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

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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 J Ultrasound Med 2007; 26:885–891
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 J Ultrasound Med 2007; 26:885–891 887
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