Acute outcomes of three-dimensional mapping for fluoroscopy reduction in paediatric catheter ablation for supraventricular tachycardia.

BACKGROUND: Catheter ablation is a safe and effective therapy for the treatment of supraventricular tachycardia in children. Current improvements in technology have allowed progressive reduction in radiation exposure associated with the procedure. To assess the impact of three-dimensional mapping, we compared acute procedural results collected from the Catheter Ablation with Reduction or Elimination of Fluoroscopy registry to published results from the Prospective Assessment after Pediatric Cardiac Ablation study. METHODS: Inclusion and exclusion criteria from the Prospective Assessment after Pediatric Cardiac Ablation study were used as guidelines to select patient data from the Catheter Ablation with Reduction or Elimination of Fluoroscopy registry to compare acute procedural outcomes between cohorts. Outcomes assessed include procedural and fluoroscopy exposure times, success rates of procedure, and complications. RESULTS: In 786 ablation procedures, targeting 498 accessory pathways and 288 atrioventricular nodal reentrant tachycardia substrates, average procedural time (156.5 versus 206.7 minutes, p < 0.01), and fluoroscopy time (1.2 versus 38.3 minutes, p < 0.01) were significantly shorter in the study group. Success rates for the various substrates were similar except for manifest accessory pathways which had a significantly higher success rate in the study group (96.4% versus 93.0%, p < 0.01). Major complication rates were significantly lower in the study group (0.3% versus 1.6%, p < 0.01). CONCLUSIONS: In a large, multicentre study, three-dimensional systems show favourable improvements in clinical outcomes in children undergoing catheter ablation of supraventricular tachycardia compared to the traditional fluoroscopic approach. Further improvements are anticipated as technology advances.

Bubble bilevel ventilation facilitates gas exchange in anesthetized rabbits.

BACKGROUND: Bubble continuous positive airway pressure is an established therapy for infants in respiratory distress. In resource-limited settings, few treatment options exist for infants requiring further respiratory support. A bubble bilevel device has been developed to provide nonelectric, time-cycled, pressure-limited respiratory support. We compared the efficacy of bubble bilevel ventilation with conventional mechanical ventilation in sedated rabbits. METHODS: Six adult rabbits under inhaled isoflurane general anesthesia were ventilated by alternating intervals of conventional and bubble bilevel ventilation for three 10-15-min periods. During each period, interval arterial blood gas (ABG) measurements were obtained after at least 10 min on the respective mode of ventilation. RESULTS: The bubble bilevel system was able to deliver the following pressures: 20/7, 15/5, 12/5, 8/5 cm H2O. The estimated differences in arterial blood gas values on bubble bilevel vs. ventilator were as follows (normalized values): pH 7.41 vs. 7.40, pCO2 37.7 vs. 40, pO2 97.6 vs. 80. In addition, the bubble bilevel ventilation delivered consistent pressure waveforms without interruption for over 60 min on two rabbits. CONCLUSION: This study demonstrates promising in vivo results on the efficacy of a novel bubble bilevel device, which may prove useful for infants in respiratory distress. IMPACT: Given the lack of personnel, funds or infrastructure to provide neonatal mechanical ventilation in resource-limited settings, additional low-cost, low-tech treatments are necessary to save infant lives. Bubble bilevel ventilation reliably delivers two levels of airway pressure to anesthetized rabbits resulting in normalization of blood gases comparable to those achieved on a traditional ventilator. If proven effective, simple technologies like this device have the potential to significantly impact neonatal mortality due to respiratory distress globally.

Frequency of CIED remote monitoring: A quality improvement follow-up study.

