Acute myocardial ischemia: cellular mechanisms underlying ST segment elevation

Myocardial ischemia simulation based on a multi-scale heart electrophysiology model

BACKGROUND

Myocardial ischemia, caused by insufficient myocardial blood supply, is a leading cause of human death worldwide. Therefore, it is crucial to prioritize the prevention and treatment of this condition. Mathematical modeling is a powerful technique for studying heart diseases.

OBJECTIVE

The aim of this study was to discuss the quantitative relationship between extracellular potassium concentration and the degree of myocardial ischemia directly related to it.

METHODS

A human cardiac electrophysiological multiscale model was developed to calculate action potentials of all cells simultaneously, enhancing efficiency over traditional reaction-diffusion models.

RESULTS

Contrary to the commonly held view that myocardial ischemia is caused by an increase in extracellular potassium concentration, our simulation results indicate that level 1 ischemia is associated with a decrease in extracellular potassium concentration.

CONCLUSION

This unusual finding provides a new perspective on the mechanisms underlying myocardial ischemia and has the potential to lead to the development of new diagnostic and treatment strategies.

Time-Warping Analysis of the T-Wave Peak-to-End Interval to Quantify Ventricular Repolarization Dispersion During Ischemia

Variations in the dispersion of ventricular repolarization can be quantified by T-wave time-warping based index, dw. However, the early phase of the T-wave can be affected by ST-segment changes during ischemia. We hypothesized that restricting dw to the T-wave peak-to-end ( Tpe) would circumvent this limitation while still quantifying variations in repolarization dispersion. A total of 101 ECG recordings from patients undergoing coronary occlusion, together with their control recordings, were analyzed. A series of dw values was calculated by quantifying the Tpe morphological variations between the T-waves at different occlusion stages and a baseline T-wave. We introduced a normalized version of dw, Rd, reflecting variations of dw during occlusion relative to control recordings ( Rd = 1 corresponds to the same level of variation). The dw series followed a gradually increasing trend with occlusion time, reaching median [range] Rd values of 9.44 [1.01, 80.74] at the occlusion end. Rd at occlusion end was significantly higher than threshold values of 1, 2, 5, and 10 in 94.1%, 85.11%, 64.4% and 48.5% of patients, respectively. The spatial lead-wise analysis of dw showed distinct distributions depending on the occluded artery, suggesting a relation with the ischemia location. The relative variation R with ischemia of index dw (9.4) is greater than that of the T-wave amplitude (7.7), Tpe interval (2.7) and T-wave width (3.0). In conclusion, dw tracks ischemic-induced variations in repolarization dispersion in a more robust manner than classical indexes, avoiding the impact of ST segment elevation/depression or early T-wave distortions, thus warranting further clinical studies.

Regional beat-to-beat variability of repolarization increases during ischemia and predicts imminent arrhythmias in a pig model of myocardial infarction

Ventricular arrhythmia (VT/VF) can complicate acute myocardial ischemia (AMI). Regional instability of repolarization during AMI contributes to the substrate for VT/VF. Beat-to-beat variability of repolarization (BVR), a measure of repolarization lability increases during AMI. We hypothesized that its surge precedes VT/VF. We studied the spatial and temporal changes in BVR in relation to VT/VF during AMI. In 24 pigs, BVR was quantified on 12-lead electrocardiogram recorded at a sampling rate of 1 kHz. AMI was induced in 16 pigs by percutaneous coronary artery occlusion (MI), whereas 8 underwent sham operation (sham). Changes in BVR were assessed at 5 min after occlusion, 5 and 1 min pre-VF in animals that developed VF, and matched time points in pigs without VF. Serum troponin and ST deviation were measured. After 1 mo, magnetic resonance imaging and VT induction by programmed electrical stimulation were performed. During AMI, BVR increased significantly in inferior-lateral leads correlating with ST deviation and troponin increase. BVR was maximal 1 min pre-VF (3.78 ± 1.36 vs. 5 min pre-VF, 1.67 ± 1.56, P < 0.0001). After 1 mo, BVR was higher in MI than in sham and correlated with the infarct size (1.43 ± 0.50 vs. 0.57 ± 0.30, P = 0.009). VT was inducible in all MI animals and the ease of induction correlated with BVR. BVR increased during AMI and temporal BVR changes predicted imminent VT/VF, supporting a possible role in monitoring and early warning systems. BVR correlated to arrhythmia vulnerability suggesting utility in risk stratification post-AMI.NEW & NOTEWORTHY The key finding of this study is that BVR increases during AMI and surges before ventricular arrhythmia onset. This suggests that monitoring BVR may be useful for monitoring the risk of VF during and after AMI in the coronary care unit settings. Beyond this, monitoring BVR may have value in cardiac implantable devices or wearables.

Non-ST-segment elevation myocardial infarction with non-obstructive coronary arteries due to a type-A thymoma: A case report

Introduction

Myocardial infarction with non-obstructive coronary arteries (MINOCA) has become an increasingly recognized subgroup in patients with acute myocardial infarction, with a recent cohort study reporting a prevalence of 8.8%. This report describes a patient who presented with non-ST-segment elevation myocardial infarction (NSTEMI) due to an incidental anterior mediastinal mass.

Case presentation

An 80-year-old woman presented to our emergency department with a chief complaint of progressive shortness of breath associated with retrosternal chest pain for one day duration. Computed tomography (CT) angiogram of the chest was conducted, which revealed an anterior mediastinal mass. Upon admission, the patient developed an acute episode of recurrent severe chest pain, which was diagnosed as an NSTEMI. Emergent cardiac catheterization was performed because of unstable vital signs; however, the results showed no evidence of atherosclerotic changes in the major coronary arteries, compatible with the diagnosis of MINOCA. The mediastinal mass was later confirmed to be a type A thymoma on CT-guided biopsy.

