Atrial Septal Defect: Stroke Risk And Prevention

can atrial septal defect cause a stroke

Atrial septal defects (ASDs) are associated with an increased risk of cardioembolic strokes. Patients with cryptogenic strokes should undergo cardiac ultrasounds to check for ASDs. Two mechanisms can cause cardioembolic strokes in patients with ASDs: the first is a venous-based thrombus that passes through the ASD by right-to-left shunting, and the second is atrial fibrillation, which is more likely to develop in ageing patients with ASDs. The presence of an ASD or patent foramen ovale (PFO) is a risk factor for perioperative stroke, with patients diagnosed with ASD or PFO experiencing perioperative ischemic strokes more frequently than those without.

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Atrial septal defects and cardioembolic strokes

Atrial septal defects (ASDs) are associated with an increased risk of cardioembolic strokes. While the exact incidence is unknown, patients with ASDs, regardless of the size of the shunt, may present with a cardioembolic stroke. Cardioembolic strokes associated with ASDs occur through two mechanisms.

The first mechanism is a paradoxical embolism, where a venous-based thrombus passes through the ASD due to right-to-left shunting, resulting in a cardioembolic stroke. The second mechanism is atrial fibrillation, which can complicate the course of patients with ASDs, especially as they age.

The presence of an ASD or patent foramen ovale (PFO) has been identified as a risk factor for perioperative ischemic stroke in patients undergoing non-cardiac surgery. In a large-scale study, patients with an ASD or PFO had a significantly higher rate of perioperative ischemic stroke compared to those without (35.1% vs 6.0%). This association remained significant even after adjusting for various factors, including demographics and clinical covariates.

The increased risk of cardioembolic stroke in patients with ASDs or PFOs is attributed to the presence of a shunt between the left and right atria, allowing for paradoxical embolization. This risk is independent of the shunt size and is particularly relevant in patients younger than 55 years of age.

Prompt action is necessary to prevent stroke recurrence in patients with ASDs or PFOs. Secondary stroke prevention is crucial, and intervention with percutaneous or surgical closure of the shunt is recommended to reduce the risk of recurrent strokes. However, it is important to note that stroke risks are not completely eliminated with shunt closure.

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Atrial septal defect and the risk of ischemic stroke

Atrial septal defects (ASDs) are associated with an increased risk of ischemic stroke, particularly in patients with large and small shunts. The exact incidence of cardioembolic strokes in individuals with ASDs is unknown, but it is a recognised complication. Patients with cryptogenic strokes should be assessed for the presence of an ASD.

Mechanisms of Ischemic Stroke in Atrial Septal Defects

There are two primary mechanisms by which cardioembolic strokes occur in individuals with ASDs:

  • Paradoxic embolism: This involves a venous-based source of thrombus, which passes through the ASD via right-to-left shunting, resulting in a cardioembolic stroke.
  • Atrial fibrillation: This is a common complication in patients with ASDs, particularly as they age, and can increase the risk of ischemic stroke.

Clinical Evidence

A study by Nathaniel R. Smilowitz et al. found that in a large, nationwide cohort of patients hospitalized in the United States, those with ASDs or patent foramen ovale (PFO) had a significantly higher risk of perioperative acute ischemic stroke after non-cardiac surgery compared to those without ASDs or PFO (35.1% vs. 6.0%, p<0.001). This association persisted even after adjusting for demographic and clinical factors, suggesting that ASDs are an independent risk factor for ischemic stroke.

Additionally, a case report by Rakan I. Nazer described a young female patient with a recurrent cryptogenic stroke who was found to have a small fenestrated ASD. The report highlights the potential advantages of direct surgical closure in detecting and removing the source of embolization in patients with recurrent cryptogenic strokes.

ASDs are associated with an increased risk of ischemic stroke, particularly in the presence of other risk factors or during perioperative periods. Prompt action is necessary to prevent stroke recurrence, including consideration of surgical or device closure of the ASD. Further research is needed to fully understand the incidence and mechanisms of ischemic stroke in individuals with ASDs.

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Inter-atrial shunts and cryptogenic stroke

Inter-atrial shunts, such as patent foramen ovale (PFO) and atrial septal defects (ASD), are associated with an increased risk of cryptogenic stroke. Cryptogenic stroke is a type of stroke with no clear source of embolisation or thrombosis, accounting for 30-40% of all ischemic strokes.

Having an inter-atrial shunt increases the risk of cryptogenic stroke, with studies showing that 40% of patients with cryptogenic stroke will have some form of inter-atrial shunting. The risk of stroke seems independent of the shunt size. In patients with inter-atrial shunts, cardioembolic strokes can occur via two mechanisms:

  • Paradoxic embolism: A venous-based clot travels through the shunt, causing a cardioembolic stroke.
  • Atrial fibrillation: This can complicate the course of patients with ASDs, especially as they age, and lead to cryptogenic stroke.

