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Cardiac catheterization
INVESTIGATIONS
Cardiac catheterization
Key points
Konstantin Schwarz
C
Despite the increasing diagnostic role of non-invasive techniques for ischaemic heart disease, cardiac catheterization remains the gold standard for evaluation of coronary artery disease
C
With improvements in technology and reduction of vascular complications, radial access has become the preferred access route for left cardiac catheterization
C
Direct functional assessment of a coronary artery stenosis with a pressure wire can guide treatment and improve outcome in patients with chronic stable angina
C
Haemodynamic assessment by left and right heart catheterization is invaluable for diagnosis and treatment-planning in valvular and structural heart disease, and plays an important role in the treatment and monitoring of pulmonary arterial hypertension
Muhammad Ayyaz Ul Haq Bharat Sidhu Jim Nolan
Abstract Cardiac catheterization involves the insertion of fine-bore tubes (catheters) into the heart through cannulae inserted into a peripheral artery or vein. Previously, transfemoral access was predominantly used, but the safer radial artery approach has now become the preferred access route for most UK operators. Left heart catheterization is used to evaluate coronary arteries, left-sided valvular function, left ventricular function and aortic root anatomy. Haemodynamic and oxygen saturation data obtained from right and left heart catheterization provide information on cardiac chamber function, valvular function, pericardial constraint and pulmonary and systemic circulation haemodynamics. The comprehensive evaluation is especially invaluable in the diagnostic work-up and/or monitoring of patients with complex cardiac conditions; this particularly includes those with ischaemic heart disease, valvular disease, pulmonary arterial hypertension, intracardiac shunts, pericardial disease or heart failure.
catheterization was performed in 1929, when Werner Forssmann inserted a catheter into the right side of his own heart via a cutdown of his left antecubital vein. Modern invasive and interventional cardiology began when Mason Sones obtained the first selective coronary angiogram in 1958, using a brachial artery cutdown technique. The introduction of the Seldinger technique and development of pre-shaped catheters in the late 1960s established the femoral approach as the preferred method. The radial artery approach, which has superior procedure-related vascular complication rates, was introduced in 1989 by Campeau, and has rapidly been adopted by most cardiologists as their access route of choice.1 Left heart catheterization involves injection of contrast into the coronary arteries (selective coronary angiography) and/or left ventricle (ventriculography) and/or aorta (aortography). Pressures in the left ventricle and aorta are also measured. Right heart catheterization involves the measurement of pressures (haemodynamic data) in the pulmonary circulation and right heart chambers. Some of the haemodynamic data obtained rely on several assumptions, so must be interpreted together with information from other sources and assessment of the patient’s clinical condition.
Keywords Aortography; cardiac catheterization; coronary angiography; MRCP; right heart catheterization; ventriculography
Introduction Although non-invasive imaging of cardiac anatomy using echocardiography, cardiac computed tomography and magnetic resonance imaging is increasingly used, cardiac catheterization remains the gold standard method for evaluating coronary artery disease and cardiac haemodynamics; it is mandatory in many patients before percutaneous or surgical treatment. Advances in equipment design and catheterization techniques, particularly use of the radial access site, have improved the tolerability and safety of this technique. Cardiac catheterization involves the insertion of fine-bore tubes (catheters) into the heart through a peripheral artery or vein under fluoroscopic guidance. The first human heart
Indications
Konstantin Schwarz PhD MRCP is an St7 in Interventional Cardiology in the Cardiothoracic Centre at the University Hospital of North Midlands, Stoke-on-Trent, UK. Competing interests: none declared.
Patients with known or suspected coronary artery disease that is unstable or not controlled by optimal antianginal medication usually undergo left heart catheterization to clarify the diagnosis and help plan an optimal treatment strategy. Left ventricular catheterization allows visual assessment of left ventricular function and size, and measurement of left ventricular enddiastolic pressure (LVEDP) and the systolic pressure gradient across the aortic valve. Coronary angiography provides information on coronary anatomy. Aortography is also performed in patients with aortic regurgitation or aortic root dilatation, and during assessment for aortic valve interventions.
Muhammad Ayyaz Ul Haq MRCP is Interventional Fellow in the Cardiothoracic Centre at the University Hospital of North Midlands, Stoke-on-Trent, UK. Competing interests: none declared. Bharat Sidhu MRCP is an St4 in Cardiology in the Cardiothoracic Centre at the University Hospital of North Midlands, Stoke-on-Trent, UK. Competing interests: none declared. Jim Nolan MD FRCP is Professor of Cardiology in the Cardiothoracic Centre at the University Hospital of North Midlands, Stoke-on-Trent, UK. Competing interests: none declared.
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Please cite this article in press as: Schwarz K, et al., Cardiac catheterization, Medicine (2018), https://doi.org/10.1016/j.mpmed.2018.05.014
INVESTIGATIONS
Patients with mitral, tricuspid or pulmonary valve disease, heart failure, pericardial constriction or suspected intracardiac shunts, and those being assessed for cardiac transplantation, usually undergo both right and left cardiac catheterization. Right heart catheterization provides haemodynamic information on pulmonary and tricuspid valve gradients, right ventricular function, pulmonary artery pressure, right-sided and left-sided filling pressures, cardiac output (CO) and left-to-right shunts. Simultaneous left heart catheterization allows assessment of left ventricular and mitral valve function, as well as associated coronary disease.
For left ventriculography, a side-hole pigtail catheter is passed over a guidewire into the aortic root and across the aortic valve into the left ventricle. With the catheter in the left ventricle, the pressure is recorded and the end-diastolic pressure measured. Contrast ventriculography is performed using a mechanical power injector. Left ventricular size and global or regional wall motion abnormalities are visually assessed. Pressure is then recorded as the catheter is withdrawn across the aortic valve; a drop in systolic pressure indicates the presence of aortic stenosis. In patients with severe aortic stenosis, a straight guidewire can facilitate crossing of the valve but this carries potential complication risks (stroke, valve damage) and is no longer necessary as non-invasive tests, such as echocardiography, provide sufficient information on stenosis severity and left ventricular function. The pigtail catheter can also be placed above the aortic valve, and further contrast injected to image the ascending aorta and aortic arch, and assess aortic regurgitation (aortography).
