Lung ventilation-perfusion scintigraphy in pulmonary embolism. Diagnostic specificity compared to pulmonary angiography

Pulmonary embolism--incidence and prognosis in hospitalized elderly

In a retrospective study of 210 patients with pulmonary embolism diagnosed by ventilation perfusion lung scan or at post-mortem, the incidence of pulmonary embolism was greater in patients over 50 years old (1.4%; P less than 0.05). This was largely due to an increased prevalence of serious associated disease (53%; P less than 0.05). Mortality in elderly patients (70 years and older) diagnosed by ventilation perfusion lung scan was similar to that in younger age groups (P greater than 0.05). However, the number of cases first diagnosed at post-mortem (44.50%; P less than 0.05) and total mortality (55%; P less than 0.05) were highest in this age group. Of elderly patients first diagnosed at post-mortem 14 (32%; P less than 0.05) had no other associated disease and had a recorded duration of symptoms sufficient to have allowed premortem diagnosis.

Pulmonary thromboembolism: current status report on the role of nuclear medicine

The normal perfusion study continues indisputably to rule out the presence of pulmonary embolism (PE) with reasonable certainty. However, the abnormal perfusion study requires additional specificity. Many retrospective and one prospective correlation of contrast pulmonary angiography (CPA) have largely substantiated the efficacy of ventilation imaging and increasing specificity, especially with a high-probability (HP) interpretation to approximately a 90% predictive value. In most studies, the predictive value of a low-probability (LP) interpretation also approaches 90%. Intermediate-probability (IP) ventilation-perfusion (V-P) studies are the most frequent reason for performing pulmonary angiography, although LP studies with a stated prior clinical HP should also have CPA. Ventilation imaging technique is not as uniformly established as for perfusion studies, leading to some continued variability in interpretative criteria; yet criteria proposed by Biello and his colleagues have begun to be widely adopted. Aerosol inhalation imaging is developing, but has not been widely used, while problems continue with central airways deposition. The importance of contemporary correlative chest x-rays (CXR) especially when normal, have been emphasized, as well as new findings of the import of serial post-V-P CXRs, especially in HP studies without CPA or negative CPA. CPA continues to be the most specific diagnostic test for PE when properly performed, and is complimented and enhanced by use of prior V-P findings; although it is clear that too few CPAs are being performed. Consequently, there has been too much clinical dependence on V-P imaging. The value of prospective clinical probability estimates in patient management has been better substantiated. Reemphasis on thromboembolism as a systemic disease with use of some objective evaluation of the presence of peripheral thrombosis is becoming a part of clinical rationale, with the integrated long-leg radionuclide venograms (RNV) being one of the reasonable approaches. Multicenter studies have demonstrated, contrary to prior contentions, that V-P imaging leads to a significant net reduction and use of anticoagulants, as well as having overall significant efficacy in effecting patient management in suspected PE. Some of the controversies surrounding V-P imaging are expected to be resolved with the completion of the ongoing multiinstitute Prospective Investigation of Pulmonary Embolic Diagnosis (PIOPED) study.(ABSTRACT TRUNCATED AT 400 WORDS)

Angiographic evaluation of scintigraphic abnormalities in screening for pulmonary embolism after total hip replacement

Among 240 consecutive patients subjected to total hip replacement, 206 underwent perfusion scintigraphy in screening for pulmonary embolism 10 to 14 days after surgery. All patients with perfusion abnormalities (n = 77) also underwent ventilation scintigraphy with a dry 99Tcm microaerosol. The scintigraphic abnormalities were classified according to a detailed coding system and in 50 patients pulmonary angiography was performed within 24 hours for correlation. Emboli were diagnosed in 19 patients at angiography. All patients with ventilated segmental (n = 6) or larger (n = 5) perfusion defects or multiple subsegmental defects larger than half a segment (n = 2) had emboli. Two of 8 patients with abnormally ventilated subsegmental perfusion defects larger than half a segment had emboli. Four of 21 patients with wedge-shaped subsegmental perfusion defects smaller than half a segment or defects with a rounded border towards the hilum and a peripheral extension equal to or less than that of a segment had emboli. In one of them the site of the emboli correlated to the site of the perfusion defect but occurred in normally perfused areas in the remaining 3. Ventilation scintigraphy was of no value in this group of patients. No emboli were found in patients who had areas with decreased but not totally lost perfusion (n = 8). No emboli were diagnosed in 27 lungs with a normal perfusion.

Clinical ventilation-perfusion scintigraphy

Ventilation-perfusion scintigraphy is an established procedure for the investigation of lung disease. Perfusion scans are commonly obtained with a gamma-camera following injection of 99mTc-labelled microspheres. For the assessment of regional lung ventilation, a number of techniques are now being employed, i.e. 133Xe and 127Xe single breath/washout studies, continuous inhalation of 81mKr and inhalation of radioactive aerosols. The latter two methods are now gaining consideration in clinical practice. Lung perfusion scanning is highly sensitive for detection of regional abnormalities of blood flow; the diagnosis of pulmonary embolism remains the most important clinical application of the technique. In this context, the use of a ventilation scan is required in order to increase the specificity of the procedure. In general, lung ventilation-perfusion scintigraphy is of great value for the management of patients with both primary lung disease and heart disease, by providing pathophysiological information of importance for the diagnosis, follow up and the functional evaluation of the patient.