Duplex ultrasound sonography is the best choice for evaluation of venous reflux in the lower extremities. It is inexpensive, noninvasive, and generally acceptable to the patient. It provides direct visualization, localization and quantitation of venous reflux with a surprisingly high sensitivity (95%) and specificity (100%). Duplex ultrasound findings have been confirmed by angioscopic observation of incompetent vein valves in advanced chronic venous insufficiency. Yamaki has demonstrated that high peak reflux velocities (>30 cm/s), reflux duration greater than 3 s and an enlarged valve annulus measured by duplex ultrasonography at the saphenofemoral junction are all closely related to angioscopically deformed and incompetent terminal valves (types III and IV of Hoshino).
Foam sclerotherapy actually began before the development of ultrasound imaging. Phlebologists of the 1950s developed ways of producing foamed sclerosants and observed the distribution of therapeutic foam by sensing crepitus. However, all credit for the origination of foam sclerotherapy, as we know it today, goes to Juan Cabrera of Granada, Spain. It was he who combined the manufacture of fine foam with administration of the agent under ultrasound guidance.
Pretreatment assessment
The evaluation should always begin with confirmation of the medical history. A family and personal venous history are of great importance. In the personal history, the reasons for the treatment should be confirmed. The patient's view of the objectives of the procedure should
be recorded. Symptoms such as aching heaviness, limb fatigue, itching and burning pain are typically present and these should be recorded. Similarly, a detailed recording of previous treatments and their failure will be of importance in seeking insurance coverage for the intervention. History of pregnancies and their number, as well as the number of deliveries and abortions, are of importance. Any limb trauma, fractures and confining illnesses should be recorded. A history of deep venous thrombosis and treatment must be paired with its method of diagnosis. A detailed description of previous venous treatments must be a part of the treatment record. Comorbidities, allergies and pharmacologic history must be documented. The body mass index is calculated from the patient's height and weight and should be recorded.
If a proper, standing, duplex reflux examination has not been done or is not part of the patient's record, it should be accomplished before treatment is initiated. The patient should be examined in a standing position for procedural planning, identification of the venous access site, and its relation to perforating veins, varicosities, and areas of tortuosity, stenosis or dilation.
In this preparatory phase, some anatomic landmarks should be clearly recognizable, including the femoral vein, saphenofemoral junction, saphenous compartment, great saphenous vein (GSV) and the variable small saphenous junction anatomy. This should be supplemented by cold light transillumination of the skin with a bright white light such as the "vein light," to identify reticular veins. A hand-held Doppler can serve to perform a confirmatory screening examination if a proper pretreatment reflux examination is part of the record.
Three levels of pathologic veins are evaluated using the methods just mentioned. Telangiectasias in the skin are visually inspected, reticular veins are transilluminated with the vein light, and varicosities and the saphenous veins with ultrasound. Clinical data should be integrated into the CEAP classification.
Equipment
The duplex ultrasound scanner should be able to detect blood flow rates as low as 6 cm/s. Dedicated high-resolution vascular scanners with color and/or power Doppler functions as well as the continuous-wave Doppler are available. Linear transducers in the range of 4-7 MHz are used for the pretreatment as well as the definitive examination. The inferior vena cava, pelvic veins and deep veins of the limbs in obese patients may be imaged with lower-frequency, 3 MHz transducers. Linear hockey-stick transducers in the range of 5-12 MHz will provide detailed imaging of smaller veins and perforating veins.
After the year 2000, advances in technology allowed duplex ultrsound scanners to become smaller, more transportable, and more operator friendly. These miniaturized devices feature transducers designed with advanced architecture that allow a single probe to image across a greater range of depths within an application and across applications. Thus, in many ways, the portable ultrasound instrument supplements the stethoscope in patient evaluation. The transducer for peripheral vascular examinations operates from 5 to 10 MHz and provides resolution from the skin surface to 7 cm in depth. The technology incorporates power Doppler sonography, tissue harmonic imaging and direct connectivity to a personal computer. The overall performance of miniaturized ultrasound devices is comparable to that of the more traditional and much larger ultrasound equipment that allowed establishment and growth of the vascular laboratory.
Venous testing and mapping
Not only is a detailed duplex ultrasound study of the normal and pathologic venous anatomy essential, but a map should be created to guide therapy. A detailed verbal description of the examination and its findings is useful for record purposes, but the map is most useful during therapy. A clear and illustrative graphic notation of significant vein diameters, anomalous anatomy, superficial venous aneurysms, perforating veins, and presence and extent of reflux should always be recorded during the examination.
