All practitioners delivering ionizing radiation during medical procedures must attend a radiation protection course (IRMER, Ionising Radiation Medical Exposure Regulations 2000). Furthermore, staff working in the catheterization laboratory should be issued with radiation-monitoring badges, for the body and neck, which should always be worn while in the lab. These badges should be checked monthly to assess doses of radiation received by individual members of staff. No unnecessary staff should be within the catheterization lab during a procedure, and all staff that need to be in the lab should be as far from the tube as practical.

Minimizing patient dose

• Minimize screening time and minimize acquisition time.

• Keep the distance between the X-ray tube and image intensifier to a minimum.

• Use collimation and cones to minimize the irradiated area.

• Use lower magnifications when possible.

• Use the lowest number of frames/second to allow adequate imaging.

• For prolonged procedures, the intensifier should be moved regularly, a few degrees, to try to minimize the possibility of skin burns.

Minimizing operator dose

• Lead aprons and lead collars should be worn.

• Additional screening should be used where available:

• lead apron below table.

• mobile lead screen to go between the operator and source.

• As above, minimize X-ray exposure by reducing screening and acquisition time.

• Some projections (e.g. left anterior oblique (LAO)) give much higher scatter of X-ray, and operators should be aware of this.

The dose for an interventional cardiologist has been calculated as 60 mSv (based upon 150 working days per year and 4 interventions per day). The calculated effective dose if the operator wears the correct lead apron and thyroid collar is less than 5 mSv/year. The maximum allowed dose is 20 mSv/year.

Vascular access: the femoral artery

Procedure for femoral artery access

• The standard approach for left heart catheterization is the right common femoral artery.

• The artery is located by palpating below the inguinal ligament, the ideal position for puncture being approximately 3 cm below the inguinal ligament and slightly lateral to the position of the vessel.

• The area should be anaesthetized generously with local anaesthetic (usually 10 mL of 2% or 20 ml of 1% lidocaine). Warn the patient of ‘pins and needles’ or transient numbness in the leg that may be caused by the effects of lidocaine on the femoral nerve.

• A small incision (3–5 mm) is made in the overlying skin. The tissue underlying this incision may then be dilated; commonly this is done by using curved ‘mosquito’ forceps.

• The procedure used to puncture the artery is known as the ‘Seldinger technique’. A hollow needle is introduced slowly; it is often possible to feel the pulsations of the artery via the needle before the vessel is punctured. When the needle is introduced into the vessel, pulsatile flow confirms its position in the arterial lumen. At this point a 0.035″ wire can be advanced into the vessel and towards the heart; this should be performed under fluoroscopic guidance.

• The needle is then withdrawn and a haemostatic sheath (usually 5–8 Fr diameter) is introduced over the wire; the haemostatic sheath allows the introduction of a guide wire and catheter into the femoral artery, while preventing excess bleeding from the femoral puncture site.

Sheath removal

(see Vascular access site management, p. 316)

• This can be performed immediately after diagnostic angiography, or after an interval of 4–6 hours if heparin has been administered.

• Haemostasis can be achieved by manual compression or by using a compression device (e.g. Femstop™).

• Vascular closure devices (e.g. Angioseal™ or Perclose™) allow earlier removal of sheaths in anticoagulated patients and may reduce bleeding complications.

Complications

• Femoral artery dissection

• Femoral artery pseudoaneurysm

• Distal embolization

• Haematoma

• Retroperitoneal haemorrhage/haematoma (particularly with high punctures of the femoral artery above the inguinal ligament).

Vascular access: the radial artery

The radial approach for coronary angiography is now widely accepted. There are several advantages, including a reduction in vascular complications, and the ability to mobilize patients immediately following their procedure. Patient selection for radial access should include palpation of the radial artery to confirm pulsations are present and then an Allen’s test. In the absence of robust supply via the ulnar artery, the radial approach should not be used.

Procedure for radial artery approach

• Consent patient.

• Perform Allen’s test.

• Remove all jewellery from arm, shave area, and disinfect.

