QUIZ13thDec2017(answersbelow)
1. Whatisthesignificanceof“clockwiserotation”inanECG?
2. Whatismeantbygoodorbad“rabbitears”onECG?
3. Whatarethemanagementprinciplesinpaediatricsevereheadinjury?
4. WhataretheimportantreversiblecausestoconsiderinpaediatricALS?
5. DescribeandinterpretthefollowingECG.
QUIZanswers13thDec2017
1. Whatisthesignificanceof“clockwiserotation”inanECG?RotationoftheECGreferstotheQRSinaxialplane(i.e.theprecordialleads)lookingupatthepatientfromtheirfeet(thesameasanaxialCTslice).ThereferencethatisrotatingisthetransitionpointwheretheQRSchangesfromsumnegative to sumpositive. In anormal ECG, the transitionpoint occursbetweenV3(dominantSwave)andV4(dominantRwave).
Causesofclockwiserotation:• intraventricularconductionabnormalitiesfromdegeneration
- rightventricularheartdisease• shiftoftheseptumtotheleft
- dilatedcardiomyopathy• shiftofthewholeheart
- pulmonaryemphysema- Verticalheart–egtallthinpeople
Althoughcertainlynotalwaysasignofdisease,arecentpublicationconcludedthatclockwiserotationonECGismoderatelyassociatedwithahigherriskofheartfailureandmortality.PatelSCounterclockwiseandClockwiseRotationofQRSTransitionalZone:ProspectiveCorrelatesofChangeandTime-VaryingAssociationsWithCardiovascularOutcomesJAHANov2017ReferenceECGpaedia.org
2. Whatismeantbygoodorbad“rabbitears”onECG?
“Rabbitears”isusedtodescribetheRSRpatterninV1Therabbitearsare“good”iftherightrabbitearistallerthantheleft(rSR’)asthisisassociatedwithRBBBratherthanventriculartachycardia.Iftheleftrabbitearistallerthantheright(Rsr’)thisismoresuggestiveofventricularorigin“badrabbitears”.
3. Whatarethemanagementprinciplesinpaediatricsevereheadinjury?
Theprinciplesarethesameasinadults.Thegoalistominimisesecondaryinjury.
• Adequateoxygenation• Bloodpressuretomaintaincerebralperfusionpressure.• Normalglucosetoprovidesubstrate.• Reduceintracranialpressure
Neurosurgery–urgentCTandneurosurgicalinvolvement Intubationtocontrolventilationforlow/normalpCO2 Headup30degreestoenhancevenousdrainage. Adequatesedationandanalgesia Minimiserestrictionsaroundneck(egcervicalcollars) Osmotictherapy–mannitol,hypertonicsaline-ifsignsofherniation.
4. WhataretheimportantreversiblecausestoconsiderinpaediatricALS?
ThesamefourHsandfourTsareusedinpaediatricALSasinadultALSbutsomearemorepertinentthanothers.
Hypoxia is the common end point leading to paediatric cardiac arrest. Addressingairway and breathing takes precedence over chest compressions and rhythmanalysis. Airway manoeuvres and rescue breaths are done before starting chestcompressions. Airway obstruction from foreign bodies is an important cause toconsiderandmaynecessitateearlyintubation.DecompressingthestomachwithanNGorOGtubeaspartofintubationisimportantinimprovingvenousreturn.
Hypovolaemiaistheothermostimportantcauseofpaediatriccardiacarrestandthisis commonly due to sepsis. 20mL/kg 0.9% saline bolus is generally given in mostpaediatriccardiacarrestswithfurtherbolusesofsaline/bloodgivenasindicated.
Hyper/hypoelectrolytes include checkingbloodglucose level.Hypoglycaemiaaloneusually causes seizures rather than cardiac arrest but children are vulnerable tohypoglycaemia when they are critically unwell. The potential for previouslyundiagnosedmetabolic or endocrine disorders necessitates checking K and iCa onbloodgasanalysis.
Hypothermia is easily achievedwith infants but the historywould usually indicatehypothermiaas thecauseof thearrest. Just likeadults,acore temperatureof lessthanatleast30degreesisrequiredtocausecardiacarrest.
Tensionpneumothoraxisunusualinpaediatrics.
Tamponadeisunusualinpaediatrics.
Toxinsneedtobeconsidered in termsofwhat tablets/medications/poisons/bitesthechildmayhavebeenexposedtoinordertoadministeranappropriateantidote.
Thromboembolismisunusualpaediatrics.
5. DescribeandinterpretthefollowingECG.Regularrhythm230/minPwavesareassociatedwiththeQRS,butappearinSTsegment(nodissociation)QRSisslightlywide120ms(notverywide>140ms)TherearenofusionorcapturebeatsQRSistypicalLBBBpattern(noconcordance,noBrugadasign,noJosephson’ssign)Axisisnormalat60degrees(aVLisisoelectric)QRStransitionpointisnormalbetweenV3andV4NoBrugadacriteriaforVT
! SVTwithLBBB(KeepinginmindthatsafestplanistomanageallasforVT)
But,Ihearyoucry,isitAVRTorAVNRT?
• PresenceofabundlebranchblockishighlyinfavourofAVRTwithanipsilateralaccessorypathway
• RP interval is shorter in AVNRTwith the Pwavemixed in the QRSwhereas inAVRTmostlypresentwitharetrogradePwaveaftertheQRS
• STelevationinaVRfavoursAVRTastheSTsegmentisthoughttobedisorderedbytheretrogradeconductedPwave
! AVRTwithleftaccessorypathway
Neiger JDifferentialdiagnosisof tachycardiawitha typical leftbundlebranchmorphologyWorldJCardiol2011May26;3(5):127–134Haghjoo M Value of the aVR lead in differential diagnosis of atrioventricular reentranttachycardiaEuropace(2012)14,1624-1628
