Friday, November 12, 2010

Pulmonary Venous Anomalies


Classification of pulmonary venous anomalies:
  • Partial anomalous pulmonary venous drainage (PAPVD).
  • Total anomalous pulmonary venous drainage (TAPVD).
  • Stenosis of pulmonary veins and venules.




Partial anomalous pulmonary venous drainage


Definition:


In partial anomalous pulmonary venous drainage (PAPVD), One or more of the pulmonary veins, but not all, drain into the right side of the heart or one of its tributaries.
Thus, a fraction of the pulmonary venous drainage goes back to the right side of the heart, hence to the pulmonary circulation. Effectively, this is a left-to-right shunt.


Pathology:


The most common 4 types are:
  • Right upper and/or middle lobe drainage into the superior vena cava (SVC): This type may be associated with sinus venosus ASD.
  • All right lung lobes drainage into RA: This type may be associated with polysplenia.
  • All right or right middle & lower lobe drainage into the inferior vena cava (IVC).
  • Left upper or both left lung lobes drainage into the left brachiocephalic vein.


Associated conditions:
  • Atrial Septal Defect:
  • Most PAPVD patients have ASD.
  • 15 % of all ASD patients have PAPVD.
  • 85 % of sinus venosus ASD patients have PAPVD.
  • Other associated conditions include: VSD, tetralogy of Fallot, persistent truncus arteriosus (PTA), and single ventricle.


Scimitar syndrome:


This syndrome consists of:
  • PAPVD of all right lung lobes into IVC.
  • Anomalous arterial supply to the right lung from the thoracic and/or the abdominal aorta.
  • Hypoplastic right lung.
  • Dextroposition of the heart.



Scimitar syndrome: PAPVD into the IVC (arrows).
http://radiographics.rsna.org/content/24/1/e17/F32.large.jpg




Scimitar syndrome: anomalous arterial supply to the right lung from the abdominal aorta.
http://www.turkishjournalpediatrics.org/pediatrics/images/figure_TJP_222_3.jpg




Pathophysiology:


Pathophysiology of PAPVD is similar to ASD, but the shunt is usually smaller, if there is no associated ASD.




Clinical picture:


Symptoms:
  • PAPVD of one vein usually goes undetected.
  • PAPVD of two or more veins: similar to ASD.
Signs:
  • Similar to ASD but S2 splitting is not fixed, though still wide.
In scimitar syndrome:

Older children and adults with Scimitar syndrome typically present with:
  • asymptomatic heart murmurs,
  • recurrent respiratory infections,
  • or mild exertional dyspnea.

Newborns and infants with severe disease present with:
  • varying degrees of cyanosis,
  • respiratory distress,
  • congestive heart failure
  • and pulmonary arterial hypertension.

Treatment of Scimitar syndrome is required in symptomatic patients and may involve:
  • surgical redirection of the anomalous venous drainage to left atrium,
  • ligation/embolization of vascular supply to the sequestered lobe
  • or pneumonectomy.



Chest x-ray:


  • PAPVD of one vein causes no abnormality.
  • PAPVD of two or more veins:
    • Similar to ASD.
    • One may also detect enlargement of the vein in which drainage occurs, e.g. SVC, Azygos, brachiocephalic ...etc.

In scimitar syndrome:
  • Scimitar (crescent-shaped, or Turkish sword-shaped shadow) in right lower lung zone, may be seen.
  • Rightward shift of the heart shadow.



Scimitar syndrome: hypoplastic right lung with mediastinal shift to the right. The heart shadow lies in the right hemithorax, and the tracheal air shadow is shifted to the right.
http://www.radpod.org/wp-content/uploads/2007/08/scimitar-syndrome.jpg





Scimitar syndrome: Scimitar vein (arrows).
http://www.ajronline.org/content/vol182/issue5/images/large/AD0962_19A.jpeg





Scimitar syndrome: Scimitar vein (arrows).
http://circ.ahajournals.org/content/vol103/issue25/images/medium/hc2515577001.gif





Scimitar syndrome: Scimitar vein (arrows).
http://circ.ahajournals.org/content/vol103/issue25/images/medium/hc2515577003.gif




Electrocardiography:


PAPVD of two or more veins produces changes similar to ASD.




