chapter 26 pulmonary vascular disease

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Chapter 26

Pulmonary Vascular Disease

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Learning Objectives

State how many patients develop venous thromboembolism each year.

Describe how and where thromboemboli originate.

Describe how pulmonary emboli alter lung and cardiac function.

Identify the clinical features and diagnostic findings associated with pulmonary embolism (PE).

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Learning Objectives (cont.)

Describe how PE is diagnosed and managed. Describe the hemodynamic findings

associated with pulmonary hypertension. Describe the possible mechanisms believed

to be responsible for the onset of IPAH. State who is at risk of the development of

IPAH.

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Learning Objectives (cont.)

Identify the clinical features associated with IPAH.

Describe the treatment used to care for patients with IPAH.

Describe the pathogenesis and management of pulmonary hypertension associated with COPD.

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Introduction

Pulmonary Vascular Disease Pulmonary vasculature is affected by pulmonary &

nonpulmonary disorders Degree of pulmonary hypertension is determined

by severity of underlying disease Nonpulmonary causes include

• Heart disease• Connective tissue diseases • Venous thromboembolic disease

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Introduction (cont.)

Venous Thromboembolic Disease Includes deep vein thrombosis (DVT) & pulmonary

emboli (PE) Major national health problem

• Up to 300,000 new cases annually (U.S.)

• 1/3 die in first hour of onset of symptoms (PE)

• >70% of patients who die of PE are not suspected before death

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Pathogenesis

PEs are most often detached portions of venous thrombi Most often (86%), thrombi form in deep veins

(DVT) of legs or pelvis Conditions that favor thrombus formation

(factors known as Virchow’s triad) Venous stasis: i.e., immobilization in hospital Hypercoagulable states Vessel wall abnormalities

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The three components that make up Virchow’s Triad are:

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Pathology

Stasis in conjunction with trauma or presence of toxins results in thrombi

Thrombus fragment travels to lungs resulting in PE

PE is most frequent in lower lobes & right lung

Pulmonary hemorrhage or infarction are rare (<10%) Bronchial circulation provides collateral circulation

limiting risk of infarction

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Pathophysiology

Massive PE causes death by cardiovascular failure, not respiratory failure

Emboli obstruct blood flow resulting in Alveolar deadspace Bronchoconstriction Decreased surfactant production Hypoxemia Pulmonary hypertension Shock (saddle embolus)

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Clinical Features

No specific signs or symptoms Anticoagulation is started on suspicion of PE &

stopped only when PE is ruled out Most common symptom is dyspnea

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Clinical Features (cont.)

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What are the most common symptoms associated with PE?

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Clinical Features: Chest Film

Rules out other life-threatening conditions Radiograph is abnormal in 80% of cases

Enlargement of right pulmonary artery (66%) Elevation of diaphragm (61%) Cardiomegaly (55%) Small pleural effusion (50%) Patchy or rounded infiltrates next to pleural

surface are less common but characteristic of PE

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Clinical Features: ECG & ABGs

ECG rules out other life-threatening conditions

ECG often abnormal but nonspecific Tachycardia, ST-segment depression most

common ABG findings most commonly show

hypoxemia & hypocapnia 15% to 25% of patients have PO2 >80 mm Hg

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Clinical Features: D-dimers

Sensitivity of 97% to 100% for PE Specificity of 39%, so its use with

comorbidities is limited Level <500 mg/L rules out PE (98%)

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Diagnosis of DVT

Testing for lower extremity DVT Venography

• Standard diagnostic tool

• Injection of dye

Impedance plethysmography • Noninvasive, sensitive, & specific

Compression ultrasonography• Noninvasive, sensitive, & specific

• Test of choice for diagnosis of DVT

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Diagnosis of DVT (cont.)

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Diagnosis of PE

Three tests available1. V/Q scan

2. Helical/Spiral CTA

3. Pulmonary angiography

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The most commonly used (definitive) test for diagnosing a PE is:

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Diagnosis of PE: V/Q Scan

Ventilation scan: Radioactive gas inhaled Perfusion scan: IV push of radioisotope-

tagged albumin Gamma radiation produced by radioisotopes

show distribution of blood flow & ventilation Areas with blood flow or ventilation scan “hot” Areas with ventilation (hot) but no perfusion (cold)

suggest presence of PE

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.. ..

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Diagnosis of PE: Helical/Spiral CTA

Principal diagnostic tool when used with IV contrast

Equal to scan if combined with D-dimer

Generally unable to detect smaller PE Advantage of helical/spiral CTA is its ability to

provide alternate diagnoses

V/Q V/Q . . . .

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Diagnosis of PE: Helical/Spiral CTA (cont.)

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Diagnosis of PE: Helical/Spiral CTA (cont.)

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Diagnosis of PE: Pulmonary Angiography

Used if scan & spiral CT fail to identify PE Low risk-to-benefit ratio justifies use of

procedure Catheter is threaded so tip passes through right

heart & into pulmonary artery Radiopaque dye is injected

V/QV/Q . . . .

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Diagnosis of PE: Pulmonary Angiography (cont.)

Fluoroscope monitors progress of dye Abnormalities include filling defects & abrupt

ending of arteries

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Treatment: Prophylaxis of DVT

High mortality justifies prophylactic treatment Moderate- to high-risk patients include those

Undergoing joint replacement With acute spinal injury or ischemic stroke With myocardial infarction or heart failure Who are MICU patients (i.e., pneumonia)

Treatment is anticoagulant therapy Heparin or fondaparinux is most commonly used

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Management of DVT

Heparin is standard therapy Immediate action Does not lyse existing clots but prevents clot

growth & formation Thrombolytic agents

Streptokinase, urokinase, TPA Actually lyse or destroy PE Not routinely used High risk of limb gangrene Risks & benefits not well established

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Management of PE

Similar regimen to DVT First-line heparin followed by oral coumarin

Supportive measures include Oxygen therapy Analgesia Hypotension & shock are treated with

vasopressors & fluids In persistent hypotension due to massive PE,

thrombolytics are indicated

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Pulmonary Hypertension

Pulmonary arterial hypertension (PAH) Mean pulmonary artery pressure (MPAP) >25 mm

Hg at rest OR MPAP >30 mm Hg with exercise, , with increased pulmonary vascular resistance (PVR) & normal left ventricular function

Associated with congenital heart disease, collagen vascular disease, liver cirrhosis, etc

Idiopathic pulmonary arterial hypertension (IPAH) if no identifiable cause is found

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Pathogenesis: IPAH

Development of IPAH Genetic predisposition probably required Follows insult to arterial endothelium Damage results in vasoconstriction

• May be caused by abnormal transport of potassium & calcium

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Epidemiology: IPAH

3 times more common in women than men

7% of cases are familial

Most common between ages 20 & 50 years As only 33% of patients are alive in 5 years, it

is important to identify & aggressively treat this disorder

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Clinical Features: Symptoms of IPAH

Symptoms are vague, so misdiagnosis is common Initial symptom: dyspnea (60%) Angina (50%) Syncope (8%) Other symptoms include

• Cough, hemoptysis, hoarseness, & Reynaud’s phenomenon

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Clinical Features: Symptoms of IPAH (cont.)

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Management of Pulmonary Hypertension

Supplemental oxygen (SaO2 >90%) Anticoagulation with coumarin

Adjust to keep INR ~2 Vasodilators (calcium channel blockers)

May use digoxin & diuretics to manage side effects

Nitric oxide is preferred• Very short half life

• Does not affect cardiac output

• Enhances V/Q mismatching

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Management of Pulmonary Hypertension (Cont.)

Prostanoids is increasingly used as substitute for inhaled nitric oxide Epoprostenol Treprostinil Iloprost

Surgical Therapy Atrial Septostomy Lung transplantation is option for severe

hypertension

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Pulmonary Hypertension in COPD

~50% of elderly with COPD have significant pulmonary hypertension

Alveolar hypoxia causes vasoconstriction & eventually medial hypertrophy, fibrosis, & lumen narrowing Leads to hypertension

Severity of COPD correlates with severity of hypertension

Long term oxygen therapy is only treatment that improves survival among this patient population

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The main mechanism for PHTN in COPD patients is: