Study of QRS duration and R/Q Ratio in the Assessment of Severity of Acute Myocardial Infarction

INTRODUCTION: Within a short span of time, Ischaemic Heart Disease (IHD) will be the number one killer replacing infections, silently, slowly sometimes suddenly occluding the coronaries of millions of Indians. WHO study group on IHD and atherosclerosis described ischaemic heart disease as “cardiac disability, arising from reduction or arrest of blood supply to the myocardium in association with disease process in coronary arterial system”. During the past 30 years, a large decline in mortality due to coronary artery disease has been experienced in the West and there is a substantial increase in the developing countries. IHD accounted for 15.3 million deaths in 1996 which included 45.6% of all deaths in developed countries and 24.5% of all deaths in the developing countries. Estimated and projected rates of death (per l,00,000) due to this dreaded disease by World Bank Health Sectoral Priorities Review are 295 and 239 for males and females respectively in the year 2015. Coronary artery disease has a multifactorial etiology with many of the risk factors being influenced by life style. Rapid change in dietary habits coupled with decreased physical activity in India as a consequence of urbanisation may partly explain the escalation of coronary artery disease. India is at going through a phase of rapid urbanization which has led to economic improvement, the consequence of which has resulted in fast food intake and tobacco consumption and decreased physical activity. AIMS AND OBJECTIVES: 1. To study the “QRS duration” on short term prognosis of acute myocardial infarction. 2. To study the QRS duration in relation to 10-day hospital mortality. 3. To study R/Q ratio in lead II for the assessment of the severity of acute inferior wall myocardial infarction. 4. To study the R/Q ratio in lead II in relation to thrombolytic therapy in acute inferior wall myocardial infarction. 5. To study the comparison of R/Q ratio with QRS duration to assess the severity of acute inferior wall myocardial infarction. MATERIAL AND METHODS: The study was carried out on 75 patients admitted in ICCU of Department of Medicine, Government Royapettah Hospital, Kilpauk Medical College, Chennai-10. Selection Criteria: In this study 75 cases of both sexes of more than 20 years of age with first episode of myocardial infarction, typical chest pain of more than 30 minutes, onset of symptoms within previous 6 hours, at least 0.2 mv ST segment elevation in two or more contiguous precordial leads or at least 0.1mv ST segment elevation in two or more leads were included. The screening criteria for the identification of the presence of myocardial infarction were: • Inferior criterion: Q>30 msec in lead aVF • Anterior criteria: A Q or R< 0.1 mv and < 10 m sec in V2. Exclusion Criteria: Patients with ECGs showing evidence of LBBB, RBBB, LAHB, LVH, old myocardial infarction, preexicitation syndrome were excluded from the present study. All cases were subjected to following examination. Case number, registration number, father/husband name, age, sex, socioeconomic status and rural urban background etc. Presenting complaints with duration were noted in detail such as chest pain, its site, duration and radiation, accompanying features like sweating, nausea, vomiting, syncope, breathlessness, palpitation, oedema, abdominal distension, right hypochondrial pain and other atypical symptoms. Detailed symptomatology of clinical presentation was sought with special reference to onset, duration, intensity, relationship to circadian and seasonal rhythm of symptoms. SUMMARY: The present series “Study of QRS Duration and R/Q Ratio in the Assessment of Severity of Acute Myocardial Infarction” was carried out on 75 patients admitted in the ICCU of Department of Medicine, Government Royapettah Hospital, Kilpauk Medical College, Chennai -10. For the study of “QRS Duration” in the severity of myocardial infarction (both AWMI and IWMI) patients were divided into 3 groups. Group A With QRS duration < 0.09 Sec. Group B With QRS duration 0.09 - 0.11 sec (intermediate QRS prolongation) Group C With QRS duration > 0.11 sec (Significant QRS prolongation) For the study; patients of inferior wan myocardial infarction were divided into groups according to “R/Q ratio” in lead II on 3rd day. Group I Includes patients of IWMI with R/Q ratio> 2 Group II Includes patients of IWMI with R/Q ratio 1- 2 Group III Includes patients of IWMI with R/Q ratio < 1 The patients were selected after application of the following exclusion criteria - patients with ECGs, showing evidence of LBBB, RBBB, LAHB, LVH, old myocardial infarction, pacemaker dependence. CONCLUSION: The present study shows that the estimation of QRS duration in patients of acute myocardial infarction offer important indirect quantitative information regarding the severity and extent of myocardial infarction. A QRS duration of > 0.09 sec predicts more incidence of arrhythmia, heart failure and other complications. This study shows that both intermediate QRS prolongation (0.09 - 0.11 see.) and significant QRS prolongation (> 0.11 sec) is an eye-opener to worse short term prognosis of myocardial infarction. The current study also concludes that QRS duration < 0.09 seconds is indicative of a relatively benign short term outcome. The present study also shows that the estimation of the R/Q ratio in lead II of patients with IWMI offers important indirect information regarding the severity and extension of the myocardial damage. An R/Q ratio of > 2 predicts mild localised LV involvement with good global LV function and good clinical course. An R/Q ratio of between 1 and 2 predicts a greater degree of local asynergy and reduced LV function, but still a good clinical outcome. Finally, R/Q ratio of < 1 predicts severe inferior wall asynergy with reduced LV function and complicated clinical course. Current study also indicates that successful thrombolytic therapy will prevent the extent of inferior wall myocardial infarction