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The Importance of MonophasicDoppler Waveforms in the CommonFemoral 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 encoun-

tered 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 tomog-raphy (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 sat-

isfactory 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 monopha-

sic waveforms. Patients younger than 18 years were excluded. Results. A total of 2963 VD examina-

tions 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 caus-

es for the monophasic waveforms. Conclusions. Monophasic waveforms in the common femoralveins 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.

Received February 20, 2007, from the Department of Imaging Sciences, University of Rochester School of Medicine, Rochester, New York USA. Revisionrequested 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: [email protected]

AbbreviationsCT, computed tomography; DVT, deep venous throm-bosis; IVC, inferior vena cava; MRI, magnetic resonanceimaging; PE, pulmonary embolism; VD, venous Doppler

he 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 varia-

tion results in a monophasic waveform. Monophasic

waveforms in the common femoral vein occur when the

transmission of respiratory pressure to the vein is damp-

ened or disrupted by extrinsic compression, proximal

deep venous thrombosis (DVT), or intrinsic luminal nar-

rowing 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

T

Article

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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 betweenmonophasic waveforms and proximal venous

extrinsic compression or DVT.1 To our knowl-

edge, however, no prior study has formally evalu-

ated the importance of monophasic waveforms

in the general population.

The purpose of our study was to assess the

importance of monophasic waveforms as en-

countered 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 magnet-ic 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 evalu-

ated 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 stud-

ies were reviewed to evaluate the causes of the

monophasic waveforms as observed on VD stud-

ies. The CT and MRI studies were read by a differ-

ent reader, who was blinded to the sonographic

results. Computed tomographic scans used a

4-, 16-, or 40-slice scanner, and MRI was per-formed 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 examina-

tions 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 summa-

rized 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 infec-

tions; 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 124patients, monophasic waveforms were due to

extrinsic compression, such as pregnancy, lym-

886

Monophasic Doppler Waveform in the Common Femoral Vein

Table 1. Most Common Causes of MonophasicWaveforms in 2963 Patients

Cases with monophasic waveform, n 124DVT involving iliac veins, n (%) 47 (38)Extrinsic compression, n (%) 26 (21)Intrinsic narrowing, n (%) 6 (5)No explanation, n (%) 45 (36)

J Ultrasound Med 2007; 26:885–891

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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 trans-

mission of fluctuating intrathoracic pressures to

distal venous structures is dampened. The loss of

phasic variation may be due to (1) a nonocclusivethrombus 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 nodiscernable 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 al7

reported an equal incidence of PE associated with

femoral vein, iliac vein, and IVC thrombosis.

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Lin et al

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 com-

pressing the right common iliac vein (arrow).

BC

A

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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 al10 reported an acute DVT iso-

lated to the iliac vein or IVC in 20% of the patients and

involving the femoral and iliac veins in 18%.

888 J Ultrasound Med 2007; 26:885–891


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

A

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.

A B

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Postphlebitic syndrome is a common compli-

cation 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 muscleperfusion, 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 thrombo-

sis. Most (68%) of these iliac vein thromboses

extended from leg veins, and one third wereisolated 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 per-

centage of iliac vein thrombosis that have


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 andstress 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 preg-

nancy, 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.

J Ultrasound Med 2007; 26:885–891 889

Lin et al

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–intra-

venous contrast CT shows large necrotic lymph nodes compressing the

left external iliac vein (arrow).

B

C

A

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This study was limited by its retrospective

design and the substantial number of monopha-

sic waveforms that remained unexplained

(36%). Technical factors and the presence of

ascites and cardiac conditions were notexplored. For example, monophasic waveforms

in pregnancy may be position dependent; shift-

ing the patient to the contralateral decubitus

position has been observed, at our center, to

elicit respirophasic variation in a vein that ini-

tially had a monophasic waveform.

External iliac veins are not imaged during rou-

tine evaluation of lower extremity veins. In addi-

tion, 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 sonog-

raphy. Routine sonographic evaluation of exter-

nal iliac veins should therefore be performed when monophasic waveforms are present. If the

sonographic evaluation is inconclusive, we rec-

ommend 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

890 J Ultrasound Med 2007; 26:885–891


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 asym-metry 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.

BC

A

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compared with thigh DVT. It should also be rec-

ognized that the incidence of iliac vein thrombo-

sis is likely higher than previously thought. In

light of these findings, we recommend routine

evaluation of external iliac veins in the presenceof monophasic waveforms and additional

imaging, if necessary, to determine the cause of


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