Historically, \200\230candidate gene \200\231 studies have been used in an attempt to iden tify risk factor genes for CAD; candidate genes are selected based on their role within one of the physiological pathways responsible for atherosclerosis. One of the genes most succe ssfully identi \201 ed from such studies is apolipoprotein E, of which there are 3 alleles : APOE2 , APOE3 , and APOE4 . APOE3 is the most common allele in European populations; the APOE2 and APOE4 alleles are associated with reduced and elevated plasma LDL-C respectively. A meta-analysis of 121 studies in which coronary outcomes were evaluated showed an odds ra tio for CAD of 0.80 in carriers of the APOE2 allele, and 1.06 in carriers of the APOE4 alle le, compared to individuals who were homozygous for APOE3 . 1 Individuals carrying the APOE 4 allele and who also smoke may show a particularly elevated risk for CAD, 2 although this remains controversial. Additional genes that have been implicated include those for lipoprotein lipase, thrombospo ndin, prothrombin, endothelial nitric oxide synthase (eNOS), myocyte enhancer factor 2A (ME F2A), and 5-lipoxygenase activation protein (FLAP). However, inconsistent results have been obtained for a number of these genes. More recently, following sequencing of the human gen ome, a number of independent genome-wide association studies have identi \201 ed a single locus on chromosome 9p21 as being associated with an increased risk of CAD 3 . A cluster of genes involved in control of the cell cycle have been identi \201 ed in this region; sinc e cellular proliferation is an essential step in the development of the atherosclerotic pla que, this may provide a mechanism for the role of this locus in the development of CAD. 1 Bennet AM, Di Angelantonio E, Ye Z, et al. (2007). Association of apolipoprotein E genoty pes with lipid levels and coronary risk. JAMA 298 : 1300 \200\22311. 2 Humphries SE, Talmud PJ, Hawe E, Bolla M, Day IN, Miller GJ (2001). Apolipoprotein E4 and coronary heart diseas e in middle-aged men who smoke: a prospective study. Lancet . 358 : 115 \200\22319. 3 McPhe rson R, Pertsemlidis A, Kavaslar N, et al. (2007). A common allele on chromosome 9 associat ed with coronary heart disease. Science 316 : 1488 \200\22391. GENETIC TESTING FOR CORONARY ARTERY DISEASE 307 Genetic testing for coronary artery disease In patients where a monogenic cause of CAD is d iagnosed on clinical assessment, it is desirable to perform genetic testing to identify the mutation(s) responsible and allow relatives to be screened. A number of methods are now av ailable for identifying the mutations responsible for causing FH, and the current NICE guid elines recommend that genetic testing is offered to all patients with a clinical diagnosis of FH; current methods can detect the FH-causing mutation in 70 \200\22380 % of patients wi th a de \201 nite diagnosis of FH based on the Simon Broome criteria. Unfortunately, the a vailable techniques are not 100 % sensitive; therefore the absence of an identi \201 ed mu tation does not exclude a diagnosis of FH. Once a mutation is identi \201 ed, NICE guideli nes recommend cascade testing for the mutation in 1st-, 2nd-, and, if possible, 3rd-degree relatives. Appropriate primary prevention with cholesterol-lowering drugs can then be insti tuted to reduce the risk of CAD; this results in a 48 % reduction in coronary heart disease mortality. 1 Unfortunately, genetic testing is not yet available for the majority of patients, in whom C AD results from the interactions between polygenic susceptibility and a high-risk environme nt. However, evidence suggests that those patients who carry (cid:2) 7 \200\230risk \200 \231 alleles (from a group of 10 identi \201 ed candidate genes) have an increased odds ra tio (4.51) for CAD when compared to those carrying 3 \200\2234 \200\230risk \200\231 allel es. 2 Any future genetic test for such patients will need to incorporate a number of polymo rphisms in a range of genes, and be assessed in the context of environmental risk factors, if it is to be used for clinical risk strati \201 cation. 1 Neil A, Cooper J, Betteridge J, et al. (2008). Reductions in all-cause, cancer, and coron ary mor- tality in statin-treated patients with heterozygous familial hypercholesterolaemia : a prospective registry study. Eur Heart J 29 : 2625 \200\22333. 