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ATLANTA -- Patients with pulmonary embolism (PE) brought to emergency rooms because they had passed out tended to have the most ominous risk factors for poor outcomes, a researcher said here.

And, curiously, such patients were very often travelers passing through one of the world's busiest airport hubs, said Robert Rifenburg, MD, of Resurrection Medical Center in Chicago, during a poster session at the American College of Chest Physicians annual meeting.

Analyzing records of all patients diagnosed with PE at the hospital's emergency department from 2006 to 2011, Rifenburg and colleagues found that those presenting with syncope were significantly more likely to have large or saddle embolisms, greater right ventricular hypertrophy, and more nonspecific ST-T wave changes on electrocardiography.

These factors signal relatively severe types of PE, Rifenburg told MedPage Today.

The study also revealed that, of the patients with PE who came to the hospital from nearby O'Hare International Airport, almost half did so because they had lost consciousness, whereas less than 10% of cases from elsewhere in the Chicago area presented with syncope.

Individuals needing emergency treatment at O'Hare are normally brought to Resurrection Medical Center, Rifenburg explained.

He said that air travel is a known risk factor for deep vein thrombosis and PE, but not enough of one to explain such a vast difference in presentation.

The study data did not provide a specific explanation, Rifenburg said. However, it may simply be that airport travelers with shortness of breath or other, less severe PE symptoms go on to their final destinations before seeking medical help.

Other studies have shown that from 13% to 30% of PE patients have syncope as their presenting complaint, he said.

In the current study, with 548 cases of PE analyzed over the 6-year period, 27 came from O'Hare and the remaining 521 from elsewhere in the hospital's catchment area. Of the 548 total cases, 55 came to the hospital primarily because of syncope.

While the 27 airport cases represented only 5% of the total, 13 of them presented with syncope -- 48% of the airport cases. Among the 521 PE cases originating elsewhere, only 42 (8%) presented with syncope.

But that wasn't the main point of the study, Rifenburg said. It was designed to determine whether PE presenting with syncope represented a unique form of PE. The answer appeared to be yes.

One major difference between the syncope-presenting PE cases and others was that about 15% of the former were found to involve saddle embolisms, compared with 4% of non-syncope cases (P=0.003).

Also, two-thirds of non-syncope patients had normal echocardiography results, versus 49% of the syncope patients (P=0.025). Evidence of right ventricular hypertrophy was seen in 13% of the nonsyncope patients and 38% of those with syncope (P<0.001).

Other echocardiography and serum markers, including hypokinesis, pericardial effusion, and cardiac troponin, did not differ between the patient groups.

The bottom-line clinical implication, Rifenburg said, is that emergency department physicians should recognize that, when patients evaluated for syncope turn out to have PE, the likelihood of relatively severe vessel occlusion is much greater than with other PE presentations.

Some of these findings were supported in a separate single-center analysis, looking at the relationship between syncope and PE from the other direction, presented at the ACCP meeting by Krittika Teerapuncharoen, MD, of Albert Einstein Medical Center in New York City.

The goal of her study was to examine features predictive of PE in patients presenting with syncope.

She and colleagues analyzed records of 243 patients examined for syncope, of whom 26 were diagnosed with PE, or about 11%.

In line with Rifenburg's data, the syncope patients with PE were more likely to show right ventricular hypertrophy on echocardiography (odds ratio 6.71, 95% CI 1.56 to 28.93, P=0.011).

Other significant markers of PE in patients with syncope at Albert Einstein included moderate or high risk according to Weill's criteria, chest tightness, oxygen desaturation, and electrocardiography findings of new right bundle branch block. These were overrepresented in the PE group with odds ratios ranging from 3.88 to 29.39, all P<0.05, Teerapuncharoen reported.

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