In the emergency department, the patient’s blood pressure was 100/68 mm Hg and his heart rate was 49 beats/min. Figure 1 shows atrial fibrillation, junctional escape beats followed by several ...consecutive relatively narrow QRS complexes with a beat-to-beat change in their axis, and an alternating left and right bundle branch block pattern. 19606089 6 Kusumoto FM Schoenfeld MH Barrett C. 2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society.
The J wave, also referred to as an Osborn wave, is a deflection immediately following the QRS complex of the surface ECG. When partially buried in the R wave, the J wave appears as J-point elevation ...or ST-segment elevation. Several lines of evidence have suggested that arrhythmias associated with an early repolarization pattern in the inferior or mid to lateral precordial leads, Brugada syndrome, or arrhythmias associated with hypothermia and the acute phase of ST-segment elevation myocardial infarction are mechanistically linked to abnormalities in the manifestation of the transient outward current (I(to))-mediated J wave. Although Brugada syndrome and early repolarization syndrome 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 that we propose be termed J-wave syndromes. This review summarizes our current state of knowledge concerning J-wave syndromes, bridging basic and clinical aspects. We propose to divide early repolarization syndrome into three subtypes: type 1, which displays an early repolarization pattern predominantly in the lateral precordial leads, is prevalent among healthy male athletes and is rarely seen in ventricular fibrillation survivors; type 2, which displays an early repolarization pattern predominantly in the inferior or inferolateral leads, is associated with a higher level of risk; and type 3, which displays an early repolarization pattern globally in the inferior, lateral, and right precordial leads, is associated with the highest level of risk for development of malignant arrhythmias and is often associated with ventricular fibrillation storms.
A prominent J wave is encountered in a number of life-threatening cardiac arrhythmia syndromes, including the Brugada syndrome and early repolarization syndromes. Brugada syndrome and early ...repolarization syndromes differ with respect to the magnitude and lead location of abnormal J waves and are thought to represent a continuous spectrum of phenotypic expression termed J-wave syndromes. Despite two decades of intensive research, risk stratification and the approach to therapy of these 2 inherited cardiac arrhythmia syndromes are still undergoing rapid evolution. Our objective in this review is to provide an integrated synopsis of the clinical characteristics, risk stratifiers, and molecular, ionic, cellular, and genetic mechanisms underlying these 2 fascinating syndromes that have captured the interest and attention of the cardiology community in recent years.
Mexiletine, a class Ib antiarrhythmic drug, exhibits its major antiarrhythmic effect via inhibition of the fast and late Na+ currents in myocardial tissues that are dependent on the opening of Na+ ...channels for their excitation. Through a comprehensive examination of mexiletine's therapeutic benefits and potential risks, we aim to provide valuable insights that reinforce its role as a vital therapeutic option for patients with ventricular arrhythmias, long QT syndrome, and other heart rhythm disorders. This review will highlight the current understandings of the antiarrhythmic effects and rationales for recent off‐label use and address the mortality and proarrhythmic effects of mexiletine utilizing published basic and clinical studies over the past five decades.
This case report describes a teenager with a history of cardiomyopathy and recurrent syncope who was admitted to the pediatric unit with a urinary tract infection.
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•Doping modifies physico-chemical properties of graphene and dichalcogenides.•Non-metal elements such as N, B, Si, P, and S are the common dopants to graphene.•Semiconducting ...dichalcogenide dopants include W, Co, Fe, Mn, Nb, Se and S.•Doped 2D materials exhibit improved performance as sensors and optoelectronic devices.
In recent years, research on two-dimensional (2D) materials including graphene and transition metal dichalcogenides (TMDCs), especially molybdenum and tungsten disulfides (MoS2 and WS2), has rapidly developed. In order to meet the increasing demands of using these 2D materials in fields as diverse as optoelectronics and sensing, heteroatom doping has become an effective method to tune their electronic and physico-chemical properties. This review discusses versatile doping methods applied to graphene and TMDCs, the corresponding changes to their properties, and their potential applications. Future perspectives and new emerging areas are also presented.
Background
On surface electrocardiographic (ECGs), it is difficult to differentiate Ito‐mediated J waves, a repolarization phenomenon seen in J wave syndromes (JWS) from terminal QRS deflections that ...mimic J waves (pseudo J waves) in intraventricular conduction delay (IVCD), an abnormality in depolarization. We hypothesize that the difference between the “maximum QRS duration” inclusive of J point or terminal QRS deflections and the minimum QRS duration identified across a 12‐lead ECG is significantly larger in Ito‐mediated J waves, and can serve as a marker to make this distinction.
Methods
A retrospective analysis was performed on adults with ECGs consisting of one of the four following manifestations: J waves associated with hypothermia and early repolarization, and pseudo J waves associated with right bundle branch block (RBBB) and non‐specific intraventricular conduction delay (NS‐IVCD). All ECGs were assessed individually and the maximum and minimum discrete QRS deflections on 12‐lead tracings, defined as “QRSmax” and QRSmin, were identified. The difference between “QRSmax” and QRSmin, designated as ∆QRS, was calculated and compared across the studied populations.
Results
A total of 60 patients consisting of 15 patients in each arm were included in the study. ΔQRS was significantly larger in the hypothermia and early repolarization groups, compared to RBBB and NS‐IVCD (p < .0001), with the following mean ∆QRS: hypothermia 54.3 ± 13.7 ms, early repolarization pattern 47.3 ± 15.3 ms, RBBB 19.3 ± 6.5 ms, and NS‐IVCD 16.0 ± 6.6 ms.
Conclusion
∆QRS may serve as a reliable ECG parameter for distinguishing Ito‐mediated J waves from pseudo J waves produced by delayed intraventricular conduction.
Drugs that prolong QT may cause torsade de pointes (TdP). However, translation of nonclinical assessment of QT prolongation or hERG channel, targeted by QT‐prolonging drugs, into clinical TdP risk ...has been insufficient to date. In this blinded study, we confirmed the utility of a Normalized TdP Score System in predicting drug‐induced TdP risks among 34 drugs, including 28 with low, intermediate, and high TdP risks under the Comprehensive In Vitro Proarrhythmia Assay (CiPA) initiative plus six compounds with names blinded to the investigators, using the rabbit ventricular wedge assay. Concentration‐dependent TdP scores were determined by drug‐induced changes in QT, Tp‐e, and proarrhythmias. Disclosure of the names and testing concentrations was made after completion of the experiments and report to the sponsors. Drugs’ normalized TdP scores were calculated thereafter based on their respective free clinical maximum concentration (Cmax). Drugs’ normalized TdP scores were calculated and ranked for 33 drugs, excluding 1 investigational drug, and the TdP risks of the 28 CiPA drugs were correctly distinguished according to their respective categories of low, intermediate, and high TdP risks under the CiPA initiative. Accordingly, we are able to propose the cutoff values of the normalized TdP scores at 1 × Cmax: ≤ 0, > 0 to < 0.65 and ≥ 0.65, respectively, for low, intermediate, and high risk. This blinded study supports utility of our Normalized TdP Score System in predicting drug‐induced TdP risks in 33 drugs, including 28 used for characterization of other assays under the CiPA initiative. However, these results need to be replicated in other laboratories.
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