High frequency qrs electrocardiography in the detection of reperfusion following thrombolytic therapy

Abstract

Summary:The hypothesis that an increase in the amplitude (root-mean-square voltage) of the high frequency ( 150-250 Hz) components of the QRS complex occurs with successful reperfusion following thrombolytic therapy in acute myocardial infarction (AMI) and fails to occur when thrombolysis fails was tested. Clinical markers for successful or failed reperfusion following thrombolytic therapy for AM1 are notoriously insensitive. The amplitude of the high-frequency components of'the QRS complex decreases during ischemia and returns to normal with resolution of ischemia, but neither the variability in measurement of these potentials nor their patterns of change during the course of AM1 have been described. In 32 control subjects, the average coefficient of variation for the amplitude of the highfrequency QRS complex was 10% or 0.3 uV. Based on these data, for the acute infarction population a significant change in this measurement was therefore defined as a change in amplitude > 20% or 0.6 UV on two consecutive recordings. In 30 patients with AM1 treated with a thrombolytic agent, either cardiac catheterization, serial serum myoglobin, or complete resolution of ST-segment elevation were used to define successful or failed reperfusion. High-frequency QRS electrocardiograms were obtained at the start of treatment with a thrombolytic agent and for 3 h thereafter using a signal-averaging technique and digital filtering. Standard 12-lead electrocardiograms were obtained at the same time. In patients who reperfused successfully, the high-frequency QRS amplitude increased significantly (1.2 ? 0.9 UV above its nadir at 83 ? 36 min after initiation of thrombolytic therapy) in 23 of 25 patients. In contrast, the highfrequency QRS amplitude did not change or declined in all five patients who failed to reperfuse (-0.4 k 0.4 uV, p < 0.05 compared with successful reperfusion). Traditional clinical markers such as resolution of chest pain and ST-segment elevation failed to distinguish successful and failed reperfusion. High-frequency QRS electrocardiography is a rapid, reliable bedside technique for discriminating between successful and failed reperfusion in patients treated with thrombolytic agents for AMI.

High-frequency electrocardiogram as a supplement to standard 12-lead ischemia monitoring during reperfusion therapy of acute inferior myocardial infarction

“…Previous studies have indicated that reperfusion in patients with acute MI is accompanied by an increase in HF-QRS (15,16). The results of the present study support these previous findings.…”

“…The criterion described by Dissmann et al was used for the STsegment analysis: an ST-elevation resolution ≥ 50% after 1 hour of therapy was taken as an indication of early reperfusion (22). A change in HF-QRS exceeding 0.6 µV was considered significant (15). These cut-off values were also used for the comparison after 2 and 4 hours of recording.…”

“…Studies during thrombolytic therapy, using few electrocardiographic leads, in patients with acute MI suggest that analysis of the HF-QRS also may have the ability to detect reperfusion (15,16). In these studies, reperfusion was accompanied by an increase in HF-QRS.…”

Evaluation of depolarization changes during acute myocardial ischemia by analysis of QRS slopes

“…Some of these changes are considered to represent already necrotic areas (Q waves), but other, potentially reversible changes in the QRS complex also appear, although they are less well understood and are usually not considered for clinical decision making. Earlier studies on depolarization changes during ischemia due to acute coronary occlusion have considered QRS prolongation (1)(2)(3)(4)(5), amplitude changes of the R-and S-waves (4,6,7), "distortion" of the terminal part of the QRS complex (8)(9)(10)(11)(12) as well as changes in the high-frequency components of the QRS complex (13)(14)(15).…”

Intra-QRS spectral changes accompany ST segment changes during episodes of myocardial ischemia

“…These ischemia-related depolarization changes in the ECG are difficult to appreciate in time domain, but produce potentials with frequency content ranging from 40 to 250 Hz. Changes in this range have been demonstrated in various models of ischemia in preclinical and clinical settings[4–11]. However, the mode of detection, magnitude, direction, and frequency range of these changes have varied widely depending on the experimental and clinical conditions, with much attention devoted to the diminution of potentials seen using HFQRS analysis (in the range above 140 Hz)[12].…”