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Detection of pacing-induced myocardial ischemia by endocardial electrograms recorded during cardiac catheterization
E G Nabel1, T L Shook, M Meyerovitz
1Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts 02115.
Insights
Rapid atrial pacing can detect myocardial ischemia in coronary artery disease patients. Endocardial electrograms reveal ST elevation, a sensitive marker of ischemia, even before symptoms appear.
Area of Science:
- Cardiology
- Electrophysiology
- Diagnostic Imaging
Background:
- Coronary artery disease (CAD) diagnosis can be challenging.
- Surface electrocardiogram (ECG) may not detect subendocardial ischemia during rapid atrial pacing.
- Angina and increased left ventricular end-diastolic pressure are common indicators but may not always be apparent.
Purpose of the Study:
- To evaluate the utility of endocardial electrograms for detecting myocardial ischemia during rapid atrial pacing.
- To assess the sensitivity of endocardial ST elevation as a marker for pacing-induced ischemia.
- To compare endocardial electrogram findings with surface ECG and clinical symptoms.
Main Methods:
- Recorded unipolar endocardial electrograms from a guidewire tip placed on the endocardial surface.
- Performed rapid atrial pacing in 21 patients with known CAD.
- Monitored endocardial electrograms, surface ECG leads, and left ventricular end-diastolic pressure.
- Assessed the effect of nitroglycerin and percutaneous transluminal coronary angioplasty (PTCA) on endocardial ST elevation.
Main Results:
- No ST elevation was observed in baseline endocardial electrograms.
- Marked ST elevation in endocardial electrograms occurred in 17 out of 21 patients post-pacing.
- Endocardial ST elevation was abolished by nitroglycerin and, in some cases, by successful PTCA.
- Endocardial ST elevation appeared earlier than angina or changes in left ventricular end-diastolic pressure.
Conclusions:
- ST elevation in endocardial electrograms during rapid atrial pacing is a sensitive indicator of myocardial ischemia.
- This method may detect pacing-induced ischemia earlier than traditional surface ECG changes or clinical symptoms.
- Endocardial electrography offers a valuable tool for diagnosing ischemia in patients with CAD.
Abstract:
Rapid atrial pacing confirms myocardial ischemia in patients with coronary artery disease when angina is provoked, and is accompanied by an increase in left ventricular end-diastolic pressure. In such cases, abnormalities in the surface electrocardiogram (ECG) are often not apparent. To enhance detection of subendocardial ischemia during rapid atrial pacing, local unipolar electrograms were recorded from the tip of a 0.025 in. (0.064 cm) diameter guidewire positioned against the endocardial surface of potentially ischemic regions. Endocardial electrograms, left ventricular end-diastolic pressure and multiple surface ECG leads were recorded during rapid atrial pacing in 21 patients with coronary artery disease. Before pacing, endocardial electrograms in all 21 patients were free of ST elevation. Marked ST elevation was apparent in 17 of the 21 patients after rapid atrial pacing and could be abolished by nitroglycerin. Moreover, in several patients, endocardial ST elevation after rapid atrial pacing was abolished after successful percutaneous transluminal coronary angioplasty of the critically stenosed artery supplying the ischemic region of myocardium. It is concluded that ST elevation in the endocardial electrogram after rapid atrial pacing is a reflection of myocardial ischemia and may be a sensitive marker of pacing-induced ischemia appearing earlier than angina, postpacing increase in left ventricular end-diastolic pressure or ST depression in the surface ECG.