Pulmonary Hypertension Flashcards
Definition of PH
- Pulmonary hypertension is defined as a resting mean pulmonary arterial pressure of >25 mm Hg, measured by right heart catheterization.
- The subgroup of PH known as pulmonary arterial hypertension (PAH) adds the criterion that the pulmonary venous (or pulmonary capillary wedge) pressure must be <15 mm Hg.
Pulmonary arterial hypertension (PAH)
- Idiopathic PAH
- Inherited
- Drug or toxin induced
- Associated with connective tissue diseases, HIV infection, portal hypertension, congenital heart diseases, schistosomiasis
- Group 1
Pulmonary hypertension due to left heart disease
- Systolic dysfunction
- Diastolic dysfunction
- Valvular disease
- Group 2
- Pulmonary hypertension due to lung diseases and/or hypoxia
- 1 COPD
- 2 Interstitial lung disease
- 3 Sleep disordered breathing and alveolar hypoventilation disorders
- 4 Chronic exposure to high altitude
- Group 3
Chronic thromboembolic pulmonary hypertension (CTEPH)
- Group 4
Pulmonary hypertension due to unclear multifactorial mechanisms
- 1 Hematologic disorders (e.g., myeloproliferative diseases)
- 2 Systemic disorders (e.g., sarcoidosis)
- 3 Metabolic disorders (e.g., glycogen storage disease)
- 4 Other (e.g., tumor obstruction)
PA mean = (CO x PVR) + PCWP
From this equation, it is apparent that mean PA pressure is determined by: Right-sided cardiac output, AND Pulmonary vascular resistance, AND Mean pulmonary venous pressure/left atrial pressure (measured as PCWP)
3 Variables that Can Change and Cause PH
- Pulmonary Venous Pressure
- Pulmonary Vascular Resistance
- Right Sided Cardiac Output
Pulmonary Venous Pressure
Left ventricular systolic or diastolic dysfunction and mitral valve disease can increase pulmonary venous pressure.
Pulmonary Vascular Resistance
Conditions that decrease the area of the pulmonary vascular bed (e.g., pulmonary emboli, connective tissue diseases, interstitial lung disease, COPD) or induce hypoxic vasoconstriction (any lung disease producing hypoxia) increase pulmonary vascular resistance.
Right Sided Cardiac Output
Left-to-right atrial septal defects (ASD), left-to-right ventricular septal defects (VSD), and other systemic-to-pulmonary shunts increase rightsided cardiac output by increasing the right ventricular volume
PH Sequence of Events
Regardless of the cause, a predictable sequence of events occurs. The initial injury causes mild pulmonary hypertension. The elevated pressure induces additional damage to the pulmonary vasculature, which narrows the pulmonary vascular bed. The right ventricle hypertrophies in order to overcome the increased resistance. Vascular injury accelerates in the presence of elevated pulmonary artery pressure, which increases right ventricular afterload further. Eventually, the right ventricle dilates and fails. By this time, patients may have severe symptoms, including symptoms at rest.
Clinical Presentation of PH - Symptoms
• Symptoms
–Dyspnea on exertion
–Fatigue
–Chest pain/angina
–Syncope
–Ankle swelling
Clinical Presentation of PH - Physical Findings
• Physical Findings
–Pulmonic component of S2
- Increased intensity
- Increased splitting
–Tricuspid regurgitation murmur
–Right ventricular S4 or S3
–Increased JVP
–Peripheral edema
–Ascites
Right ventricular hypertrophy: marked right axis deviation, tall R wave in V1.
Pathogenesis Idiopathic / Inherited PAH
• PAH is related to genetic mutations in the bone morphogenetic protein receptor type 2 gene (BMPR2) and several other genes.
– Mutations in the BMPR2 gene occur in approximately 70% of families with a history of familial PAH and in nearly 25% of patients believed to have sporadic idiopathic PAH.
• BMPR2 is a member of the transforming growth factor beta family.
– The BMPR2 pathway induces apoptosis; hypothesis is that abnormal pathway activity in patients with mutations permits excess endothelial cell growth and proliferation in response to injury.
• Idiopathic PAH is a proliferative vasculopathy, characterized by vasoconstriction, cell proliferation, fibrosis, and thrombosis.
– Pathologic findings include intimal hyperplasia and fibrosis, medial hypertrophy, and in situ thrombi of the small pulmonary arteries and arterioles.
Vasoactive Therapy
Patients with PAH – Group I
• Calcium channel blockers
– Nifedipine, diltiazem, amlodipine
• Prostaglandins
– Prostacyclin analogues
– Epoprostenol
– Treprostinil – longer half-life, subQ administration/inhaled
– Iloprost - inhaled
• Phosphodiesterase 5 inhibitors
– Sildenafil
– Tadalafil
– longer half-life
• Endothelin receptor antagonists
– Bosentan
– Ambrisentan
• Soluble guanylate cyclase stimulant
– Riociguat
Calcium Channel Blockers
Calcium channel blockers reduce the influx of calcium ions into pulmonary arterial smooth muscle cells, thereby reducing calcium-mediated activity of the contractile mechanism.
Prostacyclin Analogues
Prostacyclin analogues (epoprostenol, treprostinil, and Iloprost) supplement deficient levels of prostacyclin caused by underexpression of endothelial prostacyclin synthase.
Endothelin Receptor Antagonists
Endothelin receptor antagonists (bosentan, ambrisentan) block the effect of endothelin at smooth muscle cell receptors
Phosphodiesterase 5 (PDE5) inhibitors
Phosphodiesterase 5 (PDE5) inhibitors (sildenafil, tadalafil) promote the activity of the nitric oxide pathway by reducing conversion of cyclic guanylate monophosphate (cGMP, a second messenger) to 5ʹ-guanylate monophosphate (an inactive product).
Guanylate Cyclase Stimulators
A recently introduced class of drugs activates the conversion of cyclic guanylate monophosphate (cGMP, a second messenger) to 5ʹ-guanylate monophosphate (an inactive product) pathway in the absence of nitric oxide by directly stimulating the activity of soluble guanylate cyclase. The only available drug in this category of guanylate cyclase stimulators is riociguat.