2 Drenos F, Whittaker JC, Humphries SE (2007). The use of meta analysis risk estimates for candi- date genes in comb ination to predict coronary heart disease risk. Ann Hum Genet 71 : 611 \200\22319. This page intentionally left blank 309 Chapter 6 Cardiac catheterization and intervention Radiation protection in the catheterization laboratory 310 Vascular access: the femoral art ery 312 Vascular access: the radial artery 314 Vascular access site management 316 Coronary angiography 318 Interpreting the coronary angiogram 320 Angiographic study of grafts 322 C omplications of angiography 324 Right-heart catheterization 326 Cardiac output and left ven tricular function 328 Cardiac catheterization in valve disease 329 Intravascular ultrasound 330 Angioplasty and coronary stenting 332 Restenosis following percutaneous transluminal coronary angioplasty (PTCA) 334 Drug-eluting stents 336 Stent thrombosis 338 Physiological assessment of coronary \202 ow 340 Primary angioplasty for STEMI 342 Primary angioplasty: procedure 344 Invasive assessme nt of vulnerable plaque 346 Complex coronary angioplasty 348 Angioplasty in multivessel dis ease 354 SYNTAX score 355 Left main stem angioplasty 356 Adjunctive therapy for angioplasty and stenting 358 Embolic protection devices 360 Special techniques 362 Mitral valvuloplast y 364 310 CHAPTER 6 Cardiac catheterization & intervention Radiation protection in the catheterization laboratory All practitioners delivering ionizin g radiation during medical procedures must attend a radiation protection course (IRMER, Ion izing Radiation Medical Exposure Regulations 2000). Furthermore, staff working in the cathe terization laboratory should be issued with radiation-monitoring badges, for the body and n eck, which should always be worn while in the lab. These badges should be checked monthly t o assess doses of radiation received by individual members of staff. No unnecessary staff s hould be within the catheterization lab during a procedure, and all staff that need to be i n the lab should be as far from the tube as practical. Minimizing patient dose \200 Minimize screening time and minimize acquisition time. \200 Keep the distance between the X-ray tube and image intensi \201 er to a minimum. Use collimation and cones to minimize the irradiated area. \200 Use lower magni \201 cat ions when possible. \200 Use the lowest number of frames/second to allow adequate imaging . \200 For prolonged procedures, the intensi \201 er should be moved regularly, a few degrees, to try to minimize the possibility of skin burns. Minimizing operator dose \200 Lead aprons and lead collars should be worn. \200 Additio nal screening should be used where available: lead apron below table. \200 mobile lead screen to go between the operator and source. \200 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 w orking days per year and 4 interventions per day). The calculated effective dose if the ope rator wears the correct lead apron and thyroid collar is less than 5 mSv/year. The maximum allowed dose is 20 mSv/year. This page intentionally left blank 312 CHAPTER 6 Cardiac catheterization & intervention Vascular access: the femoral artery Procedure for femoral artery access \200 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 punc ture being approximately 3 cm below the inguinal ligament and slightly lateral to the posit ion of the vessel. The area should be anesthetized generously with local anesthetic (usually 10 mL of 2 % or 2 0 ml of 1 % lidocaine). Warn the patient of \200\230pins and needles \200\231 or transient numbness in the leg that may be caused by the effects of lidocaine on the femoral nerve. A small incision (3 \200\2235 mm) is made in the overlying skin. The tissue underlying this incision may then be dilated; commonly this is done by using curved \200 \230mosquito \200\231 forceps. The procedure used to puncture the artery is known as the \200\230Seldinger technique \200 \231. 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 int o the vessel, pulsatile \202 ow con \201 rms 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 \202 uoroscopic guidance. The needle is then withdrawn and a haemostatic sheath (usually 5 \200\2238 Fr diameter) is introduced over the wire; the haemostatic sheath allows the introduction of a guide wire an d catheter into the femoral artery, while preventing excess bleeding from the femoral punct ure site. Sheath removal (see b Vascular access site management, p. 316) \200 This can be performed immediately after diagnostic angiography, or after an interval of 4 \200\2236 hours if hep arin has been administered. \200 Haemostasis can be achieved by manual compression or by using a compression device (e.g. Femstop \204 ). Vascular closure devices (e.g. Angioseal \204 or Perclose \204 ) allow earlier removal of sheaths in anticoagulated patients and may reduce bleeding complications. Complications \200 Femoral artery dissection \200 Femoral artery pseudoaneurysm \200 Distal embolization \200 Haematoma \200 Retroperitoneal hemorrhage/haematoma (particula rly with high punctures of the femoral artery above the inguinal ligament). VASCULAR ACCESS: THE FEMORAL ARTERY 313 Anterior spine Inguinal ligament Skin crease 3 cm Common femoral artery Profunda Saphenous vein Superficial femoral artery Femoral vein 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. 