Are patients with a patent foramen ovale at increased risk of stroke? A billion dollar question

Which Patent Foramen Ovales Need Closure to Prevent Cryptogenic Strokes?

Patients with cryptogenic strokes are more likely to have a patent foremen ovale than in the general population. It is speculated that these strokes are due to paradoxical embolism, that is, passage of a venous thrombus across the patent foremen ovale to enter the arterial circulation, resulting in an embolic stroke. Venous thromboembolism is rarely present in these cases of cryptogenic stroke. Thousands of patients with cryptogenic strokes have undergone transcatheter closure of their patent foremen ovale via a variety of devices. The first 3 randomized clinical trials comparing patent foremen ovale closure with medical therapy failed to show a significant advantage of patent foremen ovale closure. Three additional trials reported in 2017 had longer years of follow-up and demonstrated an advantage of patent foremen ovale closure versus medical therapy. Analysis of their data indicated that patent foremen ovale closure in patients with an atrial septal aneurysm in addition to a patent foremen ovale had a very significant decrease in cryptogenic strokes (P < .001). There was no decrease in strokes in patients without an aneurysm of the atrial septum who underwent patent foremen ovale closure (P = .37). Aneurysms of the atrial septum are easily recognized by echocardiography and are present in approximately one-third of patients with patent foremen ovales. These data suggest that closure of patent foremen ovales in patients with an atrial septal aneurysm is indicated. In patients with a patent foremen ovale without an aneurysm of the atrial septum, patent foremen ovale closure is not indicated.

Silent Atrial Fibrillation and Cryptogenic Strokes

A new suspected cause of cryptic strokes is "silent atrial fibrillation." Pacemakers and other implanted devices allow continuous recording of cardiac rhythm for months or years. They have discovered that short periods of atrial fibrillation lasting minutes or hours are frequent and usually are asymptomatic. A meta-analysis of 50 studies involving more than 10,000 patients with a recent stroke found that 7.7% had new atrial fibrillation on their admitting electrocardiogram. In 3 weeks during and after hospitalization, another 16.9% were diagnosed. A total of 23.7% of these stroke patients had silent atrial fibrillation; that is, atrial fibrillation diagnosed after hospital admission. Silent atrial fibrillation is also frequent in patients with pacemakers who do not have a recent stroke. In a pooled analysis of 3 studies involving more than 10,000 patients monitored for 24 months, 43% had at least 1 day with atrial fibrillation lasting more than 5 minutes. Ten percent had atrial fibrillation lasting at least 12 hours. Despite the frequency of silent atrial fibrillation in these patients with multiple risk factors for stroke, the annual incidence of stroke was only 0.23%. When silent atrial fibrillation is detected in patients with recent cryptogenic stroke, anticoagulation is indicated. In patients without stroke, silent atrial fibrillation should lead to further monitoring for clinical atrial fibrillation rather than immediate anticoagulation, as some have advocated.

Cryptogenic Strokes and Patent Foramen Ovales: What's the Right Treatment?

More than 25% of all ischemic strokes per year are cryptogenic, that is, their cause is not determined after an appropriate evaluation. In 1988, it was reported that the incidence of a patent foramen ovale was 30 to 40% in young patients with a cryptogenic stroke compared with 25% in the general population. This led to the suspicion that cryptogenic strokes were due to paradoxical embolism, that is, a venous thrombus crossing a patent foramen ovale to enter the left atrium and then the arterial circulation. Few of the patients considered to have paradoxical embolism were shown to have coexistent venous thromboembolism. This suspicion of paradoxical embolism led to thousands of patients undergoing surgical closure of their patent foramen ovale. Surgical closure was replaced by closure of the patent foramen ovale by a variety of transvenous devices. Others recommended anticoagulant or antiplatelet therapy to prevent recurrent ischemic strokes. Three randomized clinical trials totaling more than 2000 patients compared closure of the patent foramen ovale with medical therapy. All 3 trials reported that closure of the patent foramen ovale provided no benefit compared with medical therapy. Subsequent trials have demonstrated no benefit of anticoagulation compared with antiplatelet therapy in patients with cryptogenic strokes with or without a patent foramen ovale. Patients with cryptogenic strokes should be evaluated for the presence of venous thromboembolism. If venous thromboembolism is present, treatment should be the same as for pulmonary embolism: anticoagulation. If venous thromboembolism is not present, antiplatelet therapy is indicated.

