It has been reported that the septal artifact associated with LBBB can be minimized by substituting pharmacological stress with dipyridamole or adenosine for exercise, since these agents have only slight chronotropic effect. It has been proposed that the decrease in septal blood flow is due to asynchronous relaxation of the septum in patients with LBBB, which is out of phase with diastolic filling of the remainder of the ventricle, during which coronary perfusion is maximal. Perfusion defects associated with LBBB frequently spares the apex in patients with normal coronary arteries. This patient is known to have LBBB, and a CT coronary angiography was performed and was normal. Selected HLA images show a reversible septal perfusion defect (arrows). Prone imaging is sometimes very helpful in selected cases (such as in this case), also attenuation correction methods can improve specificity of SPECT imaging by eliminating or minimizing soft tissue attenuation artifact. rotating display of frames in a cine loop format, regional wall motion data available on gated SPECT) often allows for differentiation between true, fixed defect, and attention artifact. In addition, intense liver, spleen, or bowel activity overlying the inferior wall of LV may mask areas of decreased perfusion or may paradoxically produce an inferior wall defect. Patients with left hemidiaphragmatic elevation may have spurious inferior wall defects due to focal attenuation. Stress prone imaging shows normal perfusion along the inferior wall (see red arrows) this finding is consistent with attention artifact by subdiaphragmatic tissue. Inferior wall attenuation artifact: selected stress SAX images show mild inferior wall perfusion defects (see white arrows) that nearly normalize on rest images.
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