Download Real-Time MR Imaging of Aortic Flow: Influence of Breathing on Left

Radiology
Cardiac Imaging
Rik J. van den Hout, MD†
Hildo J. Lamb, PhD
Joost G. van den Aardweg,
MD
Robert Schot, BSc
Paul Steendijk, PhD
Ernst E. van der Wall, MD
Jeroen J. Bax, MD
Albert de Roos, MD
Index terms:
Aorta, flow dynamics, 941.129416
Aorta, MR, 941.129416
Emphysema, 60.751
Heart, function, 52.619, 52.719
Heart, MR, 52.121416, 52.12144
Published online before print
10.1148/radiol.2292020559
Radiology 2003; 229:513–519
Abbreviations:
COPD ⫽ chronic obstructive
pulmonary disease
SV ⫽ stroke volume
1
From the Departments of Radiology
(R.J.v.d.H., H.J.L., E.E.v.d.W., A.d.R.),
Pulmonology (J.G.v.d.A., R.S.), and
Cardiology (P.S., J.J.B.), Leiden University Medical Center, Albinusdreef 2,
2333 ZA Leiden, the Netherlands.
From the 2001 RSNA scientific assembly. Received May 15, 2002; revision
requested July 15; final revision received February 12, 2003; accepted
March 28. Address correspondence
to H.J.L. (e-mail: [email protected]).
†
Deceased.
Author contributions:
Guarantors of integrity of entire study,
R.J.v.d.H., H.J.L., J.G.v.d.A., A.d.R.;
study concepts and design, R.J.v.d.H.,
H.J.L., J.G.v.d.A., R.S., A.d.R.; literature
research, R.J.v.d.H., H.J.L., J.G.v.d.A.,
J.J.B., A.d.R.; clinical studies, R.J.v.d.H.,
H.J.L., J.G.v.d.A., R.S., J.J.B., A.d.R.,
P.S.; data acquisition, R.J.v.d.H., H.J.L.,
J.G.v.d.A., R.S.; data analysis/interpretation, all authors; statistical analysis,
R.J.v.d.H., H.J.L., J.G.v.d.A., A.d.R.;
manuscript preparation and definition
of intellectual content, all authors;
manuscript editing, R.J.v.d.H., H.J.L.,
J.G.v.d.A., P.S., J.J.B., A.d.R.; manuscript revision/review, and final version approval, all authors
©
RSNA, 2003
Real-Time MR Imaging of
Aortic Flow: Influence of
Breathing on Left Ventricular
Stroke Volume in Chronic
Obstructive Pulmonary
Disease1
PURPOSE: To assess real-time changes of left ventricular stroke volume (SV) in
relation to the breathing pattern in healthy subjects and in patients with chronic
obstructive pulmonary disease (COPD).
MATERIALS AND METHODS: Real-time magnetic resonance (MR) imaging flow
measurements were performed in the ascending aorta of 10 healthy volunteers and
nine patients with severe COPD. Breathing maneuvers were registered with an
abdominal pressure belt, which was synchronized to the electrocardiographic signal
and the flow measurement. Healthy subjects performed normal breathing, deep
breathing, and the Valsalva maneuver. Patients with COPD performed spontaneous
breathing. Paired two-tailed Student t tests were used in healthy volunteers to assess
significant SV differences between normal breathing and deep breathing or the
Valsalva maneuver. The results of measurements in the patients with COPD were
compared with the results during normal breathing in healthy subjects with the
unpaired two-tailed Student t test.
RESULTS: In healthy subjects, SV decreased during inspiration and increased
during expiration (r2 ⫽ 0.78, P ⬍ .05). When compared with the SV during normal
breathing, mean SV did not change during deep breathing but declined during the
Valsalva maneuver (P ⬍ .05). The difference between minimal and maximal SVs (ie,
SV range) increased because of deep breathing or the Valsalva maneuver (P ⬍ .05).
In normal and deep breathing, velocity of SV elevation and velocity of SV decrease
were equal (which resulted in a ratio of 1), whereas during the Valsalva maneuver,
this value increased (P ⬍ .05). Spontaneous breathing in COPD resulted in SV
changes (P ⬍ .05) similar to those observed in healthy subjects who performed the
Valsalva maneuver.
CONCLUSION: Real-time MR imaging of aortic flow reveals physiologic flow
alterations, which are dependent on variations in the breathing pattern.
