The Importance of Monophasic Doppler Waveforms in the Common ...

Article
The Importance of Monophasic
Doppler Waveforms in the Common
Femoral Vein
A Retrospective Study
Edward P. Lin, MD, Shwetta Bhatt, MD, Deborah Rubens, MD,
Vikram S. Dogra, MD
Objective. The purpose of this study was to assess the importance of monophasic waveforms encountered
in the common femoral vein during deep venous thrombosis evaluation by a retrospective review
of lower extremity venous Doppler (VD) sonography and correlative studies, such as computed tomography
(CT) and magnetic resonance imaging. Methods. A retrospective review was conducted of
lower extremity VD studies performed from September 1, 2000, through September 1, 2005. All satisfactory
VD studies, which were in compliance with the Intersocietal Commission for the Accreditation
of Vascular Laboratories standard protocol, were evaluated for the presence of monophasic waveforms
and correlated with CT of the abdomen and pelvis. Studies were evaluated for the causes of monophasic
waveforms. Patients younger than 18 years were excluded. Results. A total of 2963 VD examinations
were reviewed. One hundred twenty-four of 2963 showed monophasic waveforms. Eighty-nine
of the 124 had additional CT examinations within 1 week; 19 had CT within 2 months; and 16 had
no additional examinations. Forty-seven of 124 cases revealed deep venous thrombosis extending into
the iliac veins, of which 23 were identified by VD sonography; 26 were due to extrinsic compression;
6 showed a hypoplastic or stenosed common iliac vein; and the remaining 45 had no apparent causes
for the monophasic waveforms. Conclusions. Monophasic waveforms in the common femoral
veins are reliable indicators of proximal venous obstruction. Because iliac vein thrombosis is clinically
important, we recommend routine sonographic evaluation of external iliac veins in the presence of
monophasic waveforms and CT or magnetic resonance imaging, if necessary, to determine the cause
of the monophasic waveforms. Key words: color flow Doppler sonography; deep venous thrombosis;
monophasic waveforms; sonography.
Abbreviations
CT, computed tomography; DVT, deep venous thrombosis;
IVC, inferior vena cava; MRI, magnetic resonance
imaging; PE, pulmonary embolism; VD, venous Doppler
Received February 20, 2007, from the Department
of Imaging Sciences, University of Rochester School
of Medicine, Rochester, New York USA. Revision
requested March 12, 2007. Revised manuscript
accepted for publication March 21, 2007.
Address correspondence to Vikram S. Dogra,
MD, Department of Imaging Sciences, University of
Rochester School of Medicine, 601 Elmwood Ave,
Box 648, Rochester, NY 14642 USA.
E-mail: vikram_dogra@urmc.rochester.edu
The normal common femoral venous waveform
shows phasicity on spectral Doppler analysis.
Phasic variation results from increasing and
decreasing intrathoracic pressures secondary to
respiration and is sometimes referred to as respirophasic.
This rise and fall in pressure are transmitted from the
central to peripheral veins and manifest as a cyclic
change in blood flow velocity, which can be detected by
spectral Doppler sonography. Loss of this phasic variation
results in a monophasic waveform. Monophasic
waveforms in the common femoral vein occur when the
transmission of respiratory pressure to the vein is dampened
or disrupted by extrinsic compression, proximal
deep venous thrombosis (DVT), or intrinsic luminal narrowing
of a more proximal vein.
© 2007 by the American Institute of Ultrasound in Medicine • J Ultrasound Med 2007; 26:885–891 • 0278-4297/07/$3.50

Monophasic Doppler Waveform in the Common Femoral Vein
Scattered reports have observed the usefulness
of dampened venous waveforms as indicators of
more central venous obstruction or extrinsic
compression. One small study of patients
with cancer reported an association between
monophasic waveforms and proximal venous
extrinsic compression or DVT. 1 To our knowledge,
however, no prior study has formally evaluated
the importance of monophasic waveforms
in the general population.
The purpose of our study was to assess the
importance of monophasic waveforms as encountered
in the common femoral vein during
lower extremity sonographic evaluation for DVT.
We reviewed venous Doppler (VD) studies of the
lower extremities and their correlative studies,
such as computed tomography (CT) and magnetic
resonance imaging (MRI), to determine the
most common causes of monophasic waveforms.
Materials and Methods
In a retrospective review of lower extremity VD
examinations from September 1, 2000, through
September 1, 2005, all VD studies, in compliance
with the Intersocietal Commission for the
Accreditation of Vascular Laboratories standard
protocol, were evaluated for the presence of
monophasic waveforms.
Examinations were performed with a 5- to 7-
MHz linear array transducer (Sequoia, Siemens
Medical Solutions, Mountain View, CA; or HDI
5000, Philips Medical Systems, Bothell, WA).
Patients were examined in the supine position,
and compression sonography was performed in
the transverse plane from the common femoral
to the popliteal veins. The calf veins were evaluated
if the patient had calf pain or swelling.
