Subclavian Artery Aneurysm - The Ballooning

Introduction:

Subclavian artery aneurysm is a rare condition affecting a population of less than one percent. An aneurysm is a weakening or bulging in the wall of a blood vessel. Subclavian aneurysm refers to the weakening/ballooning in the area of the subclavian artery that is located underneath the collarbone on both sides of the chest. When an area of the subclavian artery gets weakened, the pressure of the blood pumping through the artery causes abnormal bulging in the artery wall. If an aneurysm is left untreated, it can sometimes cause certain consequences to the patients. In this article, let's discuss in detail about causes, clinical presentation, and management options for subclavian artery aneurysms.

What Is the Subclavian Artery?

The subclavian artery supplies oxygen from the heart to the upper parts of the body. It also supplies a considerable part of the neck and brain through its branches. The subclavian artery is a paired blood vessel located at the roots of the neck supplying blood from the thorax to the head, neck, and upper limb. The scalenus anterior muscle (lateral muscle of the neck) crosses the subclavian artery anteriorly and divides the artery into three parts. The first part supplies to the chest and the brain, the second part supplies to the neck, and the third part supplies to the upper limb.

What Are the Causes of the Subclavian Artery Aneurysm?

Based on the anatomical location of the subclavian artery, the aneurysm of the artery occurs in the intrathoracic region or the extrathoracic region. Common causes of subclavian artery aneurysms are:

• Subclavian artery aneurysms (SAA) are often associated with people with smoking habits and hypertension.

• One of the most common causes of SAA is atherosclerosis (a fat build-up in the blood vessel walls causing narrowing and stiffening of the arteries blocking the blood flow).

• Other common causes include thoracic outlet syndrome, which is a group of disorders occurring as a result of compression to the blood vessels located in the middle of the collarbone and the first rib.

• Rarely occurs as a result of infection following intra-arterial drug injection.

• Marfan syndrome can cause SAA, and it is an inherited connective tissue disorder.

• Trauma or damage to the subclavian artery.

• Congenital condition.

• Iatrogenic causes (In hospital procedures).

What Are the Risk Factors for a Subclavian Artery Aneurysm?

Various factors can predispose to a subclavian artery aneurysm in people with the following conditions;

• People with a history of smoking habits.

• People who are diagnosed with diabetes.

• High cholesterol.

• Hypertensive patients (high blood pressure).

• Family history of atherosclerosis.

• People withcervical ribs (an additional rib above the first rib).

• People with elongated necks.

• Patients with dropped shoulders.

What Are the Clinical Presentations of SAA?

Initially, the subclavian artery aneurysm remains to be asymptomatic. Later on, the symptoms develop when the size of the bulging expands. The clinical presentation of subclavian artery aneurysm includes,

• 50 % of patients with SAA present with a pulsatile mass near the collarbone.

• Presence of non-specific chest pain.

• Shoulder pain might be present.

• Local compression of the trachea and esophagus might be present, which can result in difficulty breathing and difficulty swallowing, respectively.

• Compression can also result in brachial plexus compression causing damage to the peripheral nerves of the upper limb.

• Compression of the stellate ganglion (collection of nerve fibers) can induce Horner's syndrome (a neurological condition affecting the eye and surrounding structures of the eye).

• Compression in the laryngeal nerve results in an abnormal change in the quality of voice.

• SAA can sometimes cause the formation of blood clots in arteries resulting in a lack of blood flow to the upper arm.

• The blood clot formed sometimes might start traveling from the point of formation and might cause cerebral infarction leading to cerebrovascular accident.

How Is the Subclavian Artery Aneurysm Diagnosed?

The diagnosis of SAA depends on the symptoms of the patient and its localization.Aneurysms in the middle and distal part of the subclavian artery are normally diagnosed through detailed physical examination. Subclavian artery aneurysms in the proximal part of the artery are only diagnosed through radiographic imaging techniques.

• In cases of an intrathoracic aneurysm,achest X-ray is used as a major diagnostic tool that reveals the presence of an abnormal mass in the thoracic apex and shows the loss of normal borders between the thoracic structures.

• Contrast arteriographyis a highly sensitive imaging technique used in diagnosing the subclavian artery aneurysm. It involves using an X-ray and visualizing the inside while injecting a dye into the arteries.

• Magnetic resonance angiography and Computed tomography angiographymay be used as alternative diagnostic tools when the angiography is contraindicated.

• Currently, the investigation of choice is Duplex ultrasound scanning, and this technique uses high-frequency sound waves to assess the speed of blood inside the arteries.

How Is the SAA Treated?

The treatment options for subclavian artery aneurysms include conservative management, conventional surgical repair, and endovascular subclavian artery repair. Pre-operative computed tomography angiography and magnetic resonance angiography are compulsory for planning surgery. Open surgical repair is the definitive treatment modality in the surgical management of SAA.

Open surgical repair:

Approach: If the subclavian artery aneurysm is located in the intrathoracic region invasive approach is required along with surgical removal of the breast bone when the aneurysm is right-sided, and for the left-sided SAA, they are approached through a posterolateral thoracotomy procedure. Extra-thoracic subclavian aneurysms are approached through an incision above the clavicle (collarbone).

Procedure: It involves the surgical clipping of the aneurysm or excision with or without the reconstruction of the arterial wall. Recent reports show post-surgical pain in the arm due to reduced blood flow in the patient's arm, where arterial reconstruction was not performed. Arterial reconstruction involves anatomical reconstruction of the artery with interposition grafting. Rarely is there involvement of the aorta wall in which aorta and subclavian artery reconstruction with cardiopulmonary bypass are necessary.

Endovascular subclavian artery repair:

Even though open surgical repair is a commonly used treatment modality for SAA, nowadays, endovascular subclavian artery repair is increasingly performed. This is a minimally invasive technique involving the insertion of graft material into the aneurysm through small incisions. Radiographic imaging is used to guide the graft into its place.

Conclusion:

Aneurysm of the subclavian artery is an uncommon condition. In the initial stages, the condition is asymptomatic. If left untreated, it can lead to fatal complications. Diagnostic tools and treatment modalities are progressively increasing for this condition. The early diagnosis and proper utilization of various interventional techniques can show improvement in managing this challenging condition. Currently, the most preferred method of surgical option is endovascular subclavian artery repair.