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Neurology Today:
News From the American Stroke Association Annual Meeting

Patent Foramen Ovale – New Data on Benefits of Transcatheter Detection and Closure

Laino, Charlene

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SAN DIEGO, CA — More patients than previously realized may benefit from transcatheter closure of patent foramen ovale (PFO), suggest two new studies that found the strategy is effective for the elderly and those with atrial septal aneurysm. A third study points to a novel technique for detecting PFOs that may be superior to the standard diagnostic method.

All three studies were presented here at this year's American Stroke Association Annual Meeting.

Robert J. Sommer, MD, Director of Adult Congenital Heart Disease at Lenox Hill Hospital in New York, NY, reported that transcatheter closure is as safe and effective in older patients as in younger patients.

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IS AGE OF PATIENTS IMPORTANT?

In the study of 364 consecutive patients who had successful PFO closure after a stroke or transient ischemic attack (TIA) between June 2000 and April 2003, none of those over age 55 years had a second stroke or other neurologic event, compared with 1.3 percent of younger patients, a non-significant difference.

Also, the acute procedural complication rate was 3.6 percent in those over age 55 years, compared with 4.8 percent in younger patients, again not significant, Dr. Sommer reported.

“We found no difference in the response or complication rates between the young and the old,” he said. “The elderly derive the same benefit as the young and should not be excluded from PFO closure.”

PFO, which results when the natural closure of a flap in the wall of the heart fails to occur, often goes undetected until a patient has a stroke, or when it is discovered as an incidental finding during an echocardiogram, Dr. Sommer said. If the PFO is not closed, researchers believe, small emboli may pass from the right atrium into the left atrium resulting in a blockage, which can lead to a stroke.

Not all of these defects lead to medical complications, “but once a stroke or TIA occurs in a patient with PFO, there is substantial risk, ranging from 4 to 11 percent each year, of having additional neurologic events,” he said.

Seeking to find an explanation for a stroke or TIA in the otherwise healthy younger patients, physicians typically consider a PFO diagnosis; if confirmed, the patient undergoes transcatheter closure, which is effective at preventing a second stroke, he said.

But physicians have traditionally – and, in his view, erroneously – overlooked PFO as a cause of stroke in the elderly, which essentially denies them the potentially lifesaving closure procedure, according to Dr. Sommer.

Figure. Dr. Robert J...
Figure. Dr. Robert J...
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STUDY PROTOCOLS

Seeking to change that, his institution “made it policy to screen all stroke and TIA patients for PFO, and we found a significant number in older people,” he said. All the patients then underwent successful PFO closure.

Of the 364 patients studied, 134 (36.8 percent) were 55 years or older at the time of the procedure. Among the other 230 patients, the mean age was 40 years. Over a mean follow-up period of 14 months, there were no recurrent neurologic events in the older patients, while there were two strokes and one transient ischemic attack among the younger group.

Acute procedural complications among the older group included two cases of atrial fibrillation (both reversible), two large hematomas at the catheter site, and one dystonic reaction to sedatives. Dr. Sommer said there was no difference in the rate of post-catheter fever, late death, transient breathlessness, chest pain, or headaches among the two groups.

Also, the rate of new onset atrial arrhythmia requiring therapy was comparable: 13.4 percent in the older group compared with 16.9 percent in the younger group, a non-significant difference. “However, of those patients, 11 of the 18 older patients and only one of 39 younger patients developed atrial fibrillation,” Dr. Sommer reported. But nine of the older patients converted to normal sinus rhythm within 48 hours of initiating medical therapy, he added. “While older patients seem more prone to developing atrial fibrillation, it seems to respond readily to simple medical therapy,” he said.

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MORE STUDY NEEDED, EXPERT SAYS

Figure. Dr. William ...
Figure. Dr. William ...
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Marc Mayberg, MD, Professor and Chair of the Department of Neurological Surgery at the Cleveland Clinic Foundation, said that further study is needed.

While the research shows the procedure is relatively safe, a randomized study with a control group is needed to show efficacy, he said. In fact, further study is needed just to better define the clinical importance of PFOs, Dr. Mayberg said.

“No one has really shown that PFOs are that major in the elderly,” he explained. “The fact that an elderly person who has a stroke has a PFO doesn't mean the PFO is the cause of the stroke.”

