SAN DIEGO – Transcranial Doppler saline studies were superior to transesophageal echocardiography in diagnosing a hole in the heart, according to a prospective study of patients who had a cryptogenic stroke.
Researchers analyzed data from 340 patients with cryptogenic stroke suspected of paradoxical embolism who had had their right-left shunt confirmed with transcranial Doppler saline study (TCDSS). Transesophageal echocardiography (TEE) failed to show a shunt such as patent foramen ovale (PFO) in 15% of the cases.
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Courtesy Dr. J. David Spence, Robarts Research Institute
"I was surprised by the number," said Dr. J. David Spence, senior researcher of the study, who presented the findings at the International Stroke Conference, sponsored by the American Heart Association. "I had realized that some of the patients with shunts were missed by TEE, ... but I was surprised by how often that happened."
Nearly a quarter of the population has a PFO, and 4.0%-5.5% of strokes are due to paradoxical embolism through a right-left shunt. But patching the shunts isn’t the simple answer, because the procedure is not without complications, and so far, the studies haven’t been able to make a strong case for the procedure.
TCDSS is an ultrasound method in which 1 mL of tiny bubbles is injected into the vein and if detected in the brain, could give clues to a right-left shunt. The method is safer, the equipment is cheaper, and the training is faster than for TEE, Dr. Spence said.
He added that one reason that TCDSS may be more sensitive than TEE is that sedation for TEE may prevent an adequate Valsalva maneuver. He also showed in a video that detecting the bubbles in TCDSS is rather straightforward.
Given the findings of his study, Dr. Spence said that there’s a need to identify which PFO patients are more likely to have paradoxical embolism and are more likely to respond to patching.
One solution is paying attention to the clinical clues of paradoxical embolism (J. Neurol. Sci. 2008;275:121-7). And Dr. Spence’s recent findings may add another tool to help with this prediction.
Dr. J. David Spence
Aside from the superiority of TCDSS to TEE in identifying PFO, Dr. Spence and his colleagues found that TCDSS was also better for risk stratification of PFOs. The analysis found that 25% of the shunts that were missed on TEE were high-grade shunts (Spencer grade 3 or higher). Patients with a shunt grade of 3 or higher were significantly more likely to have a stroke or transient ischemic attack in the 4-year follow-up period (P = .028), said Dr. Spence, director of the Stroke Prevention & Atherosclerosis Research Centre at the University of Western Ontario, London. This was not predicted by the presence of shunt on TEE, nor was it predicted by mobile atrial septum or septal aneurysm. TEE missed nearly 46% of grade 1 shunts, 32% of grade 2, 13% of grade 3, 7% of grade 4, and almost 5% of grade 5.
"This doesn’t mean that everyone should go pack up their TEE machines, because we still need it for diagnosis of other cardioembolism," said Dr. Spence. "But these techniques can be complementary."
He added that it’s too soon to use these findings as grounds for change in clinical practice, and there’s a need for further studies such as randomized trials.
The majority (62%) of the study’s 340 patients were female. The patients had a mean age of 53 years and underwent follow-up for a median of 420 days. All the patients, who visited the center between 2000 and 2013, had cryptogenic stroke and were suspected of having paradoxical embolism. A total of 280 cases had TEE data available.
Dr. Spence said he had no disclosures relevant to the study.
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