Transient and rapid QRS-widening associated with a J-wave pattern predicts impending ventricular fibrillation in experimental myocardial infarction

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.

ECG Markers of Acute Melatonin Treatment in a Porcine Model of Acute Myocardial Ischemia

In myocardial ischemia, melatonin confers antiarrhythmic action, but its electrocardiographic expression is unclear. We aimed to evaluate the effects of melatonin treatment on electrocardiogram (ECG) parameters reflecting major arrhythmogenic factors and to test the association of these parameters with ventricular fibrillation (VF) incidence. Myocardial ischemia was induced by 40 min coronary artery occlusion in 25 anesthetized pigs. After induction of ischemia, 12 and 13 animals were given melatonin or placebo, respectively. Twelve-lead ECGs were recorded and durations of QRS, QT, Tpeak-Tend intervals and extrasystolic burden were measured at baseline and during occlusion. During ischemia, VF episodes clustered into early and delayed phases (<10 and >20 min, respectively), and QRS duration was associated with VF incidence. QT interval and extrasystolic burden did not differ between the groups. The Tpeak-Tend interval was progressively prolonged, and the prolongation was less pronounced in the treated animals. QRS duration increased, demonstrating two maxima (5−10 and 25 min, respectively). In the melatonin group, the earlier maximum was blunted, and VF development in this period was prevented. Thus, acute melatonin treatment prevented excessive prolongation of the QRS and Tpeak-Tend intervals in the porcine myocardial infarction model, and QRS duration can be used for the assessment of antiarrhythmic action of melatonin.

Why Is There an Increased Risk for Sudden Cardiac Death in Patients With Early Repolarization Syndrome?

The last two decades have changed the viewpoint on early repolarization syndrome (ERS). The prevalence of the early repolarization pattern is variable and ranges between 3-24% depending upon age, gender, and criteria used for J-point upliftment from baseline (0.05mV vs. 1 mV). While this pattern was previously linked with a benign result, multiple recent investigations have found a link between early repolarization and Sudden Cardiac Death (SCD) by causing life-threatening arrhythmias like Ventricular tachycardia/Ventricular fibrillation, a condition known as early repolarization syndrome. The syndrome falls under a broader bracket of J wave syndromes, which can be caused by early repolarization or depolarization abnormalities. The characteristics of early repolarization that are considered high risk for Sudden Cardiac Death include the amplitude of J-point upliftment from baseline ( > 0.2 mV), Inferior-lateral location of Early Repolarization pattern, and horizontal and downsloping ST-segment. Patients with symptomatic early repolarisation patterns on ECG are more likely to have repeated cardiac episodes. Implantable Cardioverter-Defibrillator (ICD) implantation and isoproterenol are the recommended treatments in symptomatic patients. On the other hand, asymptomatic patients with early repolarization patterns are prevalent and have a better outcome. Risk categorization is still obscure in asymptomatic early repolarization patterns. This traditional review outlines the known knowledge of pathophysiology behind the increased risk of sudden cardiac death, risk stratification of patients with ERS, and the treatment guidelines for patients with ERS. Further prospective studies are recommended to elucidate the exact mechanism for ventricular arrhythmogenesis in ERS patients and to risk stratifying asymptomatic patients with ERS.

Relationship Between an Ischaemic J Wave Pattern and Ventricular Fibrillation in ST-Elevation Myocardial Infarction Patients

Background

This study determined the ischaemic J wave pattern associated with ventricular fibrillation (VF).

Methods

A total of 262 patients diagnosed with ST-elevation myocardial infarction (STEMI) were recruited from October 2017 to September 2020. All data were collected and analysed, including baseline characteristics, electrocardiogram (ECG), coronary angiography (CAG), and examination outcomes.

Results

There were 193 STEMI patients with J wave elevation but without an ischaemic J wave (NJ group) and 69 patients with an ischaemic J wave; the latter were then subgrouped into early repolarization pattern (ERP; n=62) and Brugada pattern groups (BrP [anteroseptal ERP]; n=7). Univariate and multivariate logistic regression analyses were used to clarify high-risk factors and characteristics of ischaemic J waves. Multivariate logistic regression analysis revealed that an ischaemic J wave (odds ratio [OR], 9.708; 95% CI, 2.570–36.664; P=0.01) independently predicted VF. In the subgroup analysis, BrP (OR, 31.214; 95% CI, 3.949–246.742; P=0.001), slur morphology of the ERP (OR, 8.15; 95% CI, 1.563–42.558; P<0.05), and the number of leads with an ischaemic J wave > 3 (OR, 16.174; 95% CI, 3.064–85.375; P=0.001) were significantly associated with VF occurrence after adjusting for multiple variables.