Spectral Doppler sonography was performed in
the longitudinal plane with a Doppler angle of
60° or less. Spectral Doppler tracings were
obtained in the common femoral, femoral, and
popliteal veins. In addition, the presence of
spontaneous flow, phasic variation, response to
the Valsalva maneuver, and augmentation were
recorded in all examinations.
Correlative studies, such as CT and MRI of the
abdomen and pelvis, were further investigated as
reference standards after the sonographic studies
were reviewed to evaluate the causes of the
monophasic waveforms as observed on VD studies.
The CT and MRI studies were read by a different
reader, who was blinded to the sonographic
results. Computed tomographic scans used a
4-, 16-, or 40-slice scanner, and MRI was performed
on a 1.5-T magnet. Patients younger than
18 years were excluded from the study.
Results
A total of 2963 adult color flow Doppler examinations
were reviewed. Monophasic waveforms
were shown in 124 of the 2963 studies. The ages
of patients ranged from 18 to 93 years with an
average age of 51 years. Sixty-five patients were
female, and 59 were male.
The most common causes of the monophasic
waveforms observed in this study are summarized
in Table 1. Of the 124 patients with
monophasic waveforms, 41 had an underlying
malignancy; 22 were postsurgical; 8 had an
underlying coagulopathy; 6 had systemic infections;
5 were pregnant; 5 had a debilitating
stroke or were paraplegic; and 4 had a history of
recent trauma. The remaining 33 patients had
other medical conditions that were not prone to
thrombosis or were otherwise healthy.
Eighty-nine of the 124 patients had correlative
examinations, such as CT and MRI, within 1
week, and 19 of the 124 had such examinations
within 2 months. Sixteen of the 124 patients had
no correlative examinations within a 2-month
period. Two patients with CT also underwent
venography during inferior vena cava (IVC) filter
placement.
Forty-seven (38%) of the 124 cases revealed
DVT extending into the iliac veins, of which 23
were identified by VD sonography (49%). The
remaining 24 iliac vein DVT cases (51%) were
diagnosed by CT or MRI. In 26 (21%) of the 124
patients, monophasic waveforms were due to
extrinsic compression, such as pregnancy, lym-
Table 1. Most Common Causes of Monophasic
Waveforms in 2963 Patients
Cases with monophasic waveform, n 124
DVT involving iliac veins, n (%) 47 (38)
Extrinsic compression, n (%) 26 (21)
Intrinsic narrowing, n (%) 6 (5)
No explanation, n (%) 45 (36)
886
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Lin et al
phocele, or hematoma. Six (5%) of the 124 cases
had a hypoplastic or stenosed common iliac
vein. The remaining 45 patients (36%) had no
apparent causes for the monophasic waveforms.
Of the 47 DVTs involving the iliac veins, 15
(32%) were isolated to the iliac veins, 1 of which
extended into the IVC. Seventeen (36%) of the 47
extended from the common femoral vein into
the iliac vein, and 15 (32%) extended from the
popliteal vein into the iliac vein.
Discussion
Monophasic waveforms result when the transmission
of fluctuating intrathoracic pressures to
distal venous structures is dampened. The loss of
phasic variation may be due to (1) a nonocclusive
thrombus in a more proximal vein; (2) extrinsic
compression from a structure external to the
vein, such as fluid collections, lymphadenopathy,
or intrauterine pregnancy; (3) intrinsic luminal
narrowing secondary to a hypoplastic vein or
sequelae from radiation or a prior thrombus; and
(4) other causes, such as ascites and cardiac and
technical factors (Figures 1–5).
Venous thrombosis involving the iliac veins was
the most common cause (38%) of monophasic
waveforms in our study, followed by extrinsic
compression (21%) and intrinsic narrowing (5%).
A considerable number of studies (36%) had no
discernable explanation for the loss of phasic
variation.
Most DVTs arise from the deep calf veins, often
along the valve cusps, and extend proximally. 2,3
Approximately half of calf vein DVTs will resolve,
and one sixth will continue to advance proximally. 2
As a DVT ascends into the common femoral vein,
the risk of pulmonary embolism (PE) increases. 2,4–7
If left untreated, approximately 50% of patients will
have a PE within 3 months. 4,5 Borst-Krafek et al 7
reported an equal incidence of PE associated with
femoral vein, iliac vein, and IVC thrombosis.
A
Figure 1. A and B, Spectral Doppler tracings of the right common
femoral vein (CFV) in a healthy 66-year-old female patient with normal
phasic variation (A) and in a 21-year-old male patient with factor V Leiden
deficiency and a monophasic waveform in the right common femoral
vein (B). C, Subsequent noncontrast CT shows a large hematoma compressing
the right common iliac vein (arrow).
B
C
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Monophasic Doppler Waveform in the Common Femoral Vein
A
B
Figure 2. A, Spectral Doppler evaluation of a 54-year-old male patient after cardiac surgery shows a monophasic waveform in the distal left external
iliac vein (IL A/V). B, Color flow image shows absent flow within a more proximal segment of the external iliac vein, representing DVT.
