Chronic heart failure (CHF) is a disorder of the heart in which structural and/or functional heart disease impairs the heart's ability to fill with blood or pump it out properly at rest and/or during exercise [1]. The primary complaints in CHF are shortness of breath, ankle swelling, and general fatigue. The associated clinical signs are pulmonary crackles, elevated jugular venous pressure, and peripheral edema. In developed countries, the prevalence of CHF in adults is approximately 1–2% (depending on the definition used) [2,3], and that in people aged ≥70 years is ≥10% [1]. The cumulative 5-year mortality rate of patients with CHF is approximately 50% [4].

The prevalence of early repolarization pattern (ER) on 12‑lead electrocardiograms (ECG) in the general population is 2–46% [[5], [6], [7]]. This wide range may be explained by the different ER definitions used by the different authors. Although ER on ECG has been considered a benign finding for many years, an association has been established between ER on ECG and sudden cardiac death (SCD), mainly through ventricular arrhythmias in previously healthy individuals or those with structural cardiac pathology [6,[8], [9], [10], [11]]. This relationship was first suspected more than two decades ago, and the association between ER and idiopathic ventricular fibrillation (VF) was established 14 years ago; new studies are being conducted to support this relationship [10]. The association of ER on ECG with CHF progression and increased all-cause mortality are being studied [8,9,12]. ER is described as J-point (Jp) elevation with QRS notching or slurring in the terminal part in at least two contiguous inferior (II, III, and aVF) and/or lateral leads (I, aVL, and V4-6) on standard ECG. The J-point amplitude must be at least 1 mm (0.1 mV) and QRS duration should be <120 ms. The Jp must appear as an additional positive wave in the S-wave (QRS notching) or as a faint transition of the high R-wave to the ST segment without J-p-QRS slurring. Anterior precordial leads (V1–3) are not included in the ER description because such changes may be due to Brugada syndrome or right ventricular dysplasia [5,10,13]. The prevalence of ER on ECG in the general population is considerably high in men [14]. The knowledge that ER on ECG predisposes to a higher risk of SCD and to the development and worsening of CHF allows physicians to tailor patient care and follow-up. ECG is a cost-effective, simple, and widely available diagnostic test.

In order to improve the diagnosis and treatment and reduce the financial costs in patients with CHF it is important to identify diagnostic methods that are cheap, effective, preferably non-invasive and have reliable prognostic significance.

This study aimed to evaluate the incidence and prognostic value of ER and to compare its prognostic significance with other non-invasive diagnostic methods (N-terminal pro-B-type natriuretic peptide [NT-proBNP], impedance cardiography [ICG], transthoracic echocardiography [TTE], and 6-min walk test [6MWT]) in patients who were hospitalized due to CHF decompensation. The investigators hypothesized that ER and ICG changes may be used as cost-effective, safe, non-invasive, and widely available diagnostic and prognostic methods in patients with CHF, to help physicians tailor the follow-up and treatment protocol accordingly.