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TABLE 11.2 Trials of PFO Closure for Treating Migraine Headaches.
Trial
Patient
Population
Treatment
Group
Control
Group Follow-up
Primary
Endpoint
Primary
Endpoint
Results
Additional Findings
(Secondary Endpoints,
post hoc Analysis)
MIST [25] PFO þ frequent
migraines
with aura
STARFlex
device
Sham procedure þ
medical therapy
6 months Complete
migraine
cessation
No significant
difference
Significant reduction in
headache days in
device group when
eliminating 2 outliers.
PRIMA
[34]
PFO þ frequent
migraines
with aura
Amplatzer PFO
Occluder
Medical therapy 12 months Reduction
of migraine
days
No significant
difference
PFO closure showed
improvement in
responder rate (50%
reduction in migraine
days), freedom from
migraine with aura,
reduction in migraine
with aura headache
days, and total
migraine attacks.
PFO closure showed
reduction in migraine
attacks among
migraineurs with frequent
aura.
PREMIUM
[35]
PFO þ frequent
migraines
with and
without aura
Amplatzer
PFO Occluder
Sham procedure þ
medical therapy
12 months 50%
reduction
in migraines
attacks
No significant
difference
PFO closure showed
significant reduction in
migraine with aura
attacks and headache
days per month, and
complete headache
cessation.
PFO closure showed
reduction in migraine
attacks among
migraineurs with frequent
aura.
MIST, Migraine Intervention with STARFlex Technology; PRIMA, Percutaneous Closure of PFO in Migraine with Aura; PREMIUM, Prospective, Randomized
Investigation to Evaluate Incidence of Headache Reduction in Subjects with Migraine and PFO Using the Amplatzer PFO Occluder to Medical Management.
FIGURE 11.1 Large PFO (marks) in the transesophageal echocardiogram of a 39-year-old nurse. The patient had suffered a stroke 2 years ago
with permanent aphasia. She had had frequent migraine with aura for over 20 years, and PFO closure cured her migraine. In retrospect, PFO
closure should have been performed before the stroke happened.
V. MIGRAINE AND PFO
META-ANALYSES OF THE TRIALS OF PFO CLOSURE FOR MIGRAINE HEADACHE 135
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CONCLUSIONS
Migraine is a prevalent and debilitating neurologic condition. Epidemiologic data suggest that migraine is often
underdiagnosed and undertreated [1e3]. At first glance, it may appear that the randomized controlled trials of PFO
closure for migraine headache are disappointing, as all 3 trials did not meet their primary endpoints. Given these
results, percutaneous PFO closure as a treatment for migraine is not supported in contemporary clinical guidelines,
let alone the search for PFO in migraine patients. The trials to date are hypothesis generating and have identified
both important areas for future research and insight into the mechanistic role of right-to-left shunting in migraine
headache.
Although individual trials did not meet their primary endpoints, there was a trend toward statistical significance,
along with multiple secondary endpoints that were met, indicating a potential benefit of PFO closure for a subset of
migraineurs. Another interesting observation was that when the PRIMA and PREMIUM trials were compared
(the 2 studies using the same Amplatzer device), the primary endpoint of one trial was a secondary endpoint of
the other and vice versa. The primary endpoint and a secondary endpoint of the PRIMA trial were a mean reduction
of migraine days and the responder rate, respectively, while the primary endpoint and a secondary endpoint of the
PREMIUM trial were the responder rate and mean reductionof migraine days, respectively. Had the 2 studies swapped
their primary endpoints, both trials would have met their primary endpoints and be considered positive studies [39].
A limitation of all trials was the inclusion criterion requiring failure of 2 or 3 preventive medications before
randomization. This led to a highly selective patient group that was included in the studies. Thus, the study
populations no longer correspond to an average migraine population, making it difficult to generalize the results.
Specifically, PRIMA and PREMIUM suggested a potential benefit of PFO closure, having a consistent effect on
migraine headaches; this was especially observed in the subgroup of mi graineurs with frequent aura (>50% of head-
ache episodes). The meta-analysis by Elbadawi et al. also showed that in subjects whose majority of migraine attacks
are with aura, there was a reduction in migraine attacks with PFO closure compared to the controls (standardized
mean difference ¼ 0.86; 95% CI: 0.07e1.65; P ¼ .03) [37].
