Trans-Radial Coronary Angiography.
Haroon Rashid| May 13, 2010.
Trans radial access is much more comfortable for the subject as it does not compromise the mobility in the immediate post procedure period unlike trans femoral procedures. More over, access site bleeding problems are much lower compared to femoral arterial access. But the down side of trans radial procedures is the sharp learning curve and the higher radiation exposure for the operator. Another problem is spasm of the radial artery which can limit the number of catheter exchanges and sometimes necessitate change over to the femoral route. Radial route does not need prolonged manual compression for hemostasis. Arterial access sheaths can be removed soon after the procedure even on anticoagulation in case of percutaneous interventions. There is a small rate of late loss of patency of the radial artery after trans radial interventions, though these seldom produce clinical ischemia. Allens test for documenting the adequacy of the palmar arch would be a pre-requisite prior to trans radial access, keeping this aspect in mind.
The procedure is initiated by localising a good radial artery pulsation a few centimeters above the wrist. A small skin fold is lifted and local anaesthetic instilled subcutaneously. A small nick is made with the scalpel, again after manually lifting a skin fold to avoid nicking the radial artery. Then an intravenous cannula is slowly and steadily introduced into the radial artery, trying to avoid a counter puncture. Once the back flow of blood is noted at the proximal end of the cannula, the tip may be introduced minimally forwards to secure the vessel access and the stylet withdrawn, leaving the cannula in the artery. Then a hydrophilic guide wire is threaded through the cannula, making sure that it is done only when a good retrograde jet of blood is visible. The wire should pass smoothly into the artery without any resistance. If necessary, the wire track can be visualised on fluroscopy. Once the wire is securely within the radial artery, the cannula is removed over the wire and the radial sheath, usually 5F threaded over the guide wire and the guide wire removed. The side arm of the valved sheath is opened to ensure a good back bleed before injecting the cocktail of dilute diltiazem and nitroglycerin to prevent spasm of the radial artery. Heparin can be given either intra arterially or intravenously at this point. Once the sheath is ready, a 0.035³ J tip guide wire is gradually introduced into the sheath using an introducer and passed up the radial artery into the brachial, axillary and subclavian arteries, under fluroscopic guidance. Difficulty may be experienced in negotiating a tortuous subclavian artery, especially in older individuals. Pushing the guide wire during a deep inspiration will often help it fall into the ascending aorta rather than into the descending aorta. The diagnostic catheter is also usually introduced along with the guide wire, keeping the tip of the guide wire well beyond that of the catheter. A tiger catheter can be used for angiography of both the coronaries or specific Judkins catheters can be used for each coronary artery. The tiger catheter usually reaches the non coronary sinus during initial introduction or may even jut into the left ventricle. It is gradually withdrawn so that it falls first into the left sinus and on still withdrawing, into the left coronary ostium. Slight clockwise torque may be required for proper seating of the catheter within the ostium co-axially. After obtaining the left sided injections, it is decannulated from the left coronary ostium and pushed down the aorta before withdrawing and turning it rightward to engage the right coronary ostium. If the coronary anatomy is one which requires coronary artery bypass grafting, the left subclavian artery is cannulated in the return track of the catheter by pushing it leftward when it reaches the arch of the aorta. A guide wire may have to be used to manoeuver it into the left subclavian ostium. A left subclavian injection is usually sufficient to adequately opacify the left internal mammary artery.
After trans radial angiography, it is decided to do a transradial coronary intervention, the 5F sheath may be exchanged for a 6F sheath. This is done by initially reintroducing the hydrophilic guide wire, removing the 5F sheath over it and then threading the 6F sheath over the guide wire, applying compression on the artery to avoid undue bleeding during the sheath exchange.