ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Heart Block: The Clinical Significance Of It’s Degrees And Etiology

Updated on January 15, 2014

Heart Block

Velocity of conduction in the atria is 1m/sec. It is 0.2m/sec in the A-V nodal tissue and 4m/sec in the purkinje system. The A-V node being less conductive, there is a delay of 80-120m/sec, at this level.
Velocity of conduction in the atria is 1m/sec. It is 0.2m/sec in the A-V nodal tissue and 4m/sec in the purkinje system. The A-V node being less conductive, there is a delay of 80-120m/sec, at this level. | Source

Degrees Of Heart Block

Delay or interruption of the conduction of impulses from the SA node along the normal pathway to the ventricular myocardium results in heart block. The SA node produces impulse at the rate of 70-80/min. Velocity of conduction in the atria is 1m/sec. It is 0.2m/sec in the A-V nodal tissue and 4m/sec in the purkinje system. The A-V node being less conductive, there is a delay of 80-120m/sec, at this level. Heart block can be caused by abnormalities of impulse production at the SA node, or conduction ate the sinoatrial junction, A-V node of the bundle of His and its branches.

Sinus arrest is a condition whereby the sinus node ceases to produce impulse.

Sino-atrial block: Impulses arising from the SA node are blocked at the junction of SA node with the atrial musculature and hence the beat is missed. The ECG shows the total absence of the PQRST complexes, corresponding to the missed impulses.

Atriventricular block (A-V block): This is caused by abnormalities at the A-V junction or along His-Purkinje system. Three forms may occur.

  1. First degree A-V block: Clinical detection of this form may be difficult. The ECG shows prolongation of P-R interval exceeding 0.2 sec.
  2. Second degress A-V block: This block is of two types. In both the types, some of the impulses from the S-A node fail to reach the ventricles, resulting in dropped beats.
  • Mobitz type I block (Wenckebach phenomenon): The P-R interval increases progressively till a QRS is totally missed. This is clinically evident as a regular irregularity. Almost always this is caused by a block in the A-V node.
  • Mobitz type II: This is a more serious arrhythmia than type 1. The P-R interval of the conducted beats is fixed, but some of the P-waves are not conducted to the ventricles and are not followed by QRS. The P-waves out number the QRS complexes. Mostly this is due to a block in the His-Purkinje system and more often the QRS may show some widening.
  1. Third degrees heart block (Complete block): In this condition, impulses from the SA node are totally interrupted from reaching the ventricular muscle. The ventricles respond to impulses produced by the A-V junction or areas distal to that. When the impulses arise from the ventricles (idioventricular rhythm), the rate is usually less than 40/mt. The ECG shows regular P-waves occurring at 70-80/min and QRS complexes are usually bizarre occurring at a rate of about 30/min. There is total dissociation between the P-waves and QRS complexes. The pulse is regular in established complete heart block because the QRS complexes are produced regularly.

Primary Degeneration Of Conducting Tissues Can Cause Heart Block

Diseases affecting the myocardium: Myocardial infarction, chronic coronary artery disease and myocarditis
Diseases affecting the myocardium: Myocardial infarction, chronic coronary artery disease and myocarditis
  1. Primary degeneration of the conducting tissues.
  2. Diseases affecting the myocardium: Myocardial infarction, chronic coronary artery disease and myocarditis.
  3. Drugs and toxins: Digoxin, quinidine, procainamide, beta adrenergic blocking drugs, cerbera thevetia and cerbera odollam.
  4. Trauma to the conduction tissue during surgery.
  5. Congenital abnormality of the conducting tissue (Congenital heart block).
  6. Infection: Tertiary syphilis, south American trypanosomiasis (Chaga’s disease) and cysticercosis.

These are the various stimulators of Heart block. With this, we can adequately understand and also try to prevent the occurrence of heart block.

© 2014 Funom Theophilus Makama

Comments

    0 of 8192 characters used
    Post Comment

    • married2medicine profile imageAUTHOR

      Funom Theophilus Makama 

      4 years ago from Europe

      Thanks a lot Alphadogg16

    • Alphadogg16 profile image

      Kevin W 

      4 years ago from Texas

      Nice and informative hub married2medicine on the most important muscle in the human body. However, I would suggest maybe explaining a little more in detail in layman terms. The average person not in medicine/healthcare has no idea what a SA node is. Just a thought, voted up on your hub though.

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com 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: https://hubpages.com/privacy-policy#gdpr

    Show Details
    Necessary
    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 googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    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)
    Marketing
    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.
    Statistics
    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)