• Local anaesthesia: Use 1–2 mL 2% lidocaine instilled via a 25 gauge needle (i.e. enough to anaesthetize, but not to distort the anatomy).

• The artery should be palpated with the index and middle fingers, the index finger lifted, and the artery punctured at 45 degrees. The artery should be punctured as proximally as possible, and care should be taken to avoid the flexor retinaculum.

• Once pulsatile flow is obtained, a guide wire can then be advanced through the needle and into the vessel.

• It is usual to make a small incision in the skin to allow passage of an arterial sheath. Care should be taken not to damage the radial artery while making this incision. Thus the blade should be used to incise in the longitudinal plane, rather than transversely, to reduce the risk of completely transecting the artery.

• A variety of long and short sheaths are commercially available. The advantage of long sheaths is that they minimize trauma to the radial artery.

Complications

Radial artery spasm is the commonest complication of radial artery puncture and sheath introduction. There are various techniques to try and prevent radial artery spasm from occurring, these include:

• careful patient selection, avoiding small and difficult-to-palpate radial arteries

• adequate patient sedation if required—pain provokes spasm

• the use of a ‘cocktail’ of drugs introduced directly into the radial artery. A variety of different regimens have been described. We use 1 mg isosorbide dinitrate, 2.5 mg verapamil, and 2500 U heparin made up to 10 mL with normal saline. Repeated doses of nitrates or verapamil (up to 5 mg) given directly into the sheath or in the catheter may be required

• shorter sheaths may be better tolerated

• some sheaths have a hydrophilic coating to try to reduce spasm, and for less discomfort on removal

• always use a guide wire to straighten catheters prior to removal from the aortic arch through the radial sheath.

Common radial pitfalls and solutions

• Radial loop:

• 360 degree loop in radial artery. This may be negotiated with a hydrophilic guide wire or angioplasty wire before straightening with a catheter.

• Tortuosity in proximal vessels:

• this also may be negotiated as above; manoeuvres such as breath holds and gentle ipsilateral arm traction may help.

• Recurrent radial artery:

• anatomical variant arising from the radial artery below the elbow; may be blind ending. Contrast injection may provide a useful roadmap.

• Difficulty accessing the ascending aorta:

• breathholding may help to straighten the access route.

Vascular access site management

Femoral sheath removal

Femoral sheaths should only be removed by fully trained members of staff. After diagnostic coronary angiography, when no or little heparin is given, the sheath may be removed immediately. Direct pressure should be applied just proximal to the site of the skin puncture for 5 to 10 minutes. After angioplasty, it is routine to wait for between 4 to 6 hours, an activated clotting time (ACT)<150 s suggests that the effect of systemic heparinization is wearing off, and it is acceptable for the sheath to be removed. Femoral clamps (FemoStop®, RADI Medical Systems) can be used to reduce bleeding complications in patients.

Radial sheath removal

Radial sheaths are removed immediately after both diagnostic angiograms and angioplasty, as the position of the artery renders compression more simple. Compression bands (RadiStop®, RadiMedical Systems USA, TR-Band™, Terumo). See Fig. 6.3.

Fig. 6.1 Anatomy of the inguinal canal: the femoral vein lies medial to the femoral artery. The arterial puncture should be made 73 cm below the inguinal ligament.

Fig. 6.2 Radial artery anatomy.

Fig. 6.3 TR Band™ Radial access closure device. Reproduced with permission from www.terumo.com.

Vascular closure devices

Until recently, mechanical compression was the only method for controlling bleeding from vascular access sites in the groin. Larger sheaths and the advent of the more widespread use of glycoprotein (GP) IIb/IIIa inhibitors have increased the risk of bleeding, and made homeostasis more difficult. Recently, various closure devices have been introduced; the aim of these is to increase patient comfort, and reduce puncture-related complications.

Suture-based closure devices

Perclose® (Abbot Vascular, USA): this delivers a suture to the arterial puncture site. The device is sheath-like in nature; needles are positioned above the sheath in the handle, and are deployed by a plunger. A ‘clincher’ that performs a knot-tying function completes a sliding knot.

