9. 1- Pulmonary arterial hypertension (PAH)
PAH is a rare disease
Aeitiology: idiopathic, heritable , associated forms
Pathophysiology:
Proliferative vasculopathy which is histologically
characterized by endothelial and smooth muscle cell
proliferation, medial hypertrophy, fibrosis and in-situ
thrombi of the small pulmonary arteries and
arterioles.
10. Pathobiologic basis of therapy
Imbalance between locally produced vasodilators and
vasoconstrictors, in addition to vascular wall
remodeling
Three major pathobiologic pathways (nitric oxide,
endothelin, and prostacyclin) play important roles
in the development and progression of PAH.
11. The endothelium-derived relaxing
factor Nitric Oxide (N.O)
Potent pulmonary vasodilator
Produced in high levels in the upper and lower airways
by nitric oxide synthase II (NOSII)
NO causes smooth muscle relaxation and maintaining
the normal pulmonary vascular tone
Patients with IPAH have low levels of NO in their
exhaled breath, and the severity of the disease
inversely correlates with NO reaction products in
bronchoalveolar lavage fluid.
12. Endothelin-1
A peptide produced by the vascular endothelium
Potent vasoconstrictive and proliferative paracrine
actions on the vascular smooth muscle cells
The pulmonary circulation plays an important role in
the production and clearance of endothelin-1, and this
physiologic balance is reflected in the circulating
levels of endothelin-1.
13. Prostacyclin
The endothelium also produces prostacyclin (PGI2) by
cyclooxygenase metabolism of arachidonic acid
Prostacyclin causes vasodilation throughout the
human circulation
Inhibitor of platelet aggregation by
14. Remodeling
Pulmonary vascular smooth muscle cells that normally have
a low rate of multiplication undergo proliferation and
hypertrophy leading to intimal narrowing and increased
resistance to blood flow
Loss of the antimitogenic endothelial substances (e.g.PGI2 and
NO)
Increased mitogenic substances (e.g.endothelin-1)
Other stimuli arise from locally activated platelets, which
release thromboxane A2 and serotonin
Act as growthpromoting substances on the vascular smooth
muscle cells, Both are vasoconstrictors
15. An abnormal proliferation of endothelial cells
occurs in the irreversible plexogenic lesion.
are glomeruloid structures forming channels in
branches of the pulmonary artery
may result from a deregulated growth of endothelial
cells
represent a unique form of active angiogenesis
Vascular endothelial cell factor (VEGF) promotes
endothelial cell proliferation
16. Thrombosis
Blood thrombin activity is increased, indicating
activation of intravascular coagulation,
whereas soluble thrombomodulin, a cell membrane
protein that acts as an important site of thrombin binding
and coagulation inactivation, is decreased.
In addition, PGI2 and NO, both inhibitors of platelet
aggregation, are decreased at the level of the injured
endothelial cell.
Circulating platelets in patients with PAH seem to be in a
continuous state of activation and contribute to the
prothrombotic milieu by aggregating at the level of the
injured endothelial cells
17. Signs and symptoms
Nonspecific
Dyspnea, weakness and recurrent syncope.
Other symptoms include fatigue, angina, and abdominal
distention
Symptoms at rest are reported only in very advanced cases
The physical signs include:
left parasternal lift, loud pulmonary component of the second
heart sound (P2), pansystolic murmur of tricuspid regurgitation,
diastolic murmur of pulmonary insufficiency, and right
ventricular S3. Jugular vein distention, hepatomegaly, peripheral
edema, ascites, central cyanosis and cool extremities may be seen
The lung examination is usually normal.
18. Investigations:
Electrocardiography
RAA, RAD, RVH,
ST depression and T-wave inversions in anterior leads
However, a normal ECG does not exclude diagnosis
Chest radiography
cardiomegaly or prominent central pulmonary arteries
19. chest CT scanning
Exclude interstitial lung disease and thromboembolic
disease.
main pulmonary artery diameter (MPAD) is > 29 mm
and/or the ratio of the main pulmonary artery to
ascending aorta diameter is >1
The most specific CT findings for the presence of PH were
both a MPAD > 29 mm and segmental artery-to-bronchus
ratio of >1:1 in three or four lobes
Rapid tapering or “pruning” of the distal pulmonary
vessels.
