peripheral pulmonary stenosis

1. By
Dr. Varun K.

2.  Isolated peripheral pulmonary artery stenosis was described
first by Maugars and later by Schwalbe
 Stenosis of the pulmonary arteries, isolated or in association
with other cardiac defects, occurs in 2% to 3% of all patients
with congenital heart disease.
 The stenosis may be single,
 involving the main pulmonary artery or either of its
branches,
 or multiple, involving both the main and several smaller
peripheral pulmonary artery branches

3.  Other associated cardiac defects, most commonly valvar PS
and VSD, are present in about 2/3rd of the cases.
 Hypoplasia of the pulmonary arteries also is seen frequently
with TOF

4.  In congenital rubella syndrome, peripheral pulmonary
artery stenosis typically is associated with PDA and
ASD.
 In Williams syndrome, multiple peripheral pulmonary
artery stenosis, supravalvar AS, mental retardation,
and peculiar facies
 associated with Noonan syndrome, Alagille syndrome,
cutis laxa, Ehler Danlos syndrome, and Silver Russell
syndrome.

6.  Pulmonary artery stenosis (PAS) is the second most common CV
abnormality in WS
 The incidence of PAS in WS depends on the age at the time of
presentation
 More common in patients in the first year of life than at older
ages
 The reported range of incidence of PAS in WS is 37- 75%, with the
majority of studies reporting an incidence of ≈40%
 The stenoses seen in the pulmonary arterial bed most commonly
occur in the branch and peripheral PA

7. Embryology and Pathology
 The proximal portion of the MPA - bulbus cordis.
 The remainder of the trunk of the MPA - common
truncus arteriosus.
 The proximal segments of the RPA and LPA - 6th
branchial arches on either side.

8.  The distal portion of the left 6th arch persists as the
ductus arteriosus and later as the ligamentum
arteriosus.
 The peripheral portions of the PA branches derive
from the postbranchial pulmonary vascular
plexus, which lies in close relationship to the growing
lung buds.

9.  The rubella virus, appears to exert its teratogenic effect by
interfering with the normal formation of the elastic tissues.
 Williams syndrome - A genetic deletion mapped to chr. 7
resulting in abnormal elastin production
 Alagille syndrome - Mutations in either JAG1 or NOTCH2 have
mapped to the chr.20. JAG1, which encodes a ligand critical to the
notch gene–signaling cascade that is important in fetal
development
 Noonan's syndrome - associated with mutations in genes on
chr.12 that are part of the RAS/RAF/MEK/ERK signal transduction
pathway, an important regulator of cell growth. Approximately
50% of patients have gene mutations in PTPN11
 Sporadic or can be familial with AD inheritance.

10. Classification
 A useful classification was proposed by Gay et al. They
classified the stenoses into four types:
1. stenoses involving the main pulmonary trunk or the right
and left branches,
2. stenoses involving the bifurcation of the pulmonary artery
extending into both branches,
3. multiple peripheral stenoses,
4. a combination of main and peripheral stenoses

12. Physiology
 Elevated RV and PA (proximal to stenosis) systolic pressure
that depends on the severity and distribution of the stenoses
 When the obstruction is severe, RV ejection is prolonged and
the PA trunk proximal to the obstruction behaves as an
extension of the RVOT.
 The pressure tracing proximal to the stenosis resembles that
of the RV, with high systolic and low diastolic pressure

13.  When the stenosis is U/L and there is no left-to-right shunt,
resting RV pressure remains normal
 Because flow to the stenotic side is lower than normal, the
systolic pressure difference tends to underestimate the
severity of obstruction; however, the diastolic pressure
difference between the main pulmonary artery and the
stenotic branch is proportional to the severity of obstruction.

14. Clinical features
 Pts. with mild or moderate bilateral PA stenosis, as well as
those with unilateral stenosis, are usually asymptomatic
 DOE, easy fatigability, and signs of right heart failure
may occur in patients with severe obstruction.
 Children and adults occasionally experience chest pain
 Haemoptysis
 Sudden death

15.  S1 is usually normal, and there is no ejection click.
 S2 is usually normally split and P2 is of normal intensity
 Systolic crescendo-decrescendo murmur with delayed onset
in the pulmonary area that is well transmitted to the axilla and
back.
 A continuous murmur occasionally may be present, indicating
that the diastolic gradient across the obstruction is significant.
 The presence of soft, blowing systolic or continuous murmurs
typically heard over both lung fields and in the back should point to
the correct diagnosis.

