SAN DIEGO — An alternative test for measuring blood flow to the brain detected a potentially dangerous hole within the heart of some patients with an unexplained stroke better than a standard test, according to late-breaking science presented at the American Stroke Association’s International Stroke Conference 2014.
In addition, the transcranial Doppler test could differentiate the risk of future stroke or transient ischemic attack (TIA) as related to the severity of the defect.
An echocardiogram uses ultrasound to see if bubbles injected in a vein have flowed from the right side of the heart to the left side (through the top chambers of the heart called the atria), while the trancranial Doppler detects the bubbles in the brain arteries, said J. David Spence, M.D., senior researcher for the study and director of the Stroke Prevention & Atherosclerosis Research Centre, Robarts Research Institute at Western University in London, Ontario, Canada.
Previous research indicates that 25 percent of the population, and a higher percentage of patients who have had unexplained strokes, have a patent foramen ovale (PFO), which occurs when an opening between two heart chambers fails to close at birth. Many people never have symptoms. However, such a hole, or “shunt,” can allow a blood clot that forms in a vein to escape from the right to the left side of the heart, enter the arteries to the brain and cause a stroke (paradoxical embolism).
Researchers tested whether PFOs already detected by transcranial Doppler would also be found by transesophageal echocardiography, a widely used approach.
Echocardiography — which included contrast dye before saline bubbles were injected — failed to find the PFO in more than 15 percent of the 340 patients in the study with the defect, the researchers reported.
Researchers did not investigate whether transcranial doppler detected all such defects in patients with PFO found by echocardiogram.