Publications by authors named "Michael J Silka"

66 Publications

Utility of Surveillance Ambulatory Rhythm Monitoring in the Pediatric Fontan Population.

Pediatr Cardiol 2021 May 7. Epub 2021 May 7.

Division of Cardiology, Children's Hospital Los Angeles, 4650 Sunset Blvd, MS #34, Los Angeles, CA, 90049, USA.

Our institution established a Fontan surveillance plan, which included ambulatory rhythm monitoring (ARM) at 6, 10, 13, 16 and 19 years old, for early detection of Fontan-associated complications. We conducted a retrospective chart review of Fontan patients followed at our institution 2014-2018 to determine the utility of surveillance ARMs. 139 ARMs from 83 patients were included. ARMs with supraventricular tachycardia, sinus node dysfunction, accelerated junctional rhythm, > 1st degree atrioventricular block, and complex ventricular ectopy were classified as positive for arrhythmia. Arrhythmias were occult if detected on surveillance ARM. The ARM indication was surveillance in 78 (56%) and clinically indicated in 61 (44%). 52 (37%) ARMs in 27 (33%) patients had an arrhythmia. There was no difference in the age of patients with and without arrhythmias [median 10.9 (6.5, 17.1 years) vs. 8.8 (7, 13.6 years), p = 0.5]. Clinically indicated ARMs more frequently demonstrated arrhythmias than surveillance ARMs (52% vs. 26%, p < 0.01). Compared to patients without arrhythmias, those with arrhythmias were more likely to be female (48% vs. 23%, p = 0.02), have a single right ventricle (46% vs. 19%, p < 0.01) and longer QRS duration on ECG [100 (91, 116 ms) vs. 94 (84, 104 ms), p = 0.046]. Patients with occult arrhythmias were less likely to have moderate to severe atrioventricular valvar regurgitation (0% vs. 46%; p = 0.04) or ventricular dysfunction (0% vs. 46%; p = 0.04) than those with clinical arrhythmia(s). Arrhythmia findings resulted in change in management for 16/52 (31%) ARMs. The findings suggest the frequent presence of arrhythmias on periodic ARMs in patients following the Fontan procedure regardless of symptomatic status.
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http://dx.doi.org/10.1007/s00246-021-02630-0DOI Listing
May 2021

Characteristics of antegrade-only accessory pathways in children and adolescents.

Cardiol Young 2021 Jan 25:1-5. Epub 2021 Jan 25.

The Division of Cardiology, Department of Pediatrics, Children's Hospital Los Angeles, University of Southern California, Los Angeles, CA, USA.

There is minimal data regarding antegrade-only accessory pathways in young patients. Given evolving recommendations and treatments, retrospective analysis of the clinical and electrophysiologic properties of antegrade-only pathways in patients <21 years old was performed, with subsequent comparison of electrophysiology properties to age-matched controls with bidirectional pathways. Of 522 consecutive young patients with ventricular pre-excitation referred for electrophysiology study, 33 (6.3%) had antegrade-only accessory pathways. Indications included palpitations (47%), chest pain (25%), and syncope (22%). The shortest value for either the accessory pathway effective refractory period or the pre-excited R-R interval was taken for each patient, with the median of the antegrade-only group significantly greater than shortest values for the bidirectional group (310 [280-360] ms versus 270 [240-302] ms, p < 0.001). However, the prevalence of pathways with high-risk properties (effective refractory period or shortest pre-excited R-R interval <250 ms) was similar in both study patients and controls (13% versus 21%) (p = 0.55). Sixteen patients had a single antegrade-only accessory pathway and no inducible arrhythmia. Six patients had Mahaim fibres, all right anterolateral with inducible antidromic reciprocating tachycardia. However, 11 patients with antegrade-only accessory pathways and 3 with Mahaim fibres had inducible tachycardia due to a second substrate recognised at electrophysiology study. These included concealed accessory pathways (7), bidirectional accessory pathways (5), and atrioventricular node re-entry (2). Antegrade-only accessory pathways require comprehensive electrophysiology evaluation as confounding factors such as high-risk conduction properties or inducible Supraventricular Tachycardia (SVT) due to a second substrate of tachycardia are often present.
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http://dx.doi.org/10.1017/S1047951121000056DOI Listing
January 2021

Pediatric unexplained cardiac arrest: When no answer is also an answer.

Heart Rhythm 2020 06 24;17(6):982-983. Epub 2020 Feb 24.

Division of Cardiology, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California.

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http://dx.doi.org/10.1016/j.hrthm.2020.02.019DOI Listing
June 2020

A comparison of oral flecainide and amiodarone for the treatment of recurrent supraventricular tachycardia in children.

