Conduction Disturbances in Acute Myocardial Infarction in a series of 250 cases

INTRODUCTION: Coronary artery heart disease (CAHD) is a disease with multiple causes. It is a disorder with wide and variable spectrum of clinical features. Ubiquitous in distribution, it is a complex interaction of genetics, environmental factors and life style. The prevalence of CAHD in India is high and the case burden is rising every years. Myocardial infarction continues to be a major health problem. About 50% of death from acute myocardial infarction occur within 1 hour of the event and are attributable to arrhythmias. Ischemic injury can produce conduction block at any level of the atrioventricular or intraventricular conduction systems. The various risk factors causes micro and macrovascular pathology. The possible mechanisms being dyslipidemia, enhanced atherosclerosis, hypertension and diabetic macroangiopathy. There are reports showing higher incidence of involvement of conduction tissue of heart in diabetes mellitus. Sinus node disorder in diabetes is mostly a manifestation of diabetic autonomic neuropathy. Hypertension causes an increase in left ventricular mass and fibrous tissue resulting in increased stiffness of the left ventricle leading possibly to reduced coronary reserve, silent myocardial ischemia, and abnormal electrophysiological properties of hypertrophied myocytes and conduction disturbances. This study is performed to estimate the prevalence of conduction blocks by electrocardiogram in a series of 250 cases of myocardial infarction with respect to various risk factors and outcome. AIMS OF THE STUDY: 1. To study the incidence of isolated conduction disturbances [without arrhythmias] in acute myocardial infarction in a series of 250 cases admitted in ICCU, Stanley Medical College, Chennai. 2. To study the incidence of conduction disturbances with age and sex distribution and various risk factors. 3. To study the mortality and poor prognosis due to the incidence of conduction disturbances in acute myocardial infarction. METHODOLOGY: 250 patients admitted with acute myocardial infarction in intensive coronary care unit from January 2010 were taken up for this study. Detailed history was taken and thorough clinical examinations was done as per the proforma given here with enough and available investigations in this hospital to confirm the diagnosis. Inclusion Criteria: All ST elevation myocardial infarctions. Exclusion Criteria: Preexisting conduction blocks and tachyarrhythmias with functional conduction blocks and old myocardial infarctions. RESULTS: 250 Patients of acute myocardial infarction were included in this study. They consisted of 167 male and 83 female patients. The youngest patient was a 23 year old male and the oldest patient was an 84 year old female. Out of 250 patients with acute MI, 51 patients had heart blocks. The maximum incidence of MI is in the age group of 41 to 50 years. In this study the heart blocks are more common in the age group of 31 to 40 years. Out of 250 patients 167 were male and 83 females. Out of these 33 males and 18 females had heart blocks. It is found that among various risk factors diabetic patients had the highest percentage of heart blocks followed by alcoholics and patients with high cholesterol. The incidence of AWMI is more than IWMI. The incidence of AWMI was 58.8%and that of IWMI was 41.2%. RBBB is the most commonly occurring Intraventricular conduction defect (43.6%). The number of AV blocks is 5 in AWMI and 7 in IWMI. Out of 250 patients with acute MI 39 had intraventricular conduction defect, out of which 25 occurred in patients with AWMI and 14 in patients with IWMI. The total mortality is 10.4% of all patients with acute MI. The number of deaths is high in AWMI when compared to IWMI. The mortality among patients with heart block is 69.2% and patients without heart blocks is 30.8% The mortality among patients with third degree heart block and bifascicular block is 50% and that of RBBB is 47%. The mortality is highest in third degree AV blocks.. The mortality rate is 50% in bifasicular blocks, 30.7% in left bundle branch blocks, and 28.5% in left anterior fasicular blocks. CONCLUSION: 1. The incidence of heart blocks in acute MI is 20.4 %. 2. The distribution of heart blocks is almost equal in both sexes. 3. Heart blocks are more common in the age group of 31 to 40 years. 4. The incidence of heart blocks in diabetes mellitus and alcohol are high (28.4% and 23.5% respectively). 5. AV blocks are more common in IWMI. 6. Most of the IVCD occur in patients with AWMI. 7. RBBB is the most common IVCD with incidence of 43.6%. 8. Mortality is high in patients with third degree AV block and bifasicular block