L33: Pulmonary Hypertension (Swift) Flashcards
PAP forumla
PAP = (PBF x PVR) + PCWP
PCWP = P in the left atrium
Main differences between systemic and pulmonary circulation**
Pulmonary system has:
- lower resistance
- lower pressure
- higher capacitance
- increased CO2 leads to vasoDILATION
- decreased O2 leads to vasoCONSTRICTION
Natural vasoconstrictors in the lungs (4)
Endothelin-1
Angiotensin II (increased in CHF)
Thromboxane
Serotonin
Natural vasodilators in the lungs (3)
Nitric oxide (NO) - a therapy for pulm. HT
Prostacyclin (PGI2)
Oxygen (causes vasodilation in the lungs)
How is vasodilatin/vasoconstriction regulated at the local level in the lungs?
Nitric oxide, PGI2, and ET-1 are sourced from the endothelial cells lining blood vessels in the lungs. Whichever is in excess (ET-1 vs. NO and PGI2) determines whether there is vasoconstriction or dilation
Pulmonary endothelial dysfunction occurs when:
- increased ET-1 or decreased NO and pGI2 –> vasoconstriction
- a high blood pressure damages endothelium and causes even more vasoconstriction and higher BP
Why does pulmonary HT cause vascular remodeling?
- ET-1 and AT-11 are chronically increased –> intimal and smooth muscle hypertrophy
- is eventually irreversible
- vasoconstriction dominates
Poiseuille’s Law
- radius will increase or decrease flow by a factor of 4
- if radius decreases, have to increase pressure to maintain flow –> hypertension
Microvascular thrombosis can be either a cause or effect of PHT
:)
PHT can result from increased:
Pulmonary vascular resistance (PVR)
Pulmonary blood flow (PBF)
Pulmonary capillary wedge pressure (PCWP) (increased LA pressure)
Causes of increased PVR
1) primary PHT (rare)
2) HWD (most common): causes arteritis, embolism –> edema and congestive heart failure
3) Chronic pulmonary disease (asthma, chronic bronchitis, hypoxic vasoconstriction)
4) PTE
5) high altitude (global hypoxia)
6) hypoventilation (from anesthesia, obesity, nueromuscular dz)
Causes of increased PBF
- congenital shunts (most common)
- increased CO (from anemia, hyperthyroidism)
Eisenmenger’s physiology
A large volume L to R shunt can increase PBF so much that it causes permanent vascular change and severe PHT, ultimately causing a shunt REVERSAL as pressure in pulmonary tree exceeds pressure in the heart
-results in pulmonary vascular resistance
Causes of increased PCWP (post-capillary hypertension)**
- increased LA and pulmonary venous pressure (L-sided CHF)
- diastolic PAP within 5 mm of PCWP
Mitral valve disease or DCM –> L-sided CHF –> Increased LA pressure or pulmonary venous pressure –> increased PCWP –> increased vascular resistance
Consequences of PHT
- decreased CO
- hypoxemia
- cor pulmonale (R side of heart hypertrophies due to pressure overload –> myocardial failure –> RV dilation –> RHF)
CS of PHT
- RHF (ascites, wt. loss, poor appetite)
- cyanosis
- syncope
- cough, dyspnea
Differentials for ascites
- dec. oncotic pressure
- inc. hydrostatic pressure
- dec. lymphatic drainage
- septic exudate
- neoplastic effusion
- chyle
Ddx for dyspnea/cyanosis
Cardiac dz: CHF, HWD
Resp. Dz: infection, inflammation, neoplasia, pleural effusion
Signs of PHT on ECG
Deep S waves
Right axis deviation
Diagnostic evaluation of PHT patient
CBC (look for infection, allergic/parasitic) Chem (albumin) UA: proteinuria Fluid analysis Heartworm test SpO2/PaO2 to evaluate V/Q mismatch Thoracic rads
Things to look for on thoracic rads of PHT patient
- pleural fluid/pulmonary edema
- cardiac or vascular enlargement: L or R side?
- tortuous blunted pulm. aa
- airway or parenchymal dz (distribution helps determine CHF vs. bronchopneumonia)
Dx of PHT
Measure PAP:
- direct method (gold standard) involves cardiac catheterization and anesthesia
- indirect method: perform echo and estimate based on RV hypertrophy, MPA dilation, and pulmonic/tricuspid regurgitation
PI/TR**
Pulmonic/tricuspid regurgitation
- tricuspid regurge is an indication of SYSTOLIC pressure
- pulmonic regurge is an indication of DIASTOLIC pressure
PI/TR is an estimate of PAP
Normal pulmonary artery pressure (PAP)
Diseases assoc. with pulmonary artery hypertension
Idiopathic and familial PH HWD Congenital shunts Collagen vascular dz Eisenmenger's syndrome
Diseases assoc. with PH with L-sided heart disease
Myxomatous mitral valve disease Myocardial disease (ie. DCM)
Diseases assoc. with PH associated with lung disease/hypoxemia
COPD
Interstitial lung disease
High altitude
Alveolar ventilation disorders
Diseases assoc. with PH caused by thromboembolic disease
Thrombotic obstruction of PAs
Non-thrombotic obstruction (ie. Parasites, neoplasia)
Misc. diseases causing PHT
Compression of pulmonary vessels
Lymphadenopathy
Granulomatous disease
PHT causes a pressure overload of the RV in cor pulmonale
:)
Changes in pressures assoc. with L-sided CHF
- PAP may be increased due to high PCWP with normal PVR
- increased LA and pulmonary venous pressure with severe mitral regurge, cardiomyopathies, or mitral stenosis
- chronically increased PCWP may lead to increases in PVR and disproportionate increases in PAP
When will pressure in pulmonary arterial tree not equal pressure in the RV?
When there is pulmonic stenosis
Normal pressure gradient
(Pressure gradient b/w RA and RV)
25 mmHg
PG + pressure in RA = ** (normally)
PAP or Pressure in RV
Tx of PHT
- tx underlying cause if possible, except or R to L shunts
- tx hypoxia and R-CHF with oxygen, diuretics, and ACE-inhibitors
Methods of decreasing PVR (txs)
- oxygen (acute tx only)
- NO (acute tx only)
- Ca channel blockers (can have systemic side effects)
- ACE inhibitors (little effect on PAP)
- synthetic prostacyclin (extremely expensive)
- ET-1 receptor antagonists (Bosentan)
- phosphodiesterase inhibitors
- anti-thrombotics (only use if think PTE is cause of PHT)
*few actually succeed!
Phosphodiesterase inhibitors
Sildenafil: causes modest decrease in PAP and may improve CS
-beware in L-CHF: may increase LV preload and precipitate pulmonary edema
Tadalafil (Viagra): longer-acting
Pimobendan
-a positive inotrope that causes systemic and pulmonary vasodilation
Tx of choice for alveolar hypoxia
Oxygen
Side effect of high dose Ca channel blockers
Systemic hypotension
