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.
Keywords: J wave; early repolarization; right bundle branch block; ventricular conduction delay.
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