L 27 HTN Pulm

Pulmonary Hypertension

Definition

  • Pulmonary Hypertension (PH) is characterized by increased pressure in the pulmonary arterial circulation.

  • Defined as mean pulmonary artery pressure (mPAP) > 20 mmHg at rest, determined via cardiac catheterization.

  • Normal resting mPAP is < 20 mmHg.

  • Diagnostic ‘gold standard’ test for PH is right heart catheterization (RHC), although it is not always required.

  • Initial diagnostic test is often transthoracic echocardiography.

  • PH can be progressive and fatal if untreated and has many secondary causes.

Right Heart Catheterization

  • Procedure for diagnosing right heart pressures and evaluating the pulmonary circulation.

  • Catheter enters through the superior vena cava to access the right atrium and the pulmonary arteries.

Etiology of Pulmonary Hypertension

Common Causes

  1. Left heart failure (LV dysfunction)

  2. Parenchymal lung disease with hypoxia (disease affecting lung parenchyma)

  3. Others such as Obstructive Sleep Apnea (OSA), Pulmonary Embolus (PE), and connective tissue disorders.

Pathophysiology of Pulmonary Hypertension

  • Healthy pulmonary circulation is a large volume, low-pressure system.

  • Mechanical changes: narrowed, thickened, and stiff pulmonary arteries lead to increased pulmonary vascular resistance.

  • This increased resistance overloads the right ventricle, leading to hypertrophy, dilation, and eventual right heart failure.

Patient Presentation

Symptoms

  • Progressive dyspnea on exertion (DOE) and easy fatigability occur in almost all patients.

  • Atypical chest pain and unexplained syncope (usually exertional) may be present initially.

As PH Progresses

  • Symptoms worsen with right heart failure, presenting as:

    • Chest pain

    • Syncope

    • Palpitations

    • Cough

  • Physical findings may include:

    • Increased intensity of the second heart sound (P₂)

    • Jugular venous distention (JVD)

    • Pulmonic ejection click and tricuspid murmur

    • Liver congestion/hepatomegaly

    • Peripheral edema

Diagnosis of Pulmonary Hypertension

  • Diagnosis starts with clinical suspicion, followed by:

    • Transthoracic echocardiogram with Doppler (primary screening exam)

    • Chest X-ray (CXR), spirometry, Electrocardiogram (ECG), CBC, Brain Natriuretic Peptide (BNP) levels

    • Right heart catheterization to confirm the diagnosis

  • Identification and treatment of any underlying disorder is crucial, which may include:

    • Ventilation/Perfusion scan (V/Q scan) or pulmonary CT angiogram

    • Pulmonary Function Tests (PFTs)

    • Polysomnography

    • HIV testing, liver enzymes, and antinuclear antibody testing.

Classifications of Pulmonary Hypertension

WHO Group Classifications

  • The World Health Organization (WHO) classifies pulmonary hypertension into five groups based on etiology and mechanism.

WHO Group 1: Pulmonary Arterial Hypertension (PAH)

  • Comprises approximately 5-10% of PH cases and is secondary to various disorders.

  • Pathophysiology involves diseases localized to the pulmonary arteries leading to smooth muscle hypertrophy, structural changes, and endothelial dysfunction.

Common Causes of Group 1 PAH

  • Idiopathic

  • Heritable (BMPR2 gene defect)

  • Drugs and toxins

  • Connective tissue disorders, especially systemic sclerosis

  • Congenital heart disease (left-to-right shunts)

  • HIV infection

  • Portal hypertension due to chronic liver disease

  • Schistosomiasis, leading to granulomatous reaction in the lungs.

Prognosis for Group 1

  • Prognosis depends on a risk score. Factors influencing prognosis include age and gender; males and individuals over age 50 have poorer prognosis.

  • Main cause of death is right heart failure with circulatory collapse and respiratory failure.

Treatment for Group 1

  • Initial treatment options involve a combination of endothelin receptor antagonist (ERA, e.g., ambrisentan) and phosphodiesterase inhibitor (PDE-5, e.g., tadalafil) as first-line therapy.

  • Calcium channel blockers (e.g., diltiazem, nifedipine) may be viable in 10-20% of candidates after a trial during cardiac catheterization.

  • Soluble guanylate cyclase stimulators (e.g., riociguat) are also used.

WHO Group 2: Pulmonary Venous Hypertension

  • Description: Secondary to left heart disease, accounts for 65-80% of PH cases.

  • Includes left ventricular systolic or diastolic dysfunction, heart failure with preserved ejection fraction (HFpEF), and valvular heart disease affecting mitral and aortic valves.

Treatment

  • Treatment focuses on the underlying heart disease; left heart failure is typically managed with diuretics.

Prognosis

  • Prognosis is dependent on the underlying heart condition.

WHO Group 3: Pulmonary Hypertension due to Lung Disease

  • Associated with chronic lung disease or hypoxia, comprising approximately 10-20% of PH cases.

Included Conditions

  • Chronic Obstructive Pulmonary Disease (COPD)

  • Interstitial lung diseases

  • Pulmonary fibrosis and emphysema

  • Obstructive Sleep Apnea (OSA)

Prevalence & Prognosis

  • COPD patients with PH demonstrate poorer 5-year survival rates than those with COPD alone.

  • OSA is most commonly linked with PH.

Treatment

  • Treatment objectives include addressing the underlying lung disease and correcting hypoxemia.

  • Oxygen therapy is indicated for patients with hypoxemia.

  • Inhaled treprostinil has been approved for patients with interstitial lung disease.

WHO Group 4: Chronic Thromboembolic Hypertension (CTEPH)

  • Characterized by pulmonary artery occlusion caused by chronic thromboembolic obstruction.

Treatment

  • Management generally includes anticoagulation therapy.

  • Surgical thromboendarterectomy represents the only potentially curative option.

WHO Group 5: Multifactorial Mechanisms

  • Includes various causes leading to pulmonary hypertension due to unclear mechanisms.

  • Examples: compression of pulmonary vessels due to adenopathy or tumors, blood disorders like polycythemia vera, metabolic disorders like thyroid disease, and chronic kidney disease.

Treatment

  • Focus on managing the underlying condition.

Management for All PH Patients

  • All groups of PH patients should receive:

    • Diuretics as needed

    • Oxygen therapy as indicated

    • Lifestyle recommendations (e.g., exercise, smoking cessation)

    • Routine vaccinations

    • Early referral to specialized PH management centers.

  • Lung transplant options may be considered for patients if medical therapy fails.

  • Right ventricular function serves as the most important predictor of prognosis.

Summary of WHO Groups

  • Group 1: Pulmonary arterial hypertension (familial, idiopathic, associated with connective tissue diseases, HIV, portal hypertension, drugs, or toxins)

  • Group 2: PH with left heart disease

  • Group 3: PH associated with lung disorders or hypoxemia

  • Group 4: PH due to chronic thromboembolic disorders

  • Group 5: Miscellaneous factors including blood disorders, sarcoidosis, tumors, metabolic disorders.

Cor Pulmonale

Definition

  • Cor pulmonale is the right ventricular change in structure (dilation or hypertrophy) or function due to chronic lung disease or hypoxemia, often associated with group 3 pulmonary hypertension.

  • Can arise as a complication of pulmonary hypertension or other pulmonary diseases.

Pathophysiology

  • Loss of pulmonary capillary beds occurs with conditions like COPD or pulmonary embolism (PE).

  • Vasoconstriction in response to hypoxia or hypercapnia may occur.

  • Increased alveolar pressure and hypertrophy in arterioles are seen particularly in group 1 PH.

Presentation

  • Symptoms may include chronic productive cough, exertional dyspnea, wheezing, fatigue, weakness, dependent edema, cyanosis, clubbing, distended neck veins, tricuspid regurgitation, and liver enlargement (hepatomegaly) with ascites.

Diagnosis

  • Diagnosis typically relies on clinical suspicion, supported by echocardiography.

Pleural Effusions

Definition

  • Pleural effusions are characterized by the accumulation of excess fluid in the pleural space.

Causes

  • Over 50 benign or malignant conditions can cause pleural effusions, with common causes being cancer, infections, and heart failure.

Presentation

  • Pleural effusions may be asymptomatic or present with chest pain and dyspnea.

Diagnosis

  • Analysis of pleural fluid through thoracentesis with ultrasound guidance is crucial for diagnosis.

  • Thoracentesis is indicated for new findings of pleural effusion unless there is an obvious cause (e.g., uncomplicated heart failure).

Thoracentesis Conditions

  • Diagnosed conditions via thoracentesis and pleural fluid analysis include:

    • Malignancy

    • Empyema

    • Tuberculosis pleurisy

    • Fungal infection of the pleural space

    • Chylothorax (accumulation of lymph)

    • Urinothorax from urine leakage

    • Hemothorax (blood accumulation)

    • Following peritoneal dialysis.

Pleural Fluid Analysis

Classification: Transudates vs. Exudates

Transudate (Occurs from increased capillary hydrostatic pressure or decreased plasma oncotic pressure):

  • Examples: heart failure (most common), nephrosis.

