Second degree AV block | ACLS-Algorithms.com

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  1. Teresa says

    I had a patient in Mobitz 1 rhythm at a rate of 60. She was frightened “to death” about the test anyway and I told her if she refused the test that was her decision. The doctor didn’t really give her an informed consent because I think he thought it would scare her out of the Lexi more. I told her don’t do it. Her symptoms were very atypical and the doctor told her that he didn’t think it was her heart. She could then see her cardiologist and come back as an outpatient. Actually my question is what is the danger of Lexiscan in this rhythm?

    • Jeff with admin. says

      The danger would be minimal. As with any test utilizing a medication, there are possible side effects that may be experienced.
      “The most common side effects that occurred in clinical trials of Lexiscan were shortness of breath, headache, flushing, chest discomfort or chest pain, dizziness, nausea, abdominal discomfort, a metallic taste in the mouth, and feeling hot. Most common side effects began soon after receiving Lexiscan and went away within 15 minutes except for headache, which resolved in most patients within 30 minutes.” Quote found here.

      Kind regards,
      Jeff

  2. ls1581 says

    Why is TCP the treatment for Mobitz Type II because a dropped QRS = no circulation but on a Mobitz I, the PR lengthens and results in a dropped QRS but there is usually no treatment needed????

    • Jeff with admin. says

      TCP is the treatment of choice for Mobitz Type II because this rhythm does not usually respond well to atropine. Also, Mobitz II will usually be associated with symptomatic bradycardia. Mobitz I will not usually be associated with symptoms or an unstable condition (it is usually benign).

      Kind regards,
      Jeff

      • Amber says

        I think I need some clarification too.

        The dropped QRS in Mobitz II = no circulation. Does the dropped QRS in Mobitz I also present the same danger?

        Please help me understand. It seems to me that both are concerning.

        By the way, your site has been very helpful for me. Thank you for your work on this website. I have already recommended it to several colleagues.

      • Jeff with admin. says

        Unlike Mobitz I, which is produced by progressive fatigue of the AV nodal cells, Mobitz II is an “all or nothing” phenomenon whereby the His-Purkinje cells suddenly and unexpectedly fail to conduct a supraventricular impulse. Mobitz II is much more likely than Mobitz I to be associated with hemodynamic compromise, severe bradycardia and progression to 3rd degree heart block.
        With Mobitz I, after the dropped beat, the process of progressive fatigue and dropped beat starts over. This makes Mobitz I a much safer bradyarrhythmia. With Mobitz II, the conduction can fail and it may no long conduct an impulse (Third degree block). This makes Mobitz II a very dangerous rhythm which must be dealt with as soon as possible.

        Kind regards,
        Jeff

  3. aclsnursewh says

    So helpful when I can replay the rhythms. I am learning quite a bit from watching the videos. Looking forward to more.

  4. okeyi2000 says

    I probably don’t see what others see in this diagram ! where is the dropped beat ,how do you distinguish that from the T wave? The prolongation is clear but can someone show me where we are missing a QRS.

    • Jeff with admin. says

      The dropped beat is the first p-wave in the diagram and the p-wave that is almost in the middle of the image.
      The 2nd non-conducted p-wave occurs on the t-wave after a QRS.
      Kind regards,
      Jeff

  5. Brenda Biancosino says

    Don’t forget the helpful phrase we all learned in nursing school: “Longer, longer, longer, DROP, then we have a Wenckebach”.
    Studying this weekend to recertify for the first time. Love your site. Thank you for all your hard work to make this an enlightening experience as well as reducing my stress level.
    I have already recommended your site and will continue to do so.

    • Dan says

      Thank you Brenda ! I personally love mnemonics. They free me up from that momentary ” pause” ( no pun intended) in the thought process that usually leads to a complete block ( again, no pun intended) in my review. If you have one for the Glascow Coma Scale that would be fantastic!

      • Albert EMT-P says

        And, this is a great site. I just found it today and will make a note to show my EMT-P students at the college. I know this will help them in more ways than one.

  6. Jack says

    (1) The SA Node is the hearts primary pacemaker. (2) The SA Node generates an impulse which propagates across/thru the atria and to the A/V Node in attempt to cause the stimulation to the ventricles (via the Bundle of His and then the Purkinje Fibers. (3) The A/V Nodes primary function is to figuratively act as a gatekeeper as if there was a little man standing there with his hand on the gate allowing signals to pass thru in such a way that optimizes the hearts contracting as a smooth functioning unit (this ensures the greatest movement of blood thru the heart chambers and sets the stage for the greatest EF from the left ventiricle). (4) In the case of heart block the gatekeeper is (for some physiologic reason) restricting the passage of necessary stimulations from above the A/V Node (in the best case scenario the SA Node) from passing thru his gate so that they can transfer their stimulus to the ventricles. (5) If the QRS’s are narrow the block is in the A/V Node (internodal), if the are QRS’s wide (aberrant conduction) then the block is below the A/V Node and somewhere in the Bundle of His or Bundle branches which is much more serious and could ultimately lead to 3rd degree block and will typically create hemodynamic issues for the patient. The MD will most likely end up installing an artificial pacemaker in the patient to safegaurd the possibility of more serious heart failure.

  7. Craig Jenkins says

    why would the ventricle not fire a beat following the AV node non conductive beat/ p wave non conductive beat?

    • Jeff with admin. says

      2nd Degree Block Type 1 (Mobitz I) is usually due to reversible conduction block at the level of the AV node. Some of these are medications such as beta-blockers, calcium channel blockers, and digoxin. Other causes are inferior MI, myocarditis, increased vagal tone, and post heart surgery.

      Essentially the AV node cells are malfunctioning and tend to progressively fatigue until they fail to conduct an impulse.

      Kind regards,
      Jeff

  8. Grape123 says

    With second degree type one seems like there is a qrs after ea p wave it’s just prolonged where with second degree type two there is no qrs. after every p . having trouble with these blocks.

      • jonathanjung says

        Hi Jeff, I don’t understand your answer to Grape123. Grape123 said “With second degree type one seems like there is a qrs after ea p wave it’s just prolonged “. You seemed to agree with that. I thought the P to P interval is constant and PR interval is increasing and then eventually a QRS is dropped. Is this not the case? Also, if I am correct about the QRS being eventually dropped, is this because the P is to close to the QRS and the ventricle has not had time to repolarize? Thanks

      • Jeff with admin. says

        You are correct. I misread Grap123’s question. 2nd degree Type 1 the P to P interval is constant and the PR interval is progressively prolonged until the QRS is dropped and only the p-wave is seen.
        When the QRS is dropped it is because the impulse is not conducted to the ventricles. Most of the time this directly related to a conduction problem between the atria and ventricles and is not directly related to the timing of ventricular repolarization.

        Kind regards,
        Jeff

    • Jeff with admin. says

      It means that the QRS is not present. You will most likely see a p-wave but no QRS. The impulse that is produced in the SA node (p-wave) is not transferred through the AV node and therefore no QRS wave is seen on the monitor.
      Kind regards,
      Jeff

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