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where EDV is end-diastolic volume and ESV is end-systolic volume.
Most EF calculations are estimated by visual examination at the time
of ventriculography. SV requires a quantitative assessment with a calibration marker of true volume. This technique is not used for clinical
practice.
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Coronary Angiography and Ventriculography 153
Assessment of Mitral Regurgitation
The severity of mitral regurgitation is semiquantitative on the basis of
the degree of contrast opacification of the left atrium during left
ventriculography (Figs. 3-37 and 3-38). Although an angiographically
derived regurgitant fraction can be calculated, the use of echocardiography has supplanted the angiogram as the gold standard to assess
mitral regurgitation. Methods other than subjective grading are rarely
performed in today’s catheterization laboratory.
Ascending Aortography
Ascending aortography may be necessar y to determine the position
and/or patency of bypass grafts and degree of aortic insufficiency or
to exclude aortic dissection (Box 3-3). Aortography should be performed using side hole catheters (e.g., pigtail) to reduce the risk of
extending or inducing a dissection during contrast medium injection.
The catheter should be positioned just above the aortic valve, but not
close enough to interfere with valve opening or closing. For descending aortic dissection, the catheter is positioned above the suspected
proximal tear. Catheter position should be checked with a contrast test
before full-volume injection. Aortic regurgitation is estimated semiquantitatively as +1, +2, +3, or +4, depending on the opacification of
the ventricle after the third cycle following contrast injection (Figs.
3-39 and 3-40). Care should be taken to avoid entrapping the catheter
A
B
Figure 3 -37 Lef t ventriculogram in patient with mitral regurgitation.
A, Early opacification of the left atrium (L A). B, Left, Denser opacification
of LA. Right, LA is more densely opacified than LV after several beats. This
is severe (4+) mitral regurgitation (MR).
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Coronary Angiography and Ventriculography
Mild
Severe
Figure 3- 38 Angiographic evaluation of mitral regurgitation. (From Pujadas
G: Coronary angiography in the medical and surgical treatment of ischemic
heart disease, New York, 1980, McGraw-Hill.)
Moderate
Box 3-3 Indications and Contraindications for
Thoracic Aortography*
Indications
1. Aortic aneur ysm or aor tic dissection
2. Aortic insufficiency
3. Nonselective visualization of coronary bypass grafts
4. Supravalvular aortic stenosis
5. Brachiocephalic or arch vessel disease
6. Coarctation of the aorta
7. Aortic-to -PA or aortic -to-right-side hear t (e.g., sinus of Valsalva fistula)
communication
8. Aortic or periaor tic neoplastic disease
9. Arterial thromboembolic disease
10. Arterial inflammator y disease
Contraindications
1. Contrast media reaction
2. Injection into false lumen of aortic dissection
3. End-hole catheter malposition
4. Inability of the patient to tolerate additional radiographic contrast media
PA, Pulmonar y ar ter y.
*Note: In modern c ardiac catheterization laboratories, cineangiography is
acceptable for p atients with suspected dissec tion of the aor ta.
in a false lumen of a suspected aortic dissection by careful manipulation of the catheter and J-tipped guidewire.
Aortography can be performed by use of a minimum flow rate of
15 to 20 mL/sec for total volumes of 40 to 60 mL. High-flow (≥5 F)
catheters are required with standard power injectors. Cineangiographic frame rates of 15 frames/sec are satisfactory.
Aortography can be performed in LAO or lateral projection and
RAO projection (Figures 3-40 and 3-41).
Left Anterior Oblique or Lateral Projection
The LAO view is excellent for identifying dissection of the ascending
aorta extending up to the neck vessels; optimally delineating the aortic
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Coronary Angiography and Ventriculography 155
Mild
Severe
Figure 3-39 Angiographic evaluation of aortic regurgitation, right anterior
oblique (RAO) view. When the left anterior oblique (LAO) view is used, overestimation of aortic regurgitation occurs. (From Pujadas G: Coronary angiography in the medical and surgical treatment of ischemic heart disease,
New York, 1980, McGraw-Hill.)
Moderate
arch; and opening the aortic curvature and providing clear views of
the innominate, common carotid, and left subclavian arteries. The
coronary arteries at the root of the aorta are displayed in a semilateral
projection.
Right Anterior Oblique Projection
The descending thoracic aorta and the ascending aorta may be superimposed across the arch in the AP or LAO projection. The RAO view
is more helpful in delineating the effect of dissection on the lower
thoracic aorta and intercostal arteries, the origin of bypass grafts to
the left coronary system, or assessing aortic insufficiency.
There are no advantages to cranial or caudal tilts for viewing the
aorta. In nonselective coronary angiography in which aortic root angiography may help identify a vein graft takeoff, cranial and caudal
angulation may provide some increased detail.
