Full text of DOI:10.1383/medc.30.3.36.28279

INVESTIGATIONS
stress echocardiography, reliable reporting of studies requires
considerable experience. A segment of myocardium that is
hypokinetic or akinetic at rest represents infarction; a segment
that is normal at rest but becomes abnormal during stress
represents inducible ischaemia.
Cardiac Catheterization
Douglas Fraser
H Sandmann
J Nolan
Clinical value of MPI and stress echocardiography
For the detection of angiographic coronary stenoses, the sen-
sitivity and specificity of MPI are both about 90%; the sensi-
tivity and specificity of stress echocardiography are 80% and
90% respectively. Both methods provide prognostic inform-
ation that is independent of angiographic data. A normal study
is highly reassuring, and is associated with an annual rate of
cardiac death or non-fatal myocardial infarction of less than
1% for MPI and about 2% for stress echocardiography.
Cardiac catheterization involves insertion of a catheter into
the heart, through a cannula in a peripheral artery or vein. It
is performed under fluoroscopic guidance in a dedicated car-
diac catheter laboratory or a shared multipurpose angiography
suite. The most common access sites are the right femoral
artery and vein. Left heart catheterization involves injection of
contrast into the left ventricle (ventriculography) and selective
coronary angiography. Pressures in the left ventricle and aorta
are also measured. Right heart catheterization involves pass-
ing a catheter through the right heart chambers and into the
pulmonary circulation, and provides haemodynamic data.
Some of the haemodynamic data obtained rely on several
assumptions, and so must be interpreted together with inform-
ation from other sources and assessment of the patient’s clin-
ical condition. Procedure-related complications can occur,
and cardiac catheterization should be used only when the
results will significantly influence patient management. This
contribution concentrates on the role of diagnostic cardiac
catheterization in adults.
Hibernation studies
An increasingly important indication for MPI and stress echo-
cardiography is the identification of patients with myocardial
dysfunction at rest that may be improved by revascularization
(‘hibernating myocardium’). Using gated SPECT, hiber-
nating myocardium takes up tracer at rest while appearing
hypokinetic or akinetic. Using dobutamine stress echocardio-
graphy, it appears hypokinetic or akinetic at rest, but normal-
izes with low-dose dobutamine; a subsequent deterioration
with high-dose dobutamine (‘biphasic response’) is particular-
ly predictive.
‹
• Patients with known or suspected coronary artery disease
or aortic valve disease usually undergo left heart catheter-
ization, which involves left ventriculography and coronary
angiography. Left ventriculography allows visual assessment
of left ventricular (LV) function and size, and LV end-diastolic
pressure (LVEDP) and the systolic pressure gradient across
the aortic valve are measured. Coronary angiography provides
information on coronary anatomy. Aortography is also per-
formed in those with aortic regurgitation or aortic root
dilatation.
FURTHER READING
Cokkinos P, Kurbaan A S, Nihoyannopoulos P. Dobutamine Stress
Echocardiography. Br J Cardiol 1998; 5: 276–85.
(A succinct introduction to dobutamine stress echocardiography.)
Hachamovitch R, Berman D S, Shaw L J et al. Incremental Prognostic
Value of Myocardial Perfusion Single Photon Emission Computed
Tomography for the Prediction of Cardiac Death. Differential
Stratification for Risk of Cardiac Death and Myocardial Infarction.
Circulation 1998; 97: 535–43.
Douglas Fraser is a Specialist Registrar in the Cardiothoracic Centre
at North Staffordshire Hospital, Stoke-on-Trent, UK. He qualified from
the University of Oxford and the University of Cambridge, and trained in
general medicine and cardiology in the West Midlands. He is currently
training in interventional cardiology, and his research interests include
magnetic resonance vascular imaging.
(A large follow-up study illustrating the value of MPI in predicting
prognosis.)
Marwick T H, Case C, Sawada S et al. Prediction of Mortality
Using Dobutamine Echocardiography. J Am Coll Cardiol 2001; 37:
754–60.
H Sandmann is a Senior House Officer in the Medical Rotation at
North Staffordshire Hospital, Stoke-on-Trent, UK. He qualified from
Cologne Medical School, Cologne, Germany. His special interest is
cardiology.
(A large follow-up study illustrating the value of stress
echocardiography in predicting prognosis.)
Pennell D J, Prvulovich E. Clinicians’ Guide to Nuclear Medicine:
Nuclear Cardiology. London: British Nuclear Medicine Society, 1995.
(A thorough but readable introduction to nuclear cardiology,
assuming no previous knowledge of nuclear medicine.)
