CT perfusion angiography exams have largely replaced nuclear medicine-based ventilation/perfusion (V/Q) studies for detecting pulmonary embolism. But a new article in Academic Radiology suggests that CT’s rise wasn’t entirely based on clinical efficacy – fears of malpractice risk may have played a role.
V/Q studies can help diagnose PE by enabling clinicians to visualize lung perfusion, showing defects such as blockages in pulmonary vessels. The scans are typically performed in three phases …
- An albumin injection to show pulmonary vasculature.
- A radiopharmaceutical that’s inhaled and imaged with a gamma camera.
- A chest radiograph to correlate findings.
The scans dominated PE imaging in the 1980s, but the rise of CT saw radiology facilities begin to shift.
- CTPA was seen as having higher spatial resolution and was easier to perform than nuclear medicine exams.
But the new article suggests that there were other forces at work as well – in particular, fear of malpractice risk from PEs that weren’t adequately followed after inconclusive V/Q exams.
- The problem originated with clinical guidelines for V/Q reporting that classified some 20% of V/Q studies as “low probability” for PE when they probably would have better been classified as “inconclusive” or “non-diagnostic.”
As a result, a number of “low probability” patients weren’t followed up adequately, with tragic results that later figured into medical malpractice cases …
- A patient who was diagnosed with pneumonia after an inconclusive V/Q exam, sent home, and died one day later of a “massive” PE.
- A patient with leg and chest pain who was given heparin after a negative V/Q scan and later suffered internal hemorrhage; fortunately she survived.
- A patient with “vague symptoms” who had an inconclusive V/Q scan and later died of an undiagnosed PE that some claimed would have been detected on CTPA.
Indeed, the theme of PE malpractice cases began to shift over time, from failure to diagnose V/Q scans to failure to order CTPA exams – which were soon seen as the clinical gold standard.
The Takeaway
Given the fast pace of development in radiology, it’s inevitable that some technologies that were once clinical staples fall by the wayside. But the new article offers a fascinating look at how clinical language can lead to medico-legal concerns that influence physician behavior – often in ways that are impossible to detect as they happen.