Collagen-based closure devices

Devices that utilize a bioresorbable collagen plug that is deposited at the site of arteriotomy via a sheath; such devices include the VasoSeal® (Datascope Corp, USA) and Angio-Seal® (St Jude Medical, USA, see Fig. 6.4).

Fig. 6.4 Angioseal™ vascular closure devices.

Other mechanical closure devices

StarClose® features a Nitinol® clip that is designed to promote the primary healing process to achieve a secure closure of femoral artery access sites following diagnostic or interventional vascular procedures. This clip provides 360-degree tissue apposition for rapid healing and haemostasis.

Drug-based closure devices

Clo-Sur® PAD (Medtronic, USA): this device contains a naturally occurring biopolymer polyprolate acetate. This polymer has a coagulant property when brought into contact with heparinized blood. The device is placed over the puncture and the haemostatic sheath is removed. Direct continuous pressure is applied until haemostasis is achieved.

Radial closure device: TR Band™ (see Fig. 6.4)

How to place a TR band

• Position the spot on the TR Band™ over the radial puncture site, with the sheath in situ.

• An assistant should inflate the syringe with the minimal amount of air (usually 12–15 mL) needed to achieve haemostasis, while ensuring the radial artery remains palpable. The operator simultaneously withdraws the sheath from the radial artery.

• Add/remove additional air if needed.

• Perform regular neurovascular hand observations.

• Slowly deflate the TR Band™ over a few hours until bleeding has stopped.

Coronary angiography

Pre-shaped coronary angiographic catheters

The catheters used in diagnostic coronary angiography come in a wide variety of preformed shapes. In the UK, the most commonly used pre-shaped catheters are the Judkins Left 4 and Judkins Right 4 (known as the JL4 and JR4 respectively), used to image the left and right coronary arteries, and the pigtail catheter, used for left ventriculography. The diameter of catheters is measured in French gauge (Fr); catheters between 4Fr (0.053″) and 8 Fr (0.105″) are commonly used.

Commonly used cardiac catheter shapes

See Fig. 6.5.

Fig. 6.5 Commonly used cardiac catheter shapes.

Catheter advancement and manifold usage

A ‘J’-tipped 0.035″ guide wire is placed within the flushed catheter, which is then passed into the haemostatic sheath. The guide wire is advanced ahead of the catheter under fluoroscopic guidance, until it reaches the aortic root, just above the aortic valve. The catheter is then advanced to this position and the guide wire is removed. To ensure that no air or clot is within the catheter, a small volume of blood (5 mL) is aspirated from the catheter directly into a syringe and discarded. The catheter is then carefully connected to a two-way manifold, which allows pressure monitoring, saline flushing, and contrast injection through a closed system.

Contrast injection

Great care must be taken at all times to ensure that air is not injected into the coronary arterial tree. The injection syringe should be filled with contrast from the reservoir, and then the syringe held with the plunger elevated so that any air bubbles rise to the top of the syringe. Contrast should then be injected at a continuous rate, aiming to full opacify the coronary vessel of interest. Care should be taken that the pressure trace is normal before injection—damping suggests an ostial stenosis, excessively deep intubation, or selective intubation of a branch.

Coronary angiography/left ventriculography

Interpreting the coronary angiogram

Left coronary artery (LCA) angiographic views (Fig. 6.6)

Fig. 6.6 LCA angiographic views. Reproduced with permission from Braunwald E (ed) (2001). Heart Disease: a textbook of cardiovascular medicine. 5th ed. Philadelphia: WB Saunders.

Right coronary artery (RCA) angiographic views (Fig. 6.7)

Fig. 6.7 RCA angiographic views. Reproduced with permission from Braunwald E (ed) (2001). Heart Disease: a textbook of cardiovascular medicine. 5th ed. Philadelphia: WB Saunders.

Angiographic study of grafts

It is important to study the surgical record to ascertain how many grafts were placed at the time of the operation. Sometimes, useful information (often from a surgeon’s diagram) can be obtained as to the position in the ascending aorta that the grafts arise from. As a rule, leftwards-facing grafts are best cannulated from the RAO 50 projection, and rightwards-pointing grafts are best cannulated in the LAO 50 projection. It may be necessary to perform an aortogram to visualize the position of grafts. Specialist catheters (e.g. the left coronary bypass catheter or LCB) have been designed to aid cannulation of grafts.