The incidence of iliac vein thrombosis was initially
reported to be in the range of 1% to 4%. 8,9 However, with
the increased use of less invasive imaging modalities
such as MRI and CT venography, iliac vein thrombosis is
more common than previously thought. In a study of
769 patients, Spritzer et al 10 reported an acute DVT isolated
to the iliac vein or IVC in 20% of the patients and
involving the femoral and iliac veins in 18%.
A
Figure 3. A and B, Spectral Doppler tracings from a 60-year-old female
patient with a malignant spindle cell tumor show monophasic waveforms
in the right (A) and left (B) common femoral veins (CFV). C, Selected axial
post–intravenous contrast CT of the abdomen shows a thrombus (arrow)
within the right common iliac vein extending into the IVC.
B
C
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Lin et al
Postphlebitic syndrome is a common complication
of pelvic and lower extremity DVT. 11
Inflammation and scarring of venous valves
often lead to valve incompetence and reflux,
resulting in venous congestion, decreased muscle
perfusion, and increased tissue permeability. 12,13
Patients with postphlebitic syndrome have pain,
swelling, heaviness, cramps, and tingling in the
affected limb. 14 The incidence of postphlebitic
syndrome may be equal or possibly increased
compared with calf or thigh DVT. 12,15,16
Monophasic waveforms are reliable indicators
of proximal iliac vein or IVC thrombosis.
Approximately 40% of monophasic waveforms in
this series were secondary to iliac vein thrombosis.
Most (68%) of these iliac vein thromboses
extended from leg veins, and one third were
isolated to the iliac vein. Although the actual
incidence of iliac vein thrombosis in the study
population was not investigated, a future
prospective study may evaluate the incidence of
iliac vein thrombosis in acute DVTs and the percentage
of iliac vein thrombosis that have
monophasic waveforms.
A considerable portion (21%) of the patients with
monophasic waveforms were also found to have
lymph nodes, tumors, and hematomas, which
compressed more proximal veins. These findings
are clinically relevant to patient treatment and
stress the importance of following monophasic
waveforms when initially encountered.
Asymmetry of waveforms, with normal phasic
variation on one side and loss of phasic variation
on the other side, may help localize abnormalities
to the side of the monophasic waveform. Bilateral
monophasic waveforms suggest an IVC thrombus
or a large structure, such as an intrauterine pregnancy,
compressing both iliac veins or the IVC.
The waveforms of both common femoral veins
should be compared with each other in all lower
extremity VD sonograms.
A
Figure 4. A and B, Spectral Doppler waveforms of the left (A) and right
(B) common femoral veins (CFV) in a 71-year-old female patient with
metastatic bladder carcinoma show asymmetry of waveforms, with
monophasicity in the left common femoral vein. C, Follow-up post–intravenous
contrast CT shows large necrotic lymph nodes compressing the
left external iliac vein (arrow).
B
C
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Monophasic Doppler Waveform in the Common Femoral Vein
This study was limited by its retrospective
design and the substantial number of monophasic
waveforms that remained unexplained
(36%). Technical factors and the presence of
ascites and cardiac conditions were not
explored. For example, monophasic waveforms
in pregnancy may be position dependent; shifting
the patient to the contralateral decubitus
position has been observed, at our center, to
elicit respirophasic variation in a vein that initially
had a monophasic waveform.
External iliac veins are not imaged during routine
evaluation of lower extremity veins. In addition,
the evaluation of iliac veins has not been
addressed by the American College of Radiology
or the American Institute of Ultrasound in
Medicine. In our study, 23 (49%) of the 47 iliac
vein DVTs were initially discovered by VD sonography.
Routine sonographic evaluation of external
iliac veins should therefore be performed
when monophasic waveforms are present. If the
sonographic evaluation is inconclusive, we recommend
further evaluation with CT or MR
venography.
In conclusion, monophasic waveforms in the
common femoral veins are reliable indicators
of proximal venous obstruction, particularly
iliac vein thrombosis. Iliac vein thrombosis is
clinically important because it has an equal
incidence of PE and postphlebitic syndrome
A
Figure 5. Images from a 37-year-old female patient with a history of a
DVT in the left common iliac vein during a remote pregnancy. A and B,
Spectral Doppler waveforms of the common femoral veins show asymmetry
of waveforms, with a monophasic waveform in the left common
femoral vein (FVS; A) and normal phasic variation in the right common
femoral vein (CFV; B). C, Follow-up post–intravenous contrast CT shows
a stenotic segment (arrow) of the left common iliac vein secondary to a
sequela of the prior DVT. LA indicates left common iliac artery; RA, right
common iliac artery; and RV, right common iliac vein.
B
C
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Lin et al
compared with thigh DVT. It should also be recognized
that the incidence of iliac vein thrombosis
is likely higher than previously thought. In
light of these findings, we recommend routine
evaluation of external iliac veins in the presence
of monophasic waveforms and additional
imaging, if necessary, to determine the cause of
monophasic waveforms.
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