“There is likely an association between PFO and stroke, but no one knows exactly what that association is,” he said. “Until that is known, we won't know if the risks and complications of the [transcatheter closure] procedure are outweighed by its benefits.”

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ROLE OF ASA IN PROCEDURE

In a separate study, Seattle researchers found that transcatheter PFO closure can be successfully performed in the presence of a coexisting atrial septal aneurysm (ASA).

“We asked the question, Does ASA change the closure rate with the device?” said William A. Gray, MD, Director of Endovascular Care at Swedish Medical Center. “The answer: By and large, there was no difference. They close at the same rate.”

Dr. Gray said his team was surprised at the findings, as they had hypothesized that following transcatheter PFO closure, patients with coexisting ASA would have a significantly larger residual right to left shunt reduction and lower closure success rate than patients without ASA.

Commenting on the study, Dr. Sommer noted that ASA makes the heart wall more floppy, so people used to be nervous about doing transcatheter closure. “But we have found it makes no difference [in the response or complications rates].”

In fact, since PFO patients with coexisting ASA are at heightened stroke risk compared with those with PFO alone, “it is even more imperative to get their holes closed,” Dr. Sommer said.

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HOW PROCEDURE WAS ASSESSED

The study by Dr. Gray included 84 patients with documented cryptogenic ischemic stroke or TIA undergoing transcatheter PFO closure. Thirty patients (36 percent) – 67 percent of whom were women – had a coexisting ASA; their mean age was 62 years. In the PFO group without ASA, 56 percent were women and the mean age was 51 years.

All the patients were examined prior to and following transcatheter PFO closure, with contrast transcranial Doppler used to quantify right to left shunt reduction and detect microemboli in the cerebral circulation during calibrated respiratory strain.

During the PFO closure procedure, intracardiac echocardiography was used to assess interatrial septum morphology and the presence of ASA. PFO balloon stretch diameter was 13.5 mm in patients with ASA, compared with 12.2 mm in patients without ASA, a non-significant difference, Dr. Gray reported. Also, although patients with ASA had a higher number of microemboli in the cerebral circulation prior to and following PFO closure, the differences between the two groups were again not significant, he said.

“What this means,” Dr. Gray told Neurology Today, “is that high-risk patients with PFO and ASA are still good candidates for the procedure, rather than more invasive surgery. While this is an early look and more numbers would be helpful, based on these findings, we can now proceed with transcatheter closure in PFO patients with coexisting ASA with confidence.”

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MRI AS DETECTION TOOL

In a third study, New York researchers reported they had developed an MRI technique that offers advantages over traditional PFO diagnostic methods.

In a study of 24 patients, the MRI technique proved superior to transthoracic echo and at least as effective as the more invasive transesophageal echo in PFO detection, reported lead researcher Vernice Bates, MD, President of the Dent Neurologic Institute in Amherst, NY.

Co-investigator Mark Hekler, MD, a neuroimaging fellow at Dent, told Neurology Today that traditionally, “it has been difficult to visualize a PFO using MRI because of movement artifacts,” making echocardiography the standard means of detection.

Figure. Dr. Mark Hek...
Figure. Dr. Mark Hek...
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The researchers made some progress on the problem by manipulating the contrast on an MR image.

For the study, 10 consecutive patients with PFOs diagnosed by transthoracic echo and 10 consecutive patients with PFOs diagnosed by transesophageal echo were evaluated using the cardiac MRI technique. “MRI not only accurately identified the PFO in all 20 patients, but the exact size could be measured and flow patterns in the distal inferior venae cava could be assessed,” Dr. Bates reported.

Also, in four additional patients shown to have a PFO by MRI, two had a false negative on transthoracic echo, one had a false negative transesophageal echo, and one had an unsuccessful transesophageal echo, he said.

“The MRI technique allows us to actually visualize and measure the opening as well as provide information about flow patterns,” said Dr. Hekler. He noted that both the size of the opening and flow patterns may influence the degree of right to left shunting and therefore the PFO's embolic stroke potential. “Given these findings and the noninvasive nature of MRI, it offers an attractive imaging modality for evaluating PFO in stroke,” he said.

©2004 American Academy of Neurology

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