Transcatheter closure of PFO as secondary prevention of cryptogenic stroke

This article covers the main unsolved issues regarding the potential role that the patent foramen ovale (PFO) plays in the genesis of so-called cryptogenic stroke. Some brief notions of the anatomy and epidemiology of the PFO are outlined. Subsequently, the results of the three trials on secondary prevention (medical therapy vs. transcatheter closure) in patients with PFO and a history of cryptogenic stroke are presented. The conflicting results of numerous meta-analyses derived from the three randomized controlled trials are discussed. Official scientific guidelines dispute an alleged superior efficacy of transcatheter PFO occlusion in comparison with antithrombotic therapy alone (anticoagulants or antiplatelet agents), except for selected cases of patients with documented PFO and a concomitant clinical-instrumental picture of deep venous thrombosis. Nevertheless, considering recent doubts about the presumptive thrombogenic and arrhythmogenic potential of PFO occlusion, which concerns only one of the septal occluders previously used, further in-depth investigations are warranted, centered on the use of newer dedicated devices to be tested in comparison with antithrombotic regimens alone.

Unresolved or Contradictory Issues About Management of Patients With Patent Foramen Ovale and Previous Cryptogenic Stroke: Additional Randomized Controlled Trials Are Eagerly Awaited

Stating a well-codified and widely accepted therapeutic conduct for patients with patent foramen ovale (PFO) and previous cryptogenic stroke is made difficult and somewhat controversial by several issues remained unresolved so far. In this short review, some aspects of the possible role played by the PFO in the pathogenesis of cryptogenic stroke are succinctly analyzed. First, some aspects of cardiovascular anatomy of the human fetus and the adult are outlined. Subsequently, the three randomized controlled trials (RCTs) that have been accomplished so far to compare the implant of a transeptal occluding device with a simple medical therapy in patients with PFO and history of cryptogenic stroke are briefly examined. These RCTs, when assessed using the “intention to treat” method, do not show a greater protective effect of therapy with transeptal device as regards the recurrences of stroke. Afterwards, there is a brief presentation of the findings of several meta-analyses that have been derived from the three above mentioned RCTs, whose results are strikingly discordant with each other. In fact, some of them come to the conclusion that the transcatheter closure of PFO does not offer significant advantages compared to antithrombotic therapy for the secondary prevention of cryptogenic stroke, while others based on subgroup analyses argue that the transcatheter closure of PFO with Amplatzer device, differently from the one performed using the STARFlex device, would be associated with significantly lower incidence of cerebrovascular events compared with medical therapy alone. Finally, the authors argue the need to adhere to the current scientific guidelines. They substantially deny an alleged superior efficacy of transcatheter PFO occlusion compared to medical therapy with antithrombotic agents (anticoagulants or antiplatelet agents), except for selected cases of patients with documented PFO and concomitant clinical-instrumental picture of deep venous thrombosis.

Closure or medical therapy for cryptogenic stroke with patent foramen ovale

BACKGROUND

The prevalence of patent foramen ovale among patients with cryptogenic stroke is higher than that in the general population. Closure with a percutaneous device is often recommended in such patients, but it is not known whether this intervention reduces the risk of recurrent stroke.

METHODS

We conducted a multicenter, randomized, open-label trial of closure with a percutaneous device, as compared with medical therapy alone, in patients between 18 and 60 years of age who presented with a cryptogenic stroke or transient ischemic attack (TIA) and had a patent foramen ovale. The primary end point was a composite of stroke or transient ischemic attack during 2 years of follow-up, death from any cause during the first 30 days, or death from neurologic causes between 31 days and 2 years.

