Mira L. Katz

Why does prophylaxis with external pneumatic compression for deep vein thrombosis fail

External pneumatic compression (EPC) devices are increasing in popularity for deep vein thrombosis (DVT) prophylaxis. Patients who have these devices applied postoperatively are assumed to have effective prophylaxis, although a number of extensive postoperative DVT complications have been observed. This study evaluates the proper application of EPC devices in patients in intensive care units and regular nursing floor units and assesses whether dedicated in-service instruction can improve proper use. In a prospective study of 138 patients with 2 or more risk factors for postoperative DVT, it was found that patients on routine nursing units had properly functioning EPC devices during 48% (306 of 636) of the visits compared with 78% (312 of 398) of the visits in the intensive care unit (ICU) (p less than 0.0001). Follow-up of patients transferred from an ICU to a regular nursing unit showed that functional application decreased from 82% (129 of 157) to 33% (40 of 122) (p less than 0.005). The compression sleeves were not applied in 84% of the nonfunctional devices and were properly in place but the pump nonfunctional in 16%. Unfortunately, dedicated in-service instruction did not improve the proper use of EPC. Although proper application of EPC is better in the ICU compared with regular nursing units, improper use is frequent and failure of DVT prophylaxis with EPC devices may be due to improper use, rather than failure of the method itself.

Popliteal venous aneurysm: Report of two cases and review of the world literature

Two new cases of popliteal venous aneurysm are reported and added to the 22 other cases of popliteal venous aneurysm available for review. Both patients were first seen with acute pulmonary embolism and were treated with thrombolytic therapy followed by anticoagulation. Each had recurrent venous thromboembolism before discovery of the popliteal venous aneurysm. One popliteal venous aneurysm was diagnosed with phlebography and the second with venous duplex imaging, confirmed with phlebography. Both were surgically corrected with tangential aneurysmectomy and lateral venorrhaphy. Twenty-four cases of popliteal venous aneurysm are now available for review. Seventy-one percent (17 of 24) presented with pulmonary embolism, 88% (21 of 24) were saccular, and 96% (23 of 24) were located in the proximal popliteal vein. All but two were diagnosed by ascending phlebography. Three patients received no treatment: in two of these the outcome was not documented and the third had occasional pain. Two patients received anticoagulation without subsequent operative repair and both died of recurrent pulmonary emboli. Operative correction resulted in a 75% patency rate with 21% complications, most of which were related to postoperative anticoagulation. No patient who was operated on had subsequent pulmonary embolism, and there were no operative deaths. We suggest that all patients who have pulmonary embolism have lower-extremity venous duplex imaging. All popliteal venous aneurysms should be surgically repaired, inasmuch as nonoperative therapy results in recurrent thromboembolism and an unacceptably high mortality rate. Tangential aneurysmectomy with lateral venorrhaphy is the recommended procedure.

Hemodynamic deterioration in chronic venous disease

Clinical deterioration of patients with chronic venous disease (CVD) has been well described and a standardized classification has been proposed. The progressive hemodynamic deterioration producing these clinical findings is less well appreciated. This study examines and correlates venous hemodynamics with clinical severity in patients with CVD. Two hundred seventy-four extremities from 149 patients with varying degrees of CVD and 56 extremities from 28 symptom-free volunteers were evaluated clinically and hemodynamically. Each limb was assessed for functional venous volume, degree of valvular insufficiency, efficiency of the calf muscle pump, and noninvasive estimate of ambulatory venous pressure. In addition, exercise venous pressures were recorded in 56 extremities from 36 patients and 9 extremities from 6 volunteers. As CVD progresses from class 0 to class 2, venous volume expands, valvular function deteriorates, the calf muscle pump becomes inefficient, and ambulatory venous hypertension develops. However, once extremities develop brawny edema or hyperpigmentation, further deterioration of limb hemodynamics does not occur. Patients with deep venous obstruction have more severe valvular insufficiency, calf muscle pump dysfunction, and ambulatory venous hypertension than have patients without evidence of obstruction. Residual volume fraction offers a reliable noninvasive estimate of ambulatory venous pressure (r = 0.76), although its correlation was significantly better for patients without venous obstruction (r = 0.86) than for those with obstruction (r = 0.40; p < 0.05). Deterioration in venous hemodynamics parallels clinical severity through class 2. Once brawny edema and hyperpigmentation occur, ulceration develops without additional deterioration of venous hemodynamics.