Echocardiography:

  • Visualization of pulmonary veins especially by TEE.
  • Secondary cardiac changes similar to ASD if two or more veins are anomalous.




Cardiac catheterization:
  • O2 step-up does not usually help: the shunt is not usually enough to produce a step-up.
    • Step-up in RA should always raise the possibility of ASD.
  • Selective angiography of pulmonary veins is diagnostic, but usually not needed.




Natural history:

  • With significant shunt, the consequences are similar to ASD.
  • If mitral valve disease is associated, with high LA pressure, the pulmonary circulation will be re-distributed to the portions of the lungs with anomalous veins which drain into the low-pressure right side; thus increasing the shunt.




Surgery:


Indications for surgery:
  • Large shunts.
  • Congestive Heart Failure (CHF).
  • Pulmonary Hypertension (PHT).


Surgical procedures:
  • Direct implantation into LA, if the length of the vein allows.
  • Placement of pericardial patches directing pulmonary venous blood to LA through an ASD, which may be created if not already associated.




Total anomalous pulmonary venous drainag


Definition:


In total anomalous pulmonary venous drainage (TAPVD), All pulmonary veins do not join the left atrium and drain anomalously in the right atrium or one of its tributaries.




Pathology:


All veins join a common chamber (confluence) from which a vein arises and terminates in one of the following sites:
  • Supra-diaphragmatic sites:
    • Left brachiocephalic vein.
    • Superior vena cava (SVC).
    • Right atrium (RA).
    • Coronary sinus.
    • Azygos venous system.
  • Infra-diaphragmatic sites:
    • Portal vein.
    • left gastric vein.
    • ductus venosus.
    • Inferior vena cava.


Pathological types:


According to the site of drainage, TAPVD can be classified into four main types:
  • Type I (55% of cases): termination at a supra-cardiac level. The four pulmonary veins converge behind the left atrium and form a common vertical vein; joining the innominate vein, the left brachiocephalic vein, the right superior vena cava, or the azygos vein. Venous obstruction is uncommon.
  • Type II (30% of cases): pulmonary venous connection at the cardiac level: joining either the coronary sinus or the right atrium.
  • Type III (13% of cases): connection at an infra-cardiac or infra-diaphragmatic level. A common vertical vein is formed behind the left atrium, passes through the diaphragm anterior to the esophagus, and joins the portal venous system, the ductus venosus, the hepatic veins, or the inferior vena cava. It is almost always accompanied by venous obstruction & cyanosis, and commonly severe congestive heart failure.
  • Type IV: connections at two or more levels, e.g. the left innominate vein plus the right atrium or the coronary sinus. Other major cardiac anomalies are common in this type.



Types of TAPVD.
http://img.medscape.com/pi/emed/ckb/pediatrics_cardiac/1331339-1331342-897686-1860386.jpg


A large atrial septal defect or a patent foramen ovale should be present in all types, with right-to-left shunt that is essential for survival.


The right heart is enlarged due to volume overload, while the left atrium remains normal in size.


Rarely, multiple veins arise from the common chamber & end in the esophageal wall.




Pathophysiology:

Various degrees of congestive heart failure and cyanosis occur due to the combination of right-to-left and left-to-right shunts.


Left-to-right shunt is present, due to pulmonary venous drainage to the right side of the heart; part of it is delivered to RV, and the pulmonary blood flow is increased in most cases resulting in congestive heart failure.

Cyanosis is present due to right-to-left shunt.
  • Cyanosis is mild when the pulmonary blood flow is large and there is no obstruction to TAPVD.
  • Cyanosis is severe in any of the following cases:
    • High pulmonary vascular resistance.
    • Obstruction to TAPVD.
    • Very low O2 content of systemic venous blood, e.g. during exercise.


