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.

EKG screening for Pre-participation Sports Screening (Israel)

J Am Coll Cardiol, 2011; 57:1291-1296

CLINICAL RESEARCH: PRE-PARTICIPATION ATHLETIC SCREENING

Mandatory Electrocardiographic Screening of Athletes to Reduce Their Risk for Sudden Death. Proven Fact or Wishful Thinking?

Arie Steinvil, MD et al.
Tel Aviv University, Tel-Aviv, Israel

Objectives: The purpose of this study was to determine if pre-participation screening of athletes with a strategy including resting and exercise electrocardiography (ECG) reduces their risk for sudden death.

Background: An increasing number of countries mandate pre-participation ECG screening of athletes for the prevention of sudden death. However, the evidence showing that such a strategy actually reduces the risk of sudden death in athletes is limited. We therefore analyzed the impact of the National Sport Law enacted in Israel in 1997—which mandates screening of all athletes with resting ECG and exercise testing—on the incidence of sudden death among competitive athletes.

Methods: We conducted a systematic search of the 2 main newspapers in Israel to determine the yearly number of cardiac arrest events among competitive athletes. The size of the population at risk was retrieved from the Israel Sport Authority and was extrapolated to the changes in population size over time.

Results: There were 24 documented events of sudden death or cardiac arrest events among competitive athletes during the years 1985 through 2009. Eleven occurred before the 1997 legislation and 13 occurred after it. The average yearly incidence of sudden death or cardiac arrest events was 2.6 events per 100,000 athlete-years. The respective averaged yearly incidence during the decade before and the decade after the 1997 legislation was 2.54 and 2.66 events per 100,000 person years, respectively (p = 0.88).

Conclusions: The incidence of sudden death of athletes in our study is within the range reported by others. However, mandatory ECG screening of athletes had no apparent effect on their risk for cardiac arrest.

EKG: Early Repolarization Pattern Review

STATE-OF-THE-ART PAPER
Clinical and Mechanistic Issues in Early Repolarization
Of Normal Variants and Lethal Arrhythmia Syndromes
Begoña Benito, MD, Eduard Guasch, MD, Lena Rivard, MD and Stanley Nattel, MD*
Research Center and Department of Medicine, Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada

J Am Coll Cardiol, 2010; 56:1177-1186

Early repolarization, involving ST-segment elevation and, sometimes, prominent J waves at the QRS-ST junction, has been considered a normal electrocardiographic variant for over 60 years. A growing number of case reports and case-control studies indicate that in some instances, early repolarization patterns are associated with increased risk of idiopathic ventricular fibrillation. Epidemiological evidence indicates a dose effect for the risk of cardiac and sudden death with the extent of J-point elevation. This paper reviews present knowledge regarding the epidemiology, presentation, therapeutic response, and mechanisms characteristic of early repolarization. We highlight major unanswered questions relating to our limited ability to determine which individuals with this common electrocardiographic variant are at risk for sudden death, our incomplete understanding of underlying mechanisms, the inadequate information regarding genetic determinants and therapeutic responses, and the unclear relationship between early repolarization and other conditions involving accelerated repolarization and sudden arrhythmic death such as Brugada and short-QT syndromes. This review paper intends to inform the practicing physician about important clinical issues and to stimulate investigators to address the many unresolved questions in this rapidly evolving field.