J Nolan is Consultant Cardiologist in the Cardiothoracic Centre
at North Staffordshire Hospital, Stoke-on-Trent, UK. He trained in
interventional and general cardiology in Leeds and in the Netherlands.
His research interests are heart failure and radial angioplasty.
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INVESTIGATIONS
• Patients with mitral valve disease, heart failure, pericardial
are end-hole catheters that are designed to engage the coro-
nary ostia with minimal manipulation. In the other 10% of
cases, catheters of various shapes are used, depending on the
size and orientation of the aortic root and the relative posi-
tions of the coronary ostia. The left and right coronary arteries
(Figure 1) are imaged in several different projections, using
5–10 ml of contrast injected by hand for each view; typically,
six to eight views of the left coronary artery and three of the
right coronary artery are obtained.
constriction or suspected intracardiac shunts usually undergo
both right and left cardiac catheterization. Right heart catheter-
ization provides haemodynamic information on right ventri-
cular function, pulmonary artery pressure, right-sided and left-
sided filling pressures, cardiac output and left-to-right shunts.
Simultaneous left heart catheterization allows assessment of
LV and mitral valve function and associated coronary disease.
Alternative access sites are the brachial and radial arteries.
Brachial artery access may be achieved using a brachial cut-
down procedure or a Seldinger technique. In the cut-down
procedure, an incision is made in the skin over the brachial
artery and a cannula is inserted via an arteriotomy under dir-
ect vision. A medial antecubital vein may also be cannu-
lated for right and left heart catheterization. Radial artery
catheterization may be performed if Allen’s test demonstrates
collateral ulnar circulation to the hand. Access is obtained at
the wrist and standard Judkin’s catheters may be used.
Procedure
Left heart catheterization
• Left heart catheterization is most commonly performed via
a cannula in the right femoral artery. A sheath is inserted
using a Seldinger technique, and a side-hole catheter (usually
a pigtail catheter) is passed over a J-tipped guidewire to the
aortic root and across the aortic valve into the left ventricle.
A straight guidewire is used to cross the valve in patients
with aortic stenosis, but crossing a severely stenosed valve
may be impossible.
• With the catheter in the left ventricle, the pressure is mea-
sured and the end-diastolic pressure is recorded. Ventriculo-
graphy is performed using a side-hole catheter (usually a pig-
tail catheter) connected to a mechanical power injector. The
pressure is then recorded as the catheter is withdrawn across
the aortic valve; a decrease in pressure indicates the presence
of aortic stenosis. The catheter may also be placed above the
aortic valve and a further power injection performed to image
the ascending aorta and assess aortic regurgitation.
Right heart catheterization
• The femoral vein is the most commonly used access site
for right heart catheterization. A sheath is placed in the vein
using a percutaneous Seldinger technique and a pre-shaped
end-hole catheter is passed into the right atrium, the right
ventricle and a pulmonary artery using standard manipulations
under fluoroscopic control. Pulmonary artery pressure is re-
corded, and the catheter is advanced until it blocks a branch
of one of the pulmonary arteries and the waveform changes to
a pulmonary capillary wedge (PCW) tracing that closely
matches the left atrial pressure.
• Selective coronary angiography is then performed. In about
90% of diagnostic studies, Judkin’s catheters are used. These
RV
LAD
Cx
PDA
a
b
Coronary angiography of a the left and b the right coronary arteries. LAD, left anterior descending artery; Cx, circumflex artery;
RV, right ventricular branch; PDA, posterior descending artery.
1
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INVESTIGATIONS
• When mitral valve disease is suspected, simultaneous left
mean PCW) and cardiac output, and is a critical parameter in
the assessment of patients for cardiac transplantation.
• Mitral regurgitation may produce giant ‘v’ waves in the
PCW, and values of 35 mm Hg or more indicate moderate-to-
severe regurgitation. This is a useful marker of the severity of
regurgitation, but the size of the v wave is considerably affec-
ted by left atrial compliance.
• The transmitral gradient (LVEDP minus PCW) is a measure
of the severity of mitral stenosis. End-diastolic gradients of
more than 5 mm Hg are significant, and gradients of 12–16 mm
Hg are typically seen in severe stenosis. However, the size of
the gradient depends on heart rate and cardiac output, and
this technique has been superseded by echocardiographic
criteria. Mitral valve area derived from the Gorlin formula
(Figure 3) is more reliable, but requires estimation of cardiac
output.
