© 2018 Sociedade Portuguesa de Cardiologia. Published by Elsevier España, S.L.U. This is an open access article under the CC-BY-NC-ND license.Cardiac imaging has brought about spectacular innovations in the diagnosis, treatment, monitoring and outcome of cardiovascular disease, and the different imaging modalities constitute a set of tools that are crucial to clinical practice, research and education. The quality and accuracy of the information they provide have improved enormously in the last ten years, in parallel with other impressive technological advances in health care.info:eu-repo/semantics/publishedVersio

Almeida, Ana G.

Revista Portuguesa de Cardiologia (English Edition)

English

Repositório da Universidade de Lisboa

TC cardíaca na ablação da fibrilhação auricular - one-stop-shop?

Universidade de Lisboa: Repositório.UL

Rev Port Cardiol. 2018;37(11):885--887www.revportcardiol.orgRevista Portuguesa deCardiologiaPortuguese Journal of CardiologyEDITORIAL COMMENTCardiac  computed  tomography  for  atrial  fibrillationablation -- a one-stop  shop?TC  cardíaca  na  ablação da  fibrilhação  auricular  --  one-stop-shop?Ana G. AlmeidaHospital  Universitário  de  Santa  Maria,  Faculdade  de  Medicina  da  Universidade  de  Lisboa,  Lisboa,  PortugalAvailable online  28  November  2018breadtenbthresahssblHdCardiac  imaging  has  brought  about  spectacular  innovationsin  the  diagnosis,  treatment,  monitoring  and  outcome  of  car-diovascular  disease,  and  the  different  imaging  modalitiesconstitute  a  set  of  tools  that  are  crucial  to  clinical  practice,research  and  education.  The  quality  and  accuracy  of  theinformation  they  provide  have  improved  enormously  in  thelast  ten  years,  in  parallel  with  other  impressive  technologi-cal  advances  in  health  care.Cardiac  computed  tomography  (CCT)  has  been  at  theforefront  of  clinical  practice  since  the  introduction  in  2004of  64-slice  scanners,  which  enabled  highly  accurate  andreproducible  assessment  of  coronary  lesions.  Other  clinicalapplications  have  also  emerged,  including  in  electrophysi-ology  for  planning  of  procedures  such  as  ablation  and  leftatrial  appendage  closure  for  the  treatment  of  atrial  fibrilla-tion  (AF),  which  are  now  well-established  therapies.1 Whenplanning  ablation,  CCT  provides  high-resolution  anatomicalimages  of  the  left  atrium  and  pulmonary  veins  that  canDOI of original article: https://doi.org/10.1016/j.repce.2018.03.018 Please cite this article as: Almeida AG. TC cardíaca naablação da fibrilhação auricular -- one-stop-shop?  Rev Port Cardiol.2018;37:885--887.E-mail addresses: anagalmeida@gmail.com,amalmeida@medicina.ulisboa.pttts2174-2049/© 2018 Sociedade Portuguesa de Cardiologia. Published by EBY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)e  integrated  during  the  procedure,  increasing  its  accu-acy  and  shortening  its  duration.  Importantly,  it  can  alsoxclude  the  presence  of  thrombi  in  the  left  atrium  andtrial  appendage,  an  essential  step  in  the  ablation  proce-ure  and  one  that  has  traditionally  been  performed  usingransesophageal  echocardiography  (TEE).However,  CCT  has  its  disadvantages,  notably  the  need  forxposure  to  ionizing  radiation  and  for  administration  of  iodi-ated  contrast.  While  the  latter  is  relatively  easy  to  manage,y  appropriate  selection  and  preparation  of  patients,  radia-ion  exposure  is  unavoidable  and  carries  potentially  seriousealth  risks.  