314 CHAPTER 6 Cardiac catheterization & intervention Vascular access: the radial artery The radial approach for coronary angiography is now wide ly accepted. There are several advantages, including a reduction in vascular compli- cation s, and the ability to mobilize patients immediately following their procedure. Patient sele ction for radial access should include palpation of the radial artery to con \201 rm pulsa tions are present and then an Allen \200\231s test. In the absence of robust supply via the ulnar artery, the radial approach should not be used. Procedure for radial artery approach \200 Consent patient. \200 Perform Allen \200\231s test. \200 Remove all jewelry from arm, shave area, and disinfect. \200 Local anesthes ia: Use 1 \200\2232 mL 2 % lidocaine instilled via a 25 gauge needle (i.e. enough to anesthetize, but not to distort the anatomy). \200 The artery shou ld be palpated with the index and middle \201 ngers, the index \201 nger lifted, and th e artery punctured at 45 degrees. The artery should be punctured as proximally as possible, and care should be taken to avoid the \202 exor retinaculum. Once pulsatile \202 ow 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 inc ision. Thus the blade should be used to incise in the longitudinal plane, rather than trans versely, to reduce the risk of completely transecting the artery. A variety of long and short sheaths are commercially available. The advantage of long sheat hs is that they minimize trauma to the radial artery. Complications Radial artery spasm is the commonest complication of radial artery punc- ture and sheath introduction. There are various techniques to try and prevent radial artery spa sm from occurring, these include: \200 careful patient selection, avoiding small and dif \201 cult-to-palpate radial arteries adequate patient sedation if required \200\224 pain provokes spasm \200 the use of a \200\230cocktail \200\231 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 ver apamil (up to 5 mg) given directly into the sheath or in the catheter may be required shorter sheaths may be better tolerated \200 some sheaths have a hydrophilic coating to t ry 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. VASCULAR ACCESS: THE RADIAL ARTERY 315 Thenar muscles Branch of radial artery completing the superficial palmar arch Abductor pollicis longus Radial artery Radius Flexor carpi radialis Fig. 6.2 Radial artery anatomy. Common radial pitfalls and solutions \200 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; maneuvers 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. Dif \201 culty accessing the ascending aorta: breathholding may help to straighten the access route. 316 CHAPTER 6 Cardiac catheterization & intervention Vascular access site management Femoral sheath removal Femoral sheaths should only be remov ed by fully trained members of staff. After diagnostic coronary angiography, when no or lit tle heparin is given, the sheath may be removed immediately. Direct pressure should be appl ied 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 clot- ting time (ACT)<150 s su ggests 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 t o reduce bleeding complications in patients. Radial sheath removal Radial sheaths are removed immediately after both diagnostic angiogra ms and angioplasty, as the position of the artery renders compression more simple. Compress ion bands (RadiStop , RadiMedical Systems USA, TR-Band \204 , Terumo). See Fig. 6.3 . Vascular closure devices Until recently, mechanical compression was the only method for con trol- ling 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 dif \201 cult. Recently, various closure devices h ave been introduced; the aim of these is to increase patient comfort, and reduce puncture-r elated complications. Suture-based closure devices Perclose (Abbot Vascular, USA): this delivers a suture to t he arterial puncture site. The device is sheath-like in nature; needles are positioned abov e the sheath in the handle, and are deployed by a plunger. A \200\230clincher \200\231 tha t performs a knot-tying function completes a sliding knot. Collagen-based closure devices Devices that utilize a bioresorbable collagen plug that is d eposited at the site of arteriotomy via a sheath; such devices include the VasoSeal (Dat ascope Corp, USA) and Angio-Seal (St Jude Medical, USA, see Fig. 6.4 ). Other mechanical closure devices StarClose features a Nitinol clip that is designed t o 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-de gree tissue apposition for rapid healing and haemostasis. Drug-based closure devices Clo-Sur PAD (Medtronic, USA): this device contains a naturall