J波和J波综合征

心电图上J点抬高≥0．1mV，时程≥20ms的圆顶状或驼峰状波称为J波。J波综合征是指心电图具有J波特征的临床症状群，包括Brugada综合征、特发性心室颤动、急性冠状动脉综合征的超急期和早期复极综合征。J波形成的离子流机制是瞬时外向钾电流的增加。电生理基础是内外膜电位差和复极离散度增大，产生2位相折返。     

J波和J波综合征

心电图上J点抬高≥0.1mV,时程≥20ms的圆顶状或驼峰状波称为J波。J波综合征是指心电图具有J波特征的临床症状群,包括Brugada综合征、特发性心室颤动、急性冠状动脉综合征的超急期和早期复极综合征。J波形成的离子流机制是瞬时外向钾电流的增加。电生理基础是内外膜电位差和复极离散度增大,产生2位相折返。     

问：何谓J波和J波综合征？

答：心电图上J点抬高≥0．2mV、时程≥20ms的圆顶状或驼峰状波称之为J波。J波的检出率在一般人群中约2．5％左右，多见于早期复极综合征。另外，Brugada综合征、特发性室颤、急性冠状动脉综合征的超急期等临床症候群在心电图上亦可见J波。目前，将这些心电图上具有J波，同时又伴有各自临床特点的临床症候群统称为J波综合征。     

异常J波38例临床分析

目的探讨异常J波的疾病分布及临床特点。方法对检出含有异常J波的38例分析其所属疾病及临床特点。结果38例中早期复极综合征（ERS）35例,Brugada波3例（其中Brugada综合征1例）。结论J波是许多临床综合征（如ERS、Brugada综合征）的心电图标志,有重要临床意义。     

异常J波综合征

J波是紧随QRS波群之后的一个小的半圆形波。1953年，Osborn在犬的实验中对其进行了较详细的描述。因而J波又称Osborn波。J波在人体可见于生理和病理状态。自从10年前严干新和Antzelevitch首次阐述其细胞和离子机制以来，对J波的临床意义有了更进一步的认识。越来越多的资料表明．由瞬时外向钾电流（Ito）介导的J波，是许多临床综合征如Brugada综合征、原发性室颤（或称夜间猝死综合征）和早复极综合征的心电图标志。J波的细胞和离子流机制在Brugada综合征、原发性室颤、甚至ST段抬高的心肌梗死所致的心源性猝死的发生中发挥着重要作用。因此，这些临床综合征可以统称为瞬时外向钾电流（Ito）介导的J波综合征。本文试图回顾J波的研究现状、临床意义并展望将来可能的研究方向。     

J波综合征研究进展

J波综合征是心电图上有J波特征的一系列临床综合征的总称,包含早期复极综合征、Brugada综合征、特发性心室颤动和急性冠状动脉综合征超急期等。2010年专家学者依据J波综合征是否有遗传倾向,将其分为遗传性J波综合征和获得性J波综合征。现就近些年J波综合征的研究概况进行综述。     

心电图J波的临床意义和发生机制

J波是由心电图上QRS波终末转折处与ST段起始相交的J点升高和嗣后相应的ST段偏移所组成 ,形态上象QRS尾部的δ波或象QRS终末的第二个R波 (R′ ,图 1)。图 1　低温J波自从 1938年报道J波以来 ,曾有过多种命名。临床上J波与多种疾病相关 ,形成机制不十分明确 ,心电图表现呈一过性或持续性 ,曾引起学者们的注意。近 10多年来 ,由于对Brugada综合征的认识和研究 ,使得人们对J波又有了新的兴趣和关注 ,尤其临床上 ,J波可以出现在从预后良好的早期复极综合征 (earlyrepolarizationsyndrome,ERS)到猝死高危险的Brugada综合征 ,覆盖面广 ,…     