Conclusion

Myocardial infarction in patent coronary arteries due to an anterior mediastinal mass is rare. Further studies are needed to standardize the diagnosis and management protocols for the potential etiologies of MINOCA.

Abnormal myocardial activation as a cause of ST elevation: A study using Precordial Bipolar Leads (PBL)

OBJECTIVES

The purpose of the study was to describe the ischemic changes occurring during percutaneous transluminal coronary angioplasty (PTCA) using a new method based on Precordial Bipolar Leads (PBL) and Precordial Unipolar Leads (PUL).

BACKGROUND

Ischemic ECG changes have been attributed to both systolic and diastolic injury currents. The relation between ST segment shift and QRS changes is unclear and there is discussion about its significance.

METHODS

Twelve-lead electrocardiograms (ECGs) were performed in 16 patients before PTCA balloon inflation and immediately after balloon deflation in the proximal left anterior descending coronary artery (LAD). Also, ECG data was used to generate V2-V1 PBL, average V1+V2 lead and the correspondent loop in order to explore ECG and spatial vector changes.

RESULTS

1) The V2-V1 vs. Average V1+V2 loop rotation changed from counter clockwise (CCW) to clockwise (CW) in 14/15 patients (93%). 2) In 12/16 patients (75%), there was an abrupt change of QRS vector direction, producing a "folding" of the loop. In 10 of these cases, the change occurred between 32 and 49 milliseconds after the QRS initiation. 3) In 3/16 patients the final part of the loop was "transported", without folding, to the turning point. 4) The "folding" of the loop changed the direction of the final QRS forces and the J point and ST segment were displaced to the left and forward. 5) For this reason, repolarization began from an abnormal anterior location.

CONCLUSIONS

1) Ischemic changes in QRS loop have a cornerstone point in which the whole loop changes. 2) Once the loop has changed its direction, there are no major modifications in the loop development but the forces do not aim anymore to the isoelectric point. 3) Alterations of myocardial activation appear to be responsible of ST elevation in hyperacute ischemia.

Osteomyelitis of the Cervical Spine Presenting as Acute ST-Segment Elevation

Acute ST-segment elevation (STE) on electrocardiogram (EKG) is very frequently associated with myocardial infarction, which requires prompt diagnosis and treatment. However, there are multiple other causes of acute STE, both cardiac and noncardiac. Here we describe a unique case of acute inferior and lateral STE caused by osteomyelitis and abscess of the lower cervical vertebrae.

The Spiked Helmet Sign Predicting a Poor Outcome in a Patient with Non-Myocardial Infarction ST-Segment Elevation

Spiked helmet sign is a novel electrocardiogram marker that reflects a poor prognosis, and may mimic myocardial infarction, especially in patients with an acute alteration of mental status or out-of-hospital cardiac arrest. In cases where a spiked helmet sign is missed, there may be a delay in surgical intervention for the underlying conditions because of unnecessary cardiac catheterization. In addition, antiplatelet agents for acute coronary syndrome in such cases can lead to catastrophic complications. Therefore, early recognition of spiked helmet sign is useful for timely correction of the underlying disease and prevention of poor outcomes. Herein, we describe a rare case of a patient with internal bleeding and subarachnoid hemorrhage presenting with spiked helmet sign on an electrocardiogram.

Brugada syndrome

Brugada syndrome (BrS) is an inherited cardiac arrhythmia syndrome that causes a heightened risk for ventricular tachyarrhythmias and sudden cardiac death. BrS is characterised by a coved ST-segment elevation in right precordial leads. The prevalence is estimated to range between 1 in 5,000 to 1 in 2,000 in different populations, with the highest being in Southeast Asia and in males. More than 18 genes associated with BrS have been discovered and recent evidence has suggested a complex polygenic mode of inheritance with multiple common and rare genetic variants acting in concert to produce the BrS phenotype. Diagnosis of BrS in patients currently relies on presentation with a type-1 Brugada pattern on ECG either spontaneously or following a drug provocation test using a sodium channel blocker. Risk assessment in patients diagnosed with BrS is controversial, especially with regard to the predictive value of programmed electrical stimulation and novel ECG parameters, such as QRS fragmentation. The first line of BrS therapy remains an implantable cardioverter defibrillator (ICD), although radiofrequency catheter ablation has been shown to be an effective option in patients with contraindications for an ICD. True BrS can be unmasked on ECG in susceptible individuals by monitoring factors such as fever, and this has been recently evident in several patients infected with the 2019 novel coronavirus (COVID-19). Aggressive antipyretic therapy and regular ECG monitoring until fever resolves are current recommendations to help reduce the arrhythmic risk in these COVID-19 patients. In this review, we summarise the current knowledge on the epidemiology, pathophysiology, genetics, clinical diagnosis, risk stratification and treatment of patients with BrS, with special emphasis on COVID-19 comorbidity.

[Detection of ECG alterations typical for myocardial ischemia : New methods 2021]

BACKGROUND

The electrocardiogram (ECG) represents an essential diagnostic tool in cardiology and beyond. Classical ECG devices enable the registration of up to 12 leads, whereas modern ECG systems enable additional leads even with a reduced number of electrodes. Additionally, "smart" devices even enable patients to record an ECG at home.

OBJECTIVE

Evaluation of a potential additional benefit of using various modern ECG systems for the detection of ECG alterations typical for myocardial ischemia.

