IV Sotalol - Registry study in children

 85 patients

Age range 1 day - 36 yrs)

Treated with IV Sotalol (Average dose 1 mg/kg/dose; Range = 0.5 - 1.8 mg/kg/dose).

Infused 

over a median period of 60 min (Range 30 min - 5 hours).

Successful in 49%, Improved in 30% (Improved = HR decreased to the extent of allowing overdrive atrial pacing).

QTc prolonged >465 ms in 16% (Prolonged >500 ms in 4%).

Conlcusion: Safe as effective.

Successful or Improved in 79%.

Most common dose is 1 mg/kg/dose, infused over 60 min.

Link to reference: Mollory-walton LE at al. JAHA 2022. 

Drug induced Brugada syndrome in Children

Clinical features, device-based management and long-term follow-up.

Conte, G., et al.
JACC 2014;63:2272-9.

Short QT syndrome

J Am Coll Cardiol. 2014 Apr 8;63(13):1300-8. doi: 10.1016/j.jacc.2013.09.078. Epub 2013 Nov 28.

Novel insight into the natural history of short QT syndrome.

Mazzanti A1, Kanthan A1, Monteforte N1, Memmi M1, Bloise R1, Novelli V1, Miceli C1, O'Rourke S2, Borio G1, Zienciuk-Krajka A3, Curcio A1, Surducan AE4,Colombo M4, Napolitano C5, Priori SG6.

Author information

Abstract

OBJECTIVES:

This study intends to gain further insights into the natural history, the yield of familial and genetic screening, and the arrhythmogenic mechanisms in the largest cohort of short QT syndrome (SQTS) patients described so far.

BACKGROUND:

SQTS is a rare genetic disorder associated with life-threatening arrhythmias, and its natural history is incompletely ascertained.

METHODS:

Seventy-three SQTS patients (84% male; age, 26 ± 15 years; corrected QT interval, 329 ± 22 ms) were studied, and 62 were followed for 60 ± 41 months (median, 56 months).

RESULTS:

Cardiac arrest (CA) was the most frequent presenting symptom (40% of probands; range, <1 0.0000001="" 1.3="" 20="" 40="" 41="" 44="" 4="" a="" age="" and="" arrhythmias="" at="" being="" between="" by="" ca.="" ca="" despite="" disease="" familial="" female="" fibrillation="" first="" follow-up="" genetic="" had="" history="" in="" kindreds.="" life="" low="" mainly="" male="" men="" month="" multiple="" observed="" occurred="" occurrence="" occurrences="" of="" only="" onset="" p="" patients="" patterns="" per="" predictor="" predominance="" present="" probability="" profile="" rate="" recurrences="" reproducible="" rest.="" risk="" screening="" superimposable="" that="" the="" to="" two="" ventricular="" was="" were="" with="" year="" years="" yield="">

CONCLUSIONS:

SQTS is highly lethal; CA is often the first manifestation of the disease with a peak incidence in the first year of life. Survivors of CA have a high CA recurrence rate; therefore, implantation of a defibrillator is strongly recommended in this group of patients.

Zoll LifeVest

From http://www.lifevest.zoll.com/medical-professionals/lifevest-overview.asp

Risk Stratification in Brugada Syndrome

Results of PRELUDE (PRogrammed ELectrical stimUllation preDictive valuE) Registry.

SG Priori et al.

JACC 2012;59:37-45.

Study of 247 men (Median age 44 yrs, Range 18-72 yrs)

Results: During a median follow-up of 34 months, 14 arrhythmic events (4.5%) occurred (13 appropriate shocks of the implantable defibrillator, and 1 cardiac arrest). Programmed electrical stimulation performed with a uniform and pre-specified protocol induced ventricular tachyarrhythmias in 40% of patients: arrhythmia inducibility was not a predictor of events at follow-up (9 of 14 events occurred in noninducible patients). History of syncope and spontaneous type I ECG (hazard ratio [HR]: 4.20), ventricular refractory period <200 ms (HR: 3.91), and QRS fragmentation (HR: 4.94) were significant predictors of arrhythmias.

