Fatal Embolism Infrequent, but Fuels Overdiagnosis

Ingrid Hein

December 12, 2019

Michael Brant-Zawadzki, MD, remembers a 36-hour drive he took for a residency when he was in medical school. He drove straight through from California to Ohio. When he arrived, he didn't feel so good. "I had chest pain and I had trouble breathing," he said.

It wasn't until 6 months later when he was studying pulmonary embolism, that he realized, "Oh, I must have had one after that drive."

"I must have been dehydrated, and sitting for that long caused a blockage," he told Medscape Medical News. Fortunately for Brant-Zawadzki, the embolism was able to resolve by itself.

"There are people who have a pulmonary embolism and don't get treated and do just fine — it's not an outrageous hypothesis," he explained.

But not every pulmonary embolism can resolve on its own. According to the CDC, between 60,000 and 100,000 Americans die every year from deep venous thrombosis or pulmonary embolism and as many as 900,000 people could be affected.

But "who do you treat? That’s the real issue," said Brant-Zawadzki, from Hoag Memorial Hospital Presbyterian in Newport Beach, California.

When a patient is put on anticoagulation, a small percentage will have hemorrhages, he said. "It’s a small percentage, but it’s not zero."

Who should be treated is not always agreed upon by radiologists, but in a Controversy Session on overdiagnosis and overtreatment at the Radiological Society of North America 2019 Annual Meeting in Chicago, presenters did agree on one thing: not all pulmonary embolisms are equal.

There are those that are asymptomatic, those that are found "by accident," and others that present with right heart failure or pulmonary infarction.

Pulmonary embolisms that present with right-sided heart failure are the ones that should be treated, said Linda Haramati, MD, from Albert Einstein College of Medicine in New York City.

"We now know that when the right heart is under strain it's a riskier pulmonary embolism, a more dangerous situation," she told Medscape Medical News. Of the patients who die of pulmonary embolism, "most have shown signs of heart strain on EKG and CAT scan."

Many of the other cases are more of a "watch and wait" situation, she said.

As far back as 1977, clinicians have been raising questions about the overdiagnosis of pulmonary embolism leading to unnecessary anticoagulation therapy (Ann Intern Med. 1977;87:775-781).

This concern has grown since computed tomography pulmonary angiography (CTPA) overtook scintigraphy as the dominant imaging modality for pulmonary embolism, write Haramati and Stephanie Tan, MD, from the Montreal Heart Institute in Canada, in an article titled "Are We Overdiagnosing Pulmonary Embolism? Yes!" (Journal of Thoracic Imaging. 2018;33:346-347).

It is clear that the question has not yet been settled, Haramati told Medscape Medical News. The body has the capacity to filter small clots, "but there's a range of normal to deadly. Sometimes we don't know which are which. We have strong feelings about where the sweet spot is, but we don't really know."

As the radiologist, "I feel like I'm the one that needs to bring the information to the discussion," she added. "Radiologists can't just say to the care team, 'There's a small pulmonary embolism, I don't know what to do about it.' "

"Understanding overdiagnosis requires us to grasp the concept that PE is a complex process that ranges from normal physiology to a fatal event," Haramati and Tan conclude. "Patient-centered care requires us to shine a bright light on this complexity and lead investigations with the goal of improving outcomes."

But not everyone agrees that pulmonary embolism is being overdiagnosed.

Too Much Uncertainty

"Although it is our responsibility to describe the potential drawbacks of a powerful imaging modality, it is also mandatory to keep in mind the numerous areas of uncertainty with regard to acute PE that should keep us from considering that we are overdiagnosing acute PE," writes Martine Remy-Jardin, MD, PhD, from Hospital Calmette in Lille, France (Journal of Thoracic Imaging. 2018;33:348-349).

Remy-Jardin sees other discrepancies in the diagnosis process. Are all patients with pulmonary embolisms "of minimal clinical significance really asymptomatic?" she asks. "Probably not, as 75% of patients with unsuspected PE actually did have symptoms, which were overlooked by the referring physicians," she writes, referring to a study on unsuspected PE in patients with cancer (J Clin Oncol. 2006;24:4928-4932).

Remy-Jardin goes on to argue that the questions surrounding the natural history of pulmonary embolism are unresolved, and the answers might hold clues to understanding other diagnoses.

"Could we find in these silent forms of acute pulmonary embolism the missing link between acute PE and chronic thromboembolic pulmonary hypertension (CTEPH)?" she suggests.

Brant-Zawadzki predicts that "overdiagnosis is going to happen no matter what." Frequently, the discussion about overdiagnosis is framed as "we don't need more radiation," he said, pointing to similar discussions in mammography and prostate cancer imaging.

From a value perspective, he said, it's important that unnecessary scans are not administered, "but we want to optimize outcomes, so if that means treating incidentally found PE, we should treat it."

However, if someone has a risk factor, be it an aneurysm or a liver or kidney laceration that's not severe enough to operate on, "you don't want to cause a bleed with anticoagulation," Brant-Zawadzki said.

It's the blockages in the lungs when the heart doesn't feel any strain that are more challenging, he acknowledged. "Do you treat those? We don't have a clear answer for that — we decide on a case-by-case basis."

Radiological Society of North America (RSNA) 2019 Annual Meeting: Controversy Session SPSC20. Presented December 2, 2019.

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