Seminar
 

Radial Approach to Right Heart Catheterization and Intervention
Ian C. Gilchrist
Pennsylvania State UniversityPenn State Heart and Vascular Institute Pennsylvania USA

Abstract
Transradial cardiac procedures have many advantages over the femoral approach, but forgotten is a similarly eloquent approach to venous access. Central venous access can actually be easily obtained using the forearm veins without risking the femoral or neck approaches. Whether it is needed for right heart hemodynamic monitoring or diagnosis with a cardiac catheter, as a site for temporary pacing during periods of iatrogenic bradycardia from interventional techniques, or as a site for a transvenous interventional procedure, forearm venous access can provide a reliable and safe entry site to compliment or complete the transradial procedure. Venous access from the forearm can be accomplished efficiently and without compromise by avoiding an otherwise riskier anatomical approach. Understanding venous techniques and recognizing this important adjunct to transradial interventions completes the operator’s radial skills and further enhance the potential of transradial interventions.

Evolution Of Peripheral Venous Approaches To The Central Venous System
The ability to access the central venous system and the human heart has been known since Werner Forssmann first passed a urethral catheter up from his forearm vein into his right heart1. In the early days of cardiac catheterization, access to both the arterial and venous system relied on surgical cut downs. At the conclusion of the procedure, the artery was usually repaired, but the venous access was often forgotten and tied off rather than repaired. With the advent of percutaneous approaches popularized by Sven-Ivar Seldinger2, femoral access became the predominant approach for cardiac catheterization. By the 1980’s and 1990’s percutaneous transfemoral access was generally accepted as the standard-of-care and, in fact, femoral artery access was really needed to facilitate the large diameter equipment of early interventional cardiology.  Techniques previously developed for arm access were in many training programs no longer taught and only occasionally performed in the rare case where femoral access was deemed absolutely impossible. During this period, transcutaneous venous techniques developed using the femoral vein, were combined with newer skills using landmarks to routinely access central veins via the great neck and subclavian veins. These central veins became useful especially for long term monitoring of central pulmonary hemodynamics and application of flow directed  to right heart catheters such as those developed by Drs. Swan and Ganz3.

Transradial arterial access was attempted early in the history of catheterization but failed to be widely adapted due to difficulties with surgical repair of cut downs. It was resurrected in the 1980’s by Campeau 4 and others. Presently transradial techniques have evolved now to the state of being recognized as a safer and better tolerated procedure than the transfemoral approach. While arterial access has been recognized as being fairly straightforward with the right equipment and technique, the need for venous access has often been overlooked. In the worse case scenario, the need for right heart and central venous catheterization been used as an excuse to revert back to a transfemoral procedure. Gilchrist, et al, (2002) published a report pointing towards the utility of forearm venous access in the setting of radial artery access5. This early attempt used primarily veins very distal in the arm that were obtained at the time of catheterization by the physician with a tourniquet. This technique was limited by an inability to find distal veins at times on the distal forearm and occasional failure at blind cannulation next to the radial artery. Subsequently, a slightly different approach was adapted with the access obtained anywhere on the forearm that the pre-catheterization technical staff could find a vein large enough to establish a heparin well venous access. This access site was then exchanged for a radial sheath in the catheterization laboratory large enough to accept the monitoring catheter of other transvenous device. This latter approach met with almost universal success 6. Analogous reports of transvenous forearm access have been reported by several groups with similar success 7, 8, 9.

 

correspondence:  Dr Ian C. Gilchrist Professor of Medicine/Interventional CardiologyPenn State Heart and Vascular Institute Hershey Medical Center, Rm C-1517500 University Drive Hershey, PA 17033-0850 USA
E-mail:icg1@psu.edu

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Radial transvenous access, or more correctly forearm venous access, is actually quite straight forward and can be easily mastered by one with basic transradial skills with little extra effort. The purpose of this paper is to review transradial approaches to the right heart to complete the skill set of the radial interventionalist.

Upper Extremity Venous System: Anatomy and Physiology
The variability of the forearm arterial supply is matched if not exceeded by that of the venous system. The venous system has several advantages over the arterial tree. There are extensive collaterals and redundant passages in the venous system that permit catheter passage once access is obtained. Unlike the arterial tree, the venous system is relatively distensible and can accept larger sized sheaths with only a small increase in spasm risk. Finally, the venous system has low pressure and it can be sealed with simple dressings rather than needing well-positioned hemostasis devices.
While variability is the rule, there are some general anatomical rules that the forearm veins tend to follow as shown in Figure 1. Veins below the antecubital fossa eventually drain into either the lateral system of the cephalic vein or the medial system of the axillary/basilic vein. Medial (ulnar) side veins tend to run a more direct route to the central system passing up the axillary vein directly into the subclavian vein. The veins on the lateral or radial side of the arm below the antecubital fossa tend to pass either medially or laterally in a 50/50 distribution above the antecubital fossa10. Those veins that drain laterally up the hind arm join to form the cephalic vein that makes a right angle turn at the junction of the cephalic and axillary vein just before the subclavian vein as pictured in Figure 2. This junction, also referred to as a “T” junction, may represent a technical challenge that should be recognized but is easily met with forethought. While the veins tend to follow rules, there is often network of cross over veins so that it is possible to end up either medial or lateral on the upper arm despite the opposite intension on entry at the forearm. This is usually not a problem, but part of the technique which should not be a barrier to rapid success.
The physiology of veins is slightly different than arteries. The veins are significantly less muscular and have much thinner walls. While less muscular than arteries, veins are still capable of spasm. This spasm was a significant hazard as reported in the older literature with cut downs. The catheters used in that era were larger (8F) and stiffer with primitive coatings to promote low resistance. Present experience is remarkably free of veno-spasm without using anti-spasm medications on a regular basis. If veno-spasm does occur, it is far more likely to respond to nitrates than the calcium channel blockers that work so well for arterial spasm dilators 11.

Step-by-Step Approach to Successful Venous Technique
Preprocedural Planning and Venous Access:

Planning and preparation is important for efficient use of catheterization laboratory time. When the potential need for right heart or venous access is identified in the planning stages of the catheterization procedure, the pre-procedural technical staff are instructed to place a capped off venous access, also known as a heparin lock or heparin well, in the forearm. This

 

Figure 1: Schematic of right arm veins demonstrating the general location of each venous distribution. Individuals are unique and a broad range of patterns may be seen in clinical practice. (Adapted from Kimber DC, Gray CE. Anatomy and Physiology for Nurses-5th Ed, New York: Macmillian Company, 1919.)

Figure 2: Diagram of right upper arm showing “T” junction of the cephalic/axillary intersection just prior to the origin of the subclavian vein. (Adapted from Kimber DC, Gray CE. Anatomy and Physiology for Nurses-5th Ed, New York: Macmillian Company, 1919.)

This access site needs to be in a position that is accessible during radial artery cannulation such that sites on the backside of the forearm are not useful. While antecubital veins are the only option in some patients, more distal veins in the forearm have the potential of being safer as they tend to be distant from other important neurovascular structures and less likely for a misadventure to cause collateral damage. The access site is then left as a heparin well with a rubber/latex end, as shown in Figure 3, that will later allow needle puncture for sheath exchange in the catheterization laboratory. Pre-emptive venous access by the pre-procedural staff can also be used in cases that venous access may be needed such as for temporary pacing during thrombus extraction or rotational artherectomy procedures. Pre-placed access sites are also useful in acute angioplasty during myocardial infarctions where either temporary pacing or right heart pressures may be needed if the procedure or patient’s condition suddenly changes.

 

 

 

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Figure 3: Example of stopper type device for capping end of an intravenous catheter to form a ‘heparin lock’ or ‘well’. This stopper is later punctured directly with the wire introducer to allow wire passage up the vein. Pictured is Interlink® Injection Site, Baxter Healthcare Corp, USA.

Venous Access in the Cardiac Catheterization Laboratory:
Venous access can alternatively be obtained in the cardiac catheterization laboratory. Here a typical approach with a tourniquet may be used to identify veins. In some cases, vein are apparent without a tourniquet and can be entered in their natural state. In either case, standard micropuncture kits or equivalent to that used in radial artery access can be used. If a tourniquet is applied, it needs to be removed after access is obtained to allow catheters to freely pass up arms. While this may seem obvious, when a tourniquet is placed under sterile drapes, its presence can be easily forgotten.
Exchange of Heparin Lock for Vascular Sheath:
Once the patient is in the catheterization laboratory and being prepared for the procedure, the site of venous access is also cleaned with appropriate bactericidal wash. Next an introducer and a vascular wire of appropriate length for the vascular sheath to be inserted and diameter to pass through the indwelling intravenous catheter are used. The cap of the heparin well is punctured with the introducer needle and the wire is passed up the vein. Wire passage should be without vascular resistance and does not require a tourniquet to be placed. Leaving the introducer needle still in the heparin cap with the wire in place, the operator can grasp both the heparin lock and wire insertion needle together and remove off the wire and place off the sterile field. The wire will then remain in the lumen of the vein extending out onto the sterile field. The appropriate sized vascular sheath can then be passed over the indwelling wire and advanced into the venous system.

 

Pharmacologic Preparation of Vascular Access:
At this point, the central dilator of the vascular sheath is removed along with the introducer wire. The vascular sheath’s sidearm can be flushed with saline or heparinized flush solution. It should be noted that there may not be blood return with active aspiration at this point since the venous pressure is often low and the vein will often collapse under the suction pressure. While the radial artery does much better as a conduit after vasodilators such as nitrates or calcium channel blockers, the venous system in most cases does not need a vasodilator cocktail. In fact, calcium channel blockers are not particularly effective in the veins and only nitrates should be for venodilation.
Passage of Catheter to Central Venous and Pulmonary Circulation:
Our standard right heart catheter has been a 5-French, balloon-tipped, single lumen catheter. This can be used in the standard 110-cm length although access to long lengths such as 125-cm may be helpful in individuals with long arms if very distal extremity venous access is used. The catheter is then passed up the arm with the flow-directing balloon tip deflated. As long as no resistance is encountered, it need not be watched under fluoroscopy. When the catheter reaches the level of the subclavian vein, it is often useful to spot check the location under fluoroscopy. If it is in the subclavian vein or proximal axillary vein, the balloon can be inflated and continued through the right heart under pressure monitoring. If the catheter has passed up the cephalic vein, one needs to observe it’s crossing into the axillary-subclavian junction. The cephalic vein enters in a 90-degree fashion and one should only inflate the balloon when sure that the tip is free in the subclavian and heading towards the heart. Once the catheter is correctly positioned in the subclavian, it can be advanced under pressure monitoring through the right heart unless fluoroscopy is needed to confirm location of the catheter tip.
Venous Access Removal/Site Management:
At the conclusion of using central venous access, the hemodynamic catheter is removed from the central system after the balloon is deflated. The sheath’s side arm is once again flushed noting that return of blood may still not be possible on aspiration due to venous collapse on negative pressure. A vasodilator cocktail once again is not needed. The vascular sheath can then be percutaneously removed and pressure applied to prevent bleeding without waiting for any periprocedural anticoagulation to dissipate. Since only a small amount of pressure will prevent venous bleeding, sites remote from the arterial site can be managed with sterile pressure dressing and no specific hemostasis device is needed. If the venous site is in close proximity to the radial arterial site, the hemostatic device for the artery may also be used to control the venous site. Venous hemostasis usually is well done before arterial hemostasis so typically does not require further time beyond that used for arterial hemostasis.

 

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The steps used in placement of venous access and conduct of the venous procedure are outlined in Table 1. Using this type of approach to right heart catheterization, it is possible to get procedural results consistent with those using the femoral vein. The potential complications of directly puncturing a central vein in the neck are avoided and the benefits from the safety and convenience of the transradial approach remain with this addition to the transradial toolbox. As noted in Table 2 procedural times and x-ray times are similar with the forearm approach compared to the transfemoral for central venous and right heart catheterization.

Table 1: Steps to forearm venous catheterization of the heart.
Pre-procedural
Identify potential need for venous access
Establish venous access and cap intravenous catheter (heparin lock)
Pre-cath lab area is most efficient
Can be done in the catheterization laboratory as an alternative
Cardiac Catheterization Laboratory
Sterile prep of venous access line site
Puncture cap of heparin lock with wire insertion needle
Pass vascular wire through introducer wire up vein without resistance
Slide heparin lock with insertion needle off the wire and dispose off field
Place vascular sheath over vascular wire
Remove dilator and wire from vascular sheath
Flush sheath; no specific vasodilator required
Pass equipment up arm without resistance watching under x-ray at the cephalic-axillary junction
Flow-directing balloon can be inflated in the subclavian vein
Pass equipment to central location as indicated
After Procedure
Remove catheter with flow-directed balloon deflated
Flush remaining vascular sheath; no specific vasodilator required
Remove vascular sheath and apply appropriate pressure
Bandage site to maintain pressure suitable for venous stasis

Overcoming Challenges of Central Venous Catheterization From Peripheral Veins
Venous access:
If the pre-procedural staff can obtain good venous access with a 22-guage or larger diameter IV-catheter, failure to complete the procedure in the catheterization laboratory is rare. Veins are very distensible and compliant allowing use of larger bore equipment. It is important that the pre-procedural staff understands that their work is critical and the intravenous site should be free flowing and not positional in function. Capping the line off with a stopper or heparin lock, (Figure 3), that can be later perforated with the wire introducer needle is also helpful. This avoids the need for manipulation in the catheterization laboratory of other caps such as those used for needleless systems that may need to be screwed off to remove and are slippery under laboratory conditions..


Table 2: Characteristics of patients, procedural times and complications in 280 consecutive patients undergoing either femoral or radial, right and left heart catheterization (adapted from reference #6).

*Arterial time starts with arterial puncture and ends at the conclusion of the procedure in the cardiac catheterization laboratory. The femoral arterial sheath is removed later in a recovery area. Radial sheaths are removed at the end of arterial time while patient is in the laboratory.
AV: arteriovenous, CI: confidence interval.

While forearm veins that are distal to the antecubital fossa all the way down to the wrist can be used, they may not always be present. An antecubital vein is a reasonable second choice that is usually accessible in most patients. Ultrasound equipment can also be helpful in difficult access patients. With ultrasound, one can map out the location of deeper veins such as the Axillary vein or deep antecubital veins. It should be noted that even at the level of the wrist ulnar or radial artery, a vein accompanies each of these arterials similar to the femoral artery and vein. The lateral or medial position of the vein with regard to the artery is very patient specific, but an ultrasound device can localize the vein in regard to the arterial pulse. The operator can then approximate the venous position by palpating the arterial pulse and often obtain venous access in patients who otherwise have little hope for peripheral access.
As noted earlier, a tourniquet on the upper arm will increase the size of the forearm veins. This is often useful in combination with ultrasound in difficult cases. Again this interrogation and access is best accomplished prior to entering the cardiac catheterization laboratory to maintain efficiency. If venous access is needed in the cardiac catheterization laboratory without the foresight of a pre/planned access site, a tourniquet may be useful for access. Under the time pressure of a catheterization laboratory procedure, one must remember to remove the tourniquet after access is obtained as it may impair catheter transit to the central system. In addition, venous engorgement may cause bleeding in the fully anticoagulated patient. Rarely in our experience has an inability to find peripheral access been a cause to switch to another approach to central venous access.

