Electrocardiographic Early Repolarization

Electrocardiography in athletes: normal and abnormal findings

Many sporting organisations recommend a pre-participation ECG to screen for disorders which predispose to sudden cardiac arrest (SCA). The ability of the ECG to perform accurately is dependent on the ECG criteria used and the experience of the operator. There have been several ECG criteria over the last decade, though these were recently superseded with the publication of the 'International Consensus Criteria for ECG Interpretation in Athletes'. These criteria use the latest evidence to improve specificity while maintaining sensitivity for ECG-detectable pathologies associated with SCA. Accordingly, this review describes the normal, borderline and abnormal ECG findings in an asymptomatic athlete aged 12-35 years.

Relation of Early Repolarization (J Point Elevation) to Mortality in Blacks (from the Jackson Heart Study)

Conflicting data exist regarding the associations of early repolarization (ER) with electrocardiogram (ECG) and clinical outcomes in blacks. We examined the association of ER defined by J point elevation (JPE) and all-cause mortality, and heart failure (HF) hospitalization in blacks in the Jackson Heart Study (JHS) cohort. We included JHS participants with ECGs from the baseline visit coding JPE and excluded participants with paced rhythms or QRS duration ≥120 ms. We compared the cumulative incidence of 10-year all-cause mortality and 8-year HF hospitalization by presence of JPE ≥0.1 mV in any ECG lead at baseline using Kaplan-Meier estimates and multivariable Cox models. Of the 4,978 participants, 1,410 (28%) had JPE at baseline: anterior leads 97.8%, lateral leads 8.3%, and inferior leads 2.9%. Compared with participants without JPE, those with JPE were younger, more likely to be male and current smokers, and less likely to have hypertension. Over a median follow-up of 8 years, there were no significant differences in the cumulative incidence or multivariable-adjusted hazards of all-cause mortality or HF hospitalization in participants with and without JPE in any lead (adjusted hazard ratio 0.97, 95% confidence interval 0.89 to 1.52, and adjusted hazard ratio 1.18, 95% confidence interval 0.9 to 1.54, respectively). Of the 2,523 participants who completed Exam 3 without JPE at baseline, 246 (10%) developed JPE over follow-up. In conclusion, JPE on ECG was not associated with long-term mortality or HF hospitalization in a large prospective black community cohort, suggesting that ER may represent a benign ECG finding in blacks.

J-Wave Syndromes: Electrocardiographic and Clinical Aspects

Early repolarization, Brugada syndrome, and pathologic J waves have been described for decades, but only recently experimental and clinical data have allowed reconciliation of Brugada and Early Repolarization under the common definition of J-wave syndromes. The concept was derived from studies showing, in both conditions, the presence of transmural dispersion of repolarization, localized conduction abnormalities, and abnormal transition between QRS and ST segment on electrocardiogram. Although several clinical studies have addressed the clinical presentation and epidemiology of J-wave syndromes, relevant knowledge gaps exist. Incomplete pathophysiologic understanding and uncertain electrocardiographic definitions limit effective risk stratification. Here, we review the current knowledge and recommendations for diagnosis and clinical management of these arrhythmogenic disorders.

ST elevation: Differential diagnosis and caveats. A comprehensive review to help distinguish ST elevation myocardial infarction from nonischemic etiologies of ST elevation

Prompt diagnosis of acute ST segment elevation myocardial infarction (STEMI) by the initial ECG is important in order to perform an urgent coronary angiography as soon as possible and achieve successful revascularization, therewith improving mortality and morbidity. Several diseases and conditions can mimic an acute myocardial infarction (AMI) but may not benefit from a (percutaneous) revascularization strategy. This narrative clinical review will discuss the ECG features of some of the causes of non-ischemic ST segment elevation to facilitate early recognition, prevent wrongful diagnosis and improve treatment outcomes.