Pre-catheterization evaluation This should include a full medical history, with particular emphasis on co-morbidities such as diabetes mellitus, kidney disease and anticoagulation status. Previous allergies to contrast medium or latex should be recorded. Full procedural details relating to previous cardiac or peripheral arterial interventions or cardiac surgery should be obtained, along with a physical examination and electrocardiogram. Routine laboratory tests should include a full blood count including platelet count, serum electrolytes and creatinine, plasma glucose and international normalized ratio. Patients with diabetes mellitus who are taking metformin should omit this drug on the morning of the procedure and for 2 days afterwards. Patients with a history of allergy to contrast media should be given prophylaxis with corticosteroids and antihistamines. Patients with chronic renal impairment are susceptible to contrast nephropathy, and require pre-treatment with intravenous fluids.
Transradial catheterization Although the femoral artery is large and accessible, vascular complications have always been an inherent part of cardiac catheterization using the femoral approach. They occur in up to 5% of cases, and are associated with increased mortality and other adverse outcomes. An access site haematoma requiring transfusion is independently associated with in-hospital and 1year mortality.2 Brachial access is rarely used because of its complexity and potentially higher complication rates. The Radial Vs femorAL access for coronary intervention (RIVAL) trial was decisive in accelerating the uptake of the transradial approach for coronary catheterization.3 This was a prospective, multicentre, randomized trial comparing femoral and radial access in patients with acute coronary syndrome. There was no difference in procedural success rates between groups, but there were significantly fewer major vascular complications in the radial group (1.4%) than the femoral group (3.7%), and there were no local vascular complications at radial puncture sites.3 A recent meta-analysis of 24 randomized control trials (n ¼ 22,843) confirmed that, compared with femoral access, radial access reduces mortality and major adverse cardiac events, while reducing major bleeding and vascular complications across the whole spectrum of patients presenting with coronary artery disease.4 As a consequence, diagnostic and interventional coronary procedures are increasingly being performed via the radial route (80% of cases).1 The radial artery is superficial and easily compressible, and any bleeding can therefore be easily controlled. In addition, no major veins or nerves lie close to the artery, thereby limiting the risks of neurological damage or arteriovenous fistula formation. Other benefits include immediate ambulation and greater post-procedure comfort for the patient, early discharge and lower costs. Dedicated radial sheaths with a hydrophilic coating are inserted into the radial artery close above the wrist via a Seldinger approach. Specific catheters have been developed to allow cannulation of both coronary ostia with a single specific transradial catheter, although it is also possible to use conventional transfemoral catheters. After completion of the procedure, simple devices are used to apply compression to the radial puncture site to achieve haemostasis.
Left heart catheterization Left heart catheterization is performed via arterial access using the radial or femoral artery. Transfemoral catheterization For most procedures, a sheath is inserted using a Seldinger technique. Selective coronary angiography is then performed using dedicated pre-shaped catheters; these are passed over a Jtipped guidewire into the aortic root, and fluoroscopically guided into the coronary artery ostia. In about 90% of transfemoral diagnostic studies, a Judkins’ catheter is used. This is a preshaped end-hole catheter designed to engage the coronary ostia with minimal manipulation. In the other 10% of studies, catheters of various shapes are used, depending on the size and orientation of the aortic root, and relative positions of the coronary ostia. The left and right coronary arteries (Figure 1) are imaged in several different projections, using 5e10 ml of contrast for each view. Typically, six to eight views of the left coronary artery and three of the right coronary artery are obtained at different angles. These angiographic images are used to detect and quantify the presence of stenotic coronary lesions, usually described by the percentage diameter stenosis compared with adjacent reference vessels. Once the procedure has been completed, the catheters and sheath are removed, and manual pressure is applied to the femoral puncture site(s) to obtain haemostasis. As an alternative, vascular closure devices can be used to close the vascular puncture rapidly and reduce the need for bed rest.
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Ó 2018 Published by Elsevier Ltd.
Please cite this article in press as: Schwarz K, et al., Cardiac catheterization, Medicine (2018), https://doi.org/10.1016/j.mpmed.2018.05.014
INVESTIGATIONS
Figure 1 Coronary angiogram. Left, and lower right panels: angiogram demonstrating anatomy of the left coronary artery in the left anterior oblique (LAO) cranial and posterio-anterior (PA) caudal views. The left coronary artery arises from the proximal ascending aorta as the left main stem (LMS). This bifurcates into the circumflex artery (Cx) and left anterior descending artery (LAD). Branches of the LAD are the septal arteries, which supply the septum (S), and the diagonal arteries (D). Branches of the circumflex artery are called obtuse marginals (OM). Upper right panel: the right coronary artery (RCA) arising from the right coronary sinus. The white arrow shows a tight discrete lesion. Posterior descending artery PDA.
Effective use of the transradial approach is associated with an important learning curve, and experience is necessary to puncture the small-calibre radial artery without inducing arterial spasm, which complicates manipulation of the catheter. For experienced operators, the use of radial access does not result in any significant increase in technical complexity, radiation exposure or procedural duration, and does not reduce the likelihood of success. More recently, other forearm approaches have been described, including the ulnar approach and a distal radial puncture at the anatomical snuffbox. Arterial spasm and radial artery occlusion are potential complications associated with radial access, but advances in the technique using appropriate anticoagulation, vasodilators, sheaths with minimal external diameter, sheathless access and patent haemostasis techniques make these complications very rare.