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Venospasm
In the early catheterization literature there are reports of severe venospasm during central venous catheterization and a variety of approaches to combat this disorder have been proposed. Most of these reports involve a brachial artery/vein cut down and the use of a stiff right heart of catheter on the order of 8 French in size. Using the modern approaches with hydrophilic coated, flexible catheters, this problem appears to be primarily of historic interest. If resistance is found on passage of a catheter or wire, if it especially important not to push which will cause perforation or tearing of veins quicker than in the arterial system. Similar to arterial transradial access, a small contrast injection can often define the issue of whether there is spasm, exit of the vein, or perhaps another route that may be better,as the venous system has often-redundant systems that can all lead to the central system.
If venospasm does occur, intravenous nitroglycerine in 100-200 µg dosages is the best approach, although it is rarely needed. Further manipulation of the vein should be minimized while pharmacologic or other changes are made to reduce the tone of the vein. Other causes of spasm that should be corrected include patient anxiety and cold ambient temperatures. Papaverine is another pharmacologic agent that is also reported to break venospasm.
Cephalic-Axillary Junction
For routine modern venous catheterization, either a medial approach up the arm via the axillary vein or laterally via the cephalic vein will be adequate with small flexible catheters to reach the central venous system. Older descriptions of arm catheterization often warn against use of cephalic approach. It was concern since the relatively stiff 8-French catheters used in that period could have problems negotiating the right angle entry into the subclavian system. Present day balloon-tipped devices are far more flexible and come in much smaller diameter that have relegated this concern about the cephalic-axillary junction to a curiosity.
The important issue is recognizing that the catheter is entering via the cephalic vein and as it does it points towards the contra lateral wall of the subclavian vein. If pushed too hard, the catheter could perforate at the junction. If the catheter does not spontaneous turn up the subclavian towards the heart, having the patient take a deep inspiration often realigns the vein to a more favorable position and will allow passage. Barring success, the next step is to introduce a wire into the catheter that has a soft tip or hydrophilic coating and use that to realign the catheter into the subclavian vein. Once confirmed in the subclavian, the balloon on the catheter can be inflated and the procedure continued.

Venous Anomalies
Entry from the right arm is free of anomalies in venous structure that might impede catheter passage. Left arm approaches can potentially be impeded by a persistent left-sided superior vena cava. This results in left sided arm blood draining into the coronary sinus and then right atrium. With modern flow directed catheters, passage through the right heart and out into the pulmonary artery may still occur although the course may appear radiographically strange. With stiff catheters that require manipulation, a persistent left superior vena cava can be a significant impediment to successful right heart catheterization from the left arm. If a persistent left-sided superior vena cava is encountered and cannot be passed due to tortuous vascular course, an alternative right-sided approach will need to be found.
Permanent Pacemakers and Defibrillators
Electrophysiological devices can add a challenge to passage of right heart equipment from the ipsilateral arm. The leads on these devices may have thrombosed the venous system and even without arm swelling, extensive collaterals may be present. Whether or not thrombosis is present is not easy to tell clinically and certainly is not a universal finding. The presence of an electrophysiological device may require extra manipulation with a wire in the hemodynamic catheter to transit the site of lead entry or may be an indication to start with venous access on the contra lateral side.
Prior venous trauma
Major trauma to the ipsilateral chest or upper arm as the attempt for venous access can at times be problematic. Prior cardiac catheterization cut down at the brachial site may result in surgical destruction of the venous system, and resulting in collaterals that cannot be transversed. Brachial artery cut downs are usually repaired, although this sometimes left a stricture that may rarely interfere with transarterial crossing. Venous cut downs are usually closed, sacrificing the vein’s integrity. Such veins will no longer allow catheter passage and contra lateral access is required.
 Motor vehicle and other traumatic injuries of the upper arm and chest need to be considered as venous trauma as they render damage to central venous system.. Again, if catheter passage is met with resistant, a limited angiogram may tell whether there is an insurmountable challenge in which the contra lateral arm can be used.
Another group of patients that have been occasionally problematic are those who have received radiation to the chest. Often these patients have long term indwelling central venous ports for chemotherapy and extensive sclerosis may impede catheter passage to the central venous system. If resistance is encountered, do not push. A limited angiogram will provide information critical to deciding whether one can continue using this particular access site.
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Prevention And Treatment Of Potential Complications
Reported experience from the peripheral access to central venous system has been remarkably free of reports of serious complications. As in any invasion of the vascular system, poor preparation could lead to infection although the brief dwell times really limits this risk. Bleeding at the site is minor compared with the potential found with the arterial system and much easier to control. Since higher pressure hemostatic devices are need not obtain hemostasis on the venous side, nerve crush or handcuff injuries should not happen.
Perforation can occur similar to the arterial system. If perforation is suspected in the peripheral region of the arm, local external pressure will control it. Extra care and heighten vigilance is required if using wires to pass thrombosis central veins as central perforation can potentially occur resulting in an uncompressible hematoma or hemothorax.
Venous thrombosis is also a potential problem. It was noted historically, but may have been due to large and stiffer catheter use. Present day patients who are already undergoing system anticoagulation due to their radial access appear to have a very low risk of venous thrombosis. Part of this may also reflect a practice of immediate removal of venous lines at the conclusion of the procedure. If one leaves a catheter in, for prolonged monitoring after the procedure, enthusiasm needs to be tempered by the historic knowledge of enhance risk for peripheral thrombosis in the arm.

Advance Techniques
While several non-invasive techniques have made routine right heart catheterization obsolete and relegated the technique to primarily problematic patients, the need for central venous access does not end with hemodynamic monitoring. Using the same general approach, the forearm veins can be used for a variety of procedures that may need central venous access either with or without concomitant radial artery access.
Temporary pacing is sometimes needed and in the awake patient a transcutaneous approach is unacceptable. Pacing catheters with balloon tips are available in sizes compatible with arm access and can be easily passed up into the right heart using techniques analogous to those described above for hemodynamics. Transient heart block during acute myocardial infarction angioplasty is one example of that arm access whereas temporary pacing works well as these patients are often highly anticoagulated making central vascular stick particularly  hazardous. Similarly, transient bradycardia induced by rotational artherectomy therapy or various thrombus extraction devices can be treated using the peripheral venous access such that the arterial procedure can be done using the radial artery if appropriate sized arterial equipment is available.
Right ventricular biopsy is also reported successfully via a forearm approach. Moyer et al (2005)  reported12 using 7-French biopsy equipment passed up medially from the forearm to avoid the cephalic/axillary junction with excellent results. This equipment is relatively stiff with no trauma at the bend of the cephalic vein. Several of their patients had repeat procedures by this route with no thrombosis or apparent chronic injury.
Other interventional venous procedures should be possible via the peripheral arm approach. Potentially central venous thrombosis or superior venacaval syndromes might be approachable depending on the size requirements of the devices. The main advantage to an arm approach rests in the low risk of bleeding  despite the use of significant anticoagulation.

Likewise, facility with using a peripheral venous approach to enter the central venous system can be useful in the occasional patient who is very anticoagulated either iatrogemically or due to underlying hepatic failure. These patients can now have prompt evaluation of their central hemodynamics without reversal of anticoagulation or exposure to blood products.

Summary
Transradial arterial access has been an important evolutionary advance in cardiology that has been a timely development in the setting of ever more potent antithrombotic regimens. Adding techniques to access the venous system in the same eloquent style further enhances the transradial procedure and provides an enhanced skill set to the transradial operator. The transvenous techniques are remarkable simple and easy to master, yet few operators have considered the potential use of this approach.

References
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9. Lo TSN, Buch AN, Hall IR, Hildick-Smith DJ, Nolan J. Percutaneous left and right heart catheterization in fully anticoagulated patients utilizing the radial artery and forearm vein: A two-center experience. Journal of Interventional Cardiology 2006;19:258-263.
10. Chun HJ, Byun JY, Yoo S-S, Choi BG. Tourniquet application to facilitate axillary venous access in percutaneous central venous catheterization. Radiology 2003; 226:918–920.
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