Inadequate or lack of oxygen supply to the heart is understood as ischemia that not only damages a healthy heart muscle but also reducing its ability to pump blood efficiently. This situation in extreme and irreversible cases leads to an acute myocardial infarct and therefore warrants an early detection and treatment. Assessment of ischemia and thereby patient monitoring can be studied by the evolution of electrocardiogram (ECG) especially, the ST segment deviation. Auto detection of ischemic ST deviation episodes (ST segment elevation or depression) with fairly good accuracy is an utmost necessity. Generally, ischemic ECG changes can precede the onset of anginal pain and hence, may be a sign of 'silent Myocardial Ischemia'. Therefore, methods that detect early changes in the ECG, possibly indicating the onset of an acute ischemic syndrome are necessary for an early treatment. In this direction Wavelet transform found to be a potential tool for possible early and accurate detection of ischemic heart disease from ECG based on certain characteristic points called PR and ST derived in discrete Wavelet transform (DWT) domain. Accordingly, in this study, Wavelet analysis of ECG of normal, hypertensive, diabetic and ischemic were analyzed and the results are discussed and detailed.