An aberrant left subclavian artery is a congenital variation in which the left subclavian artery originates from an unusual spot on the aorta, almost always in the context of a right-sided aortic arch. Instead of branching off as one of the first vessels from the arch, the artery arises as the last branch, looping behind the esophagus and trachea to reach the left arm. Most people who have it never experience symptoms, but the anatomy can compress nearby structures or develop a dangerous outpouching called a Kommerell’s diverticulum, and the condition has a well-documented genetic link that makes it more than a simple anatomical curiosity.
What Normal Looks Like and Where This Goes Wrong
In a typical chest, the aortic arch curves to the left, sending off branches in a predictable order: the brachiocephalic trunk (which splits into the right subclavian and right common carotid arteries), the left common carotid artery, and then the left subclavian artery. When the arch instead curves to the right, a mirror-image pattern usually develops. But in some people with a right aortic arch, the left subclavian artery does not arise from a mirrored brachiocephalic trunk on the left side. Instead, it springs from the very end of the arch or even the top of the descending aorta, coursing behind the esophagus to get to the left arm. That retroesophageal path is what defines the anomaly and what creates the potential for trouble.
A right aortic arch itself is uncommon, appearing in roughly 0.05–0.1% of the general population. Among people who do have a right arch, though, an aberrant left subclavian artery is one of the most frequent branching variants. When you flip the scenario to a left-sided arch, the equivalent anomaly is an aberrant right subclavian artery, which is far more common overall because the left arch is the normal configuration. But as one systematic review noted, among individuals with a right arch, the proportion who also have an aberrant left subclavian artery is actually higher than the proportion of left-arch individuals with an aberrant right subclavian artery.1International Journal of Cardiology. Left aberrant subclavian artery. Systematic study in adult patients So although the absolute numbers are small, it is a disproportionately common finding once a right arch is present.
Why Most People Never Know They Have It
The majority of people with an aberrant left subclavian artery are completely asymptomatic. The vessel finds its path behind the esophagus early in fetal development, and the body accommodates it. Many cases turn up incidentally when imaging is done for an unrelated reason, such as a chest CT for a lung nodule or an echocardiogram for a heart murmur. In a large series of patients with Kommerell’s diverticulum (a related finding discussed below), about 41% were asymptomatic at the time of diagnosis.2The Annals of Thoracic Surgery. Kommerell Diverticulum: Distinctions Between Arch Side and Evaluation of Morphology, Size, And Risk That figure likely underestimates the true proportion of asymptomatic carriers in the general population, because the study only captured patients whose anatomy was already flagged on imaging.
In a series of 152 patients with aberrant subclavian arteries, 87 did not require surgery at all.3Operative Techniques in Thoracic and Cardiovascular Surgery. Repair of Kommerell’s Diverticulum and Aberrant Subclavian Arteries: Classification of the Five Groups in Declining Frequency and Their Operative Approaches For many of those patients, careful monitoring was all that was needed.
When Symptoms Do Appear
Symptoms from an aberrant left subclavian artery come from the vessel pressing on the esophagus, the trachea, or both. The classic swallowing difficulty caused by a retroesophageal artery has its own name: dysphagia lusoria, a term that has been in medical use since the 18th century. Roughly 30–40% of people with vascular anomalies of the aortic arch branching pattern eventually develop some degree of swallowing or breathing symptoms.4PubMed Central. Dysphagia lusoria: a late onset presentation
The timing of symptom onset varies widely. In children, the problem tends to show up as airway symptoms rather than swallowing trouble: wheezing, stridor (a high-pitched breathing sound), chronic cough, and recurrent pneumonia. One pediatric surgical series found that all 18 children who underwent repair were symptomatic beforehand, with airway complaints dominating and feeding difficulties present in a smaller subset.5The Annals of Thoracic Surgery. Primary Translocation of Aberrant Left Subclavian Artery for Children With Symptomatic Vascular Ring In adults, swallowing difficulty becomes more prominent. Age-related changes in the esophagus and the gradual stiffening of the aberrant vessel itself can turn a lifelong anatomical quirk into a functional problem decades later.6PubMed Central. Dysphagia lusoria: a late onset presentation
One reason for the late-onset pattern is that the esophagus is fairly compliant in youth. It can accommodate a crossing artery without much fuss. As the artery wall stiffens with age and atherosclerosis develops, the compression worsens. Meanwhile, the esophageal muscles themselves weaken, making even modest compression more disruptive to swallowing.
Kommerell’s Diverticulum and Why It Matters
At the point where the aberrant artery leaves the aorta, a bulge in the aortic wall often forms. This outpouching is called a Kommerell’s diverticulum, named after the radiologist who described it in 1936. It represents a remnant of the embryonic arch segment that normally disappears during development. The diverticulum can be small and harmless, or it can grow large enough to compress the trachea and esophagus on its own and, more ominously, to carry a real risk of rupture.
In a study comparing patients with right aortic arch and aberrant left subclavian artery to those with the mirror anomaly (left arch with aberrant right subclavian artery), the right-arch group had larger diverticula relative to the size of their descending aorta and were more symptomatic, with 75% reporting symptoms compared to 28% in the left-arch group. The right-arch patients were also younger at presentation, with a median age of about 9.5 years versus nearly 62 years for the left-arch group.7The Annals of Thoracic Surgery. Kommerell Diverticulum: Distinctions Between Arch Side and Evaluation of Morphology, Size, And Risk This difference matters because it means a right aortic arch with an aberrant left subclavian artery tends to be a more consequential finding than the reverse scenario.
Intervention on a Kommerell’s diverticulum is typically recommended when its opening exceeds about 3 cm in diameter and its depth exceeds 5 cm, thresholds beyond which rupture risk rises meaningfully.8PubMed Central. Kommerell’s Diverticulum Masquerading in a Right Aortic Arch: A Vascular Surprise Case reports document diverticula reaching impressive sizes; one patient presented with a diverticulum measuring 58 by 41 mm along with displacement of both the trachea and the esophagus.9Vascular and Endovascular Surgery. Kommerell’s Diverticulum in a Right-Sided Aortic Arch With an Aberrant Left Subclavian Artery Hybrid Repair An aneurysm of an aberrant subclavian artery is itself reported with a prevalence of about 2% among aortic arch anomalies.10Europe PMC / Journal of Visualized Surgery. Aberrant subclavian: new face of an old disease
The 22q11.2 Deletion Connection
An aberrant left subclavian artery is not just a random plumbing error. It has a well-established genetic association with chromosome 22q11.2 deletion syndrome, a condition known by several older names including DiGeorge syndrome and velocardiofacial syndrome. This microdeletion on chromosome 22 disrupts the development of the pharyngeal arches, structures in the embryo that give rise to much of the face, heart, and great vessels.
In a study of patients with isolated anomalies of aortic arch laterality and branching, chromosome 22q11 deletions were found in 24% of cases.11PubMed. Association of chromosome 22q11 deletion with isolated anomalies of aortic arch laterality and branching That is a strikingly high rate for a genetic deletion that affects roughly 1 in 4,000 live births in the general population, and it means that finding a right aortic arch with an aberrant left subclavian artery should prompt consideration of genetic testing, particularly in children. One case report highlighted a neonate whose refractory stridor, wheezing, and vomiting led to the discovery of a right aortic arch with an aberrant left subclavian artery and Kommerell’s diverticulum, and subsequent genetic testing confirmed a 22q11.2 deletion.12PubMed. Congenital stridor and wheezing as harbingers of the del22q11.2 syndrome presenting cardiovascular malformations of right aortic arch, aberrant left subclavian artery, Kommerell’s diverticulum, and left ligamentum arteriosum
The broader phenotype of 22q11.2 deletion syndrome can include immune deficiency, low calcium from underdeveloped parathyroid glands, palate abnormalities, learning difficulties, and a wide range of congenital heart defects beyond the aortic arch variant.13PubMed Central. An Adult Case of Chromosome 22q11.2 Deletion Syndrome Associated with a High-positioned Right Aortic Arch Not every person with an aberrant left subclavian artery carries this deletion, but the overlap is frequent enough that the vascular finding is considered a red flag warranting genetic evaluation.
