Acute coronary artery occlusion is detected with higher sensitivity using high-frequency QRS analysis compared with conventional assessment of ST segments. This result suggests that analysis of HF-QRS could provide an adjunctive tool with high sensitivity for detecting acute myocardial ischemia.

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The purpose of this study was to determine the changes in high frequency QRS components during acute myocardial ischemia and to compare these changes with ST deviations in the standard ECG. Signal-averaged high resolution ECGs were obtained prior to and during percutaneous transluminal angioplasty (PTCA) in 17 patients. The QRS complexes were analysed within a bandwidth of 150-250 Hz. The amplitudes of the filtered QRS were expressed as root mean square (RMS) values. During inflation there were signijicant ST deviations in 13 patients: the RMS values decreased in 16 patients. The correlation between the maximal ST elevation and the maximal decrease in RMS in any lead was r = -0.59. Acute coronary artery occlusion produces changes in high frequency QRS components, even in the absence of ST segment deviation in the standard ECG. IntroductionClinical decisions in patients with suspected myocardial ischemia are often based on assessment of the ST segments in the standard 12-lead ECG. Previous studies have shown changes also in the QRS complex during acute myocardial ischemia, both in standard [l] and in high frequency (150-250 Hz) recordings [2-41. It is therefore of interest to investigate if the analysis of high frequency QRS components could add information to that available from the ST segment in the standard ECG.The present study, in patients with balloon occlusion of either branch of the left coronary artery, was performed to:1) determine the changes in high frequency QRS components during prolonged PTCA in man and 2) compare the changes in high frequency QRS components with the ST segment deviation in the standard 12-lead ECG. Methods Study PopulationPatients receiving elective prolonged PTCA of the left anterior descending coronary artery (LAD) or the left circumflex coronary artery (LCX) at the Charleston Area Medical Center, WV, were considered for this study. Inflation of the intra-coronary balloon was maintained for 5 minutes whenever clinically feasible. A data form indicating the exact duration and anatomic site of all balloon inflations was completed. Patients with signs of previous myocardial infarction or QRS duration more than 120 ms (apparent on a control standard ECG recorded prior to the procedure) were not included. A total of 34 patients were considered for inclusion in the study. The locations of the balloon inflations were LAD (23) and LCX (1 1). 2.2, ECG AcquisitionHigh resolution ECGs were recorded using equipment by Siemens-Elema AB, Solna, Sweden. Recordings from nine leads were obtained, Vl-V6, I, 11, and 111. The leads aVL, -aVR, and aVF were later calculated using the standard leads I, 11, and 111.The standard electrode placements were used for the precordial leads. Proximal electrode placements were used for the limb leads in order to reduce noise from skeletal muscle. The signals were digitized at a sampling rate of 1000 Hz with an amplitude resolution of 0.6 pV and stored on a PC hard disc for further analysis.A control ECG recording was continuously acquired for 5 minutes in the...