BACKGROUND: Based on the findings of a prior study of CIED (Cardiac Implantable Electrical Device) remote monitoring (RM) frequency at the same center, the University of Michigan Congenital Heart Center (UMCHC) instituted a quality improvement (QI) change to reduce the frequency of routine CIED RM from every 2 months to every 3 months. The objective of this study is to determine the impact of this QI initiative to reduce workload without compromising patient care. METHODS: This is a single-center, retrospective cohort study of all UMCHC patients with CIEDs followed via Medtronic CareLink CIED remote monitoring system from July 2015 to June 2017, after the QI change in 2014. The primary outcome was success of transition to new monitoring schedule. Secondary outcomes included complications, incidence of actionable events (AES), patient compliance, and change in workload. Outcomes were compared to the prior study. RESULTS: There were 325 patients (mean age was 24  ±  14 years) included, of who 293 (90%) completely transitioned to the new RM schedule. During the study period, 96 transmissions included AES (4% of total), of which 50 (52%) were asymptomatic and discovered on routine monitoring. No patient experienced a complication attributable to decreased RM frequency. The mean number of interrogations decreased by 1.6 per patient over the 2-year period compared to prior study. CONCLUSIONS: This study demonstrated successful implementation of a QI initiative to reduce CIED monitoring frequency at a single center with no patient adverse events. The intervention reduced workload and potentially improved patient compliance with routine RM.

Variation in Pediatric Post-Ablation Care: A Survey of the Pediatric and Congenital Electrophysiology Society (PACES).

Although catheter ablation is a standard treatment for pediatric arrhythmias, there are no consensus guidelines for follow-up care. This study describes the variation in post-ablation practices identified through a survey of the pediatric and congenital electrophysiology society (PACES). Pediatric and congenital electrophysiology society members were invited to participate in an online survey of post-ablation practices in September 2014. Survey questions targeted routine post-ablation practices for three common arrhythmia substrates: atrioventricular nodal reentry tachycardia, concealed accessory pathways (AP), and manifest APs. Significant practice variation was defined as <90% concordance among respondents. There were 70 respondents from 67 centers, 29 (41%) in practice for <10 years. Uniform practices included aspirin after left side ablation by 65 (93%), immediate post-procedure ECG by 63 (90%), and performance of outpatient follow-up in 69 (99%) including ECG in 97-100% depending on substrate. The majority, 57 (81%), have standardized follow-up independent of substrate. Post-procedural observation is highly variable, with 25 (36%) discharging patients on the day of ablation, 22 (33%) observing patients in hospital overnight, and 21 (30%) basing hospitalization on pre-defined criteria. Immediate post-procedure echo is performed after all ablations in only 16 (23%). Discharge from outpatient care occurs at a median time of 12 months for each arrhythmia substrate. Common post-ablation practices are evident among pediatric electrophysiologists. However, they report significant variation in post-procedure monitoring practices and testing. The rationale for these variances, and their impact on costs and outcomes, should be defined.

Follow-Up of a Prospective Surgical Strategy to Prevent Intra-Atrial Reentrant Tachycardia After the Fontan Operation.

BACKGROUND: Intra-atrial reentrant tachycardia (IART) after the Fontan operation had an early reported incidence of 10% to 35% during early and intermediate follow-up and posed substantial management challenges. METHODS AND RESULTS: To reduce the incidence of IART after the Fontan procedure, we performed a randomized, double-blind study to evaluate the impact of an incision in the right atrium joining the lateral tunnel suture line and the tricuspid valve annulus. Between March 1998 and September 2003, 134 subjects (median age: 1.8 years; range: 1.3-5.2 years; 91 men) were randomly assigned to receive the incision. All 134 patients had a form of single ventricle pathological anatomy. The clinical course, electrocardiograms, and Holter monitoring were available for review in 114 subjects at a median of 8.2-year follow-up (range: 0.9-11.9 years). There were 2 late deaths, neither subject had IART. The combined incidence of sustained IART was 3.5% (4/114). There was no difference in the occurrence of sustained IART between those subjects receiving the incision and those who did not (2 in each group) during follow-up. No patients of either group experienced short-term complications. CONCLUSIONS: Despite the fact that the primary outcome of this trial was not reached, the most significant finding was that with current management, the incidence of IART is considerably lower than the early retrospective, observational studies suggested.

Patient and Procedural Correlates of Fluoroscopy Use During Catheter Ablation in the Pediatric and Congenital Electrophysiology Lab.