Clinical picture:


Symptoms:

  • Most patients have low pulmonary vascular resistance and only mild cyanosis. Cyanosis is delayed to age one month in 50 % of cases.
  • Most patients have CHF from large pulmonary blood flow. CHF appears before 3 months of age in two thirds of cases.
  • Most patients have slow weight gain from CHF.

Thus, the amount of pulmonary blood flow (QP) determines the clinical picture:
  • Excess QP: CHF is favored & cyanosis is mild.
  • Reduced QP: cyanosis is favored & CHF is mild.




Signs:

  • In most cases: Similar to large ASD with hyper-dynamic RV, tricuspid diastolic rumble, S3 and CHF.
  • S2 splitting is wide but may or may not be fixed.
  • Continuous murmur may be heard over the common venous chamber.
  • With obstruction to TAPVD:
    • Marked cyanosis.
    • PHT with loud S2.
    • Little or no murmurs.


Chest x-ray:
  • Non obstructed types:
    • Cardiomegaly.
    • Pulmonary plethora.
  • Obstructed types:
    • Heart size near normal.
    • Pulmonary congestion or edema.
  • Figure of 8 appearance may be seen in cases of return to the left innominate vein.



Type I TAPVD: Snowman or cottage-leaf or figure of 8 sign. The dilated vertical vein on the left, the innominate vein on the top, and the superior vena cava on the right form the head of the snowman; the body of the snowman is formed by the enlarged right atrium.
http://radiographics.rsna.org/content/27/5/1323/F5.medium.gif





Type I TAPVD: Snowman or cottage-leaf or figure of 8 sign (Schematic representation).
http://radiographics.rsna.org/content/27/5/1323/F6.medium.gif





Snowman’ or ‘cottage loaf’ heart shape due to total anomalous pulmonary venous drainage.
http://www.impaedcard.com/issue/issue38/somervillej/fig01.jpg





Cardiomegaly with increased pulmonary arterial markings. There is dilation of both the left and right innominate veins and the right superior vena cava producing the classical "snowman" or "figure of 8" appearance. The superior mediastinum is enlarged secondary to dilation of the right vena cava, innominate vein and ascending vertical vein.
http://www.bcm.edu/radiology/cases/pediatric/images/2e1a.jpg





Drawing shows the return flow of venous blood (arrows). Instead of draining into the left atrium (1), the pulmonary veins (2, 3) converge behind the heart to form a common pulmonary vein (4) that connects to the vertical vein (5), which joins the left innominate vein (6). The left innominate vein drains into the superior vena cava (7). Since all of the systemic and pulmonary venous blood enters the right heart, survival is maintained by a right-to-left shunt through a communication at the level of the atrial septum (8). 9 = right atrium, 10 = right ventricle, 11 = left ventricle.
http://radiographics.rsna.org/content/27/5/1323/F7.medium.gif





Frontal view obtained with angiocardiography in a neonate shows the aberrant cardiovascular anatomy: The upper left heart is bordered by the vertical vein; the superior part of the heart, by the left innominate vein; and the upper part of the right heart, by the dilated superior vena cava.
http://radiographics.rsna.org/content/27/5/1323/F8.medium.gif




Electrocardiography:


Similar to ASD:
  • Right axis deviation.
  • Right atrial enlargement (RAE).
  • Right ventricular hypertrophy (RVH).


Echocardiography:
  • Common chamber may be seen.
  • RA enlargement.
  • RV enlargement.
  • Assessment of PA pressure.


Cardiac catheterization:
  • O2 step-up: according to the site termination.
  • Elevated RA, RV, PA pressures.
  • Pulmonary capillary wedge pressure (PCWP) is also elevated in obstructed types.
  • Pulmonary angiography can show the common venous chamber.


Natural history:


Most patients have progressive CHF & die in the 1st year of life.
Those with severe pulmonary vascular obstructive disease (PVOD) die by 3 months of age.