  • Conditions extend to the pleural space and typically exhibit fluid movement from peritoneal or cerebrospinal fluid spaces.

Exudate (Occurs from increased vascular permeability or decreased lymphatic resorption secondary to inflammation):

  • Examples: infection and malignancy (most common), immunologic responses, lymphocytic abnormalities.

  • Movement of fluid from below the diaphragm is frequent.

Gross Appearance

  • Transudate: generally pale yellow/straw-colored and clear.

  • Exudate: may be bloody if malignant; may appear white/milky if due to chylothorax (lymph or fat).

Typical Analysis Components

  • Cell counts with differential

  • Total protein levels

  • LDH (Lactate dehydrogenase) levels

  • Glucose levels

  • Lipid analysis if chylothorax suspected

  • Gram stain and culture if infection is suspected

  • Cytology if malignancy is suspected.

Light’s Criteria Rule

  • Utilized to measure serum and pleural fluid protein and LDH levels.

  • Fluid qualifies as an exudate if one of the following is present:

    • Pleural fluid protein/serum protein ratio > 0.5

    • Pleural fluid LDH/serum LDH ratio > 0.6

    • Pleural fluid LDH > 2/3 the upper limit of normal for serum LDH.

Exudative Pleural Effusions Etiology

Common Causes

  • Empyema and pulmonary infections.

  • Second most common cause: malignancy (e.g., lung, breast, ovarian, lymphoma).

  • Hemothorax indicates trauma when HCT of pleural fluid > 50% of peripheral blood HCT.

  • Chylothorax may result from mediastinal tumor involvement by lymphoma or bronchogenic carcinoma affecting the thoracic duct.

Pleural Fluid Analysis Levels

  • Most transudates have < 3.0 g/dL protein.

  • TB pleural effusions (exudates) typically have protein > 4.0 g/dL.

  • An LDH level > 1000 IU/L indicates empyema, rheumatoid pleurisy, or some parasitic infections.

  • Triglyceride levels > 110 mg/dL support chylothorax diagnosis.

  • Glucose levels < 60 mg/dL suggest possible malignancy, TB, lupus, or esophageal rupture.

Management of Pleural Effusions

Treatment Options

  • Thoracentesis (can be repeated as needed).

  • Chest tube drainage may be employed.

  • Pleurodesis can obliterate the pleural space using a chemical irritant such as talc, particularly for recurrent effusions.

  • Treatment of underlying conditions is crucial for management.

Obstructive Sleep Apnea (OSA)

Definition and Features

  • OSA symptoms include:

    • Obstructive apneas

    • Hypopneas

    • Respiratory effort-related arousals

    • Daytime symptoms attributed to disrupted sleep (e.g., sleepiness, fatigue, poor concentration)

    • Signs of disturbed sleep such as snoring, restlessness, and resuscitative snorts.

Importance of Diagnosis

  • Patients with OSA are at risk for poor neurocognitive performance, with increased all-cause and cardiovascular (CV) mortality rates associated with severe untreated OSA.

Epidemiology

  • OSA is the most common sleep-related breathing disorder affecting:

    • 20-30% of males in North America

    • 10-15% of females in North America

  • Apnea-Hypopnea Index (AHI) > 5 events/hour is indicative of OSA, with higher prevalence noted due to obesity.

  • OSA prevalence is greater in African Americans, particularly in individuals under 35 years of age compared to Caucasians.

Risk Factors

  • Advancing age, male gender, obesity, and craniofacial abnormalities which affect the upper airway soft tissue (e.g., enlarged tonsils).

  • Additional risk factors include nasal congestion, smoking, alcohol use, and benzodiazepine/narcotic usage.

  • Increased prevalence detected in pregnancy, congestive heart failure (CHF), chronic lung disease, strokes, and end-stage renal disease.

Obesity as a Major Risk Factor

  • Obesity is the strongest risk factor for OSA, with prevalence rising alongside Body Mass Index (BMI).

    • A 10% increase in weight corresponds to a 6-fold increase in OSA risk.

    • Individuals with a BMI > 40 are also at risk for obesity hypoventilation syndrome (OHS).

Pathophysiology of OSA

  • OSA presents with recurrent functional collapse of the velopharyngeal and/or oropharyngeal airway during sleep, leading to significantly reduced airflow, hypercapnia, and hypoxemia.

  • This results in fragmented sleep, occurring during both REM and non-REM phases.

