Page 82 - Migraine, the heart and the brain

Chapter 4
Emboli that are larger or more solid (and probably less present), such as fat emboli, have not been recognized as a trigger, although studies are scarce.
Other explanations for a causal relation between right-to-left shunt and migraine with aura
A causal mechanism linking RLS with a migraine attack could also be hemodynamic. Generally, RLS are of no hemodynamic signi cance, but some PFOs have been associated with the platypnea – orthodeoxia syndrome. In this syndrome, the patient complains of dyspnea only while sitting or standing, accompanied by arterial desaturation [39]. Furthermore, resting hypoxemia related to (left-to-right) shunting across a PFO has been reported [40]. Mild arterial desaturation due to a RLS, therefore, should be considered as a possible mechanism linking RLS with migraine, as hypoxia is a known trigger of migraine [41].
Migraine treatment as a cause of right-to-left shunt?
Increased pulmonary vascular resistance is associated with PFO [42]. It was shown that sildena l decreased the RLS size, probably by decreasing pulmonary artery pressure [43]. The opposite occurs with 5HT1B agonists (e.g. triptans), which can cause pulmonary artery constriction [44]. The use of triptans, therefore, theoretically could enlarge or open a PFO by a transient increase of right-sided heart pressure. However, this does not explain that RLS prevalence is only increased in migraine with aura.
Are there proven beneficial effects of right-to-left shunt closure as prophylactic treatment of migraine?
Migraine patients have been referred to cardiologists for PFO closure, as migraine treatment [45]. Evidence for this therapy, however, is lacking, as the only randomized controlled study published so far is the Migraine Intervention with Starflex Technology (MIST) trial, which did not show an effect on the primary endpoint, cessation of migraine [10].
On the basis of (preliminary) ndings of the MIST study, Diener et al. [46] in this journal concluded that there was insuf cient evidence that PFO closure has a bene cial effect on migraine. Since then several observational (but no randomized) studies have been published [5 – 7,9]. Therefore, results from ongoing randomized PFO closure trials for migraine are eagerly awaited. Both the Stop pain, septal closure of PFO and the Escape trial (St. Jude, St. Paul, Minnesota, USA) have been terminated due to insuf cient enrollment or ethical concerns. The Premium (sham controlled,
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