Basics of X-Ray Generation and Radiation Safety
Cardiac angiography uses a complex interaction of radiographic x-ray
elements to transform energy into a visual image. The x-ray image
generation chain can be simplified into three major components:
(1) x-ray generator, (2) x-ray tube, and (3) II or detector. The details of
x-ray equipment should be familiar to all personnel working in the
catheterization laboratory. Figure 3-42 diagrams the x-ray system in a
cardiac catheterization laboratory (Fig. 3-43).
X-Ray Generator
The x-ray generator provides the power source necessary to accelerate
the electrons through the x-ray tube. The duration of x-ray exposure
is similar to the shutter speed on a regular camera. During the cardiac
“photographic” examination, exposure is usually set at a fast enough
speed to stop blurring caused by heart movement. During selective
coronary angiography, the shorter the exposure time, the better the
image. Exposure times of 3 to 6 msec reduce movement blur. Most
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Figure 3 -40 Top, Cineframe showing aortic regurgitation from lef t anterior
descending (LAD) aortogram. Note equal opacification of left ventricle (LV)
and aorta. Bottom, LV is still opacified after several beats. This is severe
aortic regurgitation.
modern generators are capable of delivering adequate power and
providing precise and automatically adjusted exposure timing. They
are equipped with either multiphase (alternating on and off) or short
and long pulse widths that are adjusted automatically for correct exposure. Manual settings, which are operator selected, are limited to cineangiographic frame rates (e.g., 15 to 60 frames/sec).
X-Ray Tubes
The function of the x-ray tube is to convert electrical energy, provided
from the generator, to an x-ray beam. Electrons emitted from a heated
filament (cathode) are accelerated toward a rapidly rotating disk
(anode) and at contact undergo conversion to x-radiation (Fig. 3-44).
This process generates extreme heat. The heat capacity of the tube is
a major limiting factor in the design of x-ray tubes. Only 0.2% to 0.6%
of the electrical energy provided to the tube is eventually converted
to x-rays.
In addition to the exposure times (controlled by the genera-
tor system) and the size of the imaging field (controlled by the x-ray
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Coronary Angiography and Ventriculography 157
A
B
Figure 3 -41 A, Normal aortogram in left anterior oblique (LAO) projection.
B, Dilated ascending aor ta.
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Figure 3- 42 Schematic diagram of an x-ray system. The x-ray tube below
the table radiates upward through the patient table to the image intensifier.
The video camera transmits the signal to video recorder, monitors, and
signal processors.
Coronary Angiography and Ventriculography
Video camera
Image intensifier
X-ray tube
C-arm
Generator
Video recorder
Video monitors
Analog-to-digital
converters and hard
drives
Figure 3-43 Cardiac catheterization laboratory with C-arm over patient.
Operators are observing images on fluoroscopic monitors.
tube), two other factors determine the quality of x-ray for proper
imaging:
1. Electrical current (mA): The number of photons (electrical particles) generated per unit of time. The greater the electrical current,
the greater the number of photons. More photons result in improved
image resolution. If the photon volume is marginal, the resulting
image may be “mottled” or have a spotty appearance. Increasing
the milliamperage improves this result, but the level of milliamperage is limited by the heat capacity of the x-ray tubes. In addition,
increasing the number of milliamperes markedly increases radiation exposure and scatter to the patient and catheterization laboratory personnel.
2. Level of kilovoltage (kV): The energy spectrum (wavelengths) of
the x-ray beam. The higher the level of kilovoltage, the shorter the
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Figure 3-44 Schematic of x-ray tube and x-ray production. A tungsten
rotating anode is the target of high-energy electrons from the cathode and
heating elements. The electrons striking the target release x-rays at a
90-degree angle. (Redrawn from Baim DS, Grossman W: Grossman’s cardiac
catheterization, angioplasty, and intervention, ed 6, Philadelphia, 2000,
Lippincott, Williams, and Wilkins.)
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Coronary Angiography and Ventriculography 159
Rotating anode
Glass housing
Cathode
Heated
filament
X-rays
Electrons
kV
mA
S
Figure 3- 45 Collimated x-ray beam passing through the body. kV, Kilovolts;
mA, milliamperes; S, seconds. (From King SB, Douglas JS Jr: Coronary
angiography and angioplasty, New York, 1985, McGraw-Hill.)
Exposure
wavelength of radiation and the greater the ability of x-rays to penetrate target tissue. Increased kilovoltage is especially important in
obese patients. To obtain better images through more tissue, a
higher kilovolt level is required. However, a high-kilovolt level also
produces lower resolution because of wide scatter and results in a
greater radiation exposure to patients and laboratory personnel. An
automatic exposure control system sets exposure times to incorporate changes in voltage and amperage to provide the desired
images at the best exposures possible (Fig. 3-45).
