[Myocardial scintigraphy with thallium 201 in assessing revascularization procedures by aortocoronary bypass or coronary dilatation]
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Thallium-201 scanning effectively assesses myocardial vascularization after coronary artery bypass surgery and catheter dilatation. It identifies residual ischemia and helps manage post-operative chest pain in patients with coronary artery disease.
Area of Science:
- Cardiology
- Nuclear Medicine
- Diagnostic Imaging
Background:
- Coronary artery disease (CAD) necessitates revascularization procedures like aortocoronary bypass surgery and catheter dilatation.
- Assessing the effectiveness of these interventions in restoring myocardial perfusion is crucial for patient outcomes.
- Exercise Thallium-201 scanning is a key diagnostic tool for evaluating myocardial viability and perfusion.
Purpose of the Study:
- To evaluate the utility of exercise Thallium-201 scanning in assessing myocardial vascularization post-revascularization.
- To correlate scanning results with angiographic findings and clinical symptoms (chest pain).
- To determine the diagnostic value of Thallium-201 in detecting residual ischemia.
Main Methods:
- Prospective study involving 40 patients undergoing aortocoronary bypass surgery and 20 patients treated with catheter dilatation for CAD.
- Preoperative and postoperative exercise Thallium-201 scans were performed.
- Results were compared with control angiography and electrocardiography (ECG) findings, alongside assessment of post-operative chest pain.
Main Results:
- Post-surgery, Thallium-201 scans normalized in 22/24 patients with improved vascularization, but remained abnormal in 2.
- Patients with no improvement or worsening vascularization showed persistent perfusion defects on scans (16/16).
- Exercise ECG remained abnormal in some patients with improved scans (6/24) and more frequently in those with unchanged/worsened vascularization (11/16); chest pain persisted in a significant proportion across both groups.
Conclusions:
- Exercise Thallium-201 scanning is a reliable method for assessing myocardial vascularization after revascularization procedures.
- It effectively identifies residual ischemia, even in patients with normal resting ECGs.
- The scan aids in differentiating causes of post-operative chest pain and guides further management.
Abstract:
40 patients underwent aortocoronary bypass surgery for coronary artery disease involving a single vessel in 2 cases, 2 vessels in 10 cases, and all 3 vessels in 28 cases. Preoperative exercise Thallium 201 scanning showed one or several zones of hypofixation (80 p. 100 of maximum myocardial fixation) which were not present at rest. After surgery, exercise scanning was normal in 22 out of 24 patients with normalised or improved vascularisation on control angiography, but remained pathological in 2 cases. However, comparable areas of hypoperfusion were observed in 16 patients with no improvement or worsening of vascularisation after operation. The exercise EG remained pathological in 6 out of 24 patients with normalised or improved vascularisation and in 11 out of 16 patients with identical or worsened vascularisation. In addition, 10 of the 24 patients with improved or normalised vascularisation, and 12 of 16 patients with identical or worsened vascularisation, continued to have chest pain after operation. A zone of hypoactivity was observed in the preoperative exercise scan in 18 out of 20 patients with isolated stenosis treated by catheter dilatation. Normalised exercise scans were recorded in all patients in the month following dilatation, but the exercise ECG remained pathological in 3 patients. In conclusion, 201 Thallium scanning gives a good assessment of myocardial vascularisation after revascularisation procedures. It helps identify patients with non-anginal post-operative chest pain, and detects residual ischaemia in patients without ischaemic signs on electrocardiography.