Depolarization changes during acute myocardial ischemia by evaluation of QRS slopes: standard lead and vectorial
Daniel Romero1, Michael Ringborn, Pablo Laguna
1Communications Technology Group, Aragón Institute for Engineering Research, and CIBER de Bioingeniería, Biomateriales y Nanomedicina, University of Zaragoza, 50018 Zaragoza, Spain. daromero@unizar.es
Insights
Analyzing QRS complex slopes, specifically upward (ℑ(US)) and downward (ℑ(DS)) R-wave slopes and the terminal S-wave upward slope (ℑ(TS)), offers a robust method for detecting myocardial ischemia during acute coronary syndromes.
Area of Science:
- Cardiology
- Biomedical Engineering
- Electrocardiography
Background:
- Acute coronary syndromes (ACS) diagnosis and risk stratification rely on ST-T segment changes.
- The QRS complex's depolarization phase offers additional, underutilized information for ischemia detection.
Purpose of the Study:
- To evaluate ischemia-induced changes in specific QRS complex slopes (ℑ(US), ℑ(DS), ℑ(TS)) as a robust measure of pathological depolarization changes.
- To develop and apply a dynamic ECG normalization method for enhanced sensitivity in detecting these QRS changes during ischemia.
Main Methods:
- Quantification of ℑ(US), ℑ(DS), and ℑ(TS) using dynamic ECG normalization on resting and percutaneous coronary intervention (PCI)-induced ischemia recordings.
- Application of the method to standard ECG leads and leads derived from QRS loop projections.
- Analysis of slope stability in resting state and relative change factors (ℜ(ℑ)) during PCI.
Main Results:
- QRS slopes (ℑ(US), ℑ(DS), ℑ(TS)) demonstrated high stability during resting state, serving as reliable references.
- Significant changes in ℑ(US) and ℑ(DS) occurred within 30 seconds to 2 minutes of ischemia onset.
- QRS loop-derived leads showed greater relative changes (up to 13.7x) compared to standard leads (up to 9.31x).
- Relative ℑ(DS) changes were smaller than ST changes but showed modest correlation, indicating complementary information.
Conclusions:
- QRS complex slopes provide a stable and sensitive measure for characterizing myocardial ischemia during the depolarization phase.
- The developed quantification method enhances the detection of ischemia-induced depolarization abnormalities.
- QRS slope analysis offers a valuable, complementary tool to conventional ST-T segment analysis for ACS patient management.
Abstract:
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.
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