Section Four:
Pulmonary Artery Waveform Interpretation
All hemodynamic pressures and waveforms
are generated by pressure changes in the heart
caused by myocardial contraction (systole) and
relaxation/filling (diastole) phases of the cardiac
cycle. This mechanical activity of the heart is
generated in response to the electrical activity,
that is, the depolarization and repolarization of
myocardial cells. Interpretation of the
hemodynamic waveforms is dependent,
therefore, on the correlation of mechanical to
electrical activities using the ECG. There are
three categories of hemodynamic waveforms:
atrial, which includes RA, LA, and PA wedge;
ventricular, which includes left and right
ventricular; and arterial, which includes PA and
systemic aortic. The waveforms in each
category have similar characteristics because
they result from the same cardiac events. The
differences are in the pressure measurements
because of the different amount of pressure that
is generated in the right heart and the left side of
the heart.
Right Atrial Pressure
The RA is a low pressure chamber, receiving
blood volume passively from the vena cava.
The normal pressure is 2 – 6 mm Hg, which
reflects the mean RA pressure (RAP). Atrial
waveforms have three positive waves: a, c, and
v (Fig 8).
The a wave is caused by the increase in
atrial pressure during atrial contraction with
systole. The c wave, often not seen, reflects the
small increase in RAP associated with closure of
the tricuspid valve and early atrial diastole. The
v wave represents atrial diastole and the
increase In pressure caused by filling of the
atrium with blood. The v wave of RA diastole is
also affected by right ventricular contraction and
the bulging of the tricuspid valve up into the RA
after RA systole.
Accurate identification of the a, c, and v
waves requires correlation of the waveform with
the ECG. On the ECG, the P wave represents
discharge of the SA node and atrial
depolarization, which causes right atrial
contraction. Therefore, the a wave occurs after
the P wave and usually in the PR interval.
Measure the mean a wave to obtain the RA
pressure. The QRS complex represents
ventricular depolarization and causes ventricular
contraction. Simultaneously the RA relaxes and
fills with blood. The v wave generated by these
events thus falls after the QRS complex and in
the T to P interval. The c wave is not always
visible because of the small increase in pressure
caused in early diastole and with tricuspid valve
closure. If it is visible, the c wave occurs
between the a and v waves.
. Figure 8. Normal components of RA (CVP) waveform
Section Four – PA Waveform Interpretation
27
Reading RA Waveforms
Method 1 – Mean A Wave
Method 2 – End QRS
Most reliable, but must have a P wave in order
to have normal a waves:
Useful when a wave is not present or abnormal,
but not as accurate:
 Locate the beginning of the a wave (correlates
with PR interval)
 Find the end of the QRS complex
 Identify the top and the bottom of the a wave
and average the 2 values to obtain the RA
pressure.
 Draw a line straight down to RA wave
 Where line intersects RA wave, that is the RA
pressure
Examine examples below.
Method 1 – Mean A Wave
Method 2 –End QRS
RA pressure = 12 mm Hg
Section Four – PA Waveform Interpretation
28
It is important to obtain the RA pressure by
examining the RA waveform and correlating it
with the ECG in order to ensure the accuracy of
the values. Obtaining values solely by taking
the digital value on the monitor may result in
inaccurate determinations.
Significance of the Right Atrial
Pressure
The normal right atrial pressure is 2-6 mm
Hg. It reflects the filling pressure of the right
ventricle, or right ventricular preload. Causes of
abnormal RA pressures include:
Low Right Atrial Pressure

Hypovolemia

Vasodilatation
Fluid overload

Right ventricular failure

Pulmonary hypertension

Left-ventricular failure
As the PA catheter is advanced from the RA
into the right ventricle, the waveform generated
has a distinctive square root configuration
(Fig.9).
RV Systole
 An initial rapid rise in pressure represents
isovolumetric contraction.
 Follows the QRS complex, before the end of
the T wave of the ECG.
RV Diastole
 Pulmonic valve closes, and the rightventricular pressure rapidly decreases creating
a diastolic dip.
 Falls near the end of the QRS on the ECG.
High Right Atrial Pressure

