Is Pulmonary Angiography Essential for the Diagnosis of Acute Pulmonary Embolism? James 0. Menzoian, MD, Boston, Massachusetts Lester F. Willlams, MD, Boston, Massachusetts

We believe that pulmonary angiography is essential for the diagnosis of acute pulmonary embolism and that the potential hazards of heparin therapy, especially in the early postoperative period, make accurate diagnosis of pulmonary embolism essential. At our institution, some workers believe strongly that with a good clinical picture and corroborating arterial blood gas measurements, acute pulmonary embolism can be diagnosed with relative certainty. Others believe that lung scanning technics are equally effective. In several published reviews, the authors attempted to support the methods used in their institutions in diagnosing acute pulmonary embolism. These methods include clinical assessment, arterial blood gas determinations, serum enzyme determinations, lung perfusion scanning, ventilation-perfusion lung scanning, chest X-ray evaluation, and pulmonary angiography [l-3]. Surgeons are often required to treat patients in the early postoperative period for presumed acute pulmonary embolism. Because the use of heparin in these patients is potentially hazardous and its complications often require vena cava interruption, acute pulmonary embolism should be diagnosed with the most reliable methods available. We are also concerned about the implications of long-term oral anticoagulant therapy. Considerable evidence now exists that heparin is a leading cause of adverse drug reactions in hospitalized patients and that it is responsible for the majority of drug-related deaths in otherwise reasonably normal patients [4,5]. Evidence also exists that oral anticoagulant drugs are often responsible for hospital admissions [6]. Patients with a diagnosis of pulmonary embolism and their phyFrom The Division of Surgery. Boston University Medical Center, Boston, Massachusetts. Reprint requests shoukl be addressed to James 0. Menzoian, MD. 75 East Newton Street, University Hospital. Boston. Massachusetts 02118. Presented at the Fifty-N&h Annual Meeting of the New England Surgical Society, September 29-October 1. 1978.

Vduma 137, Aprtl1979

sicians fear that even the slightest chest discomfort indicates recurrent pulmonary embolism. We reviewed the experience at our institution in diagnosing acute pulmonary embolism to determine the accuracy of the various methods available. Material and Methods The most recent consecutive 158 pulmonary angiograms performed at Boston University Medical Center, University Hospital, served as the basis for this study. We used only pulmonary angiograms performed for the presumed diagnosis of acute puhnonary embolism. The records of the 158 patients were reviewed by one of the authors (J.O.M.). Clinical Impressions. An attempt was made to obtain from the record the degree of certainty with which acute pulmonary embolism was diagnosed by the clinicians caring for the patient at the time. The initial history and physical examination, the attending physician’s notes and various consultant evaluations were reviewed, and a score was given by the chart reviewer indicating whether the clinicians believed that the probability of acute pulmonary embolism was high or low. Arterial Blood Gas Determinations. The initial blood gas determinations performed when acute pulmonary embolism was diagnosed were reviewed. Complete blood gas evaluationsi all performed with the patient breathing room air, were available in 120 patients. Perfusion Lung Scans. These were performed in 124 of the 158 patients, using microaggregated albumin (99 TcMAA). Routine views were recorded with a scintillation camera in the right and left anterior, right and left posterior, and right and left lateral positions. When necessary, right and left posterior oblique views were performed. The reports routinely describe the perfusion deficits, if present, and report a high, moderate, or low probability of acute pulmonary embolism or a normal scan. Ventilation-Perfusion Lung Scans. This technic was performed in only 20 of the 158 patients studied. The technic for performing these scans at University Hospital includes the use of xenon-133 gas. The perfusion scan was

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Figure 1. The resuits of pulmonary angiography in patients con&Wed to have a high and low probability of pulmonary embofism based on the clinical impression. The black areas indicate a positive angiogram.

performed first in these patients to help determine whether the ventilation scan should be performed and to help select the views for ventilation scanning. Pulmonary Angiography. Pulmonary angiography was performed in 158 patients with the presumed diagnosis of pulmonary embolism as soon after the acute event as possible. The Seldinger Technique was used, usually performed through the femoral vein approach. Selective left and right pulmonary arterial contrast injections were administered with sequential filming of each lung in at least two views. If no emboli were seen on the initial films, superselective arteriograms with magnification filming were obtained in the areas considered suspicious on the perfusion lung scan. A soft Cook french pigtail catheter was routinely used. The transfemoral approach was performed in approximately 99 per cent of the cases. The usual method was injection of 40 cc of dye per injection (20 cc per second for 2 seconds). The usual contraindication to pulmonary angiography was a pulmonary arterial pressure greater than 60 cm of water, although studies were performed in three such patients without complication. Results