©
RSNA, 2003
Chronic obstructive pulmonary disease (COPD) has a high prevalence and morbidity and
is often associated with severe hemodynamic consequences (1). In patients with COPD,
expiratory intrathoracic pressures can be increased as a result of expiratory obstruction (2).
These pressure changes have a distinct influence on cardiac function (3). In combination
with other factors, such as hypoxemia and pulmonary hypertension, the heart is subject
to chronic hemodynamic and metabolic stress (4).
Intrathoracic blood flow toward and away from the heart is influenced by the cyclic
pressure changes that occur as a result of breathing (Fig 1). The variations in intrathoracic
pressure cause changes in caval flow affect the filling of the right ventricle (5). The
513
TABLE 1
Subject Characteristics
Radiology
Characteristic
Body surface area (m2)
Heart rate (beats per minute)
Forced expiratory volume in 1 sec
(percentage predicted)*
PaO2 (mm Hg)
PaCO2 (mm Hg)
Healthy Subjects
(n ⫽ 10)
Patients with COPD
(n ⫽ 9)
1.9 ⫾ 0.1
70.4 ⫾ 14.8
1.9 ⫾ 0.1
72.2 ⫾ 11.1
...
...
...
294.7 ⫾ 78.9
71.4 ⫾ 6.8
39.8 ⫾ 4.5
Note.—Values are expressed as mean ⫾ SD. Body surface area and heart rate did not differ between
groups (P ⬎ .05).
* This value is presented as a percentage of the predicted value for a healthy subject of the same
age, height, and sex and expresses bronchial obstruction.
difference between the changing intrathoracic pressure and the constant extrathoracic pressure also has an effect on
the left side of the heart by means of alteration of the afterload (3). As a result of
ventricular interdependency, the changing
right ventricular load influences filling of
the left ventricle and vice versa (6).
In previous studies with echocardiography, scintigraphy, and catheters, researchers (7–9) evaluated the influence of
either inspiration or expiration on cardiac function. Researchers in few studies
were concerned with the immediate effect of complete respiratory cycles on left
ventricular stroke volume (SV), but investigators in none of these studies focused
on patients with obstructive pulmonary
disease (3,7). The use of echocardiography to assess instantaneous changes in
aortic flow is particularly limited in patients with emphysema because of limited acoustic windows (10).
Recently, magnetic resonance (MR) flow
imaging measurements became possible in
real time, and this imaging allows assessment of the interaction between cardiac
hemodynamics and breathing (11).
Accordingly, the purpose of the present
study was to assess real-time changes of left
ventricular SV in relation to the breathing
pattern in healthy subjects and in patients
with COPD.
MATERIALS AND METHODS
Subjects and Study Design
Ten randomly selected healthy volunteers who were nonsmokers (four women,
six men; age range, 21–30 years) and nine
consecutive men (age range, 65–73 years)
who met our criteria for severe COPD (emphysema and/or chronic bronchitis; mean
forced expiratory volume in 1 second, 39.2
percentage predicted ⫾ 10.5 [SD]; reversibility, ⬍12%) were included in the present
514
䡠
Radiology
䡠
November 2003
study (Table 1). Two patients were current
smokers (⬎15 cigarettes per day, ⬎25 packyears) and seven were former heavy smokers (⬎15 cigarettes per day, ⬎15 packyears) who stopped smoking more then 9
years prior to entering this study (each
patient smoked ⬎25 pack-years). The volunteers and the patients underwent a
physical examination that included auscultation, and their clinical history was
explored to exclude any concomitant disease. All subjects gave informed consent
to participate in the protocol that was
approved by the medical ethics committee of our institution.
Real-Time MR Imaging of Flow
Subjects were examined by using an
MR unit (ACS/NT 15; Philips Medical Systems, Best, the Netherlands) with gradients of 25 mT/m and 100 mT/m/msec
(Powertrak 6000; Philips Medical Systems).
A real-time nonelectrocardiographically triggered gradient-echo echo-planar
imaging phase-contrast technique was
used, with application of two precordial
elements of a five-element cardiac synergy coil. Imaging parameters included
the following: 8.1/4.1 (repetition time
msec/echo time msec), 10-mm section
thickness, 80 ⫻ 44 matrix, 250 ⫻
150-mm field of view, 3.1 ⫻ 3.4-mm inplane spatial resolution, echo-planar imaging factor of 7, 20° flip angle, and a
temporal resolution of 49 msec per heart
phase. A total of 612 images were acquired in a total examination time of approximately 30 seconds. Velocity encoding was 200 cm/sec, and the imaging
plane was placed perpendicular to the
vertical part of the ascending aorta.
