J wave syndromes: a decade of progress

Abstract

Objective: The objective was to provide a brief history of J wave syndromes and to summarize our current understanding of their molecular, ionic, cellular mechanisms, and clinical features. We will also discuss the existing debates and further direction in basic and clinical research for J wave syndromes.

Data sources: The publications on key words of "J wave syndromes", "early repolarization syndrome (ERS)", "Brugada syndrome (BrS)" and "ST-segment elevation myocardial infarction (STEMI)" were comprehensively reviewed through search of the PubMed literatures without restriction on the publication date.

Study selection: Original articles, reviews and other literatures concerning J wave syndromes, ERS, BrS and STEMI were selected.

Results: J wave syndromes were firstly defined by Yan et al. in a Chinese journal a decade ago, which represent a spectrum of variable phenotypes characterized by appearance of prominent electrocardiographic J wave including ERS, BrS and ventricular fibrillation (VF) associated with hypothermia and acute STEMI. J wave syndromes can be inherited or acquired and are mechanistically linked to amplification of the transient outward current (I to )-mediated J waves that can lead to phase 2 reentry capable of initiating VF.

Conclusions: J wave syndromes are a group of newly highlighted clinical entities that share similar molecular, ionic and cellular mechanism and marked by amplified J wave on the electrocardiogram and a risk of VF. The clinical challenge ahead is to identify the patients with J wave syndromes who are at risk for sudden cardiac death and determine the alternative therapeutic strategies to reduce mortality.

Figure 1

The sequence of ventricular activation impacts the appearance of J wave in a pseudo-electrocardiogram recorded from coronary-perfused canine right ventricular wedge preparation. (a) Stimulation of the endocardial (Endo) surface causes the epicardial (Epi) surface to be activated last; (b) stimulation of the epicardial surface activates it before the endocardial surface; (c) endocardial activation at different locations can cause the J wave to occur at the end of the QRS, manifesting as slurred (left panel) or notched (right panel) QRS.

Figure 2

Electrocardiogram obtained from a 34-year-old Chinese man who survived cardiac arrest displaying characteristics of Brugada syndrome, early repolarization syndrome and idiopathic ventricular fibrillation.

Figure 3

Frequency-dependent changes in epicardial notch and J wave amplitude. (a) Simultaneously recorded transmural electrocardiogram (ECG) and transmembrane action potentials (APs) from a canine right ventricular wedge; (b) plot of epicardial AP notch and J wave amplitude across a range of S1-S2 intervals. Epicardial AP notch and J wave amplitudes changed in parallel to changes in S1-S2 intervals; (c) ECG lead V4-V5 recorded from a man with J wave syndromes; (d) a J-wave-like deflection at the terminal portion of the QRS in a patient with intraventricular conduction delay.

Figure 4

Cellular basis for “downslope ST segment elevation.” Transmembrane action potential (AP) recording in a canine ventricular wedge showing markedly deep and prolonged epicardial (Epi1 and Epi2) but not endocardial (Endo) AP notch reflected on a transmural electrocardiogram as a “downslope ST segment elevation” (arrow) followed by T inversion. The “downslope ST segment elevation” is, in fact, a giant J wave.

Figure 5

J wave and ventricular fibrillation (VF) via phase 2 reentry. (a) VF in a patient with J wave in lead II, note the larger amplitude of J wave in the beat preceding VF, following a longer R-R interval; (b) phase 2 reentry predisposing to VF in a canine right ventricular wedge preparation in the presence of the K⁺ channel opener pinacidil. Loss of action potential dome in Epi1 but not Epi2 caused propagation of the dome at Epi2 to Epi1, that is, phase 2 reentry (solid arrows), which manifested a short-coupled R-on-T beats (open arrows) capable of triggering VF.

Figure 6

(a) Hypothermia-induced J wave in humans. Appearance of prominent J (Osborn) wave on electrocardiogram of a 32-year-old female at 32°C (left panel) and abolishment of J wave by rewarming at 36.3°C (right panel); (b) hypothermia-induced J wave in animal experiments.