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Transcranial Doppler (TCD) ultrasound is not only better than transesophageal echocardiography (TEE) at identifying patent foramen ovale (PFO), it also better predicts the risk of embolic events at 5 years. The findings were presented February 14, 2014, at the International Stroke Conference in San Diego, CA.
J. David Spence, MD, of the Robarts Research Institute at Western University (London, Canada), and colleagues looked at 340 patients in whom TCD saline studies had detected a right-to-left shunt (RLS). All had been referred to the Urgent TIA Clinic for cryptogenic stroke and suspected paradoxical embolism between 2000 and 2013.
TEE studies, which were available for 280 patients, failed to show RLS in 43 cases (15.4%). Among patients with a negative echo, nearly a quarter had high-grade shunts on TCD:
Over a follow-up period of 35 ± 27 months (median 420 days), 85 patients (25%) experienced recurrent ischemic stroke or TIA. Kaplan-Meier analyses demonstrated that TCD grade 3 or higher predicted poorer event-free survival at 5 years (P = 0.028), whereas RLS on TEE did not (P = 0.42).
Tests Are Complementary
In an email, Dr. Spence told TCTMD that it is not possible for TCD to over detect PFO. The test results are “entirely believable,” he said, in that “TCD bubbles are very definite.”
Importantly, TCD is “not only more sensitive but more predictive of the risk of events. This is a key issue in trying to decide who might benefit from closure of the PFO,” Dr. Spence stressed.
But there is still a place for TEE, he added, noting that the tests should be considered “complementary.” TCD can only diagnose RLS, whereas TEE is required to detect other cardioembolic sources of stroke such as left atrial appendage thrombus, left atrial myxoma, ventricular aneurysm and dyskinesia, and valve problems.
Strengths Beyond Sensitivity
Robert J. Sommer, MD, of Columbia University Medical Center (New York, NY), said that in his experience, the false negative rate of RLS with TEE vs TCD was 10%.
Dr. Sommer suggested several explanations for the disparity between the tests.
“The sedation required for TEE does not permit as strong a Valsalva effort as in an awake patient,” he said in an email with TCTMD. Moreover, the RLS finding is nonspecific and can be related to pulmonary AV malformation.
Finally, Dr. Sommer noted that the ability to detect PFO “can be very position dependent. For example, patients with platypnea-orthodeoxia syndrome have a dramatic increase in RLS creating hypoxemia when in an upright position. TCD is usually done more sitting (at a 30-degree upright position), whereas TEE is usually performed lying flat with some left oblique positioning. Some TCD investigators routinely test patients in multiple positions.”
TCD has a number of assets, he pointed out: “TCD is a very simple test to do. It can be done in the office without sedation, and without the patient even needing to get undressed. It takes less than ten minutes to perform, making it a much shorter undertaking than echo.”
While the sensitivity of TCD is valuable, “the clinically important shunts are those greater than grade 3, in my opinion,” Dr. Sommer emphasized.
Mean patient age was 53 years, and 61.5% were female.
Tobe J, Bogiatzi C, Munoz C, et al. Transcranial Doppler is superior to echocardiography for detection of patent foramen ovale. Presented at: International Stroke Conference; February 14, 2014; San Diego, CA.