Study Protocol
Real-time MR imaging of flow was performed during normal breathing, deep
Figure 1. Diagram illustrates the sequence of
hemodynamic events during inspiration. Interaction between intrathoracic pressure (Pthor)
and right (RV) and left (LV) ventricle is shown.
For clarity, atria are not depicted. In the following explanation of the sequence, 3 ⫽ leads
to, 2 ⫽ decrease, and 1 ⫽ increase. Inspiration 3 intrathoracic pressure 23 gradient
with extrathoracic pressure 13 inferior vena
cava (VCI) flow 13 right ventricular filling
volume and pressure (P&V) 13 right ventricular SV 13 aortic pulmonary flow (A. PULM)
13 blood pooling in lungs because of increased vascular capacity 3 ventricular pulmonary flow (V. PULM) 23 left ventricular filling
volume and pressure 23 left ventricular SV
23 aortic flow 2. Note that increased right
ventricular filling also causes shifting of the
interventricular septum toward the left ventricle, compromising left ventricular filling and
contraction. Note that during expiration the
opposite occurs and left ventricular SV 1.
breathing, and the Valsalva maneuver in
healthy subjects. In patients with COPD,
real-time MR imaging flow measurements were performed during only spontaneous breathing because they were not
able to perform the maneuvers in a controlled way. Within the control group,
the breathing maneuvers were compared
with spontaneous breathing to investigate the influence of different breathing
maneuvers on SV. To determine the influence of expiratory obstruction on SV,
spontaneous breathing in patients with
COPD was compared with spontaneous
breathing in healthy control subjects.
The breathing pattern was registered by
using the standard abdominal pressure
belt of the imaging unit. The electrocardiographic signal and the breathing
curve were tapped from the imaging unit
and were recorded simultaneously by using a data acquisition software program
(Conduct-PC; CDLeycom, Zoetermeer,
van den Hout et al
Radiology
Figure 2. Images in a healthy 25-year-old man. A, Modulus and phase images of real-time MR flow imaging in the ascending aorta are
displayed and resulted in the corresponding flow peak, as illustrated. B, Simultaneous real-time recording of flow in the ascending aorta.
C, Breathing curve (gray line) and SV curve (black line with data points). Calculated SVs for all flow peaks result in the SV curve. SV
acceleration (SVacc) and SV deceleration (SVdec) are indicated with dotted black lines. These lines demonstrate the mean slope of the
ascending and descending curve. a.u. ⫽ arbitrary units. D, Electrocardiographic signal.
the Netherlands). The MR imaging flow
acquisitions were synchronized with the
breathing curve and the electrocardiographic signal by one author (R.J.v.d.H.).
The patients with COPD underwent rouVolume 229
䡠
Number 2
tine pulmonary function tests (flow-volume testing before and after salbutamol
administration) and arterial blood gas
analysis within 2 weeks before the MR
imaging examination.
Data Analysis
MR imaging flow measurements were
analyzed by using a software package
(Flow; Medis, Leiden, the Netherlands).
Real-Time MR Imaging of Aortic Flow
䡠
515
Radiology
The area under every flow peak in the
flow-time curve was then determined by
an author (R.J.v.d.H.) and represents SV
of the left ventricle. A data analysis software program (CircLab; GTX Medical
Software, Zoetermeer, the Netherlands)
was used to display the simultaneously
recorded MR imaging flow acquisition,
breathing curve, and electrocardiographic signal. The calculated SVs were
plotted at the time points of the corresponding aortic flow peak to demonstrate the correlation between SVs and
the phase of inspiration and expiration.
For five healthy control subjects, SV was
plotted versus breathing phase, and the
correlation coefficient was calculated.
The created sequence of changing SVs
during a breathing maneuver was then
analyzed (R.J.v.d.H.). The average minimal SV and the average maximal SV during inspiration and expiration were calculated. In addition, the difference
between the averaged minimal and maximal SVs was calculated and yielded the
SV range, and the mean value of all SVs
was determined. The mean slope of the
SV curve between a minimum and the
consecutive maximum was calculated
and was called SV acceleration. The mean
slope of a decrease in SV was called SV
deceleration. The SV ratio was obtained
by dividing the SV acceleration by the SV
deceleration that followed it.
