QT interval dynamics in patients with ST-elevation MI

Abstract

Background: An association between excessively prolonged QT and ventricular arrhythmia in patients with ST-elevation myocardial infarction has been described; however, the QT dynamics, characterization, and long-term predictive value are not well known.

Objective: To characterize QT interval dynamics in patients undergoing ST elevation myocardial infarction (STEMI) and determine its association with mortality.

Methods: A retrospective analysis of 4,936 consecutive patients, hospitalized for STEMI between 01/2013-12/2021. Patients with less than three electrocardiograms (ECGs) during index hospitalization were excluded. Baseline demographics, cardiovascular history, clinical risk factors, treatment measures, laboratory results, and mortality data were retrieved from the hospital's electronic medical records.

Results: We included 1,054 patients and 5,021 ECGs in our cohort with a median follow-up of 6 years [interquartile range (IQR) 4.3-7.4 years]. The QT was longer in women in comparison to men (428.6 ms ± 33.4 versus 419.8 ms ± 32.52, P-value = 0.001). QT prolongation was greater in females, elderly patients, and patients with STEMI caused by occlusion of the left anterior descending (LAD) coronary artery. We determined QT cutoff to be 445 ms. This value of QT divided our cohort upon arrival into a long QT group (217 patients, 26% of the cohort) and a "normal" QT group (835 patients, 74% of the cohort). The long QT group experienced an increase in combined short and long terms all-cause mortality. The QT upon arrival, on day 2 of hospitalization, and before discharge from the hospital, correlated with long-term mortality.

Conclusion: QT duration is often prolonged during STEMI; this prolongation is associated with increased mortality and adverse events. Gender is an important mediator of QT dynamics.

Keywords: QT; STEMI; all-cause mortality; dynamics; gender.

FIGURE 1

QT dynamics during hospitalization. QT interval prolongs during the initial 3 days past myocardial infarction (MI), and then starts shortening, but without returning to the baseline values.

FIGURE 2

Difference in QT interval dynamic between men and women. In men, consistently longer QT intervals were associated with mortality. This dynamic and associated mortality difference is not seen in women. **Statistical significance with a P-value of <0.01.

FIGURE 3

Survival curves for long or normal QT groups based on ECGs upon arrival (A), day two of hospitalization (B), and the ECG before discharge (C). Interestingly, longer QT intervals are associated mainly with long-term mortality and may reflect overall health. Lower panel, number of patients at risk each day.

FIGURE 4

Multivariate Cox analysis. HR, hazard ratio; CI, confidence interval; IRA, infarcted related artery; LCX, left circumflex; RCA, right coronary artery. *Based on ECG upon arrival. ***Statistical significance, with a P-value <0.001.