ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Left To Right Shunt Lesions: Atrial Septal Defect (ASD)

Updated on January 13, 2014

The Different Shunts



This is the commonest congenital heart disease found in adults. This is characterized by the presence of one or more defects in the inter-atrial septum. Based on the developmental defect there are mainly three types- Ostium secondum, Ostium Primum and the sinus venosus type of defects. Ostium secondum defect occurs in the region of the fossa ovalis and this is the commonest. This results from the maldevelopment of the septum second. The only abnormality is the presence of atrial septal defect.

Ostium primum defect is the result of abnormal development of the endocardial cushion. The defect is in the lower portion of the inter-artrial septum. This may be associated with cleft mitral or tricuspid valve resulting in their incompetence. Sinus venosus type of defect occurs in the upper portion of the inter-atrial septum. It is due to the abnormality of development of the upper part of the inter-atrial septum and it is associated with anomalous connection of one or more pulmonary veins to the superior vena cava or right atrium.

In ASD, the blood is shunted from left atrium to right atrium and then to the right ventricule. The right ventricular output and the pulmonary blood flow are considerably increased. This leads to progressive enlargement of the right atrium, right ventricle and pulmonary arteries.

Artria septal defect is found more in females. This may occur as an isolated anomaly or in association with other intracardiac anomalies like pulmonic stenosis or ventricular septal defect. Rheumatic mitral stenosis may coexist with ASD (Lutembacher’s syndrome).

The Shunts

A pulmonic ystolic murmur may be heard. The murmur and the thrill are produced by increased blood flow through the pulmonary valve.
A pulmonic ystolic murmur may be heard. The murmur and the thrill are produced by increased blood flow through the pulmonary valve. | Source

Clinical Features

Palpitation and recurrent respiratory infection are the usual symptoms. Effort intolerance usually develops in the third and fourth decades and thereafter features of congestive heart failure develop. Clinically, there is cardiac enlargement with hyperactive precordium as a result of right ventricular enlargement. Pulmonary artery pulsation is felt in the left second intercostals space. In some cases, a systolic thrill may be felt over the upper part of the sternum on the left. A pulmonic ystolic murmur may be heard. The murmur and the thrill are produced by increased blood flow through the pulmonary valve. The second sound in the pulmonary area is widely split since the pulmonic valve closure is delayed by the larger volume of blood to be ejected by the right ventricle. During inspiration more venacaval blood flows into the right side of the heart and during expiration more of left atrial blood flows through the shunt. These phenomena account for the ejection of the same quantity of blood across the pulmonary valve during inspiration and expiration. Therefore, the split of the pulmonary second sound remains fixed. This is the single most characteristic feature of ASD. Increased flow across the tricuspid valve during diastole may produce a tricuspid mid-diastolic murmur, best heard along the left lower sterna border. This is usually preceded by a right ventricular third heart sound.

Course And Prognosis

Small atrial septal defect may remain asymptomatic. When the shunt is large, the right-sided chambers progressively enlarge. Pulmonary hypertension develops in course of time. The pulmonary pressure may be elevated to high levels and the same is reflected in the right ventricule and right atrium. When right atrial pressure exceeds that of the left atroum, the blood flow is reversed and this leads to the development of central cyanosis. This phenomenon is called Eisenmenger Syndrome. Thereafter, the course is rapidly downhill and death occurs due to congestive heart failure. Primum type of ASD carries a poorer prognosis than the secondum type. Other complications include paradoxical embolism, arrhythmias like atrial fibrillation and very rarely infective endocarditis.


Atrial septal defect can be repaired surgically. Surgery is preferably done before marked elevation of pulmonary artery pressure develops. Cases with severe irreversible pulmonary hypertension are not suitable for surgery.

© 2014 Funom Theophilus Makama


    0 of 8192 characters used
    Post Comment

    No comments yet.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)