As mentioned, the ultrasound examination is conducted with the patient standing. This position has been found to maximally dilate leg veins, and challenges vein valves. Sensitivity and specificity in detecting reflux are increased in examinations performed with patient standing rather than when the patient is supine. Supine examinations for reflux are unacceptable.
The veins are scanned by moving the probe vertically up and down along their course. Transverse scans are most informative, but a mental reconstruction must be created to record the venous map. Duplicated segments, sites of tributary confluence, large perforating veins and their deep venous connections are identified, as well as the very common superficial venous aneurysms. Location of abnormalities as measured in "centimeters from the floor" assists in preparing a therapeutic guide. Measurements from the medial malleolus are commonly recorded, but are not as precise. Transverse and longitudinal scans combined with continuous scanning provide a clear mapping of the venous system.
Patency of peripheral veins is usually assessed by compression of the vein with the transducer. Residual ancient thrombus, partial patency and extrinsic compression should all be noted in the verbal description of find-ings. Reflux is detected by flow augmentation with compression and release maneuvers of the thigh and calf. The Valsalva maneuver is used only at the saphenofemoral junction, because presence of a competent proximal valve negates the value of the examination.
Automated rapid inflation and deflation cuffs have been used, but are cumbersome. However, they do offer the advantage of a standardized stimulus, which allows timing of reflux. Although reflux greater than 500 ms is considered pathologic, this is only precisely accurate when a standard stimulus is applied.
The diameter of the saphenofemoral junction and femoral vein are recorded in preparation for radiofrequency VNUS Closure® and endovenous laser ablation. Important information is also gained from diameters of the GSV at mid-thigh and distal thigh (Figure 6.2a). Radiofrequency ablation is commonly used to treat veins from 2 to 12 mm in diameter, although diameters recorded with the patient standing do not apply when treatment is given with the patient supine.
The supragenicular, infragenicular or immediate subgenicular GSVs are often the access point for introduction of sclerosant foam. Therefore the depth of the GSV in these regions should be recorded.
Accessory saphenous veins by definition run parallel to the GSV in the thigh. It is imperative to map their course accurately and to note their communication with varices and eventual communication with GSVs, as well as their presence or absence of reflux with relationship to varicosities. The accessory veins are easily confused with the GSV during continuous longitudinal scanning when the saphenous vein appears to leave the saphenous compartment. This error is avoided when transverse scans are done. The GSV is scanned throughout the leg and the thigh so that its tributaries are identified.
The diameters of the popliteal vein and the small saphenous vein (SSV) are recorded at the junction, as well as diameters of the SSV along its course in the leg. Intersaphenous veins should be identified and the extreme variability of the SSV termination carefully recorded.
The pretreatment venous reflux examination also includes the mapping of exit and re-entry perforating veins (PVs), wherever they are identified. PV reflux is detected as outward flow duration greater than 350 ms during the release phase of the flow augmentation maneuver (distal compression has higher sensitivity in detecting PV reflux;. PVs should be accu-rately mapped in their different locations in the leg, and their positions should be measured as distances (cm) from the floor.
Ultrasound monitoring during sclerofoam treatment
The advent of foam sclerotherapy has added a powerful tool for treatment of chronic venous insufficiency. Endo thermic coagulation is caused by the generation of heat, which is applied to the endothelial surface of targeted veins. Sclerosant foam has a similar end result: stripping
off the endothelium. Foam agents provoke endothelial damage by several mechanisms. They change the surface tension of the plasma membrane (detergents) and/or the intravascular pH and osmolarity. The final result is a chemical fibrosis of the treated vessel.
The endovenous techniques accomplish this by heat. It is been suggested that the coagulation process is related to the intravascular vaporization of blood (steam) during laser therapy, with intimal denudation and collagen fiber contraction. Vein wall thickening and rapid reorganization of the vessel to form a fibrotic cord follows. If the endothelium is destroyed, the targeted vein is closed permanently. Venous occlusion is usually visualized within 10-20 s of the electromagnetic or chemical stimulus. Both thermal and the chemical techniques have been proven to be safe and effective. Percutaneous introduction of foam, laser fiber and the RF catheter have made surgical intervention obsolete because of elimination of post-treatment pain, absence of cutaneous incisions and prevention of postprocedural disability Sclerosing foams, as described elsewhere in the book, are mixtures of gas and a liquid solution with surfactant properties. One of the intrinsic limits of liquid sclerosants in treatment of varicose veins is their dilution by blood, with reduction of their efficacy. Also, they are rapidly cleared by the moving blood stream. Sclerosing foams do not mix with blood, and instead remain in the vessel, where they strip off the endothelium. Persistence of the agent in the vessel causes an increased contact time with the intimal surface. Foam preparation is remarkably simple. The Tessari method is the most commonly used, but there is an increasing use of physiological gases as a substitute for room air.
