Early repolarization pattern: its ECG characteristics, arrhythmogeneity and heritability

Novel SCN5A frame‑shift mutation underlying in patient with idiopathic ventricular fibrillation manifested with J wave in inferior lead and prolonged S‑wave in precordial lead

Mutations in the SCN5A gene has been recognized as resulting in a series of life-threatening arrhythmias. However, it also causes idiopathic ventricular fibrillation (IVF) with J wave in inferior leads and prolonged S-wave upstroke in precordial leads, which has not been previously reported. The present study aimed to study the mechanisms of a patient with IVF manifested with J wave in inferior leads and prolonged S-wave upstroke in precordial leads. The electrocardiograms (ECG) of the proband were recorded and genetic testing was conducted. Patch-clamp and immunocytochemical studies were performed in heterologously transfected 293 cells. The VF attacks was documented in a 55-year-old male proband with syncope episodes. 12-lead ECG shown the transient J wave in the inferior leads and prolonged S-wave upstroke in precordial V1-V3 leads in the same timeframe. Genetic analysis revealed a novel 1 base deletion (G) at position 839 in exon 2 in SCN5A gene (C280S*fs61), which causes a severe truncation of the sodium channel. The functional study revealed that in 293 cells transfected with mutant channel, no sodium current could be recorded even though the immunocytochemical experiment confirmed the truncated sodium channel existed in cytosol. The kinetics of the wild-type (WT) channel were not altered when co-transfected with C280S*fs61 mutant which suggested a haploinsufficiency effect of sodium channel in the cells. The present study identified a novel C280Sfs*61 mutation that caused the 'loss of function' of the sodium channel by haploinsufficiency mechanism. The reduced sodium channel function in the heart may cause conduction delay that may underlie the manifestation of J wave and prolonged S-wave upstroke associated with IVF.

Evaluation of cases with early repolarization on electrocardiogram and normal population in terms of laboratory and clinical results

Aim: Early repolarization (ER) is a frequent indication, and it is important to correctly evaluate the effects of its benign and malignant forms in terms of prognosis. It was aimed to compare ER cases with the normal population in terms of multi-vessel disease, bypass and mortality. Material and Method: This study comprised 776 patients aged 18 and older who admitted the emergency department between January 2015 and December 2020. 377 of these patients had ER in the electrocardiogram (ECG), 409 patients had normal ECGs and were added to the study as the control group. Age, gender, multi-vessel disease, by-pass and mortality relations of the patients were evaluated with angiographic findings. Results: The mean age of 786 patients was 50.49±6.82 years, 372 (47.3%) were female, and the age range was 23-66 years (p

Genome-wide association studies of cardiac electrical phenotypes

The genetic basis of cardiac electrical phenotypes has in the last 25 years been the subject of intense investigation. While in the first years, such efforts were dominated by the study of familial arrhythmia syndromes, in recent years, large consortia of investigators have successfully pursued genome-wide association studies (GWAS) for the identification of single-nucleotide polymorphisms that govern inter-individual variability in electrocardiographic parameters in the general population. We here provide a review of GWAS conducted on cardiac electrical phenotypes in the last 14 years and discuss the implications of these discoveries for our understanding of the genetic basis of disease susceptibility and variability in disease severity. Furthermore, we review functional follow-up studies that have been conducted on GWAS loci associated with cardiac electrical phenotypes and highlight the challenges and opportunities offered by such studies.

Idiopathic ventricular fibrillation - Long term prognosis in relation to clinical findings and ECG patterns in a Swedish cohort

BACKGROUND

Idiopathic ventricular fibrillation (IVF) is a rare cause of sudden cardiac arrest which may pose therapeutic and prognostic challenges. To date, the only effective treatment for survivors of cardiac arrest is the insertion of an implantable cardioverter-defibrillator (ICD). We sought to review the long-term outcome of a Swedish cohort with IVF.