Conclusions: Our data show that VT/VF inducibility is unable to identify high-risk patients, whereas the presence of a spontaneous type I ECG, history of syncope, ventricular effective refractory period <200 ms, and QRS fragmentation seem useful to identify candidates for prophylactic implantable cardioverter defibrillator.

QT interval - normal values during recovery from exercise

CIRCEP.110.961094
Published online before print May 23, 2011

The QT and Corrected QT Interval in Recovery After Exercise in Children

Wouter Rudolph Berger, Robert M. Gow, Suleman Kamberi, Michael Cheung, Katherine Rose Smith and Andrew Mark Davis

Background—Prolongation of the QT interval after exercise can be used to help diagnose Long QT syndrome, especially when the resting QT interval is borderline. The aim of this study was to determine the normal ranges for QT/QTc in the recovery phase after exercise in children.

Methods and Results—Ninety-four volunteer boys and girls aged 8 to less than 17 years, without any history of heart disease underwent exercise testing and had 12 lead ECGS performed in the supine position for 10 minutes of recovery. The QT was measured using a standardized tangent method with the baseline defined as the Q to Q line. The recovery QT was maximally short at 1 minute of recovery in 93/94 individuals, then lengthened and stabilized at 4 to 5 minutes recovery. The recovery QT lengthens as HR decreases in an approximately linear fashion with a mean increase of 15 milliseconds per 10 beat decrease in heart rate. The 98th percentiles for the QTc using the Bazett formula during minutes 4 to 6 in recovery were from 482 msec to 491 msec. There was excellent intra-observer and inter-observer reliability with intra-class correlation coefficients of 0.95 and 0.88 respectively.

Conclusions—There is substantial individual variability of the normal repolarization process in the post-exercise recovery period in children. The study provides a reference for normal responses for similar populations using a specific measurement protocol that can be easily applied.

EKG: J wave vs. J point

Interesting debate is published in JACC Apr 12, 2011 issue. The following two articles debate the issue.

Surawicz B, Macfarlane PW. Inappropriate and confusing electrocardiographic terms. J-wave syndrome and early repolarization. JACC 2011;57:1584-86.

Antzelevitch C, Yan GX, Viskin S. Rationale for the use of the terms J-wave syndromes and Early repolarization. JACC 2011;57:1587-90.

T wave components in LQTS 1

• CIRCEP.110.958827Published online before print April 21, 2011
• Original Article

Detection of Extra-Components of T Wave by Independent Component Analysis in Congenital Long QT Syndrome

1. Hitoshi Horigome,
2. Yasuhiro Ishikawa,
3. Junko Shiono,
4. Mari Iwamoto,
5. Naokata Sumitomo and
6. Masao Yoshinaga

1. ¹ University of Tsukuba, Tsukuba, Ibaraki, Japan;
2. ² Ishikawa Clinic & Toyohashi University of Technology, Toyohashi, Aichi, Japan;
3. ³ Ibaraki Children's Hospital, Mito, Ibaraki, Japan;
4. ⁴ Yokohama City University, Yokohama, Japan;
5. ⁵ Nihon University, School of Medicine, Tokyo, Japan;
6. ⁶ National Hospital Organization Kagoshima Medical Center, Kagoshima, Jap
   hhorigom@md.tsukuba.ac.jp

Abstract

Background—The main EKG criteria for the diagnosis of long QT syndrome (LQTS) include abnormal T wave morphology as well as prolonged QT interval. The T wave in LQTS probably includes additional components of myocardial repolarization process, which is derived from aberrant ion currents. We investigated whether independent component analysis (ICA) can extract such abnormal repolarization component.

