Case One
Case Two
Case One
Click on Images for Enlarged View
Findings:
Case 1: A filling defect is seen in the posterior basal segment of the LLL pulmonary artery.
Case 2: Multiple segmental and subsegmental filling defects are identified
within the upper and lower lobe pulmonary vessels.
Diagnosis: Pulmonary embolism
Discussion: With variable symptoms which are often nonspecific, pulmonary embolism has been described as the "great masquerader." It is of concern that the reported incidence of pulmonary embolism has not decreased over the last 20 to 30 years despite technological advance in diagnosis and prophylaxis. This may likely be due to technological and treatment advances in other areas of medicine prolonging the lives of patients with severe debilitating diseases. It is estimated that the total annual incidence of pulmonary embolism is 630,000. Of these, approximately 10% die within the first hour. Of those that survive 70% fail to have their P.E. detected and these people will experience a mortality rate of 30%. If the diagnosis is made promptly and therapy initiated, the mortality can be decreased to less than 10%.
Although the clinical presentation may be suggestive of pulmonary embolism, some doubt always remains. The risks of treating a patient empirically are significant, therefore an unequivocal diagnosis should always be sought. At this time it is common practice for a VQ scan to be requested as the first screening test for P.E. Unfortunately, the PIOPED investigators determined that the overwhelming majority of patients (>60%) had indeterminate or nondiagnostic studies and therefore required additional testing to establish a diagnosis. Currently, pulmonary angiography is the "gold standard" for unequivocal diagnosis of pulmonary embolism, but it is neither perfectly sensitive or specific. Because of the inherent risks and cost of the procedure, angiography is generally reserved for patients in whom more certainty about the diagnosis is absolutely required.
With the introduction of the spiral CT scanner, many of the long-standing problems of CT were overcome. A slip ring design allows for a continuous, uninterrupted rotation of the gantry, which in combination with simultaneous patient translation through the gantry, allows for a multitude of advantages such as the elimination of the need for multiple breath holds. This eliminates variations in respiration which allows better visualization of the lower lung fields (which also happens to be the most common area to find an embolus). In addition, because the data is obtained in a single breath hold, the information is volumetric and can be reformatted in any plane without respiratory artifact. Recent investigators have concluded that spiral CT scanning should be interposed between indeterminate V.P. and angiography.
References:
Blum AG, et al. Spiral-Computed Tomography Versus Pulmonary
Angiography in the Diagnosis of Acute Massive Pulmonary Embolism.
Am. J. of Cardio. 1994;74:96-98.
Matsumoto AH. Tegtmeyer CJ. Contemporary Diagnostic Approaches
to Acute Pulmonary Emboli. Radiologic Clinics of North America. 1995;33:167-182.
PIOPED Investigators. Value off the Ventilation-Perfusion Scan
in Acute Pulmonary Embolism. Chest. 1990, 263:2753-2759.
Remy-Jardin M, et al. Central Pulmonary Thromboembolism: Diagnosis
With Spiral Volumetric CT With the Single Breath Hold Technique -
Comparison With Pulmonary Angiography. Radiology. 1992;185:381-387.
Rosenow EC. Venous and Pulmonary Thromboembolism: An Algorithmic
Approach to Diagnosis and Management. Mayo Clin. Proc. 1995;70:45-49.
Remy-Jardin M, et al. Diagnosis of Pulmonary Embolism With Spiral CT:
Comparison With Pulmonary Angiography and Scintigraphy.
Radiology;200:699-706.
Submitted by: