Abstract

An Aberrant Right Subclavian Artery (ARSA) is a rare congenita; anomaly (0.4-1.8%) of the aorta in which the right subclavian artery arises from the aortic arch distal to the origin of the left subclavian artery often coursing behind the esophagus to reach the right arm. It courses behind the esophagus in about 80% of cases, between the esophagus and the trachea in 15%, and anterior to the trachea or mainstem bronchus in 5%. Patient with this anomaly rarely have symptoms (90-95%) but when symptomatic the ARSA give rise to symptoms of dysphagia lusoria, dyspnea and chronic cough. In a vast majority of patients ARSA is clinically silent till right radial angiography is performed. We are reporting a case of dissection of the retroesophageal right subclavian artery traveling into the descending thoracic aorta (Stanford Type B) during right radial cardiac catherization performed on a patient presenting with non-ST elevation myocardial infarction.

1. Introduction

An Aberrant Right Subclavian Artery (ARSA) is a rare developmental anomaly (0.4-1.8%) of the aorta in which the right subclavian artery arises from the aortic arch distal to the origin of the left subclavian artery often coursing behind the esophagus to reach the right arm ¹.

While it was fisrt described by Hanuld in 1735; this arterial anomaly in its symptomatic form “dysphagia lusoria” was described by Bayford in 1787 (lusoria= abnormal arterial course) ^{2, 3}.

A German Radiologist, Burkhard Friedrich Kommerell observed that the ARSA often arises from a dilated segment of the descending aorta and described it as remainder of the primitive right dorsal aorta. This vascular anomaly often seen with ARSA but not limited to it was been subsequently named the Lusorian artery or Kommerell’s diverticulum ⁴.

Since the introduction of diagnostic trans-radial catheterization in 1989 and its use for coronary intervention in 1993, the trans-radial approach has become increasingly popular. However, a review of literature shows that successful right radial cardiac catheterization could be successfully performed in only 60% of cases of ARSA ⁵. This is because the right trans-radial approach in patients with ARSA makes it difficult to approach the aorta root and requires the catheter to curve back into the ascending aorta.

We are reporting a case of dissection of the retroesophageal right subclavian artery traveling into the descending thoracic aorta (Stanford Type B) during right radial cardiac catherization performed on a patient presenting with non-ST elevation myocardial infarction.

2. Report of the Case

A 58-year-old, otherwise healthy, woman who presented to our emergency department (ED) after feeling that her heart abruptly began pounding at work. She indicated that, while her work as an airline ground staff involved walking large distances every day, she never experienced such symptoms before. These symptoms persisted for 3-4 hours and patient also developed retrosternal chest tightness and lightheadedness. She had been a lifetime nonsmoker, occasionally drank a glass of wine and had never abused any illicit drugs. An electrocardiogram (ECG) performed in the ED demonstrated a narrow complex tachycardia with no discernable P waves, at a rate of 160 beats per minute. An attempt at closed nose blowing (Valsalva Maneuver) in the ER reverted her supraventricular tachycardia (SVT) back to normal sinus rhythm at a rate of 98 beats per minute. This resolved her palpitations but she continued to have mild discomfort in the center of her chest. Her blood pressure was 143/90 mm of Hg, temperature 98.3⁰F and she was saturating 99% breathing 18 breaths per minute of room air. Her cardiovascular examination was noncontributory. She had no jugular venous distention, a regular heart rate with no murmurs or gallop on auscultation, equal air entry in her lungs and no edema in her extremities. Lab analysis revealed a troponin elevation of 1.39 ng/ml (normal <0.015 ng/ml). All other hematological and biochemical tests were within normal limits. Her elevated troponin was attributed to a Type II Myocardial Infarction from the SVT (likely atrioventricular nodal reentrant tachycardia). An electrophysiological (EP) study and a with possible ablation was planned. However, because of persistence of her chest tightness and elevation in her troponin a cardiac catheterization prior to the EP study was performed to rule out coronary artery disease.