Surgery:


Timing of surgery:
  • With severe obstruction & pulmonary edema: prompt surgery.
  • With growth failure: at a few months of age.
  • Those doing well: when systolic PA pressure is > 50 % of the systemic.
Surgical procedure:
  • Creation of a large communication between the common chamber & the left atrium, with obliteration of its anomalous connection.
  • Closure of ASD.




Stenosis of pulmonary veins and venules


Embryology:


Two pulmonary veins arise from each lung: left superior & inferior and right superior & inferior pulmonary veins.

The two veins of the left lung unite to from a single left pulmonary vein, and the two veins of the right lung unite to form a single right pulmonary vein.

The single left and single right pulmonary veins unite to form the common pulmonary vein, which opens in the primitive atrium to the left of the septum primum.

Later on during development, the common pulmonary vein as well as the single left & single right pulmonary veins are absorbed into the left atrium to form its posterior smooth part. 

In this way, each pulmonary vein opens separately into the left atrium.


Anatomy:


On both lung hila, the bronchus is posterior and the pulmonary vein (s) are anterior and inferior. The difference between the two involves the pulmonary artery (ies). 
  • On the right side, the artery (ies) lie more or less anterior to the bronchus. 
  • On the left side,  the artery (ies) are the most superior structure, even superior to the bronchus



Left lung hilum (schematic illustration).
http://anatomy.med.umich.edu/images/left_hilum.gif





Right lung hilum (schematic illustration).
http://anatomy.med.umich.edu/images/right_hilum.gif


The four pulmonary veins join the left atrium from its back: two on each side, one above the other, i.e. left superior & inferior, and right superior & inferior pulmonary veins.





The four pulmonary veins entering the left atrium (posterior view).
http://www.capitalcardiology.com/images/figure2.jpg


Pathology:


Two pathologic types are known: 
  • Stenosis of the major individual pulmonary veins, 
  • and Pulmonary venoocclusive disease affecting the small veins & venules.

Stenosis of individual pulmonary veins:

Stenosis is more commonly due to a fibrous intimal lesion at LA junction, but may be due to hypoplasia of the vein.
It may be associated with: ASD or TGA.

In pulmonary venoocclusive disease:

There is obstruction with connective tissue with vascular spaces in-between.
It is not associated with any anomaly.


Clinical picture:


It is an extremely rare anomaly.
Prognosis is extremely bad.
Stenosis of individual veins usually presents early in life while veno-occlusive disease may be delayed.

Symptoms:
  • Pulmonary congestive symptoms: e.g. shortness of breath (SOB).
  • Low cardiac output (COP) symptoms: e.g. fatigue, syncope, chest pain, and
  • poor weight gain.

Signs: 
  • Signs of severe Pulmonary venous congestion.
  • Signs of pulmonary hypertension (PHT).


Chest x-ray:


Manifestations of pulmonary venous congestion, pulmonary edema, and pulmonary hypertension (PHT), but with normal left atrium.




Echocardiography:


Absence of mitral valve disease should raise the possibility.
Echo will also assess the severity of PHT.


Cardiac catheterization:
  • Sever PHT.
  • Hypoxemia.
  • PCWP: elevated in stenosis of individual veins, but normal in pulmonary venoocclusive disease.
  • LA pressure: normal in both types.
  • Pathology can be demonstrated by:
    • Selective pulmonary venous angiography.
    • High quality pulmonary arterial angiography.


Natural history:


Prognosis is grave in both types.
Average survival is 2-4 years.


Medical management:


Control of CHF should be tried with digitalis, diuretics, restriction of activity, oxygen and supportive measures.


Surgery:
  • In stenosis of individual veins: rarely one of the following procedures may be possible;
    • Excision of stenotic segment & re-anastomosis to LA.
    • Excision of an obstructing membrane.
    • Repair with a pericardial patch.
  • In pulmonary venoocclusive disease:
    • Lung transplantation is the only option.
  • Rarely, obstruction in both types is affecting the venous drainage of a small lung part which can be excised.

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