Pacing Clin Electrophysiol 2019 06 28;42(6):670-677. Epub 2019 Mar 28.

Division of Cardiology, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California.

Background: Supraventricular tachycardia (SVT) in children can be difficult to treat when first-line therapies (beta-blockade or digoxin) are not effective. Both flecainide and amiodarone are used as second-line therapies. We sought to compare the efficacy and safety of flecainide and amiodarone in pediatric patients with recurrent SVT.

Methods: Pediatric patients treated with oral flecainide or oral amiodarone for SVT between 2006 and 2015 were studied. Tachycardia mechanisms included orthodromic reciprocating tachycardia (ORT), intra-atrial reentrant tachycardia (IART), and ectopic atrial tachycardia (EAT). Outcomes were classified as full success, partial success (requiring additional intervention), or failure.

Results: Seventy-four patients were included (median age 46 days, range 1 day to 19 years). Flecainide was used in 47 patients and amiodarone in 27 patients. Full success was achieved in 68% and 59%, respectively (P = 0.28). Partial success was achieved in 13% and 19%, respectively (P = 0.12). Treatment failed in 19% and 22%, respectively (P = 0.97). Ten crossover patients received the second medication after the first failed. Of five amiodarone-to-flecainide crossovers, four achieved success on flecainide alone. Of five flecainide-to-amiodarone crossovers, two achieved success. Minor adverse events occurred in 9% of flecainide and 22% of amiodarone patients (P = 0.16). No significant differences were seen by arrhythmia subtype (36 EAT, 28 ORT, 10 IART), congenital heart disease (n = 38), or age group (56 infants).

Conclusions: Oral flecainide and amiodarone achieved meaningful arrhythmia control in 81% and 78% of pediatric patients with recurrent SVT, respectively. Those who failed amiodarone had encouraging outcomes when changed to flecainide.
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http://dx.doi.org/10.1111/pace.13662DOI Listing
June 2019

Prenatal diagnosis and management of congenital complete heart block.

Birth Defects Res 2019 05 1;111(8):380-388. Epub 2019 Mar 1.

Department of Obstetrics and Gynecology/Division of Maternal Fetal Medicine, Keck School of Medicine of USC, Los Angeles, California.

Congenital complete heart block (CCHB) is a life-threatening medical condition in the unborn fetus with insufficiently validated prenatal interventions. Maternal administration of medications aimed at decreasing the immune response in the fetus and beta-agonists intended to increase fetal cardiac output have shown only marginal benefits. Anti-inflammatory therapies cannot reverse CCHB, but may decrease myocarditis and improve heart function. Advances in prenatal diagnosis and use of strict surveillance protocols for delivery timing have demonstrated small improvements in morbidity and mortality. Ambulatory surveillance programs and wearable fetal heart rate monitors may afford early identification of evolving fetal heart block allowing for emergent treatment. There is also preliminary data suggesting a roll for prevention of CCHB with hydroxychloroquine, but the efficacy and safety is still being studied. To date, intrauterine fetal pacing has not been successful due to the high-risk invasive placement techniques and potential problems with lead dislodgement. The development of a fully implantable micropacemaker via a minimally invasive approach has the potential to pace fetal patients with CCHB and thus delay delivery and allow fetal hydrops to resolve. The challenge remains to establish accepted prenatal interventions capable of successfully managing CCHB in utero until postnatal pacemaker placement is successfully achieved.
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http://dx.doi.org/10.1002/bdr2.1459DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6474813PMC
May 2019

Home use of a compact, 12‑lead ECG recording system for newborns.

J Electrocardiol 2019 Mar - Apr;53:89-94. Epub 2019 Jan 25.

Division of Pediatric Cardiology, Department of Pediatrics, Los Angeles Biomedical Research Institute, Harbor-UCLA Medical Center, Torrance, CA, USA; David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.

Background: An easy-to-operate ECG recorder should be useful for newborn screening for heart conditions, by health care workers - or parents. We developed a one-piece electrode strip and a compact, 12‑lead ECG recorder for newborns.

Method: We enrolled 2582 newborns in a trial to assess abilities of parents to record a 12‑lead ECG on their infants (2-4 weeks-old). Newborns were randomized to recordings by parents (1290) or our staff (1292 controls). Educational backgrounds of parents varied, including 64% with no more than a high school diploma.

Results: For newborns randomized to parent recorded ECGs, 94% of parents completed a 10-minute recording. However, 42.6% asked for verbal help, and 12.7% needed physical help. ECG quality was the same for recordings by parents versus staff.