Conclusion

An ischaemic J wave is an independent risk factor for VF in STEMI patients. BrP, slur morphology, and > 3 leads with an ischaemic J wave could increase the incidence of VF.

Quantifying the spatiotemporal influence of acute myocardial ischemia on volumetric conduction velocity

INTRODUCTION

Acute myocardial ischemia occurs when coronary perfusion to the heart is inadequate, which can perturb the highly organized electrical activation of the heart and can result in adverse cardiac events including sudden cardiac death. Ischemia is known to influence the ST and repolarization phases of the ECG, but it also has a marked effect on propagation (QRS); however, studies investigating propagation during ischemia have been limited.

METHODS

We estimated conduction velocity (CV) and ischemic stress prior to and throughout 20 episodes of experimentally induced ischemia in order to quantify the progression and correlation of volumetric conduction changes during ischemia. To estimate volumetric CV, we 1) reconstructed the activation wavefront; 2) calculated the elementwise gradient to approximate propagation direction; and 3) estimated conduction speed (CS) with an inverse-gradient technique.

RESULTS

We found that acute ischemia induces significant conduction slowing, reducing the global median speed by 20 cm/s. We observed a biphasic response in CS (acceleration then deceleration) early in some ischemic episodes. Furthermore, we noted a high temporal correlation between ST-segment changes and CS slowing; however, when comparing these changes over space, we found only moderate correlation (corr. = 0.60).

DISCUSSION

This study is the first to report volumetric CS changes (acceleration and slowing) during episodes of acute ischemia in the whole heart. We showed that while CS changes progress in a similar time course to ischemic stress (measured by ST-segment shifts), the spatial overlap is complex and variable, showing extreme conduction slowing both in and around regions experiencing severe ischemia.

Melatonin Prevents Early but Not Delayed Ventricular Fibrillation in the Experimental Porcine Model of Acute Ischemia

Antiarrhythmic effects of melatonin have been demonstrated ex vivo and in rodent models, but its action in a clinically relevant large mammalian model remains largely unknown. Objectives of the present study were to evaluate electrophysiological and antiarrhythmic effects of melatonin in a porcine model of acute myocardial infarction. Myocardial ischemia was induced by 40-min coronary occlusion in 25 anesthetized pigs. After ischemia onset, 12 animals received melatonin (4 mg/kg). 48 intramyocardial electrograms were recorded from left ventricular wall and interventricular septum (IVS). In each lead, activation time (AT) and repolarization time (RT) were determined. During ischemia, ATs and dispersion of repolarization (DOR = RTmax − RTmin) increased reaching maximal values by 3–5 and 20–25 min, respectively. Ventricular fibrillation (VF) incidence demonstrated no relations to redox state markers and was associated with increased DOR and delayed ATs (specifically, in an IVS base, an area adjacent to the ischemic zone) (p = 0.031). Melatonin prevented AT increase in the IVS base, (p < 0.001) precluding development of early VF (1–5 min, p = 0.016). VF occurrence in the delayed phase (17–40 min) where DOR was maximal was not modified by melatonin. Thus, melatonin-related enhancement of activation prevented development of early VF in the myocardial infarction model.

Contribution of Depolarization and Repolarization Changes to J-Wave Generation and Ventricular Fibrillation in Ischemia