Venous duplex imaging: Should it replace hemodynamic tests for deep venous thrombosis?***

Noninvasive diagnosis of deep venous thrombosis has traditionally relied on detection of alterations in venous hemodynamics. Although phleborheography is among the most sensitive tests, it is inadequate for diagnosing infrapopliteal and nonocclusive proximal thrombi and for surveillance of patients at high risk for deep venous thrombosis. Venous duplex imaging is a new technique being rapidly accepted, however, without the same critical analysis given to previous diagnostic modalities. The purpose of this study is to evaluate the diagnostic acumen of venous duplex imaging compared to phleborheography and ascending phlebography in two distinct patient groups, and to determine whether patient selection, and thus the location or magnitude of thrombi have significant influence on these diagnostic tests. One hundred ten extremities in 103 patients were prospectively evaluated with venous duplex imaging, phleborheography, and ascending phlebography within the same 24-hour period. Patients were categorized into one of two groups: Diagnostic--patients evaluated because of clinical suspicion of acute deep venous thrombosis; and Surveillance--patients at high risk of postoperative deep venous thrombosis after total joint replacement, but not symptomatic. Patients in the diagnostic group had a greater frequency of deep venous thrombosis (p less than 0.001) and significantly more occluding above-knee thrombi (p = 0.054) compared to those in the surveillance group. Phleborheography detected 73% (27/37) of above-knee thrombi in the diagnostic group compared to 29% (2/7) in the surveillance group (p = 0.036). This difference was not noted with venous duplex imaging, which detected 100% of above-knee thrombi in both diagnostic and surveillance groups and 78% (7/9) of all below-knee thrombi.(ABSTRACT TRUNCATED AT 250 WORDS)

The preoperative diagnosis of the ulcerated carotid atheroma

Arteriography and carotid duplex imaging accurately quantify the degree of stenosis caused by carotid atheroma. Since arteriography is inconsistent in identifying carotid ulceration, and controversy exists regarding the diagnostic accuracy of carotid B-mode imaging, a prospective study was performed comparing the two techniques to 126 carotid endarterectomy specimens. Sixty percent (76/126) of specimens contained ulcers. The diagnostic sensitivity for B-mode imaging and arteriography was 47% (36/76) and 53% (40/76), respectively (p = NS). Importantly, the degree of stenosis caused by the plaque significantly affected diagnostic sensitivities. B-mode sensitivity was 77% (10/13) in plaques less than or equal to 50% and 41% (26/63) for plaques greater than 50% (p = 0.03). Arteriography likewise detected 77% (10/13) of ulcers in plaques less than or equal to 50% stenosis and 48% (30/63) in plaques with greater than 50% stenosis (p = 0.07). In patients with focal symptoms, 100% (10/10) of plaques with less than or equal to 50% stenosis contained ulcers, whereas in plaques with greater than 50% stenosis 63% (36/57) contained ulcers (p = 0.02). These data indicate that the diagnostic sensitivity for carotid ulceration is not significantly different between B-mode carotid imaging and arteriography. Since most B-mode errors occur with high-grade stenoses this short-coming is unlikely to adversely affect patient care. Previous studies investigating the ability of carotid B-mode imaging to detect ulceration failed to address quantitative aspects of the carotid plaque. These data appear to resolve the previously existing controversy.

