A Study On Qt Dispersion And Thrombolytic Therapy In Acute Myocardial Infarction

Abstract

INTRODUCTION : Myocardial infarction is a common presentation of ischemic heart disease. Ischemic heart disease is the leading cause of death in developed countries, but third to AIDS and lower respiratory infections in developing countries. In India, cardiovascular disease (CVD) is the leading cause of death. The deaths due to CVD in India were 32% of all deaths in 2007 and are expected to rise from 1.17 million in 1990 and 1.59 million in 2000 to 2.03 million in 2010. Although a relatively new epidemic in India, it has quickly become a major health issue with deaths due to CVD expected to double during 1985-2015. [ Mortality estimates due to CVD vary widely by state, ranging from 10% in Meghalaya to 49% in Punjab (percentage of all deaths). Punjab (49%), Goa (42%), Tamil Nadu (36%) and Andhra Pradesh (31%) have the highest CVD related mortality estimates. State-wise differences are correlated with prevalence of specific dietary risk factors in the states. Moderate physical exercise is associated with reduced incidence of CVD in India (those who exercise have less than half the risk of those who don't). CVD also affects Indians at a younger age (in their 30s and 40s) than is typical in other countries. QTc dispersion is an important marker that reflect variations of ventricular repolarisation and arrythmogenic potential. This study is based on various studies suggesting significant reduction in QTc dispersion after thrombolytic therapy in acute myocardial infarction. AIMS OF THE STUDY : 1.To calculate the QT, QTc, QTd, QTcd in all patients with acute myocardial infarction. 2. To determine the difference of QT parameters in patients treated with thrombolytic agents(streptokinase) against those not treated with thrombolytic agents(streptokinase). MATERIALS AND METHODS : 102 patients admitted in KAPV Government Medical College Hospital, Tiruchirapalli for Acute Myocardial infarction were taken up for the study. All patients were followed for a period of 8±2 days during their stay in the hospital. The study group was chosen taking into consideration of the following criteria: INCLUSION CRITERIA : 1. Acute Myocardial infarction • Chest pain >30 minutes, • Chest pain not relieved by rest or nitrates, • ST elevation >1mm or 0.1mv in ≥2 limb leads ST elevation >2mm or 0.2mv in ≥ 2 precordial leads, • NSTEMI. 2. Treatment with Thrombolytic therapy (streptokinase) / without Thrombolytic therapy EXCLUSION CRITERIA : 1. The contraindications for thrombolytic therapy for those patients who were treated with thrombolytic therapy. 2. Drugs affecting QT interval eg. Quinidine, procainamide, tricyclics & tetracyclics depressants, astemizole, digitalis. 3. Hypertrophic cardiomyopathy, Acute carditis. 4. Atrial fibrillation, Bundle branch blocks. 5. Prior coronary bypass surgery. 6. Serum potassium 5.0mmol/l. 7. Congenital long QT Syndromes. METHODS : In Patients admitted for Acute Myocardial infarction, a standard 12 lead ECG was taken at paper speed of 25 mm/s at admission and before discharge(day 8±2).From these ECG’s taken in all 102 patients the following parameter were calculated. RESULTS AND OBSERVATION : 1. Composition of the Study Population : A total of 102 patients were taken up for the study. Of these 56 patients were treated with thrombolytic therapy and 46 patients were not treated with thrombolytic therapy. There were 92 males (90%) and 10 females(10%),Anterior wall infarction constituted 49%,extensive anterior 10% and inferior wall 41%.There were only 6 patients with NSTEMI. 2. Age and QT parameters : The QT parameters were correlated among different age groups. The QT parameters showed significant variation between the patients treated with thrombolytic therapy and not treated with thrombolytic therapy, in age groups 40-49,50-59,60-69.The other age groups did not show significant statistical variation, as the number of patients was small. 3.QT parameters and Thrombolysis and Site of Infarction. The QT parameters were correlated among study groups and it was found that there was significantly greater reductions in QT parameters at day 8±2 in patients treated with thrombolytic therapy when compared with not treated with thrombolytic therapy. It was noted that anterior wall infarction show significantly greater QT, QTc dispersions when compared with inferior wall infarction. These differences in the QT parameters were all statistically significant. CONCLUSION : 1. There were significantly greater mean QT, QTc dispersions in the early hours of Acute Myocardial infarction. 2. Patients with anterior acute myocardial infarction showed significantly greater QT parameters when compared with inferior acute myocardial infarction patients. 3. There were significantly greater reduction in QT, QTc dispersions after treatment with streptokinase than without it. 4. QT, QTc dispersions are greatest in the early hours of acute myocardial infarction and fall with time and successful thrombolysis 5.These results can be taken into account in the risk stratification for malignant ventricular tachyarrhythmia’s and they are another evidence for the benefit of thrombolytic therapy in patients with acute myocardial infarction.