Publications by authors named "Allison C Hill"

13 Publications

  • Page 1 of 1

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.
View Article and Find Full Text PDF

Download full-text PDF

Source
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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1017/S1047951121000056DOI Listing
January 2021

Genotype Predicts Outcomes in Fetuses and Neonates With Severe Congenital Long QT Syndrome.

JACC Clin Electrophysiol 2020 11 26;6(12):1561-1570. Epub 2020 Aug 26.

Joe DiMaggio Children's Hospital Heart Institute, Memorial Healthcare System, Hollywood, Florida, USA.

Objectives: This study sought to determine the relationship between long QT syndrome (LQTS) subtype (LTQ1, LTQ2, LTQ3) and postnatal cardiac events (CEs).

Background: LQTS presenting with 2:1 atrioventricular block or torsades de pointes in the fetus and/or neonate has been associated with risk for major CEs, but overall outcomes and predictors remain unknown.

Methods: A retrospective study involving 25 international centers evaluated the course of fetuses/newborns diagnosed with congenital LQTS and either 2:1 atrioventricular block or torsades de pointes. The primary outcomes were age at first CE after dismissal from the newborn hospitalization and death and/or cardiac transplantation during follow-up. CE was defined as aborted cardiac arrest, appropriate shock from implantable cardioverter-defibrillator, or sudden cardiac death.

Results: A total of 84 fetuses and/or neonates were identified with LQTS (12 as LQT1, 35 as LQT2, 37 as LQT3). Median gestational age at delivery was 37 weeks (interquartile range: 35 to 39 weeks) and age at hospital discharge was 3 weeks (interquartile range: 2 to 5 weeks). Fetal demise occurred in 2 and pre-discharge death in 1. Over a median of 5.2 years, there were 1 LQT1, 3 LQT2, and 23 LQT3 CEs (13 aborted cardiac arrests, 5 sudden cardiac deaths, and 9 appropriate shocks). One patient with LQT1 and 11 patients with LQT3 died or received cardiac transplant during follow-up. The only multivariate predictor of post-discharge CEs was LQT3 status (LQT3 vs. LQT2: hazard ratio: 8.4; 95% confidence interval: 2.6 to 38.9; p < 0.001), and LQT3, relative to LQT2, genotype predicted death and/or cardiac transplant (p < 0.001).

Conclusions: In this large multicenter study, fetuses and/or neonates with LQT3 but not those with LQT1 or LQT2 presenting with severe arrhythmias were at high risk of not only frequent, but lethal CEs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jacep.2020.06.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7679474PMC
November 2020

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.

View Article and Find Full Text PDF

Download full-text PDF

Source
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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/pace.13662DOI Listing
June 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
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.
View Article and Find Full Text PDF

Download full-text PDF

Source
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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.hrthm.2017.08.014DOI Listing
January 2018

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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/CIRCEP.116.004190DOI Listing
November 2016

Mixed aortic valve disease in the young: initial observations.

Pediatr Cardiol 2014 Aug 22;35(6):934-42. Epub 2014 Feb 22.

Department of Cardiology, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA, 02115, USA.

The short-term surgical results for mixed aortic valve disease (MAVD) and the long-term effects on the left ventricle (LV) are unknown. Retrospective review identified patients with at least both moderate aortic stenosis (AS) and aortic regurgitation (AR) before surgical intervention. A one-to-one comparison cohort of patients with MAVD not referred for surgical intervention was identified. The 45 patients in this study underwent surgical management for MAVD. A control group of 45 medically managed patients with MAVD also was identified. Both groups had elevated LV end-diastolic volume (EDV), elevated LV mass, a normal LV mass:volume ratio (MVR), and a normal ejection fraction. Both groups had diastolic dysfunction shown by early diastolic pulsed-Doppler mitral inflow/early diastolic tissue Doppler velocity z-score. The LV end-diastolic pressure (EDP) was correlated with age (R = 0.4; p = 0.03) and LV MVR (R = 0.4; p = 0.03) but not with AS, AR, or the score combining gradient and LV size. As shown by 6- to 12-month postoperative echocardiograms, aortic valve gradients and AR significantly improved (gradient 65 ± 17 to 28 ± 18 mmHg, p = 0.01; median regurgitation grade moderate to mild; p < 0.01), LV EDV normalized, and LV mass significantly improved (p < 0.01). Diastolic dysfunction was unchanged. Symptoms did not correlate with any measured parameter, but the preoperative symptoms resolved. In conclusion, despite diastolic dysfunction, systolic function is invariably preserved, and symptoms are not correlated with aortic valve function or LV EDP. Current surgical practice preserves LV mechanics and results in short-term improvement in valve function and symptoms.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00246-014-0878-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6951795PMC
August 2014

Do pediatric electrophysiologists read pre-participation screening electrocardiograms more accurately than general pediatric cardiologists?