Right heart catheterization The right heart catheterization can be performed via the right cubital, right internal jugular or femoral vein. A sheath is placed using a Seldinger technique, and a catheter is passed into the right atrium, the right ventricle and the pulmonary artery using standard manipulations under fluoroscopic control. Flexible, balloon-tipped SwaneGanz catheters are the gold standard catheters used to measure right heart pressures and CO. Pulmonary artery pressure is recorded, and the catheter is advanced until it plugs a branch of one of the pulmonary arteries and the waveform changes to a pulmonary capillary wedge pressure (PCWP) tracing closely matched to left atrial pressure (Figure 2) Simultaneous right and left heart pressure recording is indicated especially for assessment of suspected constrictive pericarditis (right versus left ventricular) or mitral stenosis (PCWP versus left ventricular). The pulmonary artery catheter is then withdrawn and pressures in the pulmonary arteries, right ventricle and right atrium are measured sequentially (Figure 2). Left-to-right intracardiac shunts are assessed using a ‘saturation run’; in this, blood samples withdrawn from the pulmonary artery, right ventricle, right atrium and caval veins are analysed and their oxygen saturations compared. In patients who have a significant left-to-right shunt, oxygenated blood enters the right heart via a defect (such as an atrial septal defect, patent ductus arteriosus or ventricular septal defect) and produces an abnormal increase in oxygen saturation (the magnitude of this increase being proportional to the size of the shunt, which allows quantification of the lesion).
Fractional flow reserve (FFR) in chronic stable angina Percutaneous diagnostic interventional procedures to determine whether an identified coronary artery stenosis is functionally significant are now widely used. A pressure wire is passed down the coronary artery of interest. This wire contains a pressure transducer 3 cm back from the distal end. Measurements are made of the pressure drop across a particular lesion during maximal blood flow, or hyperaemia, to calculate the effective flow reduction caused by the lesion e the FFR (mean distal pressure/mean proximal pressure). A value of 1.0 would indicate absence of flow limitation. Percutaneous coronary intervention to alleviate the effects of lesions with FFR of 0.80 or less has been shown to improve outcome and reduce the need for urgent revascularization.
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INVESTIGATIONS
Pressure (mmHg)
Right heart withdrawal in a patient with mild pulmonary hypertension
40 Right ventricle
Pulmonary capillary wedge 20
Right atrium
Pulmonary artery
Normal values • Pulmonary artery <25 mmHg systolic, <10 mmHg diastolic • Right atrium mean <5 mmHg • Pulmonary capillary wedge mean 4–12 mmHg, left ventricular • Right ventricle <25 mmHg systolic, <5 mmHg diastolic end-diastolic <10 mmHg
Figure 2
Interpretation of haemodynamic data Normal ranges in right heart catheterization are shown in Table 1. Low LVEDP indicates hypovolaemia; high values indicate abnormal left ventricular function or fluid overload. Low PCWP indicates hypovolaemia; high values indicate mitral valve disease, left ventricular dysfunction or fluid overload. Raised pulmonary artery pressure (pulmonary hypertension) can be primary, caused by an intrinsic abnormality of the pulmonary arteries, or secondary. The latter results
Normal ranges in right heart catheterization Measurement
Normal range
Right atrial pressure (RAP) Right ventricular pressure, systolic (sRVP) Right ventricular pressure, diastolic (dRVP) Pulmonary artery pressure, systolic (sPAP) Pulmonary artery pressure, diastolic (dPAP) Pulmonary artery pressure, mean (mPAP) Pulmonary capillary wedge pressure, mean (mPCWP) Transpulmonary gradient (TPG) Pulmonary vascular resistance (PVR)
0e5 mmHg 15e25 mmHg 0e10 mmHg 15e25 mmHg 6e12 mmHg <25 mmHg 12 mmHg
Cardiac output (CO) a
12 mmHg 240 dyn.sec/cm5 or 1.6 ARUa >5.0 litres/minute
ARU, arbitrary resistance unit (or Wood unit), which is dyn-sec/cm5/80.
from raised left heart filling pressures in left-sided heart disease, long-standing left-to-right shunts, intrinsic lung disease, chronic pulmonary thromboembolism or, rarely, drug toxicity. It is an adverse prognostic factor and indicates increased operative risk. Pulmonary vascular resistance is calculated from the transpulmonary gradient (mean pulmonary artery pressure minus mean PCWP) and CO, and is a critical measurement when assessing patients for cardiac transplantation. Mitral regurgitation can produce giant ‘v’ waves in the PCWP, and values of 35 mmHg or more indicate severe regurgitation. This is a useful marker of the severity of regurgitation, but the size of the ‘v’ wave is considerably affected by left atrial compliance. The trans-mitral gradient (PCWP minus LVEDP) measures the severity of mitral stenosis. End-diastolic gradients >5 mmHg are significant, and gradients of 12e16 mmHg are typically seen in severe stenosis. However, the size of the gradient depends on heart rate and CO, and this technique has been superseded by echocardiographic criteria. Mitral valve area derived from the Gorlin formula (Table 2)5 is more reliable, but requires estimation of CO. The pull-back aortic gradient (Figure 3) is a measure of the severity of aortic stenosis but has been largely superseded by echocardiography and is rarely required. Left-to-right intracardiac shunts are assessed by comparing oxygen saturations in the superior vena cava, inferior vena cava, high-, mid- and low-right atrium, right ventricle, pulmonary artery and aorta. Small shunts may not be detected by calculating flows (O2 consumption/O2 content difference). The magnitude of the shunt is calculated in terms of the relative blood flows in the pulmonary (Qp)
Table 1
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INVESTIGATIONS
Formulae used for haemodynamic data Left-to-right shunt
Aortic valve area (cm2), by Gorlin formula Mitral valve area (cm2), by Gorlin formula CO (litres/minute)
Qp/Qs ¼ (SatAorta e SatMixed venous)/(SatPV e SatPA) SatMixed venous ¼ (3 SatSVC þ SatIVC )/4 If not available, SatsPV can be substituted by 98% COðlitres=minuteÞ pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ðOpening time=beatÞ Heart rate Mean gradient ðmmHgÞ 44:3 COðlitres=minuteÞ pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ðOpening time=beatÞ Heart rate Mean gradient ðmmHgÞ 37:7 Oxygen consumptionðml=minuteÞ 1:36 ðSatAorta SatPA Þ Hb ðg=litreÞ Oxygen consumption ¼ 125 BSA
BSA, body surface area; IVC, inferior vena cava; PA, pulmonary artery; PV, pulmonary vein; Satxxx, oxygen saturation in XXX part of circulatory system; SVC, superior vena cava.
Table 2
Pressure during pull-back across the aortic valve, showing a peak-to-peak gradient of 50 mmHg
Pressure (mmHg)
50 mmHg 100
50
Figure 3
and systemic (Qs) circulations, and expressed as a ratio Qp/Qs (a ratio >1.5 suggests a significant left-to-right shunt) (Table 2). CO is measured using a thermodilution method or the Fick principle. The latter calculates CO from oxygen consumption (¼ O2 inspired minus O2 expired, measured using a metabolic hood or Douglas bag) and the arteriovenous difference in oxygen content (measured from blood samples taken in the pulmonary artery and aorta). Alternatively (but less accurately), oxygen consumption can be estimated as 3 ml O2/kg body weight, and empirically calculated as VO2 ¼ 125 body surface area (BSA):
Complications Major complications (e.g. major haemorrhage, myocardial infarction, stroke, major arrhythmia, death) occur in 0.25% of patients; they are more common in those with advanced cardiac disease. Minor complications (e.g. vaso-vagal reactions, contrast reactions) occur in about 5% of patients. Predictors of significant complications include advanced New York Heart Association functional class, hypotension, shock, aortic valve disease and renal insufficiency. Access site-related neurovascular complications are common with the brachial artery approach (6.5%), and occur in about 1e2% of cases with the femoral approach. The risk of access site complications is significantly lower with the radial approach. A
COFick [1253BSA=1:363ðSatsAorta SatsPA Þ3Hb½g=litre
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INVESTIGATIONS
KEY REFERENCES 1 Ludman P. National audit of percutaneous coronary interventions annual report 2015. 2016, https://www.hqip.org.uk/resources/ national-audit-of-percutaneous-coronary-interventions-annualpublic-report/. 2 Yatskar L, Selzer F, Feit F, et al. Access site hematoma requiring blood transfusion predicts mortality in patients undergoing percutaneous coronary intervention: data from the National Heart, Lung, and Blood Institute Dynamic Registry. Catheter Cardiovasc Interv 2007; 69: 961e6. 3 Jolly SS, Yusuf S, Cairns J, et al. Radial versus femoral access for coronary angiography and intervention in patients with acute
coronary syndromes (RIVAL): a randomised, parallel group, multicentre trial. Lancet 2011; 377: 1409e20. 4 Ferrante G, Rao SV, Juni P, et al. Radial versus femoral access for coronary interventions across the entire spectrum of patients with coronary artery disease: a meta-analysis of randomized trials. JACC Cardiovasc Interv 2016; 9: 1419e34. 5 Gorlin R, Gorlin SG. Hydraulic formula for calculation of the area of the stenotic mitral valve, other cardiac valves, and central circulatory shunts. Am Heart J 1951; 41: 1e29.
TEST YOURSELF To test your knowledge based on the article you have just read, please complete the questions below. The answers can be found at the end of the issue or online here. A. B. C. D. E.
Question 1 A 74-year-old man presented with a 6-month history of exertional chest pain radiating down his left arm. He described dull aches when pushing himself up inclines at a fast pace once or twice a month, His past medical history included hypertension, benign prostate hyperplasia and osteoarthritis. He was taking losartan, tamsulosin and paracetamol. Clinical examination was unremarkable.
Shorter learning curve Lower incidence of arterial spasm Decrease in major bleeding and mortality Shorter distance to the heart chambers Delayed mobilization and ambulation following procedure
Question 3 A 68-year-old woman was being investigated for worsening exertional shortness of breath. Her transthoracic echocardiography showed dilated right heart chambers. She underwent right heart catheterization with the following results: systolic PAP¼48 mmHg, mean PAP¼34 mmHg, PCWP¼10 mmHg, CO¼5.2 litres/ minute Oxygen saturation run: SatsPA ¼ 82%, SatRV ¼ 82%, SatRA ¼ 84%, SatsSVC ¼ 59%, SatIVC ¼ 62%, SatLV ¼ 98% Reminder: Oxygen saturation ‘Sat’ SatMixed venous ¼ (3 SatSVC þ SatIVC)/4 Qp/Qs¼ (SatAorta eSatMixed venous)/(SatPV eSatPA); if not available, SatPV can be substituted by 98%, SatAorta can be substituted by SatLV.
What is the next most appropriate management of this patient? A. Arrange an exercise treadmill test and start him on a statin and aspirin B. Start patient on aspirin, statin, arrange an outpatient myocardial perfusion scan, stress echocardiogram or stress cardiac MRI and reassess in a few weeks’ time C. Reassure him that this is atypical chest pain and discharge him from care D. Arrange urgent outpatient coronary angiography and start him on a statin E. Start him on aspirin, a statin and antianginal medication and reassess him in few weeks
The A. B. C. D.
following statement is true: The transpulmonary gradient is within normal limits There is severe pulmonary hypertension There is significant right to left shunt The patient should be considered for shunt closure procedure E. There is a shunt on the level of pulmonary artery
Question 2 A 64-year-old woman presented with acute severe chest pain and sweating that had lasted for 3 hours. On ECG and troponin testing, she was found to have an acute myocardial infarction and was referred for coronary artery angiography. What is the major reason to prefer radial artery access over femoral artery access in this situation?