Methods and Results—Digital EKG data were obtained as time series from 10 channels using 20 surface electrodes in 22 patients with genetically-confirmed LQTS type 1 (LQT1) and 30 normal subjects. In each case, T wave area was analyzed by radical ICA after noise reduction by the wavelet thresholding method. Furthermore, inverse ICA was applied to determine the origin of each independent component (IC). Radical ICA revealed that a T-wave consisted of four basic ICs in all control subjects, whereas five or more (mostly 6) ICs were identified in all 22 cases of LQT1. The extra ICs, which were not evident in normal subjects, were assumed to contribute to the formation of abnormal T-wave morphology. The extra ICs were identified even in those patients with normal QTc values and those taking β-blockers. Inverse ICA indicated that the additional ICs originate predominantly from the late phase of the T wave of the left ventricle.

Conclusions—Extra ICs appear during repolarization in all LQT1 patients but not in normal subjects. ICA is a potentially useful multivariate statistical method to differentiate LQT1 patients from normal subjects.

Hypothermia and Arrhythmogenesis

Enhanced Dispersion of Repolarization Explains Increased Arrhythmogenesis in Severe Versus Therapeutic Hypothermia

Joseph S. Piktel, MD, et al.

Circulation: Arrhythmia and Electrophysiology. 2011; 4: 79-86

From The Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, Cleveland, OH.

Background— Hypothermia is proarrhythmic, and, as the use of therapeutic hypothermia (TH) increases, it is critically important to understand the electrophysiological effects of hypothermia on cardiac myocytes and arrhythmia substrates. We tested the hypothesis that hypothermia-enhanced transmural dispersion of repolarization (DOR) is a mechanism of arrhythmogenesis in hypothermia. In addition, we investigated whether the degree of hypothermia, the rate of temperature change, and cooling versus rewarming would alter hypothermia-induced arrhythmia substrates.

Methods and Results— Optical action potentials were recorded from cells spanning the transmural wall of canine left ventricular wedge preparations at baseline (36°C), during cooling and during rewarming. Electrophysiological parameters were examined while varying the depth of hypothermia. On cooling to 26°C, DOR increased from 26±4 ms to 93±18 ms (P=0.021); conduction velocity decreased from 35±5 cm/s to 22±5 cm/s (P=0.010). On rewarming to 36°C, DOR remained prolonged, whereas conduction velocity returned to baseline. Conduction block and reentry was observed in all severe hypothermia preparations. Ventricular fibrillation/ventricular tachycardia was seen more during rewarming (4/5) versus cooling (2/6). In TH (n=7), cooling to 32°C mildly increased DOR (31±6 to 50±9, P=0.012), with return to baseline on rewarming and was associated with decreased arrhythmia susceptibility. Increased rate of cooling did not further enhance DOR or arrhythmogenesis.

Conclusions— Hypothermia amplifies DOR and is a mechanism for arrhythmogenesis. DOR is directly dependent on the depth of cooling and rewarming. This provides insight into the clinical observation of a low incidence of arrhythmias in TH and has implications for protocols for the clinical application of TH.

EP: Risk Factors for Recurrent Syncope in LQTS (A negative Study?!)

J Am Coll Cardiol, 2011; 57:941-950

Risk Factors for Recurrent Syncope and Subsequent Fatal or Near-Fatal Events in Children and Adolescents With Long QT Syndrome

Judy F. Liu, MD et al. for International Long QT Syndrome Registry

Objectives: We aimed to identify risk factors for recurrent syncope in children and adolescents with congenital long QT syndrome (LQTS).

Background: Data regarding risk assessment in LQTS after the occurrence of the first syncope episode are limited.

Methods: The Prentice-Williams-Peterson conditional gap time model was used to identify risk factors for recurrent syncope from birth through age 20 years among 1,648 patients from the International Long QT Syndrome Registry.

Results: Multivariate analysis demonstrated that corrected QT interval (QTc) duration (500 ms) was a significant predictor of a first syncope episode (hazard ratio: 2.16), whereas QTc effect was attenuated when the end points of the second, third, and fourth syncope episodes were evaluated (hazard ratios: 1.29, 0.99, 0.90, respectively; p < 0.001 for the null hypothesis that all 4 hazard ratios are identical). A genotype-specific subanalysis showed that during childhood (0 to 12 years), males with LQTS type 1 had the highest rate of a first syncope episode (p = 0.001) but exhibited similar rates of subsequent events as other genotype-sex subsets (p = 0.63). In contrast, in the age range of 13 to 20 years, long QT syndrome type 2 females experienced the highest rate of both first and subsequent syncope events (p < 0.001 and p = 0.01, respectively). Patients who experienced 1 episodes of syncope had a 6- to 12-fold (p < 0.001 for all) increase in the risk of subsequent fatal/near-fatal events independently of QTc duration. Beta-blocker therapy was associated with a significant reduction in the risk of recurrent syncope and subsequent fatal/near-fatal events.

Conclusions: Children and adolescents who present after an episode of syncope should be considered to be at a high risk of the development of subsequent syncope episodes and fatal/near-fatal events regardless of QTc duration.

EP: Do ablation lesions grow in size?

Circulation: Arrhythmia and Electrophysiology 2011

Enlargement of Catheter Ablation Lesions in Infant Hearts with Cryothermal Enlargement of Catheter Ablation Lesions in Infant Hearts with Cryothermal Versus Radiofrequency Energy: An Animal Study

1. Paul Khairy*,
2. Peter G. Guerra,
3. Lena Rivard,
4. Jean-François Tanguay,
5. Evelyn Landry,
6. Marie-Claude Guertin,
7. Laurent Macle,
8. Berndard Thibault,
9. Jean-Claude Tardif,
10. Mario Talajic,
11. Denis Roy and
12. Marc Dubuc

Abstract

Background—Radiofrequency catheter ablation in immature hearts has been associated with marked enlargement of lesions over time, with potential for related late adverse events. It remains unknown whether cryothermal ablation lesions display a similar pattern of growth.

Methods and Results—Ablation lesions (n=384) were performed in 32 infant miniature swine in right and left atria, ventricles, and atrioventricular (AV) grooves preselected by a randomized factorial design devised to compare radiofrequency and cryothermal lesions produced by 7-French 4 mm electrode-tip catheters. Animals were sacrificed acutely or at 1, 6, or 12 months according to the randomization scheme. The miniature swine weighed 8.8±1.2 kg and were 63±13 days of age at time of ablation. The minimum temperature during cryoablation was -79.8±3.4°C and the average temperature during radiofrequency ablation was 54.4±5.5°C. On morphometric analyses, no differences in the rate of growth of ablation lesions were noted between the two energy modalities in atria (P=0.44), ventricles (P=0.57), or AV grooves (P=0.69). Lesion volumes increased 3.3-fold in atria [95% confidence interval (CI) 2.3, 4.3, P=0.001] and 2.2-fold in ventricles [95% CI (1.4, 3.0), P<0.0001], p="0.22)." p="">

Conclusions—Ablation lesions produced by cryothermal energy in immature atrial and ventricular myocardium enlarge to a similar extent to radiofrequency ablation. In contrast, AV groove lesion volumes do not increase significantly with either energy modality.

Innovation: Parental Use of External Defibrillator for Infant with LQTS

Pediatrics 2006:118:e526-e529
Abhay Divekar and Reeni Soni

Congenital long-QT syndrome with 2:1 atrioventricular block presenting in the perinatal period is rare, has a poor prognosis, and leads to high risk for lethal ventricular arrhythmic events. An implantable cardioverter-defibrillator seems to be the most effective treatment in the prevention of arrhythmic sudden cardiac death in patients with long-QT syndrome. Technical limitations and risks associated with implantable cardioverter-defibrillators in asymptomatic infants is considered too great to justify use for primary prophylaxis against sudden cardiac death. In this case report we describe the first successful parental use of an automated external defibrillator prescribed for primary prophylaxis against sudden cardiac death in an infant with long-QT syndrome.

Additional Reading:
T wave morphology in LQTS
Circulation 2000;102:2849-2855
Very useful article to identify genotype based on EKG findings.

Wearable Cardioverter-Defibrillator

Article
JACC 2010;56:194-203

Editorial
JACC 2010;56:204-205

Just a novel idea. Defibrillator vest used in adults. Made by ZOLL. Approved by FDA in 2002. Interesting read. Something to consider in some pediatric patients.