The finding that a subset of migraineurs may benefit from PFO closure, the relative safety of the procedure, and
the high prevalence and significant societal impact of migraine headaches all highlight the importance of continued
research to identify the migraineurs who benefit from closure of their right-to-left shunts [40]. Investigating patients
who have migraine with frequent aura (>50% of the time in relation to their headaches) would be a good cohort to
investigate further. This also suggests that the International Headache Society classification may need revision to
include migraine with frequent aura as a separate entity [2]. The International Headache Society classification of
“migraine with aura” is defined by any patient who experiences 2 or more aura episodes in their lifetime. Since pa-
tients who had “migraine with frequent aura” (>50% of the time in relation to the migraine attacks) responded
significantly greater to PFO closure, this phenotype appears to be different than “migraine with rare/occasional
aura”. Future trials could focus on assessing PFO closure for migraineurs with frequent aura, as these patients
appear to benefit more from device closure. Moreover, the inclusion criteria could be liberalized to not require inef-
fective preventive medications before randomization, since the rare side effects of PFO closure need to be compared
also to the quite frequent side effects of long-term preventative migraine medications. The results of these trials and
TABLE 11.3 Summary of the Meta-analyses of PFO Closure for Treating Migraine Headaches.
Meta-analysis
Mean Migraine
Attacks/Month Mean Migraine Days/Month
Complete Cessation
of Migraine Attacks Subgroup Analysis
Kheiri
(2018) [37]
PFO closure showed
significant reduction
(mean difference: 0.54,
95% CI 0.63 to 0.45,
P < .01)
PFO closure showed
significant reduction
(mean difference: 1.33,
95% CI 2.32 to 0.33,
P < .01)
No difference
between PFO
closure and
controls (P ¼ .14)
N/A
Elbadawi
(2018) [38]
PFO closure showed
significant reduction
(SMD ¼ 0.25,
95% CI 0.06 to 0.43,
P ¼ .01)
PFO closure showed
significant reduction
(SMD ¼ 0.30,
95% CI 0.08 to 0.53,
P ¼ .01)
No difference
between PFO
closure
and controls
(P ¼ .14)
PFO closure showed reduction in
migraine attacks if majority of
migraine attacks occur with aura
(SMD ¼ 0.86, 95% CI 0.07 to 1.65,
P ¼ .03)
SMD, Standardized mean difference.
V. MIGRAINE AND PFO
11. RANDOMIZED CLINICAL TRIALS OF PFO CLOSURE FOR MIGRAINE HEADACHE (MIST, PRIMA, PREMIUM)136
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their meta-analyses suggest that such a study including only migraineurs who have frequent aura, with or preceding
their attacks, could yield a positive result.
In a recent retrospective study of 136 migraineurs with a PFO by Sommer et al. [41], patients were treated with thie-
nopyridine therapy (clopidogrel or prasugrel) and those whose headaches responded favorably underwent PFO
closure; thienopyridine therapy was discontinued 3 months after device closure. Ninety-four percent of these patients
experienced significant relief of their migraines even after medical therapy was discontinued. This study demon-
strated that successful P2Y12 platelet inhibition reduces headache symptoms in some migraineurs with PFO, suggest-
ing that the symptoms may have a platelet-based mechanism. It was thought that the near parallel response to PFO
closure may mechanistically link venous platelet activation with PFO-mediated right-to-left shunting. Similar results,
but less robust were observed with P2Y12 inhibition using ticagrelor [42]. Backed by these data, recruitment is ex-
pected to begin for a new clinical trial that will investigate the efficacy and safety of the Gore Cardioform Septal
Occluder (W.L. Gore and Associates; Flagstaff, Arizona) to treat migraine headache for 150 thienopyridine responders,
who would be randomized to PFO closure or a sham procedure followed by stopping medical therapy [43].
For years, the mainstay of preventativemigraine medical therapy has been medicationsthat were originallydesigned
to treatothersystemic disorders such as hypertension, seizures,anddepression.Recently, calcitonin gene-related peptide
(CGRP)blockers (targetingCGRPorits receptor)haveemerged as alternativemedications for the preventionof migraine
attacks [44]. Research suggests that CGRP is released during migraine episodes and this chemical may play a contrib-
utory role in migraine induction. Although the studies comparing CGRP blockers to placebo have shown promising
efficacious results in preventing migraine attacks, the long-term outcomes of these medications are currently unknown.