Clinical Presentation

  • Classic symptoms encompass: snoring, daytime sleepiness (common abstraction), nocturnal choking or gasping (most specific), restless sleep, periods of silence interrupted by loud snoring, fatigue, poor concentration, nocturnal angina, nocturia, and morning headaches.

Physical Findings

  • Common manifestations include:

    • Obesity

    • Crowded oropharyngeal airway

    • Large neck circumference

    • Hypertension

Diagnosis

  • In-laboratory polysomnography is the gold standard for diagnosing obstructive sleep apnea.

  • Home sleep apnea studies may also be utilized.

  • Diagnosis is established through a combination of obstructive apnea events during sleep and daytime symptoms of disturbed sleep.

Diagnostic Criteria in Adults

  • OSA is diagnosed if either of these criteria are fulfilled:

    • Five or more predominantly obstructive respiratory events per hour, coupled with one or more daytime symptoms such as sleepiness, nonrestorative sleep, fatigue, or insomnia symptoms; waking up with breath-holding, gasping, or choking; habitual snoring; and other breathing disturbances

    • Fifteen or more events per hour during polysomnography.

Complications and Consequences

  • Complications include decreased daytime alertness, cardiovascular morbidity, and mortality risks, including systemic hypertension, pulmonary hypertension, coronary artery disease (CAD), cardiac arrhythmias, heart failure, and stroke.

Association with Metabolic Syndrome

  • OSA is linked with metabolic syndrome, showcasing increased glucose levels, increased triglycerides, decreased HDL, increased waist circumference, arterial stiffness, and atherosclerosis.

  • The condition also contributes to Type 2 Diabetes Mellitus (T2DM) with insulin resistance.

  • Overall mortality rate is increased by 2-3 times in patients with OSA.

Treatment for OSA

  • OSA management is long-term and includes strategies to improve sleep quality and daytime functioning:

    • Weight loss for overweight individuals

    • Avoidance of alcohol and hypnotic medications.

    • Continuous Positive Airway Pressure (CPAP) therapy represents a cornerstone treatment.

    • Alternate therapies include oral appliances, upper airway surgery, and hypoglossal nerve stimulation.

Obesity Hypoventilation Syndrome (OHS)

Definition

  • OHS occurs in obese patients (BMI > 30) who develop awake alveolar hypoventilation, characterized by PaCO₂ ≥ 45 mmHg, not attributable to other causes.

  • Most OHS patients also have OSA.

Clinical Features

  • Symptoms parallel those of OSA but include more significant dyspnea on exertion (DOE).

  • Severe obesity (BMI > 50) can lead to right-sided heart failure, polycythemia, hypertension, CHF, and insulin resistance.

Diagnostic Tests

  • Monitoring serum bicarbonate levels: increased bicarbonate levels indicate chronic hypercapnia with a sensitivity of 92% for identifying OHS when > 27 mEq/L.

  • Oxygen saturation below 93% may indicate hypoxemia.

  • Consider screening with complete blood counts (CBC) for hemoglobin levels and thyroid function tests, glucose, and lipids.

Blood Gas Analysis

  • Criteria require the presence of hypercapnia during wakefulness with PaCO₂ ≥ 45 mmHg and hypoxemia with PO₂ < 70 mmHg.

Further Diagnostic Tests

  • PFTs are conducted to rule out obstructive lung diseases.

  • Polysomnography shows an AHI typically higher than 15 events/hour in OHS, revealing greater oxyhemoglobin desaturation compared to OSA.

  • Chest X-rays (CXR) are performed to rule out other conditions, and ECG is routine.

  • Echocardiography may be necessary if comorbid heart failure or pulmonary hypertension is suspected.

Diagnosis Criteria

  • OHS is diagnosed based on BMI > 30 kg/m², awake alveolar hypoventilation (PaCO₂ ≥ 45 mmHg), and absence of alternative causes for hypoventilation.

Treatment

  • The management of OHS includes:

    • Positive airway pressure (CPAP or BiPAP) to reduce nocturnal arterial carbon dioxide levels and reduce daytime PaCO₂.

    • Weight loss strategies, significant diet alterations, lifestyle modifications, or surgical intervention may be indicated for more severe obesity.

    • Identification and management of comorbid conditions such as COPD or hypothyroidism should be prioritized.

Preventing Complications

  • Patients are advised to abstain from alcohol, benzodiazepines, opioids, and barbiturates as these may worsen respiratory drive.

  • Supplemental oxygen should not be used as monotherapy due to potential for increasing hypercapnia; use in conjunction with CPAP is preferable.

  • Pharmacotherapy should be regarded as a last resort, with medications such as progestins or acetazolamide being considered only when necessary to stimulate respiration.