y occur- ring biopolymer polyprolate acetate. This polymer has a coagulant prop- erty 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. VASCULAR ACCESS SITE MANAGEMENT 317 Fig. 6.3 TR Band \204 Radial access closure device. Reproduced with permission from Y www .terumo.com. Radial closure device: TR Band \204 (see Fig. 6.4 ) How to place a TR band \200 Positio n the spot on the TR Band \204 over the radial puncture site, with the sheath in situ . An assistant should in \202 ate the syringe with the minimal amount of air (usually 12 \200\22315 mL) needed to achieve haemostasis, while ensuring the radial artery remains palp able. The operator simultaneously withdraws the sheath from the radial artery. \200 Add/r emove additional air if needed. \200 Perform regular neurovascular hand observations. \200 Slowly de \202 ate the TR Band \204 over a few hours until bleeding has stopped. Fig. 6.4 Angioseal \204 vascular closure devices. 318 CHAPTER 6 Cardiac catheterization & intervention Coronary angiography Pre-shaped coronary angiographic catheters The catheters used in diagn ostic 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 th e JL4 and JR4 respectively), used to image the left and right coronary arteries, and the pi gtail catheter, used for left ventriculography. The diam- eter 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 . AR I AR II AR III AR Mon AL I AL II AL III LRA 1 JR 4 JR5 JR 5 JL4 JL 45 JR 5 JR 6 JR 35 JL 35 LCB SONI SCNII SONIII CASI CASII CASIII MPA2 MPB1 SX PG PG PG MPA2 MPB2 PG Flow-directed balloon catheters ULM Cardiac multipacks NH PG MPA 2 JR4 RC8 C8 M JL4 Fig. 6.5 Commonly used cardiac catheter shapes. Catheter advancement and manifold usage A \200\230J \200\231-tipped 0.035" guide wire is p laced within the \202 ushed catheter, which is then passed into the haemostatic sheath. T he guide wire is advanced ahead of the catheter under \202 uoroscopic 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 cathet er, a small volume of blood (5 mL) is aspirated from the catheter directly into a syringe a nd discarded. The catheter is then carefully connected to a two-way manifold, which allows pressure moni- toring, saline \202 ushing, 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 \201 lled with contrast from the reservoir, and then the syringe held with the plunger elevated so that any air bu bbles rise to the top of the syringe. Contrast should then be injected at a continuous rate , aiming to full opacify the cor- onary vessel of interest. Care should be taken that the p ressure trace is normal before injection \200\224 damping suggests an ostial stenosis, exc essively deep intubation, or selective intubation of a branch. CORONARY ANGIOGRAPHY 319 Coronary angiography/left ventriculography Left coronary artery \200 The 50 left anterior oblique (LAO 50) is the best projection for cannulation of both the left and right coronary ostia. In reality however, the left coronary ostium is often cannulated with the tower in the anteroposterior (AP) position. The JL4 catheter will almost invariably cannulate the left coronary ostium without manipulation. In patients with large aortic roots (large, hypertensive patients), the JL5 (with a larger curve) may be needed, and, conversely, a smaller root may need a smaller catheter curve, th e JL3.5. Right coronary artery \200 The LAO 50 projection is best used for cannulation of the righ t coronary ostium. The JR4 catheter is introduced to the aortic root, until it lies 1 \200\2232 cm above the aortic valve. The catheter is then rotated ( \200\230torqued \200\231) in a clockwise direction, such tha t the catheter tip rotates towards the right coronary ostium. It may be necessary to reduce the torque to prevent the catheter from over-shooting. There is often a noticeable lateral movement as the catheter enters the artery. Before contrast is injected, it must be ensured that the pressure tracing transduced from t he tip of the catheter is not damped. \200 NB: damping can suggest that the catheter has selectively intubated the conus branch of the right coronary artery, and injection of contr ast into this vessel can induce ventricular arrhythmias. Left ventriculography \200 Position a pigtail catheter a few centimeters above the aortic valve and pull the wire back 5 \200\22310 cm to make the catheter tip soft, and push gentl y (the catheter may cross at this point). If the catheter does not cross, apply torque as it is gently withdrawn. \200 If this tech nique is not successful, use a straight soft-tipped guide wire and catheters that allow tha t guide wire to be \200\230pointed \200\231 at the valve (e.g. AL1 or JR4). This may impro ve the chances of crossing the valve. Once the catheter has been placed in a stable (free of ectopics) position in the mid-LV cavity, connect to the manifold and measure the pressure. Disconnect the manifold catheter connected to a power injector and expel all air. Set the injection rate: typically 25 \200\22330 mL of contrast at a rate of 10 mL/s. Warn the patient about hot \202 ush and the feeling of extra systoles. When the left ventriculogram has been performed, the catheter is reconnected to the manifold to allow pressure recording as the catheter is withdrawn acr oss the aortic valve (the pullback pressure). 320 CHAPTER 6 Cardiac catheterization & intervention Interpreting the coronary angiogram Left coronary artery (LCA) angiographic views (Fig. 6.6 ) LCx LAO cranial LMCA OMB S D LAD LCx LAO caudal LAD LMCA AP caudal LCx LAD LCx AP cranial LMCA S LAD LCx RAO cranial S LAD RAO caudal LAD LCx OMB Fig. 6.6 LCA angiographic views. Reproduced with permission from Braunwald E (ed) (2001). H eart Disease: a textbook of cardiovascular medicine . 5th ed. Philadelphia: WB Saunders. INTERPRETING THE CORONARY ANGIOGRAM 321 Right coronary artery (RCA) angiographic views (Fig. 6.7 ) RCA LAO straight PLV AMB PDA LAO cranial RCA PLV AMB PDA Conus branch RAO straight RCA PDA Fig. 6.7 RCA angiographic views. Reproduced with permission from Braunwald E (ed) (2001). H eart Disease: a textbook of cardiovascular medicine . 5th ed. Philadelphia: WB Saunders. 322 CHAPTER 6 Cardiac catheterization & intervention 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 \200\231s 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 th e RAO 50 projection, and rightwards-pointing grafts are best cannulated in the LAO 50 proje ction. It may be necessary to perform an aortogram to visualize the position of grafts. Spe cialist cath- eters (e.g. the left coronary bypass catheter or LCB) have been designed to a id 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 to wards the posterolateral surface of the heart \200 left anterior descending (LAD) and dia gonal 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 prefer red in contemporary surgery. Left internal mammary artery (LIMA) grafts are usually accesse d via the femoral route, but may also be accessed via the left radial approach. Right inter nal mammary artery (RIMA) grafts are less often used, and can be approached via either the femoral or right radial route. \200 the left subclavian artery is accessed using a standa rd 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 f or an internal mammary artery catheter. small contrast injections may be needed to identify the LIMA ostium. \200 coronary inject ions 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 \202 ushing feeling in their arm and neck. the catheter should be disengaged under \202 uoroscopic screening and carefully removed over a wire. ANGIOGRAPHIC STUDY OF GRAFTS 323 Common aortic positions for placement of saphenous vein graft (SVG) (Fig. 6.8 ) SVG-OVG SVG-LAD SVG-PDA LCA RCA Fig. 6.8 Common aortic positions for placement of SVG. OVG = omni \202 ow vascular graft. Reproduced with permission from Braunwald E (ed) (2001). Heart Disease: a textbook of cardi ovascular medicine . 5th ed. Philadelphia: WB Saunders. 324 CHAPTER 6 Cardiac catheterization & intervention Complications of angiography Peripheral vascular complications Haematoma The incidence of h aematoma formation is related to the following factors: \200 length of time the sheath is left in place \200 gauge (size) of the sheath \200 anticoagulation \200 risk factors , e.g. hypertension, obesity, and pre-existing peripheral vascular disease technique of sheath removal. Features that suggest a haematoma may require further investig ation are an overlying bruit, expansile mass, and a large tense swelling. Pseudoaneurysm (F ig. 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 d irect compression; however, large pseudoaneurysms may require thrombin injection, or surgic al intervention. Hemorrhage 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 ischaemi a. 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 rig ors are relatively common. These symptoms may settle spontaneously, but are often treated w ith a combination of IV chlorphenamine 10 mg and IV hydrocortisone 100 \200\223200 mg. Anap hylactic 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 remo val, and characterized by hypotension and bradycardia. They are treated with IV atropine an d volume expanders. Arrhythmia Brief episodes of supraventicular tachycardia (SVT) are common and often transie nt. During catheter manipulation (especially in the left ven- tricle (LV)), salvoes of VT a re common. Ventricular \201 brillation (VF) may occur during coronary artery injection, a nd should be treated with rapid de \201 brillation. COMPLICATIONS OF ANGIOGRAPHY 325 (a) Common femoral artery Pseudoaneurysm Tract Superficial femoral artery Femoral head Profunda femoral artery (c) (b) Pressure device Haematoma Pseudoaneurysm Fig. 6.9 Anatomy of a pseudoaneurysm. (a) Bleeding along a small tract allows blood to coll ect 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 ex travascular collection with persistent connection and \202 ow from the main artery (c). T his can be visualized on ultrasound scan (USS). 