There is usually a predictable anatomy:

• patent ductus arteriosus (PDA) grafts originate from the right anterior aspect of the aorta and run vertically to the inferior surface of the heart

• obtuse marginal (OM) grafts originate from the left anterior aspect of the aorta and arc towards the posterolateral surface of the heart

• left anterior descending (LAD) and diagonal grafts originate from an intermediate position and run laterally towards the anterior interventricular groove.

• arterial grafts improve patency rates in coronary artery bypass graft (CABG) and are preferred in contemporary surgery. Left internal mammary artery (LIMA) grafts are usually accessed via the femoral route, but may also be accessed via the left radial approach. Right internal mammary artery (RIMA) grafts are less often used, and can be approached via either the femoral or right radial route.

• the left subclavian artery is accessed using a standard JR or multipurpose catheter. Care must be taken when advancing catheters up the subclavian artery. A JR catheter may engage the LIMA directly or may need to be exchanged over a long wire for an internal mammary artery catheter.

• small contrast injections may be needed to identify the LIMA ostium.

• coronary injections should be acquired in different orthogonal planes to adequately visualize the LIMA and its subtended territory, particularly the point of insertion.

• the patient should be warned that they will feel a warm flushing feeling in their arm and neck.

• the catheter should be disengaged under fluoroscopic screening and carefully removed over a wire.

Common aortic positions for placement of saphenous vein graft (SVG) (Fig. 6.8)

Fig. 6.8 Common aortic positions for placement of SVG. OVG = omniflow vascular graft. Reproduced with permission from Braunwald E (ed) (2001). Heart Disease: a textbook of cardiovascular medicine. 5th ed. Philadelphia: WB Saunders.

Complications of angiography

Peripheral vascular complications

Haematoma

The incidence of haematoma formation is related to the following factors:

• length of time the sheath is left in place

• gauge (size) of the sheath

• anticoagulation

• risk factors, e.g. hypertension, obesity, and pre-existing peripheral vascular disease

• technique of sheath removal.

Features that suggest a haematoma may require further investigation are an overlying bruit, expansile mass, and a large tense swelling.

Pseudoaneurysm (Fig. 6.9)

A pseudoaneurysm represents a rupture of the femoral arterial wall at the site of puncture, with the formation of a false aneurysm involving the media and adventitia. It is best visualized on ultrasound examination. Small pseudoaneurysms can often be managed by direct compression; however, large pseudoaneurysms may require thrombin injection, or surgical intervention.

Fig. 6.9 Anatomy of a pseudoaneurysm. (a) Bleeding along a small tract allows blood to collect within the extravascular tissues. Manual compression fails to obliterate the tract (b), and allows the haematoma to persist. Failure of thrombosis of the haematoma produces an extravascular collection with persistent connection and flow from the main artery (c). This can be visualized on ultrasound scan (USS).

Haemorrhage

If prolonged, then direct pressure (either manually or using a clamping device) may be needed. Heparin anticoagulation can be reversed using protamine.

Limb ischaemia

This is rare, and usually occurs in patients with pre-existing limb ischaemia. If limb ischaemia is suspected, then urgent review by the vascular surgical team should be sought.

Contrast reactions

Mild contrast reactions such as rash, urticaria, blurred vision, and rigors are relatively common. These symptoms may settle spontaneously, but are often treated with a combination of IV chlorphenamine 10 mg and IV hydrocortisone 100–200 mg. Anaphylactic reactions are rare; these should be treated with chlorphenamine and hydrocortisone, but also plasma expanders and IM adrenaline.

Vasovagal reactions

These are common both during angiography and at the time of sheath removal, and characterized by hypotension and bradycardia. They are treated with IV atropine and volume expanders.