Conclusions: By use of a one-piece electrode strip and a compact recorder, 87% of parents recorded diagnostic quality ECGs on their newborn infants, with minimal assistance.
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http://dx.doi.org/10.1016/j.jelectrocard.2019.01.086DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6458066PMC
July 2020

A prospective 5-year study of exercise performance following Melody valve implant.

Am Heart J 2019 03 29;209:47-53. Epub 2018 Dec 29.

Children's Hospital of Orange County, University of California, Irvine, CA. Electronic address:

Background: The long-term benefits of Melody valve implant for right ventricular outflow tract conduit obstruction or insufficiency on exercise capacity are undefined.

Methods: As part of the Melody valve clinical trial, 136 patients with congenital heart disease underwent serial cardiopulmonary exercise testing prior to, 6 months after, and annually for up to 5 years postimplant.

Results: Mean age at Melody valve implantation was 22.4 ± 0.9 years (range 7-53 years). The 95 patients who completed the study protocol provide the basis of this report. An initial improvement in % predicted workload was present at 6 months postimplant; however, at the final (5 year) follow-up, sustained or further improvements in workload were not demonstrated for the entire cohort compared to baseline. By subgroup analysis, age <17 years at implant and pulmonary regurgitation as the primary lesion were variables associated with sustained improvement in exercise performance. There were sustained improvements in the ventilatory equivalents for O (minute ventilation/O intake, P = .01) and CO (minute ventilation/CO output, P < .01) at the ventilatory anaerobic threshold at the study conclusion. Improvements in forced vital capacity were also observed during the study but not sustained at the final follow-up.

Conclusions: A cautious appraisal of the cardiovascular benefits of Melody valve implant on sustained improvements in exercise performance appears warranted. Although the observed changes in pulmonary function suggest improved restrictive lung physiology and more efficient gas exchange, after an initial increase in % predicted performance, neither sustained nor further improvements in exercise performance were observed, except in specific patient subgroups.
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http://dx.doi.org/10.1016/j.ahj.2018.12.014DOI Listing
March 2019

International Triadin Knockout Syndrome Registry.

Circ Genom Precis Med 2019 02;12(2):e002419

Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics, Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, and Division of Heart Rhythm Services, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN (D.J.C., D.J.T., J.R.G., J.M.B., R.K.R., M.J.A.).

Background: Triadin knockout syndrome (TKOS) is a rare, inherited arrhythmia syndrome caused by recessive null mutations in TRDN-encoded cardiac triadin. Based previously on 5 triadin null patients, TKOS has been characterized by extensive T-wave inversions, transient QT prolongation, and severe disease expression of exercise-induced cardiac arrest in early childhood refractory to conventional therapy.

Methods: We have established the International Triadin Knockout Syndrome Registry to include patients who have genetically proven homozygous/compound heterozygous TRDN null mutations. Clinical/genetic data were collected using an online survey generated through REDCap.

Results: Currently, the International Triadin Knockout Syndrome Registry includes 21 patients (11 males, average age of 18 years) from 16 families. Twenty patients (95%) presented with either cardiac arrest (15, 71%) or syncope (5, 24%) at an average age of 3 years. Mild skeletal myopathy/proximal muscle weakness was noted in 6 (29%) patients. Of the 19 surviving patients, 16 (84%) exhibit T-wave inversions, and 10 (53%) have transient QT prolongation > 480 ms. Eight of 9 patients had ventricular ectopy on exercise stress testing. Thirteen (68%) patients have received implantable defibrillators. Despite various treatment strategies, 14 (74%) patients have had recurrent breakthrough cardiac events.

Conclusion: TKOS is a potentially lethal disease characterized by T-wave inversions in the precordial leads, transient QT prolongation in some, and recurrent ventricular arrhythmias at a young age despite aggressive treatment. Patients displaying this phenotype should undergo TRDN genetic testing as TKOS may be a cause for otherwise unexplained cardiac arrest in young children. As gene therapy advances, enrollment into the International Triadin Knockout Syndrome Registry is encouraged to better understand TKOS and to ready a well-characterized cohort for future TRDN gene therapy trials.
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http://dx.doi.org/10.1161/CIRCGEN.118.002419DOI Listing
February 2019

Cardiac Resynchronization Therapy in Pediatrics.

J Innov Card Rhythm Manag 2018 Aug 15;9(8):3256-3264. Epub 2018 Aug 15.

Division of Cardiology, Children's Hospital Los Angeles, Los Angeles, CA, USA.