• The pull-back aortic gradient (Figure 4) is an important
measure of the severity of aortic stenosis; a gradient of
50 mm Hg or more prompts consideration of valve replace-
ment. Echocardiography measures instantaneous gradients,
which are typically 10 mm Hg or more greater than pull-back
gradients, and this may lead to significant overestimation of
the severity of aortic stenosis. However, if LV function is poor,
the pull-back gradient is reduced, and estimation of valve
area using echocardiography or the Gorlin formula is a more
accurate guide to severity.
heart catheterization is performed and a side-hole catheter is
advanced to the left ventricle from a sheath in the right femor-
al artery. The LV and PCW pressure are recorded; any differ-
ence between these measures in diastole indicates mitral
stenosis.
• The pulmonary artery catheter is then withdrawn and
pressures in the pulmonary arteries, the right ventricle and
the right atrium are measured sequentially (Figure 2). Left-to-
right intracardiac shunts are assessed using a ‘saturation run’,
in which blood samples withdrawn from the pulmonary ar-
tery, the right ventricle, the right atrium and the caval veins
are analysed and their oxygen saturations compared.
Flexible balloon-tipped catheters may also be used to
measure right heart pressures and cardiac output in ICUs
and coronary care units. They are commonly inserted via the
subclavian, femoral or jugular vein, and are floated across the
tricuspid and pulmonary valves; in many cases fluoroscopic
guidance is not needed. With the catheter positioned in the
pulmonary artery, cardiac output may be estimated using a
thermistor at the tip to measure the thermodilution of a bolus
of cold saline injected into the right atrium via a proximal
port.
Interpretation of haemodynamic data
• Low PCW pressure or LVEDP indicates hypovolaemia; high
values indicate incipient LV failure or fluid overload.
• Raised pulmonary artery pressure (pulmonary hyper-
tension) may result from chronically raised left heart filling
pressures in mitral valve disease or heart failure, from long-
standing left-to-right shunts, or from intrinsic lung disease.
It is an adverse prognostic indicator and indicates increased
operative risk.
• Left-to-right intracardiac shunts are assessed by comparing
oxygen saturations in the superior vena cava, the inferior vena
cava, the high, mid and low right atrium, the right ventricle
and the pulmonary artery. An increase in saturation of more
than 7% suggests a left-to-right shunt. Small shunts may not
be detected. The magnitude of the shunt is measured in terms
of the relative blood flows in the systemic and pulmonary
circulations.
• Pulmonary vascular resistance is calculated from the trans-
pulmonary gradient (mean pulmonary artery pressure minus
• Cardiac output is measured using a thermodilution method
or by the Fick principle. The Fick principle calculates cardiac
Right heart withdrawal in a patient with mild pulmonary hypertension
40
Right
ventricle
Right
atrium
Pulmonary
capillary wedge
20
Pulmonary artery
Normal values
• Right atrium mean < 5 mm Hg
• Right ventricle < 25 mm Hg systolic, < 5 mm Hg diastolic
• Pulmonary artery < 25 mm Hg systolic, < 10 mm Hg diastolic
• Pulmonary capillary wedge mean 4–12 mm Hg, left ventricular
end-diastolic < 10 mm Hg
3
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INVESTIGATIONS
Formulae used for haemodynamic data
•
Left-to-right shunt
Pulmonary flow
Systemic flow
=
SAO2 – MVO2
98 – PAO2
SAO2, aortic oxygen saturation; PAO2, pulmonary artery saturation
MVO2= (3 x superior vena cava saturation + inferior vena cava saturation)/4
•
•
•
Aortic valve area (cm2)
(Gorlin formula)
Cardiac output (litres/minute)
Opening time/beat x heart rate x √mean gradient (mm Hg) x 44⋅3
Mitral valve area (cm2)
(Gorlin formula)
Cardiac output (litres/minute)
Opening time/beat x heart rate x √mean gradient (mm Hg) x 37⋅7
Cardiac output (litres/minute)
(Fick principle)
Oxygen consumption (ml/minute)
1.36(SAO2 – PAO2) x haemoglobin concentration (g/litre)
3
Pressure during pull-back across the aortic valve, showing a peak-to-peak gradient of
50 mm Hg
50 mm Hg
100
50
4
output from oxygen consumption (measured using a meta-
bolic hood or a Douglas bag) and the arteriovenous difference
in oxygen content (measured from blood samples taken in the
pulmonary artery and aorta). Alternatively, oxygen consump-
tion can be estimated as 3 ml O2/kg body weight, but this is
less accurate.
REFERENCES
Davis C, VanRiper S, Longstreet J, Moscucci M.
Vascular Complications of Coronary Interventions. Heart Lung 1997;
26(2): 118–27.
Gorlin R, Gorlin S. Hydraulic Formula for Calculations of Stenotic
Mitral Valve, Other Cardiac Valves, and Central Circulatory Shunts.