MATERIAL AND METHODS

Presentation of various signs of ischemia in the ECG according to the latest guidelines. Demonstration of modern ECG systems and their potential advantage in the detection of signs of ischemia in the ECG based on current study results.

RESULTS

Modern ECG systems with vector-based electrocardiography can facilitate and optimize the detection of ischemic ECG alterations. Smart nonvector-based devices for patients are primarily useful for detection of arrhythmias and do not replace the 12-lead ECG for detection of ischemia, even though they can be useful for documentation of temporary ECG alterations also within the ST-segment.

CONCLUSION

The ECG systems based on vector electrocardiography can improve the detection of ECG alterations typical for ischemia compared to the conventional 12-lead ECG.

Cognition and progress of de Winter electrocardiogram pattern

The de Winter electrocardiogram pattern is an acute ST-segment elevation myocardial infarction equivalent, however this specific electrocardiogram change is easily ignored by clinicians. The de Winter electrocardiogram pattern in patients with acute chest pain mostly indicates sub-complete or complete occlusion of the left anterior descending or the diagonal branch. Patients with acute chest pain and such electrocardiographic finding should undergo emergency coronary angiography immediately to determine the coronary condition, and reperfusion therapy should be performed as soon as possible to reduce the incidence of adverse cardiovascular events.

Variant Angina with Spontaneously Documented Ischemia- and Tachycardia-induced "Lambda" Waves

In a patient with variant angina of the proximal left anterior descending coronary artery, myocardial ischemia changed the QRS-ST-T configurations without J-waves into those resembling "lambda" waves at maximal ST-segment elevation, and couplets or triplets of supraventricular extrasystole (SVE) changed the ischemia-induced "lambda" waves into QRS-ST-T configurations resembling a "tombstone" morphology or "monophasic QRS-ST complex." At the resolution phase of coronary spasm, the QRS-ST-T configurations returned to those without J-waves and were changed by SVE into "lambda" waves. Interestingly, neither ischemia- nor SVE-induced "lambda" waves or SVE-induced "tombstone" morphology or "monophasic QRS-ST complex" were complicated by ventricular tachyarrhythmia.

Myocardial Infarction with and without ST-segment Elevation: a Contemporary Reappraisal of Similarities and Differences

Understanding the similarities and differences between myocardial infarction with or without ST-segment elevation is an essential step for proper patients' management in current practice. Both syndromes are caused by critical stenosis or total occlusion of coronary arteries (mostly due to thrombosis on atherosclerotic plaque), and manifest with a similar clinical presentation. Recent epidemiologic studies show that the relative incidence of ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation myocardial infarction (NSTEMI) moves in an opposite fashion (decreasing and increasing respectively), with a prognosis that is worse at short-term follow-up for STEMI but comparable at long-term. Current management differs, as for STEMIs, immediate reperfusion is recommended, while for NSTEMIs, risk stratification is mandatory in order to stratify patients' risk, and then decide the timing for coronary angiography. Periprocedural and technical aspects of the interventional management, as well as antithrombotic medications, are for the most similarly implemented in the two types of MI, with routine radial access, DES implant, and novel P2Y12 inhibitors representing the standard of care in both cases. The following review article aims to compare the two types of MI, with and without persistent STsegment elevation. The main purpose is to explore their similarities and differences and address areas of uncertainty with regards to clinical presentation, therapeutic management, and prognosis. The identification of high-risk NSTEMI patients is important as they may require an individualised approach that can substantially overlap with current STEMI recommendations, and their mortality remains high if their management is delayed.

The Heart in Diabetic Ketoacidosis: A Narrative Review Focusing on the Acute Cardiac Effects and Electrocardiographic Abnormalities

Diabetic ketoacidosis (DKA) is a serious complication of diabetes mellitus. Hyperglycemia, acidosis, and electrolyte imbalances can directly affect the heart by inducing toxicity, impairing myocardial blood flow, autonomic dysfunction, and altering activation and conduction of electrical impulses throughout the heart, increasing the risk of arrhythmias and ischemia. The electrocardiogram is useful in monitoring patients during and after an episode of DKA, as it allows the detection of arrhythmias and guides metabolic correction. Unfortunately, reports on electrocardiographic abnormalities in patients with DKA are lacking. We found two electrocardiographic patterns that are frequently reported in the literature: a pseudo-myocardial infarction and a Brugada Phenocopy. Both are associated with DKA metabolic anomalies and they resolve after treatment. Because of their clinical relevance and the challenge they represent for clinicians, we analyzed the clinical characteristics of these patients and the mechanisms involved in these electrocardiographic findings.

Degree of ST-segment elevation in patients with STEMI reflects the acute ischemic burden and the salvage potential

BACKGROUND

ST-segment elevation myocardial infarction (STEMI) is clinically diagnosed by significant ST-segment elevation (STE) in the electrocardiogram (ECG). The importance of the sum of significant ST-segment elevation (∑STE) before primary percutaneous coronary intervention (PPCI) - considered an indicator of the degree of ischemia - is sparse. We evaluated the association of ∑STE before PPCI with respect to area at risk, infarct size and myocardial salvage.

METHODS

A total of 503 patients with STEMI and available cardiac magnetic resonance (CMR) were included. CMR was performed at day 1 (interquartile range [IQR], 1-1) and at follow-up at day 92 (IQR, 88-96). The ECG before PPCI with the most prominent STE was used for analysis.