Right Ventricular Pressure
 The point on the waveform just prior to the
rapid rise in pressure represents rightventricular end-diastole.
 The right-ventricular end diastolic pressure
should be close to or equal to the RA, CVP.
Figure 9. Normal RV pressure waveform.
Section Four – PA Waveform Interpretation
29
Significance of Right Ventricular
Pressure
Low Right Ventricular Pressure

Hypovolemia
The right ventricle is considered a lowpressure chamber. Right-ventricular systolic
pressure is normally 20 to 30 mm Hg because
the right ventricle needs to generate only
enough pressure to open the pulmonic valve
and move blood through the low-pressure
pulmonary vasculature

Vasodilatation
High Right Ventricular Pressure

Right ventricular failure

Pulmonary hypertension

Pulmonic stenosis
Right-ventricular end-diastolic pressure is
usually 0-6 mm Hg, equal to the RA pressure as
the tricuspid valve is open. Causes of abnormal
RV pressure includes:


Pulmonary Artery Pressure
The pulmonary vasculature is a relatively
low-resistance and low-pressure system in
normal individuals. PA systolic pressure and the
peak of the PA waveform are generated by rightventricular systolic ejection; therefore, the PA
and right-ventricular systolic pressure are the
same. The PA waveform characteristics are
similar to the systemic arterial waveform (see
Figure 10).
PA Systole
 Measure the peak of the systolic waveform to
obtain the PA systolic pressure.
 Systole is found after the QRS complex, but
before the end of the T wave.
 Normal PA systole is 20 – 30 mm Hg.
Dicrotic Notch
 Found in the downward slope of the PA
waveform.
 Occurs after systole but before diastole,
usually after the T wave.
 Corresponds with pulmonic valve closure at
the beginning of right-ventricular diastole and
is the beginning of the PA diastolic phase.
PA Diastole
 PA diastolic pressure theoretically and in
absolutely normal conditions is an indirect
measure of LV pressure because the
pulmonary vasculature, left atrium, and open
mitral valve allow equalization of pressure
from the left ventricle back to the tip of the PA
catheter.
 Measure the PA diastolic pressure just before
the upstroke of the systolic waveform.
 PA diastole corresponds with the end of the
QRS.
 Normal PA diastolic pressure is ~ 8 – 15 mm
Hg.
Section Four – PA Waveform Interpretation
30
Figure 10. PA pressure waveform showing phases of systole, dicrotic notch (pulmonic valve closure),
and end-diastole.
Significance of Pulmonary Artery
Pressures
Normal PA systolic pressure is 20 to 30 mm
Hg and is equal to right-ventricular systolic
pressure. Normal PA diastolic pressure is 8 to
15 mm Hg and is usually about the same as the
left atrial pressure because there is no valve
between the left atrium and the pulmonary
circulation. The normal PA mean pressure is 10
to 20 mm Hg. Abnormal PA pressures may be
due to:
Low Pulmonary Artery Pressure

