A Perspective on Sheath Selection and Access Sites for Coronary Angiography

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Figure 2.
Table 1.
Figure 3.
Figure 5.
Table 2.
Figure 4. The palmar arch. This illustration is used with permission of the Transradial Center on Angioplasty.Org, online at http://www.angioplasty.org/radial
Author(s): 

Margaret A. Coburn, RT(R)(CI), RCIS, Jefferson School of Health Professions, Philadelphia, Pennsylvania, and Richard J. Merschen, MS, RT(R)(CV), Pennsylvania Hospital, Philadelphia, Pennsylvania

Abstract
Numerous access and sheath options are available to the interventional cardiologist when performing percutaneous transcatheter procedures. Depending on the procedure, the radial, brachial, or femoral access routes may be used for coronary angiography. Once access is achieved, sheaths offer physicians a safe method for exchange of multiple catheters and wires. Radial artery access is being used more commonly in the United States as results of positive trial data are presented, and operator skill and experience increases. This manuscript will include an overview of access sites and sheath options, as well as a discussion on the practical applications for all access routes that are available for cardiac catheterization.

Introduction
The advancement in percutaneous coronary angiography techniques and equipment affords many more options to practitioners in securing vascular access. The interventional cardiologist needs to carefully plan the procedure, with the goal of a safe and uncomplicated cannulation of the vessel. Since vascular complications are the most common set of post-catheterization problems, the selection of the best access route maximizes safety and reduces complications. Vascular complications can result in adverse impacts and require additional hospitalizations, transfusions, and surgical procedures to repair the vessel. It is crucial to select the best access route to ensure successful procedural outcomes and improve patient safety. The selection of the most appropriate site of access depends on procedural complexities, operator experience, patient anatomy, and other factors (Table 1). There are devices such as ultrasound guidance, micropuncture systems (Figure 1), and other adjunct devices available to assist physicians in achieving access. These advancements, as well as increased operator skills, have greatly reduced procedure times and complications.

The insertion of a sheath preserves a constant source of arterial access. In addition, the sheath offers the physician a safe method for the exchange of multiple catheters and wires while maintaining hemostasis at the access site via a one-way valve on the sheath. Sheath sizes range from 4 French (Fr) to 24 Fr for percutaneous procedures, with most using 4-6 Fr for diagnostic angiography. Sheath sizes that exceed 10 Fr are usually reserved for special procedures, with the largest used for procedures such as transcatheter valve replacement. Selection of the sheath is based on the size of the catheters employed in the procedure (Figure 2). Catheter size is often determined by operator preference and patient anatomy. Technology has advanced to allow sheath and catheter diameter to become smaller over the years. Contrast media and automatic contrast delivery systems have also improved, and provide better angiographic quality at smaller French sizes. There are some operators who choose to use 4 Fr systems for all diagnostic procedures, barring any patient pathology that may require a larger diameter system. This decision is usually based on the desire for patient comfort, as well as the reduced incidence of procedural complications. These include catheter occlusion of the coronary ostium,(1) vasospasm, and other vascular incidents. Good quality angiography can be achieved in most patients using a 4 Fr system.(2) Generally, the sheath size is kept as small as possible in order to minimize the vascular puncture and therefore, reduce complications. However, there are patients who require larger lumen catheters to visualize the vessel. The current standard is the use of a 5 or 6 Fr sheath for diagnostic angiography, since this provides optimal results in situations when vessels are difficult to access and opacify.(3)

Femoral Access
The femoral artery approach is still the most commonly used route for vascular access in the United States. Some cardiac catheterization procedures require access of both artery and vein. This includes assessment of valvular heart disease, coronary angiography that requires additional right heart hemodynamic measurements, and procedures that require pacemakers or additional venous access. The femoral approach, for these cases, provides access within the same area. Many operators also believe it is the best option for advanced interventional procedures and equipment, and provides higher procedural success rates. In the setting of an emergency or complicated intervention such as the use of the “kissing balloon” technique, complex stenting, complex bifurcation lesions, and/or rotational atherectomy, femoral access gives the operator greater flexibility. In many of these cases, a 7 or 8 Fr sheath and catheter may be required for successful outcomes. Additionally, anomalous takeoff of the coronary artery, complex graft anatomy, transcatheter valvuloplasty, and staged procedures may be better suited for the femoral approach (Table 1). However, according to a meta-analysis by Jolly et al, femoral access bleeding complications are higher (2.3%) compared to the radial approach,(4) and require greater post-procedural nursing care and prolonged bed rest for monitoring complications. This meta-analysis established a standardized major bleeding definition as one of the following: fatal bleeding, intracranial hemorrhage, bleeding with a ≥3 g/dL hemoglobin drop, and bleeding-associated transfusion or surgery,(4) criteria also supported by the American College of Cardiology (ACC). These occurrences have been significantly reduced through the use of closure devices such as Perclose (Abbott Vascular, Redwood City, CA), Starclose (Abbott), and Angio-Seal (St. Jude Medical, Minnetonka, MN). With the use of these devices, patients can ambulate and be discharged within 2-3 hours post-catheterization.

Other considerations for the femoral artery approach include patients on hemodialysis and patients who have failed the Allen’s test. Patients who have undergone radial artery harvesting for bypass surgery, those who have previously had multiple radial procedures or a-lines, patients with breast cancer, and patients who have undergone a mastectomy are probably better candidates for the femoral approach. Patients with long-standing hypertension may have extremely tortuous vessels, making upper extremity angiography much more complex due to tortuosity of the vessels coming off the aortic arch.

It is our opinion that acute myocardial infarctions (MIs) should always be done via the femoral approach, because of the potential for intra-aortic balloon pump (IABP) insertion, transvenous pacemaker, and Swan-Ganz placement. In an emergency situation, using the groin allows easy access to two femoral arteries and two femoral veins for central line placement. The limited sheath size in the upper extremity can severely restrict the interventional cardiologist in emergency situations.

Upper Extremity Access
Upper extremity access is being performed with greater frequency in the United States as results of randomized trials are presented, and practitioner training and expertise have increased.(4) Many studies have concluded that lower bleeding complications (Figure 3), better patient outcomes, and lower hospital costs are associated with access of the radial artery compared to the femoral artery. The radial artery approach, however, requires considerable operator skill and experience due to the susceptible nature of the smaller vessels to irritation, spasm, and tortuosity. This technique provides several advantages to the patient when performed by a skilled operator, including earlier ambulation and reduced hemostasis complications. Radial access serves as an alternative to the femoral technique in obese patients (Table 1). Since the average radial artery lumen is approximately 2mm, the operator is limited in sheath size. As a result, a rule of thumb for radial artery access is to not go above 6 Fr due to the increased risk of vasospasm.(5) Aggressive use of vasodilators like verapamil or nitroglycerin are required to aid in catheter manipulation and prevent vascular injury. The dominant hand of the patient should be considered in radial cases when both radial arteries are patent, and if possible, the contralateral side should be accessed. Often, a micropuncture needle (Figure 1) is used for initial access, as it produces less trauma, irritation and spasm to the vessel. Radial artery occlusion is rare and likely related to the ratio of the arterial diameter to the sheath.(6) The incidence of radial artery occlusion is approximately 1-3% due to intima-media thickening, which may be a result of acute inflammatory reaction and endothelial dysfunction post procedure, as reported by Yan.(7) Most of these occlusions tend to be benign, but can limit future access via the radial approach. Moreover, Yonetsu reports in a study that assessed 73 radial arteries post-intervention that significant acute injuries and chronic intimal thickening of the radial artery occurred after transradial coronary intervention.

This trauma and narrowing of the vessel was significantly greater in the proximal and distal areas of the radial artery in patients who underwent repeat transradial interventions. Therefore, the use of the radial artery as a conduit in coronary bypass surgery post-transradial intervention should be avoided until long-term patency of the artery can be demonstrated(8) (Figure 4 - please note this illustration is used with permission of the Transradial Center on Angioplasty.Org, online at http://www.angioplasty.org/radial). Performing an Allen’s test is critical in determining the availability of the radial artery for cardiac catheterization and is used to ensure patency of the ulnar artery distally if thrombus occurs. A study conducted by Kohonen in 2007 with 145 patients who underwent the Allen’s test showed that 77% of patients had a normal Allen’s test, allowing for a safe transradial approach.(9) Other literature states that the rate is closer to 90%. Either way, the Allen’s test is a significant indicator for radial access.

The brachial artery approach can be used when there are known lower extremity vascular issues such as peripheral vascular disease, vessel tortuosity, or obesity. However, brachial artery access is often associated with higher risk of thrombotic complications than the radial artery (Table 1). Patients are also vulnerable to compartment syndrome via the brachial route, because of the complex network of muscle compartments and nerves located at the puncture site. It is important to carefully monitor the brachial artery to quickly identify potential hematomas. The best way to observe the arm is to do 15-minute checks post-cath for at least 2 hours, and regularly assess radial and ulnar pulses. The use of a paper tape to measure the circumference of the arm allows the post-cath team to monitor the development of a hematoma. The brachial approach does not have the structural hemostasis support that the femoral and radial approaches have, making it necessary for a vigilant staff to observe the patient post-procedurally.

Axillary artery access is an emergency option for arterial cannulation when other routes are not readily available. When using the axillary artery, the patient’s hand is placed behind their head, the axillary area is prepped, and access can be gained. The axillary artery was often used for access in the 1980’s and early 1990’s, especially in interventional radiology. As endovascular techniques became more advanced, brachial angiography proved to be safer and supplanted the axillary approach. Radial artery access is now replacing brachial artery access because of lower complication rates. The axillary approach had high complication rates and hemostasis was difficult to achieve, because of a lack of bony support to compress against. Additionally, most of the punctures used for axillary artery approach involved the use of a double-wall needle.(10)

Jugular Vein Access
In cases where right heart hemodynamic measurements are necessary, the internal jugular approach is used as an alternative to the femoral vein, if needed. Some physicians use ultrasound to guide access to the internal jugular vein in order to gain a high approach and avoid the upper lung tip.(11) The right side jugular vein is the most direct route to the superior vena cava. Endomyocardial biopsy, used for monitoring of a patient post heart transplant, is often performed through the right internal jugular vein to gain access to the right ventricle. While a 7 Fr sheath is used to accept 50 cm biopsy forceps, the development of longer, 104 cm bioptomes has allowed the use of the femoral vein approach for this procedure, utilizing an 8 Fr sheath and 7 Fr forceps.

Access Philosophy
A discussion about access philosophy should include the currently debated issue of radial versus femoral artery access. The radial artery approach has been the subject of much study, relative to reducing post-procedural bleeding complications. Should every patient be accessed through the wrist? Periprocedural complications and problems such as vasospasm, and subclavian, axillary, and innominate artery tortuosity that can accompany the radial artery technique can extend the length of the procedure. Access difficulty can also complicate a radial artery approach that would otherwise be a straightforward case in the femoral approach.

Many interventional cardiologists perceive that the decrease in post-procedure vascular complications with radial access is balanced by technical difficulty, increased fluoro time, and radiation exposure to the patient.(4) Studies comparing radial access to the femoral artery approach have generally not included those patients who were at risk of procedural complications, those who are relatively sick, and those who may have required additional interventions such as a pacemaker or an intra-aortic balloon pump (IABP). These studies also do not take into consideration operator experience, the number of inadvertent sticks in obtaining access, and the exact location of femoral access.(12) The trial review conducted by Jolly et al revealed in the study limitations that many of the trials were small, did not detail the number of patients screened, and were performed in highly expert radial centers, which may limit the external validity of these results.(4)

When a cardiac catheterization lab wants to reduce the incidence of bleeding complications in patients, all access routes and potential issues need to be considered. The optimal access site for catheterization should be the focus, whether radial or femoral, as well as the appropriate steps to reduce the complications associated with that technique. There are several aids available to the interventionalist in order to obtain precise access. Ultrasound guidance, micropuncture needles, and fluoroscopic guidance all contribute to the best possible stick, and each reduce the number of sticks. The use of a femoral arteriogram post-procedurally allows assessment of the access site for hemostasis, and whether manual compression or a closure device should be employed. This step also alerts the operator to any complications early on, so that a proper strategy can be employed to limit the extent of any complications.(11)

Sample Case Presentations
A 56-year-old male experienced chest pain radiating down the left arm, becoming progressively worse. A stress test revealed a reversible anterior wall defect. A history of peripheral vascular disease, an ankle-brachial index of 0.65 on the left leg and 0.63 on the right leg, as well as diminished femoral pulses, necessitated angiography via the right radial artery. Cardiac catheterization demonstrated coronary artery disease that could be treated with medical therapy. Post-procedurally, an abdominal aortagram was performed. It revealed total occlusion of the abdominal aorta, which collateralized the femoral arteries via the inferior mesenteric artery and other abdominal collaterals (Figure 5).

A 70-year-old male presented with chest pain and a previous history of coronary artery stenting. He also had an aorto-bifemoral bypass graft and severe scarring of the femoral artery access sites. Radial angiography allowed the study to be performed safely and avoided damaging the bypass areas.

A 60-year-old male with a history of coronary artery bypass (CABG) experienced recurrent stenoses and occluded grafts post-CABG. The bypass conduits consisted of a left internal mammary artery (LIMA) graft and harvest of the left radial artery due to the lack of other vessels available for graft placement. Right radial artery access was ruled out as a result of the LIMA graft. The study was performed via the femoral approach without complication. It was determined that treatment would be addressed as a staged intervention. Femoral artery access allowed the patient to have multiple procedures performed safely.

A 65-year-old female with a history of congestive heart failure and coronary artery disease had a previous diagnostic catheterization via the radial artery. New onset of angina necessitated the evaluation of the radial artery for a follow-up cath. A thrombosis of the radial artery was revealed with accompanying persistent tingling in her thumb and index finger. Due to this finding and existing renal insufficiency, the femoral approach was used to preserve the contralateral radial artery for potential future bypass placement.

Pediatric Procedures
Today, cardiac catheterization is the treatment of choice for many congenital heart defect lesions rather than surgery. Most procedures are performed via femoral access to provide the best support for manipulation of multiple catheters and devices (Table 2). In specific situations, such as cardiac catheterization post bidirectional Glenn procedures and endomyocardial biopsy post transplantation, the right internal jugular vein access is preferred.

As in adult angiography, the smallest sheath to successfully perform the study (3 or 4 Fr) is used to minimize damage to the vessel.(13) For right heart studies, the right femoral vein is used, as it is a straight course to the right atrium.(14)

Examples of pediatric transcatheter procedures include percutaneous stenting of coarctation of the aorta, which requires the sheath size be large enough to accommodate the profile of the balloon and stent chosen for the dilatation. This could mean a balloon as large as 11 to 25mm in diameter, depending on the size of the patient and degree of narrowing. A long sheath is inserted in the femoral artery and positioned past the coarctation segment. An appropriately-sized stent is mounted on a delivery balloon and then placed in position across the coarctation segment to dilate the aorta.(13)