20. Echocardiography
Extremely useful for:
assessing right and left ventricular function
estimating pulmonary systolic arterial pressure, and
evaluating for congenital anomalies and valvular
disease
Systolic pulmonary artery pressure is estimated using
tricuspid insufficiency jet velocity based on the
simplified Bernoulli's equation
21. Right heart catheterization
FOR
right atrial pressure
mean PAP
pulmonary artery occlusion pressure (PAOP)
cardiac output (CO)
pulmonary vascular resistance (mPAP-PAOP)/CO
Transpulmonary gradient (mPAP-PAOP)
Evaluates pulmonary vasoreactivity
22. Treatment
There is no cure for pulmonary hypertension.
The goals of treatment are:
to treat the underlying cause
to reduce symptoms
improve quality of life
to slow the growth of the smooth muscle cells and the
development of blood clots
to increase the supply of blood and oxygen to the
heart, while reducing its workload
23. General measures
Oral anticoagulation improves survival
Supplemental oxygen should be used to maintain
oxygen saturation greater than 90%,especially because
hypoxemia is a major cause of pulmonary
vasoconstriction.
Diuretics are indicated for right ventricular volume
overload
Digoxin is reserved for patients with refractory right
ventricular failure and for rate control in atrial flutter
or fibrillation.
24. Pulmonary vascular reactivity
testing and vasodilator therapy
Only patients with an acute vasodilator response to an
intravenous or inhaled pulmonary vasodilator
challenge (eg, with adenosine, epoprostenol, nitric
oxide) derive any long-term benefit from CCBs.
Such patients constitute less than 15% of patients with
IPAH and probably less than 3% of patients with other
associated forms of PAH
Patients who do not have an acute vasodilator response
to a vasodilator challenge have a worse prognosis on
long-term oral vasodilator therapy
25. Calcium Channel Blocker therapy
(CCB)
These drugs are thought to act on the vascular smooth
muscle to dilate the pulmonary resistance vessels and
lower the pulmonary artery pressure.
The use of CCBs should be limited to patients without
overt evidence of right-sided heart failure as they may
worsen right ventricular failure
26. Specific vasodilator therapy
These drugs in general work by dilating the pulmonary
arteries and, therefore, by reducing the pressure in these
blood vessels and some help prevent the excessive
overgrowth of tissue in the blood vessels (that decrease
remodeling of the vessels).
Prostacyclins
dilates systemic and pulmonary arterial vascular beds.
Short acting drugs
include epoprostenol (Flolan), treprostinil (Remodulin),
iloprost (Ventavis), Treprostinil (Tyvaso).
27. Phosphodiesterase type 5
Inhibitors (PDE5i)
Sildenafil (Viagra)
is an orally active pulmonary vasodilators.
promote selective smooth muscle relaxation in lung
vasculature by inhibiting PDE5 thereby stabilizing
cyclic guanosine monophosphate (cGMP, the second
messenger of nitric oxide), allowing a more sustained
effect of endogenous nitric oxide,
an indirect but effective and practical way of using the
NO-cGMP pathway.
28. Endothelin Receptor Antagonists
(ERAs)
Bosentan
Sitaxentan, a selective endothelin (ET)-A receptor antagonist,
has negligible inhibition of the beneficial effects of ETB
stimulation, such as nitric oxide production and clearance of ET
from circulation.
In clinical trials, the efficacy of sitaxentan has been much the
same as bosentan with reduced hepatotoxicity.Dosing is once
daily
Ambrisentan :
A-selective endothelin receptor antagonist
once-daily dosing.
improvements in 6-minute walk distance in patients
low risk of aminotransferase abnormalities.
The most frequent side effect of ambrisentan isfluid retention
29. ACCP guidelines recommend using the patient’s New
York Heart Association (NYHA) functional class to
guide the choice of vasodilator therapy
• Functional class II – Sildenafil
• Functional class III - Endothelin-receptor
antagonists (bosentan), sildenafil, IV epoprostenol, or
inhaled iloprost
• Functional class IV - Intravenous epoprostenol.