The comparative value of noninvasive testing for diagnosis and surveillance of deep vein thrombosis

This is a prospective analysis of 351 patients in two distinct groups undergoing ascending phlebography, impedance plethysmography (IPG), and/or phleborheography (PRG) within the same 24-hour period. One hundred twenty patients also had a 125I-fibrinogen uptake test (RFUT). The two patient groups consisted of the following: those patients evaluated because of suspicion of deep vein thrombosis (DVT) (diagnostic) and those patients at high risk for postoperative DVT (total joint replacement) who had routine noninvasive testing and ascending phlebography (surveillance). The overall sensitivities for IPG and PRG were significantly better in the diagnosis group (71% [69 of 97 patients] and 78% [82 of 105], respectively) compared with the surveillance group (20% [14 of 71] and 27% [17 of 63], respectively) (p less than 0.0001). The sensitivities for IPG and PRG detecting proximal (A/K) thrombi was 83% (68 of 82 patients) and 92% (79 of 86) in the diagnosis group compared with 32% (11 of 34) and 33% (9 of 27) in the surveillance group (p less than 0.0001). Although there was no difference in overall incidence of DVT between the diagnosis group (56%, 118 of 212 patients) and the surveillance group (55%, 76 of 139), the results can be explained by the difference in A/K thrombi (84% [99 of 118] and 47% [36 of 76]) (p less than 0.001) and occlusive A/K thrombi (84% [58 of 69] and 23% [7 of 31]) (p less than 0.0001), respectively. Of the patients with A/K thrombi, 97% (67 of 69) in the diagnosis group had hemodynamically detectable thrombi compared with only 48% (12 of 25) in the surveillance group (p less than 0.001). Combining the RFUT with the noninvasive studies for surveillance significantly improved the sensitivity for both A/K and distal thrombi. Patient selection also appears to have a significant influence on the results of the combination of IPG and RFUT when the current surveillance group is compared with similarly performed studies in a previously reported diagnosis group. The location and magnitude of thrombi in any patient population can be skewed depending on indications and timing of testing, thereby significantly affecting the sensitivity of noninvasive tests. IPG and PRG are reliable for evaluating patients with suspected DVT. However, patients with postoperative DVT have a high incidence of nonocclusive thrombi. Because noninvasive hemodynamic tests cannot identify accurately postoperative DVT, they cannot be used to generate epidemiologic data or as end points for studies evaluating efficacy of prophylaxis in patients undergoing total joint replacement, and anatomic studies of the deep venous system continue to be required.

Variability of venous hemodynamics with daily activity

PURPOSE This study was designed to evaluate changes in venous hemodynamics that occur in normal, symptom-free male and female volunteers, as a consequence of daily activity. METHODS Each leg of 25 symptom-free volunteers was prospectively studied twice in the early morning and twice in the late afternoon on 2 days. Air plethysmography was used to evaluate venous volumes, venous valvular function, calf muscle pump function, and the noninvasive equivalent of ambulatory venous pressure. RESULTS There was significant change in venous valvular function (venous filling index) indicating progressive insufficiency in the late afternoon compared with the results of the morning studies (p = 0.039). This was demonstrated by a shortened venous filling time (p = 0.033) but not a change in venous volume (p = 0.794). Calf muscle pump function and ambulatory venous pressures remained constant. Although there were significant leg volume and ejection volume differences at baseline in male volunteers compared with female volunteers, no gender differences were evident as a result of daily activity. Five of 25 (20%) volunteers and seven of 50 (14%) extremities had normal venous refill times and venous function index in the morning, which became abnormal in the afternoon, indicating deterioration of venous valve function. CONCLUSIONS Venous hemodynamic changes occur normally as a consequence of daily activity and seem to result from valvular dysfunction. This occurs in men and women and can alter diagnostic conclusions in 20% of otherwise normal patients. These findings have important implications for venous testing and accurate patient evaluation. However, extrapolation of these data to patients with established venous disease should not be made.