Background: Activation delay in ischemic myocardium has been found to contribute to J-wave appearance and to predict ventricular fibrillation (VF) in experimental myocardial infarction. However, the role of ischemia-related repolarization abnormalities in J-wave generation remains unclear. Objectives: The objective of our study was to assess a contribution of myocardial repolarization changes to J-wave generation in the body surface ECG and VF in a porcine acute myocardial infarction model. Methods: In 22 anesthetized pigs, myocardial ischemia was induced by occlusion of the left anterior descending coronary artery (LAD, n = 14) and right coronary artery (RCA, n = 8). Body surface ECGs were recorded simultaneously with intramyocardial unipolar electrograms led from flexible electrodes positioned across the left ventricular (LV) wall, interventricular septum (IVS), and right ventricular (RV) wall at apical, middle and basal levels of the ventricles (a total of 48 leads). Local activation times (ATs) and activation-repolarization intervals (ARIs, differences between dV/dt maximum during T-wave and dV/dt minimum during QRS) were measured. Results: J-waves appeared in left precordial leads (in 11 out of 14 animals with LAD occlusion) and right precordial leads (in six out of eight animals with RCA occlusion). During ischemic exposure, ATs prolonged, and the activation delay was associated with J-wave development (OR = 1.108 95% CI 1.072-1.144; p < 0.001) and VF incidence (OR = 1.039 95% CI 1.008-1.072; p = 0.015). ARIs shortened in the ischemic regions (in the IVS under LAD-occlusion and the lateral RV base under RCA-occlusion). The difference between maximal ARI in normal zones and ARI in the ischemic zones (ΔARI) was associated with J-wave appearance (OR = 1.025 95% CI 1.016-1.033, p < 0.001) independently of AT delay in multivariate logistic regression analysis. Conclusions: Both AT delay and increase of ΔARIs contributed to the development of J-wave in body surface ECG. However, only AT delay was associated with VF occurrence.

Prevalence of ECGs Exceeding Thresholds for ST-Segment-Elevation Myocardial Infarction in Apparently Healthy Individuals: The Role of Ethnicity

Background

Early prehospital recognition of critical conditions such as ST‐segment–elevation myocardial infarction (STEMI) has prognostic relevance. Current international electrocardiographic STEMI thresholds are predominantly based on individuals of Western European descent. However, because of ethnic electrocardiographic variability both in health and disease, there is a need to reevaluate diagnostic ST‐segment elevation thresholds for different populations. We hypothesized that fulfillment of ST‐segment elevation thresholds of STEMI criteria (STE‐ECGs) in apparently healthy individuals is ethnicity dependent.

Methods and Results

HELIUS (Healthy Life in an Urban Setting) is a multiethnic cohort study including 10 783 apparently healthy subjects of 6 different ethnicities (African Surinamese, Dutch, Ghanaian, Moroccan, South Asian Surinamese, and Turkish). Prevalence of STE‐ECGs across ethnicities, sexes, and age groups was assessed with respect to the 2 international STEMI thresholds: sex and age specific versus sex specific. Mean prevalence of STE‐ECGs was 2.8% to 3.4% (age/sex‐specific and sex‐specific thresholds, respectively), although with large ethnicity‐dependent variability. Prevalences in Western European Dutch were 2.3% to 3.0%, but excessively higher in young (<40 years) Ghanaian males (21.7%–27.5%) and lowest in older (≥40 years) Turkish females (0.0%). Ethnicity (sub‐Saharan African origin) and other variables (eg, younger age, male sex, high QRS voltages, or anterolateral early repolarization pattern) were positively associated with STE‐ECG occurrence, resulting in subgroups with >45% STE‐ECGs.

Conclusions

The accuracy of diagnostic tests partly relies on background prevalence in healthy individuals. In apparently healthy subjects, there is a highly variable ethnicity‐dependent prevalence of ECGs with ST‐segment elevations exceeding STEMI thresholds. This has potential consequences for STEMI evaluations in individuals who are not of Western European descent, putatively resulting in adverse outcomes with both over‐ and underdiagnosis of STEMI.

Prevalence and Significance of an Early Repolarization Electrocardiographic Pattern and Its Mechanistic Insight Based on Cardiac Magnetic Resonance Imaging in Patients With Acute Myocarditis

BACKGROUND

An early repolarization electrocardiographic (ER-ECG) pattern is caused by various pathophysiological conditions and is reported to be a predictor of life-threatening ventricular tachyarrhythmias. However, little evidence has been reported on the prevalence and significance of the ER-ECG pattern in acute myocarditis. This study aimed to investigate the prevalence and significance of the ER-ECG pattern and its mechanistic insight based on the cardiac magnetic resonance findings in patients with acute myocarditis.

METHODS

Thirty patients (23 men; 39.2±19.1 years) with a diagnosis of acute myocarditis by a clinical presentation between March 2011 and April 2018 were retrospectively evaluated. The patients were divided into 2 groups depending on the presence of an ER-ECG pattern on admission.

