CORRESPONDENCE: LETTER TO THE EDITOR
Reply
Jonathan Tobis, MD* and
Babak Azarbal, MD
* Adult Cardiac Catheterization Laboratory, David Geffen School of Medicine, BL-394 CHS, University of California at Los Angeles, 10833 LeConte Avenue, Los Angeles, CA 90095-1717 (Email: Jtobis{at}mednet.ucla.edu).
The letter to the editor by Dr. Gupta raises some concerns, and it questions the validity of our hypothesis, which attempts to explain the observed connection between interatrial shunts and migraine headaches (1). It is appropriate to be skeptical of any new proposition, especially one that "rocks the boat" of currently accepted beliefs. We submit that there are enough independent observations of an association between patent foramen ovale (PFO) closure and significant reduction in migraine headache to allow this proposal a chance by performing a randomized clinical trial.
The clinical observation has been made that patients who have an interatrial communication 1) have an increased incidence of migraine headaches, and 2) closure of the interatrial communication results in significant improvement of the migraines. Although these studies are limited by their retrospective nature and a cohort that may not be reflective of the overall population of patients with migraine headache, the compelling findings of these studies have raised the possibility that closure of interatrial communications might provide a substantive treatment for migraine headaches.
Our hypothesis is that migraine headaches occur in people with a susceptible neuronal substrate. Several types of triggers might induce a migraine, but some of them may be chemically mediated, either through ingestion, or endogenously produced. Passing through the venous system, these chemicals are usually detoxified or perhaps just diluted in a first passage through the lungs. However, if a PFO or atrial septal defect (ASD) is present, then the intermittent right-to-left shunt that occurs with straining in either entity may permit these chemicals to enter the cerebral circulation in a high concentration and trigger the neurologic constellation that is recognized as a migraine headache. We agree with Dr. Gupta that emboli are unlikely to be the trigger of migraine headaches.
This hypothesis does not explain the mechanism of all migraine headaches. We do not understand why patients who have migraine with aura respond more frequently to PFO closure than do patients who have migraine without aura. These fascinating observations may open more avenues for research that might produce more successful therapeutic options for migraine sufferers than do current medical regimens.
With 12% of the population suffering from migraine headaches, we understand why the observations of reduction in migraine headaches following closure of interatrial shunts may generate interest and controversy. As with any new theory, the observations that support the theory come long before the randomized controlled trial that will test its validity. Our study supports the observations from other independent centers and provides a theoretical construct that "connects the dots" of rather disparate pieces of data. Let us turn the question around. How does one explain these independent observations of decreased headache following PFO closure? Placebo? This is unlikely when five independent centers all describe similar observations. Of the patients with migraine and aura, 75% had complete resolution of their headaches, with some patients followed up to three years. There is no drug or placebo that reports such a dramatic and long-lasting benefit to reduce migraine pain.
Finally, there are valid concerns with implanting a permanent device in someone's heart, especially when the indication is not life-threatening. We should use the observations of the studies as a starting point to generate a hypothesis and then perform a randomized clinical trial that will assess the potential benefits and risks of this technique. This is the classic scientific paradigm: if the current theory does not fit the data, then revise the theory; do not discount reproducible data. The strength and consistency of the observations are compelling enough to give this randomized clinical trial a chance.
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References
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- Azarbal B, Tobis J, Soh W, Chan V, Dao C, Gaster R. Association of interatrial shunts and migraine headachesimpact of transcatheter closure. J Am Coll Cardiol 2005;45:489-492.[Abstract/Free Full Text]
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