The records of 158 patients who had undergone pulmonary angiography at University Hospital were reviewed. The reviewer attempted to assess the probability of acute pulmonary embolism based on the clinical impression, arterial blood gases on room air, perfusion lung scan results, ventilation-perfusion lung scan results, and pulmonary angiography. The results of the pulmonary angiogram were the basis for documentation of pulmonary embolism. Although some authors believe that pulmonary angiography is not completely accurate, we believe it is the most reliable technic available to the clinician. There were few deaths in the patients studied, and thus the results of postmortem evaluation are not helpful. Clinical Impression. Of the 158 patients in this study, 111 patients were considered to have a high probability of acute pulmonary embolism and 47 a low probability based on the clinical impression. Sixty of the 111 patients (54 per cent) in the high

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Figure 2. 77~ resuits of puimonary angiograpfty in patients considered to have a high, moderate, and low probabiiity of pulmonary embolism on the basis of perfusion kmg scans and in five patients with a normal lung scan. The black areas indicate a positive anglogram.

probability group and 10 of the 47 patients (21 per cent) in the low probability group had a positive pulmonary angiogram. (Figure 1.) Thus the clinical impression accurately diagnosed acute pulmonary embolism in approximately 50 per cent of the patients. Perfusion Lung Scans. These were performed in 124 patients. Forty-eight of seventy-three patients (66 per cent) with a high probability perfusion lung scan, four of seven patients (67 per cent) with a moderate probability lung scan, and six of thirty-nine patients (15 per cent) with a low probability lung scan had a positive pulmonary angiogram. Of the five patients with a normal lung scan in whom pulmonary angiography was performed, none had a positive pulmonary angiogram. (Figure 2.) The perfusion lung scan alone correctly indicated a positive diagnosis in 66 per cent of the patients, resulting in a false positive rate rate of 33 per cent. Ventilation-Perfusion Lung Scans. The results of these scans are reported although they were performed in only a small number of our patients. Eleven of twelve patients (92 per cent) with a high probability ventilation-perfusion scan and two of eight patients (25 per cent) with a low probability scan had a positive angiogram. Using these results alone, one of our patients would have been needlessly heparinized and two would not have been treated for angiographically documented pulmonary embolism. Arterial Blood Gases. These determinations were performed with the patient breathing room air as soon after the presumed acute pulmonary embolism as possible. Complete blood gas determinations were available in 120 patients. The mean partial pressure of oxygen (POs) in the patients with a positive pulmonary angiogram was 64 mm Hg and the mean partial pressure of carbon dioxide (PCOs) was 30 mm Hg. In the patients with a negative pulmonary an-

The American Journal of Surgery

Diagnosing Acute Pulmonary Embolism

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giogram the mean PO2 was 63 mm Hg and the mean PC02 34 mm Hg. (Figures 3 and 4.) The distribution of arterial blood POs values in patients with a positive angiogram show that some patients with POs values as high as 100 mm Hg had a positive angiogram, but most of the patients with a positive angiogram had PO2 values of 50 to 80 mm Hg. It has been suggested that the normal value for PO2 in the average hospital patient with a mean age of 45 years is greater than 80 mm Hg [I]. These authors believe that a PO:! of less than 80 mm Hg is abnormal and in the appropriate clinical setting indicates acute pulmonary embolism. We analyzed the data using a cut-off point of 80 mm Hg. Of the 101 patients with a PO2 of less than 80 mm Hg, 45 (45 per cent) had a positive pulmonary angiogram. Of the nineteen patients with an arterial PO2 greater than 80 mm Hg, nine (47 per cent) had a positive pulmonary angiogram. Thus, a cut-off point of 80 mm Hg for arterial POz was not diagnostic in our study. Because the mean age of our patients was 54 years, we also analyzed the data using a cut-off point of 70 mm Hg for arterial POs. Of the eighty-seven patients with an arterial PO2 of less than 70 mm Hg, thirtynine (45 per cent) had a positive pulmonary angiogram. Of the thirty-three patients with an arterial POs greater than 70 mm Hg, fifteen (45 per cent) had a positive pulmonary angiogram. Thus, a cut-off point of 70 mm Hg for arterial PO:! was not diagnostic for acute pulmonary embolism. It is interesting that of sixty-nine patients with a PO:! of 65 mm Hg or less, twenty-nine (42 per cent) had a positive pulmonary angiogram. Pulmonary Angiography. This was performed in 158 patients using the Seldinger Technique. The pulmonary angiogram was positive in seventy patients (44 per cent) and negative in eighty-eight patients (56 per cent). Comments