METHODS AND RESULTS

Fifty patients with IVF diagnosis between 1988 and 2016 (mean age at index 34.3, 56% male), were followed for a median 13.8 years in this retrospective multicenter observational study. No cardiac mortality was reported. 32% (n = 16) of patients had recurrence of ventricular fibrillation or sustained ventricular tachycardia, requiring ICD therapy, at a median time of 1.9 years (range 0.1-20.3) from the index event. Annual incidence rate of ventricular tachyarrhythmia was 3.1%. Abnormal ECG at baseline did not predict appropriate ICD therapy (p = 0.56). During the follow-up period, 14% (n = 7) patients received a cardiac diagnosis. Follow-up genetic testing was low (26%), however did confirm pathogenic mutations in three cases.

CONCLUSION

Idiopathic VF is a rare diagnosis with a relatively good prognosis provided ICD therapy is initiated. Routine clinical follow-up is recommended due to potential late emerging cardiac pathology. ECG changes are common, but have no prognostic value in determining the risk of ventricular arrhythmias recurrence. Screening for genetic diseases has previously been low, and this calls for improvement, especially since cheaper and more comprehensive genetic panels are now readily available.

Reduced Sodium Current in the Lateral Ventricular Wall Induces Inferolateral J-Waves

BACKGROUND

J-waves in inferolateral leads are associated with a higher risk for idiopathic ventricular fibrillation. We aimed to test potential mechanisms (depolarization or repolarization dependent) responsible for inferolateral J-waves. We hypothesized that inferolateral J-waves can be caused by regional delayed activation of myocardium that is activated late during normal conditions.

METHODS

Computer simulations were performed to evaluate how J-point elevation is influenced by reducing sodium current conductivity (GNa), increasing transient outward current conductivity (Gto), or cellular uncoupling in three predefined ventricular regions (lateral, anterior, or septal). Two pig hearts were Langendorff-perfused with selective perfusion with a sodium channel blocker of lateral or anterior/septal regions. Volume-conducted pseudo-electrocardiograms (ECG) were recorded to detect the presence of J-waves. Epicardial unipolar electrograms were simultaneously recorded to obtain activation times (AT).

RESULTS

Simulation data showed that conduction slowing, caused by reduced sodium current, in lateral, but not in other regions induced inferolateral J-waves. An increase in transient outward potassium current or cellular uncoupling in the lateral zone elicited slight J-point elevations which did not meet J-wave criteria. Additional conduction slowing in the entire heart attenuated J-waves and J-point elevations on the ECG, because of masking by the QRS. Experimental data confirmed that conduction slowing attributed to sodium channel blockade in the left lateral but not in the anterior/septal ventricular region induced inferolateral J-waves. J-waves coincided with the delayed activation.

CONCLUSION

Reduced sodium current in the left lateral ventricular myocardium can cause inferolateral J-waves on the ECG.

Evaluation of left ventricular myocardial deformation parameters in individuals with electrocardiographic early repolarization pattern

OBJECTIVE

Although an early repolarization (ER) pattern was considered to be a benign electrocardiographic variant, several studies have shown that it is associated with an increased risk of idiopathic ventricular fibrillation and death. The aim of the present study was to determine whether there is any abnormality in myocardial deformation parameters (strain, strain rate, rotation, and twist) of the left ventricle obtained by speckletracking echocardiography (STE) in subjects with ER pattern.

METHODS

There were two groups in this prospective case-control study. The first group consisted of subjects with ER pattern (n=35). The other group was control without ER pattern (n=25). Subjects with poor echocardiographic image quality and history of cardiovascular, pulmonary, systemic, or metabolic disease were excluded from the study. For STE of the left ventricle, two-dimensional images from apical long-axis, twochamber, and four-chamber views and from parasternal short-axis views were obtained.

RESULTS

We did not observe significant differences between the groups for left ventricular (LV) longitudinal deformation parameters, rotation, and twist. When LV circumferential deformation parameters were analyzed, early diastolic strain rate value at the level of apex was higher in subjects with ER pattern (2.3±0.7 s-1 vs. 1.9±0.4 s-1, p=0.01). Among LV radial deformation parameters, only peak strain (42.5±16.1% in the ER group vs. 56.9±21.1% in controls, p=0.004) and early diastolic strain rate (-2.0±0.7 s-1 in the ER group vs. -2.3±0.7 s-1 in controls, p=0.03) values at the level of papillary muscle were different.

CONCLUSION

In subjects with ER pattern, LV myocardial deformation evaluated by STE is normal with a few regional exceptions. STE does not provide much information about risk stratification of these subjects.