Additionally, CGRP receptors are also found in the normal vasculature and nervous system. Blocking these receptors
may have adverse neurovascular effects, especially in predisposed patients who already have cardiovascular or neuro-
logical diseases. Animal studies have shown that CGRP blockers may cause constipation, attenuate wound healing,
and affect pituitary hormone homeostasis, albeit there is no clear evidence of these observations in humans [44].
When PFO closure is considered for migraineurs, the risks and benefits of a one-time procedure should be weighed
against the risks, benefits and costs of chronic (and possibly lifelong) alternative medical therapies.
Finally, it needs to be kept in mind that the principal risk of a PFO resides in the possibility of paradoxical
embolism with stroke, myocardial infarction, or other systemic embolism. Several studies demonstrate an increased
risk of migraineurs, particularly those with aura, for such events, and some mention the PFO as a potential common
cause [45e51]. Since a right-to-left shunt occurs in 93% of cryptogenic stroke patients who have frequent migraine
with aura [52], and considering that migraine has also been linked to altered platelet function and increased venous
thromboembolism [49], a PFO may act as a conduit for the passage of blood clots or platelet plugs to cause most of
the strokes found in migraineurs with aura. However, this would be difficult to prove in a randomized trial given the
low absolute risk of stroke in migraine with aura patients. Thus, closing a PFO for migraine may entail a collateral
benefit, even for patients whose migraine does not respond favorably [53e55].
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CHAPTER
12
Hypoxemia and PFO
Dhruv Mahtta
1
, M. Khalid Mojadidi
2
, Anwar Tandar
3
,
Jonathan M. Tobis
4
, Bernhard Meier
5
1
Baylor College of Medicine, Houston, TX, United States;
2
Virginia Commonwealth University, Richmond, VA, United
States;
3
University of Utah, Salt Lake City, UT, United States;
4
University of California, Los Angeles, Los Angeles, CA,
United States;
5
University Hospital Bern, Bern, Switzerland
OUTLINE
Introduction 143
PFO and Hypoxemic Conditions 144
Pathophysiological Interplay Between PFO
and Hypoxemia 144
PFO and Obstructive Sleep Apnea 144
PFO and Chronic Obstructive Pulmonary Disease 146
PFO and Pulmonary Hypertension 146
Percutaneous PFO Closure for Other Chronic
Pulmonary Disorders 147
PFO and Platypnea-Orthodeoxia Syndrome 147
PFO and Pulmonary Arteriovenous Malformation
148
PFO and High-Altitude Pulmonary Edema
149
PFO and Exercise Desaturation
149
PFO and Left Ventricular Assist Device Implant
150
Society Guidelines on PFO Closure
151
Supplementary Materials
151
References
151
INTRODUCTION
During the embryonic period, the foramen ovale allows oxygenated blood from the maternal placenta to bypass
the unaerated lungs and directly enter the left atrium, thereby reaching the systemic fetal circulation. This right-to-
left shunt in the developing fetus is due to higher right atrial pressure from elevated pulmonary vascular resistance
in the unoxygenated fetal lungs [1]. Af ter birth, pulmonary vas cular resistance decreases, along with the pressure in
the right atrium, while a significant rise in left atrial pressure is seen. These changes result in closure of the septum
primum against the septum secundum with subsequent fusion (Fig. 12.1). However, in 20%e25% of individuals, the
foramen ovale fails to completely close and remains patent (Chapt er 1) [2e4]. Once thought to be rather benign, a
patent foramen ovale (PFO) has now been linked to multiple relevant pathologies. Although the association between
PFO and stroke has been well established (Chapters 4e7) [5,6], PFO-mediated hypoxemia remains clinically under-
recognized and undertreated.