Repetitive-incessant electrical storm triggered by early repolarization

Early repolarization syndrome (ERS) was originally considered a normal variant with benign outcome. However, recent studies have demonstrated that it can be linked to a considerable risk of life-threatening arrhythmias and sudden cardiac death. We report a case with an extraordinary, extremely malignant clinical expression of ERS refractory to all antiarrhythmic drugs including quinidine. This case demonstrates real-time changes of dynamic electrocardiogram (ECG) preceding a polymorphic ventricular tachycardia (VT)-ventricular fibrillation (VF) and possible external factors triggering arrhythmia onset. Implantable cardioverter-defibrillator (ICD) function was terminated 6 months after implantation due to multiple-incessant electrical storm (ES). Catheter ablation was the definite treatment of this malignant entity.

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Normal Ventricular Repolarization and QT Interval: Ionic Background, Modifiers, and Measurements

The QT interval on surface electrocardiogram represents the sum of depolarization and repolarization process of the ventricles. The ventricular recovery process, reflected by ST segment and T wave, mainly depends on the transmembrane outward transport of potassium ions to reestablish the endocellular electronegativity. Outward potassium channels represent a heterogeneous family of ionic carriers, whose global kinetics is modulated by heart rate and autonomic nervous activity. Several cardiac and noncardiac drugs and disease conditions, and several mutations of genes encoding ionic channels, generating distinct genetic channellopathies, may affect the ventricular repolarization, provoke QT interval prolongation and shortening, and increase the susceptibility to ventricular arrhythmias.

Computer-Interpreted Electrocardiograms: Benefits and Limitations

Computerized interpretation of the electrocardiogram (CIE) was introduced to improve the correct interpretation of the electrocardiogram (ECG), facilitating health care decision making and reducing costs. Worldwide, millions of ECGs are recorded annually, with the majority automatically analyzed, followed by an immediate interpretation. Limitations in the diagnostic accuracy of CIE were soon recognized and still persist, despite ongoing improvement in ECG algorithms. Unfortunately, inexperienced physicians ordering the ECG may fail to recognize interpretation mistakes and accept the automated diagnosis without criticism. Clinical mismanagement may result, with the risk of exposing patients to useless investigations or potentially dangerous treatment. Consequently, CIE over-reading and confirmation by an experienced ECG reader are essential and are repeatedly recommended in published reports. Implementation of new ECG knowledge is also important. The current status of automated ECG interpretation is reviewed, with suggestions for improvement.

Ventricular and Supraventricular Ectopy in Subjects With Early Repolarization

Early repolarization (ER) is a common electrocardiographic (ECG) finding that is associated with an increased risk of idiopathic ventricular fibrillation and sudden cardiac death. This study investigated whether the presence of ER is a predictor of ventricular and supraventricular ectopy as a marker for electrical instability. Standard 12-lead electrocardiograms of the first follow-up in the population-based Study of Health in Pomerania (SHIP-1) (n = 3,300, age 20 to 79 years) were analyzed to identify subjects with an ER pattern. Ventricular and supraventricular ectopy was assessed via portable tele-ECG cards recording 2 electrocardiograms daily over the course of 4 weeks. Data of 1,630 subjects (n = 83,833 ECG card recordings, average 51.4 per subject) were analyzed for ventricular and supraventricular ectopy using a standardized automated algorithm. Associations of ER and several forms of arrhythmias were assessed using a 2-sided Fisher's exact test or t test, where appropriate. Overall, prevalence of ER in the SHIP-1 population was 4.8%. Presence of ER was not associated with the occurrence of ventricular and supraventricular arrhythmias (p ≥0.05 for all analyses). Furthermore, subgroup analyzes for ER localization (inferior) and ST-segment morphology (horizontal/descending) did not show any association with arrhythmic events. In conclusion, presence of the ER pattern is not associated with an increased occurrence of ventricular or supraventricular arrhythmias as assessed by serial ECG card recordings in this large population-based sample.

