Ch. 19 Disorders of the Venous System

CAPRIOTTI DAVIS ADVANTAGE for PATHOPHYSIOLOGY

Introductory Concepts and Clinical Perspectives

Overview

  • Second Edition, F.A. Davis Company, Copyright ©2020 F.A. Davis Company.

Chapter 19: Disorders of the Venous System

Venous Disorders

Common Conditions

  • Venous disorders range from mild (varicose veins) to serious (DVT: deep vein thrombosis).

Major Vein Disorders

  • Major disorders include:

    • Venous insufficiency

    • DVT (Deep Venous Thrombosis)

    • Varicose veins

    • Venous ulcers

Anatomy and Physiology of Veins

Characteristics of Veins

  • Veins are:

    • Thin-walled and flexible

    • Function to return blood to the heart

    • Operate as a low-pressure system

    • Contain valves to prevent backflow

Structure of Vein Walls

  • Vein walls have three distinct layers:

    • Tunica intima:

    • Composed of endothelial cell lining

    • Tunica media:

    • Contains a thin layer of smooth muscle

    • Tunica adventitia:

    • The exterior layer composed of connective tissue

Types of Veins

Two Systems of Veins

  • Superficial Veins:

    • Small diameter

    • Located in the skin and subcutaneous tissues

    • Drain into deep veins

  • Deep Veins:

    • Large diameter

    • Empty into inferior and superior vena cava

  • Perforating Veins:

    • Connect superficial and deep vein systems

Function of Veins

  • Veins do not pump blood but work against the gravitational pull.

  • Use skeletal muscle action and valves to facilitate blood return to the heart.

  • Veins have a large capacity but are susceptible to blood stasis.

  • The strength of veins may have a hereditary component, indicating familial predisposition to conditions like venous insufficiency.

Venous Insufficiency

Overview

  • Deep or superficial veins can become insufficient.

  • Superficial vein distension may lead to varicose veins.

  • In deep veins, increased hydrostatic pressure can result in tissue edema.

  • Conditions leading to venous insufficiency:

    • Obesity

    • Pregnancy: may weaken valve leaflets in veins

Deep Venous Thromboembolism (DVT)

Definition

  • DVT includes both deep vein thrombosis and pulmonary embolism (PE).

  • Incidents of hospital admissions for DVT are increasing, likely due to enhanced detection methods.

Virchow's Triad

  • A key concept related to DVT includes three components:

    • Venous Stasis: Impaired blood flow

    • Vascular Damage: Injury to the vessel wall

    • Hypercoagulability: Increased tendency of the blood to clot

Examples of Virchow's Triad Conditions

  • Venous Stasis:

    • Sedentary behavior, immobility

  • Venous Injury:

    • Trauma or surgery, especially orthopedic (may occur in 30% to 80% of postoperative patients)

  • Hypercoagulability:

    • Cancer, use of estrogen, smoking

DVT Progressing to Pulmonary Embolism (PE)

Mechanism

  1. Blood stasis leads to thrombus formation.

  2. Thrombus travels into the inferior vena cava, then to the right atrium.

  3. From the right atrium, the thrombus enters the pulmonary artery.

  4. In the pulmonary artery, the thrombus is referred to as a pulmonary embolism (PE).

Consequences

  • PE can obstruct blood supply to lung areas, potentially leading to fatal outcomes.

Clinical Presentation of DVT

Symptoms

  • Common presenting signs of DVT include:

    • Unilateral leg pain

    • Redness

    • Ropiness (the hardening of the vein)

    • Tenderness

    • Warmth over the affected vein

    • Possible swelling of the calf

Clinical Presentation of PE

Symptoms

  • Clinical signs of pulmonary embolism can vary significantly:

    • May be asymptomatic (silent)

    • Dyspnea (difficulty breathing)

    • Chest pain

    • Tachycardia (increased heart rate)

    • Hypotension (low blood pressure)

    • Hemoptysis (coughing up blood)

Diagnosis of DVT and PE

Challenges in Diagnosis

  • DVT cannot be diagnosed based solely on symptoms, as they can often be absent.

  • Imaging studies are not always practical for DVT evaluation in all suspected patients.

Diagnostic Techniques for DVT

  • Duplex Ultrasonography:

    • A combination of ultrasound and Doppler blood flow evaluation.

  • Impedance Plethysmography (IPG):

    • Measures blood volume in the extremity.

  • CT Venography and MRI:

    • These can be used as a definitive test in some situations.

D-Dimer Testing

  • The D-dimer test measures fibrin degradation products and is useful for ruling out the presence of DVT.

  • D-dimer levels can remain elevated for about 7 days in cases of DVT and PE.

  • Well's Criteria:

    • A scale (0 to 3) for assessing clinical signs of DVT, such as leg swelling.

Summary of D-Dimer and Well's Criteria

  • A negative D-dimer and a Well's score less than 2 can effectively rule out DVT.

  • Positive D-dimer and a Well's score greater than 2 necessitate duplex ultrasonography confirmation.

Diagnosis of PE

  • The best diagnostic method for PE is high-resolution multidetector computed tomographic angiography (MDCTA).

  • A V-Q scan (ventilation-perfusion scan) is also utilized.

Treatment of DVT

Preventive Strategies

  • Preventive measures include:

    • Sequential venous compression devices

    • Antiembolism stockings

    • Elevation of affected extremities when possible

Treatment Protocols: Anticoagulants

Goals

  • Anticoagulant therapy primarily aims to prolong clotting time.

Medications

  • Various medications can be used, including:

    • Factor Xa inhibitors

    • Direct thrombin inhibitors

    • Low molecular weight heparin

    • Unfractionated heparin

    • Warfarin

Varicose Veins

Definition

  • A varicose vein, also known as a varicosity, is characterized as an abnormally dilated superficial vein.

Characteristics of Varicose Veins

  • Varicosities are more likely to form in superficial veins due to high internal pressure that weakens valves.

  • Factors that increase pressure include:

    • Prolonged standing or sitting

    • Pregnancy

    • Obesity

  • Prevalence of varicose veins escalates with age and is more common among women.

Treatment Options

  • Treatment for varicose veins may include:

    • Surgical removal of superficial veins

    • Endovenous ablation using energy or radiofrequency

    • Sclerotherapy ablation involving the injection of a sclerosing agent into the vein

    • Use of elastic, supportive stockings

Comparison: DVT vs. Varicose Veins

DVT

  • Involves deep veins, characterized by thrombus (clot).

  • Associated with Virchow’s triad:

    • Venous stasis, vascular damage, hypercoagulability.

  • Symptoms may include unilateral leg pain, redness, ropiness, tenderness, warmth over a vein, and swelling.

  • Significant risk of pulmonary embolism.

  • Treatment involves anticoagulants.

Varicose Veins

  • Involves superficial veins, characterized as abnormal dilated veins.

  • Caused by elevated pressure within superficial veins that weakens valves, exacerbated by prolonged standing or sitting, pregnancy, and obesity.

  • Treatment may include supportive stockings or surgical interventions such as surgery or ablation.