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Transcranial Doppler superior for detection of PFO
SAN DIEGO — New research indicates that transcranial Doppler is superior to transesophageal echocardiography for the detection of patent foramen ovale.
Patients with PFO are at increased risk for paradoxical embolism, which is the cause of 4% to 5.5% of strokes, J. David Spence, MD, of the Robarts Research Institute of Western University in London, Ontario, Canada, said at the International Stroke Conference. However, it is not clear which patients with PFO are likely to have paradoxical embolism, and risks associated with percutaneous PFO closure restrict its use as a prophylactic measure.
Recent research demonstrated that septal aneurysm and septal mobility do not predict paradoxical embolism in those with PFO, but results from a small study indicated that transcranial Doppler shunt grade could be a predictor, Spence said.
J. David Spence
The researchers conducted a study to compare the performance of transcranial Doppler with transesophageal echocardiography (TEE), the standard method for diagnosing a right-left shunt such as PFO. They hypothesized that transcranial Doppler saline studies would be more sensitive, in part because sedation for TEE could prevent an adequate Valsalva maneuver.
The study included 340 patients (mean age, 53 years, 61.5% women) with cryptogenic stroke and suspected paradoxical embolism who were referred to an urgent transient ischemic attack clinic from 2000 to 2013.
Right-left shunt was detected in all 340 patients by transcranial Doppler, but TEE failed to show right-left shunt in 15.4% of patients, according to Spence. “In some cases, it missed quite big shunts,” he said. Of the missed shunts, a quarter were grade 3 or higher.
During median follow-up of 420 days, 85 patients had a recurrent ischemic stroke or TIA. Survival free of stroke was predicted by transcranial Doppler shunt of grade 3 or more (P=.008), but not by TEE (P=.6), Spence said.
“We found that transcranial Doppler is better for both diagnosing (because it is more sensitive), and risk stratifying,” he said, noting that the technologies are complementary because “you need [TEE] to find other causes of stroke from the heart.” – by Erik Swain
For more information:
Spence JD. Plenary Session III: Abstract LB10. Presented at: International Stroke Conference 2014; Feb. 12-14, 2014; San Diego.
Disclosure: Spence reports no relevant financial disclosures.
Perspective
Back to TopWe don’t yet know whether patent foramen ovale closure is an effective treatment for those who do have a bona fide paradoxical embolism. But, it makes a lot of sense that if there is a way to detect that subgroup of people with PFO who are going to be at highest risk for future stroke, then PFO closure in that subgroup would have the best chance of preventing enough strokes to justify any procedure-related complications.
Perspective
Back to Top
A PFO is a very common remnant from fetal circulation, present in approximately 25% of the population. Paradoxical embolism via right to left shunt across the interatrial septum accounts for roughly 5.5% of all ischemic strokes. However, because PFOs are so common, a significant majority of PFOs found during a stroke work-up are incidental. Multiple recently completed randomized studies have failed to show significant benefit in PFO closure compared with medical therapy in stroke prevention. Detection of a PFO is accomplished by demonstrating a right to left shunt with a transthroacic echocardiogram (TTE), a TEE or transcranial Doppler (TCD) performed with agitated saline. Noninvasive methods such as TTE or TCD are considered first-line, while TEE is utilized if suspicion still exists despite negative noninvasive testing. Although TEE is considered the gold standard in PFO detection, multiple studies have shown that transcranial Doppler saline studies are more sensitive than TEE.
The current study prospectively looked at PFO detection by TEE in patients with cryptogenic stroke with right to left shunt on transcranial Doppler saline studies. TEE failed to detect right to left shunt in 15% of patients and thus TCD was shown to be superior to TEE. In addition, 25% of the right to left shunt missed by TEE were large shunts (Spencer grade 3-5). Not only did they show that TEE had high false negative rate, but a significant number shunts missed by TEE were not small.
The superiority of TCD in the detection of PFO is likely in part due to an inadequate Valsalva maneuver during TEE. TCD is less invasive compared with TEE, which carries inherent risks for anesthesia, aspiration and esophageal damage. TCD is a very useful diagnostic tool for PFO detection and in cases where the question is whether a patient has a PFO it may obviate the need for TEE. However, TEEs are still warranted if a more detailed look at the interatrial septum is desired or if further search for other cardiac causes of stroke, such as left atrial thrombus or endocarditis, are indicated.
Further research is warranted to compare TTE with TCD in the detection of PFO.