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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3597_Библиотеки_им_академика_М_И_Перельмана
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192 4 —
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ECG
40 mm Hg
LA
LV
Hemodynamic Data
0
CF
1 cm = 3.9 mm Hg
9.46 cm
3.4 cm
9.46 • CF
3.4
2
= 10.85 mm HgMVG
Area
DFP
Figure 4-7 Hemodynamic tracing used to calculate mitral valve area (MVA).
Shaded area, Diastolic mean valvular gradient (MVG) surrounded by the
diastolic filling period (DFP). CF, Correction factor or scale factor; DFP, diastolic filling period; ECG, electrocardiogram; LA, left atrial pressure; LV, left
ventricular pressure (scale 0 to 40 mm Hg); MVG, mean valvular gradient.
DFP
Step 2. Measure diastolic filling period (DFP).
DFP cm then convert to time
=
3 4
. ( )
cm sec/ cm second
× =
3 4 1 10 0 34
. .
Step 3. Convert planimetered area to mean diastolic pressure
gradient.
mm Hg/ cm
3 9 1
.
MVG cm
2
.
3 4
cm
.
10 85
.
mm Hg= × =9 46
Step 4. Compute mitral valve flow. For the mitral gradient (similar
to AVAs), DFP is in centimeters at this point, owing to scale factor.
Flow
CO
=
DFP HR
3500
=
77 2
2
=
×
0 34 80
128 7..= mL/min
mL/min
3500
s/beat bpm
. .
×
=
3500
×
0 34 80
Step 5. Compute MVA.
Mitral value flow
MVA
=
×
0 44 44 3 10 85
. . .
128 7
=
0 85 44 3 3 3
.
× ×
. . .
=
128
124 3
..
7
= cm
.
1 0
2
.
Notes on Mitral Valve Gradient
Obtaining an accurate PCWP is crucial (see earlier discussion about
PCW accuracy; see Fig. 4-3, A). Use of direct LA pressure from transseptal measurement is the most accurate method. Trans-septal catheterization will confirm pressure gradients, especially for suspected
prosthetic mitral stenosis. However, if the PCWP-LV pressure tracings show no significant gradients, trans-septal catheterization is
unnecessary.
Simplified Mitral Valve Gradient Calculation by
Cui et al
Cui et al simplified estimation of the mitral valve gradient and thus
simplified the calculation of MVA from hemodynamic tracings.
Because the mean mitral valve gradient is the pressure difference
between the mean left atrium pressure (MLAP) and mean left ventricular pressure (MLVP) during diastole (i.e., MLVG = MLAP − MLVP),
the computation of the mean mitral valve gradient depends on
simply knowing the MLVP. The MLAP is easily obtained from the
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Hemodynamic Data 193
LV
LA
LVEDP
Baseline
Figure 4-8 Cui method to calculate mitral valve gradient from hemody-
namic tracings. Left ventricular (LV) and left atrial (LA) pressures are superimposed. The LV-LA gradient is triangular in shape, representing half of the
rectangle delineated by A and B, diastolic filling period (DFP); C, left ventricular end-diastolic pressure (LVEDP); D, mitral value closing; and E, mitral value
opening. (From Cui W, Dai W, Zhang G: A new simplified method for calculating mean mitral pressure gradient. Catheter Cardiovasc Interv 70[5]:754–
757, 2007.)
LV
E
LA
D
C
A
LVEDP
B
DFP
electronically meaned LA signal on the hemodynamic recorder. The
area under the LV pressure during diastole is roughly a triangle with
the three corners formed from the intersections of the DFP starting
and ending points (mitral valve closure and opening) marking the
vertical lines intersecting with the LV pressure line (rising diagonally
across diastole; Fig. 4-8). This triangular area can be estimated from
the rectangular area LVEDP × DFP divided by 2. Thus, the MLVP is
equal to the LVEDP/2. From this key calculation, the mitral valve gradient is therefore simplified as
MVG MLAP LVEDP/
2
There is strong correspondence between MVAs calculated by the
Gorlin and Hakki formulae, both before and after mitral balloon valvuloplasty, with an error of estimates at 1.6 mm Hg. The Cui mitral
valve gradient slightly overestimated the gradient before but not after
mitral valvuloplasty. The Hakki formula significantly underestimated
mitral valve gradients after mitral balloon valvuloplasty. Unlike Hakki,
the Cui mitral valve gradient was not affected by mitral regurgitation,
Ao insufficiency, AF, or HR.
Although simple, the Cui mitral valve gradient still has potential
problems. HR changes will affect the shape of the triangular area
under the LV pressure curve, and thus, tachycardia may cause a potential overestimation of valve severity.
