Characterization of early repolarization during ajmaline provocation and exercise tolerance testing Rachel Bastiaenen, MRCP, * Hariharan Raju, MRCP, * Sanjay Sharma, MD, FRCP, *† Michael Papadakis, MRCP, *† Navin Chandra, MRCP, *† Martina Muggenthaler, MRCP, * Malini Govindan, BMed, FRACP, * Velislav N. Batchvarov, MD, * Elijah R. Behr, MD, MRCP * From the *Cardiovascular Research Centre, St George’s University of London, London, UK and y Department of Cardiology, University Hospital Lewisham, London, UK. BACKGROUND Early repolarization (ER) in the inferior electro- cardiogram leads is associated with idiopathic ventricular fibrilla- tion, but the majority of subjects with ER have a benign prognosis. At present, there are no risk stratifiers for asymptomatic ER. OBJECTIVE To examine the response to ajmaline provocation and exercise in potentially high-risk subjects with ER and without a definitive cardiac diagnosis. METHODS Electrocardiographic data were reviewed for ER at baseline and during ajmaline and exercise testing in 229 potentially high-risk patients (mean age 37.7  14.9 years; 55.9% men). ER was defined as J-point elevation in Z2 consecutive leads and stratified by type, territory, J-point height, and ST-segment morphology. RESULTS Baseline ER was present in 26 (11.4%; 19 men) patients. During ajmaline provocation and exercise, there were no new ER changes. ER with rapidly ascending ST-segment and lateral ER consistently diminished. There were 7 patients with persistent ER during ajmaline and/or exercise. They were all men with inferior or inferolateral ER and horizontal/descending ST segment. Those with persistent ER during exercise were more likely to have a history of unexplained syncope than those in whom ER changes diminished (P o .01). Subtle nondiagnostic structural abnormalities were demonstrated in 3 of these patients. CONCLUSIONS ER with horizontal/descending ST-segment mor- phology in the inferior or inferolateral leads that persists during exercise is more common in patients with prior unexplained syncope and may identify patients at higher risk of arrhythmic events. ER that persists during ajmaline provocation and/or exercise may reflect underlying subtle structural abnormalities and should prompt further investigation. KEYWORDS Early repolarization; Idiopathic ventricular fibrillation; Electrocardiogram; Ajmaline provocation; Exercise tolerance testing ABBREVIATIONS BrS ¼ Brugada syndrome; CMRI ¼ cardiac magnetic resonance imaging; ECG ¼ electrocardiogram; ER ¼ early repolarization; ETT ¼ exercise tolerance testing; SADS ¼ sudden arrhythmic death syndrome; SAECG ¼ signal-averaged ECG; SCD ¼ sudden cardiac death; VF ¼ ventricular fibrillation; VT ¼ ventricular tachycardia (Heart Rhythm 2013;10:247–254) I 2013 Heart Rhythm Society. All rights reserved. Introduction Early repolarization (ER) was considered a benign electro- cardiogram (ECG) variant found more commonly in young men and athletes. 1,2 In recent years, it has emerged as a risk marker for sudden cardiac death (SCD). ER with horizontal/ descending ST-segment morphology in the inferior and inferolateral leads has been associated with idiopathic ventricular fibrillation (VF). 3–6 In the general population, inferior ER with horizontal/descending ST segment appears to confer a 3-fold increased risk of arrhythmic death. However, this risk does not become apparent until 10 years after the index ECG. 7,8 ER with rapidly ascending ST segment anterolaterally has been associated with athletic status and African/Afro-Caribbean ethnicity and does not appear to confer the same level of risk. 9,10 At present, there are no clear risk stratifiers and the majority of subjects with ER appear to have a benign prognosis. In addition, although patients with ER syndrome (ER and resuscitated SCD) warrant ICD implantation and may benefit from quinidine therapy, there is no primary prevention strategy for asympto- matic subjects with ER. 11–13 Even the need for such a strategy is unclear. 9 Existing data have demonstrated variable response of ER during ajmaline testing and general loss of ER during treadmill testing. 5,6,14,15 We sought to identify subjects with ER and potentially increased risk of arrhythmic events and systematically examine clinical characteristics and response to ajmaline provocation and exercise in an attempt to tease out features that may associate with risk. Dr Bastiaenen was supported by an educational grant from Boston Scientific. Dr Raju, Dr Papadakis, Dr Chandra, and Dr Muggenthaler were supported by educational grants from Cardiac Risk in the Young. Address reprint requests and correspondence: Elijah R. Behr, MD, MRCP, Cardiovascular Research Centre, St George’s University of London, Cranmer Terrace, London SW17 0RE, UK. E-mail address: ebehr@ sgul.ac.uk. 1547-5271/$-see front matter B 2013 Heart Rhythm Society. All rights reserved. http://dx.doi.org/10.1016/j.hrthm.2012.10.032