TOTAL ANOMALOUS PULMONARY VENOUS CONNECTION,CJ JORDAAN 29/01/04,Definition:,Uncommon congenital cardiac defect (1-3%) in which there is no direct communication between the pulmonary venous drainage and the Left Atrium. All the pulmonary veins connect/drain to the Right atrium.,Embryology:,Total anomalous pulmonary venous connection (TAPVC) develops when the primordial pulmonary vein fails to unite with the plexus of veins surrounding the lung buds. This results in return of pulmonary venous blood to the heart via a systemic vein, and subsequently to the right atrium.,Classification:,TAPVC is classified according to the site of connection: Supra cardiac: includes connections to the left Innominate vein, the SVC, or the Azygos Cardiac: includes connections to the coronary sinus or directly to the right atrium Infra cardiac: includes connections below the diaphragm to the portal vein, hepatic veins, ductus venosus or IVC. Mixed: involves connections of two or more of these types; at least one of the main lobar pulmonary veins is draining differently from the others Each category can be further classified as obstructive or non-obstructive.,1. Supra cardiac TAPVC:,Most common form of TAPVC-45% Bilat draining of pulmonary veins (PV) to Common Pulmonary Venous Sinus (CPVS). This confluence drains via Vertical Vein (VV) to Innominate vein, SVC or Azygos. Stenosis common ( +/- 40-60%): Pulmonary vein systemic connection, Vascular vice or Long thin VV,-CPVC location Supra cardiac TAPVC -Sites of stenosis,2. Cardiac TAPVC:,Accounts for 25% of TAPVC VV drains mostly to Coronary Sinus, seldom directly to Right atrium. Enlarged coronary sinus acts as the CPVS with only a thin wall of myocardium separating sinus and the Left atrium. Right atrial draining: Seen in RA isomerism. Associated with absent Coronary sinus, huge or absent intra atrial septum. VV opens as a fibrous midline confluence. STENOSIS: Rare. May occur where the CPVS joins the Coronary sinus, or at the mouth of the coronary sinus (persisting Thebesian valve),3. Infra cardiac TAPVC:,Accounts for 25% of TAPVC The common pulmonary vein drains through the diaphragm to the portal vein, ductus venosus or seldom to the IVC. Has the greatest propensity for STENOSIS: -May be compressed where it penetrates the Diaphragm, -Connecting vein is narrowed at its junction with the portal vein, -VV has a thickened wall with intimal proliferation, -portal sinusoids (Liver) offer additional obstruction to venous return,Infra cardiac TAPVC:,4. Mixed APVC,Involves a combination of connections of two or more of the subtypes (at least one of the main lobar pulmonary veins is draining differently from the others.),Anatomy,RA: Enlarged and thick walled. Decreased compliance. LA: Volume 53% less than predicted. LA auricle is normal in size, decrease in LA can be explained by the absence of the pulmonary vein component. ASD: ASD or PFO must exist for survival. Usually of adequate size and not obstructive. Obstruction leads to a decreased R to L shunt with pulmonary venous obstruction and Pulm. Hypertension. Presents as a severely sick neonate.,Anatomy,LV: Normal in size, wall thickness and mass, but decreased LV cavity ( due to leftward displacement of septum secondary to right ventricle pressure-volume overload.) RV: Varies in size, depends on magnitude of pulmonary blood flow, pulmonary venous stenosis, point of PV connection. (Infra cardiac connection- RV not dilated or hypertrophied) PA: Most infants have marked pulmonary hypertension. Structural changes are usually found in the lungs even in the youngest infants dying of TAPVC. Increase in pulm. Arterial muscularity-increase in wall thickness and extension of muscle into smaller and peripheral arteries. Vein wall thickness is also increased.,Pathophysiology:,All pulmonary venous blood returns to the right atrium. (common mixing chamber) A right-to-left shunt at the atrial level (-RV compl, ASD size, Rp) Increased pulmonary blood flow and pulmonary venous obstruction will eventually result in pulmonary hypertension. Infra diaphragmatic draining.,Pathophysiology:,Pulmonary vein stenosis: Obstruction to pulmonary draining with increase in pulm. venous pressure. Capillary leak with interstitial edema. Reflex pulm. vaso constriction and progressive increase in Rp =pulmonary hypertension. Increased PAP leads to increased RV pressures (sometimes supra systemic) with RV failure, decreased pulm. blood flow, decreased Qp:Qs, decreased systemic SAT, peripheral hypoxia and metabolic acidosis with multi organ failure. PFO obstruction: Increased LAP, impedes pulm. venous return, producing pulm. hypertension.,Burchell principle:,A direct relationship exists between the magnitude of pulm. blood flow and systemic saturation. The Qp:Qs is determined by magnitude of pulmonary blood flow, pulm. blood flow is inversely related to Rp. Thus an increase in PAP and Rp leads to a decrease in pulm blood flow with a decreased systemic SAT. SAT less th