How It Gets Diagnosed
Before cross-sectional imaging existed, many of these anomalies were found either at autopsy or during catheter-based angiography. Today, CT angiography and MR angiography are the standard first-line tools for evaluating thoracic vascular anomalies. CT angiography is particularly valuable because it shows the vessel itself, the surrounding airways, the esophagus, and any associated diverticulum or aneurysm in a single scan. Compared with older catheter angiography, CT angiography is better at visualizing the relationship between the aberrant vessel and adjacent structures and is far less invasive.14PubMed. Multidetector computed tomographic angiography of aberrant subclavian arteries
Prenatal diagnosis is possible as well. When fetal echocardiography raises suspicion of an abnormal arch, the diagnosis can be confirmed after delivery with echocardiography and CT angiography.15PubMed. Right aortic arch with aberrant left subclavian artery–prenatal diagnosis and evaluation of postnatal outcomes: report of three cases Prenatal detection is useful because it allows the medical team to plan for potential airway or feeding issues early and to arrange genetic testing promptly after birth.
The Blood Pressure Clue
An underappreciated consequence of an aberrant left subclavian artery is a difference in blood pressure readings between the two arms. Because the aberrant vessel follows a longer, more tortuous path from the aorta to the left arm, and because it can develop narrowing or even hypoplasia at its origin, blood flow to the left arm may be reduced. One case report described a 30-year-old man whose only finding was a persistent inter-arm blood pressure difference of 15–20 mmHg, with the left arm reading lower. Doppler ultrasound showed left subclavian artery occlusion with retrograde flow in the left vertebral artery, a phenomenon called subclavian steal. CT confirmed a right aortic arch with a severely hypoplastic aberrant left subclavian artery.16PubMed. Aberrant Left Subclavian Artery Hypoplasia with Right Aortic Arch as a Cause of Inter-arm Blood Pressure Difference and Subclavian Steal in an Asymptomatic Adult
For the average person, a blood pressure difference of more than 10 mmHg between arms is usually a prompt to investigate peripheral vascular disease or aortic problems. In someone with an undiagnosed aberrant left subclavian artery, this finding has a straightforward anatomical explanation but can be easily mistaken for atherosclerotic disease. It also has practical implications: if a clinician always measures blood pressure on the left arm, they may underestimate a patient’s true systemic pressure.
Treatment Options When Intervention Is Needed
Not everyone with an aberrant left subclavian artery needs treatment. Asymptomatic patients without a Kommerell’s diverticulum, or with a small one, are generally followed with periodic imaging. When treatment is indicated, it is usually because symptoms are significant, the diverticulum is large enough to raise rupture concerns, or the aberrant vessel is forming a true aneurysm. Three broad approaches exist.
Open Surgical Repair
Traditional open repair involves replacing the affected segment of the aorta and reimplanting or bypassing the aberrant subclavian artery. This can mean total arch replacement through a sternotomy, descending aorta replacement through a left thoracotomy, or a combination depending on the anatomy. One series reported 15 patients who underwent arch and descending aortic replacement, with the aberrant subclavian artery reconstructed in situ in all but one case.17PubMed. Graft Replacement of Kommerell Diverticulum and In Situ Aberrant Subclavian Artery Reconstruction Open surgery carries higher upfront risk, particularly for stroke and nerve injury, but tends to produce durable results with low rates of reintervention.
In a dedicated open surgical series of 37 adults, complications occurred in about 30% of patients: vocal cord dysfunction was the most common (11%), followed by chylothorax (8%), Horner syndrome (5%), and spinal deficit (5%). Dysphagia resolved in 92% and shortness of breath in 89%, though gastroesophageal reflux persisted in nearly half of patients who had it preoperatively.18PubMed Central. Outcomes of Surgical Repair of Aberrant Subclavian Arteries in Adults
Hybrid and Endovascular Approaches
Because open repair of the aortic arch is a major operation, less invasive strategies have gained ground. Thoracic endovascular aortic repair (TEVAR) uses a stent graft delivered through the femoral artery to line the aorta from the inside, sealing off the diverticulum. The catch is that the aberrant subclavian artery often arises near other important branches. Simply covering it with a stent graft would cut off blood flow to the left arm and, more critically, to the left vertebral artery supplying the brain. To preserve those circuits, surgeons frequently perform a hybrid procedure: first, a surgical bypass reroutes blood to the left subclavian artery from another vessel (such as the right carotid artery), and then TEVAR is used to exclude the diverticulum.19Journal of Vascular Surgery Cases, Innovations and Techniques. Hybrid repair of Kommerell’s diverticulum with aberrant subclavian artery
Other endovascular variations include custom-fenestrated stent grafts, which have a hole in the graft fabric to allow continued flow into the aberrant artery, and chimney stents placed alongside the main graft to keep branch vessels open.20PubMed Central. Thoracic Endovascular Aortic Repair for Aberrant Subclavian Artery and Stanford Type B Aortic Intramural Hematoma These techniques expand the pool of patients eligible for less invasive repair, but they add complexity and are not yet standardized.
Comparing Outcomes Across Approaches
A multicenter study comparing open, endovascular, and hybrid repair of aberrant subclavian arteries and Kommerell’s diverticulum found that about 83% of patients experienced complete or partial symptom relief at one year, with no significant difference between open repair and endovascular or hybrid approaches in that respect (87% versus 79%). The 30-day stroke rate was about 4% and the 30-day mortality was about 5%. At a median follow-up of roughly three years, overall survival was about 87%.21PubMed. Contemporary outcomes after treatment of aberrant subclavian artery and Kommerell’s diverticulum
Where the approaches diverged was in durability. Reinterventions occurred in about 12% of patients overall, and the endovascular or hybrid group required reintervention more than twice as often as the open group (15% versus 6%), mainly because of endoleaks, which are persistent blood flow into the sealed-off area around the stent graft.22PubMed. Contemporary outcomes after treatment of aberrant subclavian artery and Kommerell’s diverticulum A separate review of hybrid outcomes echoed these concerns, reporting a technical success rate above 95% and low 30-day mortality (about 2%), but a 30-day major complication rate of about 16% and an endoleak rate that the authors flagged as a significant durability concern.23PubMed Central. Outcomes in the treatment of aberrant subclavian arteries using the hybrid approach A study from the Journal of Vascular Surgery put it plainly: if the hybrid technique is used, the mandatory need for long-term imaging surveillance and a high chance of reintervention should be discussed with the patient beforehand.24Journal of Vascular Surgery. Hybrid open brachiocephalic artery revascularization with thoracic endovascular aortic repair for complicated aberrant subclavian arteries
For patients who do undergo open repair through experienced centers, outcomes have been reassuring. In one series of 152 patients with aberrant subclavian arteries, 65 required surgery and survival was 100%, with virtually all patients free of residual symptoms.25Operative Techniques in Thoracic and Cardiovascular Surgery. Repair of Kommerell’s Diverticulum and Aberrant Subclavian Arteries: Classification of the Five Groups in Declining Frequency and Their Operative Approaches
Sex Differences and Demographic Patterns
Aortic arch anomalies are not distributed equally between men and women, and the pattern shifts depending on which specific anomaly you look at. An evaluation of over 1,300 cases of aberrant subclavian arteries found that females predominated among those with an aberrant right subclavian artery, while males were overrepresented among those with an aberrant left subclavian artery.26PubMed. Aberrant subclavian artery (arteria lusoria): sex differences in the prevalence of various forms of the malformation. Evaluation of 1378 observations The reasons for this sex-linked distribution are not well understood and may reflect hormonal influences on vascular development, sex-linked genetic susceptibility, or simply the demographics of the populations that happened to be studied. Regardless, it is worth noting because clinicians may carry a stronger suspicion for certain anomalies depending on the patient’s sex.
Age at presentation also varies with the type of arch anomaly present. As noted earlier, patients with a right arch and aberrant left subclavian artery tend to come to medical attention much younger than those with a left arch and aberrant right subclavian artery. This likely reflects the larger and more symptomatic Kommerell’s diverticula in the right-arch population, which create problems earlier in life.
Living With an Incidental Finding
If you have been told incidentally that you have a right aortic arch with an aberrant left subclavian artery, the immediate question is usually whether something needs to be done about it. For most people, the answer is nothing urgent. Surveillance imaging at intervals your doctor recommends can track the size of any Kommerell’s diverticulum and the caliber of the aberrant vessel itself. If the diverticulum remains small and you have no symptoms, watchful waiting is reasonable.
A few practical points matter in day-to-day life. Blood pressure should ideally be measured on the right arm if you have a right-sided arch with an aberrant left subclavian artery, since the left-arm reading may underestimate your true pressure. If you are planning any procedure involving the aorta or its branches (even an unrelated cardiac catheterization), the surgical and anesthesia teams need to know about your anatomy ahead of time, because guidewire navigation and cannulation strategies change significantly when the arch is reversed and a vessel crosses behind the esophagus. And if genetic testing for 22q11.2 deletion has not been done, particularly if the anomaly was found in childhood or in the setting of other congenital features, it is worth discussing with a geneticist.