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Please cite this article in press as: Schwarz K, et al., Cardiac catheterization, Medicine (2018), https://doi.org/10.1016/j.mpmed.2018.05.014
Cardiac catheterization
Key points
Konstantin Schwarz
C
Despite the increasing diagnostic role of non-invasive techniques for ischaemic heart disease, cardiac catheterization remains the gold standard for evaluation of coronary artery disease
C
With improvements in technology and reduction of vascular complications, radial access has become the preferred access route for left cardiac catheterization
C
Direct functional assessment of a coronary artery stenosis with a pressure wire can guide treatment and improve outcome in patients with chronic stable angina
C
Haemodynamic assessment by left and right heart catheterization is invaluable for diagnosis and treatment-planning in valvular and structural heart disease, and plays an important role in the treatment and monitoring of pulmonary arterial hypertension
Muhammad Ayyaz Ul Haq Bharat Sidhu Jim Nolan
Abstract Cardiac catheterization involves the insertion of fine-bore tubes (catheters) into the heart through cannulae inserted into a peripheral artery or vein. Previously, transfemoral access was predominantly used, but the safer radial artery approach has now become the preferred access route for most UK operators. Left heart catheterization is used to evaluate coronary arteries, left-sided valvular function, left ventricular function and aortic root anatomy. Haemodynamic and oxygen saturation data obtained from right and left heart catheterization provide information on cardiac chamber function, valvular function, pericardial constraint and pulmonary and systemic circulation haemodynamics. The comprehensive evaluation is especially invaluable in the diagnostic work-up and/or monitoring of patients with complex cardiac conditions; this particularly includes those with ischaemic heart disease, valvular disease, pulmonary arterial hypertension, intracardiac shunts, pericardial disease or heart failure.
catheterization was performed in 1929, when Werner Forssmann inserted a catheter into the right side of his own heart via a cutdown of his left antecubital vein. Modern invasive and interventional cardiology began when Mason Sones obtained the first selective coronary angiogram in 1958, using a brachial artery cutdown technique. The introduction of the Seldinger technique and development of pre-shaped catheters in the late 1960s established the femoral approach as the preferred method. The radial artery approach, which has superior procedure-related vascular complication rates, was introduced in 1989 by Campeau, and has rapidly been adopted by most cardiologists as their access route of choice.1 Left heart catheterization involves injection of contrast into the coronary arteries (selective coronary angiography) and/or left ventricle (ventriculography) and/or aorta (aortography). Pressures in the left ventricle and aorta are also measured. Right heart catheterization involves the measurement of pressures (haemodynamic data) in the pulmonary circulation and right heart chambers. Some of the haemodynamic data obtained rely on several assumptions, so must be interpreted together with information from other sources and assessment of the patient’s clinical condition.
Keywords Aortography; cardiac catheterization; coronary angiography; MRCP; right heart catheterization; ventriculography
Introduction Although non-invasive imaging of cardiac anatomy using echocardiography, cardiac computed tomography and magnetic resonance imaging is increasingly used, cardiac catheterization remains the gold standard method for evaluating coronary artery disease and cardiac haemodynamics; it is mandatory in many patients before percutaneous or surgical treatment. Advances in equipment design and catheterization techniques, particularly use of the radial access site, have improved the tolerability and safety of this technique. Cardiac catheterization involves the insertion of fine-bore tubes (catheters) into the heart through a peripheral artery or vein under fluoroscopic guidance. The first human heart
Indications
Konstantin Schwarz PhD MRCP is an St7 in Interventional Cardiology in the Cardiothoracic Centre at the University Hospital of North Midlands, Stoke-on-Trent, UK. Competing interests: none declared.
Patients with known or suspected coronary artery disease that is unstable or not controlled by optimal antianginal medication usually undergo left heart catheterization to clarify the diagnosis and help plan an optimal treatment strategy. Left ventricular catheterization allows visual assessment of left ventricular function and size, and measurement of left ventricular enddiastolic pressure (LVEDP) and the systolic pressure gradient across the aortic valve. Coronary angiography provides information on coronary anatomy. Aortography is also performed in patients with aortic regurgitation or aortic root dilatation, and during assessment for aortic valve interventions.
Muhammad Ayyaz Ul Haq MRCP is Interventional Fellow in the Cardiothoracic Centre at the University Hospital of North Midlands, Stoke-on-Trent, UK. Competing interests: none declared. Bharat Sidhu MRCP is an St4 in Cardiology in the Cardiothoracic Centre at the University Hospital of North Midlands, Stoke-on-Trent, UK. Competing interests: none declared. Jim Nolan MD FRCP is Professor of Cardiology in the Cardiothoracic Centre at the University Hospital of North Midlands, Stoke-on-Trent, UK. Competing interests: none declared.
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Please cite this article in press as: Schwarz K, et al., Cardiac catheterization, Medicine (2018), https://doi.org/10.1016/j.mpmed.2018.05.014
INVESTIGATIONS
Patients with mitral, tricuspid or pulmonary valve disease, heart failure, pericardial constriction or suspected intracardiac shunts, and those being assessed for cardiac transplantation, usually undergo both right and left cardiac catheterization. Right heart catheterization provides haemodynamic information on pulmonary and tricuspid valve gradients, right ventricular function, pulmonary artery pressure, right-sided and left-sided filling pressures, cardiac output (CO) and left-to-right shunts. Simultaneous left heart catheterization allows assessment of left ventricular and mitral valve function, as well as associated coronary disease.
