Effect of Direct Stent Implantation on QTc Dispersion

QT interval dynamics in patients with ST-elevation MI

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.

Earliest time of change in QT dispersion after stenting in patients with single vessel coronary artery disease

Dispersion of the QT interval (QTd) is a measure of inhomogeneity of ventricular repolarization, and its prolongation may provide a suitable substrate for life-threatening ventricular arrhythmias. The present study was performed to determine the onset time of change in the corrected QT (QTc) interval and QTd in patients with stable angina and single vessel coronary artery disease. Electrocardiograms of 60 patients with successful stenting, obtained 1 h before and 1 h, 6 h, 12 h and 24 h after the procedure were analyzed. The QTc interval, QTc maximum, QTc minimum and QTd were measured. All electrocardiograms were scanned, and then underwent computer-based analysis. There was a significant reduction in the mean QTc interval as early as 12 h after the procedure (from 474±41 ms to 460±31 ms; P<0.001), which persisted to the 24 h follow-up. This was associated with a significant reduction in mean QT maximum (from 496±31 ms to 418±66 ms; P<0.001) and a significant prolongation in mean QT minimum (from 403±21 ms to 444±12 ms; P<0.001) at the same time intervals. Therefore, successful stenting of coronary arteries in patients with single vessel coronary artery disease and stable angina decreases QTd as early as 12 h after the procedure. This phenomenon may be the result of improved regional myocardial circulation, and reduced ischemia. A persistently low QTd in the following months may therefore have prognostic significance, and can be used as a noninvasive marker of stent patency. Further studies are necessary to define the clinical applicability of QTd in the assessment of long-term stent patency in such patients.

[Corrected QT interval prolongation: a new predictor of cardiovascular risk in patients with non-ST-elevation acute coronary syndrome]

INTRODUCTION AND OBJECTIVES

Recently we reported that prolongation of the corrected QT (CTc) interval is an independent risk factor in patients with unstable angina and acute ischemic changes. The aim of this study was to determine the prognostic value of this variable in patients with non-ST-segment elevation acute coronary syndrome who do not exhibit acute ischemic changes on admission ECG.

METHODS

The study included 55 patients with this syndrome. On admission, a standard 12-lead ECG was recorded, the cardiac troponin-T was measured and a TIMI (Thrombolysis in Myocardial Infarction) risk score was calculated. The primary endpoint was the combination of nonfatal acute myocardial infarction, percutaneous or surgical revascularization, and cardiac death up to 30 days after discharge. Two independent investigators measured the QT interval manually and the corrected value was derived using Bazett's formula. In the statistical analysis, the following cut-off points were used: the median TIMI risk score, a cardiac troponin-T level of 0.04 ng/mL, and a QTc of 0.458 s.

RESULTS

Of the 21 patients (38%) who reached the primary endpoint, 17 (81%) had QTc prolongation. Binary logistic regression analysis showed that QTc prolongation was an independent predictor of the combined endpoint.

CONCLUSIONS

This study shows that QTc prolongation is an independent predictor of cardiovascular risk in patients with non-ST-segment elevation acute coronary syndrome but without acute ischemic changes on admission ECG.