OBJECTIVE: To identify factors associated with fluoroscopy use in pediatric and congenital heart disease (CHD) patients. DESIGN: Retrospective cohort. SETTING: Pediatric electrophysiology lab in a single tertiary-care children's hospital. PATIENTS: Three hundred eighty-three patients who underwent electrophysiology study and ablation between January 2010 and December 2012. METHODS: Ablation procedures in which nonfluoroscopic navigation was employed were reviewed. Procedures using ≥ 10 minutes of fluoroscopy (high-fluoroscopy time; HF) were compared with those using <10 minutes (low-fluoroscopy time; LF). Group comparison of characteristics was made in the entire cohort and in CHD and anatomically normal heart subsets. RESULTS: During the study period, 416 ablation procedures were performed involving 471 substrates in 383 patients. Median fluoroscopy time was 6.7 minutes overall and 5.1 minutes with anatomically normal hearts. LF comprised 61% of all ablation and 69% of anatomically normal hearts. LF procedures were associated with anatomically normal hearts (93% vs. 63%; P < .0001). In anatomically normal hearts, HF was associated with accessory pathways (64% vs. 47%; P = .01), posteroseptal substrates (22% vs. 9%; P = .002), and ventricular substrates (12% vs. 1%; P < .0001). All cases of intra-atrial reentrant tachycardia were HF. HF was associated with trans-septal puncture (47% vs. 23%; P < .0001) though not when controlling for atrioventricular nodal reentrant tachycardia. LF was associated with cryoablation (56% vs. 17%; P < .0001). CONCLUSIONS: In pediatric and congenital EP, ablation procedures using cryoablation and in patients with anatomically normal hearts are associated with LF. In accessory pathway ablation, HF was not associated with trans-septal puncture.

Cardiac implantable electronic device remote monitoring surveillance in pediatric and congenital heart disease: Utility relative to frequency.

BACKGROUND: Heart Rhythm Society expert consensus provides recommendations for surveillance monitoring of cardiac implantable electronic devices (CIEDs), but limited data are available for the pediatric and congenital heart disease population. OBJECTIVE: The purpose of this study was to determine the rate of actionable events during CIED surveillance in this population, assess the utility of routine CIED remote monitoring, and assess the potential benefit from more frequent monitoring. METHODS: This was a retrospective cohort study of all CIED patients followed at a pediatric and congenital heart center and enrolled in the Medtronic Carelink system with either (1) a chronic (implanted for >6 months) CIED followed between July 1, 2010, and July 1, 2012, on a bimonthly schedule; or (2) a new CIED (implanted <6 months) between July 1, 2008, and July 1, 2012, followed on a monthly schedule. RESULTS: Aggregate mean age was 20 ± 13.7 years. There were 608 interrogations on newly implanted CIEDs with an actionable event rate of 11 per 100 patient-years. There were 2614 interrogations of chronic CIEDs with an actionable event rate of 22 per 100 patient-years. The odds of an actionable event on an asymptomatic remote monitoring transmission was lower than if symptomatic (odds ratio 0.04, 95% confidence interval 0.03-0.07). Tachyarrhythmia was the most common event. Predictors of actionable events were identified. CONCLUSION: In this population of pediatric and congenital heart disease patients, the rate of actionable events was low, especially on asymptomatic interrogations. Most actionable events were due to tachyarrhythmia. A more frequent than every 90-day monitoring schedule does not appear to be of significant benefit.

Antitachycardia pacemakers in congenital heart disease.