Cardiac resynchronization therapy (CRT) has proven to be a powerful and effective tool in the treatment of adults with severe dilated or ischemic cardiomyopathy. A substantial portion of the adult heart failure population has severely depressed systolic function, heart failure symptoms, QRS prolongation, and left bundle branch block. Indications for CRT in adults are commonly focused on these characteristics. However, pediatric patients represent a heterogeneous group with many etiologies of heart failure and anatomic variants, with most of them not fitting the typical adult CRT criteria. The heterogeneity of the pediatric population has hindered the identification of ideal candidates for CRT, but initial experience with CRT in various groups of pediatric patients has been encouraging. This article reviews indications for and outcomes of CRT in pediatric and congenital heart disease patients.
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http://dx.doi.org/10.19102/icrm.2018.090804DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7252792PMC
August 2018

Minimally Invasive Implantation of a Micropacemaker Into the Pericardial Space.

Circ Arrhythm Electrophysiol 2018 07;11(7):e006307

Department of Biomedical Engineering, University of Southern California, Los Angeles (L.Z., S.M.R., V.N., G.E.L.).

Background: Permanent cardiac pacemakers require invasive procedures with complications often related to long pacemaker leads. We are developing a percutaneous pacemaker for implantation of an entire pacing system into the pericardial space.

Methods: Percutaneous micropacemaker implantations were performed in 6 pigs (27.4-34.1 kg) using subxyphoid access to the pericardial space. Modifications in the implantation methods and hardware were made after each experiment as the insertion method was optimized. In the first 5 animals, nonfunctional pacemaker devices were studied. In the final animal, a functional pacemaker was implanted.

Results: Successful placement of the entire nonfunctional pacing system into the pericardial space was demonstrated in 2 of the first 5 animals, and successful implantation and capture was achieved using a functional system in the last animal. A sheath was developed that allows retractable features to secure positioning within the pericardial space. In addition, a miniaturized camera with fiberoptic illumination allowed visualization of the implantation site before electrode insertion into myocardium. All animals studied during follow-up survived without symptoms after the initial postoperative period.

Conclusions: A novel micropacemaker system allows cardiac pacing without entering the vascular space or surgical exposure of the heart. This pericardial pacemaker system may be an option for a large number of patients currently requiring transvenous pacemakers but is particularly relevant for patients with restricted vascular access, young children, or those with congenital heart disease who require epicardial access.
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http://dx.doi.org/10.1161/CIRCEP.118.006307DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6050018PMC
July 2018

Pediatric survivors of out-of-hospital ventricular fibrillation: Etiologies and outcomes.

Heart Rhythm 2018 01 18;15(1):116-121. Epub 2017 Aug 18.

Division of Cardiology, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California.

Background: In general, the prognosis is poor for pediatric patients who experience out-of-hospital (OOH) cardiac arrest, with survival rates of 12% to 29%.

Objective: The purpose of this study was to describe the causes and outcomes of pediatric patients with documented ventricular fibrillation (VF) at resuscitation from OOH cardiac arrest with sustained return of spontaneous circulation after defibrillation and survival to hospital admission.

Methods: Retrospective analysis of OOH-VF patients <19 years of age evaluated between 2004 and 2016 was performed. Primary outcome measures included demographics, arrest and resuscitation parameters, cardiac diagnoses, survival, and neurologic outcome.

Results: Forty-five patients fulfilled study criteria (median age 12 years; range 2 months to 18 years). Cardiac arrest occurred in public in 68% of cases, with bystander cardiopulmonary resuscitation in 42% before arrival of emergency medical services. All patients underwent defibrillation (1-6 shocks) with return of spontaneous circulation and survival to hospital admission. Underlying etiologies were primary electrical disease (33%), cardiomyopathy (27%), congenital heart disease (11%), other (13%), and unknown (16%). Before arrest, 40% of patients had a cardiac diagnosis and 26% had symptoms. Ultimately, 40 of 45 patients (89%) survived resuscitation to hospital discharge. During 72 ± 37 months of follow-up, 38% of survivors had a normal neurologic outcome, whereas 32% had mild neurologic impairment and 30% had moderate-to-severe neurologic impairment.

Conclusion: In pediatric patients resuscitated from OOH-VF, a cardiovascular cause was identified in >80%. Regardless of cause, survival and neurologic prognosis appear improved compared to patients with asystole or pulseless electrical activity. These findings support early rhythm assessment and advanced cardiopulmonary resuscitation protocols in pediatric cardiac arrest victims.
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http://dx.doi.org/10.1016/j.hrthm.2017.08.014DOI Listing
January 2018

Prevalence of Atrial Fibrillation and Permanent Atrial Arrhythmias in Congenital Heart Disease: Sequel or Series?

J Am Coll Cardiol 2017 08;70(7):866-868

Division of Cardiology, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California.

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http://dx.doi.org/10.1016/j.jacc.2017.06.052DOI Listing
August 2017

Return to play in the athlete with cardiac disease: who decides and what is the protocol?