Statistical Analysis
Paired two-tailed Student t tests were
used to assess significant SV differences
between normal breathing and deep
breathing or the Valsalva maneuver in
the group of healthy volunteers. The results of measurements in the patients
with COPD were compared with measurements during normal breathing in
control subjects by using an unpaired
two-tailed Student t test. A difference
with P ⬍ .05 was considered statistically
significant. All parameters were expressed as the mean ⫾ SD.
RESULTS
Figure 2 demonstrates how SV was calculated from the area under the flow curve
of the ascending aorta.
Figure 3 shows a typical example of
each breathing maneuver for a healthy
subject. Ventilatory movements were
registered with a respiratory belt and
were expressed in arbitrary units. The upslope represents inspiration, and the
downslope represents expiration. Note
the greater changes of SV during deep
516
䡠
Radiology
䡠
November 2003
Figure 3. Graphs of typical breathing maneuvers performed by the same subject as in Figure 2.
Gray line represents the breathing curve. Black line is the SV curve, with each data point
representing an SV value. Dotted horizontal line represents mean SV. This value does not differ
between normal and deep breathing. a.u. ⫽ arbitrary units. A, Normal breathing. Note that SV
increases with expiration and decreases with inspiration. B, Deep breathing. Note the exaggerated
effect of an SV increase with expiration and an SV decrease with inspiration. C, Valsalva
maneuver. Note a sudden increase in SV followed by a slow decrease in SV.
Figure 4. Graph shows correlation between thoracic excursion (inspiration or expiration) and SV during normal breathing in the same
subject as in Figure 2. Each data point represents an SV value. Note
that SV decreases from end-expiration toward end-inspiration (r2 ⫽
0.77, P ⬍ .05). For the whole group, mean r2 ⫽ 0.78 ⫾ 0.09. a.u. ⫽
arbitrary units.
breathing (Fig 3, B) and the sudden increase followed by a slow decrease of SV
during the Valsalva maneuver (Fig 3, C).
The correlation between thoracic excursion and SV was assessed for normal
breathing. Figure 4 shows a typical exam-
ple of the correlation, which was high for
all participating healthy subjects (mean
r2 ⫽ 0.78 ⫾ 0.09). Inspiration causes an
instantaneous decrease of left ventricular
SV followed by an increase during the
expiration that followed it.
van den Hout et al
parison of the gray areas in Figure 5.
Figure 6 summarizes all differences between healthy subjects and patients with
COPD.
TABLE 2
Changes in SV as a Function of Breathing Pattern in Healthy Subjects
and Patients with COPD
Radiology
Healthy Subjects
SV Parameter
Normal
Breathing
Deep
Breathing
Valsalva
Maneuver
Patients
with COPD*
Minimal (mL)
Maximal (mL)
Range (mL)
Mean (mL)
Acceleration-deceleration ratio§
78.8 ⫾ 18.2
91.9 ⫾ 18.6
13.1 ⫾ 2.7
86.0 ⫾ 18.2
1.0 ⫾ 0.5
69.1 ⫾ 15.7†
104.4 ⫾ 17.5†
35.3 ⫾ 8.3†
87.4 ⫾ 15.5
1.1 ⫾ 0.3
44.1 ⫾ 20.5†
111.5 ⫾ 25.3†
67.4 ⫾ 20.5†
78.4 ⫾ 20.3†
4.1 ⫾ 1.5†
50.1 ⫾ 4.7‡
69.6 ⫾ 6.1‡
19.5 ⫾ 5.6‡
61.1 ⫾ 5.8‡
1.8 ⫾ 0.6‡
* Patients performed spontaneous breathing.
† P ⬍ .05, paired two-tailed Student t test, compared with normal breathing.
‡ P ⬍ .05, unpaired two-tailed Student t test, compared with normal breathing of healthy
subjects.
§ Acceleration signifies the mean slope of the increase in SV from a minimum to the consecutive
maximum in the SV-versus-time graph (see Fig 2); deceleration signifies the mean slope of the
decrease in SV from a maximum to the consecutive minimum in the SV-versus-time graph.
DISCUSSION
Findings
Results of this study show that realtime MR imaging of aortic flow reveals
instantaneous changes in aortic flow related to breathing. These changes were
studied during normal and deep breathing, as well as during the Valsalva maneuver, in healthy subjects. The findings
observed during spontaneous breathing
in healthy subjects were compared with
those observed in patients with COPD.