RESULTS

Nine cases had an ER-ECG pattern, which was defined as terminal QRS notching or slurring with an amplitude of >0.1 mV in at least 2 inferior or lateral leads (early repolarization [ER] group), whereas the remaining 21 cases had broad ST-segment elevation or pathological Q waves (non-ER group). The cardiac troponin T level was significantly higher in the non-ER group than ER group (3.2±4.3 versus 0.9±1.2 ng/mL; P=0.036). The ECG changes returned to baseline along with the normalization of the cardiac biomarkers. Nine of the 21 non-ER group patients, but none of the 9 ER group patients, developed a fulminant course and lethal ventricular tachyarrhythmias. T2-weighted cardiac magnetic resonance showed high-intensity signals over the entire transmural left ventricle in the non-ER group, whereas they were localized to the left ventricular epicardium in the ER group.

CONCLUSIONS

The ER-ECG pattern in acute myocarditis was transient and reversible and was not associated with a worse prognosis. Inflammation/swelling localized to the left ventricular epicardium because of acute myocarditis might provide a mechanistic insight into the ER-ECG pattern.

Early repolarization pattern on ECG recorded before the acute coronary event does not predict ventricular fibrillation during ST-elevation myocardial infarction

BACKGROUND

Generally considered benign, electrocardiographic (ECG) early repolarization (ER) pattern was claimed to be an indicator of increased susceptibility to ventricular arrhythmias during acute ischemia.

OBJECTIVE

The purpose of this study was to assess in a nonselected population whether ER pattern documented before ST-elevation myocardial infarction (STEMI) is associated with risk of hemodynamically unstable ventricular tachycardia (VT) or ventricular fibrillation (VF) during acute STEMI.

METHODS

For STEMI patients admitted for primary percutaneous coronary intervention from 2007-2010, the latest ECGs recorded before STEMI were exported in digital format. After excluding ECGs with paced rhythm and QRS duration ≥120 ms, the remaining ECGs were processed using the Glasgow algorithm allowing automatic ER detection. The association between ER pattern and VT/VF during the first 48 hours of STEMI was tested using logistic regression.

RESULTS

ECGs recorded before STEMI were available for 1584 patients. Of these patients, 124 did not meet inclusion criteria, leaving 1460 patients available for analysis (age 68 ± 12 years; 67% male). ER pattern was present in 272 patients (18.6%; ER+ group). ER+ and ER- groups did not differ with regard to clinical characteristics. VT/VF during the first 48 hours of STEMI occurred in 19 ER+ (7.0%) and 105 ER- patients (8.8%; P = .398). ER was not associated with any VT/VF (odds ratio [OR] 0.78; 95% confidence interval [CI] 0.47-1.29; P = .324); VT/VF before reperfusion (OR 0.48; 95% CI 0.23-1.001; P = .051); or reperfusion-related VT/VF (OR 1.28; 95% CI 0.55-3.01; P = .569).

CONCLUSION

In a nonselected population of STEMI patients, the ER pattern on ECG recorded before the acute coronary event was not associated with VT/VF during the first 48 hours of STEMI.

Prolongation of The Activation Time in Ischemic Myocardium is Associated with J-wave Generation in ECG and Ventricular Fibrillation

J-wave pattern has been recognized as an arrhythmic risk marker, particularly in myocardial infarction patients. Mechanisms underlying J-wave development in ischemia remain unknown. In myocardial infarction model, we evaluated activation time delay as a prerequisite of J-wave appearance and predictor of ventricular fibrillation. Body surface ECGs and myocardial unipolar electrograms were recorded in 14 anesthetized pigs. 48 intramural leads were positioned across ventricular free walls and interventricular septum. Myocardial ischemia was induced by ligation of the left anterior descending coronary artery and the recordings were done during 40-minute coronary occlusion. The local activation times were determined as instants of dV/dt minimum during QRS complex in unipolar electrograms. During occlusion, ventricular local activation time prolonged in the middle portion of the left ventricular free wall, and basal and middle portions of septum, while J-waves appeared in precordial leads in 11 animals. In logistic regression and ROC curve analyses, activation time delay at a given time-point was associated with J-wave development, and a longer activation time was associated with ventricular fibrillation appearance. In experimental coronary occlusion, activation delay in ischemic myocardium was associated with generation of the J waves in the body surface ECG and predicted ventricular fibrillation.