30. Surgery
Atrial septostomy:
palliative procedure
in the setting of severe disease with recurrent syncope
or right heart failure (or both) despite maximal
medical therapy.
The procedure can also be used as a bridge to lung
transplantation.
Lung transplantation
31. Pulmonary Hypertension in
Chronic Lung Diseases and/
or Hypoxia
Pulmonary hypertension is a common complication in
lung disease.
In the most recent revised classification of pulmonary
hypertension (PH), chronic lung diseases or conditions
with alveolar hypoxia are included in WHO Group III
of PH-related diseases
As both the primary respiratory condition and PH may
be associated with dyspnoea, the latter often goes
unrecognised
32. Pulmonary hypertension due to
lung diseases and/or hypoxia
Chronic obstructive pulmonary disease
Interstitial lung disease
Other pulmonary diseases with mixed restrictive and
obstructive pattern
Sleep-disordered breathing
Alveolar hypoventilation disorders
Chronic exposure to high altitude
Developmental abnormalities
33. Pathophysiology
Alveolar hypoxia is a potent stimulus for pulmonary
vasoconstriction.
It operates at the endothelial level and is one of the
most important pathways leading to PH development
in chronic lung diseases.
Alveolar hypoventilation precipitates acute
pulmonary vasoconstriction in some regions of the
lungs, and vasodilation in others, causing
physiological shunt.
34. Studies of the vasculature in hypoxic PH have
demonstrated changes including intimal thickening,
medial hypertrophy and muscularization of the small
arterioles
chronic hypoxia triggers endothelial cell proliferation
Inflammatory cells have been detected in local vascular
structures in COPD patients, in addition to the evidence of
systemic inflammation with raised inflammatory markers,
such as CRP and TNF–α
35. The impact of PH on mortality in COPD is
independent of age, lung function and blood gas
derangements
In patients with parenchymal lung disease PH is
generally modest (mean PAP 25-35 mmHg).
it increases significantly during exercise, sleep and
acute infective exacerbations
36. Treatment of PH in COPD
No clear guidelines and no medications currently
registered for the treatment of PH secondary to
COPD.
The primary focus of treatment, therefore involves
standard therapy with smoking cessation,
bronchodilators, inhaled steroids, long-term oxygen
therapy (LTOT) and pulmonary rehabilitation
37. Long-term home oxygen therapy
((LTOT
The only therapy that has demonstrated a survival
advantage in people with COPD and coexistentPH is
LTOT.
Indications for LTOT include patients with severe
hypoxemia or those with moderate hypoxemia and cor
pulmonale
physically reliant on a machine, expensive
38. Prostanoids/ Endothelin receptor
antagonists (ERA)/ Phosphodiesterase-
5 (PDE-5) inhibitors
current practice does not favour routine use of these
medications.
The primary concern in using pulmonary vasodilators is
related to worsening gas exchange due to ventilation/
perfusion (V/Q) inequality
39. Calcium channel blockers
Their use is largely limited to patients who
demonstrate acute vasoreactivity testing
Use the dihydropyridine group
An important practice point is that alternative causes
of PH in patients with COPD, such as concomitant
sleep disordered breathing or chronic
thromboembolic disease should be actively
investigated, as there are important treatment
alternatives in these patients.
40. Sleep disordered breathing and PH
True prevalence of PH in OSA is unknown and ranges
from 17 - 52%
Three main mechanisms have been proposed
including hypoxia, mechanical factors and reflex
mechanisms
with CPAP : decrease in the mean PAP observed
and associated with improved pulmonary endothelial
function due to the elimination of intermittent
hypoxemia
41. PH in interstitial lung diseases
The prevalence of PH in IPF is high and varies between 32 -
85%.
PH is mostly of moderate severity
Adenosine has been associated with progression of
fibrotic lung disease and PH through the adenosine
receptor
The prevalence of PH in systemic sclerosis is as high as
45%
The development of PH in ILD is associated with high
mortality
However, most guidelines do not recommend use of
PAH-specific treatments in patients with ILD
42. High altitude PH
prevalence is between 5 and 18% in those living at
≥3000 metres
Migration to a lower altitude reverses HAPH. However,
as an alternative, sildenafil maybe used