RESULTS

∑STE divided into quartiles were progressive linearly associated with area at risk (p < 0.001), final infarct size (p < 0.001) and extent of microvascular obstruction (p < 0.001) and inverse linearly associated with final myocardial salvage (p < 0.001). Similar results were found for linear regression analyses. However, ∑STE was not associated with final myocardial salvage in patients with pre-PCI TIMI (thrombolysis in myocardial infarction) flow 0/1 (p = 0.24) in contrast to patients with pre-PCI TIMI flow 2/3 (p ≤ 0.001).

CONCLUSION

In patients with STEMI presenting within 12 h of symptom onset, the degree of STE in the ECG before PPCI is a marker of the extent of myocardium at risk that in turn affects the infarct size in patients with pre-PCI TIMI flow 0/1, whereas the degree of STE in patients with pre-PCI TIMI flow 2/3 is a marker of the extent of the myocardium at risk as well as myocardial salvage - both affecting the myocardial damage.

Ionic mechanisms of ST segment elevation in electrocardiogram during acute myocardial infarction

ST elevation on an electrocardiogram is a hallmark of acute transmural ischemia. However, the underlying mechanism remains unclear. We hypothesized that high ischemic sensitivities of epicardial adenosine triphosphate-sensitive potassium (IKATP) and sodium (INa) currents play key roles in the genesis of ST elevation. Using a multi-scale heart simulation under moderately ischemic conditions, transmural heterogeneities of IKATP and INa created a transmural gradient, opposite to that observed in subendocardial injury, leading to ST elevation. These heterogeneities also contributed to the genesis of hyper-acute T waves under mildly ischemic conditions. By contrast, under severely ischemic conditions, although action potentials were suppressed transmurally, the potential gradient at the boundary between the ischemic and normal regions caused ST elevation without a contribution from transmural heterogeneity. Thus, transmural heterogeneities of ion channel properties may contribute to the genesis of ST-T changes during mild or moderate transmural ischemia, while ST elevation may be induced without the contribution of heterogeneity under severe ischemic conditions.

Brugada phenocopy following coronary artery bypass graft surgery

A 71-year old male with a history of inferior myocardial infarction and hypertension underwent coronary artery bypass graft (CABG) surgery. He had no family or personal history of syncope, sudden cardiac death or Brugada syndrome. A series of twelve-lead electrocardiograms showed type 1 and type 2 Brugada ECG patterns after procedure, but resolution of ST segment changes to five days later. The electrophysiological mechanisms underlying these changes will be discussed.

Transient appearance of Brugada-like Type 1 electrocardiogram pattern immediately after biphasic synchronized electrical cardioversion for atrial fibrillation: a case series

Background

ST-segment deviation post-electrical cardioversion is a common finding amongst a significant number of patients. However, the mechanism by which this phenomenon occurs and its clinical implications are not fully understood.

Case summary

Four patients presented to our department with complaints of palpitations. They were found to have atrial fibrillation and were cardioverted using a synchronized direct current shock at 200 J. However, their telemetry immediately after the shock showed transiently an ST-segment elevation resembling Brugada Type 1 pattern. All telemetries normalized within 6 s from cardioversion.

Discussion

Through this report, we aim to raise mild concern about a possible safety issue related to synchronized electrical cardioversion with electrodes positioned in an anteroposterior fashion. Also, we try to give a pathophysiological explanation to this finding on the base of the knowledge accumulated through the years on Brugada syndrome.

ECG analysis in patients with acute coronary syndrome undergoing invasive management: rationale and design of the electrocardiography sub-study of the MATRIX trial

BACKGROUND

The twelve‑lead electrocardiogram (ECG) has become an essential tool for the diagnosis, risk stratification, and management of patients with acute coronary syndromes (ACS). However, several areas of residual controversies or gaps in evidence exist. Among them, P-wave abnormalities identifying atrial ischemia/infarction are largely neglected in clinical practice, and their diagnostic and prognostic implications remain elusive; the value of ECG to identify the culprit lesion has been investigated, but validated criteria indicating the presence of coronary occlusion in patients without ST-elevation are lacking; finally, which criteria among the multiple proposed, better define pathological Q-waves or success of revascularisation deserve further investigations.

METHODS

The Minimizing Adverse hemorrhagic events via TRansradial access site and systemic Implementation of AngioX (MATRIX) trial was designed to test the impact of bleeding avoidance strategies on ischemic and bleeding outcomes across the whole spectrum of patients with ACS receiving invasive management. The ECG-MATRIX is a pre-specified sub-study of the MATRIX programme which aims at analyzing the clinical value of ECG metrics in 4516 ACS patients (with and without ST-segment elevation in 2212 and 2304 cases, respectively) with matched pre and post-treatment ECGs.

CONCLUSIONS

This study represents a unique opportunity to further investigate the role of ECGs in the diagnosis and risk stratification of ACS patients with or without ST-segment deviation, as well as to assess whether the radial approach and bivalirudin may affect post-treatment ECG metrics and patterns in a large contemporary ACS population.

Significance of New, Isolated T-wave Inversion in Multiple Electrocardiogram Leads with Regadenoson Injection in Patients with Normal Myocardial Perfusion Imaging: An Observational Report of 5 Consecutive Cases

INTRODUCTION

The pharmacologic (regadenoson) stress myocardial perfusion imaging (MPI) is used widely in patients who cannot exercise for detecting coronary artery disease (CAD). The interpretation of these studies depends primarily on the imaging results because the sensitivity of electrocardiograms (ECG) in this setting is poor. Prior study showed that effects of regadenoson on ST-segment occurred infrequently and had low sensitivity for detecting CAD. The significance of T-wave inversion in multiple ECG leads without ST-segment depression with regadenoson injection in patients with normal MPI is described and reported.

