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Figure: pulmonary embolism, syncopeA patient shows up in the emergency department after a temporary syncopal episode. Emergency physicians know the cause is usually benign, but something more problematic can be afoot—an arrythmia, a heart attack, a significant hemorrhage, or a pulmonary embolism. Diagnosing the other problems is fairly easy, but identifying a pulmonary embolism can expose patients to significant radiation. The question is, “Are those tests justified?” The answer, unfortunately, has been equivocal. The 2016 Pulmonary Embolism in Syncope Italian Trial (PESIT), for instance, evaluated 560 hospitalized patients who had a first episode of syncope, and found that one in six had an underlying pulmonary embolism, an incidence strikingly higher than had been previously suspected. (N Engl J Med. 2016;375[16]:1524; http://bit.ly/2TxiU4D.) A recent study at the Sorbonne Université by Yonathan Freund, MD, and colleagues analyzed 411 syncope patients with no chest pain or difficulty breathing who had formal workups for PE, including a D-dimer and further imaging studies if the D-dimer was positive. (Eur J Emerg Med. 2019;26[6]:458.) That imaging included a computed tomography pulmonary angiogram in 128 patients and a ventilation-perfusion scan in nine. Nine patients with isolated syncope had a confirmed PE, translating into a prevalence of 2.2 percent, leading the researchers to conclude that that was not low enough to negate a PE workup even if the patient did not have chest pain or dyspnea. The study's 95% confidence interval, however, prevented the researchers from making a definitive recommendation. Dr. Freund wrote in an email interview with EMN that he thought this question would never be definitively answered. He pointed to a study in the Journal of the American College of Cardiology that found the prevalence of pulmonary embolism was 1.4 percent with a 95% confidence interval. (2019;74[6]:744.) He noted that the result was in line with his study and that “whether this low prevalence should warrant a systematic research of PE is unknown.” PE Risk Dr. Freund said the decision to do a PE workup is best left to the physician's discretion. “Since the two studies were published, we tend to test more patients with syncope and no signs of chest pain or dyspnea,” he said. “What may have changed is that we used to consider PE only in patients with cardiac syncope, i.e., no prodrome. Now we can consider PE patients in whom we have concluded vasovagal syncope, but we do it under a Bayesian approach with an estimation of the global PE risk.” He said his study differed from PESIT, which included only patients admitted to the hospital for reasons that were not explained in the report. “In our sample, the vast majority of patients were discharged from the emergency department,” Dr. Freund said. “Moreover, in the PESIT study, they included patients with chest pain or dyspnea, which would have mandated a PE workup in either case.” Across the Atlantic, Venkatesh Thiruganasambandamoorthy, MBBS, MSc, of the Ottawa Hospital Research Institute, and his colleagues analyzed data from 9091 patients; a total of 547 were assessed for PE—278 had a D-dimer, 39 had a ventilation-perfusion scan, and 347 had CT pulmonary angiography. (Ann Emerg Med. 2019;73[5]:500.) Overall, 874 patients (9.6%) had serious outcomes at 30 days—818 with a non-pulmonary embolism serious outcome and 56 with pulmonary embolism. Eighty-six patients (0.9%) died, four related to PE. The researchers concluded that the prevalence of pulmonary embolism was extremely low—0.6 percent—among the syncope patients who arrived at the emergency department. “Although an underlying pulmonary embolism may cause syncope, clinicians should be cautious about indiscriminate investigations for pulmonary embolism,” they wrote. Dr. Thiruganasambandamoorthy said he and his colleagues sought “to prevent excessive and unnecessary investigations for PE among low-risk patients” in the wake of the PESIT study that investigated all patients hospitalized for syncope “and reported that a very high proportion of patients were diagnosed with PE, contrary to the previous literature.” His results differed from those of the French study because the other study had a small sample size and a large confidence interval, he said, noting that overall the prevalence of PE among ED patients with syncope is low. The question remains, however, about whether specific subgroups such as those with cancer need a pulmonary embolism workup, he said. If an underlying PE is found, what is its relationship to syncope and the clinical significance? Choose D-Dimer, not CT Daniel D. Dressler, MD, MSc, a professor of medicine at Emory University School of Medicine in Atlanta, reviewed Dr. Freund's study for the New England Journal of Medicine, and said the results from the D-dimer test were interesting. As an internist and hospitalist who works with emergency physicians, he agreed that the question was what to do with a patient with syncope and no other symptoms. The history and physical can provide an answer in some cases, he said. “Do I need to admit this patient? If I don't have clear evidence based on history and physical exam and [ECG], should I admit or check for D-dimer?” Dr. Dressler said. “If it's negative, then I'm done. If it's positive, then the patient may have other problems and doing further evaluations may be reasonable. We may use a positive D-dimer to admit the patient to the hospital.” Dr. Dressler said he was reluctant to recommend a lot more chest CTs to look for PE. “We will be exposing people to a lot more radiation if we do this,” he said. A good history and physical, an ECG, and a D-dimer are likely to identify the patients with pulmonary embolism, Dr. Dressler said. “That's where I'm standing at the moment based on the literature that's available and also maintaining the balance to avoid exposing more people to more radiation.” Share this article on Twitter and Facebook. Access the links in EMN by reading this on our website, www.EM-News.com. Comments? Write to us at [email protected]. Ms. SoRellehas been a medical and science writer for more than 40 years, previously at the University of Texas MD Anderson Cancer Center, the Houston Chronicle, and Baylor College of Medicine. She has received more than 60 awards, including the Texas Human Rights Foundation Award. She has been a contributor to EMN for more than 20 years.

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