Tuesday, November 16, 2010

Pulmonary arterial anomalies



Classification:
  • Pulmonary arterial sling.
  • Origin of one pulmonary artery from the ascending aorta.
  • Pulmonary atresia with ventricular septal defect.
  • Persistent truncus arteriosus (PTA).
  • Pulmonary Arterio-Venous Fistula (AVF).




Pulmonary arterial sling


Definition:


Pulmonary arterial sling is defined as: Origin of the left pulmonary artery from the right pulmonary artery.


Anatomy:


The pulmonary trunk divides in front of the left main bronchus, to the left of the mid line, into the right & left PA.


The left PA is short and arches over the left main bronchus to enter immediately into the hilum of the left lung.


The right PA is longer and passes rightwards behind the ascending aorta and in front of the right main bronchus & esophagus and below the carina (tracheal bifurcation). It first gives a branch to right upper lung lobe, then enters into the hilum of the right lung.


The normal pulmonary arteries.
http://en.ganfyd.org/images/9/91/Great_vessels.jpg


Pathology:


In PA sling, the pulmonary trunk continues rightwards as the right PA.
The left PA arises to the right of the mid line from the right PA, arches over the right main bronchus, passes behind the trachea & in front of the esophagus leftwards to reach the left lung hilum.


Pulmonary Artery (PA) sling; MPA, RPA, LPA: main, right & left pulmonary arteries.
http://www.childrenshospital.org/cfapps/mml/viewBLOB.cfm?MEDIA_ID=2017


Associated conditions:

  • Bronchus sinus: independent origin of the right upper bronchus from the trachea.
  • Tracheomalacia.
  • Congenital heart disease:
  • VSD.
  • PDA
  • TOF.
  • Interruption of AO arch.


Clinical picture:


Female/male: 1/1.
Respiratory obstruction occurs in most cases, beginning at birth or within the first 6 months.
Sings of unequal lung aeration & mediastinal shift to the left are usually present.


Chest x-ray:


Usually there is unilateral right-sided obstructive emphysema, with
Mediastinal shift to the left.
In barium swallow: Usually there is anterior indentation at the level of the carina.


Bronchoscopy:


Usually there is posterior compression of the distal trachea by a pulsatile mass.
Tracheobronchial anomalies may be seen.


Cardiac catheterization:


Selective pulmonary angiography is diagnostic.


Natural history:


Patients with severe respiratory obstruction usually die early if not treated.


Management:


Surgical procedures:
  • Ligation & re-implantation of the left PA is the treatment of choice.
  • Division & repositioning of the trachea,or the left main bronchus, or division of PDA may be done.

Mortality is 50 % due to:
  • Patency of left PA rarely persists.
  • Severe tracheo-bronchial anomalies.
  • Cardiac anomalies.


Origin of one pulmonary artery from the ascending aorta


Definition and pathology:


Anomalous origin of one PA, usually the right, from the ascending AO and the other PA from RV. This condition is also called: hemitruncus arteriosus.
The anomalous PA is usually on the side opposite to the AO arch.

Associated conditions:
  • PDA in most cases.
  • TOF.
  • VSD.


Clinical picture:


It presents similar to large PDA with rapid development of CHF.
The murmur is usually ejection systolic rather than continuous.
P2 is usually accentuated due to rapid development of PHT.


Electrocardiography:

  • RVH in most cases.
  • RVH + LVH in some cases.


Chest x-ray:

  • Cardiomegaly.
  • Unilateral lung plethora in most cases.
  • Bilateral plethora in presence of PDA.


Lung scan:


Uptake of the radiotracer by the side supplied with the normally arising PA usually the left.


Natural history:


Death usually occurs in early infancy due to CHF or associated anomalies.
PVOD appears in those who live beyond six months.


Management:


Excision of the anomalous PA and establishment of its continuity with the pulmonary trunk.
Operation should be done as early as possible. Cardiopulmonary bypass is not usually needed but should be available.