METHODS

ECGs were reviewed retrospectively in 64 patients who had regadenoson MPI and coronary angiography for evaluation of CAD from June 1, 2016 to August 31, 2018. Five cases were identified with new, isolated T-wave inversion in multiple ECG leads.

RESULTS

All five cases had new and isolated T-wave inversion in multiple leads without ST segment depression with regadenoson injection and normal MPI. At coronary angiography, three of the five cases showed obstructive coronary artery disease who received coronary percutaneous intervention. One case had nonobstructive coronary artery disease and one had a normal coronary artery.

CONCLUSIONS

Despite nonspecific ST-T changes on baseline ECGs and normal MPI in all patients, three of five cases had obstructive CAD by coronary angiography. New, isolated T-wave inversion in multiple ECG leads with regadenoson injection were observed in our patients with normal MPI. These ECG findings may be associated with false negative MPI. Therefore, careful observation and scrutiny of all ECG changes, especially new, isolated T-wave inversion in multiple ECG leads during regadenoson MPI is advisable to identify potential obstructive CAD despite normal MPI findings.

Link between Brugada phenocopy and myocardial ischemia: Results from the International Registry on Brugada Phenocopy

BACKGROUND

Brugada phenocopies clinical entities that have indistinguishable electrocardiographic (ECG) patterns from true congenital Brugada syndrome. However, they are induced by other clinical circumstances such as myocardial ischemia. The purpose of our study was to examine the clinical features and pathogenesis of ischemia-induced Brugada phenocopy (BrP).

METHODS

Data from 17 cases of ischemia-induced BrP were collected from the International Registry (www.brugadaphenocopy.com). Data were extracted from these publications and authors were contacted to provide further insight into each case.

RESULTS

Of the patients included in this study, 71% were male. Mean age was 59 ± 11 years (range: 38-76). Type-1 Brugada ECG pattern occurred in 15/17 (88%) of the cases, while a type-2 Brugada ECG pattern was observed in the other 2/17 (12%). In all cases, the Brugada ECG pattern resolved upon correction of the ischemia, indicating ischemia as the inducing circumstance. No arrhythmic events have been detected acutely or during the follow-up. Reported time to resolution ranged from 2 minutes to 5 hours. Provocative challenges using sodium channel blocking agents were performed in 7/17 cases (41%), and all failed to induce a Brugada ECG pattern (BrP Class A). The remaining 10/17 cases (59%) did not undergo provocative testing due to various clinical reasons.

CONCLUSIONS

Myocardial ischemia is a commonly reported etiology of BrP. Importantly, this study found no association between BrP induced by myocardial ischemia and sudden cardiac death or malignant ventricular arrhythmias.

Pretreatment with neuregulin-1 improves cardiac electrophysiological properties in a rat model of myocardial infarction

Neuregulin-1 (NRG-1) is considered to be a potential therapeutic agent for cardiovascular diseases due to its diverse protective effects. The aim of the present study was to investigate the effect of NRG-1 on cardiac electrophysiology in rats with myocardial infarction (MI). The rats were randomly divided into three groups: The sham operation group (SO; n=8); MI group (n=8); and the MI with recombinant human NRG (rhNRG)-1 administration group (NRG-1 group; 10 µg/kg; n=8). A rat MI model was established via ligation of the left anterior descending coronary artery. The rats in the NRG-1 group received a 10 µg/kg rhNRG-1 injection through the tail vein 30 min prior to ligation. Following 24 h of intervention, the field potential (FP) parameters, including the interspike interval (ISI), field potential duration (FPD), FPrise, FPmin, FPmax and conduction velocity (CV), were measured using microelectrode array technology. Subsequently, burst pacing was performed to assess ventricular arrhythmia (VA) susceptibility in the left ventricle. FP parameters in the MI group were significantly different when compared with those observed in the SO group. ISI, FPD, FPrise and FPmax in the infarct, peri-infarct and normal zones, as well as the CV of the infarct and peri-infarct zones, were all significantly decreased, and FPmin in the normal zone was increased (P<0.05). However, when compared with the MI group, NRG-1 prolonged the ISI and FPD in the 3 zones, and increased FPrise in the infarct zone, FPmax in the normal zone and CV in the peri-infarct zone; it also decreased FPmin in the normal zone (P<0.05). Furthermore, the incidence of VA was significantly reduced in the NRG-1 group when compared with the MI group (P<0.05). In conclusion, NRG-1 improved cardiac electrophysiological properties and reduced VA susceptibility in acute MI.

Brugada phenocopy associated with left ventricular aneurysm

Brugada phenocopies (BrP) are clinical entities that are characterized by ECG patterns identical to those of Brugada syndrome, but are the result of various clinical conditions. We describe the case of a 41-year-old male who exhibited BrP due to a left ventricular aneurysm in the context of chronic coronary artery disease.

Tpeak-Tend/QT interval predicts ST-segment resolution and major adverse cardiac events in acute ST-segment elevation myocardial infarction patients undergoing percutaneous coronary intervention

Elevated ST-segment and increased Tpeak-Tend interval (Tp-e) were prognostic predictors in major adverse cardiac events (MACEs) in ST-segment elevation myocardial infarction (STEMI). The electrophysiologic relationship between them during percutaneous coronary intervention (PCI) needs to elucidate.Patients with STEMI admitted to hospital were prospectively evaluated. ST-segment resolution (STR) (defined as ≥50% reduction as the complete-STR [CSTR] group, <50% as incomplete-STR [ISTR] group), Tp-e interval, and ratio of Tp-e to QT interval (Tp-e/QT) were measured, calculated and analyzed with MACEs.Tp-ec interval (corrected Tp-e interval, P < .001) and Tp-e/QT ratio (P < .001) were significantly increased by myocardial infarction and partly recovered post-PCI. Patients with ISTR showed more increased Tp-ec interval (P < .001) and Tp-e/QT ratio (P < .001) than those in CSTR groups post-PCI. In multivariate analysis and receiver operating characteristic curves analysis, Tp-e/QT was an independent and strongest predictor for STR. STR and electrocardiogram parameters with a cutoff value for predicting STR showed prognostic value for MACE in STEMI in Kaplan-Meier survival analysis.Both STR and change of Tp-e parameters were not only predictors of arrhythmia, but also prognostic factors of MACE in patients with STEMI after PCI.

The de winter electrocardiogram pattern is a transient electrocardiographic phenomenon that presents at the early stage of ST-segment elevation myocardial infarction

BACKGROUND

The de Winter electrocardiogram (EKG) pattern is a novel sign that indicates left anterior descending coronary artery (LAD) occlusion in patients with chest pain. This study aimed to assess the prevalence and clinical characteristics of patients with this pattern.

HYPOTHESIS

The de Winter EKG pattern is an special anterior ST-segment elevation myocardial infarction (STEMI) equivalents without obvious ST-segment elevation.

METHODS

This retrospective study included all patients with anterior myocardial infarction admitted between January 2011 and December 2017. Patients were categorized into two groups: those with the de Winter EKG pattern and those with typical STEMI.

RESULTS

Of 441 patients, 15 (3.4%) with anterior myocardial infarction had the de Winter EKG pattern. Similar to those with typical STEMI, the majority of patients with the de Winter EKG pattern had ST-segment elevation, pathologic Q wave, and absence of R wave at follow-up. The median time from recognition of this pattern until its evolution was 114 minutes. The ST-segment in leads V3R to V5R and leads V7 to V9 were normal or slightly depressed when a typical de Winter EKG pattern was noted in leads V1 to V6. The culprit lesion was mainly in the proximal LAD or the diagonal branch. Patients with this EKG pattern responded poorly to thrombolytic therapy.

CONCLUSIONS

We believe that the de Winter EKG pattern may be a sign of ischemia and presents at the early stage of STEMI rather than being an independent pattern. In patients with this pattern, a percutaneous coronary intervention rather than follow-up and thrombolytic strategy should be performed.

"Lambda-wave" ST-elevation is associated with severe prognosis in stress (takotsubo) cardiomyopathy

BACKGROUND

Persistent ST-segment elevation in acute coronary syndrome is associated with both short and long-term complications. By contrast, there is limited information about ST-elevation and its evolution during takotsubo (stress) cardiomyopathy (TTC).

AIM

To evaluate whether persistent downsloping ST-elevation in the early stages of TTC might correlate with short and long-term clinical events.

METHODS

One-hundred fifty-eight consecutive subjects with TTC were prospectively enrolled and assessed by electrocardiogram. Patients were classified in two groups according to the presence of downsloping ST-elevation ≥5 mm lasting at least 24 hr ("lambda-wave" ST-elevation group vs. without downsloping ST-elevation) in at least one/two contiguous leads.

RESULTS

Five (3.2%) patients, all female with a mean left ventricular ejection fraction 32 ± 5%, were included in the lambda-wave ST-elevation group. These patients were characterized by a higher prevalence of physical stressor (100% vs. 49%, p = 0.04) and higher admission and peak levels of troponin-I levels during hospitalization. Peak of ST-elevation in the lambda-wave ST-elevation group was reached 6 hr after admission and gradually decreased after 24 hr. In-hospital complications were observed in all the patients presenting lambda ST-elevation (100% vs. 23%, p = 0.03, OR: 29.1, p = 0.04); one patient presented endoventricular thrombosis and two died of cardiogenic shock. At long-term follow-up (mean 443 days), adverse events were observed in 80% of patients with lambda-wave ST-elevation (RR of adverse events at follow-up 32, p < 0.01).

CONCLUSION

Persistent downsloping lambda-wave ST-elevation during the acute phase of stress cardiomyopathy may be associated with a higher risk of adverse events at short and long-term follow-up.

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.

Spatial indices of repolarization correlate with non-ST elevation myocardial ischemia in patients with chest pain

Mild-to-moderate ischemia does not result in ST segment elevation on the electrocardiogram (ECG), but rather non-specific changes in the T wave, which are frequently labeled as non-diagnostic for ischemia. Robust methods to quantify such T wave heterogeneity can have immediate clinical applications. We sought to evaluate the effects of spontaneous ischemia on the evolution of spatial T wave changes, based on the eigenvalues of the spatial correlation matrix of the ECG, in patients undergoing nuclear cardiac imaging for evaluating intermittent chest pain. We computed T wave complexity (TWC), the ratio of the second to the first eigenvalue of repolarization, from 5-min baseline and 5-min peak-stress Holter ECG recordings. Our sample included 30 males and 20 females aged 63 ± 11 years. Compared to baseline, significant changes in TWC were only seen in patients with ischemia (n = 10) during stress testing, but not among others. The absolute changes in TWC were significantly larger in the ischemia group compared to others, with a pattern that seemed to depend on the severity or anatomic distribution of ischemia. Our results demonstrate that ischemia-induced changes in T wave morphology can be meaningfully quantified from the surface 12-lead ECG, suggesting an important opportunity for improving diagnostics in patients with chest pain.

