Usefulness of dynamic perfusion SPECT with quantitative assessment of myocardial perfusion reserve for the detection of myocardial ischaemia in patients with presumed new left bundle branch block.

Aims: The aim of this retrospective study was to evaluate the ability of dynamic SPECT with quantitative analysis of myocardial blood flow (MBF) and myocardial flow reserve (MFR) for the detection of coronary artery disease (CAD) in patients with presumed new left bundle branch block (LBBB).

Methods And Results: We evaluated the dynamic SPECT results from 174 consecutive patients with LBBB without a history of CAD from a single center. MBF was assessed at rest and during regadenoson (400 μg). Normal MFR was defined as ≥ 2.1. Left ventricular function and segmental perfusion were assessed from conventional gated SPECT. SPECT abnormalities were found in 17/174 (10%) patients including a reversible SPECT defect in 4 patients (2.3%), a fixed defect in 12 patients (7%), and both in 1 patient. Global left ventricular function was normal despite a significant impairment of septal wall motion. Stress and rest MBF was decreased in the septum and the inferior wall compared with other walls ( < 0.0001), resulting in similar MFR. A reduced MFR was associated with a fixed defect ( = 0.04). Only 18 patients (10%) presented with a decreased MFR. They were more often referred to subsequent coronary angiography (8/18, 44%) compared with patients with a normal MFR (9/156, 6%, χ = 27.382, < 0.0001). However, significant coronary lesions were finally found in only 4/174 patients (2%).

Conclusion: Although a decreased MFR was associated with a fixed defect on conventional perfusion imaging, the low rate of CAD finally demonstrated in this study questions the relevance of routine screening for CAD in patients with presumed new LBBB.