

Catecholaminergic Polymorphic Ventricular Tachycardia in Children Analysis of Therapeutic Strategies and Outcomes From an International Multicenter Registry

Background—Catecholaminergic polymorphic ventricular tachycardia is an uncommon, potentially lethal, ion channelopathy. Standard therapies have high failure rates and little is known about treatment in children. Newer options such as flecainide and left cardiac sympathetic denervation are not well validated. We sought to define treatment outcomes in children with catecholaminergic polymorphic ventricular tachycardia. Methods and Results—This is a Pediatric and Congenital Electrophysiology Society multicenter, retrospective cohort study of catecholaminergic polymorphic ventricular tachycardia patients diagnosed before 19 years of age. The cohort included 226 patients, including 170 probands and 56 relatives. Symptomatic presentation was reported in 176 (78%). Symptom onset occurred at 10.8 (interquartile range, 6.8–13.2) years with a delay to diagnosis of 0.5 (0–2.6) years. Syncope (P<0.001), cardiac arrest (P<0.001), and treatment failure (P=0.008) occurred more often in probands. &bgr;-Blockers were prescribed in 205 of 211 patients (97%) on medication, and 25% experienced at least 1 treatment failure event. Implantable cardioverter defibrillators were placed in 121 (54%) and was associated with electrical storm in 22 (18%). Flecainide was used in 24% and left cardiac sympathetic denervation in 8%. Six deaths (3%) occurred during a cumulative follow-up of 788 patient-years. Conclusions—This study demonstrates a malignant phenotype and lengthy delay to diagnosis in catecholaminergic polymorphic ventricular tachycardia. Probands were typically severely affected. &bgr;-Blockers were almost universally initiated; however, treatment failure, noncompliance and subtherapeutic dosing were often reported. Implantable cardioverter defibrillators were common despite numerous device-related complications. Treatment failure was rare in the quarter of patients on flecainide. Left cardiac sympathetic denervation was not uncommon although the indication was variable.

Comparison of Anatomic Isthmus Block With the Modified Right Atrial Maze Procedure for Late Atrial Tachycardia in Fontan Patients

Background—Late atrial reentry tachycardia (AT) after Fontan repair is common, with limited efficacy of medical therapy in preventing AT recurrence. In this study, two approaches to surgical arrhythmia ablation in patients with refractory AT undergoing Fontan revision are compared: cryoablation of the inferomedial right atrium (RA), and a more extensive modified RA maze procedure designed to eliminate all potential RA reentrant circuits. Methods and Results—Fontan revision was performed in 23 patients with AT, using inferomedial RA cryoablation (Group 1, n=8) and modified RA maze procedure (Group 2, n=15). There was no difference in age at initial Fontan, age at Fontan revision, age at onset of AT, or number of failed antiarrhythmic medications. Patients underwent preoperative, intraoperative, and postoperative electrophysiological studies. Thirty-eight different tachycardia circuits were induced in preoperative studies with 3 major areas of RA involvement: the lower lateral RA, the atrial septum, and the inferomedial RA. At postoperative electrophysiological study, AT was inducible in 62% of Group 1 patients but only 7% of Group 2 patients (P <0.02). With mean follow-up of 43 months, 5 of 8 patients in Group 1 experienced AT recurrence compared with none in Group 2 (P <0.001). There was no significant difference in length of hospital stay or complication rate comparing the two groups. Conclusion—Modified RA maze procedure is superior to anatomic isthmus block in treating reentrant AT in postoperative Fontan patients. The modified RA maze has eliminated AT recurrence at mid-term follow-up with low morbidity and mortality.

Current Approach to Pediatric Syncope

Abstract. Syncope is the abrupt loss of consciousness and postural tone that reverses without intervention. Typically, syncopal episodes in pediatric patients are brief, lasting seconds (rarely minutes), and are followed by complete recovery without residual neurological sequelae. Syncopal presentations may be dramatic and lead family members and primary care providers to suspect a malignant cardiac condition, prompting referral to a pediatric cardiologist. Significant advances in the understanding of syncope in infants, children, and adolescents have occurred in the past decade. This review emphasizes neurally mediated syncope, but other etiologies are reviewed to complete the spectrum encountered by pediatric cardiologists. Some clues are provided to distinguish the more common and benign forms of syncope from those due to significant underlying heart disease.

A Comparison of Steroid‐Eluting Epicardial versus Transvenous Pacing Leads in Children

Abstract Objective: To evaluate the acute and chronic performance of steroid‐eluting (SE) epicardial (EPI) pacing leads as compared to SE transvenous (TV) pacing leads in children. Methods: From 1989 through 1997, 55 children with congenital heart disease received a total of 85 SE pacing leads, of which 38 were EPI and 47 TV. The mean age of children receiving EPI leads was younger than those receiving TV leads (7.7 months vs 15.1 years, p = 0.001), and they had shorter follow‐up (17.2 months vs 36.2 months, p < 0.001). All leads were evaluated for acute and chronic sensing and capture thresholds, and impedance. Results: Acute and in particular chronic atrial and ventricular sensing and capture thresholds in SE EPI and TV leads were essentially equivalent.

