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

OBJECTIVE: This study evaluates depolarization changes in acute myocardial ischemia by analysis of QRS slopes. METHODS: In 38 patients undergoing elective percutaneous coronary intervention, changes in upward slope between Q and R waves and downward slope between R and S waves (DS) were analyzed. In leads V1 to V3, upward slope of the S wave was additionally analyzed. Ischemia was quantified by myocardial scintigraphy. Also, conventional QRS and ST measures were determined. RESULTS: QRS slope changes correlated significantly with ischemia (for DS: r = 0.71, P < .0001 for extent, and r = 0.73, P < .0001 for severity). Best corresponding correlation for conventional electrocardiogram parameters was the sum of R-wave amplitude change (r = 0.63, P < .0001; r = 0.60, P < .0001) and the sum of ST-segment elevation (r = 0.67, P < .0001; r = 0.73, P < .0001). Prediction of extent and severity of ischemia increased by 12.2% and 7.1% by adding DS to ST. CONCLUSIONS: The downward slope between R and S waves correlates with ischemia and could have potential value in risk stratification in acute ischemia in addition to ST-T analysis

Ventricular Depolarization in Ischemic Heart Disease.Value of Electrocardiography in Assessment of Severity and Extent of Acute Myocardial Ischemia.

Background In patients with symptoms compatible with acute myocardial infarction (MI), early triage by ECG in the pre-hospital phase by ST-segment elevation myocardial infarction (STEMI) criteria is important for direct transport of these patients to a regional center for primary percutaneous coronary intervention (pPCI). The time from first medical contact to pPCI should, due to present guidelines, be no longer than two hours. One main determinant of final infarct size (IS), in addition to myocardium at risk (MaR) and time to treatment, is the severity of ischemia, which relates to the rate of progression of the infarction wavefront. Presently, no assessment of severity is made. Patients with severe ischemia may have changes within the QRS complex in addition to ST-T changes, making it possible to identify these high-risk patients. QRS changes are, however more difficult to determine and to quantify correctly as compared to the changes within the ST segment. Aims and methods The overall objective was to increase the understanding of depolarization changes during myocardial ischemia and to evaluate whether these changes have possible clinical implications in patients with acute MI. Different QRS methods are applied in patients during ischemia produced by elective, prolonged PCI as well as during STEMI, and comparisons are made with conventional ECG parameters as well as single-photon emission computed tomography (SPECT) images. Results and conclusions Study I compared the computer-derived high-frequency QRS components (HF-QRS) in patients with and without standard ECG changes indicative of old MI. In contrast to previous findings we found that HF-QRS cannot differentiate between patients with and without old MI. Study II tested the ability of HF-QRS versus conventional ST-segment measurements to detect and quantify myocardial ischemia, as determined by SPECT, in a group of patients undergoing elective balloon PCI. We showed that HF-QRS can provide valuable information both for detecting acute ischemia and for quantifying MaR and its severity. Study III evaluated a potentially more readily available (compared with HF-QRS) new marker of ventricular depolarization distortion, which is based on calculation of up- and downslope within the QRS complex, in patients undergoing coronary intervention that includes temporary occlusion of a coronary artery. We found that in particular the downward slope between R and S waves better correlates with ischemia than conventional QRS parameters, as quantified by SPECT, and thus can be of value in risk stratification of patients with ischemia in addition to conventional ST-segment analysis. Study IV, in a large cohort of STEMI patients, assessed the value of the conventional Sclarovsky-Birnbaum ischemia grading system that includes terminal QRS distortion in addition to ST elevation, on pre-hospital ECG and its dynamic behavior during transport time to the PCI center for prediction of final infarct size and salvage, as estimated by SPECT imaging. The study explored the temporal behavior of the ischemia grading and showed the strong association of ischemia grade assessed from pre-hospital ECG, as well as the dynamic patterns, with infarct size, independent of ST-segment analysis. It also demonstrated the importance of early intervention, which was found to be particularly important in patients who had advanced, QRS-based ischemia grade

Detection and quantification of acute myocardial ischemia by morphologic evaluation of QRS changes by an angle-based method

Objective: In acute myocardial ischemia changes within the QRS complex can add valuable information to that from the repolarization phase. This study evaluates three angles obtained from the main slopes of the R-wave within the QRS complex to assess acute myocardial ischemia. Methods: The QRS angles, denoted by empty set(R) (R-wave angle), empty set(U) (up-stroke angle) and empty set(D) (down-stroke angle), were evaluated in 12-lead electrocardiogram (ECG) recordings of 79 patients before and during coronary occlusion by elective percutaneous coronary intervention (PCI). In a subset of 38 patients, ischemia was quantified by myocardial scintigraphy. Results: At baseline the QRS angles presented low variations. During occlusion, empty set(U) and empty set(D) developed a fast and abrupt change, whereas empty set(R) showed a smaller and gradual change. There were significant correlations between both maximal and sum of positive change in empty set(R) and ischemia: r = 0.67; p < 0:001 and r = 0.78; p <0.001, for extent, and r = 0.60; p < 0.001 and r = 0.73; p <0.001, for severity, respectively. Prediction of extent and severity of ischemia increased by 50% by adding empty set(R) changes to ST-segment changes, for LCX occlusions, whereas increased by 12.1% and 24.6% for LAD and RCA occlusions, respectively. No significant correlation was seen between empty set(u) and empty set(D) angles and ischemia. Conclusions: Evaluation of QRS angles from the standard 12-lead ECG represents a sensitive marker for detection of acute myocardial ischemia, whereas, empty set(R) changes can be used for prediction of its extent and severity. (C) 2013 Elsevier Inc. All rights reserved

Depolarization Changes During Acute Myocardial Ischemia by Evaluation of QRS Slopes: Standard Lead and Vectorial Approach

Diagnosis and risk stratification of patients with acute coronary syndromes can be improved by adding information from the depolarization phase (QRS complex) to the conventionally used ST-T segment changes. In this study, ischemia-induced changes in the main three slopes of the QRS complex, upward (I-US) and downward (I-DS) slopes of the R wave as well as the upward (I-TS) slope of the terminal S wave, were evaluated as to represent a robust measure of pathological changes within the depolarization phase. From ECG recordings both in a resting state (control recordings) and during percutaneous coronary intervention (PCI)-induced transmural ischemia, we developed a method for quantification of I-US, I-DS, and I-TS that incorporates dynamic ECG normalization so as to improve the sensitivity in the detection of ischemia-induced changes. The same method was also applied on leads obtained by projection of QRS loops onto their dominant directions. We show that I-US, I-DS, and I-TS present high stability in the resting state, thus providing a stable reference for ischemia characterization. Maximum relative factors of change (R-I) during PCI were found in leads derived from the QRS loop, reaching 10.5 and 13.7 times their normal variations in the control for I-US and I-DS, respectively. For standard leads, the relative factors of change were 6.01 and 9.31. The I-TS index presented a similar behavior to that of I-DS. The timing for the occurrence of significant changes in I-US and I-DS varied with lead, ranging from 30 s to 2 min after initiation of coronary occlusion. In the present ischemia model, relative I-DS changes were smaller than ST changes in most leads, however with only modest correlation between the two indices, suggesting they present different information about the ischemic process. We conclude that QRS slopes offer a robust tool for evaluating depolarization changes during myocardial ischemia

Ischemic QRS prolongation as a predictor of ventricular fibrillation in a canine model

Objectives. An acute coronary occlusion and its possible subsequent complications is one of the most common causes of death. One such complication is ventricular fibrillation (VF) due to myocardial ischemia. The severity of ischemia is related to the amount of coronary arterial collateral flow. In dog studies collateral flow has also been shown to be associated with QRS prolongation. The aim of this study was to investigate whether ischemic QRS prolongation (IQP) is associated with impending VF in an experimental acute ischemia dog model. Methods. Degree of IQP and occurrence of VF were measured in dogs (n = 21) during coronary occlusion for 15 min and also during subsequent reperfusion (experiments conducted in 1984). Results. There was a significant difference in absolute IQP between dogs which developed VF during reperfusion (47 ± 29 ms, mean ± SD) and those which did not (12 ± 10 ms; p =.001). Conclusions. IQP during acute coronary occlusion is associated with reperfusion VF in an experimental dog model and might therefore be a potential predictor of malignant arrhythmias in patients with acute coronary syndrome

The absence of high-frequency QRS changes in the presence of standard electrocardiographic QRS changes of old myocardial infarction

BACKGROUND: This study compares the high-frequency QRS components (HF-QRS) in patients with and without standard electrocardiogram (ECG) changes indicative of old myocardial infarction (MI). Previous studies have indicated that patients with an old MI differ in their HF-QRS compared with healthy subjects. The HF-QRS has been reported to be decreased during acute coronary occlusion and increased after reperfusion. However, there is controversy about the appearance of HF-QRS after the acute phase of MI. METHODS: A total of 154 patients were included, 57 with and 97 without QRS changes of old MI on the standard ECG. The patients with old MI were divided into subgroups on the basis of the MI location indicated by the standard ECG. Signal-averaged ECGs from the 12 standard leads were recorded. The root-mean-square values of the HF-QRS were determined within two frequency bands: 150 to 250 Hz and 80 to 300 Hz. RESULTS: There was a large interindividual variation in HF-QRS in patients without MI as well as in those with different MI locations. There were no significant differences between the groups in the summed HF-QRS of all 12 leads or in the pattern of lead distribution of the HF-QRS. Not even the patients with the greatest QRS changes of old MI could be differentiated from those without any changes of old MI on the standard ECG. The results were the same in both analyzed frequency bands. CONCLUSIONS: This study shows, contrary to previous studies, that analysis of HF-QRS cannot differentiate between patients with and without old MI

A 12-lead ECG-method for quantifying ischemia-induced QRS prolongation to estimate the severity of the acute myocardial event.

Studies have shown terminal QRS distortion and resultant QRS prolongation during ischemia to be a sign of low cardiac protection and thus a faster rate of myocardial cell death. A recent study introduced a single lead method to quantify the severity of ischemia by estimating QRS prolongation. This paper introduces a 12-lead method that, in contrast to the previous method, does not require access to a prior ECG