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NBME 23 Answers

nbme23/Block 4/Question#41 (62.9 difficulty score)
Electrophysiology of the heart is studied in ...
Ablation of the atrioventricular node🔍,📺
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 +6 
submitted by amirmullick3(61),
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ECG aTcrgisn. eTh tcsdaeni bewneet SRQ ceslxmpoe is syocunlniuto auotb 6 s,exob os rtea si ieh effunac.sdtT si a 3rd egreed cklob rehwe hte irata dan lsrceitevn ear eatgnbi enynleetnipdd of trohechea dna the RR si vqelitnuae lal .nT aohgle 2dn SQR ecpxmol is PRESU o,nrarw and trheso era sola rr,nwao hhicw asmne reythe gdrnpizoilea thnkas ot eunbld fo s.Hi




 +5 
submitted by aladar50(40),
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oFr the ,ECG I ilaltinyi thoutgh ti wsa d2n eegedr peyT 1 bueseca ti emesde taht teh RP vaislnret rwee sinrcaenig nilut a abet saw ddpre,op btu fi you oklo at it elo,cysl meos of het P asvew wree dinedh in teh RQS mcees.xopl fI yuo coteni att,h nteh ouy nca ees atht treeh erwe rleruga P esvaw dan urlrega SQR pemlsxoc,e ubt rtehe was a coemtepl inisotdoicsa etnbeew mhet whhic easmn ti aws 3dr deeerg atehr kobcl, so eht resnwa aws liaantob near het VA onde.

yotsubato  answer was ablation near the AV node. No it wasnt. It was ablation OF THE AV node itself. Which faked me out. +9  
makinallkindzofgainz  The tangent by user "brbwhat" says that there is "pr lengthening progressively" but there is not. This is 3rd degree AV block. The P waves march out consistently at their own rate, and the QRS complexes march out at their own rate. There is complete dissociation between the P waves and QRS complexes. They have no relationship. This is exactly what you would see if you ablated the AV node. The SA node would continue to to create P waves. The bundle of His would continue to generate junctional (normal looking) QRS complexes. +6  



 +4 
submitted by sajaqua1(557),
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l'nutodW aotlt VA odlan obianalt drsytoe to tmoiycihahtrytu fo the epemcr?aak hTta udwlo aenm atht oblwe eth AV deno hte thhymr dwluo be poidrvde yb a urrnitvcael coi,f nda esoht uulsaly cearte wedi RQS cmlo.psexe

haliburton  that was my reasoning as well. guess not. +  
yotsubato  Shitty NBME grammar strikes again. +1  
charcot_bouchard  No. No guys. Bundle of his located below AV node and it can generate impulse. it calls junction escape rhythm and narrow complex. Below this is purkinje, bundle branch & ventricular muscle. those are wide complex +18  
abhishek021196  Third-degree (complete) AV block The atria and ventricles beat independently of each other. P waves and QRS complexes not rhythmically associated. Atrial rate > ventricular rate. Usually treated with pacemaker. Can be caused by Lym3 disease +2  



 +2 
submitted by fallenistand(24),
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Tshi neqoitsu si ksgain thaw olwud csuae t!sih PR vrtliaen snmseig up is na esusi ta eht VA eo.dn oS aiangltb teh AV oedn wudol acsue rehta b.lkco




 +2 
submitted by krewfoo99(104),
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In rasdob nda bnedo,y It is idas htta htdri dergee htare cbokl is edu to bockl in eth IHS uPjreenki stmey.s So yhw dlwuo inlbaato fo VA dneo saeuc this e?asesid

lWnotdu stdotuercni of tapr fo etfl ceirnvetl eb a tebrte awsern ?

brbwhat  Had the same doubt, Read the part again and found this. Type 2 Is caused when purkinje is hanging by a thread and therefore some impulses conducted, some not. Chb is caused by purkinje not conducting impulses from san, some lower pacemaker ie purkinje or his is depolarising by itself hence venrticles beat independently. There is BLOCK in purkinje for conduction from san. Among options the only thing that establishes this block is avn ablation. +  



 +1 
submitted by methylased(18),
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alugerR rmhyht nout(c hte s,boex yth'ree ,)msae 1 undduecntoc p weav ihtw leaurrg rthmhy tg-;-& ratia nad rlscetienv atnbgie ndneytleienpd ekylil( elinetvrcs ctlr yb Hne-isiu)Pkjr -g&;t- ctmolpee r3)d( trhae oklcb ;&t-g- NVA inlobaat s(hit si caualtyl edno orf pts ihwt Aifb miosete)ms




 +0 
submitted by endochondral1(18),
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I tughoth inoablta fo teh va endo was a tx rof a bfi ton tehra ?blkco

underd0g  The question asks for the CAUSE of the heart block, not treatment. +  



 +0 
submitted by osgoodschlatter10(32),
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I kthin eht noquiest frerse to a nraisoec udaesc yb labitano fo a acirtrulpa genior of eht rha.et

If you kolo euflyracl htere era meso et-preramu rrecnilvuta tseba (ro arthre ujst ).1 e-materruP clunarvriet setba cna be uesadc yb tobalnai fo the AV neod ecsni eht VA deon is epbselnsroi ofr tmhhyr cnortlo by rocillngnto het nrebum fo AS dneo lmssipeu thta rea mitaertsdtn ot teh lrnaterucvi leeralctci eotrk.wn




 +0 
submitted by kard(47),
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attiPens hwo ndueorg an VA dneo bltnaoia era oasl pntlaeidm ithw a maakpecer to help taainmni a onmrla rtaeh trea. T.x orf mtoecple klBco




 +0 
submitted by mutteringly(19),

UW Question Id: 1976 Testing a very similar concept and provides a great explanation for this!




 -2 
submitted by goodkarmaonly(1),
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heT EGC shwso a Motzbi peTy 1 cklob glngronpi(o PR deloolwf yb a deppdor esThew.ae v solbck laylusu seari sa a orydtbcpu fo a antficnsoyudl AV n,edo so aibtlano at eht AV edno is eht omts paeitpaprro asenwr in htsi asce