BACKGROUND: Many patients with congenital heart disease (CHD) acquire rhythm abnormalities related to their repair, most commonly intraatrial reentrant tachycardia (IART). Treatment of IART in CHD is often multifaceted, and may include medication, ablation, and pacing. Evidence regarding the use of antitachycardia pacing therapies is limited. OBJECTIVE: The aim of the study is to define the use and efficacy of antitachycardia pacing in patients with CHD at a single center. RESULTS: Eighty implants were performed on 72 patients between 2000 and 2010. Follow-up data of more than 3 months were available for 56 patients; median follow-up time was 2.8 years. Twenty (36%) patients received successful antitachycardia pacing at a median 1.3 years postimplant. For those patients with IART after implant, antitachycardia pacing was successful in 57%. Patients with two-ventricle repairs were more likely to have successful antitachycardia pacing than those with one-ventricle palliation (45% vs. 17%, P = .04). Patients with documented IART had more successful antitachycardia pacing than those with no documented atrial tachycardia prior to implant (46% vs. 7%, P = .006). Early complications of antitachycardia pacemaker implant occurred in six patients (11%); late complications after implant occurred in three patients (5.6%). Of the initial 72 patients implanted, there were six deaths (8%). CONCLUSIONS: Antitachycardia pacing therapies were successful in the majority of CHD patients who had IART after implant. Patients without documented atrial tachycardia prior to implant were unlikely to require or receive successful therapy from antitachycardia pacemaker. Those patients postatrial switch procedure who had documented IART prior to implant had the highest incidence of successful antitachycardia pacing therapies. Antitachycardia pacemaker implantation is an adjunct to the management of IART in CHD patients, but may not benefit patients who have not yet demonstrated IART.

Transseptal access in pediatric and congenital electrophysiology procedures: defining risk.

PURPOSE: Transseptal puncture (TSP) is commonly used to access the left heart for catheter ablation procedures. The specific complication risk of this procedure has not been determined. This study assesses the risk of TSP using a single standard technique during electrophysiology study (EPS) in pediatrics and congenital heart disease (CHD). METHODS: Retrospective cohort study of patients undergoing TSP during EPS at the University of Michigan Congenital Heart Center between 1999 and 2011. RESULTS: There were 373 left heart ablation procedures during the study period. Excluded were six adults without CHD, five procedures using an alternative imaging modality, five procedures using retrograde aortic access, one transhepatic access, and one where TSP was performed during a prior procedure. Included were 321 pediatric (≤18 years old without CHD) TSP procedures (median age 13 years) and 34 TSP procedures in patients with CHD (median age 28 years). There was one complication directly attributable to TSP: needle perforation of the left atrium without development of effusion in the pediatric group. Post-procedure echocardiograms were performed in 351 (99 %) cases, showing only trivial effusions in seven (1.9 %). CONCLUSIONS: This single center experience over 12 years shows the risk of TSP in pediatric and CHD patients to be low, with a 0.3 % (95 % confidence interval (CI) 0, 0.9 %) risk for complications directly related to TSP using only single plane fluoroscopy for visualization.

Research accomplishments in pediatric electrophysiology: a historical review.

Arrhythmia management in young patients plays a small but important role within the broader discipline of cardiac electrophysiology (EP). By virtue of its sharp focus on developmental cardiology, congenital heart defects, and hereditary channelopathies, pediatric EP has contributed in significant ways to improved understanding of rhythm disorders in patients of all ages. Scientific progress in the field was recently reviewed at the 2012 meeting of the Heart Rhythm Society, where historical details of pioneering investigations in pediatric EP were highlighted. In this article, we hope to summarize those details and acknowledge the roles of individuals and organizations that were instrumental in developing the subspecialty.

Arrhythmogenic channelopathy syndromes presenting as refractory epilepsy.

BACKGROUND: Children and young adults with potentially lethal cardiac channelopathies often present to medical care with a history of syncope or seizures due to episodic ventricular arrhythmias and associated cerebral hypoperfusion. METHODS: Two important types of genetic arrhythmia syndromes-long QT syndrome and catecholaminergic polymorphic ventricular tachycardia-are discussed using relevant case examples. The pathophysiology and distinguishing clinical features of these conditions are reviewed. RESULTS: The patients in each case were ultimately diagnosed with a cardiac channelopathy as the cause for their syncope and refractory seizures. With appropriate medical management, no further events have occurred to date. CONCLUSIONS: Cardiac channelopathies can be misdiagnosed as refractory epilepsy when in fact these events represent convulsive syncopes. Knowledge of and suspicion for these arrhythmogenic conditions may expedite diagnosis and improve outcomes.