The  biological  effects  of  ionizing  radiation  areelated  to  the  cumulative  effective  dose,  and  its  stochasticffects  may  include  the  development  of  cancer,  althoughuch  effects  are  assumed  to  come  into  play  only  followingcute  radiation  exposure  at  high  doses  (figures  of  >100  mSvave  been  suggested).2 The  risks  associated  with  low  doses,uch  as  those  used  for  diagnostic  exams,  are  less  well  under-tood;  it  has  been  suggested  that  there  is  a  threshold  doseelow  which  there  is  no  harmful  effect,  or  even  that  lowevels  of  radiation  are  protective  against  the  risk  of  cancer.owever,  given  the  lack  of  convincing  evidence  from  epi-emiological  studies,  it  is  generally  accepted  that  exposureo  any  level  of  radiation  carries  risks,  and  that  thereforehe  ‘‘as  low  as  reasonably  achievable,’’  or  ALARA,  principlehould  be  applied,  by  which  the  use  of  imaging  studies  shouldlsevier España, S.L.U. This is an open access article under the CC.8bedcidiciwacwaiiwnaepiltaildlteA1acwiqd3dssoin3iaanubtnwtutuisgrtaoodssrrlhstqnrCTR123486  e  rational  and  reasonable  in  order  to  minimize  radiationxposure  as  far  as  possible.3Recent  technological  developments,  as  well  as  improvediagnostic  ability,  have  also  led  to  significant  changes  inlinical  attitudes  and  in  diagnostic  guidelines,  for  examplen  the  use  of  CCT  for  assessment  of  stable  coronary  arteryisease.4The  technological  advances  that  have  resulted  inmproved  image  quality  and  lower  radiation  doses  includeurrent  modulation,  prospective  acquisition  and  iterativemage  reconstruction,  together  with  developments  in  hard-are  including  dual-source  scanners  with  high  pitch  andcquisition  volume,  enabling  image  acquisition  in  a singleardiac  cycle.  This  is  particularly  advantageous  in  patientsith  arrhythmias,  including  AF,  which  is  the  most  frequentrrhythmia  in  the  general  population,  especially  in  olderndividuals.Clinical  validation  of  new  technological  developmentss  the  subject  of  considerable  study,  since  the  speedhich  such  developments  become  available  implies  theeed  for  equal  rapidity  in  validating  them  for  clinicalpplication.It  is  against  this  background  that  a  study  by  Marquest  al.5 is  published  in  this  issue  of  the  Journal,  based  on  arospective  registry,  from  which  270  patients  were  selectedn  whom  CCT  was  performed  prior  to  AF  ablation  to  detecteft  atrial  thrombi,  aiming  to  assess  the  impact  of  CCT  pro-ocol  optimization  and  technological  advances  on  contrastnd  radiation  doses  and  on  image  quality.  The  study  is  a  goodllustration  of  the  difficulties  associated  with  rapid  techno-ogical  advances  in  CCT  with  which  the  authors  have  had  toeal.The  study  population  were  divided  into  three  chrono-ogically  ordered  groups  representing  different  stages  ofechnological  development.  The  first  two  groups  underwentxams  using  a  first-generation  dual-source  64-slice  scanner. conventional  retrospective  protocol  was  used  in  Group,  with  tube  current  modulation  and  peak  voltage  selectedccording  to  body  mass  index,  while  in  Group  2  the  proto-ol  was  optimized,  using  a  prospective  protocol  in  patientsith  regular  or  arrhythmic  heart  rate  and  little  R-R  variabil-ty,  and  reducing  peak  voltage  and  contrast  volume.  Imageuality  was  similar  in  these  two  groups  but  radiation  doseecreased  substantially,  from  5.6  mSv  to  1.3  mSv.  Group,  the  most  recent,  was  studied  with  a  third-generationual-source  192-slice  scanner  using  iterative  image  recon-truction.  As  well  as  enabling  images  to  be  acquired  in  aingle  heartbeat,  which  has  significant  advantages  in  casesf  arrhythmia,  this  protocol  also  led  to  a  marked  reductionn  radiation  dose,  to  a  median  of  0.6  mSv,  as  well  as  to  a  sig-ificantly  smaller  contrast  volume.  Image  quality  in  Group was  also  better  than  in  the  previous  two  groups  accord-ng  to  both  subjective  (visual)  and  objective  (quantitative)ssessments.The  choice  of  quantitative  parameters  for  the  objectivessessment  was  interesting:  signal-to-noise  and  contrast-to-oise  ratios  and  density  homogeneity,  the  latter  of  which  was5A.G.  Almeidased  in  this  case  to  distinguish  blood  flow  from  thrombus,ut  can  potentially  be  used  for  other  applications.The  diagnostic  accuracy  of  CCT  for  the  exclusion  ofhrombi,  amply  demonstrated  in  other  studies,  which  reportegative  predictive  values  of  over  99%  validated  by  TEE,6--8as  not  tested  in  this  study,  in  which  the  prevalence  ofhrombi  (in  a  low-risk  and  appropriately  anticoagulated  pop-lation)  was  extremely  low.  Even  so,  the  few  cases  in  whichhere  were  doubts  concerning  the  presence  of  thrombusnderwent  a  second  scan  without  additional  contrast  admin-stration  and  were  confirmed  by  TEE.  The  need  for  a  secondcan  was  less  frequent  in  the  group  assessed  using  the  third-eneration  scanner.The  optimized  protocols  were  shown  to  give  superioresults  to  those  in  other  published  studies  in  terms  of  radia-ion  and  contrast  dose,  without  sacrificing  diagnostic  quality.This  study  clearly  demonstrates  the  value  of  innovativedvances  in  technology  and  increasing  expertise  in  CCT,  notnly  as  applied  to  pre-AF  ablation  assessment,  but  withbvious  potential  for  the  study  of  other  cardiovascular  con-itions.These  developments,  which  will  undoubtedly  becometandard  practice  in  the  near  future,  open  up  novel  pos-ibilities  for  this  imaging  modality,  due  to  the  quality  andeliability  of  its  results,  together  with  marked  reductions  inadiation  doses.  Further  studies  will  be  needed  to  estab-ish  the  actual  cost/benefit  ratio  of  CCT,  balancing  itsigh  and  still  improving  diagnostic  quality  against  patientafety  concerns  and  cost,  but  we  can  predict  that  upcomingechnological  developments,  although  they  will  pose  newuestions  and  challenges,  are  also  bound  to  present  bothew  diagnostic  possibilities  and  reductions  in  exposure  toisk.onflicts of  interesthe  author  has  no  conflicts  of  interest  to  declare.eferences. Liddy S, Buckley U, Kok HK, et al. Applications of cardiac com-puted tomography in electrophysiology intervention. Eur Heart JCardiovasc Imaging. 2018;19:253--61.. Kalra MK, Sodickson AD, Mayo-Smith WW. CT radiation: keyconcepts for gentle and wise use. Radiographics. 2015;35:1706--21.. Einstein AJ. Radiation dose reduction in coronary CT angiogra-phy: time to buckle down. JACC Cardiovasc Imaging. 2015;8:897--9.. National Institute for Health and Clinical Excellence: Guidance.Chest pain of recent onset: assessment and diagnosis. Clinicalguideline [CG95]. Published date: March 2010, last updated:November 2016. https://www.nice.org.uk/guidance/cg95.. Marques H, Araújo Gonçalves P, Ferreira AM, et al. Cardiac com-puted tomography prior to atrial fibrillation ablation: effects oftechnological advances and protocol optimization. Rev Port Car-diol. 2018;37:873--83. --  a67diovasc Imaging. 2016;32:347--54.Cardiac  computed  tomography  for  atrial  fibrillation  ablation. Romero J, Husain SA, Kelesidis I, et al. Detection of leftatrial appendage thrombus by cardiac computed tomography inpatients with atrial fibrillation: a meta-analysis. Circ CardiovascImaging. 2013;6:185--94.. Lazoura O, Ismail TF, Pavitt C, et al. A low-dose, dual-phase car-diovascular CT protocol to assess left atrial appendage anatomy8 one-stop  shop?  887and exclude thrombus prior to left atrial intervention. Int J Car-. Wang L, Kadiyala M, Koss E, et al. CTA detection of left atrialstasis and thrombus in patients with atrial fibrillation. Pacing ClinElectrophysiol. 2016;39:1388--93.

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TC cardíaca na ablação da fibrilhação auricular - one-stop-shop?

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