Venous Disease Flashcards
How much blood volume is carried in the vessels?
60-64% total blood volume is in the veins
15% total blood volume is in the arteries
(12% in pulmonary blood vessels, 8% in heart, 5%in capillaries)
What is the anatomy of a vein?
The deep vein wall consists of three layers. The outside layer, called the Tunica adventitia, is made of collagen, vasa vasorum and nerve cells. The middle layer, or media, is comprised of smooth muscle surrounded by fibrous tissue. The inside layer, or intima, is made up of a single layer of endothelial cells which provide a nonthrombogenic surface for flowing blood (specialised to secrete thrombolytic substances). The venous valves are formed from folds of the intimal
What are the different types of veins?
Superficial
Deep
Perforating
Deep veins they run alongside the arteries, and as such, often share the same name. Veins are thin walled with low velocity phasic flow, that are easily dilated and compress with very little applied pressure Blood flows from the superficial veins into the deep veins. Perforating veins act as communicating veins between the deep and superficial systems. Unique to the veins are bicuspid venous valves, which permit unidirectional flow toward the heart.
What are some anatomical variations in the course of veins?
Bifurcations, branches and occasional bifid and trifid vessels
How does venous blood return to the heart?
- Heart – small contribution due to pressure gradient from 120mmHg as it leaves the heart to <10mmHg as it returns
- Skeletal muscle pump
- Valves
- Respiratory pump
What is the calf muscle pump?
Calf muscle pump is the motive force enhancing return of venous blood from the lower extremity to the heart. When calf muscles contract, blood is pushed unidirectionally to the heart, backflow prevented by bicuspid one way valves
What is the respiratory pump?
the changes in pressure on insp and exp will alter flow in the veins
During inhalation, the volume of the thorax increases, largely through the contraction of the diaphragm, which moves downward and compresses the abdominal cavity.
What is flow phasicity?
Normal venous waveforms are phasic with respiration meaning that they approach the baseline with inhalation and go lower below the baseline with exhalation. So flow ceases in the veins in the legs on inspiration due to increased pressure in the abdomen
How can you use Valsalva manoeuvre to assess patency?
VALSALVA – Can use this phasicity to assess patency of abdominal veins. Flow should cease on expiration due to increased pressure in abdomen
Name some venous diseases
Thrombosis
Paget-schroters disease
Post Thrombotic Disorders
Lower limb Deep Venous Insufficiency (reflux)
Thrombophlebitis
Pulmonary Embolism
Varicose Veins
Pelvic vein congestion syndrome/pelvic vein incopetence
Venous Ulcers
Klippel-Tranauney Syndrome
Parkes-Weber Syndrome
Arteriovenous malformation
Lipodermatosclerosis
Venous hypertension
What is DVT?
Blood clot, usually formed behind valves of deep veins obstructing blood
Thrombosis vs embolism
Thrombosis happens when a blood clot, or thrombus, grows in blood vessels. This can reduce blood flow. An embolus is any foreign material that travels within the body. If it becomes stuck and severely blocks the flow of blood, the issue is called an embolism.
What can DVT cause?
PE, Post-thrombotic syndrome
Most Common site of DVT?
IVC 1.6%
Iliac 4.7%
Femoral 27%
Popliteal 3.2%
Calf 63.5%
What are superficial veins?
The superficial veins are, by definition, located near the skin, superficial to the muscle. The main superficial veins usually travel without an accompanying artery within the tissue that separates the fascia from the muscle. Their job is not to be the primary channels for returning blood to the heart, but to get blood close to the skin surface so that the veins can help to regulate body temperature. They constrict when the environment is cold to help preserve body heat. When the body needs to cool down, they dilate to shunt large amounts of warm blood to the skin so that heat escapes from the body.
Although clots within the superficial veins pose less of a threat of producing a pulmonary embolism, clots can and do break loose from superficial veins and travel to the pulmonary arteries. These clots in the superficial system are less likely to cause major, clinically significant pulmonary embolism because they are usually smaller than clots found in the deep veins, and they are less likely to be dislodged because they are not surrounded by muscle. Examination of the superficial veins is still an important part of a complete evaluation of the lower extremity because superficial clots may become large (as the normally small superficial vein is expanded by the contained thrombus) and cause considerable discomfort. There is also potential danger that a superficial vein clot will extend into the deep system.
What are deep veins?
The deep veins are accompanied by an artery and are, by definition, surrounded by muscle. Their job is to act as the main conduits that transport blood back to the heart. Clots within the deep veins are more likely to produce a clinically significant pulmonary embolism because these clots are usually larger than those in the superficial system. Also, because they are surrounded by muscle, the chance of the clot being dislodged during muscle contraction is higher than for a clot in the superficial veins. For these reasons, the main focus in a lower extremity venous duplex examination is on the deep system.
What are perforating veins?
Perforator veins connect the deep veins with the superficial veins. Their job is to keep blood moving from the superficial system into the deep system. When they are working properly, they keep blood from pooling at the level of the skin. When they are not functioning well, blood can pool at the skin level and chronic stasis changes and ulcers may result. Although a complete examination of the lower extremity for the presence of DVT need not include a detailed evaluation of perforators, more attention is paid to them when the question of chronic swelling or venous stasis is being evaluated.
How to image veins for DVT?
If the vein is thrombus-free, it will compress completely so that the inner vein walls actually touch each other. When the vein collapses completely with light probe pressure, it can be determined to be unequivocally thrombus-free at that location ( Fig. 18.3 ). This is the key to venous duplex imaging of the veins. The pressure on the vein is released, and the vein will reopen. The examiner then moves the probe along the length of the vessel until the entire vein has been imaged in this way. It is important to ensure that these compression maneuvers are as close together as possible. If the cuts are too far apart, a major section of vein containing thrombus can be missed. As a rule, the smaller the cuts, the less chance there is of missing a thrombus. Color Doppler can be used to help visualize the veins in the transverse plane. Care must be taken to evaluate for compression with gray scale because color signals can obscure thrombus. Augmentation of the distal extremity also aids in the visualization of the veins and to demonstrate patency (discussed later).
What is echogenicity?
It is a descriptive term that can describe normal or abnormal findings. Usually refers to tissue or substances found in the lumen of the vein that reflect sound waves more strongly than the surrounding tissues.
How can a DVT be confirmed?
Normal veins will compress completely so that the inner vein walls actually touch each other. Thrombus is present within the vein when echogenic material is identified within the lumen of the vein and when full compression of the vein cannot be obtained. It is crucial to note that both of these things must occur together to make a definitive diagnosis of thrombus in the vein .
Incomplete compression of the vein may be caused by pelvic mass or adenopathy, the patient bearing down in response to painful probe compressions, poor patient positioning, compression being limited by a nearby bone, and other factors.
Examination of the lower extremity veins usually begins at the groin crease . Just above the crease, the main venous trunk is called the external iliac vein. As it crosses the groin crease, it becomes the common femoral vein