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 cannula tion is unclear \200\224 but is probably between 1 % and 5 % . The rate of occlusion is re duced with smaller sheath sizes, hydrophilic sheaths, and heparin administration. 326 CHAPTER 6 Cardiac catheterization & intervention Right-heart catheterization Indications for right-heart catheterization include: \200 eva luation of cardiac shunts \200 evaluation of valvular heart disease \200 dyspnoea not e xplained by non-invasive investigation \200 investigation for pulmonary hypertension \200 work-up for cardiac transplantation investigation for pulmonary hypertension and transplantation should only be performed in specialist centers. 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 b Vascular access: the femoral artery, Fig. 6.1 , p. 313). An 18-gauge needle, attached to a syringe that is part ially \201 lled 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 pass ed into the vein, using a technique similar to femoral artery cannulation, and a haemostati c sheath introduced. Right-heart catheterization protocol \200 A \200\230multipurpose \200\231 catheter or ba lloon-tipped catheter may be used. \200 Ensure that the catheter is \202 ushed, and tha t 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. Advanc e into the RV. A combination of rotation of the catheter and gentle traction will allow the catheter to \202 ick upwards into the right ventricular out \202 ow tract (RVOT). It ca n then be advanced into the main pulmonary artery (PA) and out to the periphery. Occasional ly, the guide wire is necessary to achieve this. \200 Advance the catheter to the pulmona ry capillary wedge position, and record phasic and mean pressures. With a pigtail catheter in the LV, measure and record the LV pressures. Record simultanous pulmonary capillary wedge pressure (PCWP) and LV pressure, ensuring that the scale allows i nterpretation of the end-diastolic pressures with accuracy (to assess for mitral valve (MV) gradient). Withdraw the wedge catheter slightly and record pulmonary artery phasic and mean pressure. Obtain oxygen saturations from the main PA (also right and left pulmonary arteries (RPA and LPA) if a PDA is suspected). Withdraw the pulmonary catheter to the right ventricle (RV). Measure and record simultanous RV and LV pressures. Withdraw the catheter to the RA and measure the pressures again. RIGHT-HEART CATHETERIZATION 327 The LV catheter should be pulled back to the ascending aorta while the pressure is being mo nitored to record any pull-back gradient. Aortic saturations should be measured to allow ca lculation of cardiac output (see Fig. 6.10 ) and to compare with saturations from the right side if a shunt is suspected. For shunts, a full saturation run should be performed (superior vena cava (SVC); high, mid, and low right atrium (RA), IVC, RV; main, right, and left pulmonary artery (MPA, RPA, LPA) ; etc.). Right ventricle Right atrium Pulmonary artery Pulmonary capillary wedge x v y a 30 20 10 0 a c x v y a ) g H m m ( Left atrium Left ventricle Aorta e r u s s e r P 150 100 50 0 a x v y a c Fig. 6.10 Cardiac catheterization \200\224 normal pressure waveforms. 328 CHAPTER 6 Cardiac catheterization & intervention Cardiac output and left ventricular function Cardiac output is most often measured using th e thermodilution method with a pulmonary \202 otation catheter. Cardiac output can also be measured using the Fick principle, which assesses the difference between the pulmonary arterial and aortic O 2 saturation. ( ) mL min )) \227Hb \2271.34 oxygen consumption PA SaO Ao SaO PA SaO ( L min = ) Cardiac output ( 2 2 Where Ao = aorta; Hb = hemoglobin; PA = pulmonary artery; SaO 2 = arterial oxygen saturatio n. Systemic and pulmonary vascular resistance Pulmonary vascular resistance (PVR) is an import ant prognostic factor in patients with valvular heart disease, heart failure, and cor pulmo nale. The measurement of PVR and systemic vascular resistance (SVR) is especially important in patients being assessed for cardiac transplantation. PVR and SVR are measured in Woods units (mmHg/L/min) or dynes/cm 5 , with 80 dynes/cm 5 = 1 Woods unit. \210\222 mean aortic pressure mean right atrial pressure stemic vascular resistance = Cardiac output sy \210\222 mean PA pressure mean left atrial pressure = Cardiac output pulmona ryrr vascular resistance CARDIAC CATHETERIZATION IN VALVE DISEASE 329 Cardiac catheterization in valve disease Valve stenosis Several parameters can be assessed during cardiac catheterization. \200 Peak-to-peak gradient : aortic and LV pressures are recorded during withdrawal of the pigtail catheter across the aortic valve. The gradient is the difference between peak aortic and peak LV pressure. \200 Peak instantaneous gradient : more accurat e and measured using a double-lumen pigtail catheter. Mean gradient : the mean pressure gradient measured using planimetry of the area by aortic and LV pressure traces. This can be used to calculate the valve area using the Gorlin equation, and a similar method can be used to assess the mitral valve area . 