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False-positive reversible perfusion defect during dobutamine-thallium imaging in left bundle branch block
D A Tighe1, H G Hutchinson, C H Park
1Division of Cardiology, Jefferson Medical College, Thomas Jefferson University, Philadelphia.
Insights
Dobutamine stress thallium imaging can cause false-positive septal and periapical perfusion defects in patients with left bundle branch block (LBBB). These abnormalities, seen in coronary artery disease diagnosis, require cautious interpretation due to potential inaccuracies.
Area of Science:
- Cardiology
- Nuclear Cardiology
- Diagnostic Imaging
Background:
- Left bundle branch block (LBBB) complicates exercise stress thallium scans, often causing false-positive septal and apical perfusion abnormalities.
- Pharmacologic agents like dipyridamole and adenosine have shown reduced false-positive rates in LBBB patients compared to exercise stress.
- Dobutamine, a synthetic catecholamine, is increasingly used for myocardial perfusion imaging in patients unable to exercise, mimicking physiological stress.
Observation:
- A patient with pre-existing LBBB underwent dobutamine thallium imaging.
- The imaging revealed septal and periapical perfusion defects.
- Subsequent coronary angiography confirmed these defects to be false-positives.
Findings:
- Dobutamine thallium imaging may produce false-positive septal and periapical perfusion defects in patients with LBBB.
- The positive inotropic and chronotropic effects of dobutamine can simulate exercise-induced changes, leading to misinterpretation.
Implications:
- Results suggest that septal and periapical perfusion abnormalities observed during dobutamine thallium imaging in LBBB patients should be interpreted with caution.
- This highlights the need for careful consideration of underlying conditions when interpreting myocardial perfusion imaging results.
- Further research may be warranted to refine imaging protocols or diagnostic criteria for LBBB patients undergoing pharmacologic stress testing.
Abstract:
In the presence of pre-existing left bundle branch block (LBBB) exercise stress thallium scans have been associated with false-positive septal and apical perfusion abnormalities. Recent reports have documented a lower incidence of false-positive septal perfusion defects when pharmacologic agents such as dipyridamole or adenosine are utilized in patients with LBBB. Dobutamine, a synthetic catecholamine, is being used with increasing frequency in combination with perfusion agents for the diagnosis of coronary artery disease in patients unable to achieve an adequate exercise workload. Because the positive inotropic and chronotropic actions of doubtamine are similar to the physiologic effects of treadmill exercise, it is conceivable that false-positive perfusion abnormalities will be observed in patients with pre-existing LBBB undergoing dobutamine perfusion imaging. We describe a patient with underlying LBBB who underwent dobutamine thallium imaging which revealed septal and periapical defects. Subsequent coronary angiography showed these abnormalities to be false-positive. It is concluded that septal and periapical perfusion abnormalities during dobutamine thallium imaging may be false-positive and should be interpreted cautiously.