Page 292 - Libro 2

272 PART 4 — PERIPHERAL VENOUS
PATHOLOGY BOX 17-1
Ultrasound Finding of CVVI
B-Mode Color Flow (Grayscale) SpectralDoppler Imaging
• Vein diameter enlarged
• Valve sinuses enlarged
• Tortuosity, varicosities, or venous aneurysms may be present
• Saphenous veins and tributaries retrograde flow 􏰂500 ms
• Deep veins retrograde flow 􏰂1.0 s
• Perforating veins retrograde flow 􏰂0.350 ms
• Retrograde flow color • Turbulent
or multiple color patterns seen within valve sinuses
QUANTIFICATION OF REFLUX
Measurement of reflux duration is commonly pre- ferred to measurement of peak reverse velocity or reflux volume flow rate. A classical, commonly ref- erenced study was originally designed to describe normal values.39 In the vast majority of normal subjects, saphenous vein valves close in less than 500 ms. The valves of the deep femoropopliteal veins close in less than 1 second. Perforating vein valves close in less than 350 ms. Longer durations are com- monly considered as an abnormal reflux. A severely abnormal GSV typically has reflux durations longer than 2 seconds. The actual duration of reflux may depend on the diameter, the amount of venous blood volume stored distally, the strength and duration of distal compression, and characteristics of the distal venous network. Pathology Box 17-1 summarizes the duplex ultrasound findings of CVVI.
OTHER NONINVASIVE DIAGNOSTIC PROCEDURES
Two classical technologies, photoplethysmography (PPG) and air plethysmography (APG), have been used as a screening tool and as a quantifier of venous abnormality, respectively. Recently, another indirect test has been employed in this patient population. This newer test employs a “red” light detector to aid in superficial vein mapping.
VENOUS PHOTOPLETHYSMOGRAPHY
PPG testing should be considered a screening pro- cedure for the detection of reflux.40 Source of re- flux is mostly undetermined. A PPG transducer emits infrared light and detects the signal reflected back from the blood within the cutaneous vessels.
Compression/decompression maneuvers alter the quantity of blood under detection by the PPG. The amount of blood detected by the PPG is reduced when blood is pumped back toward the heart. Upon completion of the maneuvers, blood volume returns and the sensor displays the return.
Patient Position
The patient is examined in a sitting position with legs dependent. The PPG is placed against the skin in the medial aspect of the calf. A common placement is about 10 to 15 cm above the medial malleolus. Other positions may be used for additional testing. The PPG positioned on the posterior aspect of the lower calf would provide information about small saphenous vein reflux.
Technique and Required Documentation
Once the patient and the PPG transducer are ap- propriately positioned, the examination begins with recording a baseline tracing while the limb is relaxed and no muscular contractions are occurring. The next step is to produce emptying of the calf venous blood volume. This is done using muscular contrac- tions with flexion/relaxation of the foot. About 5 to 10 ft flexion maneuvers are common practice. The PPG tracing is recorded during these maneuvers. A resting horizontal line is usually placed near the top of a 5-cm wide strip paper. The tracing falls to the bottom of the strip paper during the flexion/relax- ation of the foot. The tracing returns to the baseline position during the recovery period with the foot at rest and leg relaxed. The timing of blood return to the region indicates the presence or absence of reflux. Tracings may be observed on a monitor, but paper graphic registration is recommended. A common re- cording speed is 25 mm/s or about 0.5 to 1 cm/min.
The test can be repeated with the use of a tour- niquet in an attempt to differentiate a superficial reflux from a deep system reflux. A tourniquet can be placed around the thigh or other location over the great saphenous vein. The tourniquet can also be used to occlude the small saphenous vein by placing the tourniquet around the upper third of the calf. Changes in the recording both with and without the tourniquets in place may indicate different portions of the venous system are incompetent.
Paper registry should be filled with information about (1) the instrument used; (2) the time scale; (3) the anatomical location of the PPG; (4) the rest- ing trace showing arterial pulses and stable base- line; (5) the clear tracing during foot flexion, usually toward the bottom of the registry; and (6) enough paper length documenting recovery time.