Venous Duplex Imaging for the Diagnosis of Acute Deep Venous Thrombosis

Acute deep venous thrombosis (DVT) continues to be a common clinical problem requiring objective evaluation. Hemodynamic testing for acute DVT has been popular, but is inadequate for evaluating asymptomatic patients and symptomatic patients with isolated calf vein thrombi. Venous duplex imaging (VDI) has rapidly gained in popularity, and is generally accepted to be the noninvasive technique of choice for the evaluation of patients with acute DVT. Twenty-five reports evaluate gray-scale venous duplex imaging versus ascending phlebography in 2,781 symptomatic patients. The sensitivity for proximal DVT and calf DVT is 96 and 80%, respectively. Seven reports review the use of VDI for surveillance in 857 asymptomatic patients, with an overall sensitivity of 76% for proximal DVT and of 11% for isolated calf vein thrombosis. The results of color-flow duplex appear to be somewhat better; however, the numbers are considerably smaller. The results for identification of calf vein thrombosis in asymptomatic surveillance patients continue to be poor. VDI appears to be the best noninvasive diagnostic test for acute DVT, and may challenge ascending phlebography as the best diagnostic test for proximal DVT in symptomatic patients, although it will miss 20% of isolated calf DVT. VDI appears to be the best noninvasive screening technique for high-risk asymptomatic patients under surveillance; however, additional correlative studies with ascending phlebography are required. The addition of color Doppler images appears to have improved results, although these higher sensitivities may be the consequence of improved experience as much as the addition of color to the image.

Venous outflow of the leg: Anatomy and physiologic mechanism of the plantar venous plexus

PURPOSE Mechanisms of venous outflow from the leg and foot have not been clearly defined. The purpose of this study was to evaluate the anatomy and physiologic mechanism of the plantar venous plexus and its impact on venous drainage from the tibial veins. METHODS Fifty phlebograms that contained complete foot and calf films were reviewed. On lateral films, the number of veins in the plantar venous plexus and its tibial outflow tract were counted. The length and diameter of the longest vein in the plantar venous system and the length of the foot arch were measured. The ratio of the length of the plantar venous plexus to the arch length was calculated. The presence or absence of valves within the plexus was recorded. Plantar venous plexus outflow was evaluated by an duplex ultrasonographic scan of the posterior tibial, anterior tibial, and peroneal veins during intermittent external pneumatic compression of the plantar surface of the foot. RESULTS The plantar venous plexus was composed of one to four large veins (mean, 2.7 veins) within the plantar aspect of the foot. The diameter of these veins was 4.0 +/- 1.2 mm. The veins coursed diagonally from a lateral position in the forefoot to a medial position at the level of the ankle, spanning 75% of the foot arch. Prominent valves were recognized within the plantar veins in 22 of 50 patients. The plexus coalesced into an outflow tract of one to four veins (mean, 2.5 veins) that flowed exclusively into the posterior tibial venous system. Small accessory veins that drained the plantar surface of the forefoot flowed into either the posterior tibial or peroneal veins. This pattern of selective drainage of the plantar venous plexus was confirmed by duplex imaging. Mechanical compression of the plantar venous plexus produced a mean peak velocity in the posterior tibial veins of 123 +/- 71 cm/sec, in the anterior tibial veins of 24 +/- 14 cm/sec, and in the peroneal veins of 29 +/- 26 cm/sec. CONCLUSIONS The plantar venous plexus is composed of multiple large-diameter veins that span the arch of the foot. Compression of the plantar venous plexus, such as that which occurs during ambulation, is capable of significantly increasing flow through the posterior tibial venous system into the popliteal vein. Its function may be integral to venous outflow from the calf and priming of the more proximal calf muscle pump.

Transcranial Doppler ultrasonography in siblings with sickle cell disease

Summary. The risk of stroke in sickle cell disease (SCD) may be influenced by either genetic or environmental factors. Elevated blood flow velocity in the large cerebral arteries, detected by transcranial Doppler (TCD) ultrasonography, predicts an increased stroke risk in children with SCD. We undertook this study to investigate the possibility of a familial predisposition to elevated cerebral blood flow velocity, a surrogate marker for stroke risk. We analysed the results of TCD studies performed on 63 children from 29 families that had more than one child with SCD. We assessed the association of elevated cerebral blood flow velocity with sibling TCD results as well as age and haemoglobin level, which are factors known to affect cerebral blood flow velocity. Positive or negative TCD results were highly correlated between family members (r = 0·61). The presence of a sibling with a positive TCD result was significantly associated with an elevated cerebral blood flow velocity in other siblings with SCD (odds ratio = 50·7, 95% confidence interval 10·1–253·7, P < 0·001). Furthermore, children who had a sibling with a positive TCD result had a significantly higher TCD velocity than children with SCD but without a sibling who were matched for age, sex, genotype and haemoglobin level. Our results are consistent with a familial predisposition to cerebral vasculopathy in SCD.