Abstract
Background: Cigarette smoking is one of the prime contributing factors for atherosclerosis. Chronic cigarette smoking causes disturbances in the electrophysiology of heart and may lead to ventricular arrhythmias. Furthermore, cigarette smoke produces oxidative stress by generating free radicals which is responsible for lipid peroxidation and atherosclerosis.

Aims and Objectives: The present study is aimed at evaluating the electrocardiographic (ECG) changes and plasma malondialdehyde (MDA) levels in smokers suffering from ischemic heart disease (IHD).

Materials and Methods: About 327 male subjects, consisting of 127 healthy subjects and 200 consecutively admitted IHD patients were enrolled for this study and were subsequently divided into two subgroups as smokers and non-smokers consisting of 100 non-smokers and 100 smokers, based on the history of smoking. The healthy control group consisted of 64 smokers and 63 non-smokers. All the subjects underwent ECG recording and evaluation of plasma MDA levels.

Results: 68% of IHD patients had typical ST elevation type of ECG, and out of these, 74% were smokers and 62% were non-smokers. The analysis of normal ECG waves of control group indicated significantly shortened QRS complex (P < 0.001) and shortened ST interval (P < 0.001) in smokers than non-smokers. The plasma MDA levels were observed to be highly significant (P < 0.001) in control smokers and patient smokers in comparison to control non-smokers and patient non-smokers, respectively.

Conclusion: In chronic healthy smokers, the QRS complex and ST segment were found to be shortened indicating incomplete ventricular relaxation indicating that the smokers are at higher risk for greater myocardial damage. Furthermore, the greater lipid peroxidation indicated by higher MDA levels in smokers irrespective of the presence of IHD predisposes them to higher risk of atherosclerosis and higher mortality from IHD.

Key words: Electrocardiogram; Smoking; Ischemic Heart Disease; Lipid Peroxidation