New Directions in Surgical Therapy of Arrhythmias

Abstract. The success of the radiofrequency catheter ablation procedure for most types of supraventricular and ventricular tachycardia, particularly in young patients, largely eliminated the role of surgical therapy of arrhythmias. However, there remains a subset of arrhythmia patients in whom the catheter approach has not been successful and types of arrhythmias with high recurrence rates following initially successful catheter ablation procedures where surgery can provide more definitive therapy. In addition, the concepts of ablation therapy can be successfully incorporated into the concomitant repair of complex congenital heart disease, resulting in single-stage therapy for structural and rhythm abnormalities. Prospectively, knowledge of the role of anatomic barriers as substrates for future reentrant arrhythmia circuits provides the opportunity to alter these circuits prophylactically at the time of initial surgical repair of congenital heart disease in an attempt to avoid the late development of tachycardia. This article describes our experience during the past decade with 71 patients undergoing arrhythmia surgery using this approach.

The clinical and genetic spectrum of catecholaminergic polymorphic ventricular tachycardia: findings from an international multicentre registry

Aims Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an ion channelopathy characterized by ventricular arrhythmia during exertion or stress. Mutations in RYR2-coded Ryanodine Receptor-2 (RyR2) and CASQ2-coded Calsequestrin-2 (CASQ2) genes underlie CPVT1 and CPVT2, respectively. However, prognostic markers are scarce. We sought to better characterize the phenotypic and genotypic spectrum of CPVT, and utilize molecular modelling to help account for clinical phenotypes. Methods and results This is a Pediatric and Congenital Electrophysiology Society multicentre, retrospective cohort study of CPVT patients diagnosed at <19 years of age and their first-degree relatives. Genetic testing was undertaken in 194 of 236 subjects (82%) during 3.5 (1.4-5.3) years of follow-up. The majority (60%) had RyR2-associated CPVT1. Variant locations were predicted based on a 3D structural model of RyR2. Specific residues appear to have key structural importance, supported by an association between cardiac arrest and mutations in the intersubunit interface of the N-terminus, and the S4-S5 linker and helices S5 and S6 of the RyR2 C-terminus. In approximately one quarter of symptomatic patients, cardiac events were precipitated by only normal wakeful activities. Conclusion This large, multicentre study identifies contemporary challenges related to the diagnosis and prognostication of CPVT patients. Structural modelling of RyR2 can improve our understanding severe CPVT phenotypes. Wakeful rest, rather than exertion, often precipitated life-threatening cardiac events.

Magnetocardiography-Guided Management of an Unusual Case of Isoimmune Complete Atrioventricular Block Complicated by Ventricular Tachycardia

A fetus who was diagnosed at 25 weeks of gestation with isoimmune AV block presented at 34 weeks with a precipitous fall in ventricular rate and periods of tachycardia. Magnetocardiography revealed the tachycardia to be ventricular. After delivery, nonsustained ventricular tachycardia continued. The baby then successfully paced, and at higher ventricular rates the tachycardia resolved. Five years later the child has normal ventricular function and is doing well.

Atrioventricular Nodal Reentrant Tachycardia in Patients With Congenital Heart Disease: Outcome After Catheter Ablation

Background— The relationship of atrioventricular nodal reentrant tachycardia to congenital heart disease (CHD) and the outcome of catheter ablation in this population have not been studied adequately. Methods and Results— A multicenter retrospective study was performed on patients with CHD who had atrioventricular nodal reentrant tachycardia and were treated with catheter ablation. There were 109 patients (61 women), aged 22.1±13.4 years. The majority, 86 of 109 (79%), had CHD resulting in right heart pressure or volume overload. Patients were divided into 2 groups: group A (n=51) with complex CHD and group B (n=58) with simple CHD. There were no significant differences between groups in patients’ growth parameters, use of 3-dimensional imaging, and type of ablation (radiofrequency versus cryoablation). Procedure times (251±117 versus 174±94 minutes; P=0.0006) and fluoroscopy times (median 20.8 versus 16.6 minutes; P=0.037) were longer in group A versus group B. There were significant differences between groups in the acute success of ablation (82% versus 97%; P=0.04), risk of atrioventricular block (14 versus 0%; P=0.004), and need for chronic pacing (10% versus 0%; P=0.008). There was no permanent atrioventricular block in patients who underwent cryoablation. After 3.2±2.7 years of follow-up, long-term success was 86% in group A and 100% in group B (P=0.004). Conclusions— Atrioventricular nodal reentrant tachycardia can complicate the course of patients with CHD. This study demonstrates that the outcome of catheter ablation is favorable in patients with simple CHD. Patients with complex CHD have increased risk of procedural failure and atrioventricular block.