For left ventriculography, a side-hole pigtail catheter is passed over a guidewire into the aortic root and across the aortic valve into the left ventricle. With the catheter in the left ventricle, the pressure is recorded and the end-diastolic pressure measured. Contrast ventriculography is performed using a mechanical power injector. Left ventricular size and global or regional wall motion abnormalities are visually assessed. Pressure is then recorded as the catheter is withdrawn across the aortic valve; a drop in systolic pressure indicates the presence of aortic stenosis. In patients with severe aortic stenosis, a straight guidewire can facilitate crossing of the valve but this carries potential complication risks (stroke, valve damage) and is no longer necessary as non-invasive tests, such as echocardiography, provide sufficient information on stenosis severity and left ventricular function. The pigtail catheter can also be placed above the aortic valve, and further contrast injected to image the ascending aorta and aortic arch, and assess aortic regurgitation (aortography).
Pre-catheterization evaluation This should include a full medical history, with particular emphasis on co-morbidities such as diabetes mellitus, kidney disease and anticoagulation status. Previous allergies to contrast medium or latex should be recorded. Full procedural details relating to previous cardiac or peripheral arterial interventions or cardiac surgery should be obtained, along with a physical examination and electrocardiogram. Routine laboratory tests should include a full blood count including platelet count, serum electrolytes and creatinine, plasma glucose and international normalized ratio. Patients with diabetes mellitus who are taking metformin should omit this drug on the morning of the procedure and for 2 days afterwards. Patients with a history of allergy to contrast media should be given prophylaxis with corticosteroids and antihistamines. Patients with chronic renal impairment are susceptible to contrast nephropathy, and require pre-treatment with intravenous fluids.
Transradial catheterization Although the femoral artery is large and accessible, vascular complications have always been an inherent part of cardiac catheterization using the femoral approach. They occur in up to 5% of cases, and are associated with increased mortality and other adverse outcomes. An access site haematoma requiring transfusion is independently associated with in-hospital and 1year mortality.2 Brachial access is rarely used because of its complexity and potentially higher complication rates. The Radial Vs femorAL access for coronary intervention (RIVAL) trial was decisive in accelerating the uptake of the transradial approach for coronary catheterization.3 This was a prospective, multicentre, randomized trial comparing femoral and radial access in patients with acute coronary syndrome. There was no difference in procedural success rates between groups, but there were significantly fewer major vascular complications in the radial group (1.4%) than the femoral group (3.7%), and there were no local vascular complications at radial puncture sites.3 A recent meta-analysis of 24 randomized control trials (n ¼ 22,843) confirmed that, compared with femoral access, radial access reduces mortality and major adverse cardiac events, while reducing major bleeding and vascular complications across the whole spectrum of patients presenting with coronary artery disease.4 As a consequence, diagnostic and interventional coronary procedures are increasingly being performed via the radial route (80% of cases).1 The radial artery is superficial and easily compressible, and any bleeding can therefore be easily controlled. In addition, no major veins or nerves lie close to the artery, thereby limiting the risks of neurological damage or arteriovenous fistula formation. Other benefits include immediate ambulation and greater post-procedure comfort for the patient, early discharge and lower costs. Dedicated radial sheaths with a hydrophilic coating are inserted into the radial artery close above the wrist via a Seldinger approach. Specific catheters have been developed to allow cannulation of both coronary ostia with a single specific transradial catheter, although it is also possible to use conventional transfemoral catheters. After completion of the procedure, simple devices are used to apply compression to the radial puncture site to achieve haemostasis.
Left heart catheterization Left heart catheterization is performed via arterial access using the radial or femoral artery. Transfemoral catheterization For most procedures, a sheath is inserted using a Seldinger technique. Selective coronary angiography is then performed using dedicated pre-shaped catheters; these are passed over a Jtipped guidewire into the aortic root, and fluoroscopically guided into the coronary artery ostia. In about 90% of transfemoral diagnostic studies, a Judkins’ catheter is used. This is a preshaped end-hole catheter designed to engage the coronary ostia with minimal manipulation. In the other 10% of studies, catheters of various shapes are used, depending on the size and orientation of the aortic root, and relative positions of the coronary ostia. The left and right coronary arteries (Figure 1) are imaged in several different projections, using 5e10 ml of contrast for each view. Typically, six to eight views of the left coronary artery and three of the right coronary artery are obtained at different angles. These angiographic images are used to detect and quantify the presence of stenotic coronary lesions, usually described by the percentage diameter stenosis compared with adjacent reference vessels. Once the procedure has been completed, the catheters and sheath are removed, and manual pressure is applied to the femoral puncture site(s) to obtain haemostasis. As an alternative, vascular closure devices can be used to close the vascular puncture rapidly and reduce the need for bed rest.
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Figure 1 Coronary angiogram. Left, and lower right panels: angiogram demonstrating anatomy of the left coronary artery in the left anterior oblique (LAO) cranial and posterio-anterior (PA) caudal views. The left coronary artery arises from the proximal ascending aorta as the left main stem (LMS). This bifurcates into the circumflex artery (Cx) and left anterior descending artery (LAD). Branches of the LAD are the septal arteries, which supply the septum (S), and the diagonal arteries (D). Branches of the circumflex artery are called obtuse marginals (OM). Upper right panel: the right coronary artery (RCA) arising from the right coronary sinus. The white arrow shows a tight discrete lesion. Posterior descending artery PDA.
Effective use of the transradial approach is associated with an important learning curve, and experience is necessary to puncture the small-calibre radial artery without inducing arterial spasm, which complicates manipulation of the catheter. For experienced operators, the use of radial access does not result in any significant increase in technical complexity, radiation exposure or procedural duration, and does not reduce the likelihood of success. More recently, other forearm approaches have been described, including the ulnar approach and a distal radial puncture at the anatomical snuffbox. Arterial spasm and radial artery occlusion are potential complications associated with radial access, but advances in the technique using appropriate anticoagulation, vasodilators, sheaths with minimal external diameter, sheathless access and patent haemostasis techniques make these complications very rare.
