Bod: Respiratory: Pulmonary Hypertension

Front 1

What is the major factor responsible for pulmonary hypertension?

Back 1

Increased pulmonary vascular resistance. (Duh)

Front 2

Explain the "hyperkinetic" etiology of PHTN.

What are the "hyperkinetic" etiologies of pulmonary hypertension?

Back 2

When blood flow through an atrial septal defect is so high that the pulmonary vascular bed cannot accomodate it (Left to right shunt). This leads to eventual secondary changes.

Intracardiac shunt lesions
Atrial septal defects, ventricular septal defects, anomalous venous return
Pulmonary arteriovenous fistulas

Front 3

Explain the "passive" etiology of PHTN.

What are the "passive" etiologies of pulmonary hypertension?

Back 3

When blood return to the left heart is impeded so that pressure increases ("back-pressure").

Coronary heart disease, cardiomyopathy, constrictive pericarditis
Mitral valve stenosis or obstruction
Left atrial obstruction
Myxoma, neoplasm, thrombus
Pulmonary venous obstruction
Neoplasm, adenopathy, fibrosing mediastinits

Front 4

Explain the "obliterative" etiology of PHTN.

What are the "obliterative" etiologies of pulmonary hypertension?

Back 4

When disease causes damage to pulmonary capillary beds --> reduced cross-sectional area --> increased pulmonary pressure.

Main cause: Interstitial lung disease

Obstructive (bronchitis, emphysema, bronchiectasis)
Restrictive physiology (fibrosis, thoracic cage abnormalities)
Pulmonary arteritis
Scleroderma, SLE, vasculitis, (Schistosomiasis)

Front 5

Explain the "obstructive" etiology of PHTN.

What are the "obstructive" etiologies of pulmonary hypertension?

Back 5

Caused by something obstructing the pulmonary vessels and causing a rise in pulmonary pressure.

Pulmonary embolism

Venous thromboemboli, tumor emboli
Pulmonary arterial thrombosis
Sickle cell disease
Schistosomiasis (common in the developing world)

Front 6

What are the "idiopathic" etiologies of pulmonary hypertension?

Back 6

Primary pulmonary hypertension (now known as IPAH, idiopathic pulmonary arterial hypertension).
Pulmonary veno-occlusive disease
Dietary-related pulmonary hypertension (e.g. aminorex, toxic oil syndrome)
Coexistent portal and pulmonary hypertension
HIV-associated PHTN.

Front 7

What is the mean pulmonary arterial pressure at rest and during exercise?

Back 7

25 at rest and 30 mm Hg during exercise

Front 8

Give a general description of the blood flow/nature of the flow through the lungs.

Back 8

"Normally, a large volume of blood flows through the pulmonary circuit under low pressure."

Front 9

How can the lungs handle increased blood flow through the lungs during exercise without a dramatic increase in pulmonary pressure?

Back 9

This is because of an increase of the cross sectional area of the vascular bed. This is due to blood flowing through vessels that are not normally perfused at rest.

Front 10

What is the mechanism of the development of pulmonary hypertension with mitral stenosis or left ventricular failure?

Back 10

Blood backs up on the left side of the heart (passive hypertension).

Front 11

What is the mechanism of the development of pulmonary hypertension with atrial or ventricular septal defect?

Back 11

Cardiac output is so high that even a normal vascular bed is unable to accommodate the high flow rate (hyperkinetic).

Front 12

What would cause vasoconstriction of a pulmonary capillary?

Back 12

Hypoxia

Front 13

Describe the nature of primary thrombi formed in the pulmonary circulation

Back 13

They are incorporated into the arterial wall and display eccentric and irregular intimal fibrosis.

Front 14

What is seen in 20% of cases of embolic (occlusive) pulmonary hypertension?

Back 14

Prominent medial hypertrophy. This suggests that vasoconstriction plays a role in the minority of these cases

Front 15

What neoplasms are prone to creating tumor emboli?

Back 15

Carcinomas of the stomach, liver, and breast.

Front 16

What are some common foreign body emboli?

Back 16

Cotton, wool, or gauze fibers used during injection or cardiac catheterization.

Talcum/starch used by heroin addicts

Front 17

What etiology of pulmonary hypertension do you think about when you see severe medial hypertrophy with concentric or circumferential intimal fibrosis?

Are these findings diffuse or focal?

Back 17

Obliterative (fibrotic) hypertension due to interstitial lung disease.

Focal - normal areas are normal

Front 18

Is severe pulmonary hypertension common in most forms of lung fibrosis (pneumocionioses, tuberculosis, sarcoidosis, viral infections)?

Back 18

No, it is not common

Front 19

What is the most characteristic finding of primary pulmonary hypertension?

Back 19

Plexogenic Pulmonary Arteriopathy (PPA). Capillaries grow giving the impression of a plexus arising from the arterial wall. (Can also be seen in congenital heart disease with left to right shunting)

Front 20

(extra credit)

What is a diet suppressant (now unavailable) that causes pulmonary hypertension?

Back 20

PHEN-PHEN

Front 21

What is the equation for the pressure in the pulmonary vessels?

Back 21

Pressure = CO * resistance

Front 22

What is Poiseuille's Law and what does it demonstrate?

Back 22

How sensitive resistance is to radius

Resistance = 8(viscosity)(length) / π(radius)^4

Front 23

What are three processes that can decrease the cross-sectional area of the vasculature of the lungs (causing PHTN)?

Back 23

- Vasoconstriction
- Blood vessel occlusion
- Blood vessel obliteration

Front 24

What are the ranges of pulmonary artery pressure that define PHTN?

Back 24

> 25 mm Hg at rest
> 30 mm Hg during exercise

Front 25

Cause of hypoxemia with PHTN?

Back 25

PHTN --> perfusion of areas that are not normally perfused (and therefore underventolated.

Can also lead to R to L shunting of blood through patent foramen ovales

Front 26

PHTN: patients complain of what?

Back 26

- Poor exercise tolerance.
- Severe dyspnea on exertion.
- Sometimes a dull substernal chest pain. (Note that sharp, pleuritic chest pain indicates PE)
- Syncope
- Loud P2, narrowly split S2
- RVF signs (RV heave, JVD)

CXR:
- May show enlarged hilar shadows due to distended pulmonary arteries or RV enlargement.

PFTs:
- May show a reduced diffusing capacity

Front 27

What is the basis of the self-perpetuating cycle of PHTN?

Back 27

Reduced vascular bed --> hypoxemia --> increased pulmonary vasoconstriction --> increased pressure --> secondary changes in pulmonary vessels --> increase in pressure/hypoxemia --> --> -->

Front 28

When PHTN is detectable at rest...

Back 28

...irreversible secondary changes to the lung have already taken place.

Front 29

Explain the "vasoconstrictive" etiology of PHTN.

Back 29

Hypoxia and acidemia cause pulmonary vasoconstriction

- Hypoxia with COPD
- Hypoxia with restrictive disease

Front 30

What is one of the most potent vasodilators known?

Back 30

Oxygen!

Front 31

IPAH: demographics?

Back 31

Women in their 40s, sometimes with collagen-vasculature disease.

Front 32

IPAH: prognosis?

Back 32

Death within months to years

Front 33

IPAH/PHTN: treatment?

Back 33

- Vasodilators
- Drugs that minimize proliferation of smooth muscle (IV prostacyclin, IV or SC treprostenil, inhaled iloprost)
- Endothelin receptor antagonists (PO bosentan)
- Phosphodiesterase type 5 inhbitors (PO sildenafil)
- Calcium channel antagonists (nifedipine, diltiazem) - only benefit a small fraction of patients.