Her right radial artery was accessed using the modified Seldinger technique and a 6 French Glidesheath was placed. A J wire was advanced under fluoroscopic guidance to the level of the arch of the aorta. Even with deep inspiration the wire repeatedly selectively entered the descending aorta instead of the ascending aorta [Figure 1A]. Subsequent attempts to direct an angled guidewire into the ascending aorta resulted in the patient experiencing central crushing chest pain and all catheter and wire manipulations were stopped. Subclavian angiography during catheter withdrawal demonstrated dissection of an aberrantly origination right subclavian artery [Figure 1B]. The patients pain resolved. Cardiothoracic surgery’s guidance was obtained and the patient was taken immediately for a CT (computed tomography) scan.

The CT scan demonstrated dissection of the retroesophageal right subclavian artery [Figure 1C]. The dissection extended down the descending aorta and terminated in the iliac arteries with no obvious malperfusion [Figure 1D]. Her Stanford B dissection was managed medically with an esmolol drip. A repeat CT scan in 3 days did not show any progression of the dissection and the patient remained free of chest pain. She was discharged home on oral beta blockers with a plan for a short follow up with cardiothoracic surgery and a repeat CT scan in 4 weeks.

3. Discussion

The aorta develops in the 3^rd week of gestation ⁶. Normally, the right aortic arch regresses caudal to the origin of the 7^th intersegmental artery which subsequently gives rise to the right subclavian artery. In about 0.4-1.8% of individuals, the regression occurs between the right common carotid and the 7th intersegmental artery. This causes the right subclavian artery to be connected to the left dorsal aorta via the right dorsal aorta, which in normal development would have otherwise regressed. During the course of its development, the origin of the aberrant right subclavian migrates until it is distal to the origin of the left subclavian artery ¹.

The aberrant right subclavian artery (ARSA) courses behind the esophagus in about 80% of cases, between the esophagus and the trachea in 15%, and anterior to the trachea or mainstem bronchus in 5% ⁷. ARSA is seen more often in women and has a female to male prevalence of 3:1 in the general population ⁸. When present, ARSA may be associated with other vascular anomalies like Truncus bicaroticus (19.2%), Kommerell's diverticulum (14.9%), aneurysm of the artery itself (12.8%), and a Right sided aortic arch (9.2%). Prevalence of this anomaly is higher (26-34%) in patients with down syndrome and other congenital abnormalities. Patient with this anomaly rarely have symptoms (90-95%) but when symptomatic the ARSA give rise to symptoms of dysphagia lusoria, dyspnea and chronic cough ^{1, 7}. Rarely, the ARSA may lead to Ortner’s syndrome by causing compression of the recurrent laryngeal nerve leading to stridor ⁹.

A study of 10,260 aortic CTA records of 6,804 patients of Chinese patients reported higher rates of aortic dissection or coarctation in patients with ARSA when compared to the control group (52.6% vs 36.8%, p=0.006; 5.1% vs 0.9%, p=0.007, respectively) ¹⁰.

Iatrogenic aortic dissection when occurring in the context of arteria lusoria tend to be typically be Stanford B in variety and extend down the descending aorta given the location of the origin of the artery in the descending aorta distal to the left subclavian artery ¹¹.

It is often difficult to identify ARSA on the postero-anterior projection during conventional angiography. The guidewire repeatedly entering the descending aorta during the right radial approach should alert the operator to the possibility of this vascular anomaly. This should prompt an oblique view of the right subclavian artery angiogram which would then better demonstrate the origin of the ARSA distal to the left subclavian artery ^{12, 13}.

4. Conclusion

In a vast majority of patients ARSA is clinically silent till right radial angiography is performed. This case highlights the importance of considering this rare coronary anomaly when the J wire selectively enters the descending aorta during right radial catheterization. In such a case, catheterization of the ascending aorta may be difficult or even impossible (7.1%) ¹². Unsuccessful attempts at navigating the wire into the ascending aorta pose the risk of trauma to the endothelial lining and potential adverse outcomes including aortic dissection ¹⁴ and intramural hematoma formation ¹⁵. They should prompt the angiographer to obtain a subclavian angiogram with oblique views and if unsuccessful consider accessing the ascending aorta either from the left radial or the femoral approach.

Acknowledgements

This work is supported, in part, by the efforts of Dr. Moro O. Salifu M.D., M.P.H., M.B.A., M.A.C.P., Professor and Chairman of Medicine through NIH Grant number S21MD012474.

References