143
PFO Closure for Stroke, Myocardial Infarction, Peripheral Embolism, Migraine, and Hypoxemia
Copyright © 2020 Elsevier Inc. All rights reserved.https://doi.org/10.1016/B978-0-12-816966-7.00012-9
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PFO AND HYPOXEMIC CONDITIONS
Pathophysiological Interplay Between PFO and Hypoxemia
In patients who have a PFO with no underlying pulmonary pathology, the left atrial pressure is 5e7mm Hg higher
than right atrial pressure. However, among patients suffering from pulmonary disorders such as pulmonary hyper-
tension, chronic obstructive pulmonary disease, obstructive sleep apnea, or obesity hypoventilation syndrome, intra-
thoracic pressure is often higher, resulting in right atrial pressure exceeding left atrial pressure [7,8]. This reversal of
the interatrial pressure gradient results in significant shunting of blood from the deoxygenated venous to the oxygen-
ated systemic circulation (Fig. 12.2A and B). The admixture of deoxygenated venous blood to oxygenated arterial
blood may result in profound hypoxemia. In patients with pulmonary conditions causing chronic hypoxemia due
to their primary lung pathology, a coexisting cardiac right-to-left shunt results in decreased arterial oxygenation
out of proportion to the underlying pulmonary disease. Distinguishing the relative contribution of hypoxemia due
to underlying pulmonary disease from a cardiac right-to-left shunt-induced arterial desaturation can be challenging.
PFO and Obstructive Sleep Apnea
The prevalence of obstructive sleep apnea (OSA) is estimated to be 10%e15% in adult females and 20%e30% in
adult males [9]. The mechanism for hypoxemia in OSA patients includes intermittent upper airway obstruction dur-
ing sleep caused by the receding tongue, resulting in disordered breathing (consisting of hypopneic and apneic ep-
isodes) and subsequent hypoxemia. Hypoxemia is also propagated by increased pulmonary arteriolar resistance,
pulmonary hypertension, and fluctuations in intrathoracic pressure during periods of forced breathing against an
obstructed upper airway [10]. Risk factors for OSA include male gender, diabetes, hypertension, and obesity. The
presence of OSA elevates the risk for cardiovascular and all-cause mortality [11,12]. Due to conflicting results of
several prior studies, the mechanistic association between PFO and OSA has been a subject of ongoing debate.
Normal
LA
LA
Septum secundum
Septum secundum
RA RA
Fossa ovalis
IVS IVS
PFO
Septum primum Septum primum
FIGURE 12.1 Patent foramen ovale. IVS, interventricular septum; LA, left atrium; RA, right atrium. Adapted with permission from Ref. [82].
(B)(A)
FIGURE 12.2 Transesophageal echocardiogram showing a PFO with resting bidirectional shunt. Color Doppler imaging confirms a left-to-
right shunt (A) and bubble study confirms right-to-left shunting (B). LA, left atrium;RA, right atrium.
12. HYPOXEMIA AND PFO144
VI. OTHER CONDITIONS AND PFO
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In an observational study of 72 patients (48 subjects with OSA and 24 controls), Shanoudy et al. [13] detected a
higher prevalence of PFO by transesophageal echocardiography (TEE) in patients with OSA compared to controls
(69% vs. 17%, P < .0001) [13]. Additionally, the authors also demonstrated that although baseline oxygen saturation
was similar in both groups, significant systemic hypoxemia occurred with Valsalva provocation among OSA pa-
tients who had a PFO compared to subjects without a PFO (Change in O2 saturation of 2.4% 1.5%
vs. 1.3% 0.6%; P ¼ .007). It is also noteworthy that one-third of patients had a >4 standard deviation decrease
in oxygen saturation.
The ratio between oxygen desaturation index (ODI) and apnea-hypopnea index (AHI) is a metric of the severity of
hypoxemia for the degree of OSA. Hypoxemia due to apneic episodes results in increased pulmonary arteriolar
resistance and a transient elevation in pulmonary artery pressure. In the presence of a PFO, the increased right-
sided pressure results in augmented right-to-left shunting and, thereby, worsening hypoxemia. Correlation between
patients with PFO resulting in right-to-left shunt and increased ODI/AHI ratio has also been well demonstrated by
several investigations [14,15]. In their study, Shaikh et al. [15] showed a higher prevalence of larger right-to-left
shunts (18% vs. 6%; P ¼ .049), with increased ODI/AHI in patients with a clinically significant shunt (1.05 vs.