As with endovenous ablation, the treatment starts with clear ultrasound mapping as described above. The GSV or the SSV can then be directly cannulated with an angiocath, an echogenic Cook needle or a butterfly needle. Nearly all descriptions of the technique explain direct ultrasound-guided access to the saphenous vein. In contrast, many experienced operators achieve a satisfactory and rapid obliteration of the GSV and SSV by cannulating a peripheral varicosity. Although the saphenous vein cannot be cannulated with a catheter by way of a varicosity, because of its angle of connection, there is no such obstacle to the flow of foam.
Foam functions as an efficient ultrasound contrast medium because of its air content. Its injection is easily monitored. Its ultrasound appearance is that of a solid hyperechogenic core with an accompanying acoustic shadow.
Foam is introduced into a varix or the saphenous vein with the patient supine. As the foam reaches the saphenofemoral junction as monitored by ultrasound, compression of the saphenofemoral or the saphenopopliteal junctions may be done in order to preserve foam in the limb. Such a maneuver does not prevent foam from reaching the systemic circulation, however.
Vasoconstriction and vasospasm in foam-filled veins can be induced by intermittent compression of the veins by the ultrasound transducer and by elevating the limb. This minimizes the blood content of the treated veins. Foam will be seen by ultrasound to flow distally in the elevated limb. As mentioned, it flows selectively through incompetent valves and is blocked by competent valves. Femoral vein compression and leg elevation have the effect of prolonging the action of the foamed sclerosant on the distal intima, improving the efficacy of the entire treatment. In addition, leg elevation for 5-10 minutes allows the foam to revert to its liquid state, so that foam particles will not reach the right atrium or a patent foramen ovale.
The femoral, popliteal and deep veins of the leg are scanned intermittently throughout the entire procedure. Foam particles are washed out of deep veins such as the gastrocnemius or tibial veins by flexion-extension maneuvers of the foot. Repetitive dorsiflexion of the foot completely clears the deep veins of any foam particles.
Despite much consternation, major thrombotic events have rarely been described with the use of sclerofoam. In a study of over 12 000 sclerotherapy sessions by Guex, over half of which involved foam, only a single femoral vein thrombus was encountered. Thromboses of the gastrocnemius, tibial and peroneal veins have been reported occasionally, and intra-arterial injections are even rarer.
Ultrasound sonography has confirmed the presence of the tangled network of small varicose veins, reticular varices and incompetent perforating veins under lipodermatosclerotic plaques and under venous ulcers. Ultrasound monitoring should confirm the fact that these vessels are filled with foam during treatment.
Ultrasound guidance is also used in treatment of incompetent perforating veins. Direct cannulation and controlled injection can be done easily if the primary treatment has failed to heal an ulcer or improve the condition of lipodermatosclerosis.6 Often, superficial peripheral veins can be directly injected with the objective of obliterating the attached perforator and its network of the incompetent veins.
As other adverse events have been eliminated, skin discoloration remains a major deterrent to acceptance of foam sclerotherapy. It is usually accompanied by patent venous channels as shown here. These should be closed by repeat injections under ultrasound guidance Post-treatment assessment.
Post-treatment assessment
Early post-treatment duplex scanning should be performed. This is best done at 1 and 7 days postprocedure, looking for deep venous thrombosis. Many have eliminated the 1-day examination because deep venous thrombosis is uncommon. Successful obliteration of the saphenous vein is confirmed by its contraction to a residual diameter of
For more information, please visit http://www.SDVeinInstitute.com
Van Cheng, MD
Medical Director, San Diego Vein Institute
1011 Devonshire Dr. Ste B
Encinitas, CA 92024
760.944.9263
http://www.SDVeinInstitute.com
This post was made using the Auto Blogging Software from WebMagnates.org This line will not appear when posts are made after activating the software to full version.
沒有留言:
張貼留言