Associations of Sex Hormones With Surface Electrocardiogram J Point Amplitude in Healthy Volunteers

Gender differences in J point height exist. Previous studies suggest male sex hormones mediate effects on cardiovascular disease through myocardial repolarization. Our objective was to assess whether male and female sex hormones are associated with J point amplitude in healthy subjects. We conducted a cross-sectional study of 475 healthy, mixed racial population of men, and premenopausal women (age 33 ± 9 years, 56% male). Baseline J point amplitude (JPA) was obtained from continuous surface electrocardiograms. Plasma testosterone (T), dihydrotestosterone, estrone, 17-estradiol (E2), and sex hormone-binding globulin were measured. A free testosterone index (FTI) was calculated. Multivariate regression analysis stratified by gender and electrocardiographic lead location was used to determine independent predictors of maximum JPA. Regression analysis demonstrated FTI levels were positively associated with JPA in lateral leads (β = +0.01, p <0.05) in men but not in women. Total testosterone was positively associated with anterior electrocardiographic lead JPA in women (β = +0.5, p <0.02), but not in men. E2 was positively associated with inferior lead JPA (β = +1.2, p <0.03) in men but not in women. Total testosterone levels were positively associated with JPA in anterior leads (β = +0.054, p <0.05) in women. Male volunteers in the highest tertile of FTI demonstrated greater lateral JPA compared with the lowest tertile (p <0.05). Women in the highest tertile of FTI demonstrated greater anterior lead JPA compared with the lowest tertile (p <0.05). In conclusion, in a young, healthy population, the female sex hormone E2 and an FTI are independent determinants of JPA in men, whereas T is associated with JPA in women.

A mutation in the CACNA1C gene leads to early repolarization syndrome with incomplete penetrance: A Chinese family study

BACKGROUND

Early repolarization syndrome (ERS) may be a near-Mendelian or an oligogenic disease; however, no direct evidence has been provided to support this theory.

METHODS AND RESULTS

We described a large Chinese family with nocturnal sudden cardiac death induced by ERS in most of the young male adults. One missense mutation (p.Q1916R) was found in the major subunit of the L-type calcium channel gene CACNA1C by the direct sequencing of candidate genes. A concomitant gain-of-function variant in the sodium channel gene SCN5A (p.R1193Q) was found to rescue the phenotype of the female CACNA1C-Q1916R mutation carriers, which led to the incomplete penetrance. The functional studies, via the exogenous expression approach, revealed that the CACNA1C-Q1916R mutation led to a decreasing L-type calcium current and the protein expression defect. The decreased calcium current produced by the mutant channel was improved by isoproterenol but exacerbated by testosterone. The effects of CACNA1C-Q1916R mutation and testosterone on cellular electrophysiology were further confirmed by the human ventricular action potential simulation.

CONCLUSIONS

Our results demonstrated that the loss-of-function CACNA1C-Q1916R mutation contributed to ERS-related sudden cardiac death, and the phenotypic incomplete penetrance was modified by the SCN5A-R1193Q variant and sex. These findings suggest that phenotypes of ERS are modified by multiple genetic factors, which supports the theory that ERS may be an oligogenic disease.

Long-term prognosis associated with early repolarisation pattern in Chinese population with atherosclerotic risk factors

BACKGROUND

Recent evidence has linked early repolarisation pattern (ERP) to sudden cardiac death (SCD) in patients without structural heart disease. However, no studies have clarified the prognostic value of ERP in people at high risk for atherosclerotic heart disease.

METHODS

We prospectively assessed the prognostic significance of ERP on ECGs in a community-based population of 18 231 subjects with atherosclerotic risk factors (49.3% men, mean age 64.0 years). Mean follow-up was 7.6 years. Cox models were used to estimate the hazard ratios (HRs) adjusted for possible confounding factors.

RESULTS

Compared with those without ERP, subjects with ERP had a significantly increased risk of developing SCD (HR 1.91, 95% CI 1.30 to 2.82), death from coronary heart disease (CHD) (HR 1.80, 95% CI 1.45 to 2.22) and death from any cause (HR 1.35, 95% CI 1.22 to 1.50). ERP was not associated with an increased risk of non-sudden CHD death and non-CHD death. ERP with J wave pattern in inferior leads, high amplitude of J wave pattern, notching configuration and horizontal or descending ST segment indicated a higher risk for SCD. ERP was associated with an absolute risk increase of 52.3 additional SCDs per 100 000 person-years in the population at high risk for atherosclerotic heart disease.

CONCLUSIONS

ERP is associated with a significantly increased risk for SCD, CHD death and death from any cause in people with atherosclerotic risk factors. The observed association between ERP and all-cause mortality appears to be driven by an association with CHD death, in particular SCD.