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Background: The presence of septal perfusion defect on myocardial perfusion single-photon emission computed tomography (SPECT) in patients with known left bundle branch block (LBBB) can present a major diagnostic dilemma.
Methods: Thirty-nine patients with known LBBB underwent both SPECT and coronary computed tomography angiography (CCTA), a median of 65 days after SPECT. Patients underwent SPECT; CCTA was performed on the basis of abnormal SPECT and presence of clinical symptoms. Exclusion criteria included a history of myocardial infarction, previous coronary artery bypass surgery or percutaneous coronary intervention.
Results : Of the study population (n=39), 22 (56%) patients were female and the mean (± SD) age was 63±13 years; all patients were known to have LBBB diagnosed by electrocardiogram. SPECT results showed 24 (61%) patients had a reversible septal defect and 15 (39%) had a fixed septal defect. CCTA revealed that 27 (69%) patients had normal coronary artery or nonobstructive coronary artery disease (CAD); only 12 (31%) had abnormal coronary artery (>50% luminal stenosis). There was no relationship between patterns of SPECT perfusion abnormalities and CCTA results.
Conclusion: The presence of abnormal SPECT in patients with LBBB did not necessarily indicate the presence of CAD. Approximately 70% of patients with LBBB and abnormal SPECT had normal CCTA. The authors strongly believe CCTA must be considered the first noninvasive test in patients without history of CAD and LBBB. Normal CCTA excludes CAD, but patients with obstructive CAD >50% on CCTA will benefit from conventional coronary angiography.