Elsevier

Heart Rhythm

Volume 12, Issue 7, July 2015, Pages 1576-1583
Heart Rhythm

Early repolarization patterns associated with increased arrhythmic risk are common in young non-Caucasian Australian males and not influenced by athletic status

https://doi.org/10.1016/j.hrthm.2015.03.060Get rights and content

Background

Early repolarization (ER) with a horizontal ST segment (ST-h) and high-amplitude J waves in the inferior leads is associated with an increased risk of cardiac arrhythmic death. The effect of ethnicity and athletic status on this increased-risk ER pattern has not been established. Aboriginal Australian/Torres Strait Islander and Pacific Islander/Maori (non-Caucasian [non-C]) subjects are well represented in Australian sport; however, the patterns and prevalence of ER in these populations are unknown.

Objective

The purpose of this study was to assess the prevalence and effect of athletic activity on ER patterns in young non-C and Caucasian (C) subjects.

Methods

Twelve-lead ECGs of 726 male athletes (23.8% non-C) and 170 male controls (45.9% non-C) aged 16–40 years were analyzed for the presence of ER, defined as J-point elevation (J wave, QRS slur, or discrete ST elevation) ≥0.1 mV in ≥2 inferior (II, III, aVF) or lateral (I, aVL,V4–V6) leads. ST morphology was coded as horizontal (ST-h) or ascending (ST-a). “Increased-risk ER” was defined as inferior ER with ST-h and J waves >2 mV.

Results

Regardless of athletic status, ER and increased-risk ER were more prevalent in non-C than in C subjects (53.8% vs 32% and 7.6% vs 1.2%, respectively, P <.0001). Whereas lower heart rate, larger QRS voltage, and shorter QRS duration were predictors of ER, non-C ethnicity was the only independent predictor of increased-risk ER (odds ratio 17.621, 95% confidence interval 4.98–62.346, P < .0001).

Conclusion

ER patterns associated with increased arrhythmic risk are more common in young non-C than C subjects and were not influenced by athletic status. The long-term clinical significance of ER in these populations is yet to be determined.

Introduction

Early repolarization (ER) is generally considered a normal finding in young athletic individuals. The most common description of ER in athletes is J-point elevation with an associated ascending ST segment (ST-a) in the anterolateral ECG leads. The benign nature of this pattern has been confirmed in several studies.1, 2, 3 However, in more recent years it has become clear that not all patterns of ER are the same. Since 2008 when Haissaguerre et al4 described a high prevalence of prominent J waves or QRS slurs in the inferolateral ECG leads in survivors of sudden cardiac arrest due to idiopathic ventricular fibrillation, a series of studies have confirmed an association with idiopathic ventricular fibrillation, as well as an increased risk of atrial and ventricular tachyarrhythmias and death in the context of acute myocardial ischemia (AMI).4, 5, 6, 7, 8, 9, 10 The highest arrhythmic risk has been associated with inferior ER with a horizontal ST segment (ST-h) and high-amplitude (>2 mV) J waves.11, 12, 13 The prevalence of this pattern in young athletic populations and the effect of athletic training are unclear, as most studies focusing on athletes have not considered ST-segment morphology and have lacked age-matched, nonathletic (NA) controls (most control groups consist of middle-aged subjects).3, 7, 12 Furthermore, descriptions of the patterns and prevalence of ER in young athletic populations of ethnic backgrounds other than African American or Caucasian are lacking.

Approximately 11% of the professional male players in the Australian Football League are of Aboriginal Australian/Torres Strait Islander heritage and up to 30% of professional male players in rugby football codes are of Pacific Islander or Maori heritage, yet we have no data on the patterns and prevalence of ECG patterns in these populations, in whom cardiac mortality related to premature coronary disease far exceeds that of their nonindigenous counterparts.14, 15 Thus, the aim of this study was to determine if the patterns and prevalence of ER in young subjects of Aboriginal Australian/Torres Strait Islander and Pacific Islander or Maori heritage (non-Caucasian [non-C]) may differ from Caucasians (C), and whether athletic training may affect these patterns.

Section snippets

Study population

De-identified ECGs of 1306 consecutive elite athletes aged 16–35 years who underwent preparticipation cardiac screening inclusive of an ECG between June 2011 and December 2013 were analyzed. Our study methods have been described in detail elsewhere.16, 17 All subjects provided written informed consent, and ethics approval was obtained from the Human Research and Ethics Committee at St. Vincent’s Hospital, Melbourne, and the Australian Institute of Sport, Canberra. The gender differences in ER

Subject characteristics

Table 1 summarizes the demographic and baseline ECG characteristics of all subjects. Compared to C-A, non-C–A had a slightly larger body surface area and higher resting heart rate but similar age, QRSd, QRS axis, QTc with Bazett correction, and LVH scores. Both athletic groups, on average, were younger and had lower resting heart rates than NA. Similar to the differences seen in the athlete groups, non-C–NA had a larger body surface area and a higher resting heart rate than C–NA.

Patterns and prevalence of ER in non-C–A vs C-A

Table 2 details

Discussion

This is the first study to describe the ECG findings and patterns of ER in subjects of Aboriginal Australian/Torres Strait Islander and Pacific Islander/Maori heritage. We found that these populations demonstrated a greater prevalence of ER compared to Caucasians, including patterns that have been associated with increased arrhythmic risk, namely, inferior ER with a horizontal ST segment and high-amplitude J waves. In contrast to prior studies, we found no association between ER prevalence and

Conclusion

We demonstrated that patterns of ER associated with increased arrhythmic risk were very common in subjects of Aboriginal Australian/Torres Strait Islander and Pacific Islander or Maori heritage and were not influenced by athletic training or ECG parameters typically associated with so-called benign ER patterns. Given the growing evidence that increased-risk ER patterns may have a heritable basis, the ethnic variations in the patterns and prevalence of ER we described are of interest. However,

Acknowledgements

We thanks Professor Gillian Whalley, Dr. Philippa Cross, and Dr. James Aoina for generous assistance with ECG collection.

References (37)

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Dr. Brosnan is the recipient of a National Health and Medical Research Council (NHMRC) PhD scholarship. Dr. LaGerche is the recipient of a NHMRC Career Development Fellowship and NHF Future Leader Fellowship. Dr. Kumar is the recipient of a Neil Hamilton Fairley Overseas Research Scholarship co-funded by the National Heart Foundation of Australia and NHMRC. Dr. Kalman is the recipient of an NHMRC practitioner fellowship.

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