Authors:
Michael J Silka

Cardiol Young 2017 Jan;27(S1):S110-S114

Division of Cardiology,Children's Hospital Los Angeles,Keck School of Medicine,University of Southern California,Los Angeles,California,United States of America.

Improved public awareness and advances in medical diagnostics have resulted in the development of criteria to determine eligibility or disqualification for the athlete with cardiovascular abnormalities. Simultaneously, protocols have been developed for athletes with concussion or orthopaedic injuries to guide team physicians and consultants in return-to-play decisions. However, there are currently inadequate data to allow the development of such protocols for athletes with cardiovascular abnormalities who have undergone treatment. Further complicating the decision process is the designation of the team physician as the ultimate authority in making return-to-play decisions - where the team physician often is an employee of the team and supports the team's goal and players as well as the individual athlete. This review will discuss the ethical dilemma of the team physician and the role of the cardiovascular consultant. Following this, current data and practices regarding return to play will be discussed for the following conditions or diagnoses: following catheter ablation for supraventricular tachycardia; following pacemaker or implantable cardioverter-defibrillator implantation; unexplained syncope; and the athlete with a genetic mutation in the absence of any phenotype of associated disease. These recommendations will undoubtedly continue to evolve and improve and should be considered at this time as a point of departure.
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http://dx.doi.org/10.1017/S104795111600233XDOI Listing
January 2017

Analytical Modeling for Computing Lead Stress in a Novel Epicardial Micropacemaker.

Cardiovasc Eng Technol 2017 03 9;8(1):96-105. Epub 2017 Jan 9.

Medical Device Development Facility, Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, 1042 Downey Way, Los Angeles, CA, 90089, USA.

Implantation and maintenance of a permanent cardiac pacing system in children remains challenging due to small patient size, congenital heart defects and somatic growth. We are developing a novel epicardial micropacemaker for children that can be implanted on the epicardium within the pericardial space via a minimally-invasive technique. The key design configurations include a novel open-coiled lead in which living tissue replaces the usual polymeric support for the coiled conductor. To better understand and be able to predict the behavior of the implanted lead, we performed a radiographic image-based modeling study on a chronic animal test. We report a pilot study in which two mechanical dummy pacemakers with epicardial leads were implanted into an adult pig model via a minimally invasive approach. Fluoroscopy was obtained on the animal on Post-Operative Days #9, #35 and #56 (necropsy). We then constructed an analytic model to estimate the in vivo stress conditions on the open-coil lead based on the analysis of orthogonal biplane radiographic images. We obtained geometric deformation data of the implanted lead including elongation magnitudes and bending radii from sequenced films of cardiac motion cycles. The lead stress distribution was investigated on each film frame and the point of maximum stress (Mean Stress = 531.4 MPa; Alternating Stress = ± 216.4 MPa) was consistently where one of the leads exited the pericardial space, a deployment that we expected to be unfavorable. These results suggest the modeling approach can provide a basis for further design optimization. More animal tests and modeling will be needed to validate whether the novel lead design could meet the requirements to withstand ~200 million cardiac motion cycles over 5 years.
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http://dx.doi.org/10.1007/s13239-017-0292-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5321717PMC
March 2017

Characteristics of Decremental Accessory Pathways in Children.

Circ Arrhythm Electrophysiol 2016 11;9(11)

From the Division of Cardiology, Children's Hospital Los Angeles and Keck School of Medicine, University of Southern California (A.C.H., M.J.S., Y.B.-C.); and Biostatistics Core, Children's Hospital, Los Angeles CA (C.P.W.).

Background: Although retrograde decremental accessory pathways (DAPs) are thought to typically present as permanent junctional reciprocating tachycardia (permanent junctional reciprocating tachycardia), they may also be diagnosed unexpectedly during electrophysiology study. We aimed to compare the clinical and electrophysiological characteristics of patients with DAPs to an age-matched cohort with nondecremental accessory pathways.

Methods And Results: We retrospectively studied pediatric patients (<21 years of age) with retrograde DAPs and an age-matched control population with nondecremental accessory pathways who underwent electrophysiology study between 2005 and 2014. Decrement was defined as rate-dependent prolongation of the local ventriculo-atrial time by >30 ms. Twenty-six patients with DAPs were compared with 73 controls (mean age at electrophysiology study 9.8±5.7 and 10.3±5.2 years, respectively [P=nonsignificant]). Compared with controls, patients with DAPs had more frequent syncope (5/26 [19%] versus 3/73 [4%]; P=0.02) and ventricular dysfunction (6/26 [23%] versus 4/73 [6%]; P=0.04). Only 11 (42%) DAP patients manifested clinical permanent junctional reciprocating tachycardia, and these patients had more syncope (5/11 [45%] versus 0/15 [0%]; P<0.01), slower orthodromic reciprocating tachycardia (176±44 beats per minute versus 229±31 beats per minute; P=0.001), and longer ventriculo-atrial times (mean maximum ventriculo-atrial times of 283±116 ms versus 208±42 ms; P=0.02) compared with those with DAPs without clinical permanent junctional reciprocating tachycardia. DAPs and controls had similar rates of acute ablation success (23/26 [89%] versus 67/73 [92%]; P=nonsignificant) and recurrences (1/23 [4%] versus 2/67 [3%]; P=nonsignificant).

