Case 18-2 cont'd
Conclusion:
No evidence of wedge-shaped segmental/subsegmental mismatch perfusion defect to suggest pulmonary embolism.
Impression:
PE Absent (According to Modified PIOPED II criteria).
NUCLEAR MEDICINE AND MOLECULAR IMAGING: THE REQUISITES, 5th EDITION
ISBN: 978-0-323-530378
DISCUSSION:
One major sign of severe left HF is pulmonary congestion. Pulmonary congestion is recognized as a challenge to diagnose and grade objectively. Available guidelines recommend the use of chest X‐ray (CXR) or the presence of rales on physical examination, although the sensitivity and specificity of these examinations for the diagnosis of pulmonary congestion are low. Even among HF patients with known pulmonary congestion, studies show that CXR can be normal in 50–60% of cases.
According to several studies Ventilation/perfusion single‐photon emission computed tomography can be used as a non‐invasive method to diagnose and quantify pulmonary congestion in patients with HF and is more accurate than CXR in diagnosing pulmonary congestion in the clinical setting.
In healthy individuals, because of gravity, pulmonary perfusion is predominantly distributed to dependent parts of the lungs, that is, to posterior parts of the lungs in the supine position. In patients with pulmonary congestion, however, the elevated pressure and surrounding interstitial edema cause narrowing and an increased resistance to flow in vessels in the lower parts of the lungs. Hence, pulmonary perfusion is redistributed from the posterior to anterior parts of the lungs in the supine position, and this can be shown and quantified with technetium‐99m‐labelled macroaggregated albumin. Ventilation is usually not affected to the same degree. The perfusion defects that occur in the posterior parts of the lungs are not of segmental character as seen in pulmonary embolism.
Reference:
-
Nuclear Medicine Department of The Ottawa Hospital
-
NUCLEAR MEDICINE AND MOLECULAR IMAGING: THE REQUISITES, 5th EDITION ISBN: 978-0-323-530378
-
Jögi J, Al-Mashat M, Rådegran G, Bajc M, Arheden H. Diagnosing and grading heart failure with tomographic perfusion lung scintigraphy: validation with right heart catheterization. ESC Heart Fail. 2018 Oct;5(5):902-910. doi: 10.1002/ehf2.12317. Epub 2018 Jul 17. PMID: 30015395; PMCID: PMC6165926.