Tricuspid Valve Gradients
Because small gradients (5 mm Hg) across the tricuspid valve may
lead to significant clinical symptoms, precise measurement of hemodynamics through two large-lumen catheters may be required. Match
pressures through two catheters (or through the two lumens of a
balloon-tipped catheter if correctly positioned) before placement in
the RA and RV to avoid technical error. The Gorlin valve area formula
has not been validated for the tricuspid or pulmonic valves.
Measurement of Cardiac Output
In the cardiac catheterization laboratory, CO is determined by one of
two techniques: (1) Fick, with measurement of oxygen consumption
(see earlier) or (2) indicator dilution (TD, using a PAC; see Chapter 1).
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Table 4 -1
Hemodynamic Data
Cardiac Shunt Locations
Location
Atrial Septal Defects
Primum (low) RA, RV
Secundum (mid) RA
Sinus venosus (high) R A
Partial anomalous pulmonary venous return
(pulmonary veins entering RA)
Ventricular Septal Defects
Membranous (high) RV
Muscular (mid) RV
Apical (low) RV
Aorticopulmonary window (connection of aorta
to PA)
Patent ductus ar teriosus (normally closed
Ao- PA connection at birth)
Ao, Aortic; PA, pulmonary arter y; RA, right atrium; RV, right ventricle.
Earliest Step -Up Location
(for Left-to -Right Shunts)
RA
PA
PA
Intracardiac Shunts
A shunt is an abnormal communication between the left- and rightheart chambers. The direction of blood flowing through the shunt is
left to right, right to left, or sometimes bidirectional. In the absence of
shunting, the pulmonary blood flow (right side of the heart) is equal
to the systemic blood flow. Table 4-1 lists intracardiac shunt locations.
A left-to-right shunt increases the amount of blood to the right side of
the heart and increases pulmonary blood flow, now the sum of the
systemic blood flow plus shunt flow. With a right-to-left shunt, the
amount of blood shunted from the right side of the heart to the left is
added to that normally ejected into the systemic circulation, making
systemic blood flow greater than pulmonary blood flow by the amount
of blood flow in the shunt (Fig. 4-9). Intracardiac shunts have been
evaluated by oximetry, radionuclide perfusion, and Doppler echo flow
measurements. Oximetry is the most common method used in the
catheterization laboratory.
Oximetry Procedure: Diagnostic
Saturation Run
A diagnostic “saturation run” uses 1- to 3-mL heparinized syringes to
obtain blood from the superior vena cava (SVC), inferior vena cava
(IVC), RA, RV, and PA in a rapid, organized manner. A standard
balloon-tipped PA flotation catheter is satisfactory, but a large-bore
end-hole or side-hole (multipurpose) catheter performs better rapid
sampling. Heparinize saturation syringes with <
prepare the labels and list of sample sites in advance (Box 4-10).
The saturation run begins after diagnostic hemodynamic data
and CO have been obtained and before right-sided heart pull back.
With the catheter positioned in the right or left PA, measure oxygen
consumption (Fick method). On catheter pull back, one operator
manipulates the catheter under fluoroscopic and pressure control
while an assistant aspirates the blood samples at each location along
the run. Each new sample is obtained after several milliliters of blood
have been withdrawn and discarded so that blood left from the previous catheter sampling location will not contaminate the new blood
oxygen. The entire diagnostic run should take approximately 5 to 7
minutes.
0.5 mL. In addition,
Body
Lungs
L R
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Hemodynamic Data 195
EPBF = PBF +
shunt flow
SVC
L R = PBF – EPBF
IVC
R
CS
L = SBF – EPBF
PV
Right
heart
O2 cons.
PVO
– MVO
2
R L
EPBF EPBF
2
Shunt
R L
Shunt
L – R
Shunt
R L
R L
=
EPBF
Left
heart
PA
Ao
R L
ESBF = SBF +
shunt flow
2
O
cons.
2
SAO2 – MVO
2
Figure 4-9
Lungs Body
PBF = SBF =
O2 cons.
PVO2 – PAO
Schematic diagram for right-to -lef t and left-to-right shunting
across the hear t. Ao, Aorta; CS, coronary sinus; EPBF, ef fective pulmonar y
blood flow; ESBF, ef fective systemic blood flow; IVC, inferior vena cava;
L, left; MVO2, mixed venous oxygen saturation or content; O2 cons., oxygen
consumption; PA, pulmonary ar tery; PAO2, pulmonary arterial oxygen saturation or content; PBF, pulmonary blood flow; PVO2, pulmonary venous oxygen
saturation or content; PV, pulmonary vein; R, right; SAO2, systemic ar terial
oxygen saturation or content; SBF, systemic blood flow; SVC, superior vena
cava.