0.86; P ¼ .004). In a larger study of 100 OSA patients and 200 control subjects, the authors demonstrated a 2.2 times
higher prevalence of right-to-left shunt in OSA patients as detected using a transcranial Doppler (TCD) bubble test
(42% vs. 19%; P < .001) [14]. The authors showed that patients with a right-to-left shunt had a higher ODI/AHI ratio
(P < .0001). OSA patients with PFO were younger and less frequently hypertensive. This led the authors to
hypothesize that with a similar level of obstructive airway dysfunction, patients with right-to-left shunt become
symptomatic at an earlier disease state due to more profound hypoxemia as compared to patients without a
right-to-left shunt.
Several mechanisms exist which result in increased right-to-left shunting across a PFO in patients with OSA.
Intermittent obstructive ventilation resulting in hypoxemia and hypercapnia predisposes patients to developing
pulmonary hypertension, which occurs in roughly 15%e20% of sleep apnea patients [9]. Recurrent hypoxemia
also results in reflex pulmonary vasoconstriction that can subsequently result in chronic pulmonary hypertension
by long-term modification of the pulmonary vasculature. Fluctuations in intrathoracic pressure occur as patients
breathe forcefully agains t an obstructed upper airway. This results in a negative pleural pressure which causes left-
ward bulging of the interatrial septum [16]. Lastly, apneic episodes result in sudden increases in pulmonary pres-
sures, which can lead to transient reversal of the interatrial pressure gradient, thereby increasing right-to-left
shunting across a PFO [17,18]. This was confirmed by a study that showed significant PFO-mediated shunting dur-
ing apneic episodes while no significant shunting was detected in OSA patients while they were awake [18].
Case reports have demonstrated cessation in right-to-left shunting with the use of continuous positive airway
pressure (CPAP) in OSA patients who have a PFO [19]. Pinet and Orehek showed that with the use of CPAP,
right-to-left shunting was terminated and could only be provoked with a Valsalva maneuver [19]. The use of
CPAP can mitigate the hemodynamic changes that occur in the pulmonary vasculature during recurrent apneic ep-
isodes in OSA patients with PFO, thereby leadi ng to cessation of right-to-left shunting [20]. Improvement in inter-
atrial shunting with the use of CPAP has also been attributed to beneficial changes in disordered breathing, apneic
episodes, and sudden increase in intrathoracic pressures.
Other case reports describe subjective and objective clinical improvement in patients with OSA after percuta-
neous PFO closure. In a case report, PFO closure was performed for secondary ischemic stroke prophylaxis; the pa-
tient demonstrated a significant improvement in OSA symptoms and a decrease in AHI was observed on
polysomnography [9]. The clinical improvement in this particular patient could not be explained by lifestyle, weight,
or medication adjustments. Additional case reports have shown improvement in fatigue, daytime lethargy, and ex-
ercise capacity after PFO closure [21]. These findings have been confirmed by an observational study by Rimoldi et
al. who investigated 40 patients with newly diagnosed OSA [10]. Among these patients, 14 (35%) were found to have
a PFO and all of them underwent successful PFO closure. Compared to controls, PFO closure demonstrated a sub-
stantial decrease in AHI (DAHI, 7.9 10.4 vs. þ4.7
13.1 events per hour, P ¼ .0009) and ODI (DODI, 7.6 16.6
vs. þ7.6 17.0 events per hour, P ¼ .01) indices for OSA patients who underwent device closure. A significantly
reduced number of patients were classified as having severe OSA after PFO closure (21% vs. 79%, P ¼ .007). Subjects
who underw ent device closure also experienced an improvement in cardiovascular parameters which included
brachial artery flow-mediated vasodilation, carotid artery stiffness, left ventricular diastolic function, nocturnal
blood pressure dipping, nocturnal systolic (7 mm Hg, P ¼ .009) and diastolic blood pressure (3 mm Hg,
P ¼ .04). The authors concluded that in patients with OSA and PFO, percutaneous device closure improves sleep-
disordered breathing and nocturnal oxygenation, which subsequently leads to improvement in endothelial function
VI. OTHER CONDITIONS AND PFO
PFO AND HYPOXEMIC CONDITIONS 145
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and vascular stiffening. On the contrary, the PFO Closure on Obstructive Sleep Apnea Syndrome (PCOSA) study
showed that the prevalence of PFO in OSA was similar to that in the general population [22]. The authors of this
study concluded that although PFO closure was safe, it did not improve OSA severity parameters on polysomnog-
raphy. It should be noted that this study used transthoracic echocardiography (TTE) with bubble study to detect a
PFO, which has inferior sensitivity and diagnostic accuracy comp ared to TEE and TCD (Chapter 2) [23e26]. Of the
