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Up to one third of patients with patent foramen ovale (PFO) experience oxygen desaturation after exercise, a condition that is greatly ameliorated by closure of the defect, according to findings in the April 2012 issue of JACC: Cardiovascular Interventions.
Researchers led by Richard A. Krasuski, MD, of the Cleveland Clinic (Cleveland, OH), prospectively followed 50 patients with newly diagnosed PFO seen at a single center. The patients underwent standardized assessment for arterial oxygen saturation with pulse oximetry during postural changes and stair-climbing exercise to assess the incidence of provoked exercise desaturation, defined as a sustained arterial desaturation of 8% to 90% compared with baseline.
It has been hypothesized that rigorous exertion might alter the pressure gradient enough to induce a transient right-to-left shunt through the PFO, thereby causing oxygen desaturation.
In all, 17 patients (34%) experienced exercised-induced oxygen desaturation, and baseline demographics were not different between those with and without the condition. One-third of patients (34%) had an atrial septal aneurysm, 30% experienced migraine headaches, and 48% had suffered a TIA or stroke.
Closure Improves Saturation, Symptoms
Twenty-one patients underwent PFO closure; 13 who demonstrated exercise-induced oxygen desaturation and 8 who did not. The majority of the closure procedures were percutaneous (n = 19), while only 2 were surgical. In patients with oxygen desaturation and who were followed for 3 months after PFO closure (n = 10), the drop in oxygen saturation during exercise improved by an average of 10.1 ± 4.2% (12.6 ± 3% to 2.5 ± 1.6%; P < 0.001), and NYHA functional class improved by a median of 1.5 (interquartile range 0.75-2) from 3 (range 2-3) to 1 (range 1-2; P = 0.008).
Only 6 patients were referred for PFO evaluation, primarily due to arterial oxygen desaturation; 4 of these demonstrated the condition. Interestingly, 13 cases of provoked exercise desaturation were seen in patients with no history of the condition. After PFO closure, 5 patients demonstrated minor residual shunting on postprocedural echocardiography, but presence of residual shunt did not seem to impact the efficacy of PFO closure in ameliorating exercise-induced oxygen desaturation.
Dr. Krasuski and colleagues conclude that, “PFO closure leads to resolution of arterial oxygen desaturation and significant improvement in functional capacity in [provoked exercise desaturation] patients.”
Although one-third of patients in the general PFO population probably do not suffer from this condition, as opposed to patients in the study who were more likely to be symptomatic, “the greater implication . . . is that arterial desaturation through a PFO is a particularly challenging diagnosis that is likely underdiagnosed in the general population,” they write.
‘Crossing Our Fingers’
As such, the method of assessing arterial desaturation employed by the authors should become a routine part of assessing PFO patients, “particularly considering that there is no a priori way to determine which patients will desaturate,” they note.
In an accompanying editorial, Bernhard Meier, MD, of Bern University Hospital (Bern, Switzerland), suggests that “we look for a PFO in patients complaining about unexplained exertional dyspnea and to close it when present, crossing our fingers that the symptoms will improve.”
If they do not, the patient will still benefit from a lower risk of paradoxical embolism, Dr. Meier explains. The alternative, leaving the PFO open, “means missing the chance of symptom improvement and leaving the patient exposed to rare but serious risks for the rest of his or her life,” he writes.
However, when it comes to routinely testing symptomatic PFO patients for provoked exercise desaturation, Dr. Meier’s verdict is: “Probably not, as we usually have a more compelling indication at hand.”
Robert J. Sommer, MD, of Columbia University Medical Center (New York), agreed with that approach. “We shouldn’t be picking all PFO patients, but if patients are short of breath and have right to left shunting, doing pulse oximetry with exercise is easy,” he told TCTMD in a telephone interview, adding that this approach is probably not routine practice, “but it should be on people’s minds.”
Choosing the Right Patients
Dr. Sommer expressed surprise that so many patients demonstrated exercise-induced oxygen desaturation despite not showing symptoms. “What’s really impressive is [after PFO closure], NYHA class goes up substantially because they no longer get blue when they exert themselves,” he said. “It’s a cure.”
The findings, though, come in the midst of a turbulent period in the field after 2 trials found no benefit from PFO closure for migraine (MIST) or cryptogenic stroke (CLOSURE-1).
“The PFO thing has gotten so controversial,” Dr. Sommer acknowledged. “The importance of this paper is in demonstrating that we really need to continue to unbundle all of these PFO patients. They’re not all alike and we should stop trying to treat them all the same way. What’s incumbent on us as physicians in this current PFO era is to identify which groups need to be treated and which don’t.”
That is one reason why he does not recommend routine exercise testing for all PFO patients. “If a patient comes in with a stroke, do you do them any favors by exercising them, showing they desaturate, and then suggesting they close the hole as an alternative to just staying on medical therapy to prevent more strokes?” he said. “Those are 2 separate issues. Walking them up and down steps is an easy thing to do and it’s fine for patients who present with shortness of breath on exertion, but to try and use this as a rationalization for closing PFOs in patients with other symptoms is probably not appropriate.”
The average patient age was 46. Percutaneous PFO closure was accomplished using various devices:
2. Meier B. Some air for closure of the patent foramen ovale. J Am Coll Cardiol Intv. 2012;5:420-421.
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