Longterm Follow-Up of Patients with Suspected Pulmonary Embolism and a Normal Lung Scan: Perfusion Scans in Embolic Suspects

doi:10.1378/chest.82.4.411

Chest

Volume 82, Issue 4, October 1982, Pages 411-415

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There is widespread acceptance of the thesis that in a patient with suspected embolism, a normal perfusion lung scan excludes the diagnosis of acute pulmonary embolism. However, limited published data exist which validate this thesis. We have explored this question by longitudinal follow-up of 68 patients who were referred for lung scanning to rule out embolism and proved to have normal perfusion lung scans. Risk factors for venous thromboembolism among these patients were similar to those reported in prior series of patients with pulmonary embolism. Our data support the widely-held views that: 1) a normal perfusion lung scan excludes the diagnosis of clinically significant pulmonary emboli; 2) the diagnostic work-up for suspected pulmonary embolism need not extend beyond a normal perfusion scan; 3) anticoagulant therapy can be discontinued after a normal perfusion scan, except in the presence of documented venous thrombosis; and 4) a normal lung scan has the same value in ruling out embolism in man as does a normal pulmonary angiogram.

Section snippets

MATERIALS AND METHODS

The data of all patients who had had an imaging procedure at the San Diego Veterans Hospital between 1976 and 1980 were reviewed. If the data noted a perfusion lung scan, the requisition and scan report were examined to determine whether two criteria were met: (1) the patient had been referred for the scan to rule out clinically-suspected pulmonary embolism; (2) findings on the perfusion scan were reported as normal. The scans were then reviewed independently by two of us (MSK and KEK). Each

RESULTS

Of the 68 patients, 63 (93 percent) were men. They ranged in age from 22 to 80 years (average 51.0 years). Thirty-three (49 percent) had documented heart disease; 12 (18 percent) had a history of surgery and/or immobilization less than one month prior to the time of the reference perfusion scan; and more than half (38) were smokers. Other documented risk factors included a previous history of lower extremity thrombophlebitis in six and a current malignancy in three (Table 1).

Chest pain, usually

CASE 1

This 74-year-old man had been treated for congestive heart failure of unknown cause during his initial admission. A normal perfusion lung scan was obtained during this admission. Despite intensive therapy, severe, unrelenting dyspnea led to readmission six months later. Chest roentgenogram on admission disclosed cardiomegaly, pulmonary congestion and bilateral pleural effusions. A perfusion lung scan now disclosed bilateral basilar defects. He failed to respond to treatment Postmortem

DISCUSSION

The accurate and prompt diagnosis of pulmonary embolism remains a challenge to the clinician, radiologist, and specialist in nuclear medicine. Two major questions are faced in defining the most appropriate diagnostic sequence in patients with suspected embolism: (1) how can the diagnosis be excluded? and (2) if it cannot be excluded, how can the diagnosis be established? In this study, we focused on the first question. Our data indicate that, based upon patient outcome, a normal perfusion scan