J波与J波综合征

早期复极综合征、Brugada综合征、变异型Brugada综合征(包括"下壁导联有明显J波的心脏性猝死","下壁导联有明显J波及ST段下斜型抬高的原发性室颤")的离子及细胞学机制相似,被称为Ito电流调节的"J波综合征",它们之间的区别仅在于Ito电流密度及J波大小。Ito电流密度及J波大小在诱发心律失常中起重要作用。Brugada综合征时V1～V3导联出现J波及ST抬高,发生心脏性猝死的危险性高;而早期复极综合征时V4～V6导联出现J波及ST抬高,一般认为是良性的。换句话说,累及右室的J波可能致心律失常,累及左室前侧壁的J波常是良性的,而累及左室下壁的明显J波及ST抬高对检出既往不明原因晕厥患者处于心脏性猝死的高危状态具有诊断意义。     

早期复极综合征与急性心肌梗死的Osborn（J）波的心电图鉴别诊断

Osborn（J）波综合征是由瞬时外向钾电流（Ito）介导的J波，亦统称为Ito介导的J波综合征。如早期复极综合征（ERS），Brugada综合征，ST段抬高的急性心肌梗死（AMI）等生理和病理状态多种原因引起。故ERS误诊为AMI屡见不鲜，而AMI伴发J波时也易误诊为ERS，因而本文就ERS和AMI的J波主要描述在心电图上的鉴别。     

Brugada综合征和特发性J波的临床分析

目的：了解Brugada综合征和特发性J波的临床和心电图特点及其异同点,方法：对收集的10例Brugada综合征和8例特发性J波患者临床和心电图资料进行对比并结合文献。结果：两病有 相似的临床和心电图表现,但心电图表现仍有一定区别,Brugada综合征R’波大于R波,多见于V1－V3导联,伴ST段持续抬高,T波倒置,图形较恒定,特发性J波中J波小于R波,在Ⅱ,Ⅲ,aVF和V4－V6导联多见,无T波倒置,J波可因药物,运动等原因在短时间内明显改变。结论：Brugada综合征和特发性J波临床表现相似,可能有相同的发病机制,只是影响的部位不同,其区别主要在心电图表现。     

ECG Repolarization Waves: Their Genesis and Clinical Implications

The electrocardiographic (ECG) manifestation of ventricular repolarization includes J (Osborn), T, and U waves. On the basis of biophysical principles of ECG recording, any wave on the body surface ECG represents a coincident voltage gradient generated by cellular electrical activity within the heart. The J wave is a deflection with a dome that appears on the ECG after the QRS complex. A transmural voltage gradient during initial ventricular repolarization, which results from the presence of a prominent action potential notch mediated by the transient outward potassium current (I_to) in epicardium but not endocardium, is responsible for the registration of the J wave on the ECG. Clinical entities that are associated with J waves (the J‐wave syndrome) include the early repolarization syndrome, the Brugada syndrome and idiopathic ventricular fibrillation related to a prominent J wave in the inferior leads. The T wave marks the final phase of ventricular repolarization and is a symbol of transmural dispersion of repolarization (TDR) in the ventricles. An excessively prolonged QT interval with enhanced TDR predisposes people to develop torsade de pointes. The malignant “R‐on‐T” phenomenon, i.e., an extrasystole that originates on the preceding T wave, is due to transmural propagation of phase 2 reentry or phase 2 early afterdepolarization. A pathological “U” wave as seen with hypokalemia is the consequence of electrical interaction among ventricular myocardial layers at action potential phase 3 of which repolarization slows. A physiological U wave is thought to be due to delayed repolarization of the Purkinje system.     

Early repolarisation and J wave syndromes

J wave syndrome has emerged as a significant cause of Idiopathic ventricular fibrillation (IVF) responsible for sudden cardiac death. A large body of data is now available on genesis, genetics and ionic mechanisms of J wave syndromes. Two of these viz., Early repolarization syndrome (ER) and Brugada syndrome (BrS) are fairly well characterized enabling correct diagnosis in most patients. The first part of repolarization of ventricular myocardium is governed by Ito current i.e., rapid outward potassium current. The proposed mechanism of ventricular fibrillation (VF) and ventricular tachycardia (VT) storms is the faster I_to current in the epicardium than in the endocardium results in electrical gradient that forms the substrate for phase 2 reentry. Prevention of Ito current with quinidine supports this mechanism. Majority of ER patterns in young patients are benign. The key issue is to identify those at increased risk of sudden cardiac death. Association of both ER syndrome and Brugada syndrome with other disease states like coronary artery disease has also been reported. Individuals resuscitated from VF definitely need an implantable cardiac defibrillator (ICD) but in others there is no consensus regarding therapy. Role of electrophysiology study to provoke ventricular tachycardia or fibrillation is not yet well defined. Radiofrequency ablation of epicardial substrate in right ventricle in Brugada syndrome is also under critical evaluation. In this review we shall discuss historical features, epidemiology, electrocardiographic features, ionic pathogenesis, clinical features and current status of proposed treatment of ER and BrS.     

J wave syndromes: Molecular and cellular mechanisms

An early repolarization (ER) pattern in the ECG, consisting of J point elevation, distinct J wave with or without ST segment elevation or slurring of the terminal part of the QRS, was long considered a benign electrocardiographic manifestation. Experimental studies a dozen years ago suggested that an ER is not always benign, but may be associated with malignant arrhythmias. Validation of this hypothesis derives from recent case–control and population-based studies showing that an ER pattern in inferior or infero-lateral leads is associated with increased risk for life-threatening arrhythmias, termed early repolarization syndrome (ERS). Because accentuated J waves characterize both Brugada syndrome (BrS) and ERS, these syndromes have been grouped under the heading of J wave syndromes. BrS and ERS appear to share common ECG characteristics, clinical outcomes, risk factors as well as a common arrhythmic platform related to amplification of I_to-mediated J waves. However, they differ with respect to the magnitude and lead location of abnormal J waves and can be considered to represent a continuous spectrum of phenotypic expression. Recent studies support the hypothesis that BrS and ERS are caused by a preferential accentuation of the AP notch in right or left ventricular epicardium, respectively, and that this repolarization defect is accentuated by cholinergic agonists. Quinidine, cilostazol and isoproterenol exert ameliorative effects by reversing these repolarization abnormalities. Identifying subjects truly at risk is the challenge ahead. Our goal here is to review the clinical and genetic aspects as well as the cellular and molecular mechanisms underlying the J wave syndromes.     

Early Repolarization Syndrome: Electrocardiographic Signs and Clinical Implications

Early repolarization syndrome (ERS) was previously considered as a benign variant, but it has recently emerged as a risk marker for idiopathic ventricular fibrillation (VF) and sudden death. As measured by electrocardiogram (ECG), early repolarization is characterized by an elevation of the J point and/or ST segment from the baseline by at least 0.1 mV in at least two adjoining leads. In particular, early repolarization detected by inferior ECG leads was found to be associated with idiopathic VF and has been termed as ERS. This condition is mainly observed in young men, athletes, and blacks. Also, it has become evident that electrocardiographic territory, degree of J‐point elevation, and ST‐segment morphology are associated with different levels of risk for subsequent ventricular arrhythmia. However, it is unclear whether J waves are more strongly associated with a depolarization abnormality rather than a repolarization abnormality. Several clinical entities can cause ST‐segment elevation. Therefore, clinical and ECG data are essential for differential diagnosis. At present, the data set is insufficient to allow risk stratification in asymptomatic individuals. ERS, idiopathic VF, and Brugada syndrome (known as J‐wave syndromes) are three clinical conditions that share many common ECG features; however, their clinical consequences are remarkably different. This review summarizes the current electrocardiographic data concerning ERS with clinical implications.     

