Pulmonary Hypertension Flashcards
Technical definition of pulmonary HTN
Pulmonary artery pressure >25mmHg at rest or >30mmHg with exercise
Cor pulmonale
Right ventricular hypertrophy due to disorders of any part of the respiratory apparatus (airways, parenchyma and blood vessels, chest wall, respiratory musculature, or central nervous system controller)
Right ventricular response to acute increase in pulmonary afterload
No time to hypertrophy, so the right ventricle is forced to work at higher volumes instead, effectively dilating.
Right ventricular response to chronic increase in pulmonary afterload
RVH
Pulmonary embolism in pulmonary HTN
Pulmonary emboli result in an acute increase in afterload on the RV and resulting pulmonary hypertension when they occlude half to two-thirds of the vessel
Disorders which result in thickening of pulmonary artery walls and subsequent pulmonary HTN due to vessel narrowing
- Idiopathic pulmonary hypertension
- Hereditary pulmonary arterial hypertension (BMPR2 mutations, result in hyperplasia of pulmonary artery smooth muscle)
- Scleroderma
- Certain drugs and toxins
Mechanisms of pulmonary hypertension (6)
- Occlusion of vessels by emboli
- Thickening of arterial walls
- Loss of blood vessels due to alveolar scarring or destruction
- Pulmonary vasoconstriction (hypoxia or acidosis)
- Increased pulmonary flow (left to right shunt, often results in 2 when chronic, leading to Eisenmenger syndrome)
- Elevated left atrial and pulmonary venous pressure
Leading factor contributing to pulmonary hypertension in COPD
Hypoxic vasoconstriction
Histologic changes in pulmonary hypertension
- Intima hyperplasia and media hypertrophy in small vessels
- Obliteration of the lumen of small vessels (chronic change)
- Thickening of walls in elastic arteries, resulting in decreased compliance
- Right ventricular hypertrophy
Plexiform lesions
Plexus of small, slit-like vascular channels resulting from proliferation and migration of cells originating in the vessel wall (smooth muscle cells, endothelial cells, and fibroblasts).
Pathognomonic feature of chronic pulmonary arterial hypertension, though pathophysiology is not fully understood
Pulmonary hypertension and thrombosis
While pulmonary hypertension may often be caused by thromboembolism, chronic pulmonary hypertension also induces endothelial damage which results in thrombosis within the pulmonary arteries themselves.
This most often occurs in the small arterioles.
If the primary component of the vascular change occurs at the precapillary level in the pulmonary arteries or arterioles, . . .
. . . pulmonary arterial pressures (both systolic and diastolic) rise, but the pressure within pulmonary capillaries remains normal.
If the primary component of the vascular change occurs at the capillary or pulmonary venous level, . . .
. . . pulmonary capillary pressure is elevated above its normal level.
Consequences of increased pressure within the pulmonary capillaries
- Fluid hydrostatic leakage into interstitium and alveoli (ie, cardiogenic pulmonary edema)
- Increased permeability of capillary membranes (ie, non-cardiogenic pulmonary edema)
Why does pulmonary edema occur in right ventricular hypertrophy secondary to left ventricular diastolic failure, but not in primary right ventricular hypertrophy?
Because capillary pressures are only increased in left ventricular diastolic failure. In primary right ventricular hypertrophy, pulmonary arterial pressure is likely increased, but capillaries can control their pressure by constricting their arteriolar sphincters and dropping pressure. But if venous pressures are high, capillary pressures must be equally high or higher by necessity.
Dyspnea and fatigue in pulmonary hypertension
They are observed in pulmonary hypertension even in the absence of any gas exchange problem. This is due to stretch receptors detecting the pressure, not to chemoreceptors.
Pulmonary hypertension “chest pressure”
Difficult if not impossible to distinguish from angina pectoris.
Also increases with exertion and is usually described as tightness. Presumed to be related to ischemia of the right ventricle due to the large metabolic demand of pumping frequently against a high afterload.
Strong exertion may result in transient right ventricle failure, lightheadedness, and syncopy. This is a very poor prognostic sign.
Cardiac exam in isolated pulmonary hypertension
- Accentuated P2
- Tricuspid regurgitation murmur
- Graham Steell murmur (murmur of pulmonary HTN)
- Pulmonary artery tap
- LLSB heave
- R sided S4 gallop (indicates RVH)
- R sided S3 gallop (indicates RV failure)
Pulmonary artery tap
When the pulmonary artery is enlarged, a pulsation may be felt at the left upper sternal border
Diagnosis of pulmonary hypertension
Requires cardiac catheterization and accurate hemodynamic measurements of pulmonary arterial and pulmonary venous pressures
What is going on in this radiograph?
Pulmonary arterial hypertension. The lesions are enlarged central pulmonary arteries. Notice that the smaller vessels taper off quickly after stemming off from them.
When there is elevation of pulmonary venous pressure from mitral stenosis or left ventricular failure, the chest radiograph often shows . . .
. . . redistribution of blood flow from lower to upper lung zones, accompanied by evidence of interstitial or alveolar edema
Total, alveolar, and extraalveolar PVR plot
PHTN profiles (numerically in terms of PVR, PAP, PVP)
Normal pulmonary arteriole and PAH arteriole H and E
PAH is on the right. This helps you picture why a vasodilator is going to do absolutely nothing to help.
What is shown in this pulmonary arteriole?
A plexiform lesion, pathognomonic of PAH.
Current therapies for PAH
Targeting cGMP in PAH
The two drugs in the upper right are viagra and cialis.
NOTE that nitrates and viagra/cialis together result in dangerously high levels of cGMP, leading to pulmonary and systemic hypotension. This is a classic contraindication that will be on the Boards.