Box 4 -10 Sample Sites for Oxygen Saturations During
Diagnostic Saturation Run
Right Side of the Heart
Left PA
Right PA
Main PA
PA above pulmonary valve (PApV)
RV below pulmonar y valve (RVpV)
RV (mid)
RV (apex)
RV at tricuspid valve (RVTV)
RA at tricuspid valve (RATV)
RA (mid)
SVC (high)
SVC (low)
RA (high)
RA (low)
IVC (high, just beneath heart, above hepatic vein)
IVC (low, above renal vein, but below hepatic vein)
Left Side of the Heart
Arterial saturation, Ao
If possible, cross ASD, pulmonar y vein saturation
Patent foramen ovale or LA
Ao, Aortic; ASD, atrial septal def ect; IVC, inferior vena cava; LA, lef t atr ium;
PA, p ulmonar y arter y; RA, right atrium; RV, right ventricle; SVC, superior vena cava.
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Table 4 -2
Hemodynamic Data
Oxygen Saturation Values for Shunt Detection
Level of Shunt
Atrial (SVC/IVC to right aor ta)
Ventricular
Great vessel
IVC, Inferior vena cava; SVC, superior vena cava.
= (3 SVC + 1 IVC)/4 and difference from PA should be ≤7% normally.
MVO
2
*Difference betwe en distal and proximal chamber; for example, for atrial septal
defect (ASD).
Significant Step- Up
Difference* O2% Saturation
≥7
≥5
≥5
Oxygen Step-Up: Evidence of a Shunt
A left-to-right shunt is suggested when an oxygen step-up or increase
of oxygen content in that chamber or vessel exceeds that of a proximal
compartment. A step-up in oxygen saturation at the PA by more than
7% above the RA saturation is indicative of a left-to-right shunt at the
atrial level (Table 4-2). Similarly, the desaturation of arterialized blood
samples from the left heart chambers and aorta suggests a right-to-left
shunt. In determining the site of the right-to-left shunt, sequential sampling can be made from the LA, LV, and aorta.
Mixed venous blood is assumed to be fully mixed PA blood. With
a left-to-right shunt, measure mixed venous blood one chamber proximal to the step-up. In the case of an atrial septal defect (ASD), compute
the mixed venous oxygen content from the weighted average of vena
caval blood (i.e., as [3 × SVC + IVC]/4). When pulmonary venous blood
) per-
centage saturation is 95%.
2
Shunt Calculation
The Fick or left-sided indicator dilution methods of CO determination
are used to measure systemic flow (see Fig. 4-9). Using the Fick
method, the following formulae apply:
1. Systemic flow
O consumption mL/min
Q L/min
( )
s
=
2
arterial mixed venous O co
( )
−
2. Pulmonary flow, QP (L/min)
O consumption mL/min
pulmonary venous pulmonary arterial
( )−
2
Thus, the effective pulmonary blood flow (EPBF) is
O consumption mL/min
Q
=
EPB
pulmonary venous mixed venous O
( )
2
−
Normally, the EPBF is equal to the systemic blood flow. In a leftto-right shunt, EPBF is increased (by the amount of the shunt) as
follows:
EPBF systemic flow shunt flow left-to-right
In a right-to-left shunt, EPBF is decreased (by the amount of the
shunt):
EPBF systemic flow shunt flow right-to-left
Shunt volume is determined by use of equations 1 and 2 (later).
The shunt fraction is the ratio of pulmonary to systemic flow
(called Q
, where Q is flow, P is pulmonary, and S is systemic)
p/Qs
for a left-to-right shunt. Flow ratios (Q
( )
nntent
2
( )
OO content
2
( )
content
22
( )
( )
) >1.5 often require closure.
p/Qs
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Hemodynamic Data 197
Example for Left-to-Right Shunt Atrial Septal
Defect Calculation
Data obtained at catheterization are:
Location Saturation (%) Location Saturation (%)
Arterial 92 PA 81
SVC 71 PV 98
Mid R A 85 IVC 70
Low R A 68
Hemoglobin g
O consumption mL/min
2
==13
210
1. Compute O2 content.
Arterial O content mL O /g g/dL
2 2
0 98 1 36 14 1 10
= × × ×
. . .
mL O /L
188
=
2
Mixed venous O2 content (use estimate of mixed venous oxygen
saturation):
3 1
SVC IVC
+
71 1 36 14 1 10 136
Pulmonary artery O content mL O /g g/dL
Pulmonary vein O content mL O /g g/dL
× × × =. .mL O /g g/dL mL O /L
for mixed venous oxygen saturation:
4
(. . . . )
71 71 71 70
+ + +
4
2 2
0 81 1 36 14 1 10= × × ×
2 2
2 2
( . . . )
=
11552mL O /L
0 98 1 36 14 1 10
= × × ×
( . . . )
18
=
882mL O /L
=
.