The presence of an inter-atrial shunt can be detected by cardiac ultrasound, and prompt action is required to prevent stroke recurrence. Surgical or device closure of the shunt can be performed to reduce the risk of recurrent strokes. However, this does not eliminate stroke risks, as it is difficult to estimate how much of the stroke burden is attributed solely to the shunt.

In addition to shunt closure, anticoagulation therapy may also be considered for secondary stroke prevention in patients with atrial cardiopathy and cryptogenic stroke. Clinical trials are currently underway to test the effectiveness of anticoagulation therapy in this patient population.

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Atrial septal defects and atrial fibrillation

Atrial septal defects (ASDs) are a common congenital heart defect, accounting for 6-10% of all congenital heart defects. ASDs are associated with an increased risk of atrial fibrillation (AF), a common complication in patients with ASDs. The link between AF and ASD is complex and involves modifications in electrophysiologic, contractile, and structural properties at the cellular and tissue level of both atria, mainly due to chronic atrial stretch and dilation.

ASDs are characterised by a left-to-right shunt, resulting in right atrial enlargement, right ventricular dilation, and, to a lesser extent, left atrial enlargement. This chronic volume stress leads to electrical remodelling, altering atrial myocyte electrophysiologic properties and increasing intra-atrial conduction time. This electrical remodelling predisposes patients with ASDs to AF and other atrial tachyarrhythmias.

The risk factors for AF in patients with ASDs include older age at the time of repair, larger shunt size, pulmonary hypertension, and other comorbidities. The prevalence of AF is decreased after ASD closure but remains elevated compared to the general population, especially in older patients or those with larger shunts.

In addition to AF, other forms of supraventricular tachycardia (SVT) are also commonly seen in patients with ASDs, including atrioventricular reciprocating tachycardia (AVRT) and atrioventricular node reentrant tachycardia (AVNRT). These arrhythmias can be treated medically or with transcatheter ablation, with consideration given to the timing and type of ASD closure.

Conduction disorders are rare in patients with ASDs. However, sinus node dysfunction may be seen, especially in patients with sinus venosus ASDs or with late age of repair and large shunt size. Additionally, ostium primum ASDs have a higher risk of spontaneous or post-operative atrioventricular (AV) block, although this is rare with modern surgical techniques.

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Atrial septal defect closure

Atrial septal defect (ASD) closure is a procedure to treat atrial septal defects, which are holes in the heart's septum. ASD closure can be performed either through transcatheter closure or surgical repair. Transcatheter closure is a less invasive procedure where a catheter is inserted into a vein in the groin and guided to the heart to place a closure device. Surgical repair, on the other hand, involves open-heart surgery to access and close the defect.

Transcatheter closure has become an accepted alternative to surgical repair for ostium secundum atrial septal defects, which are the most common type of ASD. It is commonly offered as the first-intention treatment and is safe and effective in at least 80% of cases. However, large ASDs (>38 mm) and defects with deficient rims are usually referred for surgical closure. Transcatheter closure may also be controversial for complicated ASDs with comorbidities, additional cardiac features, and in small children.

During the procedure, the patient is placed under anaesthesia, and a cardiologist performs a transoesophageal echocardiogram (TEE) to guide the surgeon. The surgeon then makes an incision in the breastbone to reach the heart and places the patient on a cardiopulmonary bypass machine, which pumps blood to the body while the heart is temporarily stopped. An incision is made in the heart's right atrium to access the defect, and a patch is stitched onto the hole to close it. The heart is then closed with sutures, and the cardiopulmonary bypass machine is removed.

ASD closure surgery carries certain risks, such as bleeding, infection, or adverse reactions to anaesthesia. Patients should not eat after midnight on the night before the surgery. Before the procedure, patients meet with the surgeon and anesthesiologist to review their medical history and receive specific instructions. After the surgery, patients are monitored in the intensive care unit, and pain medication is administered as needed. The length of the hospital stay depends on the patient's recovery progress and their ability to perform physical activity.

Frequently asked questions

Yes, atrial septal defects (ASDs) can cause cardioembolic strokes. Patients with cryptogenic strokes should have a cardiac ultrasound to check for an ASD.

There are two mechanisms by which an ASD can cause a cardioembolic stroke. The first is a paradoxical embolism, where a venous-based thrombus passes through the ASD by right-to-left shunting. The second is atrial fibrillation, which can complicate the course of patients with ASDs, especially as they age.

The exact incidence of stroke in patients with ASDs is unknown. However, in a large nationwide analysis of patients undergoing non-cardiac surgery, a diagnosis of ASD was associated with a significantly increased risk of acute ischemic stroke.

Treatment options for ASD include surgical or device closure. Prompt action is required to prevent stroke recurrence.

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