Assessment of QT Dispersion in Patients with Acute STEMI Receiving Thrombolytic Versus those Performing Primary Percutaneous Coronary Intervention (PCI) Therapy

Background: ECG is a necessary tool for the diagnosis of myocardial infarction and cardiac arrhythmia. The QT interval reflects the duration of ventricular electrical activity, determined by the phases of depolarization and repolarization. QT dispersion (maximum QT interval minus minimum QT interval) was originally proposed as an index of the spatial dispersion of ventricular recovery times. Aim of the Study: This study was carried out aiming to compare QT dispersion in patients presenting with STEMI and treated with thrombolytic therapy versus those treated with PCI therapies. Subjects and Methods: The study was carried out at Cardiology Department in Specialized Medical Hospital, Mansoura University from January 2014 to January 2015. Approval to conduct this study was obtained. Also, written consents were obtained from the patients to participate in the study. The study was conducted on 50 patients presented with acute STEMI. Patients were divided into two groups depending on the reperfusion strategy. First group included 25 patients treated with thrombolytic therapy. The second group included another 25 patients treated with PCI therapies. All patients were interviewed using a specially designed questionnaire. Furthermore, anthropometric measurements and laboratory investigations were done. QT intervals of the studied patients were manually calculated at admission (before treatment) and in 24 hours (after treatment). The population enrolled in this study was composed of 35 male patients and 15 female patients with age range between 25 and 75 years. Diabetic patients constituted 56% of the studied sample, whereas patients having hypertension represented 46% of the studied sample. 60% of the studied patients were smokers and dyslipidemia was present in 66% of the studied sample. Results: Most patients studied were males, diabetic, smoker, and dyslipidemic. Mean age of female patients (54.09+9.35 years) was more than that of male patients (57.47+9.53 years). Patients presented with anterior STEMI were more than those presented with inferior STEMI. There were a significant reduction in QT and QTc dispersions before and after reperfusion regardless of reperfusion strategy (p 0.001 and 0.001 respectively). There were non-significant reduction in QT and QTc dispersions before and after thrombolytic therapy (p=0.147 andp=0.097 respectively), however, there were significant reduction in QT and QTc dispersions before and after PCI therapies (p 0.001 and p 0.001 respectively). Our study revealed higher significant reduction in QT and QTc dispersions after PCI therapies than after thrombolytic therapy (p=0.005 andp=0.005 respectively). There were nonsignificant differences in QT and QTc intervals and dispersions before reperfusion according to the site of the infarction (p=0.765 andp=0.0801 respectively). QT maximum and QT minimum were significantly higher in patients with inferior STEMI than those with anterior STEMI after reperfusion (p=0.046 and 0.015 respectively). Conclusion: Primary PCI is associated with higher significant reduction in QT and QTc dispersion than thrombolytic therapy. So it will be associated with lower incidence of ventricular arrhythmias. Recommendations: We recommend future larger studies that involve automatic measurements of QT interval which will increase the accuracy of the results to compare different Coronary reperfusion strategies.