Chapter 23 - Vascular lab - venous duplex Flashcards
Venous duplex transducer frequency
5-10 MHz 3-5 MHz for deeply located vessels IVC and iliac vein or obesity
Normal venous flow with respiration
Phasic flow inspiration = diaphragm moves down, intraabdominal pressure increased, intrathoracic pressure decreased - decrease venous return from LE - increase venous return from UE expiration - increase venous return from LE - decrease venous return from UE
Augmentation maneuvers on venous duplex
1) calf pump 2) manual distal compression
Rate of progression or recurrent thrombosis in patients with symptomatic calf-vein DVT
15-20% in 3 months
Timing of follow-up duplex in patients not on anticoagulation with isolated calf vein thrombi
2 weeks
Sen and spe for duplex on UE DVT
sensitivity 84-97% spe 93-96%
Ultrasound features to determine venous thrombus age
TABLE 23.3
Terminology to describe chronicity of venous thrombosis
Acute DVT Venous thrombosis indeterminate age chronic postthrombotic change
Ultrasonic elastography describe
Use ultrasound imaging to measure soft tissue strain to objectively assess mechanical properties of tissue (hardness/stiffness)
Define elasticity
tendency of material to resume original size and shape after deformation
Define strain
Changes in size or shape
Define stress
force acting on an area
Three moduli that describe elasticity
1) Young modulus - longitudinal elasticity = ratio of stress to strain 2) shear or torsion modulus = rigidity 3) bulk or volume modulus = volume elasticity
Define acoustic radiation force impulse imaging and how it works
ARFI uses energy of insonated US to move tissue at microscopic level - focused US beam pass through soft tissue - mainly attenuated through absorption - some create tissue movement causing deformational stress - greater effect on softer tissues
Two types of elastography to assess thrombus elasticity
Shear wave elasticity imaging (SWEI) Shear wave induced resonance elastography (SWIRE)
Finding of the DACUS study on recurrent DVT
Duration of anticoagulation based on compression ultrasonography residual thrombus in proximal veins were associated with increased risk of recurrent thrombus after DVT
Risk of recurrent thrombosis in cancer patients with DVT after 6 months of anticoagulation
15% in 1 year
PROLONG study on recurrent DVT
Elevated D-dimer at 1 month after anticoagulation withdrawal associated with recurrence residual venous obstruction not associated
Rate of vein postthrombotic abnormalities after DVT at 3 months and 1 year
80% 3 months 50% 1 year
Define suppurative thrombophlebitis
Bacterial infection of thrombosed vein
Trousseau sign of malignancy
Recurrent, migratory thrombosis in superficial veins including uncommon sites (torso, UE) Associated with adenocarcinoma especially pancreas or lung
Ultrasound exam pre-op on AVF maturity and usability
Assisted primary patency 1 year 80 vs 65%
Characteristics considered suitable for use as bypass conduit in vein
1) compressible at all level 2) no intraluminal echoes 3) no thickened walls 4) > 0.25 cm 5) uniform caliber without tortuosity 6) no varicose segments or multiple branches 7) not superficial to fascia
Three levels on the diagnostic assessment for chronic venous disorder
Level I = office visit with H+E, handheld doppler Level II = duplex, plethysmography Level III = ascending, descending venography, venous pressure measurements, CTV, MRV (invasive)
Frequency of ultrasound probe to use for venous exam in lower leg
4-7 MHz
Minimum venous flow velocity before valves will close normally
> 30 cm/s
Maneuvers during venous duplex exam
Valsalva Manual compression Deflation of pneumatic cuff with rapid < 0.3 s deflation
Normal cutoff for retrograde venous flow
> 1 second is deep femoral reflex > 0.5 s for superficial vein and calf deep vein > 0.35 s for perforator ALTERNATIVELY use 0.5 sec for everything
Minimize size of perforator veins to have valves normally
> 1 mm
Size of perforator vein associated with reflux
> 3.5 mm (90% will reflux)
