Early repolarization syndrome: a decade of progress

Molecular Pathways and Animal Models of Arrhythmias

Arrhythmias account for over 300,000 annual deaths in the United States, and approximately half of all deaths are associated with heart disease. Mechanisms underlying arrhythmia risk are complex; however, work in humans and animal models over the past 25 years has identified a host of molecular pathways linked with both arrhythmia substrates and triggers. This chapter will focus on select arrhythmia pathways solved by linking human clinical and genetic data with animal models.

Tachycardia dependent early repolarisation pattern in subarachnoid haemorrhage related takotsubo syndrome

We present a case of a patient who suffered subarachnoid haemorrhage (SAH), complicated by takotsubo syndrome, paroxysmal atrial fibrillation and ECG repolarisation abnormality, compatible with Brugada phenocopy. The early repolarisation morphology showed a paradox association with the cardiac cycle length; a relationship not yet documented in SAH. Our observation also sheds light on the genesis of the "spiked helmet" ECG sign.

Association of early repolarization pattern with cardiovascular outcomes in middle-aged population: A cohort study

BACKGROUND

Large cohort studies provide conflicting evidence regarding the prognostic value of early repolarization pattern (ERP) in the general population, complicated by the complex or heterogeneous definitions of ERP applied in different studies.

HYPOTHESIS

We hypothesized that ERP was associated with increased cardiovascular risk with the definition of ERP recommended by the expert consensus statements.

METHODS

A total of 13673 middle-aged subjects from the prospective, population-based Atherosclerosis Risk in Communities (ARIC) study were included in this analysis. Cox models were used to estimate the hazard ratios (HRs) adjusted for possible confounding factors. ERP was defined as ST-segment elevation ≥0.1mV at the end of the QRS or J wave on the QRS downstroke in two or more contiguous leads.

RESULTS

Compared with those without ERP, subjects with ERP had a significantly increased risk of developing sudden cardiac death (SCD) (HR, 1.48; 95% CI, 1.08-2.04) and death from coronary heart disease (CHD) (HR, 1.45; 95% CI, 1.10-1.92) after a median follow-up of 20.1 years. ERP was significantly predictive of SCD in females, whites, younger people, and subjects with relatively low cardiovascular risk. ERP with ST-segment elevation appeared to indicate poor cardiovascular outcomes. ERP was associated with an absolute risk increase of 93.3 additional SCDs per 100 000 person-years.

CONCLUSIONS

Our findings suggest that ERP was an independent predictor of SCD and CHD death in the middle-aged biracial population.

A constant ST segment elevation in leads II, III, AVF: An electrocardiographic, echocardiographic, clinical, exercise test, laboratory and multi-slice computed tomography angiographic study

A constant ST-elevation was more often described in precordial leads. We presented it in leads II, III, AVF in 16 consecutive patients seeking to establish a link between it and clinical, laboratory, echocardiography, exercise test, and multi-slice computed tomography angiography data. Main complaint of these obese middle-age men was angina pectoris (68.75%). They usually had hypertension, dyslipidemia, concentric left ventricular hypertrophy and non-pathological exercise test. Coronary stenosis >50% was only in one case (6.25%). Despite the typical pain and risk factors, the constant ST-elevation in leads II, III, AVF usually was not associated with coronary stenosis.

Diagnostic Approach to Unexplained Cardiac Arrest (from the FIVI-Gen Study)

Unexplained cardiac arrest (UCA) can be caused by low-penetrance genetic disorders. The aim of this cross-sectional study is to assess the usefulness of a new diagnostic protocol: Thirty-five patients were recruited from 9 Spanish centers. Electrocardiogram, echocardiogram, and coronary catheterization were used to rule out electrical or structural heart disease in all subjects. Patients underwent pharmacologic tests with epinephrine and flecainide, followed by assessment of family members using electrocardiogram and echocardiogram, and next-generation genetic sequencing to analyze 126 genes if all the other test results were negative. A firm diagnosis of channelopathy required phenotypic proof of the condition in unmasking tests, the presence of a pathogenic variant consistent with the phenotype observed, and/or co-segregation of the mutation found in a family member's phenotype. A firm diagnosis was made in 18 cases. The diagnoses were 7 Brugada syndrome, 5 catecholaminergic polymorphic ventricular tachycardia, 3 long QT syndrome, 2 early repolarization syndrome, and 1 short QT syndrome. Pharmacologic testing was the most frequent method of diagnosis. In 5 cases, the diagnosis was made based on positive genetic testing without phenotypic alterations. In conclusion, this sequential diagnostic protocol allows diagnoses to be made in approximately half of the UCA cases. These diagnoses are low clinical penetrance channelopathies. If interpreted carefully, genetic tests can be a useful tool for diagnosing UCA without a phenotype.

Prognostic value of automatically detected early repolarization

Early repolarization associated with sudden cardiac death is based on the presence of >1-mm J-point elevations in inferior and/or lateral leads with horizontal and/or downsloping ST segments. Automated electrocardiographic readings of early repolarization (AER) obtained in clinical practice, in contrast, are defined by ST-segment elevation in addition to J-point elevation. Nonetheless, such automated readings may cause alarm. We therefore assessed the prevalence and prognostic significance of AER in 211,920 patients aged 18 to 75 years. The study was performed at a tertiary medical center serving a racially diverse urban population with a large proportion of Hispanics (43%). The first recorded electrocardiogram of each individual from 2000 to 2012 was included. Patients with ventricular paced rhythm or acute coronary syndrome at the time of acquisition were excluded from the analysis. All automated electrocardiographic interpretations were reviewed for accuracy by a board-certified cardiologist. The primary end point was death during a median follow-up of 8.0 ± 2.6 years. AER was present in 3,450 subjects (1.6%). The prevalence varied significantly with race (African-Americans 2.2%, Hispanics 1.5%, and non-Hispanic whites 0.9%, p <0.01) and gender (male 2.4% vs female 0.6%, p <0.001). In a Cox proportional hazards model controlling for age, smoking status, heart rate, QTc, systolic blood pressure, low-density lipoprotein cholesterol, body mass index, and coronary artery disease, there was no significant difference in mortality regardless of race or gender (relative risk 0.98, 95% confidence interval 0.89 to 1.07). This was true even if J waves were present. In conclusion, AER was not associated with an increased risk of death, regardless of race or gender, and should not trigger additional diagnostic testing.