In diagnosing acute pulmonary embolism, many workers believe that appropriate clinical assessment

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along with the relevant laboratory data is sufficient for a correct diagnosis. We and others believe that acute pulmonary embolism has been overdiagnosed, overtreated, and inadequately diagnosed in many cases [7]. Although we presumed that pulmonary angiography was the most accurate method of diagnosis, this method has not gained widespread acceptance for many reasons. Pulmonary angiography involves invasion of a major vein and the passage of a catheter into the heart and the pulmonary outflow tract, in addition to multiple injections of contrast material and multiple serial X-rays. Because of this method’s invasiveness, the amount of time it requires, and its associated morbidity and mortality, many clinicians have favored the use of less invasive or noninvasive methods. The question at hand is the diagnostic accuracy of these other methods. The 158 patients in this study had pulmonary angiography for the presumptive diagnosis of acute pulmonary embolism. Sixty of 111 patients with a high clinical suspicion of pulmonary embolism were found to have a positive pulmonary angiogram. Thus, on the basis of clinical impression, if all the patients had received anticoagulant therapy for presumed pulmonary embolism, fifty-one patients would have been inappropriately treated. On the other hand, of forty-seven patients considered to have a low probability of acute pulmonary embolism, ten were found to have pulmonary embolism on angiography. On the basis of the clinical impression alone, these ten patients would not have been treated for pulmonary embolism. On the basis of clinical impression in a high probability group of patients, angiography will demonstrate pulmonary embolism in about 50 per cent of patients. These results agree with those of other authors [2]. Perfusion lung scanning technics have been dem-

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onstrated to be extremely sensitive in diagnosing acute pulmonary embolism. However, these technics are far too sensitive, and other clinical problems such as chronic obstructive pulmonary disease, asthma, chronic bronchitis, and atelectasis can result in a false positive diagnosis. In our study forty-eight of seventy-three patients (66 per cent) with a high probability lung scan had a positive angiogram. Thus twenty-five of seventy-three patients would have been inappropriately treated with heparin therapy if they had not had subsequent pulmonary angiography. This is slightly less accurate than the 77 per cent positive angiograms in a high probability lung scan group of Gilday et al [8]. Similarly, six of thirty-nine patients (15 per cent) with a low probability for pulmonary embolism based on perfusion scanning had pulmonary embolism demonstrated on angiography. These six patients would not have had adequate therapy if angiography had not been performed. In our study none of the five patients with a normal perfusion scan had a positive angiogram. This supports the findings of other authors that a normal lung scan can be believed and angiography is not indicated [a]. The results of a National Cooperative Study also show a poor correlation between lung scans and pulmonary angiography [9]. Ventilation-perfusion lung scanning has been shown to be more accurate than perfusion lung scanning [IO]. Because the experience at our institution includes complete data on only twenty patients, we are uncertain about what conclusions can be reached. The diagnostic accuracy of ventilationperfusion lung scanning in our study was high: eleven of twelve patients with a high probability for pulmonary embolism had a positive angiogram. Thus a pulmonary embolism would not have been detected in one patient without subsequent pulmonary. angiography. Two of eight patients with a low probability for pulmonary embolism had angiographically demonstrated pulmonary embolism. Information is now accumulating from other centers that ventilation-perfusion lung scanning technics are not as ac-

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Figure 5. The accuracy of diagnosis in a selected group of patients with a high clinical probability for acute pulmonary embolism in whom iung scans and pulmonary angiography were performed. PROB. = probability.

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Is pulmonary angiography essential for the diagnosis of acute pulmonary embolism?

Is Pulmonary Angiography Essential for the Diagnosis of Acute Pulmonary Embolism? James 0. Menzoian, MD, Boston, Massachusetts Lester F. Willlams, MD,...
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