Genetic, molecular and cellular mechanisms underlying the J wave syndromes

An early repolarization (ER) pattern in the ECG, distinguished by J-point elevation, slurring of the terminal part of the QRS and ST-segment elevation has long been recognized and considered to be a benign electrocardiographic manifestation. Experimental studies conducted over a decade ago suggested that some cases of ER may be associated with malignant arrhythmias. Validation of this hypothesis was provided by recent studies demonstrating that an ER pattern in the inferior or inferolateral leads is associated with increased risk for life-threatening arrhythmias, termed ER syndrome (ERS). Because accentuated J waves characterize both Brugada syndrome (BS) and ERS, these syndromes have been grouped under the term "J wave syndromes". ERS and BS share similar ECG characteristics, clinical outcomes and risk factors, as well as a common arrhythmic platform related to amplification of I(to)-mediated J waves. Although BS and ERS differ with respect to the magnitude and lead location of abnormal J wave manifestation, they can be considered to represent a continuous spectrum of phenotypic expression. Although most subjects exhibiting an ER pattern are at minimal to no risk, mounting evidence suggests that careful attention should be paid to subjects with "high risk" ER. The challenge ahead is to be able to identify those at risk for sudden cardiac death. Here I review the clinical and genetic aspects as well as the cellular and molecular mechanisms underlying the J wave syndromes.     

Transition of the ST segment from a J wave to a coved-type elevation before ventricular fibrillation induced by coronary vasospasm in the precordial leads

We describe the case of a 63-year-old man whose electrocardiogram showed transition of the ST segment from a J wave to a coved-type elevation in precordial leads before ventricular fibrillation induced by right coronary artery vasospasm. Simultaneously, the ST segment in inferior leads was gradually depressed with a J wave. Considering the sudden death of his son, induced ventricular fibrillation by programmed electrical stimulation, and modulations of the ST segment in the precordial and inferior leads by pilsicainide, some abnormalities in repolarization associated with Brugada syndrome or early repolarization syndrome might have caused these atypical ST-segment manifestations.     

特发性异常J波与Brugada综合征的临床及心电图特征

目的探讨特发性异常J波与Brugada综合征的临床及心电学特点。方法对特发性异常J波与Brugada综合征各8例进行分析。结果①特发性异常J波在肢导联或(和)胸导联可见正向异常J波[除aVR(部分患者aVL)外],其波幅较低而分布较广,一般V1~V2导联不出现J波,若出现则JV1~V2R,TV1~V2(V3)倒置或直立。两者均易诱发多形性室性心动过速及/或心室颤动而致死。结论异常J波和Brugada综合征及Brugada样心电图象是具有不同临床及心电学特点的临床病症。     

Some Controversies about Early Repolarization: The Haïssaguerre Syndrome

Controversy has followed the groundbreaking and cornerstone paper of Haïssaguerre et al. Much of this controversy has been due to the use of the term “early repolarization pattern” and possible waveform morphologies on the standard 12‐lead ECG ( it is 10 second strip) that could predict who will manifest the malignant arrhythmogenic syndrome described by Haïssaguerre et al. The standard ECG definition of early repolarization pattern (ERP) or early repolarization variant (ERV) since then has changed its clinical meaning for a surface electrocardiographic waveform from benign to malignant. The new definition of ERP/ERV contains only J wave but ST‐segment elevation is no more obligatory. In the old definition, early repolarization pattern (ERP) or early repolarization variant (ERV) 3 is a well‐recognized idiopathic electrocardiographic phenomenon considered to be present when at least two adjacent precordial leads show elevation of the ST segment, with values equal or higher than 1 mm. In the new electrocardiographic ERP concept, the ST segment may or may not be elevated and can be up‐sloping, horizontal or down‐sloping while in the old ERP/ERV concept it must be elevated at least 1 mm in at least two adjacent leads and the variant is characterized by a diffuse elevation of the ST segment of upper concavity, ending in a positive T wave of V₂ to V₄ or V₅ and prominent J wave and ST‐segment elevation predominantly in left precordial leads. The phenomenon constitutes a normal variant; it is almost a rule in athletes (present in 89% of the cases in this universe).     

J波综合征

J波不仅存在于心电异常的正常人中而且在特发性心室颤动、B rugada综合征以及早期复极综合征中并非是一种罕见的现象,近一个世纪的基础和临床试验证实,J波发生的离子流机制是瞬时外向钾电流相对增加且最终确定了J波产生和恶性事件触发机制。由于J波的诸多特殊性,因此笔者就J波及J波综合征的主要心电现象做一综述。