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Citation Excerpt :
An effective way to decrease cost and radiation exposure is to perform a perfusion scan without ventilation. Perfusion scintigraphy combined with chest radiography has been shown to have the same diagnostic accuracy as MDCTPA and V/Q scintigraphy,70 and a normal perfusion scan excludes PE with an NPV close to 100%.71-73 Thus, the ventilation portion of the examination can be eliminated without decreasing diagnostic accuracy.69-72,74,75
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In the beginning, there was the Q scan.1-3 A normal Q scan has long been accepted to exclude pulmonary embolism (PE) for practical purposes (the morbidity and mortality of missed PE has been thought to be far less than that from continuing the diagnostic evaluation or with preemptive therapy).4,5 It is the Q scan that is pivotal in excluding PE; as long as Q is normal, the V scan or chest radiograph (CXR) can be abnormal and the examination is still read as negative for PE.
In this article, we review the evolution of scintigraphy for the diagnosis of acute pulmonary embolism (PE). We begin with perfusion (Q) scintigraphy, review the development of diagnostic systems that combine ventilation (V) scintigraphy and chest radiography with the Q scan, and describe in detail the Prospective Investigative Study of Acute Pulmonary Embolism Diagnosis (PISAPED) criteria for diagnostic categorization of the Q scan read in conjunction with the chest radiograph. Finally, we review the results obtained with the PISAPED criteria in clinical research studies. The PISAPED method for lung scan interpretation provides sensitivity and specificity for diagnosing acute PE that is comparable to V/Q scanning and to computed tomography angiography (CTA), with fewer nondiagnostic results than either V/Q or CTA. The criteria can be used effectively in a diagnostic management approach that incorporates the use of a clinical prediction rule. Clinical outcomes in patients in whom PE is excluded in this way are comparable to outcomes for patients in whom the diagnosis is excluded by CTA or conventional angiography.
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Citation Excerpt :
A normal perfusion scan excludes pulmonary embolism with a negative predictive value close to 100%.30,72,73 The ventilation scan can be eliminated in most patients without reducing diagnostic accuracy.31,72-74 If outcome studies confirm its efficacy, perfusion scintigraphy could be beneficial in young women and in other patients in whom reduced radiation exposure is preferred.
The state of the art of diagnostic evaluation of hemodynamically stable patients with suspected acute pulmonary embolism was reviewed. Diagnostic evaluation should begin with clinical assessment using a validated prediction rule in combination with measurement of D-dimer when appropriate. Imaging should follow only when necessary. Although with 4-slice computed tomography (CT) and 16-slice CT, the sensitivity for detection of pulmonary embolism was increased by combining CT angiography with CT venography, it is not known whether CT venography increases the sensitivity of 64-slice CT angiography. Methods to reduce the radiation exposure of CT venography include imaging only the proximal leg veins (excluding the pelvis) and obtaining discontinuous images. Compression ultrasound can be used instead. In young women, radiation of the breasts produces the greatest risk of radiation-induced cancer. It may be that scintigraphy is the imaging test of choice in such patients, but this pathway should be tested prospectively. A patient-specific approach to the diagnosis of pulmonary embolism can be taken safely in hemodynamically stable patients to increase efficiency and decrease cost and exposure to radiation.

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: Manuscript received January 11; revision accepted April 21.

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Chest

Clinical InvestigationsLongterm Follow-Up of Patients with Suspected Pulmonary Embolism and a Normal Lung Scan: Perfusion Scans in Embolic Suspects

Section snippets

MATERIALS AND METHODS

RESULTS

CASE 1

DISCUSSION

Lancet

Prog Cardiovasc Res

Prog Cardiovasc Dis

Prog Cardiovas Dis

Am Heart J

The diagnosis and treatment of pulmonary embolism

Med Clin N Am

Assessment of anticoagulant treatment of venous thromboembolism

Ann Surg

Lethal pulmonary in embolism

Urokinase pulmonary embolism trial, Phase 1 results

JAMA

Urokinase—Streptokinse pulmonary embolism trial, Phase 2 results: A cooperative study

JAMA

A prospective study of the value of monitoring heparin treatment with the activated partial thromboplastin time

N Engl J Med

Management of heparin therapy

N Engl J Med

Drug-related deaths among medical inpatients

JAMA

Does a normal isotope perfusion scan exclude pulmonary embolism?

Investigative Rad

The value of the lung scan in the evaluation of young patients with pleuritic chest pain

J Nucl Med

A diagnostic strategy using ventilation-perfusion studies in patients suspect for pulmonary embolism

J Nucl Med

Overdiagnosis and overtreatment of pulmonary thromboembolism: The emperor may have no clothes

Ann Intern Med

Assessment of pulmonary photoscanning and angiography in experimental pulmonary embolism

Circulation

Clinical Investigations
Longterm Follow-Up of Patients with Suspected Pulmonary Embolism and a Normal Lung Scan: Perfusion Scans in Embolic Suspects