[Exercise 201-thallium myocardial scintigraphy in left bundle branch block]

Area of Science:

• Cardiology
• Nuclear Medicine
• Diagnostic Imaging

Background:

• Left bundle branch block (LBBB) can cause reduced septal uptake of 201-Thallium, leading to false positives in diagnosing left anterior descending coronary artery disease.
• The prevalence and diagnostic value of septal defects in LBBB patients undergoing Thallium-scintigraphy require further assessment.

Purpose of the Study:

• To determine the prevalence of septal perfusion defects in patients with left bundle branch block (LBBB).
• To evaluate the diagnostic sensitivity and specificity of 201-Thallium scintigraphy for detecting coronary artery disease in LBBB patients.

Main Methods:

• Exercise 201-Thallium myocardial scintigraphy was performed on 54 stable LBBB patients.
• Patients with other cardiomyopathies or prior myocardial infarction were excluded.
• Coronary angiography was used to evaluate coronary stenosis in a subset of patients.

Main Results:

• Septal defects were observed in 67% of patients.
• Diagnostic sensitivity for left anterior descending coronary artery disease was 67% (100% with semi-quantitative analysis), with low specificity (52% and 19% respectively).
• High sensitivity (80%) and specificity (100%) were found for right coronary artery disease detection.

Conclusions:

• A high prevalence of septal defects exists in LBBB patients, indicating high sensitivity but low specificity for left anterior descending coronary artery disease diagnosis.
• Semi-quantitative analysis improves sensitivity but decreases specificity.
• 201-Thallium scintigraphy is accurate for right coronary artery disease but less so for circumflex artery disease.