Atrial septal defect (ASD) closure is usually performed after 3 years of age. The sheath size depends on the type of device that will be used in the procedure. For example, the Helex septal occluder device (Gore Medical, Flagstaff, AZ) is deployed through a 10 Fr sheath in the femoral vein. The Amplatzer requires a 6 to 9 Fr femoral vein delivery system to deploy the device. Additionally, a long 10 Fr sheath is placed in the left femoral vein for insertion of an intracardiac echocardiography (ICE) catheter if transesophageal echocardiogram (TEE) is not used, while a 4 to 5 Fr sheath is placed in the right femoral artery for arterial pressure monitoring.(15)

Sheath Length
Most procedures will employ a standard sheath length. In some cases, the length of the sheath can be a consideration for the practitioner and is often based on the anatomy of the patient. Some practitioners choose to use long sheaths, as these give better support during catheter manipulation, especially in tortuous vessels. A 15 cm sheath will only reach the mid iliac. Severe tortuosity may require a longer sheath, sometimes up to 23 cm, to position above the bifurcation.(16) In radial artery access during an intervention, a longer sheath is sometimes preferred in order to avoid vessel spasm and maintain smooth access for guide catheters.(17)

Sheath Maintenance
Good sheath maintenance throughout the procedure has reduced complications over the years. Early case review has determined that risks during coronary angiography 35 years ago were considerably higher than today. For example, it is general knowledge today that in-procedure thrombus formation and occlusion is attributed to the femoral sheath. Years ago, it was not standard procedure to flush the side arm of the sheath at catheter exchanges until the correlation between the femoral sheath and thrombogenesis was discovered. Once the practice of flushing the sheath was established, this complication was nearly eliminated.(18)

Thrombus begins to form on the catheter’s outer surface during the procedure. As the catheter is removed, this material is stripped from the catheter by the sheath tip. The next catheter inserted will carry this thrombus as it is advanced, depositing it near the coronary ostium. Embolization can then occur on its own or with contrast injection. Scrupulous sheath management through regular aspiration and flush of the sheath after new catheter insertion must be employed for this reason. Some operators choose to use a continuous flush during percutaneous coronary angiography. A continuous pressurized flush system maintains sheath patency and is typically used when a patient is transferred to the nursing unit post-intervention, to provide a means of monitoring invasive pressures until the sheath is pulled. In the cath lab, this technique can be employed as part of the regular cardiac catheterization routine. Once the sheath has been introduced into the femoral artery, it is aspirated, flushed, and connected to a pressurized flush system at 30mL/hour drip to avoid clot formation within the sheath.(16)

Conclusion
Practitioners have many considerations for sheath options and access sites in coronary angiography, and for the most part, the choice is based on training, personal preference, and patient specifics. Techniques are always evolving to improve performance. Most advances in sheath practices and sheath maintenance have been to the benefit of the patient. Sheath sizes have become smaller in diameter, reducing trauma to the vessel and limiting hemostasis complications, providing greater patient comfort and early ambulation. In addition, the smaller catheter size also reduces the incidence of occlusion of the coronary ostium by the catheter tip during angiography. However, small catheters still pose challenges. They are sometimes inadequate in sufficiently opacifying the vessel when using hand injection. They are difficult to manipulate and severely limit the ability to perform complicated procedures, and therefore, are optimal only for elective, non-interventional procedures.

Emerging percutaneous technologies such as electrophysiology studies and ablation, valvuloplasty, valve repair, aneurysm repair, congenital lesion procedures, and septal defect closures require femoral access. In certain cases, radial artery access offers several advantages that are very attractive from the view of access site complications, patient discharge, and reduced hospital costs. The reduction in bleeding complications in any cardiac catheterization department can be addressed by not only initiating a transradial program, but also by utilizing methods to reduce the number of unintentional sticks, and assessing the puncture site at the end of the procedure for proper hemostasis management and post-procedure patient care. The use of all available access sites optimizes the ability of the efficient cardiac catheterization lab to perform safe, effective, state-of-the-art catheterizations.

The authors can be contacted at richardmerschen@verizon.net

This article received a double-blind peer review from members of the Cath Lab Digest editorial board.

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References: 

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