0 71
2. Compute systemic flow (equation 1).
225
mL O /min
( )
188 136
2
−
mL O /L
225
= = =
52
2
.
4 3
Q L/min
S
3. Compute pulmonary flow (equation 2).
225
mL O /min
( )
188 155
−
2
mL O /L
225
= = =
33
2
.
6 8
Q
P
4. Compute.
6 8
.
Q
P
= =
1 6
Q
S
4 3
.
.
The L→R shunt is 6.8 L/min − 4.3 L/min or 2.5 L/min.
If absolute flows are not required, the QP/QS ratio can be deter-
mined using saturations only as follows:
QQSAO MVO
P
S
−
2
=
−
PVO PAO
2 2
2
where SAO2 is systemic arterial oxygen saturation, PVO2 is pulmonary
venous oxygen saturation, MVO
and PAO
is pulmonary arterial oxygen saturation.
2
is mixed venous oxygen saturation,
2
Using saturation data from the example of left-to-right shunt:
−
98 71
Q
P
=
Q
S
= =
−
98 812717
1 6.
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Hemodynamic Data
Example for Right-to-Left Shunt
Data obtained at catheterization are:
Location Saturation (%) Location Saturation (%)
Arterial 89 L A 88
SVC 81 PA 82
Mid R A 83 PV 96
Low R A 82 IVC 70
Hemoglobin g
O consumption mL/min
2
==15
195
1. Compute O2 content.
Arterial = (0.89 ×
15 g/100 mL × 1.36 mL O2/g × 10) = 182 mL O2/L
Mixed venous (estimated mixed venous) saturation = (.81 + .81 +
.81 + .70) 4 = 0.78
Mixed venous = (0.78 ×
Pulmonary arterial = (0.82 ×
=
167 mL O2/L
Pulmonary venous = (0.96 ×
=
196 mL O2/L
15 g/dL × 1.36 mL O2/g × 10) = 159 mL O2/L
15 g/dL × 1.36 mL O2/g × 10)
15 g/dL × 1.36 mL O2/g × 10)
2. Compute systemic flow (equation 1).
O consumption
arterial mixed venous O content
( )−
2
2
=
ml O /min
195
2
(( )182 1592− ml O /L
3. Compute pulmonary blood flow (equation 2).
O consumption
2
( )− tt
pulmonary venous pulmonary arterial O conten
4. Compute Q
=
( )
=
( )
mL O /min
195
( )
196 167
.
EPB
pulmonary venous mixed venous O content
195
mml O /min
2
196 159
mL O /L
2
mL O /L
−
O consumption
2
−
5 3
.−=
2
.
=
6 7
2
L
2
L/min=
2
Shunt calculations:
Left-right shunt Q Q L/min
Right-to-left shu
= − = − =6 7 5 3 1 4. . .
P EPB
nnt Q Q L/min
= − = − =8 5 5 3 3 2. . .
S EPB
Limitations of the Oximetric Technique
1. Because of its low sensitivity, oximetry may fail to detect small (<1)
shunts.
2. The application of the Fick principle to calculate blood flow pre-
sumes a steady state during the diagnostic run and measurement
of oxygen consumption (i.e., timely collection of saturation sample
within a period during which oxygen consumption and CO are
stable).
3. The oximetry method also assumes that complete mixing is
achieved instantly and that blood samples obtained are representative of blood in the respective compartment.
4. The rate of systemic blood flow is important in detecting a
shunt by oximetry. A high systemic flow tends to equalize the AVO
difference across a given vascular bed. In the presence of elevated
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systemic blood flow, the mixed venous oxygen saturation is higher
than normal and intrachamber variability caused by streaming is
reduced. In contrast, when systemic blood flow and mixed venous
oxygen saturation are low, a larger step-up must be detected before
a significant left-to-right shunt is diagnosed.