Conclusions: The majority of pediatric patients with DAPs do not present with clinical permanent junctional reciprocating tachycardia. DAPs are associated with more severe symptoms, but ablation outcomes are similar to those of age-matched controls.
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http://dx.doi.org/10.1161/CIRCEP.116.004190DOI Listing
November 2016

A prospective 5-year study of the frequency of arrhythmias during serial exercise testing and clinical follow-up after Melody valve implant.

Heart Rhythm 2016 11 21;13(11):2135-2141. Epub 2016 Jul 21.

Children's Hospital of Orange County, University of California Irvine, Orange, California. Electronic address:

Background: Although percutaneous Melody valve implant has become an accepted alternative to surgical pulmonary valve replacement in patients with congenital heart disease, the benefit regarding frequency and severity of arrhythmias remains undefined.

Objective: The purpose of this study was to evaluate the impact of Melody valve implant on the type and frequency of arrhythmias during cardiopulmonary exercise testing (CPET) and subsequent clinical outcome.

Methods: As part of the phase I Melody valve clinical trial, 136 patients with congenital heart disease underwent prospective serial evaluation including CPET before implant, 6 months after implant, and annually thereafter for 5 years. Arrhythmias were defined as premature ventricular complexes (PVCs) and supraventricular or ventricular tachycardia (VT).

Results: Before Melody implant, PVCs occurred in 55 patients (40%) and nonsustained ventricular tachycardia (NSVT) in 1 patient during CPET. Median age at valve implantation was 19.0 years (range 7-53 years). During median follow-up of 4.9 years (range 0.8-7.3 years), there was no significant change in the proportion of patients with PVCs during CPET at any follow-up interval (40%-45%). However, postimplant, NSVT occurred in 18 patients, including 8 during CPET. Diagnoses in the patients with NSVT were tetralogy of Fallot (11), transposition (2), and post-Ross procedure (5). Improved hemodynamic status was not associated with resolution or prevention of arrhythmias.

Conclusion: Despite improvement in hemodynamics, Melody valve implant was not associated with resolution or prevention of arrhythmias during CPET. PVCs or VT may be related to pathologic hypertrophy, fibrosis, dilation, or possible mechanical effects of the Melody device.
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http://dx.doi.org/10.1016/j.hrthm.2016.07.023DOI Listing
November 2016

Minimally invasive implantable fetal micropacemaker: mechanical testing and technical refinements.

Med Biol Eng Comput 2016 Dec 28;54(12):1819-1830. Epub 2016 Mar 28.

Medical Device Development Facility, Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, 1042 Downey Way, Los Angeles, CA, 90089, USA.

This paper discusses the technical and safety requirements for cardiac pacing of a human fetus with heart failure and hydrops fetalis secondary to complete heart block. Engineering strategies to meet specific technical requirements were integrated into a systematic design and implementation consisting of a novel fetal micropacemaker, a percutaneous implantation system, and a sterile package that enables device storage and recharging maintenance in a clinical setting. We further analyzed observed problems on myocardial fixation and pacing lead fatigue previously reported in earlier preclinical trials. This paper describes the technical refinements of the implantable fetal micropacemaker to overcome these challenges. The mechanical performance has been extensively tested to verify the improvement of reliability and safety margins of the implantation system.
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http://dx.doi.org/10.1007/s11517-016-1470-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5040620PMC
December 2016

A Comparison of AV Nodal Reentrant Tachycardia in Young Children and Adolescents: Electrophysiology, Ablation, and Outcomes.

Pacing Clin Electrophysiol 2015 Nov 24;38(11):1325-32. Epub 2015 Aug 24.

Division of Cardiology, Children's Hospital Los Angeles, Los Angeles, California; and Keck School of Medicine, University of Southern California, Los Angeles, California.

Background: Atrioventricular nodal reentrant tachycardia (AVNRT) typically occurs in adolescents and adults with limited data regarding AVNRT in young children.

Methods: All patients with AVNRT who underwent electrophysiology study and ablation between 2005 and 2012 were retrospectively studied. Patients were stratified by age <10 years (young AVNRT) or ≥10 years (older AVNRT). Young AVNRT patients were also compared to age-matched patients with orthodromic reentrant tachycardia (ORT).

