Lower ST levels in electrocardiogram (ECG) lateral leads were found to be independently associated with all-cause mortality, according to a study published in the Journal of Electrocardiology.
Slight ST depression — even slight depressions — on ECG has been linked to cardiovascular disease and poorer outcomes. However, population-level studies in which the prognostic significance of ST-level changes have been examined are lacking, with few studies examining ST slope or ST level as a continuous variable. Investigators sought to evaluate the prognostic role of these parameters in men and women, in 3 separate anatomical lead groups.
In this study based on the Finnish Health 2000 survey, 6354 randomly sampled individuals (56.1% women; >30 years) were enrolled. Study participants had a health examination that included a standard supine 12-lead ECG. The ECG leads were divided into anterior (V1-V4), inferior (II, III, and aVF) and lateral (I, aVL, V5, and V6) groups. ST levels, amplitudes and durations, and ST slope (upsloping, horizontal, or downsloping) were measured in all leads.
The study’s primary outcome was all-cause mortality, assessed over a mean follow-up period of 13.7 and 13.9 years in men and women, respectively (until patient death or the end of 2015).
Patients who died vs survived were older and had more comorbidities at baseline. They also had relatively lower ST levels in all lead groups and a greater percentage of negative ST slopes compared with participants who survived.
In the lateral ECG leads, lower ST levels were found to be associated with all-cause mortality in both men (at J + 80 ms, hazard ratio [HR], 0.64; 95% CI, 0.49-0.84; P =.0002) and women (at J + 80 ms, HR, 0.61; 95% CI, 0.48-0.78; P < .001) after adjustment. The presence of coronary heart disease was not found to affect these findings substantially. There were no significant differences in outcomes based on ST levels in the anterior or inferior lead groups, and ST slope was not found to independently predict mortality in this cohort.
When patients with signs of left ventricular hypertrophy (LVH) on ECG were excluded, lower lateral ST levels were associated with increased and decreased mortality risk in men and women, respectively.
Study strengths include the use of a representative population sample, extended follow-up period, the use of continuous vs categorical ST-level variables that improved sensitivity, inclusion of lead groups, and ease of implementation into clinical practice.
Study limitations include a relatively high mortality rate (due to the long follow-up), questionable significance of borderline results, and lack of information on LVH from echocardiographic or magnetic resonance imaging.
“Lower levels of the ST segment in the lateral lead group as a continuous variable is associated with increased mortality in the general population independently of gender, other cardiovascular risk factors and [coronary heart disease],” noted the authors. They recommended that future research explore the pathophysiology of this phenomenon.
This work was supported by The Doctoral Programme in Medicine and Life Sciences, Faculty of Medicine and Health Technology, Tampere University; Finnish Medical Foundation; Finska Läkaresällskapet; Academy of Finland (grant 322098); Competitive State Research Financing of the Expert Responsibility area of Tampere; Finnish Foundation for Cardiovascular Research; Tampere Tuberculosis Foundation; EU Horizon 2020 (grant 755320 for TAXINOMISIS); and Tampere University Hospital Supporting Foundation.
Istolahti T, Nieminen T, Huhtala H, et al. Long-term prognostic significance of the ST level and ST slope in the 12‑lead ECG in the general population. J Electrocardiol. 2019;58:176-183. doi: 10.1016/j.jelectrocard.2019.12.010