Statistical analysis of body surface electrocardiographic maps in ischemic heart disease

Body surface electrocardiographic mapping is a technique for recording the thoracic electrical potentials generated by the cardiac cycle and transmitted to the body surface. The body surface map emphasizes the spatial distribution of the cardiac electrical potentials rather than the time magnitude relationship of the standard electrocardiogram. The body surface map contains more information than the standard electrocardiogram and in a different format. This thesis addresses the following questions: 1. is the additional information contained in the body surface map of clinical significance in myocardial infarction ? 2. is the display format and thus the application of topographical statistics of clinical benefit in myocardial infarction? 3. is the addition information able to detect coronary artery disease in patients presenting with chest pain ? Detailed analysis of the body surface map in acute inferior wall myocardial infarction predicted the clinical course of the patient, one map pattern being associated with a high mortality and morbidity, giving a guideline to immediate therapy. The area of ST segment elevation corresponds to the the area of eventual Q wave formation in acute inferior wall myocardial infarction. Thus the body surface map may be useful in assessing reperfusion by thrombolytic agents in acute myocardial infarction. In acute anterior wall myocardial infarction the body surface map was diagnostic but only moderately predictive of the eventual outcome. Again the area of ST segment elevation matched the area of Q wave formation and thus the body surface map may be of value in assessing reperfusion. The body surface mapping was unable to differentiate patients with and without coronary artery disease who had normal standard electrocardiograms. The body surface map was useful in differentiating patients with acute or old myocardial infarction from normal patients but did not detect coronary artery disease in the absence of myocardial damage. The information content of the body surface is increased if an accurate inverse transformation can be used to calculate the epicardial potentials in the clinical situation. To prove that epicardial potentials are accurately calculated, comparison of the area of myocardial damage to the calculated epicardial area of ST segment elevation was made using thallium scanning. This demonstrated a good correlation demonstrating that the inverse transformation was accurate. The technique is adding a new dimension to the understanding of the origin of the electrocardiogram. Body surface mapping is an easily performed clinical investigation that adds information in the assessment of the patients with myocardial infarction.