4 —
Hemodynamic Data 199
Angiography
Angiography is a qualitative method used to localize either left-to-right
or right-to-left shunts. The shunt can be detected by injection of x-ray
contrast medium into the closest proximal chamber. The left anterior
oblique view with cranial angulation puts the interatrial and interventricular septae on face (i.e., on edge), which provides an ideal view
for detection of contrast medium passage across the atrial and ventricular septal defects (see Chapter 3 for angiographic views to visualize an intracardiac shunt).
Equipment Used for
Hemodynamic Study
Pressure Manifold and Setup
The optimal set of transducers, tubing, and manifolds for any laboratory is that which is cost effective, familiar, accurate, and simple to
use. Several varieties of disposable manifolds exist (Fig. 4-10) that can
be coupled to transducers positioned either on the manifold or at the
side of the catheterization table. For research studies, special
transducer-tipped micromanometer pressure catheters and pressure
sensor guidewires are used to obtain high-fidelity pressure recordings.
High-fidelity recordings are not necessary for routine clinical hemodynamic studies; accurate measurements can be obtained with fluidfilled systems if appropriate precautions in the setup are taken.
Some clear plastic manifolds have several ports: (1) pressure
and zero line, (2) saline flush, (3) contrast media at the third, and
(4) closed waste line (to minimize contamination of personnel and
laboratory). A three-port manifold combines a saline flush and waste
port with a one-way valve.
Figure 4-10 Pressure manifold used for coronary angiography. At the end
of the manifold, the connection of the manifold to the catheter has a swivel
connector. 1, Stopcock to pressure; 2, saline flush line; 3, contrast line;
4, waste line with a one-way valve.
4
1 2 3
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200 mm Hg
100 cm/sec
Figure 4-11 Hemodynamic tracing showing the effect of an air bubble in
a pressure line. Note the change in hemodynamic waveform after the bubble
is flushed: The ringing artifact (sharp points at arrows) is eliminated and fine
detail of precise pressure restored. ECG, Electrocardiogram; LV, lef t
ventricle.
Hemodynamic Data
ECG
LV
0
Bubble
in line
After flushing
For best pressure waveforms, tubing should be short and stiff, with
the transducer as close to the catheter as possible. Tubing length from
the catheter to the transducer should also be minimized; longer tubing
contributes to more resonating or “ringing” artifacts (Fig. 4-11).
The zero level is set at mid chest (i.e., the measured anteroposterior diameter of the patient divided by 2 and added to the position of
the table). When the transducer is raised above zero level, pressure is
artificially lower. When the transducer is lower than zero, pressure
is artificially higher (Fig. 4-12). When abnormally low pressures are
seen initially, recheck the zero for proper positioning (at mid chest)
and check for air bubbles or loose connections.
Physiologic Recorder
The physiologic recorder system is now a digital system that processes
the hemodynamic and electrocardiographic signals from the transducers and pacing electrode catheters used in electrophysiologic
studies. The typical physiologic monitor/recorder is a multichannel
unit that can process, display, and record ECG signals, pressure tracings, and direct current (DC) inputs from external sources (e.g., TD).
The number of channels determines how many individual signals are
displayed and recorded simultaneously. For routine cardiac catheterization, one ECG signal and two to three pressure channels are normally recorded. In certain complex cases, such as electrophysiology
studies and cases with complex congenital or valvular heart disease,
it is common to use four to 18 channels.
Most recorders have an electronic calibration that allows the
operator to input an electronic pressure standard. This feature provides a convenient means for simulating pressure signals to calibrate
the display. An external standard pressure reference can be input from
a mercury manometer and the transducer calibrated to match the
input pressure.
Display Settings for Hemodynamic Data
The laboratory has many choices when setting the display for hemodynamic waveforms. These settings include timing lines, signal display
sweep speed, and pressure scale(s). The typical setting for a routine
case is 1-second time lines (i.e., one line each second). Use a faster
time line sequence for special studies or when a faster paper speed
is used. For most procedures, the sweep speed of the monitor is
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Hemodynamic Data 201
A
B
Figure 4 -12 A, To demonstrate the effect of zero position, a transducer
is connected to a fluid-filled tube and its stopcock is open to air. By lifting
either the tubing (as shown in the left hand) or the transducer, one can see
the zero move. B, The effect of first raising the tubing shows how zero offset
is affected by height on the table. The blue line goes up and then raising
the transduce to the same level produces the same effect. Set the zero at
bedside and keep the transducer fixed throughout the study.
25 mm/sec. Slower sweep speeds (10 and 5 mm/sec) are used to
examine changes in hemodynamics, such as respiratory variations in
RV/LV pressure, over longer periods of time. Faster speeds can help in
observing timing of diastolic and systolic pressures (e.g., LV and Ao;
LA and LV).
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