Hypovolemia
High Pulmonary Artery Pressure

Pulmonary hypertension

Left ventricular failure
Pulmonary Capillary Wedge Pressure
When the PA catheter is properly positioned, the
pulmonary capillary wedge pressure (PCWP) is
obtained by inflating the balloon at the catheter
tip. The balloon occludes forward flow in the
branch of the PA, creating a static column of
blood from that portion of the PA through the left
atrium, an open mitral valve during diastole, and
the left ventricle. In this way the PCWP reflects
left ventricular end-diastolic pressure. (See
Figure 11A below.)
Inflation of the PA balloon causes the PA
waveform on the monitor to become a PCWP
tracing. No more than 1.5 mL of air is used to
inflate the balloon. If less than 1 mL of air
generates a PCWP tracing, the PA catheter has
migrated distally and needs to be withdrawn
slightly by the physician or RN (check policy), for
proper placement. If spontaneous wedge
occurs the physician should be notified and
measures taken immediately to reposition. (See
table on page 44.)
Section Four – PA Waveform Interpretation
31
Figure 11A. PA catheter, chamber pressures, relationship to left heart.
PCWP Waveform
The PCWP tracing has a, c, and v waves
(Fig 11A). The electrical and mechanical events
of the heart generating these waves are identical
to those of the RA waveform, except that the
PCWP waveform reflects activity from the left
side of the heart. The a wave is caused by LA
contraction, and the v wave corresponds with LV
contraction and left atrial filling. The c wave is
rarely visible on the PCWP tracing.
As with the RA, RV and PA pressures, it is
important to obtain PCWP measurements from a
graphic waveform strip with simultaneous ECG
in order to ensure utmost accuracy. Two
methods for accurate interpretation will be
reviewed.
larger or smaller. It is the mean a wave that
best reflects the LVEDP and should be used to
interpret the PCWP reading.
 The a wave is found near the end or after the
QRS.
 Giant a waves may be due to arrhythmias
such as AV block, AV asynchrony found in
paced rhythms or mitral stenosis.
 The v wave is due to blood filling the LA with a
closed mitral valve.
 The v wave is located after the T wave, in the
T-P interval.
 Giant v waves may occur due to mitral
regurgitation or in problems of ventricular wall
compliance.
 The a wave occurs during LA contraction,
often the same size as the v wave, but may be
Methods for Reading PCWPs
Method 1 – Mean of the A Wave
 Most reliable method (see Figure 11B).
 The a wave is usually easy to identify and is
present unless atrial contraction is absent,
e.g. atrial fibrillation.
 The a wave is correlated with the end of the
QRS complex.
 Locate the top and bottom of the a wave and
average the 2 values to obtain the PCWP.
Method 2 – Z Point
 Useful when the a wave is absent or
abnormal.
 Assumes that the left ventricular end diastolic
pressure (LVEDP) is 0.08 - 0.12 seconds after
initiation of the QRS, end QRS.
 At the end of the QRS, draw a line straight
down and take the reading. (See Figure 11c
on the next page.)
Section Four – PA Waveform Interpretation
32
Differences in CVP and PCWP ECG Correlation
Wave
RA, CVP
PCWP
A

In the PR interval

End of QRS
V

Near end of T wave

In the TP interval
Method 1 – Mean of the A Wave
Figure 11 B. Normal pulmonary capillary wedge pressure waveform showing a and v waves and x and y
descents. The top of the a wave (15) and bottom (8) are averaged to get the mean PCWP (15+8=23,
232=11.5)
Method 2 – Z Point (End QRS)
Figure 11 C. There are no clear P waves, therefore read the PCWP at the end of the QRS complex. The
v waves are larger than the a waves in the tracing.
Section Four – PA Waveform Interpretation
33
Significance of PCWP
The PCWP more closely measures left
atrial and ventricular end- diastolic pressure
than the PA diastolic pressure because
balloon inflation halts blood flow past the
catheter tip and thereby decreases the
influence of pulmonary vascular resistance
on the pressure reading. Normal PCWP is 8
to 12 mm Hg. Abnormal PCWP may be due
to:
Low PCWP

Hypovolemia

Vasodilatation
Elevated PCWP (A Waves and V Waves)

Hypervolemia

Left heart failure

Cardiac tamponade
Elevated V waves

Mitral valve regurgitation, insufficiency

Acute ischemia
Normally PA diastole (PAD) closely
represents left ventricular end-diastolic
pressure, although when pulmonary
hypertension is present the PA diastolic
pressure may be higher than the PCWP.
Elevated PCWP frequently is due to LV
dysfunction or hypervolemia. In some
cases, such as acute respiratory distress
syndrome or mechanical ventilator settings
that generate extremely high intrathoracic
pressure, PCWP will be elevated because of
noncardiogenic causes. In these cases,
however, the PA diastolic pressure will be
greater than the PCWP.
When the PA catheter is inserted, the
relationship of the PAD and PCWP should
be noted. If the PAD correlates with the
PCWP (as it should), a sudden increase in
the PAD would alert the RN to check the
PCWP. When the PAD is higher than the
PCWP, the LVEDP can only be obtained by
wedging the catheter. See Figure 11d and
11e below to see the usual PAD/PCWP
relationship and the PAD/PCWP in the
presence of conditions that cause
pulmonary hypertension.
PAD/PCWP Relationship
Note: The PCWP cannot be higher than
the PAD.
Figure 11e. The PAD is 50, the PCWP
is 20, much less than the PAD.
Figure 11d. The PAD is 20, the PCWP is
~18, similar to the PAD.
Review material from this section by
completing the Self-Test that follows, and
then compare your answers with those
given.
Section Four – PA Waveform Interpretation
34
Section Four:
Pulmonary Artery Waveform Interpretation
Self-Test
Fill in the blanks with one of the following:

