Subtraction electrocardiography: Detection of ischemia-induced ST displacement without the need to identify the J
C Cato Ter Haar1, Sum-Che Man1, Arie C Maan1
1Cardiology Department, Leiden University Medical Center, Leiden, the Netherlands.
Insights
A new J-point independent method accurately detects cardiac ischemia by analyzing electrocardiogram (ECG) differences. This approach simplifies ischemia detection without requiring expert J-point identification, improving diagnostic efficiency.
Area of Science:
- Cardiology
- Medical Imaging
Background:
- Electrocardiograms (ECGs) are crucial for diagnosing acute chest pain and myocardial ischemia.
- Current guidelines recommend comparing acute ECGs with prior ones, but lack specific methods for J-point identification challenges.
- A novel J-point independent method is proposed for improved ECG comparison in ischemia detection.
Purpose of the Study:
- To develop and validate a J-point independent method for comparing acute and baseline ECGs to detect cardiac ischemia.
- To assess the correlation between J-point synchronized and QRS onset synchronized ECG difference signals.
- To determine the sensitivity and specificity of the novel method in identifying ischemia.
Main Methods:
- Vectorcardiograms were derived from ECGs of 81 patients undergoing PCI.
- Baseline and ischemic vectorcardiograms were compared using J-point or QRS onset synchronization.
- Vector magnitude difference signals (ΔH) were calculated and analyzed using linear regression.
Main Results:
- A high correlation (0.93) was observed between ΔH 40ms post-J point and ΔH 160ms post-QRS onset.
- The method achieved high sensitivity (81-84%) in detecting ischemia based on a 0.05mV ΔH threshold.
- 66/81 and 68/81 patients were correctly identified as having ischemia using J-point and QRS onset synchronization, respectively.
Conclusions:
- A J-point independent method for cardiac ischemia detection has been successfully developed.
- This approach eliminates the need for manual J-point identification, simplifying the diagnostic process.
- The method offers a promising alternative for objective and efficient detection of myocardial ischemia using ECG data.
Background:
When triaging a patient with acute chest pain at first medical contact, an electrocardiogram (ECG) is routinely made and inspected for signs of myocardial ischemia. The guidelines recommend comparison of the acute and an earlier-made ECG, when available. No concrete recommendations for this comparison exist, neither is known how to handle J-point identification difficulties. Here we present a J-point independent method for such a comparison.
Methods:
After conversion to vectorcardiograms, baseline and acute ischemic ECGs after 3minutes of balloon occlusion during elective PCI were compared in 81 patients of the STAFF III ECG database. Baseline vectorcardiograms were subtracted from ischemic vectorcardiograms using either the QRS onsets or the J points as synchronization instants, yielding vector magnitude difference signals, ΔH. Output variables for the J-point synchronized differences were ΔH at the actual J point and at 20, 40, 60 and 80ms thereafter. Output variables for the onset-QRS synchronized differences were the ΔH at 80, 100, 120, 140 and 160ms after onset QRS. Finally, linear regressions of all combinations of ΔHJ+… versus ΔHQRS+… were made, and the best combination was identified.
Results:
The highest correlation, 0.93 (p<0.01), was found between ΔH 40ms after the J point and 160ms after the onset of the QRS complex. With a ΔH ischemia threshold of 0.05mV, 66/81 (J-point synchronized differences) and 68/81 (onset-QRS synchronized differences) subjects were above the ischemia threshold, corresponding to sensitivities of 81% and 84%, respectively.
Conclusion:
Our current study opens an alternative way to detect cardiac ischemia without the need for human expertise for determination of the J point by measuring the difference vector magnitude at 160ms after the onset of the QRS complex.
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