Arrhythmia

Brief episodes of supraventicular tachycardia (SVT) are common and often transient. During catheter manipulation (especially in the left ventricle (LV)), salvoes of VT are common. Ventricular fibrillation (VF) may occur during coronary artery injection, and should be treated with rapid defibrillation.

Radial arterial complications

One of the main advantages of the radial route is a reduction in complication rates.

Bleeding

This is more easily managed with direct pressure than from the femoral route.

Compartment syndrome

This is a rare, but potentially catastrophic complication.

Pseudoaneurysm

Rare. Manage as per femoral pseudoaneurysm.

Radial artery occlusion

The rate of radial artery occlusion following radial artery cannulation is unclear—but is probably between 1% and 5%. The rate of occlusion is reduced with smaller sheath sizes, hydrophilic sheaths, and heparin administration.

Right-heart catheterization

Indications for right-heart catheterization include:

• evaluation of cardiac shunts

• evaluation of valvular heart disease

• dyspnoea not explained by non-invasive investigation

• investigation for pulmonary hypertension

• work-up for cardiac transplantation

• investigation for pulmonary hypertension and transplantation should only be performed in specialist centres.

The acute settings in which right heart catheterization can be helpful (e.g. intensive drug therapy in cardiogenic shock) will not be discussed here.

Access to the right heart is usually achieved via the right femoral vein (RFV). The RFV is located 0.5 cm to 1 cm medial to the femoral arterial pulsation (see Vascular access: the femoral artery, Fig. 6.1, p. 313). An 18-gauge needle, attached to a syringe that is partially filled with saline, can be used to locate the position of the vein, followed by the larger-bore needle. When venous blood is freely aspirated, a 0.035″ guide wire is passed into the vein, using a technique similar to femoral artery cannulation, and a haemostatic sheath introduced.

Right-heart catheterization protocol

• A ‘multipurpose’ catheter or balloon-tipped catheter may be used.

• Ensure that the catheter is flushed, and that the transducer is correctly zeroed.

• Advance the catheter to the inferior vena cava (IVC), and further to the right atrium. Record the phasic and mean pressures.

• It is customary to then advance the catheter to the pulmonary artery wedge position. Advance into the RV. A combination of rotation of the catheter and gentle traction will allow the catheter to flick upwards into the right ventricular outflow tract (RVOT). It can then be advanced into the main pulmonary artery (PA) and out to the periphery. Occasionally, the guide wire is necessary to achieve this.

• Advance the catheter to the pulmonary capillary wedge position, and record phasic and mean pressures.

• With a pigtail catheter in the LV, measure and record the LV pressures. Record simultaneous pulmonary capillary wedge pressure (PCWP) and LV pressure, ensuring that the scale allows interpretation of the end-diastolic pressures with accuracy (to assess for mitral valve (MV) gradient).

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Tags: Oxford Handbook of Cardiology

Mar 4, 2017 | Posted by admin in CARDIOLOGY | Comments Off

Fastest Thoracic Insight Engine

Cardiac catheterization and intervention

Minimizing patient dose

Minimizing operator dose

Procedure for femoral artery access

Sheath removal

Complications

Procedure for radial artery approach

Complications

Femoral sheath removal

Radial sheath removal

Vascular closure devices

Suture-based closure devices

Collagen-based closure devices

Other mechanical closure devices

Drug-based closure devices

Radial closure device: TR Band™ (see Fig. 6.4)

How to place a TR band

Pre-shaped coronary angiographic catheters

Commonly used cardiac catheter shapes

Catheter advancement and manifold usage

Contrast injection

Left coronary artery

Right coronary artery

Left ventriculography

Left coronary artery (LCA) angiographic views (Fig. 6.6)

Right coronary artery (RCA) angiographic views (Fig. 6.7)

Common aortic positions for placement of saphenous vein graft (SVG) (Fig. 6.8)

Peripheral vascular complications

Haematoma

Pseudoaneurysm (Fig. 6.9)

Haemorrhage

Limb ischaemia

Contrast reactions

Vasovagal reactions

Arrhythmia

Bleeding

Compartment syndrome

Pseudoaneurysm

Radial artery occlusion

Right-heart catheterization protocol

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