Verapamil in infants: an exaggerated fear?

The use of intravenous verapamil for tachyarrhythmia in infants is widely considered contraindicated due to the perceived risk of hemodynamic collapse after administration. This article reviews the relatively limited evidence that led to this well-known contraindication and highlights the interesting process by which medical practice may evolve in the absence of persuasive science.

Utility of intrathoracic impedance monitoring in pediatric and congenital heart disease.

BACKGROUND: The utility of cardiac device-based intrathoracic monitoring (OptiVol, Medtronic Inc., Minneapolis, MN, USA) for congestive heart failure (CHF) exacerbation has not been evaluated in pediatric or congenital heart disease patients. METHODS: This was a retrospective study of all patients at a single center with an endocardial OptiVol capable device. OptiVol index values were collected in 2-week bins from January 2007 to December 2010. The clinical outcomes were CHF exacerbation defined as hospitalization or medication change for CHF and device-treated ventricular arrhythmia based on remote or in-office device interrogation. Clinical and OptiVol data were collected by separate investigators blinded to the other parameter. OptiVol data were correlated to the clinical outcomes to determine sensitivity and predictability for multiple threshold values in the entire cohort and pediatric and congenital subgroups. RESULTS: Forty-seven patients were included. A total of 1,106 months of OptiVol data were collected. Median age of the cohort was 18 years (range 6-58 years). There were 23 pediatric, median age 13 years (range 6-16), at device implant, and 18 patients, median age 31 years (range 13-58), considered at risk for heart failure at implant. There were three heart failure exacerbations and 17 treated ventricular arrhythmias. The study population-specific positive predictive value (PPV) of OptiVol was low (sensitivity 33% and PPV ≤4.4%) for both CHF exacerbation and arrhythmias in all analyzed groups. CONCLUSIONS: The sensitivity and positive predictive value of intrathoracic impedance monitoring was low in this population of adult congenital and pediatric patients. Recent improvements to the OptiVol algorithm may decrease these deficiencies.

Implanted defibrillators in young hypertrophic cardiomyopathy patients: a multicenter study.

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiovascular disease, with an annual risk of sudden cardiac death (SCD) estimated at 1 %. Limited data are available regarding both the risk of SCD in the young HCM population and the use of implantable cardioverter-defibrillators (ICDs). This retrospective study included all patients with HCM who underwent ICD implantation for primary or secondary prevention of SCD before the age of 30 years at five institutions between 1995 and 2009. There were 99 devices implanted in 73 patients. Appropriate shocks occurred for 11 % of all the patients. None of the previously identified conventional risk factors for SCD in HCM patients were associated with increased risk of appropriate shocks in the young study cohort. During a median follow-up period of 2.4 years, inappropriate shocks occurred for 22 % of the patients. Older age at implant was associated with a decreased risk of inappropriate shock. Those who underwent implantation in the earlier decade had a higher incidence of inappropriate shocks. Late complications including lead fracture or dislodgement, generator malfunction, and infection occurred for 32 % of the patients. Three patients died (4 %), one of whom had an arrhythmic sudden death. A greater proportion of primary prevention implantations was performed for patients from the latter decade. Over time, ICD use in young HCM patients has become increasingly primary prevention oriented. Shock rates mirror those reported in adult series, and there is a substantial incidence of device complications.

Pattern of recovery for transient complete heart block after open heart surgery for congenital heart disease: duration alone predicts risk of late complete heart block.