Am Heart J 1951; 41: 1–29.
Johnson L W, Lozner E C, Johnson S et al. Coronary Arteriography
1984–1987: A Report of the Registry of the Society for Cardiac
Angiography and Interventions. I. Results and Complications.
Cathet Cardiovasc Diagn 1989; 17(1): 5–10.
Kern M J. Cardiac Catheterisation. 2nd ed. St Louis: Mosby, 1995.
Kiemeneij F, Laarman G J, Odekerken D, Slagboom T,
van der Wieken R. A Randomized Comparison of Percutaneous
Transluminal Coronary Angioplasty by the Radial, Brachial and
Complications
Minor complications such as vasovagal reactions and urti-
caria occur in about 5% of patients. Major complications
such as major haemorrhage, myocardial infarction, stroke,
major arrhythmia or death occur in 0.25% of patients, and are
more common in those with advanced cardiac disease. There
are fewer access site complications when the radial artery is
used.
‹
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INVESTIGATIONS
Femoral Approaches: The Access Study. J Am Coll Cardiol 1997;
29(6): 1269–75.
Kron J. The Case for Continued Scrutiny of Catheterization-related
Complications. Chest 1985; 87(6): 707–8.
MRI and CT
FURTHER READING
Braunwald E, Zipes D P, Libby P, eds. Heart Disease. 6th ed.
Philadelphia: Saunders, 2001.
Stefan Neubauer
(Includes up-to-date and well-illustrated chapters on cardiac
catheterization and angiography.)
Kern M J. Cardiac Catheterisation Handbook. St Louis: Mosby.
(A practical and comprehensive book covering the basics of cardiac
catheterization.)
The investigation of patients with cardiovascular disease
should provide information on both the anatomy and the
physiology of the heart and vessels, including the three-
dimensional anatomy of the heart and its surrounding struc-
tures, global and regional pump function, blood supply and
regional viability. The three main modalities currently used
in cardiology (echocardiography, cardiac catheterization and
nuclear methods) provide only limited information on the
pathophysiological state of the heart. In recent years, major
technical progress has been achieved in cardiac MRI and CT,
and these methods may allow complete and non-invasive
multiparametric characterization of the cardiovascular system.
There are currently few accepted indications for MRI and
CT in cardiology, and routine clinical applications (e.g. for
the diagnosis of coronary artery disease) require substantial
further development. However, it is likely that MRI, and, to
a lesser extent, CT will become standard diagnostic methods
in cardiac patients.
Kern M J, Ubeydullah D. The Interventional Cardiac Catheterisation
Handbook. St Louis: Mosby.
(A comprehensive introduction to percutaneous coronary
intervention.)
Kron J. The Case for Continued Scrutiny of Catheterization-related
Complications. Chest 1985; 87(6): 707–8.
(A useful review of the complications of cardiac catheterization.)
Background
MRI is usually based on the magnetic properties of the hydro-
gen nucleus, though other nuclei can be used. In an MRI
examination, the patient is placed in a powerful magnetic field
with which the protons in the body become aligned. Radio
waves in the form of a radiofrequency pulse transmitted into
the patient cause the alignment of the protons to change (e.g.
by 90°). When this radiofrequency pulse is turned off, the
protons in the patient’s body return to their neutral position,
emitting their own weak radio-wave signals, which are detec-
ted by receiver coils and used to produce an image. The
phase and amplitude of each returning radio-wave signal
can be determined using powerful computers and additional
magnetic field gradients, and this information can be used
to map the position of the excited protons. The resulting
image reflects not only proton density, but also the highly
complex manner in which protons resonate in their local en-
vironment. Cardiac MRI requires advanced technology, inclu-
ding a high-field magnet (typically 1.5 Tesla), fast-switching
gradient coils, and coils for transmission and signal reception.
Both CT and conventional MRI scans comprise an array of
small picture elements (pixels), but the distinction between
different tissues (contrast resolution) is greater in MRI. In
CT, the attenuation value of each pixel reflects only the local
tissue density. In MRI, the equivalent value is influenced by
Practice points
•
•
Cardiac catheterization provides comprehensive assessment
of left and right heart anatomy and function
Despite the development of non-invasive tests, cardiac
catheterization remains an essential investigation in many
cardiac disorders
•
•
Haemodynamic parameters are affected by physiological
conditions, and must be interpreted in light of this and
together with complementary information
Cardiac catheterization is an invasive test with potentially
major complications and so must be performed only when
the results will influence management
Stefan Neubauer is Clinical Reader in Cardiovascular Medicine
and Honorary Cardiology Consultant at the John Radcliffe Hospital,
Oxford, UK.
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