Right heart catheterization The right heart catheterization can be performed via the right cubital, right internal jugular or femoral vein. A sheath is placed using a Seldinger technique, and a catheter is passed into the right atrium, the right ventricle and the pulmonary artery using standard manipulations under fluoroscopic control. Flexible, balloon-tipped SwaneGanz catheters are the gold standard catheters used to measure right heart pressures and CO. Pulmonary artery pressure is recorded, and the catheter is advanced until it plugs a branch of one of the pulmonary arteries and the waveform changes to a pulmonary capillary wedge pressure (PCWP) tracing closely matched to left atrial pressure (Figure 2) Simultaneous right and left heart pressure recording is indicated especially for assessment of suspected constrictive pericarditis (right versus left ventricular) or mitral stenosis (PCWP versus left ventricular). The pulmonary artery catheter is then withdrawn and pressures in the pulmonary arteries, right ventricle and right atrium are measured sequentially (Figure 2). Left-to-right intracardiac shunts are assessed using a ‘saturation run’; in this, blood samples withdrawn from the pulmonary artery, right ventricle, right atrium and caval veins are analysed and their oxygen saturations compared. In patients who have a significant left-to-right shunt, oxygenated blood enters the right heart via a defect (such as an atrial septal defect, patent ductus arteriosus or ventricular septal defect) and produces an abnormal increase in oxygen saturation (the magnitude of this increase being proportional to the size of the shunt, which allows quantification of the lesion).
Fractional flow reserve (FFR) in chronic stable angina Percutaneous diagnostic interventional procedures to determine whether an identified coronary artery stenosis is functionally significant are now widely used. A pressure wire is passed down the coronary artery of interest. This wire contains a pressure transducer 3 cm back from the distal end. Measurements are made of the pressure drop across a particular lesion during maximal blood flow, or hyperaemia, to calculate the effective flow reduction caused by the lesion e the FFR (mean distal pressure/mean proximal pressure). A value of 1.0 would indicate absence of flow limitation. Percutaneous coronary intervention to alleviate the effects of lesions with FFR of 0.80 or less has been shown to improve outcome and reduce the need for urgent revascularization.
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Pressure (mmHg)
Right heart withdrawal in a patient with mild pulmonary hypertension
40 Right ventricle
Pulmonary capillary wedge 20
Right atrium
Pulmonary artery
Normal values • Pulmonary artery <25 mmHg systolic, <10 mmHg diastolic • Right atrium mean <5 mmHg • Pulmonary capillary wedge mean 4–12 mmHg, left ventricular • Right ventricle <25 mmHg systolic, <5 mmHg diastolic end-diastolic <10 mmHg
Figure 2
Interpretation of haemodynamic data Normal ranges in right heart catheterization are shown in Table 1. Low LVEDP indicates hypovolaemia; high values indicate abnormal left ventricular function or fluid overload. Low PCWP indicates hypovolaemia; high values indicate mitral valve disease, left ventricular dysfunction or fluid overload. Raised pulmonary artery pressure (pulmonary hypertension) can be primary, caused by an intrinsic abnormality of the pulmonary arteries, or secondary. The latter results
Normal ranges in right heart catheterization Measurement
Normal range
Right atrial pressure (RAP) Right ventricular pressure, systolic (sRVP) Right ventricular pressure, diastolic (dRVP) Pulmonary artery pressure, systolic (sPAP) Pulmonary artery pressure, diastolic (dPAP) Pulmonary artery pressure, mean (mPAP) Pulmonary capillary wedge pressure, mean (mPCWP) Transpulmonary gradient (TPG) Pulmonary vascular resistance (PVR)
0e5 mmHg 15e25 mmHg 0e10 mmHg 15e25 mmHg 6e12 mmHg <25 mmHg 12 mmHg
Cardiac output (CO) a
12 mmHg 240 dyn.sec/cm5 or 1.6 ARUa >5.0 litres/minute
ARU, arbitrary resistance unit (or Wood unit), which is dyn-sec/cm5/80.
from raised left heart filling pressures in left-sided heart disease, long-standing left-to-right shunts, intrinsic lung disease, chronic pulmonary thromboembolism or, rarely, drug toxicity. It is an adverse prognostic factor and indicates increased operative risk. Pulmonary vascular resistance is calculated from the transpulmonary gradient (mean pulmonary artery pressure minus mean PCWP) and CO, and is a critical measurement when assessing patients for cardiac transplantation. Mitral regurgitation can produce giant ‘v’ waves in the PCWP, and values of 35 mmHg or more indicate severe regurgitation. This is a useful marker of the severity of regurgitation, but the size of the ‘v’ wave is considerably affected by left atrial compliance. The trans-mitral gradient (PCWP minus LVEDP) measures the severity of mitral stenosis. End-diastolic gradients >5 mmHg are significant, and gradients of 12e16 mmHg are typically seen in severe stenosis. However, the size of the gradient depends on heart rate and CO, and this technique has been superseded by echocardiographic criteria. Mitral valve area derived from the Gorlin formula (Table 2)5 is more reliable, but requires estimation of CO. The pull-back aortic gradient (Figure 3) is a measure of the severity of aortic stenosis but has been largely superseded by echocardiography and is rarely required. Left-to-right intracardiac shunts are assessed by comparing oxygen saturations in the superior vena cava, inferior vena cava, high-, mid- and low-right atrium, right ventricle, pulmonary artery and aorta. Small shunts may not be detected by calculating flows (O2 consumption/O2 content difference). The magnitude of the shunt is calculated in terms of the relative blood flows in the pulmonary (Qp)
Table 1
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Formulae used for haemodynamic data Left-to-right shunt
Aortic valve area (cm2), by Gorlin formula Mitral valve area (cm2), by Gorlin formula CO (litres/minute)
Qp/Qs ¼ (SatAorta e SatMixed venous)/(SatPV e SatPA) SatMixed venous ¼ (3 SatSVC þ SatIVC )/4 If not available, SatsPV can be substituted by 98% COðlitres=minuteÞ pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ðOpening time=beatÞ Heart rate Mean gradient ðmmHgÞ 44:3 COðlitres=minuteÞ pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ðOpening time=beatÞ Heart rate Mean gradient ðmmHgÞ 37:7 Oxygen consumptionðml=minuteÞ 1:36 ðSatAorta SatPA Þ Hb ðg=litreÞ Oxygen consumption ¼ 125 BSA
BSA, body surface area; IVC, inferior vena cava; PA, pulmonary artery; PV, pulmonary vein; Satxxx, oxygen saturation in XXX part of circulatory system; SVC, superior vena cava.