Pulmonary atresia with ventricular septal defect:


Pathology:


Pathological types:

  • Atretic pulmonary trunk: (Pseudo-truncus arteriosus): Pulmonary arteries (PA) are confluent, ductus may be present or absent, closed or patent.
    • Either proximal atresia with distal patency.
    • Or the whole trunk is atretic.
  • Absent pulmonary trunk with confluent PA: PDA may be associated.
  • Origin of PA from a patent ductus arteriosus: PA are non-confluent.
    • Both PA from PDA, or
    • One PA from PDA while the other arises from RV with atresia.
  • Origin of PA from bronchial arteries: PA are non confluent.
In all types:

  • VSD should be present.
  • The ventricles are usually in the normal position.


The Aorta in patients with pulmonary atresia with VSD:

  • The aorta usually arises from both ventricles, over-riding the VSD. Continuity of the posterior aortic wall with the anterior mitral leaflet (AML) is preserved. This anomaly may be difficult to differentiate from pseudo-truncus form of TOF. 
  • Uncommonly the AO arises entirely from RV. If RV is also inverted, the case may be considered a variation of corrected transposition of the great arteries.


Associated conditions:

  • Aortic arch anomalies:
    • Right aortic arch.
    • Interruption of the aortic arch.
  • Coronary arterial anomalies:
    • Crossing of coronary artery branches infront of RV wall.
    • Single coronary artery.
    • High origin of coronary arteries from AO.
  • Truncal valve anomalies:
    • Mucoid degeneration.
    • Regurgitation.
    • Stenosis.


Clinical picture:


Usually presents as a severe form of TOF with severe cyanosis since birth and rapid deterioration after duct closure.
Rarely there are numerous collaterals with PDA, and cyanosis is mild.


Electrocardiography & chest x-ray: Changes are similar to those of TOF.


Echocardiography: Differentiation between these cases & TOF is mentioned under TOF.


Cardiac catheterization:


Aortography, Selective collateral angiography, and/or Selective pulmonary venous angiography will show PA origin, size & confluence.


Natural history:


Prognosis is much worse than in TOF: Most patients die in infancy except those with numerous collaterals & PDA.


Medical management:


Similar to TOF but Propranolol is not useful.


Surgery:

  • Palliation is done first:
    • Systemic-to-pulmonary shunts, which should be bilateral if PA are non-confluent.
    • Pericardial patch between RVOFT & PA without VSD closure, if there is distal patency.
  • Followed by correction: Correction is possible only if PA are confluent and large enough to carry the required systemic cardiac output.
    • A valved conduit is placed between RV & PA. The conduit will need replacement by a larger one as the infant grows.
    • VSD is closed.


Persistent truncus arteriosus:


Pathology:


Pathological types:


In Persistent Truncus Arteriosus (PTA), a single large artery, the truncus arteriosus, leaves the heart instead of two separate large arteries (aorta & pulmonary trunk).


Collett and Edwards classified PTA into four pathological types:
  • PTA type I: the pulmonary trunk arises from the lateral aspect of the truncus arteriosus, and then divides into the right & left pulmonary arteries. Thus the pulmonary arteries are confluent.
  • PTA type II: the two pulmonary arteries arise side-by-side from the posterior aspect of the truncus arteriosus. The pulmonary arteries are confluent.
  • PTA type III: the two pulmonary arteries arise separately, one at each side of the truncus. Thus the pulmonary arteries are non-confluent.
  • PTA type IV: the pulmonary arteries are absent. The lungs receive blood supply only from the bronchial arteries.


Van Praagh offered another classification:
  • Type A1 is the same as Collett & Edwards type I.
  • Type A2 grouped Collett & Edwards types II & III.
  • Type A3 represents atresia of one of the pulmonary arteries with collateral flow to that lung.
  • Type A4 is truncus associated with interrupted aortic arch.



Collett and Edwards pathological types of PTA.
http://www.ctsnet.org/graphic/56_2_1.jpg





Collett and Edwards PTA type I.
http://www.bristol-inquiry.org.uk/final_report/annex_a/images/chapter_3_a6.jpg





Collett and Edwards PTA type I.
http://www.h4heart.com/h4heart/images/Article_Images/Truncus-Arteriosus.jpg





Collett & Edwards classification compared with Van Praagh classification.
http://www.childrenshospital.org/cfapps/mml/viewBLOB.cfm?MEDIA_ID=2027




The truncal valve is usually tri-leaflet, but may be bi-leaflet or quadri-leaflet, and may be stenotic or regurgitant.
VSD is present in all cases.
Coronary arteries: arise from the truncus and may show the following anomalies
Displaced coronary ostia: usually the origin of the left ostium is displaced posteriorly.
Single coronary artery.
Associated conditions are similar to pulmonary atresia with VSD.


