BOSTON—Transesophageal echocardiography has a 30% false-negative rate for detecting patent foramen ovale (PFO) among patients with high-grade right-to-left intracardiac shunts, researchers determined using power M-mode transcranial Doppler (pmTCD). This suggests that a negative transesophageal echocardiography finding should not be considered the gold standard in ruling out a right-to-left shunt, James W. Banks, MD, and colleagues reported at the 50th Annual Scientific Meeting of the American Headache Society.
The researchers evaluated 50 patients from a headache specialty clinic who had a high risk for stroke or right-to-left intracardiac shunts; migraine with aura and/or white matter lesions determined them as high risk. All underwent pmTCD of either bilateral or unilateral insonation of the middle cerebral arteries using agitated saline/blood contrast injected at rest and with calibrated Valsalva (40 mm Hg sustained for 10 seconds). A grade of 1 or 2 was positive but insignificant. A grade of 3 to 5 was considered positive and significant.
Twenty patients (40%) had significant right-to-left shunts; 17 underwent echocardiography, which confirmed PFO in 11 participants (65%). The remaining had a negative transesophageal echocardiography; PFO was later confirmed with use of cardiac catheterization or repeated transesophageal echocardiography. Twelve patients had a positive but insignificant finding, and one had undergone transesophageal echocardiography that was negative for PFO, “but this patient had stroke on MRI and was found to have a hypercoagulability disorder,” stated Dr. Banks, Associate Director of the St. John’s Mercy Medical Group–Ryan Headache Center and Mercy Health Research in St. Louis. Among those with significant right-to-left shunts, 75% had migraine with aura, and 60% had abnormal MRI.
“pmTCD with calibrated Valsalva maneuver has a higher degree of specificity, positive predictive value, and more importantly, nearly perfect negative predictive value,” noted Dr. Banks. “Interestingly, 95% of the patients with a significant right-to-left shunt had a marked increase in the degree of the shunt after Valsalva maneuver compared to at rest. The inability of patients to sustain a Valsalva maneuver during transesophageal echocardiography may be a contributing factor to the high false-negative rate,” Dr. Banks said. A trend toward significance was observed regarding headache characteristics predicting a positive and significant right-to-left shunt on pmTCD, such as migraine with aura and abnormal MRI.
“Whether PFO should be screened for and intervention made—for example, closure—for treatment of migrane is far too preliminary,” reported Dr. Banks. “However … there is a plausible association between PFO with right-to-left shunt, stroke risk, and abnormal MRI in patients with migraine with aura.”