16. Ecg
 The ECG is normal in patients with mild stenosis and
demonstrates RVH in those with moderate to severe
obstruction.
 A relatively high frequency of LAD has been noted in infants
with the rubella syndrome, as well as in infants with Noonan
syndrome.

17. Radiologic features
 Only in cases of severe unilateral stenosis and increased
pulmonary blood flow is there a detectable difference in the
degree of vascularity between the two lung fields.
 When the stenosis is bilateral and severe, RA and RV enlargement
may be seen.
 MRI is becoming increasingly useful in detailing PA anatomy. It is
superior to echocardiography and complementary to angiography
for the detection of pulmonary artery abnormalities.
 Radionuclide lung perfusion scans are very useful in quantifying
flow to each lung before and after surgical or transcatheter
therapy

19. Echocardiographic features
 The anatomy of the proximal PA usually can be delineated
fairly well, but the distal PA cannot be imaged reliably. The
PSAX view and suprasternal views are the most helpful.
 Color flow Doppler can contribute to the qualitative
assessment of stenosis by the appearance of turbulence at the
area of obstruction. The pressure gradient can be estimated
by Doppler but not always accurately.
 The echocardiogram is useful in detecting secondary
manifestations of RV hypertension, such as RVH, TR, or
enlargement of the right-sided chambers.

21. Cardiac catheterization
 The clinical suspicion of peripheral pulmonary stenosis
usually requires cardiac catheterization to confirm the
diagnosis as well as to determine the severity and exact
anatomy.
 Carefully obtained withdrawal pressure tracings from the
distal branches will demonstrate pressure gradients across
the stenotic segments.
 Systolic pressure gradients >10 mm Hg should be considered
abnormal in the absence of increased pulmonary blood flow

22.  When the stenosis is unilateral, a pressure gradient is present
at the site of obstruction, but the proximal PA pressure is
normal. The measured gradient may underestimate the
severity of angiographic obstruction as a result of preferential
flow to the unobstructed side
 With bilateral PA stenosis, the systolic portion of the tracing
is identical to that of the RV. The dicrotic notch is usually
quite low with a slow descent, followed by low diastolic
pressure similar to that distal to the obstruction.

24. Angiography
 Angiocardiography is the best tool in the diagnosis of
peripheral PA stenosis.
 The exact location, extent, and distribution of the lesions
can be easily visualized with selective injections proximal to
the site of obstruction.
 The anterior view with cranial angulation and straight lateral
views usually show the anatomy of the RPA and of the
peripheral branches bilaterally. The proximal LPA can be well
visualized in the hemiaxial oblique views

27. Non invasive imaging : MRI and CT
 Gadolinium-enhanced three-dimensional magnetic
resonance angiography (MRA) has been shown to correlate
with angiographic findings with 100% sensitivity and specificity
when assessing PA stenosis or hypoplasia, absent or discontinuous
PA.
 Measurements of PA diameter also showed excellent correlation,
with a mean difference of 0.5 mm ± 1.5 mm between the two
modalities.
 A limitation of MRA for pediatric patients is motion artifact
requiring breath holding for optimal image acquisition.
 Anatomic delineation of the more peripheral branches, typically
beyond the 3rd and 4th generation is not adequately achieved by
MRA.

28.  Advantages include reduced risk, avoidance of radiation, and
preservation of vascular access for future interventional procedures.
 Electron-beam computed tomography (CT) has also shown excellent
correlation with angiography . It is less sensitive to motion artifact and
can often be performed with sedation alone, even in small infants.
 CT is more suited for the unstable patient because of the short time
needed to acquire the information and has better spatial resolution than
MRA.
 Radiation exposure and contrast administration are necessary, but the
dose of both is typically lower than needed for angiography to obtain the
same information.
 Exact hemodynamic measurements still require cardiac catheterization.

29. Treatment
 Mild to moderate isolated unilateral or bilateral peripheral
pulmonary artery stenosis usually does not require treatment
 Despite significant improvements in surgical techniques,
access to distal vessels remains difficult, and catheter
treatment is sometimes the only option.

30. Balloon angioplasty
 The first use of PTA for peripheral pulmonary arterial
stenosis was described by Martin et al. in 1980
 investigators demonstrated histologically that successful
dilations resulted from intimal and medial tearing of the
pulmonary artery wall

31.  The protocol for angioplasty consists of positioning a balloon
dilation catheter across the stenotic segment of the
pulmonary artery.
 The balloon diameter should be 3-4 times the narrowest PA
segment.
 Initially, the balloon is inflated to low pressure (1 to 2 atm)
while confirming proper position, indicated by a waist
representing the stenotic segment centered on the balloon.

