High-Frequency ECG in Ischemic Heart Disease

Sammanfattning: Analysis of high-frequency QRS components (HF-QRS) is one of the emerging methods for increasing the diagnostic performance of the electrocardiogram (ECG). The overall objective of the thesis is to investigate whether analysis of HF-QRS has the ability to provide information about ischemic heart disease and so serve as an adjunctive diagnostic tool in several clinical situations. Investigation of the basic properties at rest of the HF-QRS showed large individual variations, in patients both with and without previous myocardial infarction. Analysis of HF-QRS therefore cannot differentiate between patients with and without previous infarction. During acute myocardial ischemia evoked by prolonged percutaneous transluminal coronary angioplasty, there were significant changes in HF-QRS. The changes in HF-QRS were compared with the ST-segment deviations in the standard 12-lead ECG. The sensitivity for detection of coronary-artery occlusion was higher for HF-QRS than for ST-segment elevation. The changes in HF-QRS during ischemia were distributed among many leads regardless of which artery was occluded. High-frequency analysis thus probably is not as useful as standard ECG for localization of ischemia. Analysis of HF-QRS could provide an adjunctive tool to detect ischemic heart disease. The large individual variations in HF-QRS probably make high-frequency analysis most applicable in monitoring situations when it is possible to identify changes from baseline, such as during thrombolytic therapy, during unstable angina, and in conjunction with exercise testing.