CVP, RA

RV systolic

PAD
Normally, the right ventricular diastolic pressure is ~ the same as the _____; the PA systolic
pressure is ~ the same as the _____; and the PCWP is ~ the same as the _____.
It is important to correlate the hemodynamic waveform with the ECG and to know where the
reading should be taken in order to get accurate data. Fill in the following:

RA, CVP is best read at the ___ wave, which correlates with the __________ on the ECG.

RV end-diastole is read just prior to __________ ejection, which correlates with
the__________ on the ECG.

PA diastole is read just prior to __________ ejection, which correlates with the
____________ on the ECG.

PCWP is best read at the ___ wave, which correlates with __________________ on the
ECG.
Match the anatomic location with its normal pressure:
_____ Aortic
a) 2-8 mm Hg
_____ Pulmonary artery
b) 8-12 mm Hg
_____ PCWP
c) 20/8 – 30/12
_____ Right atrial, CVP
d) 20/0 – 30/5
_____ Right ventricular
e) 100/60 – 140/80
Match the pressures with the possible corresponding conditions:
___ PA 50/30, PCWP 10
a) Left ventricular failure
___ PA 20/10, PCWP 10
heart function
b) Pulmonary hypertension, normal left
___ PA 35/22, PCWP 28
c) Hypovolemia
___ PA 32/25, PCWP 23
d) Normal
___ PA 18/3, PCWP 2
e) Impossible reading
Section Four – PA Waveform Interpretation
35
Identify the following waveforms and document the pressures:
1) Waveform: _________Pressure: ________
2) Waveform:________ Pressure: _________
Section Four – PA Waveform Interpretation
36
3) Waveform: _______Pressure: _________
4)
Waveform: ____________ Pressure: ___________
Section Four – PA Waveform Interpretation
37
Section Four: Waveform Interpretation
Self-Test
Answers
Fill in the blanks with one of the following:

CVP, RA

RV systolic

PAD
Normally, the right ventricular diastolic pressure is ~ the same as the CVP ; the PA systolic
pressure is ~ the same as the RV systolic ; and the PCWP is ~ the same as the PAD .
It is important to correlate the hemodynamic waveform with the ECG and to know where the
reading should be taken in order to get accurate data. Fill in the following:

RA, CVP is best read at the a wave, which correlates with the PR interval on the ECG.

RV end-diastole is read just prior to systolic ejection, which correlates with the end of
the QRS on the ECG.

PA diastole is read just prior to systolic ejection, which correlates with the end of the
QRS on the ECG.

PCWP is best read at the a wave, which correlates with end of QRS on the ECG.
Match the anatomic location with its normal pressure:
E Aortic
a) 2-6 mm Hg
C Pulmonary artery
b) 8-12 mm Hg
B PCWP
c) 20/8 – 30/12
A Right atrial, CVP
d) 20/0 – 30/5
D Right ventricular
e) 100/60 – 140/80
Match the pressures with the possible corresponding conditions:
B PA 50/30, PCWP 10
a) Left ventricular failure
D PA 20/10, PCWP 10
function
b) Pulmonary hypertension, normal left heart
E PA 35/22, PCWP 28
c) Hypovolemia
A PA 32/25, PCWP 23
d) Normal
C PA 18/3, PCWP 2
e) Impossible reading
Section Four – PA Waveform Interpretation
38
ANSWERS TO WAVEFORMS:
1) Waveform:
PA
Pressure: 63/25 mm Hg
2) Waveform: RA (A wave in PR) Pressure: 7.5-8 mm Hg
Section Four – PA Waveform Interpretation
39
3) Waveform: RV
Pressure: 78/28 mm Hg
4) Waveform: PCWP Pressure: 10 mm Hg
Section Four – PA Waveform Interpretation
40
Section Four – PA Waveform Interpretation
41