Myocardial perfusion defects in left bundle branch block: True or false? Fact or artifact?
✍ Scribed by Frans J.Th. Wackers
- Publisher
- Springer
- Year
- 1997
- Tongue
- English
- Weight
- 455 KB
- Volume
- 4
- Category
- Article
- ISSN
- 1071-3581
No coin nor oath required. For personal study only.
✦ Synopsis
Despite tomographic image acquisition, computer processing, and quantification, interpretation of myocardial perfusion images remains an art. The interpreter has to navigate judiciously between the Scylla and Charybdis of normal variants and artifacts to arrive at an accurate and clinically meaningful image interpretation. The various artifacts that cause these problems are well known: breast attenuation, diaphragmatic attenuation, and apparently false defects in patients with left bundle branch block (LBBB). 1
Experienced interpreters generally manage to deal with artifacts caused by tissue attenuation such as by breast and diaphragm. They are able to recognize the artifactual nature of such defects with reasonable certainty by careful inspection of raw and reconstructed images, electrocardiography-gated images, or images acquired with the patient in different positions. 2,3 Patients with recognized artifacts on perfusion images are rarely inappropriately referred for cardiac catheterization, and patients with images interpreted as normal, despite the presence of artifacts have the same favorable outcome as patients with unequivocally normal images without artifacts. 4 The future development and clinical implementation of attenuation correction of single photon emission computed tomography (SPECT) images may eliminate this problem altogether or, it is hoped, make it simpler to deal with attenuation artifacts.
The issue of myocardial perfusion artifacts in patients with LBBB is more complex. The underlying cause for these abnormal images is different than that for breast or diaphragmatic attenuation and is not caused by inhomogeneous photon absorption. In many patients with LBBB without previous myocardial infarction, resting myocardial perfusion images are normal. In fact, one of the first clinical applications of resting thallium-201 myocardial perfusion imaging was to critically evaluate the usefulness of electrocardiographic criteria