Results: A total of 275 studies in 272 patients were evaluated including 38 young AVNRT patients (7.7 ± 1.5 years) and 202 older AVNRT patients (14.9 ± 2.1 years). An atrial-His jump ≥50 ms was demonstrated in 56% of young and 64% of older patients. Slow pathway modification was attempted in all but one older patient with acute ablation success achieved in all. RF ablation was the primary ablation modality with cryoablation used in 10 patients (three young and seven older). Recurrences were rare (zero young and three older patients) despite residual AVNRT echo beats postablation in 34% of young and 40% of older patients. One older AVNRT patient (0.5%) required a pacemaker for heart block while no complications occurred in the young patients. Electrophysiologic parameters were comparable to the 35 age-matched young ORT group (7.7 ±1.7 years) in whom supraventricular tachycardia was more inducible.

Concusions: Slow pathway modification for AVNRT in children resulted in high success and low complication rates, regardless of age. Recurrence of tachycardia was infrequent despite persistence of AVNRT echo beats in 34-40% of patients following slow pathway modification.
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http://dx.doi.org/10.1111/pace.12699DOI Listing
November 2015

Preclinical testing and optimization of a novel fetal micropacemaker.

Heart Rhythm 2015 Jul 14;12(7):1683-90. Epub 2015 Mar 14.

Department of Obstetrics and Gynecology, Keck School of Medicine, University of Southern California, Los Angeles, California.

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http://dx.doi.org/10.1016/j.hrthm.2015.03.022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4485563PMC
July 2015

Comparison of formulas for calculation of the corrected QT interval in infants and young children.

J Pediatr 2015 Apr 31;166(4):960-4.e1-2. Epub 2015 Jan 31.

Division of Pediatric Cardiology, Los Angeles Biomedical Research Institute at Harbor-University of California, Los Angeles Medical Center, Torrance, CA. Electronic address:

Objective: To compare 4 heart rate correction formulas for calculation of the rate corrected QT (QTc) interval among infants and young children.

Study Design: R-R and QT intervals were measured from digital electrocardiograms. QTc were calculated with the Bazett, Fridericia, Hodges, and Framingham formulas. QTc vs R-R graphs were plotted, and slopes of the regression lines compared. Slopes of QTc-R-R regression lines close to zero indicate consistent QT corrections over the range of heart rates.

Results: We reviewed electrocardiograms from 702 children, with 233 (33%) <1 year of age and 567 (81%) <2 years. The average heart rate was 122 ± 20 bpm (median 121 bpm). The slopes of the QTc-R-R regression lines for the 4 correction formulas were -0.019 (Bazett); 0.1028 (Fridericia); -0.1241 (Hodges); and 0.2748 (Framingham). With the Bazett formula, a QTc >460 ms was 2 SDs above the mean, compared with "prolonged" QTc values of 414, 443, and 353 ms for the Fridericia, Hodges, and Framingham formulas, respectively.

Conclusions: The Bazett formula calculated the most consistent QTc; 460 ms is the best threshold for prolonged QTc. The study supports continued use of the Bazett formula for infants and children and differs from the use of the Fridericia correction during clinical trials of new medications.
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http://dx.doi.org/10.1016/j.jpeds.2014.12.037DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4380641PMC
April 2015

Current practices in the monitoring of cardiac rhythm devices in pediatrics and congenital heart disease.

Pediatr Cardiol 2015 Apr 20;36(4):821-6. Epub 2014 Dec 20.

Division of Cardiology, Children's Hospital Los Angeles, 4650 Sunset Boulevard, Mail Stop #34, Los Angeles, CA, 90027, USA.

Although guidelines for routine follow-up of pacemakers and implantable cardioverter defibrillators (ICDs) are available for adults, minimal data supports their appropriateness in pediatrics and congenital heart disease. This study aimed to define current practices of cardiac rhythm device (CRD) follow-up among pediatric electrophysiologists. Pediatric and Congenital EP Society (PACES) members were surveyed regarding frequency of CRD in-person follow-up as well as transtelephonic monitoring (TTM) and remote monitoring (RM) practices. If home monitoring was used, the effect on in-person follow-up was also evaluated. A total of 106 PACES members responded to the survey. Uncomplicated pacemaker and ICD patients were both followed in-person at a median interval of 6 months (range 1-12 months). TTM was utilized by 67 % of responders (median interval 3 months; range 1-6 months), while RM was used by 87 % for pacemakers (median interval 3 months; range 1-6 months) and 92 % for ICDs (median interval 3 months; range 2 weeks-6 months). When TTM was used, 21 % of responders reduced their frequency of pacemaker clinic visits. In comparison, RM reduced the frequency of clinic visits for pacemakers and ICDs in 32 and 31 % of responders, respectively. Patient age was an independent factor in determining CRD follow-up for 49 % of responders. While CRD follow-up by pediatric electrophysiologists in general follows adult guidelines, individual practices widely vary. In contrast to published recommendations in adults, TTM and RM utilization does not reduce the frequency of in-person visits for the majority of pediatric electrophysiologists.
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http://dx.doi.org/10.1007/s00246-014-1090-4DOI Listing
April 2015

