A Study on QT Dispersion before and after Thrombolysis in Acute Myocardial Infarction and its Prognostic Implications: A before and after Comparison Study.

Introduction: Acute myocardial infarction (AMI) stands as one of the most catastrophic occurrences in the progression of coronary artery disease. Measuring QT dispersion (QTd) is a fairly straightforward and noninvasive technique for predicting mortality in patients at high risk following a myocardial infarction (MI). Objective: To measure the QT, corrected QT interval (QTc), QTd, and corrected QT dispersion (QTcd) intervals before and after thrombolysis in patients with AMI and to determine prognostic implications of QTd in AMI. Materials and methods: This was a before and after comparison study conducted in the intensive care unit (ICU) of a tertiary care center in Central India. It was carried out in patients with AMI [ST-elevation myocardial infarction (STEMI)] who underwent thrombolysis in ICU. A total of 160 participants were enrolled over the time period of 24 months using the convenience sampling technique. Results: The most prevalent (68 patients) risk factor among MI patients was hypertension (HTN). QT parameters such as QT, QTd, and QTcd showed significant statistical variation of p-value < 0.0001 when compared at admission and after thrombolysis. No significant difference (p > 0.05) in QT parameters at admission (QTd, QTc, and QTcd) between anterior and inferior wall MI, except for QT interval (p = 0.0010). Among the 33 patients who experienced arrhythmia, ventricular tachycardia was the most prevalent arrhythmia in 22 patients (13.75%). There was a significant statistical correlation between the arrhythmic event and the outcome of the patient (p < 0.0001). Patients who died had higher QT parameter values at admission, and these remained on the higher side even after thrombolysis, whereas those who got discharged had lower QT parameter values at admission, and their values decreased after thrombolysis. Conclusion: Successful thrombolysis significantly decreases the QTd and thereby the arrhythmogenic potential, and thus can also be used as a reliable predictor of arrhythmia in patients of MI. How to cite this article: M A, Khandait H, Guralwar C, et al. A Study on QT Dispersion before and after Thrombolysis in Acute Myocardial Infarction and its Prognostic Implications: A before and after Comparison Study. J Assoc Physicians India 2023;71(10):14-18.

A Study on Qt Dispersion before and after Thrombolysis in Acute Myocardial Infarction, and its Prognostic Implications.

Acute myocardial infarction (AMI) represents one of the catastrophic events in the natural history of CAD. Early mortality is attributed to arrhythmic events, mainly VT/VF. Ventricular repolarization time varies for different cells located in diverse regions of the left ventricle, resulting in a regional heterogeneity of repolarization time, which in turn causes QT interval dispersion in various leads of ECG. Increased dispersion of ventricular recovery time is believed to provide a substrate for serious ventricular arrhythmias. QT dispersion measurement is a simple non-invasive method for predicting mortality in high-risk patients after MI. It reflects variations of ventricular repolarization and arrhythmogenic potential. Our study was designed to analyze QT dispersion variation in patients of AMI, the effect of thrombolysis on QT dispersion and assess its prognostic implications. MATERIAL: A before and after comparison study was conducted, including 160 patients of AMI who received thrombolytic therapy. Relevant clinical data was collected. A 12-lead ECG was recorded at the time of admission and a repeat ECG was taken 1 hour after thrombolysis. QT interval was measured manually from the onset of QRS complex to the end of T wave. The patients admitted were followed up for a minimum five days of their hospital stay for assessing the outcome. Occurrence of sustained VT, VF, VPC or sudden death was considered to be an arrhythmic event. OBSERVATION: In patients who experienced arrhythmia, QTcd was 0.07±0.06 sec at admission and 0.04±0.03 sec after thrombolysis (p=0.0227). Among patients who did not experience any arrhythmia, QTcd was 0.04±0.03 sec at admission and 0.02±0.03 sec after thrombolysis (p= <0.0001). Thus, patients who experienced arrhythmia had higher QT dispersion at admission and it remained on the higher side even after thrombolysis, probably due to failed reperfusion, in contrary to those without arrhythmia. There was a significant statistical correlation between arrhythmic event and outcome of a patient (p<0.0001). QTcd showed significant statistical correlation after thrombolysis in predicting the outcome of MI patients (p=0.0120) with median (IQR) QTcd of 0.01(0-0.09) in discharged patients and 0(-0.09-0.03) in patients who expired. CONCLUSION: Successful thrombolysis was associated with lower QT dispersion on ECG in patients of AMI. Our data supported the hypothesis that QT dispersion after MI depends on reperfusion status. Reduction in QT dispersion maybe a mechanism of benefit of thrombolytic therapy. QTcd reflects the amount of dispersion of refractoriness associated with the scarred myocardium, which is a marker of future arrhythmogenicity.