Partial anomalous pulmonary venous connection: Difference between revisions
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'''Associate Editor-in-Chief:''' Keri Shafer, M.D. [mailto:kshafer@bidmc.harvard.edu] | '''Associate Editor-in-Chief:''' [[User:KeriShafer|Keri Shafer, M.D.]] [mailto:kshafer@bidmc.harvard.edu] | ||
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Revision as of 21:40, 7 January 2009
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Associate Editor-in-Chief: Keri Shafer, M.D. [2]
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Synonyms and related keywords: PAPVC, isolated partial anomalous pulmonary venous connection
Overview
In partial anomalous pulmonary venous connection (PAPVC) with intact atrial septum a portion (hence the term partial) of veins return to the right atrium rather than the left atrium. As a result oxygenated blood returning form the lung returns to the venous system via the right atrium.
Epidemiology and Demographics
Autopsy data suggests that PAPVC has an incidence of 0.4-0.7%. Many of these autopsy cases were asymptomatic and as a result the clinical incidence of PAPVC is much lower.
Associated Conditions
PAPVC is present in approximately 10% of patients with an ASD. Depending upon the hemodynamics and magnitude and direction of shunting, an ASD may either improve or exacerbate the shunting associated with a PAPVC.
Differentiaion of PAPVC from Total Anomalous Pulmonary Venous Connection (TAPVC)
These two defects have a common embryologic origin. However, in contrast to PAPVC, in TAPVC all pulmonary venous return is to the right atrium.
Anatomy and Anatomic Variants
Anatomically, PAPVC can involve a wide variety of connections, and PAPVC from the right lung is twice as common as PAPVC from the left lung. The most common form of PAPVC is one in which a right upper pulmonary vein connects to the right atrium or the superior vena cava (SVC). This form is almost always associated with a sinus venosus type of atrial septal defect (ASD).
In addition to draining into the right atrium, the anomalous right pulmonary veins can also drain into the inferior vena cava. Similarly, the left pulmonary veins can drain into the innominate vein, the coronary sinus. More rarely, the left pulmonary vein can drain into the cavae, the right atrium, or the left subclavian vein.
Pathophysiology
The most important determinant of the ratio of pulmonary blood flow (Qp) to systemic flow (Qs) (the Qp/Qs ratio or the magnitude of the shunt) is the number of pulmonary veins that drain into the RA. The greater the number of pulmonary veins that drain into the [[RA}}, the greater the magnitude of the shunt. It has been speculated that when the proportion of returning pulmonary veins that drain anomalously exceeds 50% of the pulmonary veins, then the anomaly is clinically significant. The position of the patient relative to the position of the anomalous pulmonary veins may also influence the magnitude of shunting. If a patient is standing, pulmonary blood flow is predominantly to the middle and the lower lobes of the lung. If there are a greater proportion of anomalous veins draining these portions of the lung, then standing can exacerbate the shunt. Other noncardiac conditions may influence the magnitude of shunting. One such disease state is the scimitar syndrome or pulmonary venolobar syndrome. In scimitar syndrome there is abnormal right-sided pulmonary venous drainage into the inferior vena cava. There is also malformation and/or hypoplasia of the right lung along with anomalous arterial flow to the right lung.
Natural History and Complications
There are few symptoms in infancy or childhood. After many years of excess pulmonary venous return, right atrial and right ventricular (RV) dilation may occur as a result of volume overload in the adult. RV dilation and enlargement is in turn associated with arrhythmias, cor pulmonale or right-sided heart failure, and, in some patients, the development of pulmonary hypertension.
Genetics
There is no known genetic association.
Diagnosis
In general, children with partial anomalous pulmonary venous connection (PAPVC) are asymptomatic. Symptoms usually do not arise until adulthood following prolonged volume overload of the right ventricle.
Symptoms
- Palpitations are usually due to supraventricular arrhythmias which in turn are likely due to right atrial dilation.
- Dyspnea may develop in adults as a result of right ventricular volume overload and ensuing cor pulmonale. It has been said that dyspnea may occur earlier in children if over 50% of the pulmonary veins drain anomalously.
- Hemoptysis may reflect the development of pulmonary hypertension and is rare.
- Pedal edema can occur as a result of right ventricular failure or cor pulmonale.
Cardiac Magnetic Resonance (CMR)
CMR is the imaging modality of choice in diagnosis and evaluating the structure of PAPVC. Other imaging modalities such as echocardiography may diagnose the presence of PAPVC, but CMR may yiled valuable insight into the number and location of pulmonary veins that are anomalously draining into the right atrium.
Chest X Ray
Cardiomegaly and increased vascular markings may be observed on chest x ray. The main pulmonary artery may be dilated. The mediastinum may be widened due to veins draining from the left lung into the left vertical vein.
There may be evidence of the Scimitar syndrome in which an anomalous vein drains into the inferior vena cava at the level of the diaphragm.
It should be noted that the chest x ray may be normal.
Echocardiographic Findings
The presence of right ventricular dilation may be the first sign that PAPVC is present. The next step is to visualize all the major pulmonary veins and their points of insertion into the heart. The use of agitated saline and contrast echocardiography can be of help in more refined imaging of the venous architecture and the connections to the heart. When agitated saline is injected in the left arm vein, there may be negative contrast in the innominate vein at the side of the anomalous venous drainage from a left pulmonary vein in patients with PAPVC. Transesophageal echocardiography may also be useful in further imaging the venous structures. Becuase PAPVC is associated with ASDs, the interatrial septum should be carefully evaluated.
Computed Tomography
If echocardiographic visualization of structures is non diagnostic, then contrast-enhanced CT is an alternative imaging modality.