2,3,5,4'-Tetrahydroxystilbene-2-O-β-D-glucoside protects murine hearts against ischemia/reperfusion injury by activating Notch1/Hes1 signaling and attenuating endoplasmic reticulum stress

2,3,5,4'-Tetrahydroxystilbene-2-O-β-D-glucoside (TSG) is a water-soluble active component extracted from Polygonum multiflorum Thunb. A number of studies demonstrate that TSG exerts cardioprotective effects. Since endoplasmic reticulum (ER) stress plays a key role in myocardial ischemia/reperfusion (MI/R)-induced cell apoptosis, we sought to determine whether modulation of the ER stress during MI/R injury was involved in the cardioprotective action of TSG. Male mice were treated with TSG (60 mg·kg^-1·d^-1, ig) for 2 weeks and then were subjected to MI/R surgery. Pre-administration of TSG significantly improved post-operative cardiac function, and suppressed MI/R-induced myocardial apoptosis, evidenced by the reduction in the myocardial apoptotic index, serum levels of LDH and CK after 6 h of reperfusion. TSG (0.1-1000 μmol/L) did not affect the viability of cultured H9c2 cardiomyoblasts in vitro, but pretreatment with TSG dose-dependently decreased simulated ischemia/reperfusion (SIR)-induced cell apoptosis. Furthermore, both in vivo and in vitro studies revealed that TSG treatment activated the Notch1/Hes1 signaling pathway and suppressed ER stress, as evidenced by increasing Notch1, Notch1 intracellular domain (NICD), Hes1, and Bcl-2 expression levels and by decreasing p-PERK/PERK ratio, p-eIF2α/eIF2α ratio, and ATF4, CHOP, Bax, and caspase-3 expression levels. Moreover, the protective effects conferred by TSG on SIR-treated H9c2 cardiomyoblasts were abolished by co-administration of DAPT (the Notch1 signaling inhibitor). In summary, TSG ameliorates MI/R injury in vivo and in vitro by activating the Notch1/Hes1 signaling pathway and attenuating ER stress-induced apoptosis.

Intracoronary acetylcholine application as a possible probe inducing J waves in patients with early repolarization syndrome

Acetylcholine is widely used for a diagnostic provocation test of coronary spasm in patients with vasospastic angina. Acetylcholine usually induces coronary vasodilatation mediated by muscarinic receptor activation, but sometimes it evokes vasoconstriction of coronary arteries where the endothelium is damaged. Early repolarization syndrome is characterized by a J wave observed at the end of the QRS complex in a surface electrocardiogram. The J wave is attributed to the transmural voltage gradient at the early repolarization phase across the ventricular wall, which stems mainly from prominent transient outward current in the epicardium, but not in the endocardium. Transient high-dose application of acetylcholine into the epicardial coronary arteries provides a unique opportunity to augment net outward current, selectively, in the ventricular epicardium and unmask the J wave, irrespective of the cardiac ischemia based on coronary spasm. Acetylcholine augments cardiac membrane potassium conductance by enhancing acetylcholine-activated potassium current directly and by activating adenosine triphosphate-sensitive potassium current, in addition to the reduced sodium and calcium currents in the setting of severe ischemia due to vasospasm. However, the role of acetylcholine as an arrhythmogenic probe of the J wave induction in patients with suspected early repolarization syndrome warrants future prospective study.

Cardiac-protective effects and the possible mechanisms of alatamine during acute myocardial ischemia

Alatamine is a constituent in the extract of a traditional herbal medicine Ramulus euonymi widely used for cardiac protection. However, its precise effects remain unclear. In the present study, we found that alatamine was able to reduce acute myocardial ischemia (AMI)-induced cardiac dysfunction in a rat model, as reflected by significantly restored electrocardiograms, M-mode echocardiograms, and left ventricular hemodynamics. Also, Nagar Olsen staining revealed that alatamine markedly reduced AMI-induced cardiac injury and cardiac myocyte apoptosis. TUNEL and caspase-3 activity assay showed that cardiac myocytes underwent significant apoptosis during AMI, and levels of LDH and CK-MB increased in the serum. However, such changes were significantly inhibited by pre-administration of alatamine. Furthermore, such anti-apoptotic effects of alatamine was also confirmed in a cardiac myocyte model of isoproterenol (ISO)-induced damage. Mechanistically, it was also found that alatamine improved the expression and activity of sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA), which were inhibited during AMI, promoting contractility and relaxation. Meanwhile, alatamine decreased Bax and increased Bcl-2 expressions both in vivo and in vitro, therefore inhibiting cardiac myocyte apoptosis and preventing cardiac dysfunction caused by AMI at the cellular level. The present study revealed the beneficial role of alatamine in cardiac protection and highlighted it as a potential therapeutic reagent for reduction of AMI-induced cardiac injury.