Transient complete heart block (TCHB) is defined as complete interruption of atrioventricular conduction (AVC) after cardiac surgery followed by return of conduction. This study aimed to assess the risk for the development of late complete heart block (LCHB) after recovery of TCHB and to examine the electrocardiographic and electrophysiologic properties of the AVC system after TCHB. Of the 44 patients in this study who experienced TCHB, 37 recovered completely. Seven patients progressed from TCHB to intermittent CHB or LCHB requiring pacemaker implantation. Preoperative, early postoperative, and late postoperative electrocardiograms as well as postoperative atrial stimulation were obtained. The results showed that the median duration of TCHB was 5 days in the TCHB group compared with 9 days in the LCHB group (p = 0.01). All 37 subjects with TCHB recovered AVC within 12 days, but only two with LCHB did so (p = 0.02). The risk of LCHB for the patients with 7 days of postoperative TCHB or longer was 13 times greater than for the patients with fewer than 7 days of TCHB (p = 0.01). The median late postoperative PR interval was slightly but significantly longer in the LCHB group than in the TCHB group (p = 0.02). In contrast, the electrophysiologic properties between the two groups did not differ significantly. From those findings, we concluded that delayed recovery of AVC after surgical TCHB (≥7 days), but not electrophysiologic properties of recovered AVC assessed early in the postoperative period strongly, predicts risk of LCHB. Follow-up evaluation of AVC is particularly indicated for the delayed recovery group.

Novel ryanodine receptor 2 mutation associated with a severe phenotype of catecholaminergic polymorphic ventricular tachycardia.

An adolescent girl with a history of anxiety associated seizure-like episodes was ultimately diagnosed with catecholaminergic polymorphic ventricular tachycardia. She tested positive for a novel mutation of the ryanodine receptor. The report underscores how genetic arrhythmia syndromes may be mistaken for neurologic disorders.

Cryoablation therapy for atrioventricular nodal reentrant tachycardia in children: a multicenter experience of efficacy.

Atrioventricular nodal reentrant tachycardia (AVNRT), a common tachycardia in children, is routinely treated by catheter ablation using radiofrequency or cryothermal energy. Acute success rates of 95-97 % are reported for cryoablation, similar to those achieved with radiofrequency ablation (RFA). However, early studies reported higher recurrence rates after cryoablation for treatment of AVNRT than those reported for RFA. This study evaluated the success and recurrence rates for cryoablation in a current cohort of pediatric patients across several institutions. Patients 21 years old or younger with AVNRT who underwent cryoablation at five participating centers between 2004 and 2009 were retrospectively reviewed. Patient demographics and procedural data were extracted from patient records and analyzed. A total of 434 patients with AVNRT who underwent cryoablation were identified. Cryoablation was used as the exclusive ablation method for 379 patients. For 97 % (368/379) of these patients, cryoablation was acutely successful. A higher acute success rate was found with the 6-mm-tip catheter (99 %) than with the 4-mm-tip catheter (91 %) (p < 0.01). Recurrence was experienced by 7.3 % of the patients. Recurrence was more likely for those treated with the 4-mm-tip catheter (6/42, 14 %) than for those who had the larger catheters (12/204, 6 %) No patient experienced permanent heart block. Success and recurrence rates for this cohort of patients were similar to those reported for RFA used to treat AVNRT in pediatric patients. The findings show a higher success rate and a lower recurrence rate after cryoablation with a 6-mm-tip catheter than after use of the 4-mm-tip catheter, with an associated excellent safety profile.

Iatrogenic atrioventricular reentrant tachycardia following Bjork/Fontan palliation of tricuspid atresia: Electro-anatomic mapping, ablation, review and possible mechanism.

This case report describes the successful ablation of an iatrogenic accessory pathway in a Fontan patient. A 15-year-old girl with tricuspid atresia was palliated with a Bjork modification Fontan procedure; six years later she developed supraventricular tachycardia. Electro-anatomic mapping during electrophysiology study localized a concealed iatrogenic atrioventricular accessory pathway and facilitated successful ablation using radiofrequency energy. This report reviews the reported cases of anomalous atrioventricular conduction (antegrade only, retrograde only [Hager, et al., J Thorac Cardiovasc Surg 2005;130:48-53], both [Liberman, et al., Pacing Clin Electrophysiol 2000;23:914-6]) after the Fontan/Bjork repair, outlines a potential pathophysiologic mechanism for the post-operative tachyarrhythmia and highlights the usefulness of electro-anatomic mapping in identifying unusual arrhythmias in post-operative patients with complex congenital heart disease.