J Pediatr 2013 Dec 29;163(6):1775-7. Epub 2013 Aug 29.

Department of Pediatrics, Lucile Packard Children's Hospital, Stanford University, Palo Alto, CA.

Pre-participation electrocardiogram (ECG) screening of athletes is controversial. Pediatric electrophysiologists do not interpret screening ECGs more accurately than pediatric cardiologists with average number of correct ECG interpretations of 13.1-12.4 (P = .14). Electrophysiologists ordered fewer follow-up tests and were more likely to give sports recommendations based on published guidelines.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jpeds.2013.07.034DOI Listing
December 2013

Electrical and mechanical dyssynchrony in pediatric pulmonary hypertension.

J Heart Lung Transplant 2012 Aug 8;31(8):825-30. Epub 2012 Jun 8.

Department of Pediatrics, Division of Cardiology, Stanford University Medical School, Palo Alto, CA, USA.

Background: Electrical and mechanical dyssynchrony are often seen in patients with left ventricular failure. In pediatric pulmonary hypertension (PH), right ventricular failure predominates; however, the prevalence of electrical and/or mechanical dyssynchrony in these patients is unknown. We examined the prevalence of electrical and mechanical dyssynchrony in pediatric PH patients.

Methods: Medical records (including, functional status, electrocardiograms and echocardiograms) of pediatric PH patients were reviewed. QRS duration z-scores were calculated to determine electrical dyssynchrony. Echo vector velocity imaging was used to calculate the mechanical dyssynchrony index (DI).

Results: Seventy-seven PH patients (idiopathic pulmonary arterial hypertension [IPAH]: n = 26; congenital heart disease: n = 41; other: n = 10) were studied. Electrical dyssynchrony was seen in 84% (p < 0.01 vs historic controls), with a mean z-score of 4.3 (95% CI 3.5 to 5.1). There was no difference between those with IPAH, z = 3.6 (95% CI 2.5 to 4.6), and those without, z = 4.7 (95% CI 3.6 to 5.8). Mechanical dyssynchrony was seen in 76% of patients (mean DI = 66 ± 47 vs 18 ± 8 milliseconds in historic controls, p < 0.01) in both IPAH and non-IPAH patients. Post-operative congenital heart disease patients had the largest dyssynchrony index. No correlation was found among electrical or mechanical dyssynchrony, hemodynamics or disease severity.

Conclusions: Significant electrical and mechanical dyssynchrony is present in pediatric PH patients, regardless of etiology. The overall effect of electrical and mechanical dyssynchrony on outcomes in this patient population is still unknown. Select patients may benefit from resynchronization therapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.healun.2012.04.004DOI Listing
August 2012

Accuracy of interpretation of preparticipation screening electrocardiograms.

J Pediatr 2011 Nov 14;159(5):783-8. Epub 2011 Jul 14.

Department of Pediatrics, Stanford University, Stanford, CA, USA.

Objective: To evaluate the accuracy of pediatric cardiologists' interpretations of electrocardiograms (ECGs).

Study Design: A series of 18 ECGs that represented conditions causing pediatric sudden cardiac death or normal hearts were interpreted by 53 members of the Western Society of Pediatric Cardiology. Gold-standard diagnoses and recommendations were determined by 2 electrophysiologists (100% concordance).

Results: The average number of correct ECG interpretations per respondent was 12.4 ± 2.2 (69%, range 34%-98%). Respondents achieved a sensitivity of 68% and a specificity of 70% for recognition of any abnormality. The false-positive and false-negative rates were 30% and 32%, respectively. Based on actual ECG diagnosis, sports participation was accurately permitted in 74% of cases and accurately restricted in 81% of cases. Respondents gave correct sports guidance most commonly in cases of long QT syndrome and myocarditis (98% and 90%, respectively) and least commonly in cases of hypertrophic cardiomyopathy, Wolff-Parkinson-White syndrome, and pulmonary hypertension (80%, 64%, and 38%, respectively). Respondents ordered more follow-up tests than did experts.

Conclusions: Preparticipation screening ECGs are difficult to interpret. Mistakes in ECG interpretation could lead to high rates of inappropriate sports guidance. A consequence of diagnostic error is overuse of ancillary diagnostic tests.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jpeds.2011.05.014DOI Listing
November 2011