Patients with COPD may have a breathing pattern that deviates from that of
normal sinusoidal breathing. This altered
breathing pattern affects cardiac function. In this real-time MR imaging study,
significant alterations in aortic flow that
resulted from expiratory obstruction
were demonstrated in patients with
COPD when they were compared with
healthy subjects. This real-time MR imaging technique may become useful for assessment of the hemodynamic reaction
to various treatment strategies (12).
Real-Time Flow Imaging
Figure 5. Graph shows SV curves of the same subject as in Figure 2
and of a 69-year-old man with COPD obtained during spontaneous
breathing. Curve obtained in patient with COPD is in all aspects at a
lower level, the range between minimal and maximal SV is wider
(compare gray areas), and the acceleration-deceleration ratio of SV is
higher as compared with values in the healthy subject. For all healthy
subjects, mean SV range is 13.1 mL ⫾ 2.7, and for the patients with
COPD, the range is 19.5 mL ⫾ 5.6 (P ⬍ .05). The accelerationdeceleration ratio is 1.0 ⫾ 0.5 in healthy subjects and 1.8 ⫾ 0.6 in
patients with COPD. SVacc ⫽ SV acceleration, SVdec ⫽ SV deceleration.
During the three breathing maneuvers,
different values for the SV parameters
were observed (Table 2). During deep
breathing and the Valsalva maneuver,
minimal and maximal values differed significantly from those observed during
normal breathing (P ⬍ .05). SV range became significantly wider for both deep
breathing and the Valsalva maneuver,
compared with the values observed during normal breathing (P ⬍ .05). During
the Valsalva maneuver, mean SV was significantly decreased (P ⬍ .05); the acceleration-deceleration ratio was clearly increased as a result of the sudden increase
and slow decrease of SV (P ⬍ .05). Deep
Volume 229
䡠
Number 2
breathing does not differ from normal
breathing in regard to mean SV and the
acceleration-deceleration ratio (P ⬎ .05).
When we compared values observed
during normal breathing in healthy subjects with those observed during spontaneous breathing in patients with severe
COPD, all SV parameters differed significantly between both groups (P ⬍ .05), as
demonstrated in Table 2. Cardiac performance in patients with COPD was significantly decreased in regard to minimal,
maximal, and mean SV (P ⬍ .05), as is
displayed in Figure 5. Acceleration-deceleration ratio and SV range were increased, as may be observed with com-
Conventional MR imaging flow acquisition measures only the average of all
SVs during many respiratory cycles. This
technique cannot reveal the instant SV
changes that occur as a result of the continuously changing intrathoracic pressures caused by breathing. With real-time
MR imaging flow acquisition, it is possible to assess the direct influence of
breathing on aortic flow. During inspiration, there is an instantaneous decrease
of left ventricular SV, followed by an increase during the consecutive expiration.
These measured SV changes confirm results of previous echocardiographic studies and computer model studies about
ventricular interdependence (6,7). These
results indicated that in end-inspiration
the negative intrathoracic pressure results in a lower SV than in end-expiration, when intrathoracic pressure equals
atmospheric pressure.
Relationship between Cardiac Flow
and Different Breathing Maneuvers
With real-time MR imaging, it was possible to demonstrate that breathing maneuvers have a distinct influence on cardiac SV. The present results indicate that
Real-Time MR Imaging of Aortic Flow
䡠
517
Radiology
minimal and maximal SV show a significant change when deep breathing or the
Valsalva maneuver are performed as
compared with the values measured during normal breathing. It is hypothesized
that more extreme intrathoracic pressures during special maneuvers cause the
changes in these SV parameters (7).
In healthy subjects, the ratio of SV acceleration divided by SV deceleration
equals 1 during normal and deep breathing. When there is expiratory airway obstruction, such as during the Valsalva
maneuver or during spontaneous breathing in patients with COPD, this ratio increases because of the prolongation of
the period in which SV decreases. The
Valsalva maneuver implies an extremely
obstructed expiratory phase and might
therefore be a model for spontaneous
breathing in COPD (13). SV increases rapidly at the beginning of the Valsalva maneuver and decreases slowly while there
is still a higher (expiratory) intrathoracic
pressure. This is in agreement with the
findings in the study of Eichenberger et al
(11), who used real-time MR imaging to
assess the aortic blood flow during a few
seconds of normal breathing and during
the Valsalva maneuver in healthy subjects. They found a SV decrease of 25% at
the end of the maneuver, as compared
with the average SV during normal
breathing. The present results show an
SV decrease of almost 50%.
Figure 6. Graph shows comparison of all SV parameters as a result of normal breathing in both
healthy subjects and patients with COPD. COPD causes a decrease of minimal, maximal, and
mean SV (P ⬍ .05). Note the increase in SV range and acceleration-deceleration ratio in patients
with COPD as compared with values in healthy subjects (P ⬍ .05). ⴱ ⫽ P ⬍ .05, unpaired
two-tailed Student t test, comparison between healthy subjects and patients with COPD.
jects. This suggests that after the normal
increase at the start of expiration, SV
slowly starts to decrease during the last
phase of expiration, and the decrease in SV
continues during inspiration. All these differences in SV parameters in patients with
COPD are comparable with the differences
that occur during the Valsalva maneuver
when compared with nonobstructed
breathing, and these findings support the
hypothesis that the Valsalva maneuver can
be used as a model for breathing in patients
with COPD (13).
Patients with COPD
Clinical Implications
The results show that the patients with
COPD have a decreased minimal, maximal, and mean left ventricular SV as compared with subjects who have normal unobstructed breathing. Heart rate did not
differ between both groups. The diminished SV in patients with COPD indicates
impaired cardiac function caused by the
pathologically altered pressure relationships between the intra- and extrathoracic
compartments as a result of the obstructed
breathing pattern (5). Hypoxemia induced
by both parenchymal and vascular pulmonary damage can also add to the impaired
cardiac function (4). The SV range, that is,
the difference between minimal and maximal SV, is wider when compared with that
during normal breathing in healthy subjects. This is probably because of the increased gap between the higher end-expiratory intrathoracic pressure and the
normal unobstructed inspiratory thoracic
pressure. The acceleration-deceleration ratio of the SV curve is significantly higher in
patients with COPD who are breathing
spontaneously than it is in healthy sub-
We believe that in the future this technique can be useful in the monitoring of
cardiac SV noninvasively to evaluate
the effect of pulmonary medication (ie,
bronchodilators) and oxygen therapy. It
might also be useful in the evaluation of
the hemodynamic effect of breathing retraining that is part of a pulmonary rehabilitation program (14,15).
Moderate pulmonary hypertension is
frequently encountered in patients with
severe COPD and results in elevated right
ventricular pressures. This, in turn, may
contribute to the paradoxical movement
of the intraventricular septum, with an
adverse effect on left ventricular SV, cardiac output, and cardiac index. The effect
of medical therapy aimed at the reduction of pulmonary hypertension and
right ventricular pressures may be evaluated by the proposed MR imaging protocol as well. The MR imaging protocol in
this study may be useful to provide
highly accurate and reproducible measurements noninvasively to monitor cardiopulmonary hemodynamics.
518
䡠
Radiology
䡠
November 2003
Limitations
Intrathoracic pressures were measured
indirectly with a respiratory belt balloon.
Body surface area and heart rate were
equal between both groups (ie, healthy
subjects and patients with COPD), although mean age was different. However, findings of some studies (16,17) indicate that SV remains constant over
time or even increases with age in
healthy individuals.
In conclusion, in contrast to conventional velocity-encoded MR imaging,
real-time MR flow imaging can demonstrate a decrease in left ventricular SV
during inspiration and an increase in SV
during expiration.
In addition, instantaneous effects of
changes in breathing on SV can be measured by using real-time MR flow imaging. In healthy volunteers, deep breathing caused an increase in the range of SV,
whereas the mean SV and the slopes of
the SV curve remained unchanged, as
compared with these parameters during
normal breathing. The Valsalva maneuver exaggerated the observed difference
in SV range caused by deep breathing in
normal subjects. The SV curve of the Valsalva maneuver became strongly asymmetrical because of a prolongation of the
SV decrease, as compared with those observed during normal and deep breathing.
