Correlation between corrected QT dispersion and left ventricular systolic and diastolic function in patients with first acute myocardial infarction

Abstract

Background: QT interval is attracting the interest of many investigators. In the last two decades, lengthening in the QT interval has been felt to be associated with electrical instability and Sudden Cardiac Death (SCD). The QT interval is an indirect measure of the duration of action potential depolarization and repolarization of the ventricles. Aim of the study: The goal of the present study is to correlate between QTc dispersion obtained from standard surface 12 lead ECG and left ventricular systolic and diastolic function obtained from transthoracic echocardiography in the setting of acute STEMI promptly after presentation and prior to revascularization. We also aim to evaluate how accurate is the QTc dispersion as an ECG index in predicting LV function after acute STEMI. Results: There was a statistically significant difference between patients who developed ventricular arrhythmias-prior to reperfusion strategy-and those who did not suffer ventricular arrhythmias regarding QTcD (p<0.001). Mean QTcD in ventricular arrhythmia group was much higher than that in non-arrhythmia group (125.26 ± 28.73 msec. vs. 73.41 ± 23.9 msec.). Also, a strong negative correlation (r=˗0.772) between LVEF and QTcD (p<0.001). Moreover, by correlating LV systolic function with QTcD using logistic regression model, QTcD was a good predictor of LV systolic function. Significant positive correlation (r=0.536) between QTcD and the grade of LV diastolic dysfunction (p<0.001). 88.6% of prolonged QTcD patients had impaired diastolic function in comparison to 53.3% of normal QTcD patients. There was a statistically significant relationship when associating age of STEMI patients with LV diastolic function (p<0.001 vs. p=0.06). Patients with normal diastolic function had a mean age 48.55 ± 13.69 while those with restrictive diastolic pattern had a mean age 66.4 ± 5.98 years. There was a statistically significant weak positive correlation between duration of hospital stay in days and value of QTcD (r=0.24, p=0.016). Conclusion: The present study concluded that, given the ready availability of ECG, QTc dispersion is an important non-invasive electrocardiographic indicator that is highly correlated with LV systolic and diastolic function in the setting of acute STEMI. It is also an important independent predictor of LV systolic function in such patients.