143 OSA patients screened with a TTE bubble test, only 23 underwent PFO closure [22].
PFO and Chronic Obstructive Pulmonary Disease
The prevalence of PFO in patients with chronic obstructive pulmonary disease (COPD), and the potential
improvement in hypoxemia and patients’ functional capacity after PFO closure, have been a topic of multiple inves-
tigations. Based on observational studies, the approximate prevalence of PFO in COPD patients is estimated to be
45%e54% [10,27]. However, not all studies have demonstrated a statistically higher prevalence of PFO in patients
with COPD when compared to controls [28]. The reported prevalence has varied among different studies due to
the modality used to diagnose PFO (TTE vs. TCD) and the criteria used for a positive right-to-left shunt. TCD
may be limited in identifying a PFO due to its inability to differentiate between intracardiac and transpulmonary
shunts [29].
Soliman et al. demonstrated a doubling of the prevalence of PFO in patients with severe COPD versus controls
when diagnosed with TEE bubble study and Valsalva provocation [27]. It was noted that roughly half of these pa-
tients had transient arterial oxygen desaturation, the degree of which correlated with the severity of underlying pul-
monary hypertension secondary to COPD. Authors from another study confirmed the increased prevalence of PFO
in COPD patients compared to controls when a TTE bubble study was used to make the diagnosis [30]. Compared to
COPD patients without a PFO, those with a PFO were shown to have a lower arterial oxygen saturation, reduced 6-
minute walk test duration, and more severe disease course.
On the contrary, Martolini et al. showed that although the prevalence of PFO is higher in patients with COPD, the
functional limitations in terms of exercise capacity remained unchanged despite the presence of a right-to-left shunt
[31]. Twenty-two patients enrolled in the Global Initiative for Chronic Obstructive Lung Disease (GOLD) Stage II
COPD were included in this study. PFO was identified in 54% of patients (12 out of 22 patients) using TCD. As
compared to patients without a PFO, those with PFO did not have reduced exercise capacity or 6-minute walk
test duration. The authors concluded that the presence of PFO, although it resulted in right-to-left shunting, had
no implications in terms of functional capacity or limitations. However, the results of this study were criticized
due to the lack of control subje cts, small sample size, and absence of patients with large shunts.
PFO and Pulmonary Hypertension
In the setting of chronic pulmonary disorders, ventilation-perfusion mismatch may lead to hypoxia-induced
vasoconstriction and subsequent pulmonary hypertension [32,33]. Roughly 33% of all patients with COPD are noted
to have some degree of pulmonary hypertension [34,35]. Pulmonary hypertension has deleterious effects by result-
ing in an increase in right atrial pressure. This increase in right atrial pressure produces a reversal of the pressure
gradient between the left and right atrium, thereby promoting right-to-left shunting and exacerbation of hypoxemia
[36e39]. As a result, the presence of a PFO in patients with CO PD and associated pulmonary hypertension may
aggravate underlying hypoxemia and dyspnea. Several studies have shown that PFO-mediated right-to -left shunt-
ing can be decreased by using the same medications that decrease hypoxia-driven pulmonary vasoconstriction and
pulmonary hypertension. These medications include inhaled nitric oxide, supplemental oxygen, and phosphodies-
terase 5 inhibitors [14,40].
Nootens et al. evaluated the prevalence of PFO and its relation to 5-year survival, and exe rcise tolerance in pa-
tients with pulmonary hypertension; however, no significant differences were found as compared to the general
population [3]. It has long been hypothesized that in the setting of pulmonary hypertension, a right-to-left interatrial
shunt serves the purpose of a “pop off” valve that allows right atrial and ventricle pressure decompression. There-
fore, clinicians have questioned the safety of PFO closure in the setting of significant pulmonary hypertension, with
the concern of worsening the clinical condition due to a sudden increase in right-sided pressures following PFO
closure. Experimental studies in animal models by Austen et al. showed a benefit of right-to-left shunting via cre-
ation of atrial septostomy in dogs with right ventricular hypertension [41]. Some studies have sho wn clinical
improvement in patients with severe pulmonary hypertension after an iatrogenic right-to-left shunt was created
VI. OTHER CONDITIONS AND PFO
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