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Correlation of adenosine thallium 201 perfusion patterns with markers for inducible ischemia
M S Fenster1, M D Feldman, G Camarano
1Department of Internal Medicine, University of Virginia Health Sciences Center, Charlottesville 22908, USA.
Insights
Intravenous adenosine infusion for cardiac stress testing revealed few cases of true myocardial ischemia in patients with coronary artery disease. Most perfusion defects detected by thallium-201 imaging during adenosine stress are due to flow reserve heterogeneity, not ischemia.
Area of Science:
- Cardiology
- Nuclear Cardiology
- Pharmacology
Background:
- Coronary artery disease (CAD) diagnosis often relies on stress imaging.
- Adenosine is a pharmacologic agent used for myocardial stress testing.
- Distinguishing true ischemia from other perfusion defects is crucial.
Purpose of the Study:
- To assess the incidence of true myocardial ischemia during intravenous adenosine infusion in CAD patients.
- To investigate the causes of perfusion defects observed with adenosine stress testing.
Main Methods:
- 13 patients (11 with CAD) underwent intravenous adenosine infusion and thallium-201 (201Tl) SPECT during cardiac catheterization.
- Coronary artery stenoses, wall motion abnormalities (echocardiography), and hemodynamic parameters were assessed.
- Myocardial oxygen extraction and lactate production were evaluated.
Main Results:
- All 11 CAD patients had significant coronary stenoses (>=70%).
- Only 18% of patients showed new wall motion abnormalities.
- Pulmonary capillary wedge pressure did not significantly increase; coronary sinus oxygen saturation rose, indicating reduced myocardial oxygen extraction.
Conclusions:
- True myocardial ischemia is infrequent during intravenous adenosine stress testing in CAD patients.
- Perfusion defects seen with vasodilator stress are primarily attributed to heterogeneous coronary flow reserve, not true ischemia.
- Adenosine stress imaging with 201Tl may overestimate ischemia in some CAD patients.
Abstract:
To determine the frequency of true myocardial ischemia caused by hemodynamic, metabolic, and regional functional abnormalities after intravenous adenosine infusion in patients with coronary artery disease, 13 patients--11 with coronary artery disease--received intravenous adenosine and thallium 201 during cardiac catheterization. Intracoronary adenosine levels increased by an average of 9.4-fold over baseline. Of the 11 patients, all had > or = 70% stenoses with a mean number of redistribution defects per patient of 3.3 +/- 0.7. Only two (18%) patients had new wall motion abnormalities detected by echocardiography during adenosine infusion. Pulmonary capillary wedge pressure did not significantly rise (13 +/- 7 to 17 +/- 8 mm Hg, p= NS). Lactate production occurred in two patients. Coronary sinus oxygen saturation levels rose from 29% +/- 6% to 68% +/- 8%, consistent with less myocardial oxygen extraction. Thus, despite a high prevalence of defects detected by 201Tl, the prevalence of true myocardial ischemia in patients with coronary artery disease undergoing pharmacologic stress imaging with intravenous adenosine is low. Perfusion defects induced by vasodilator stress are predominantly caused by heterogeneity of flow reserve rather than true ischemia.