Addicudo
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Post MI pt , 37 year Male , showing Third degree block on the ECG ... Physician plans to insert a Single lead pace maker with the lead placed at the apex of the Rt. Ventricle .. What will be the finding on ECG after the placement of the lead ?
A) Prolonged QRS
B) Prolonged ST
C) LBB
D) RBB
E) Normal ECG tracing
Edited by Addicudo on 06/02/07 - 09:05 AM
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| arlete
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LBB with negative QRS complex in II if in the apex.
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| doc179
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A
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| Luckyall
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because in most cases the block occurs below the His bundle, i d say a wide QRS is correct , so my answer in A)
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| drduck
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thats a third degree block....or complete heart block
no passage of atrial impulse to ventricle...
ventricles be beating on its own.....as it is now the pacemaker...
at the apex of heart....there will be ventricular rhythm.
i m a bit confused...
anyone help me out with this one
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| doc179
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hmm...any ectopic location of the beat origination in the ventricle would produce a prolonged QRS complex
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| Addicudo
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huMMm .... I opted for LBB .. due to the relative disassociatoin between the two sides .. as the LEAD is placed on the apex therefore the Right Ventricle .. !!
And since NORMALLY i.e thru the AV nodal pathways impulses spread to both the ventricles in a coordinate fashion ... The ECG is then as we normally see it .. !!
But here there would be impulse conduction via the Muscle fibers ... so .. thus a dealy for the Left Ventricle .. ! and therefore on ECG signs of a LBB .. !
Thats how I thought this up .. !
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| Addicudo
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And NOW ..  CAN an impulse pass via the Right Vent walls to the LEFT vent walls .. WHEN there is an interventricular septum in between .. and as far as I remember .. Its acts as an insulation too .. Or it doesnt .. ?? !
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| nochoice
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so is it LBB or prolonged QRS?
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| arlete
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Addicudo:
No, it does not act as an insulation, so the pacemaker captures both ventricles, with delay on left, like you said. If it is truely in apex, II will be negative. The insulation happens between atriums and ventricles, where only the AV node or an anomalous pathway are capable of conduction.
LBB IS a prolonged QRS (by definition, any complete bundle branch block is greater than 0.12 s), so now I am not sure what they consider the right answer.
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| doc179
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guyssssssss apex is left ventricle its not right ventricle
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| Luckyall
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yessssssssssssssssssssss, cannot believe how they can even think that RV is the Apex !
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| arlete
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Single lead pacemaker is always implanted on right ventricle, guys! The lead goes inside the vein, no sense in passing it through the foramen ovale to atach it to the left ventricle. That is too complicated and brings no advantage to the patient.
If you see an EKG pattern that suggests left ventricle stimulation (RBBB), chances are the lead is outside the heart, on the pericardium.
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| doc179
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not arguing with that concept arlete, but the qn says apex of the heart, apex of the heart can only be lt ventricle its not right, if they want us to think that its right ventricle, then they would say so, they wuld not say just apex of the heart.
my opinion.
Edited by doc179 on 06/01/07 - 04:26 PM
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| new_n_lost
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WHERE IS THE Q FROM ?? CAN U PLZ TELL US THAT
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| doc179
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Hey Addicudo, where is this qn from? I am just wondering whether this has an ECG tracing with it. Could you pls let me know.
Thanx.
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| doc179
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look the q asks wht will be the ECG AFTER PLACING A SINGLE LEAD PACEMAKER . Agreed the pacemaker is placed on the Right Ventricle but still u wont have a LBBB cos then whts the use of the PACEMAKER PLZ GO THRU THE LINK and after reading that u will surely understand Y THE ANS IS PROLONGED QRS
http://missinglink.ucsf.edu/lm/pacemaker_module/i...
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| Luckyall
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common guys, this qs is a very good one, dont even ask where is it from... just think.. who could make such Qs
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| arlete
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doc 179:
I think the question would be better if it said RV apex, at least it would be closer to reality. When we implant pacemakers, RV apex is the most common site, not apex of the heart, agree with you that that would be LV.
The electrical impulse goes from the RV to the LV, so it is functionally like a LBBB, but it's not a real one, because the impulse is not coming from the upper side, normally conducted by the RBB and having a delay on LBB.
So I agree with you, I am changing my answer to prolonged QRS.
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| arlete
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On the other hand, take a look at this:
http://www.mamc.amedd.army.mil/cardiology/book126...
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| doc179
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I agree with you as well arlete about the functionally looks like LBBB but not LBBB. Thanks for the link. and the link also says that.
Thanx addicudo for the qn.
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| Addicudo
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Guyss ... Sorrry .... for that ..>!!! THEY mentioned in the question .. that they planted the LEAD at the RIGHT Ventricular APEX ... !!!
Sorry for that .. !!!!
And niCe link .. !!!
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| ssrpk
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wow tht was a very good discussion....
for the sake of summary, left bundle branch block pattern [which is signified by a double R-wave in lead V5-6 which are left ventricular leads]is due to delayed conduction in the left ventricle, LBBB will also occur in third degree heart block although it won't be presented by a QRS with double R waves in V5-6 leads, because the escape rhythm may not neccassarily be originating just distal to the block or even in the purkinje fibers, therefore they have bizzare and widened QRS complex due to conduction of impulse in the ventricles through a completely aberrant pathway, the same will be the case with cardiac pacemaker, only here the bizzare QRS will be preceeded by a pacemaker spike.
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| arlete
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ssrpk:
The QRS morphology in complete heart block depends on where the scape rhythm is coming from. If it's from the His bundle, it's narrow, if it comes from RV, it's LBBB, if it comes from LV, it's RBBB.
(Just adding).
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| arlete
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Still... A AND C are both right for me...
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