Depolarization versus repolarization abnormality underlying inferolateral J-wave syndromes: New concepts in sudden cardiac death with apparently normal hearts

Early repolarization indicates a distinct electrocardiographic phenotype affecting the junction between the QRS complex and the ST segment in inferolateral leads (inferolateral J-wave syndromes). It has been considered a benign electrocardiographic variant for decades, but recent clinical studies have demonstrated its arrhythmogenicity in a small subset, supported by experimental studies showing transmural dispersion of repolarization. Here we review the current knowledge and the issues of risk stratification that limit clinical management. In addition, we report on new mapping data of patients refractory to pharmacologic treatment using high-density electrogram mapping at the time of inscription of J wave. These data demonstrate that distinct substrates, delayed depolarization, and abnormal early repolarization underlie inferolateral J-wave syndromes, with significant implications. Finally, based on these data, we propose a new simplified mechanistic classification of sudden cardiac deaths without apparent structural heart disease.

Ischemic QRS prolongation as a predictor of ventricular fibrillation in a canine model

OBJECTIVES

An acute coronary occlusion and its possible subsequent complications is one of the most common causes of death. One such complication is ventricular fibrillation (VF) due to myocardial ischemia. The severity of ischemia is related to the amount of coronary arterial collateral flow. In dog studies collateral flow has also been shown to be associated with QRS prolongation. The aim of this study was to investigate whether ischemic QRS prolongation (IQP) is associated with impending VF in an experimental acute ischemia dog model.

METHODS

Degree of IQP and occurrence of VF were measured in dogs (n = 21) during coronary occlusion for 15 min and also during subsequent reperfusion (experiments conducted in 1984).

RESULTS

There was a significant difference in absolute IQP between dogs which developed VF during reperfusion (47 ± 29 ms, mean ± SD) and those which did not (12 ± 10 ms; p = .001).

CONCLUSIONS

IQP during acute coronary occlusion is associated with reperfusion VF in an experimental dog model and might therefore be a potential predictor of malignant arrhythmias in patients with acute coronary syndrome.

Significance of Coronary Artery Spasm Diagnosis in Patients With Early Repolarization Syndrome

BACKGROUND

Previously described patients with early repolarization syndrome (ERS) may have experienced silent coronary artery spasm (CAS) because the diagnosis of CAS was mainly based on symptoms or coronary angiography findings, without performing a spasm provocation test. This study investigated the significance of CAS diagnosis and evaluated the incidence of silent CAS in patients with possible ERS (ie, idiopathic ventricular fibrillation [VF] and inferolateral J wave).

METHODS AND RESULTS

The study included 34 patients with idiopathic VF and inferolateral J wave. Thirteen patients (38%) were diagnosed as having CAS on the basis of coronary angiography with spasm provocation test (n=8) and documentation of spontaneous ST elevation (n=5). Of the 13 patients with CAS, 5 (38%) did not experience chest symptoms before and during VF, and were diagnosed as having silent CAS. The remaining 21 patients (62%), with a negative provocation test result and absence of chest symptoms, were considered to have ERS. During the 92 months of follow-up, patients with CAS receiving appropriate medical treatment with antianginal drugs showed a favorable outcome. In contrast, 4 of 21 patients with ERS (19%) had VF recurrences. The use of monotherapy or combination therapy, consisting of quinidine, cilostazol, and bepridil, in the 4 patients with ERS, was effective in suppressing VF.

CONCLUSIONS

Approximately 40% of patients with CAS with documented VF and inferolateral J wave did not experience chest symptoms at the first VF, and could have been misdiagnosed as having ERS. The use of the spasm provocation test is considered essential to differentiate patients for optimal medical treatment.

Early Repolarisation - What Should the Clinician Do?

The early repolarisation (ER) pattern is a common ECG finding. Most individuals with the ER pattern are at minimal risk for arrhythmic events. In others, ER increases the arrhythmic risk of underlying cardiac pathology. Rarely ER syndrome will manifest as a primary arrhythmogenic disorder causing ventricular fibrillation (VF). ER syndrome is defined as syncope attributed to ventricular arrhythmias or cardiac arrest attributed to ER following systematic exclusion of other etiologies. Some ECG features associated with ER portend a higher risk. However, clinically useful risk-stratifying tools to identify the asymptomatic patient at high risk are lacking. Patients with asymptomatic ER and no family history of malignant ER should be reassured. All patients with ER should continue to have modifiable cardiac risk factors addressed. Symptomatic patients should be systematically investigated, directed by symptoms.