32.  Under continuous fluoroscopic monitoring, the balloon is
inflated further to higher pressure for a variable period (10 to
60 seconds) until the waist disappears or the maximum
pressure is reached.
 A postdilation angiogram should be performed either just
proximal to the dilated area or by advancing an end-hole
angiographic catheter over a guidewire left in place across the
dilated segment

34.  Percutaneous balloon angioplasty of peripheral pulmonary artery
stenosis has met with a significantly lower success rate than
pulmonary valvuloplasty.
 The criteria used to determine success has been described
arbitrarily as an increase of >50% in vessel diameter,
an increase of >20% in flow to the affected lung,
or a decrease of >20% in systolic RV to aortic pressure ratio.
 The overall acute success rate for patients with varying diagnoses,
most commonly TOF with and without pulmonary atresia, has
been reported as 50-60% and appears to be similar in the small
subset of patients with isolated peripheral pulmonary artery
stenosis and intact ventricular septum.

35.  Hosking et al. examined the clinical impact of balloon
angioplasty using relatively low pressure balloons on
subsequent management and found that only 35% of patients
were favorably influenced by the procedure, with no patient
previously considered inoperable becoming operable
following angioplasty.
 A similar study by Zeevi et al. found a 50% rate of favorable
clinical impact using more stringent criteria for technical
success and high-pressure balloons on some patients.
 The rate of recurrent stenosis has been 15-20% in short-term
to midterm follow-up; long-term follow-up is unknown.

36.  Because of the disappointing results obtained with low-pressure
balloons, high-pressure balloons that can be inflated 20 to 25 atm
are being used increasingly to dilate PA.
 The overall acute success rate is around 70-80%, but still only 50%
in patients with isolated peripheral pulmonary artery stenosis.
 Limited information is available regarding the frequency of
restenosis, but it may be higher than had been previously
suspected.
 Using high-pressure balloons whenever necessary, and defining
restenosis as >50% decrease in the gain in diameter achieved
at the initial successful angioplasty, a restenosis rate of 35%
was found at follow-up angiography in a group of 48 patients by
Bush et al

37.  The continued effort to improve on the success rate of balloon
angioplasty for resistant pulmonary artery stenosis has recently brought
about the use of cutting balloons in this setting.
 These balloons have 3-4 microsurgical blades with a cutting depth of
0.15 mm mounted longitudinally at 90-degree angles to the balloon.
 The technique is best suited for small, lobar pulmonary artery branches
not amenable to stenting.
 Vessels resistant to high-pressure balloon angioplasty have been shown
to respond to either cutting balloon angioplasty alone, or cutting
balloon angioplasty followed by high-pressure ballooning.
 The longitudinal cuts made by the blades create sites for the tear to
propagate when further dilated with a high-pressure balloon. Successful
dilation has been achieved in 92% of resistant vessels in a study by
Bergersen et al

38.  Significant complications have been reported in 5-15% of patients
following percutaneous balloon dilation of peripheral pulmonary
arterial stenosis.
 These complications include
o exsanguination from a ruptured PA either by the dilating balloon
or the guidewire
o hemoptysis
o ipsilateral pulmonary edema
o obstruction of dilated vessels by intimal flaps
o pulmonary artery aneurysms
o clotted iliac veins
o Transient arrhythmias, cyanosis, and hypotension also may occur
during pulmonary artery angioplasty

40.  Transcatheter intervention is most commonly used for peripheral PAS
 Geggel et al have reported that central PA do not respond well to
balloon angioplasty. However, the intrapulmonary segments of the PA
respond better to balloon dilation, especially when undertaken in a
serial manner.
 Wessel et al previously reported that high degrees of PAS are tolerated
well without intervention, which, when combined with the high
frequency of complications from transcatheter interventions ( PA
aneurysm) led Geggel et al to recommend frequent noninvasive
observation in the asymptomatic patient with subsystemic RV pressures.
 Rapid failure of arterial stenting in patients with WS has been reported
 In-stent stenosis in patients with WS is likely related to an abnormal
arterial response to injury caused by stent implantation in the setting of
decreased arterial elastin.

41.  The mortality rate, measured at 7.7% in one series by Geggel et al, is
more than twice that reported in other settings.
 Interestingly, the cause of death was not associated with PA trauma in
any of the patients in this study, but rather, occurred in patients with
significant coronary artery stenosis or ventricular hypertrophy and
concomitant subendocardial ischemia with transient hemodynamic
perturbations.
 These findings, coupled with the recognition that spontaneous
improvement is often seen in patients with Williams syndrome and
pulmonary artery stenosis, have led most investigators to recommend
watchful waiting, particularly in young, asymptomatic children, despite
significant elevation of the right ventricular pressure.
 When necessary, a combined approach with distal balloon angioplasty
and proximal surgical reconstruction may be the best therapy in this
difficult group of patients

42. Balloon-expandable intravascular stents
 The stainless steel balloon-expandable stent developed by
Palmaz et al. dramatically improved the effectiveness of
balloon angioplasty in a selected group of patients
 Several investigators reported excellent results acutely as well
as in midterm follow-up of stent implantation for pulmonary
artery stenosis, with an increase of >100% in stenosis
diameter and a >75% reduction in gradient. Most of the
patients in these studies had associated congenital heart
disease, such as TOF with and without pulmonary atresia
and TA, and a smaller number had isolated congenital
pulmonary artery stenosis

43.  Shaffer et al reported on a group of 15 patients with isolated
PAS. There was a dramatic immediate decrease in the
gradient across the stenotic areas but a less significant
decrease in RV pressure than seen in the rest of the group, as
well as an increase in the RV pressure at midterm follow-up
not seen in the other patients.

45.  Complications from stent implantation include
o incorrect stent positioning or embolization, sometimes
requiring surgical removal
o thrombosis of the pulmonary artery within the stent
o all the complications associated with balloon angioplasty
alone, including pulmonary edema and pulmonary
hemorrhage

46.  At follow-up catheterization, a small and usually
hemodynamically insignificant decrease in diameter of the
stented vessel has been noted that resulted from neointimal
proliferation.
 McMahon et al noted an increase in luminal diameter from 5.4
mm to 11.2 mm immediately after stent placement and a decrease
to 9.3 mm after 5.6 years of mean follow-up.
 More significant narrowings can develop in areas of diameter
mismatch between the stented and nonstented vessel, or in
between nonoverlapping serial stents.
 In most cases the gradient measured on follow-up was due to
growth of the vessel wall adjacent to the stent despite the absence
of significant restenosis within the stent

47.  In very small patients, stents should be avoided unless the
stent used has the capacity to later be enlarged to adult
diameter. For older children and adult patients, in whom
stents can be dilated at the initial or subsequent
catheterizations to the required adult size of the vessel, stent
placement has become the preferred therapy for refractory
branch pulmonary stenosis

48. Surgery
 Multiple peripheral stenoses were first tackled by McGoon
et al. using an azygous vein graft to patch over the incised
stenotic segments
 Further surgical experience with PA reconstruction was
gained primarily in patients with TOF with pulmonary
atresia and aortopulmonary collateral arteries.
 When native arterioplasty is not sufficient, stenotic segments
are enlarged, preferably with autologous pericardium and
occasionally with azygous vein grafts

49.  Isolated congenital peripheral PA stenosis, often
accompanied by long-segment hypoplasia, is difficult to treat
successfully with either balloon angioplasty or surgery.
 Various techniques are used to deal with this lesion,
including excision of stenotic segments, and use of an
autologous pericardial roll to restore arterial continuity when
direct anastomosis is not possible
 A combined approach, with surgical reconstruction followed
by transcatheter pulmonary artery intervention, is often the
best form of treatment.

52. Course and prognosis
 Routine prophylaxis against endocarditis in acyanotic
patients with untreated peripheral pulmonary stenosis is not
recommended.
 Endocarditis prophylaxis is recommended for patients who
have received prosthetic material to treat pulmonary artery
stenosis, whether placed by surgery or by catheter
intervention, during the first six months after the procedure

53.  Most patients with mild or moderate stenosis remain stable,
and pressure gradients recorded early in life often decrease
with growth. This is particularly true in patients with
associated syndromes, such as Williams, Noonan, or
congenital rubella
 However, multiple peripheral pulmonary stenosis of severe
degree may be progressive, and the prognosis is poor unless
angioplasty, stent placement, or surgery is successful

54.  Complications include
o right ventricular failure
o pulmonary artery thrombosis
o poststenotic aneurysmal dilation with pulmonary artery
hemorrhage

55.  Isolated peripheral pulmonary artery stenosis is rarely seen
in adult patients and often is misdiagnosed as chronic
pulmonary thromboembolic disease. These patients typically
present with exertional dyspnea and fatigue, and
symptomatic improvement has been seen following balloon
angioplasty.
 Systemic vasculitis with pulmonary arterial involvement
should be excluded.
 The presence of murmurs consistent with pulmonary artery
stenosis in many of these patients in childhood or
adolescence suggests a congenital cause with slow
progression.

56.  Thank you…