50 40 30 g H m m LV 20 LA x y 10 0 Fig. 6.11 Simultanous LV and PCWP tracing in mitral stenosis. Reproduced with permission fr om Braunwald E (ed) (2001). Heart Disease: a textbook of cardiovascular medicine , 5th ed. Philadelphia: WB Saunders. Valve regurgitation \200 The severity of aortic regurgitation can be estimated by perform ing an aortogram. In severe aortic regurgitation, the LV is seen to opacify within one or two b eats after contrast injection. Mitral regurgitation may be assessed by left ventriculography, with contrast seen to opacify the left atrium and pulmonary veins in severe regurgitation. In ad dition, mitral regurgitation (MR) may be associated with a prominent \200\230v \200\231 wa ve in the pulmonary capillary wedge tracing. 330 CHAPTER 6 Cardiac catheterization & intervention Intravascular ultrasound ( Figs. 6.12 and 6.13 ) Intravascular ultrasonography (IVUS) is a technology that allows direct visualization of atherosclerotic plaque and the vessel lumen, with recent advances allowing the echogenic characteristics of an IVUS image to give insig hts into the underlying histology. Ultrasound images are produced by passing an electrical current through a piezoelectric crystal that expands and contracts to produce sound waves w hen electrically stimulated. These sound waves are re \202 ected from tissues, and return to the transducer, where they are detected and converted to an electrical impulse that can be presented graphically. A phased array of crystals (usually 64) is used, and these are se quentially activated to produce circumferential imaging. The equipment required to perform an IVUS examination involves a mini- aturized ultrasound transducer mounted on a catheter ( usually 2.6 \200\2233.5 Fr gauge), and computer interface that carries out image reconstruc tion. Examination technique \200 Intracoronary isosorbide dinitrate and IV heparin should be administered. The IVUS catheter should be carefully advanced distal to the area of interest. A motorized pullback device is then used to draw the IVUS catheter proximally at a \201 xed speed. Landmarks such as side branches can be useful, and positions may also be recorded angiographically. Advantages of ultrasound \200 The full circumference of the vessel wall is seen, not just two surfaces as in angiography, and is thus the method of choice to determine vessel luminal area. It is useful in imaging ambiguous lesions such as: \200 intermediate lesions of unknown s everity \200 ostial stenosis \200 left main stem disease \200 disease at bifurcation sites. It images the plaque, not just the lumen. \200 It allows optimal results during angioplas ty and stenting. INTRAVASCULAR ULTRASOUND 331 Fig. 6.12 Example of image obtained by IVUS. Fig. 6.13 IVUS image of a coronary stent. 332 CHAPTER 6 Cardiac catheterization & intervention Angioplasty and coronary stenting \200 Currently, coronary stents are implanted in > 85 % of revascularization procedures in the UK. National Institute for Health and Clinical Excellence (NICE) guidelines state that \200 \230stents should be used routinely for people with either stable or unstable angina or wit h acute myocardial infarction undergoing percutaneous intervention \200\231. Angioplasty Before stents became widely used in the mid to late 1990s, balloon angio- plast y alone was the commonest percutaneous treatment for coronary artery narrowings. The two ma in designs of balloon catheters now com- monly used are over-the-wire and rapid-exchange sy stems. Both types of catheter consists of three parts: \200 the shaft : there are two mai n varieties: the hypotube, the advantage of which is a better balance between pushabillity and \202 exibility the corewire design, which is superior in terms of \202 exibility \200 the lumen : coax ial design (a tube within a tube) is the most common \200 the balloon : these are constru cted from varying plastics (e.g polyethylene, nylon), the mix of which affects the balloon \200\231s compliance. The design of the tip is important, as tapered tips are less traumatic when crossing narrowings. The balloon may also have a hydrophilic coating to render it more lubricious.