Table 2
Pressure during pull-back across the aortic valve, showing a peak-to-peak gradient of 50 mmHg
Pressure (mmHg)
50 mmHg 100
50
Figure 3
and systemic (Qs) circulations, and expressed as a ratio Qp/Qs (a ratio >1.5 suggests a significant left-to-right shunt) (Table 2). CO is measured using a thermodilution method or the Fick principle. The latter calculates CO from oxygen consumption (¼ O2 inspired minus O2 expired, measured using a metabolic hood or Douglas bag) and the arteriovenous difference in oxygen content (measured from blood samples taken in the pulmonary artery and aorta). Alternatively (but less accurately), oxygen consumption can be estimated as 3 ml O2/kg body weight, and empirically calculated as VO2 ¼ 125 body surface area (BSA):
Complications Major complications (e.g. major haemorrhage, myocardial infarction, stroke, major arrhythmia, death) occur in 0.25% of patients; they are more common in those with advanced cardiac disease. Minor complications (e.g. vaso-vagal reactions, contrast reactions) occur in about 5% of patients. Predictors of significant complications include advanced New York Heart Association functional class, hypotension, shock, aortic valve disease and renal insufficiency. Access site-related neurovascular complications are common with the brachial artery approach (6.5%), and occur in about 1e2% of cases with the femoral approach. The risk of access site complications is significantly lower with the radial approach. A
COFick [1253BSA=1:363ðSatsAorta SatsPA Þ3Hb½g=litre
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KEY REFERENCES 1 Ludman P. National audit of percutaneous coronary interventions annual report 2015. 2016, https://www.hqip.org.uk/resources/ national-audit-of-percutaneous-coronary-interventions-annualpublic-report/. 2 Yatskar L, Selzer F, Feit F, et al. Access site hematoma requiring blood transfusion predicts mortality in patients undergoing percutaneous coronary intervention: data from the National Heart, Lung, and Blood Institute Dynamic Registry. Catheter Cardiovasc Interv 2007; 69: 961e6. 3 Jolly SS, Yusuf S, Cairns J, et al. Radial versus femoral access for coronary angiography and intervention in patients with acute
coronary syndromes (RIVAL): a randomised, parallel group, multicentre trial. Lancet 2011; 377: 1409e20. 4 Ferrante G, Rao SV, Juni P, et al. Radial versus femoral access for coronary interventions across the entire spectrum of patients with coronary artery disease: a meta-analysis of randomized trials. JACC Cardiovasc Interv 2016; 9: 1419e34. 5 Gorlin R, Gorlin SG. Hydraulic formula for calculation of the area of the stenotic mitral valve, other cardiac valves, and central circulatory shunts. Am Heart J 1951; 41: 1e29.
TEST YOURSELF To test your knowledge based on the article you have just read, please complete the questions below. The answers can be found at the end of the issue or online here. A. B. C. D. E.
Question 1 A 74-year-old man presented with a 6-month history of exertional chest pain radiating down his left arm. He described dull aches when pushing himself up inclines at a fast pace once or twice a month, His past medical history included hypertension, benign prostate hyperplasia and osteoarthritis. He was taking losartan, tamsulosin and paracetamol. Clinical examination was unremarkable.
Shorter learning curve Lower incidence of arterial spasm Decrease in major bleeding and mortality Shorter distance to the heart chambers Delayed mobilization and ambulation following procedure
Question 3 A 68-year-old woman was being investigated for worsening exertional shortness of breath. Her transthoracic echocardiography showed dilated right heart chambers. She underwent right heart catheterization with the following results: systolic PAP¼48 mmHg, mean PAP¼34 mmHg, PCWP¼10 mmHg, CO¼5.2 litres/ minute Oxygen saturation run: SatsPA ¼ 82%, SatRV ¼ 82%, SatRA ¼ 84%, SatsSVC ¼ 59%, SatIVC ¼ 62%, SatLV ¼ 98% Reminder: Oxygen saturation ‘Sat’ SatMixed venous ¼ (3 SatSVC þ SatIVC)/4 Qp/Qs¼ (SatAorta eSatMixed venous)/(SatPV eSatPA); if not available, SatPV can be substituted by 98%, SatAorta can be substituted by SatLV.
What is the next most appropriate management of this patient? A. Arrange an exercise treadmill test and start him on a statin and aspirin B. Start patient on aspirin, statin, arrange an outpatient myocardial perfusion scan, stress echocardiogram or stress cardiac MRI and reassess in a few weeks’ time C. Reassure him that this is atypical chest pain and discharge him from care D. Arrange urgent outpatient coronary angiography and start him on a statin E. Start him on aspirin, a statin and antianginal medication and reassess him in few weeks
The A. B. C. D.
following statement is true: The transpulmonary gradient is within normal limits There is severe pulmonary hypertension There is significant right to left shunt The patient should be considered for shunt closure procedure E. There is a shunt on the level of pulmonary artery
Question 2 A 64-year-old woman presented with acute severe chest pain and sweating that had lasted for 3 hours. On ECG and troponin testing, she was found to have an acute myocardial infarction and was referred for coronary artery angiography. What is the major reason to prefer radial artery access over femoral artery access in this situation?
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