Clinical picture:

  • PTA types I, II & III:
    • Big PA with excess pulmonary blood flow (QP) occurs in most cases, and will present in congestive heart failure (CHF) similar to a large PDA.
    • The few patients with Small PA with diminished QP present with cyanosis.
  • PTA type IV: presents similar to a severe form of TOF.





Electrocardiography: Biventricular hypertrophy.








Echocardiography:

  • RVOFT is absent.
  • There is a single large vessel leaving the heart, and over-riding both ventricles.
  • VSD is present in all cases.
  • Differentiation between PTA, TOF & pulmonary atresia with VSD is mentioned under TOF.


Cardiac catheterization:

  • Truncal angiography reveals the PA origin.
  • Attempts to enter both PA are essential for assessment of the pulmonary vascular resistance (RP).
  • RV angiography reveals absence of RVOFT.
  • VSD is detected with bi-directional shunt.
  • Equal PA & AO pressures.


Natural history:


The majority die before 1 year from severe CHF, PVOD, or severe hypoxia.
Those with type I, II or III who have small PA & reasonable QP survive longer.
Survival to early adulthood is extremely rare.


Surgery:


  • Types I, II or III: Palliation followed by correction, or primary correction.
    • Palliation:
      • With excess QP: PA banding.
      • With small QP: systemic-to-pulmonary shunt.
    • Correction:
      • VSD closure; with the truncal valve placed on left side.
      • RV-PA valved-conduit after excision of PA from the truncus. Conduit will need replacement as the infant grows.
      • Truncal valve replacement may be needed.
  • Type IV: There is no known surgical treatment.


Pulmonary Arterio-Venous Fistula (AVF):


Definition:


Pulmonary AVF is defined as: Direct communication between one or more pulmonary arterial branches and one or more pulmonary veins.


Pathology:


AVF is a thin walled aneurysm fed by one or more arterial branches and from which arising one or more veins. 
There may be single or multiple AVF.
The most commonly affected are the superficial parts of:
  • Right middle lobe.
  • Both lower lobes.
Rarely a pulmonary arterial branch communicates directly with LA.


Rendu – Osler - Weber syndrome:


Rendu – Osler - Weber syndrome consists of:
  • Pulmonary AVF associated with
  • Telangiectasia of other organs.


Complications of pulmonary AVF:

  • Paradoxical systemic embolism, i.e. embolism from the right side of the circulation (e.g. from deep venous thrombosis; DVT) to the left side, particularly to the brain.
  • AVF infection or rupture are uncommon.


Clinical picture:


Familial tendency was reported.
Skin & mucous membrane angiomata may be found.
Large AVF usually present with
various degrees of cyanosis & CHF.
Small AVF may pass undetected
or present only in adulthood.
A continuous murmur may be heard over the fistula.


Chest x-ray:


One or more masses may be seen.
Heart is frequently enlarged.
Mediastinum may be shifted to the other side.



Pulmonary AVF: CXR shows a rounded, well-delineated shadow on the right lower lung zone.
http://www.hmc.org.qa/heartviews/vol1no9/images/Image_Heart_1No9/fig1_376.jpg


Echocardiography:


The finding of a normal heart in a patient with central cyanosis should raise the possibility.
Contrast echocardiography with i.v. saline injection demonstrates opacification of the right side followed few cardiac cycles later by opacification of the left side of the heart.


Pulmonary arteriography:


Pulmonary arteriography will establish the diagnosis except in very small fistulae.



Contrast injection demonstrating at least three pulmonary A-V fistulae. (A-V = arteriovenous).
http://www.hmc.org.qa/heartviews/vol1no9/images/Image_Heart_1No9/fig2_376.jpg


Management:


Surgery is indicated for symptomatic cases even with minimal symptoms due to the potential for life threatening complications & the safety of operation.
  • Usually resection of the affected part of the lung is done.
  • Occasionally, resection of a sub-pleural fistula is possible with ligation of its arteries & veins.

No comments: