Suggested Bony Landmarks for Safe Axillary Artery Access

Abstract: Objective. To identify a fluoroscopic bony landmark for safe percutaneous axillary artery cannulation. Background. No bony landmarks exist to guide safe percutaneous axillary artery cannulation, which is an important alternate access site for catheter-based procedures in selected patients. Methods. We retrospectively analyzed 51 consecutive percutaneous axillary artery sheath angiograms and attempted to correlate a fixed bony landmark to the proximal end of the third part of the artery. Proximal to this site, no cords of the brachial plexus traverse the anterior aspect of the vessel. Moreover, this site is proximal to the subscapular branch of the axillary artery, the first branch of its third part, and a sentinel component of the scapular anastomosis responsible for collateral blood flow to the arm. Results. With the arm abducted at 135°, the subscapular artery originated at, or distal to, the inferior border of the glenoid cavity, as seen on fluoroscopy in the anterior-posterior projection, in all patients. The origin was within 5 mm distal to the inferior border of the glenoid cavity in 17 patients (46%), 5-10 mm in 13 patients (35%), and between 10 mm and 20 mm in 7 patients (19%). Conclusions. With the arm abducted, the origin of the subscapular artery correlates well with the inferior-most aspect of the glenoid cavity of the scapula under fluoroscopy. Axillary artery cannulation medial to this bony landmark typically lands the sheath in the second part or proximal end of the third part of the artery, thereby theoretically sparing injury to the brachial plexus and the subscapular artery.

J INVASIVE CARDIOL 2018;30(3):115-118.

Key words: axillary artery cannulation, large-bore catheters, high-risk PCI, subscapular artery

There has been a growing interest in the axillary artery as an alternate conduit to host large-bore catheters required for percutaneous endovascular valve replacement and hemodynamic support in patients with hostile aortoiliac segments.^1-4 However, not much attention has been paid to avoiding neural and vascular complications during its percutaneous cannulation, and unlike the common femoral artery, no bony landmarks have been described to aid safe axillary artery cannulation. 

The axillary artery originates at the lateral margin of the first rib as a continuation of the subclavian artery and ends at the inferior border of the teres major muscle, where it continues as the brachial artery. It is divided into three parts (Figure 1) based on its relation to the pectoralis minor muscle.⁵ Although the brachial plexus has a complex intimate anatomical relationship with the axillary artery, it is noteworthy that the first part, second part, and proximal end of the third part of the axillary artery do not have any brachial plexus cords on their anterior surface. On the other hand, the third part, beyond its very beginning portion, has brachial plexus cords and their respective peripheral nerve branches traversing its anterior surface (Figure 2).

The subscapular artery is the largest branch of the axillary artery and the first branch of its third part (Figure 1). It contributes to the scapular anastomosis (Figure 3), which supplies collateral blood flow to the brachial artery from the subclavian artery.⁵

A cannulation medial to the subscapular artery should be in the second part or proximal end of the third part of the axillary artery, and therefore at least theoretically be less likely to cause neural damage to the brachial plexus cords. Such cannulation can also potentially avert upper-limb ischemic and thrombotic complications during invasive catheter-based procedures, especially when large-bore sheaths are in use, by maintaining collateral blood flow to the brachial artery through the scapular anastomosis. Furthermore, it can prevent accidental laceration of the subscapular artery and the abundant vascular branches of the third part and hence reduce bleeding complications. The purpose of this study is to propose a bony landmark that can be used to identify the origin of the subscapular artery, in an attempt to help guide safe percutaneous axillary artery access. 

Methods

Consecutive patients who underwent interventional or diagnostic procedures via percutaneous axillary artery approach at our institution between January 2011 and October 2017 were retrospectively identified. Axillary artery approach was utilized due to the lack of an alternate suitable arterial access. All demographic, clinical, and periprocedural data were recorded in a database and obtained from hospital and outpatient record review.

Axillary artery cannulation was routinely performed with the arm abducted over the head at around 135°. This angle renders the vessel highly palpable in the deltopectoral groove. An axillary artery angiogram through a 6 Fr sheath, angled away from the vessel, was routinely performed in the anterior-posterior projection. 

Axillary artery sheath angiograms, recorded using cine fluoroscopy, were reviewed. The relationships between the subscapular branch of the axillary artery and the visible bony landmarks were recorded.

Statistical analysis. Continuous variables are presented as median with interquartile range (IQR) and categorical variables are presented as frequency with percentage.

Results

Axillary artery sheath angiograms were reviewed from 51 procedures performed in 37 patients. The axillary artery approach was deemed necessary in all patients due to severe aortoiliac disease precluding common femoral artery approach. The patients were elderly (median age, 69 years; IQR, 64-74.5 years) and 51.4% were males. There was a high prevalence of systemic hypertension (97.3%), coronary artery disease (91.9%), and diabetes mellitus (59.5%). Patient characteristics are summarized in Table 1.

The left axillary artery was utilized in 40 procedures (78.4%) while the right was utilized in 11 procedures (21.6%). Nine patients (19%) had >1 procedure utilizing the axillary artery, with the majority being done from the left axillary artery. Procedure characteristics are summarized in Table 1.

On identifying the relationship between the subscapular artery origin to a fixed bony landmark, it was noted that the subscapular artery originated at, or distal to, the inferior border of the glenoid cavity, as seen on fluoroscopy in an anterior-posterior projection in all patients. This finding was consistent for both right and left axillary arteries and on repeated angiograms in patients who underwent >1 procedure. 

The origin of the subscapular artery was within 5 mm distal to the inferior border of the glenoid cavity in 17 patients (46%), between 5 mm and 10 mm distal to the inferior border of the glenoid cavity in 13 patients (35%), and between 10 mm and 20 mm in 7 patients (19%) (Figure 4).  

Discussion

The axillary artery is often comparable in size to the common femoral artery, and is less frequently affected by calcification or atherosclerotic disease.⁶ This makes it a suitable choice not only for coronary and peripheral interventions but also for catheter-based hemodynamic support or transcatheter aortic valve replacement (TAVR) requiring large-bore arteriotomies, when no other suitable vascular access site exists. Historically, surgical exposure has been utilized for axillary artery cannulation due to vascular and neural concerns. Nevertheless, percutaneous axillary artery approach has been employed, with acceptable outcomes, for TAVR and catheter-based ventricular assist devices.^1-4 

In the current study, we found that the inferior border of the glenoid cavity, as seen under fluoroscopy in an anterior-posterior projection with the arm abducted at approximately 135°, provided a reliable bony landmark for the subscapular artery. The subscapular artery origin was at, or distal to, the inferior border of the glenoid cavity in all reviewed cases. The relationship was consistent for both right and left axillary arteries and in patients with multiple angiograms.

Major concerns regarding vascular and neural injuries exist when using the axillary artery for percutaneous catheter-based procedures. We propose that accessing the axillary artery proximal to the origin of the subscapular artery (in its second part or in the proximal end of its third part) may, at least theoretically, be conducive to avoiding these complications.

Brachial plexus injuries occur in 0.6%-13.0% of patients undergoing percutaneous axillary artery approach.^7,8 The cords of the brachial plexus surround the second part of the axillary artery (Figure 3), as implied by their names, medially, laterally, and posteriorly leaving the anterior surface of the second part and proximal end of the third part of the artery free of any cords or branches.⁵ The high incidence of brachial plexus injuries appears to occur more frequently on cannulating the distal third part of the artery as a result of multiple mechanisms, including: direct damage to the nerves, closely embracing the distal third part, by the needle or sheath; ischemia of the nerves due to arterial thrombosis; and compressing hematomas within the fascia.^8,9 Axillary artery cannulation proximal to the subscapular artery should be in its second part or proximal end of the third part in order to, at least theoretically, avoid brachial plexus injury, since the anterior surface of the vessel in its aforementioned parts is free of significant neural elements.

Bleeding and hematoma formation are reported to occur in 2.2% of patients undergoing percutaneous axillary approach.^8,10 Avoiding laceration of the subscapular artery and the abundant vascular branches of the third part during axillary artery cannulation might, at least theoretically, decrease the likelihood of bleeding and hematoma formation. Even small contained perivascular hematomas can result in disproportionate clinically manifest nerve injuries due to the presence of an inelastic fascial compartment, namely, the medial brachial fascial compartment (MBFC). The MBFC extends distally from the humerus and surrounds the neurovascular structures of the axillary fossa.¹¹ If required, hemostasis can be achieved by manual pressure medial to the proposed cannulation site where the axillary artery can be compressed against the first rib and intercostal space.

Procedure-related occlusion of the axillary artery requiring surgical intervention is described in at least 1.2% of cases in the literature.¹⁰ It may theoretically be related partly to a compromise of the scapular anastomosis, which provides collateral circulation to the brachial artery through the subscapular artery directly from the subclavian artery (Figure 3).^5,12 Axillary artery cannulation proximal to the subscapular artery origin might reduce the likelihood of intraprocedural upper-limb ischemia, especially when using a large-bore sheath, and avoid the smaller distal axillary or brachial arteries.

Study limitations. This study was a retrospective analysis performed at a single center and the patient sample size is small. This paper only suggests a theoretically safe bony landmark; hence, prospective studies involving axillary artery cannulation employing this proposed “safe bony landmark” are needed to determine if employing this approach does indeed translate into clinically superior outcomes. Although not seen in our series, infrequent variations in the branching pattern of the axillary artery have been reported.^13,14 The true incidence and clinical implication of such variations are unclear; however, their presence is noteworthy and should be considered during percutaneous cannulation.  

Conclusions

(1)    In addition to the first part, which is typically favored by surgeons to cannulate during surgical cutdown, the second part and proximal end of the third part of the vessel may also be a safe zone for percutaneous cannulation, since no element of the brachial plexus straddles the anterior aspect of the vessel here.

(2)    With the arm abducted, this portion of the axillary artery can be identified under fluoroscopy in the anterior-posterior view by identifying the inferior border of the glenoid cavity. This bony landmark marks the takeoff of the subscapular artery, which is the first branch of the third part of the axillary artery. An access medial to this bony landmark will land the operator in the second part or proximal end of the third part of the axillary artery. 

(3)    Moreover, by accessing the axillary artery in its second part or proximal end of its third part, the arteriotomy site is always medial to the subscapular artery takeoff, which is a sentinel component of the scapular anastomosis. This anastomosis is an alternate source of blood supply to the brachial artery from the subclavian artery, thereby theoretically lowering the chance of intraprocedural upper-limb ischemia, especially when employing a large-bore sheath as in TAVR or transcatheter left ventricular assist devices for high-risk percutaneous coronary interventions.

References

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From the Department of Cardiology, Newark Beth Israel Medical Center, Newark, New Jersey.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted November 22, 2017, provisional acceptance given December 4, 2017, final version accepted December 11, 2017.

Address for correspondence: Najam Wasty, MD, FACC, Director, Cardiac Catheterization Lab, Newark Beth Israel Medical Center, 201 Lyons Avenue at Osborne Terrace, Newark, NJ 07112. Email: najam.wasty@rwjbh.org