RESULTS

A total of 909 patients were enrolled in the trial. The cumulative incidence (Kaplan-Meier estimate) of the primary end point was 5.5% in the closure group (447 patients) as compared with 6.8% in the medical-therapy group (462 patients) (adjusted hazard ratio, 0.78; 95% confidence interval, 0.45 to 1.35; P=0.37). The respective rates were 2.9% and 3.1% for stroke (P=0.79) and 3.1% and 4.1% for TIA (P=0.44). No deaths occurred by 30 days in either group, and there were no deaths from neurologic causes during the 2-year follow-up period. A cause other than paradoxical embolism was usually apparent in patients with recurrent neurologic events.

CONCLUSIONS

In patients with cryptogenic stroke or TIA who had a patent foramen ovale, closure with a device did not offer a greater benefit than medical therapy alone for the prevention of recurrent stroke or TIA. (Funded by NMT Medical; ClinicalTrials.gov number, NCT00201461.).

Percutaneous device closure of patent foramen ovale for secondary stroke prevention: a call for completion of randomized clinical trials. A science advisory from the American Heart Association/American Stroke Association and the American College of Cardiology Foundation

The optimal therapy for prevention of recurrent stroke or transient ischemic attack in patients with cryptogenic stroke and patent foramen ovale has not been defined. Although numerous observational studies have suggested a strong association between patent foramen ovale and cryptogenic stroke, a causal relationship has not been convincingly established for the majority of affected patients. Treatment choices include medical therapy with antiplatelet agents or vitamin K antagonists, percutaneous device closure, or open surgical repair. Whereas suture closure of an incidental patent foramen ovale is performed routinely during the course of an operation undertaken for another indication, primary surgical repair is rarely advocated in the current era. The choice between medical therapy and percutaneous device closure has been the subject of intense debate over the past several years, albeit one that has not been adequately informed by randomized, prospective clinical trial data to permit an objective comparison of the relative safety and efficacy of these respective approaches. Enrollment in clinical trials has lagged considerably despite frequent calls for participation from the US Food and Drug Administration and major professional societies. Completion and peer review of ongoing trials are critical steps to establish an evidence base from which clinicians can make informed decisions regarding the best therapy for individual patients. The present advisory strongly encourages all clinicians involved in the care of appropriate patients with cryptogenic stroke and patent foramen ovale--cardiologists, neurologists, internists, radiologists, and surgeons--to consider referral for enrollment in these landmark trials to expedite their completion and help resolve the uncertainty regarding optimal care for this condition.

Prevalence of atrial septal abnormalities in older patients with cryptogenic ischemic stroke or transient ischemic attack

OBJECTIVE

To evaluate the association of atrial septal abnormalities--patent foramen ovale (PFO), atrial septal aneurysm (ASA), or the combination of both (PFO+ASA)--with cryptogenic stroke or transient ischemic attack (TIA) in older patients.

METHODS

We examined the prevalences of PFO, ASA, and PFO+ASA in 132 consecutive patients aged 55 years or more who underwent transesophageal echocardiography (TEE) for evaluation of ischemic stroke or TIA. We compared patients with cryptogenic stroke/TIA and those with stroke/TIA of known cause.

RESULTS

PFO+ASA was more common in patients with cryptogenic stroke/TIA than in patients with stroke/TIA of known cause (12/62 or 19% vs. 2/70 or 3%; adjusted odds ratio, 7.4; 95% CI, 1.4-38.2). Differences between groups for isolated PFO, and isolated ASA were not significant. The association of PFO+ASA with cryptogenic stroke/TIA was confirmed in the subgroup of patients aged 75 years or more (odds ratio, 15.0; 95% CI, 1.5-146.7).

CONCLUSION

This study indicates a significant association of PFO+ASA with cryptogenic stroke or TIA in older patients.

Leptin receptor action and mechanisms of leptin resistance

The adipose tissue-derived hormone leptin regulates energy balance and neuroendocrine function. Resistance to the appetite-suppressing effects of leptin is associated with common forms of obesity. Here, we review the mechanisms by which leptin activates intracellular signals and the roles that these signals play in leptin action in vivo. Furthermore, we discuss potential mechanisms of leptin resistance, specifically focusing on data regarding the neuroanatomical locus of leptin resistance and potential mechanisms by which expression of the suppressor of cytokine signaling-3 may impair leptin action.