The Pathophysiology of CVI and DVT

Disorders of the Veins and Arteries
Pathophysiology of Chronic Venous Insufficiency and Deep Venous Thrombosis
The pathophysiology of Chronic venous insufficiency (CVI) is either obstruction or reflux of venous blood flow. It can develop from the protracted valvular incompetence of the superficial veins, deep veins or the perforating veins that connect them. In all these cases the result is venous hypertension of the lower extremities. The bicuspid valve which is located in the superficial and deep veins assists in ensuring that blood is pumped towards the heart and it prevents blood from refluxing towards the feet when the patient is standing in an upright position (Eberhardt & Raffetto, 2014). Perforating veins valve function by preventing the reflux of blood from the deep veins into the superficial veins. In normal conditions, when a patient is standing erect, venous return is pulsatile and the valves will open and close about 20 times per minute. Superficial vein valve failure occurs after the primary points of high leakage develop between the superficial systems and the deep system. This high pressure results in secondary valve failure when the normal superficial veins become widely dilated that the thin flaps of the venous valves will no longer make contact in the lumen of the vessel. With time these incompetent superficial veins will become visibly dilated and tortuous, and at this point, they are recognized as varicose veins.
Deep vein thrombosis (DVT) mainly develops in the calf veins and it grows in the direction of venous flow towards the heart. The venous valves are avascular and in conjunction with the reduced flow of oxygenated blood in the veins will predispose the endothelium to be hypoxemic. The endothelium around the valves will then respond by expressing adhesion molecules that will attract leukocytes (Line, 2001). The cells will transfer tissue factor to the endothelium, which will complex with activated factor VII in order to begin the coagulation cascade through the extrinsic pathway. In normal circumstances, there is a physiologic balance between the factors that promote and retard coagulation. However, any disturbance in this equilibrium will result in the coagulation process occurring at an expected time or in excess. In case there is a failure of the normal coagulation mechanism it might result in hemorrhage.
Venous thrombosis is a condition that occurs when there is development of a blood clot in the vein. However, when a clot forms in an artery it is referred to as arterial thrombosis. This is a dangerous condition because it can stop blood flow to the major organs like the brain or the heart.
Impact of Obesity on The Pathophysiology of CVI and DVT
Having excess weigh will add additional pounds of pressure on the body, which can cause serious exertion on the veins and their valves. If there is too much weight pushing down on the lower half of the body, there will be high pressure in the superficial veins and this will lead to them dilating and increasing in diameter. The femoral vein diameter is significantly greater in obese patients as compared to non-obese patients. This can lead to vein wall distension. The superficial veins are also faced with a higher outflow resistance in obese individuals. With more pressure from the upper body, it results in more pressure being needed to move blood from the lower part to the heart (SPIRIDON & CORDUNEANU, 2017). This makes the valves weaker due to the increased pressure required to pump blood outward. The result is weakened valves and there is increased reflux since less blood is being pumped out as compared to the blood flowing back.
The presence of extra fat around the belly tends to prevent blood from flowing easily through the deep veins and this would result in the formation of blood clots. The body has a natural function of clearing blood clots, which would be impacted because there are chemical changes that take place in the body of obese individuals that leads to inflammation. This would block the normal flow of blood and the natural clearing of blood clots would also be impacted. Therefore, there might be more blood clots being formed and the natural mechanism for clearing blood clots will become overwhelmed.
Diagnosing CVI in obesity will require a clinical examination. One can use a Doppler to listen to the blood flow. However, the most accurate exam is the venous duplex ultrasound scan, which will provide an accurate image of the patient’s vein. The image will show if there are any blood clots or if there is any improper vein valve function. One can also use an MRI or CAT scan in order to rule out any other causes of leg swelling. Diagnosis of DVT will begin by analyzing the overall health of the patient. The physical examination will involve checking the patient's legs for any signs of DVT. The patient's blood pressure, heart, and lungs will also be checked. Diagnostic tests might also be recommended and the most common is the use of ultrasound. In case the diagnosis is not clear then a venography is done.
For obese patients with CVI, the doctor will recommend a diet and lifestyle change in order to reduce weight. Compression therapy will also aid in increasing pressure of the skin and the underlying structures in order to counteract the force of gravity. Pharmaceutical treatment will involve using a sulodexide agent that has polypharmacological actions that target several sites that are involved in the pathogenesis of CVI. Treatment for DVT will involve stopping the blood clot from getting bigger, preventing the blood clot from breaking off and moving to the lings, and reducing the patient's chance of having another blood clot. The use of anticoagulants is the most common medicine for treating DVT. This is a blood thinner that decreases the blood's ability to clot and they also prevent the existing blood clots from getting bigger.

Mind Map for CVI




Mind Map for DVT




References

Eberhardt, R. T., & Raffetto, J. D. (2014). Chronic venous insufficiency. Circulation, 130(4), 333-346.
Line, B. R. (2001). Pathophysiology and diagnosis of deep venous thrombosis. Paper presented at the Seminars in nuclear medicine.
SPIRIDON, M., & CORDUNEANU, D. (2017). Chronic Venous Insufficiency: a Frequently Underdiagnosed and Undertreated Pathology. Mædica, 12(1), 59.