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Image Intensifier and Detector
After the x-rays have penetrated the body (Figs. 3-46 and 3-47), the
partially absorbed beams are cast in a shadow fashion on the input
screen of the II or flat-panel detector. The II converts the invisible x-ray
image into a visual image. Each x-ray photon hits the phosphoruscovered plate of the intensifier resulting in a light particle that is
detected, the position and intensity of which are noted. The sum of all
events produces an image for video. Image intensifiers are equipped
with various-sized image fields that alter the image resolution. In
general, the smaller the image field size, the sharper the resolution but
the higher the radiation dose. Smaller input screen diameters (5- to
7-inch screens) are better suited for coronar y angiography because of
their enhanced resolution. For more detailed work, such as percutaneous transluminal coronary angioplasty and other coronary interventions, 5-inch fields are commonly used by some operators. In contrast,
for large area examinations (i.e., left ventriculography, aortography, or
peripheral angiography), field diameters of 9 to 11 inches are used with
the known tradeoff of loss of resolution for small structures. The development of the flat-panel image detector offers efficient (low-dose)
x-ray image acquisition and better image clarity.
Image Distortion
Magnification
The x-ray image casts an x-ray shadow onto the image intensifier. The
distance of the object from the panel determines the image sharpness
or resolution. Figure 3-48 displays the effect of the object–screen distance on image quality. When an object is held close to the surface
on which the shadow falls, the image is sharp. The farther the object
is moved away from this surface, the larger and more indistinct the
image becomes. When the II is closest to the chest wall and the heart,
the image is sharp. When the heart is far away from the II and closer
to the x-ray source, the image is magnified but poorly defined. Increasing the distance of the heart to the II also requires more kilovoltage to
produce the image and further reduces image quality. Increased magnification increases the radiation exposure required to produce the
magnified image. Figure 3-49 shows the effects of increasing image
size on radiation dosing. The closer the patient is to the source without
moving the II, the greater the spread of the beam and higher the radiation exposure. Keep the II close to the patient whenever possible.
Minimizing the angulation of the C-arm also reduces x-ray exposure
(Fig. 3-50).
Foreshortening
Distortion of the object’s perspective is called foreshortening. Figure
3-51 displays the effects of the shadow cast by an object, such as a
pencil, that has a concentric narrowing (similar to an artery stenosis)
in the middle portion. The foreshortening (change of true length) of
the pencil causes the image to change depending on the axis in relation to the beam of the x-ray. When the pencil’s long axis is perpendicular to the image plane (parallel to the x-ray beam), all contour
details are lost, and the shadow is seen as a dot. When the longitudinal
axis is seen at an oblique angle, the length shadow is foreshortened,
and when the axis is perpendicular to the x-ray beam (parallel to the
image plane), a full and true image of the length and contour details
can be seen. Because of foreshortening, an angiographic narrowing
that may appear severe in one projection may not appear at all or may
seem significantly less severe in other projections. For this reason,
multiple projections are used to characterize the severity of lesions
within the coronar y tree.
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Coronary Angiography and Ventriculography 161
(A) X-ray photon source
(E) Patient
(C) Scatter radiation
(B) Grid
(D) Primary radiation
A
Object Housing Focusing electrodes
Optical
relay
X-rays
Detector
B
Figure 3- 46
X-ray photon source; B, grid; C, scatter radiation; D, primary radiation; E,
patient. Scatter radiation is reduced by grid in front of the II. B, Inner
mechanisms of the II. (A, From King SB, Douglas JS Jr: Coronary angiography
and angioplasty, New York, 1985, McGraw-Hill.)
screen
A, The grid on the image intensifier (II) aligns the beams. A,
Photocathode
Viewing screen
TV camera
Image
distributor
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A
Coronary Angiography and Ventriculography
Scintillator
Photodiode
X-ray
X-ray
Light
B
Figure 3-47 A, Flat-panel image intensifier (II). B, Screen of flat panel
showing how x-ray triggers photodiode to produce digital signal that is
transmitted and reconver ted into x-ray image.
The best practices to maximize image quality and reduce radia-
tion exposure are as follows:
1. The II/flat-plate detector should be as close to the patient’s chest as
possible. This position optimizes the image detail and decreases
scatter radiation (see tube height and radiation exposure).
2. All ECG electrodes, lead wires, metal snaps on the patient’s gown,
and jewelry should be out of the field of view before the start of the
procedure. Keeping the IV lines and wires from hanging down
under the table prevents the x-ray tube from pulling out a lead or
IV tube when rotating around the patient.
3. Use of the collimators (shutters) is mandatory. The operator should
focus on the exact area of interest to be imaged and eliminate
unwanted lung field brightness. This helps optimize settings for the
automatic brightness control system.
4. Minimize the number of cineangiograms obtained to only those
that are necessary. Maximize use of newer features of angiographic systems, such as “fluro save,” that save images obtained
during fluoroscopic imaging without having to use higher-radiation
cineangiography.
5. Use the ceiling mounted screen and table-side “skirt” to block
scatter radiation from above and below the table
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