Prevalence of arrhythmias during exercise stress testing in patients with congenital heart disease and severe right ventricular conduit dysfunction.

Am J Cardiol 2014 Aug 17;114(3):468-72. Epub 2014 May 17.

Department of Pediatrics, Children's Hospital Los Angeles, University of Southern California, Los Angeles, California. Electronic address:

The utility of cardiopulmonary exercise testing (CPET) to define the risks of arrhythmia and sudden death in postoperative patients with congenital heart disease (CHD) remains uncertain. As part of the US Melody valve trial, prospective standardized CPET, along with echocardiography, cardiac magnetic resonance imaging, and cardiac catheterization, were performed in 170 CHD patients with right ventricular outflow tract conduit dysfunction before Melody valve implantation. Ventricular premature complexes (VPC) occurred in 75 patients (44%) and were common during all phases of CPET (13% baseline, 24% exercise, and 23% recovery). Although no subjects had sustained arrhythmias, 2 had nonsustained ventricular tachycardia and 3 had nonsustained supraventricular tachycardia during recovery. There were no statistically significant differences between patients with or without VPCs in echocardiographic, cardiac magnetic resonance imaging, or catheterization measures of cardiac function. However, clinical parameters of age, New York Heart Association functional class ≥II, and ≥3 cardiac surgical procedures were correlated with VPCs. Persistent ventricular ectopy during all exercise stages was present in 11 patients (6.5%), including 3 of the 4 patients who died during follow-up. In conclusion, VPCs were common during CPET, although they were not correlated with various measures of hemodynamic impairment; conversely, increased age, functional class, and number of surgeries were correlated with an increased prevalence of VPCs. CPET appears to be of minimal risk for sustained arrhythmia provocation in CHD patients with right ventricular outflow tract conduits and various degrees of advanced subpulmonary ventricular dysfunction.
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http://dx.doi.org/10.1016/j.amjcard.2014.05.019DOI Listing
August 2014

Genetic variants for long QT syndrome among infants and children from a statewide newborn hearing screening program cohort.

J Pediatr 2014 Mar 31;164(3):590-5.e1-3. Epub 2013 Dec 31.

Department of Pediatrics, Harbor-UCLA Medical Center and Los Angeles Biomedical Research Institute, Torrance, CA.

Objectives: Autosomal recessive long QT syndrome (LQTS), or Jervell and Lange-Nielsen syndrome (JLNS), can be associated with sensorineural hearing loss. We aimed to explore newborn hearing screening combined with electrocardiograms (ECGs) for early JLNS detection.

Study Design: In California, we conducted statewide, prospective ECG screening of children ≤ 6 years of age with unilateral or bilateral, severe or profound, sensorineural or mixed hearing loss. Families were identified through newborn hearing screening and interviewed about medical and family histories. Twelve-lead ECGs were obtained. Those with positive histories or heart rate corrected QT (QTc) intervals ≥ 450 ms had repeat ECGs. DNA sequencing of 12 LQTS genes was performed for repeat QTc intervals ≥ 450 ms.

Results: We screened 707 subjects by ECGs (number screened/number of responses = 91%; number of responses/number of families who were mailed invitations = 54%). Of these, 73 had repeat ECGs, and 19 underwent gene testing. No subject had homozygous or compound heterozygous LQTS mutations, as in JLNS. However, 3 individuals (with QTc intervals of 472, 457, and 456 ms, respectively) were heterozygous for variants that cause truncation or missplicing: 2 in KCNQ1 (c.1343dupC or p.Glu449Argfs*14; c.1590+1G>A or p.Glu530sp) and 1 in SCN5A (c.5872C>T or p.Arg1958*).

Conclusions: In contrast to reports of JLNS in up to 4% of children with sensorineural hearing loss, we found no examples of JLNS. Because the 3 variants identified were unrelated to hearing, they likely represent the prevalence of potential LQTS mutations in the general population. Further studies are needed to define consequences of such mutations and assess the overall prevalence.
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http://dx.doi.org/10.1016/j.jpeds.2013.11.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3943925PMC
March 2014