In patients with COPD—that is, in patients with an expiratory obstruction—
the observed increase in SV range was
similar to that during deep breathing and
the Valsalva maneuver, as observed in
healthy subjects. Moreover, the SV minimum, SV maximum, and mean SV were
at a lower level, as compared with those
van den Hout et al
Radiology
in healthy subjects. An interesting observation was that the SV curve in COPD
patients became asymmetrical with a fast
SV increase and a slow decrease that reflected expiratory obstruction, as observed during the Valsalva maneuver in
healthy subjects. MR imaging evaluation
of hemodynamics may become useful for
monitoring of the effect of therapy in
patients with COPD or pulmonary hypertension. The technique also will be useful
to study the pathophysiology of COPD
and other diseases with heart-lung interaction.
Acknowledgments:
We acknowledge the
important contributions of Erik van den Berg,
BS, and Zafiria Metafratzi, MD, in the analysis
of the data and in the assistance they provided
during the imaging procedures. Rik van den
Hout passed away after a long illness on April
23, 2003. His coauthors dedicate this article to
his memory.
References
1. Vizza CD, Lynch JP, Ochoa LL, Richardson G, Trulock EP. Right and left ventricular dysfunction in patients with severe
pulmonary disease. Chest 1998; 113:576 –
583.
2. Tyberg JV, Grant DA, Kingma I, et al. Effects of positive intrathoracic pressure on
Volume 229
䡠
Number 2
3.
4.
5.
6.
7.
8.
9.
10.
pulmonary and systemic hemodynamics.
Respir Physiol 2000; 119:171–179.
Buda AJ, Pinsky MR, Ingels NB Jr, et al.
Effect of intrathoracic pressure on left
ventricular performance. N Engl J Med
1979; 301:453– 459.
Matthay RA, Niederman MS, Wiedemann
HP. Cardiovascular-pulmonary interaction in chronic obstructive pulmonary
disease with special reference to the
pathogenesis and management of cor
pulmonale. Med Clin North Am 1990;
74:571– 618.
Scharf SM. Cardiovascular effects of airways obstruction. Lung 1991; 169:1–23.
Amoore JN, Santamore WP. Model studies of the contribution of ventricular interdependence to the transient changes
in ventricular function with respiratory
efforts. Cardiovasc Res 1989; 23:683– 694.
Guz A, Innes JA, Murphy K. Respiratory
modulation of left ventricular stroke volume in man measured using pulsed
Doppler ultrasound. J Physiol Lond 1987;
393:499 –512.
Karam M, Wise RA, Natarajan TK, Permutt S, Wagner HN. Mechanism of decreased left ventricular stroke volume
during inspiration in man. Circulation
1984; 69:866 – 873.
Michard F, Chemla D, Richard C, et al.
Clinical use of respiratory changes in arterial pulse pressure to monitor the hemodynamic effects of PEEP. Am J Respir
Crit Care Med 1999; 159:935–939.
Boussuges A, Pinet C, Molenat F, et al.
Left atrial and ventricular filling in
11.
12.
13.
14.
15.
16.
17.
chronic obstructive pulmonary disease:
an echocardiographic and Doppler study.
Am J Respir Crit Care Med 2000; 162:
670 – 675.
Eichenberger AC, Schwitter J, McKinnon
GC, Debatin JF, von Schulthess GK.
Phase-contrast echo-planar MR imaging:
real-time quantification of flow and velocity patterns in the thoracic vessels induced by Valsalva’s maneuver. J Magn
Reson Imaging 1995; 5:648 – 655.
Lualdi JC, Goldhaber SZ. Right ventricular dysfunction after acute pulmonary
embolism: pathophysiologic factors, detection, and therapeutic implications.
Am Heart J 1995; 130:1276 –1282.
Markelov IM, Karashurov ES, Martianov
SG. Role of intrathoracic pressure in
changes in the greater and lesser circulation hemodynamics in patients with
bronchial asthma. Sov Med 1990; 10 –14.
Aliverti A, Macklem PT. How and why
exercise is impaired in COPD. Respiration
2001; 68:229 –239.
Guell R, Casan P, Belda J, et al. Long-term
effects of outpatient rehabilitation of
COPD: a randomized trial. Chest 2000;
117:976 –983.
Slotwiner DJ, Devereux RB, Schwartz JE,
et al. Relation of age to left ventricular
function in clinically normal adults. Am J
Cardiol 1998; 82:621– 626.
Wandt B, Bojo L, Hatle L, Wranne B. Left
ventricular contraction pattern changes
with age in normal adults. J Am Soc Echocardiogr 1998; 11:857– 863.
Real-Time MR Imaging of Aortic Flow
䡠
519