Chemical chaperone 4-phenylbutyric acid protects H9c2 cardiomyocytes from ischemia/reperfusion injury by attenuating endoplasmic reticulum stress-induced apoptosis

Myocardial ischemia/reperfusion (I/R) is a potential contributor to high rates of mortality in several cardiovascular diseases. I/R initiates the unfolded protein response and endoplasmic reticulum (ER) stress, which may lead to apoptotic pathways and exaggerate I/R injury. 4‑phenylbutyric acid (4‑PBA), a low molecular weight, terminal aromatic substituted fatty acid, has been reported to function as an ER chaperone. The aim of the present study was to investigate whether 4‑PBA is able to reduce ER stress‑induced apoptosis and prevent cardiomyocyte damage during the process of I/R in vitro. Accordingly, the rat cardiomyocyte line, H9c2, was treated with hypoxia/reoxygenation as an I/R model in vitro. Myocardium apoptosis was determined with TUNEL staining. The expression of ER stress‑related proteins were examined by western blotting. The resulting data showed that I/R activates the ER stress proteins, glucose‑regulated protein 78, activating transcription factor 6 and protein kinase RNA‑like endoplasmic reticulum kinase, which were all reduced by pretreatment with 4‑PBA. In addition, pretreatment with 4‑PBA significantly inhibited the expression levels of pro‑apoptotic proteins, C/EBP homologous protein, B cell lymphoma (Bcl‑2)‑associated X protein and phosphorylated c‑Jun N‑terminal kinase, and enhanced the expression of the anti‑apoptotic protein Bcl‑2 (n=3; P<0.05). The data demonstrated that I/R initiates ER stress‑associated apoptotic pathways, and 4‑PBA pretreatment protected the cardiomyocytes from I/R‑induced cell death. To the best of our knowledge, the present study is the first to report on the cell repair mechanism of 4‑PBA against I/R damage in cardiomyocytes based on ER stress‑associated apoptotic pathways.

Effects of histidine and vitamin C on isoproterenol-induced acute myocardial infarction in rats

In the present study, we investigated the effects of histidine and vitamin C (alone or in combination) treatments against isoproterenol (a β-adrenergic receptor agonist)-induced acute myocardial infarction in rats. We used propranolol (a β-adrenergic receptor blocker) to compare the results. Rats were given intraperitoneal injections of histidine (40 mg kg(-1)) and vitamin C (40 mg kg(-1)) alone and combined daily for 21 days. Propranolol (10 mg kg(-1)) was orally administered daily for 10 days (from day 11 to day 21). Myocardial infarction was induced by subcutaneous injections of 150 mg kg(-1) of isoproterenol at an interval of 24 hr on days 20 and 21. Blood and tissue samples were taken for histopathological and biochemical evaluations following electrocardiography recording on day 21. Isoproterenol elevated ST segment, increased heart weight, heart rate, serum activities of aspartate transaminase, lactate dehydrogenase, creatine kinase-MB and heart tissue content of malondialdehyde, and decreased R wave amplitude and superoxide dismutase and catalase activities of heart tissue. Necrosis, edema and inflammatory cells infiltration were observed in myocardial tissue sections. Our results indicated that histidine and vitamin C alone, and especially in combination prevent isoproterenol-induced cardiotoxicity and have similar protective effects with propranolol. Cardioprotective effects of histidine and vitamin C may be associated with their ability to reduce free radical-induced toxic effects.

Clinical Utility of Ventricular Repolarization Dispersion for Real-Time Detection of Non-ST Elevation Myocardial Infarction in Emergency Departments

BACKGROUND

A specific electrocardiographic (ECG) marker of ischemia would greatly improve the speed and accuracy of detecting and treating non-ST elevation myocardial infarction (NSTEMI). We hypothesize that ischemia induces ventricular repolarization dispersion (VRD), altering the T-wave before any ST segment deviation. We sought to evaluate the clinical utility of VRD to (1) detect NSTEMI cases in the emergency department (ED) and (2) identify NSTEMI cases at high risk for in-hospital major adverse cardiac events (MACEs).

METHODS AND RESULTS

We continuously recorded 12-lead Holter ECGs from chest pain patients upon their arrival to the ED. VRD was quantified using principal component analysis of the 12-lead ECG to compute a T-wave complexity ratio (ie, ratio of second to first eigenvectors of repolarization). Clinical outcomes were obtained from hospital records. The sample was composed mainly of older males (n=369; ages 63±12 years; 63% males), and 92 (25%) had NSTEMI and 26 (7%) had MACEs. Baseline T-wave complexity ratio modestly correlated with peak troponin levels (r=0.41; P<0.001) and was a good classifier of NSTEMI events (area under the curve=0.70). An increased T-wave complexity ratio on the presenting ECG was strongly associated with NSTEMI (odds ratio [OR]=3.8 [2.1 to 5.8]) and in-hospital MACE (OR=8.2 [3.1 to 21.5]).

CONCLUSIONS

A simple measure of global VRD on the presenting 12-lead ECG correlates with ischemic myocardial injury and can discriminate NSTEMI cases very early during evaluation. Prospective studies should validate these findings and test whether VRD can guide therapy.

Transient repolarization alterations dominate the initial phase of an acute anterior infarction--a vectorcardiography study

OBJECTIVE

To study effects of ischemia-reperfusion on ventricular electrophysiology in humans by three-dimensional electrocardiography.

METHODS

Fifty-seven patients with first-time acute anterior ST elevation myocardial infarction were monitored from admission and >24h after symptom onset with continuous vectorcardiography (VCG; modified Frank orthogonal leads). Global ventricular depolarization and repolarization (VR) measures were compared at maximum vs. minimum ST vector magnitude (STVM) (median 208; 111-303 vs. 362; 165-1359min after symptom onset).

RESULTS

At maximum vs. minimum STVM the Tarea (overall VR dispersion) almost tripled (118 vs. 41μVs; p<0.0001), the T-loop bulginess was 90% greater (Tavplan 0.91 vs 0.48μV; p<0.0001), and Tpeak-end/QT was 39% larger (0.32 vs 0.23; p<0.0001). QRSarea (overall dispersion of depolarization) was 12% larger at maximum STVM, while QRS duration was 10% longer at minimum STVM.

CONCLUSIONS

Ischemia-reperfusion was accompanied by profound and transient alterations of VR dispersion, while changes in depolarization were modest and delayed.