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Acute Myocardial Infarction: The Relationship between Duration of Ischaemia and Infarct Size in Humans - Assessment by MRI and SPECT

Hedström, Erik LU (2005) In Lund University Faculty of Medicine Doctoral Dissertation Series 72.
Abstract (Swedish)
Popular Abstract in Swedish

En hjärtinfarkt, dvs död hjärtmuskel, uppstår då en del av hjärtats muskel inte blodförsörjs, exempelvis genom att en propp bildats i ett av hjärtats blodkärl. Detta tillstånd bör behandlas snarast möjligt för att rädda största möjliga del av hjärtmuskeln, eftersom en större infarkt innebär sämre pumpfunktion vilket ger patienten sämre prognos. Tidsförloppet för en hjärtinfarkts utveckling hos människa har inte klargjorts tidigare. Vi har nu visat att 20-40 % av det område som hotas att bli infarkt, blir det efter 2-3 timmar. Det är alltså av största vikt att behandla patienten inom de första timmarna efter det att proppen uppstått (studie IV).



För att möjliggöra studium av... (More)
Popular Abstract in Swedish

En hjärtinfarkt, dvs död hjärtmuskel, uppstår då en del av hjärtats muskel inte blodförsörjs, exempelvis genom att en propp bildats i ett av hjärtats blodkärl. Detta tillstånd bör behandlas snarast möjligt för att rädda största möjliga del av hjärtmuskeln, eftersom en större infarkt innebär sämre pumpfunktion vilket ger patienten sämre prognos. Tidsförloppet för en hjärtinfarkts utveckling hos människa har inte klargjorts tidigare. Vi har nu visat att 20-40 % av det område som hotas att bli infarkt, blir det efter 2-3 timmar. Det är alltså av största vikt att behandla patienten inom de första timmarna efter det att proppen uppstått (studie IV).



För att möjliggöra studium av infarktutveckling hos människa behövde vi säkerställa korrelationen mellan två olika metoder, nämligen SPECT (avbildning av hjärtmuskelns genomblödning med hjälp av radioaktiv isotop) och infarktmätning med magnetisk resonanstomografi (MR). Vi visade i studie I att mätningar med dessa två metoder ger jämförbara resultat.



Vid en hjärtinfarkt släpps skademarkörer ut i blodet och dessa mäts för att uppskatta hur stor infarkt som har uppkommit. För att säkerställa uppskattningen av infarktstorleken bör serieprover tas med täta intervall. Vi visade i studie II att man för patienter som behandlats med ballongvidgning kan ersätta serieprover med enstaka prover utan att det påverkar bedömningen av infarktstorlek. Detta kan ge besparingar i både tid och pengar.



För att studera hur de kontrastmedel som används vid infarktdiagnostik med MR fungerar, genomfördes i samarbete med Uppsala Universitet studie III. Denna studie visade att inget kontrastmedel kommer in i ett område som saknar blodförsörjning, något som tidigare inte varit helt klarlagt. Detta område kan dessutom misstolkas som infarkt. Fortsatta studier inom området är av värde för att öka förståelsen kring hur kontrastmedelförstärkt MR fungerar. (Less)
Abstract
The effect of duration of ischaemia on final infarct size is well established in animal studies, but not fully evaluated in humans. Delayed contrast-enhanced magnetic resonance imaging (DE-MRI) can be used to distinguish between viable and non-viable myocardium and thus to quantify infarct size. We therefore used DE-MRI to investigate how duration of ischaemia affects final infarct size normalized to myocardium at risk in humans (Paper IV). The results showed that 20-40 % of myocardium at risk was infarcted after 2-3 hours of occlusion, indicating that a major part of myocardium at risk may be salvaged if reperfusion is performed within the first few hours of occlusion.



In order to study infarct evolution in humans, we... (More)
The effect of duration of ischaemia on final infarct size is well established in animal studies, but not fully evaluated in humans. Delayed contrast-enhanced magnetic resonance imaging (DE-MRI) can be used to distinguish between viable and non-viable myocardium and thus to quantify infarct size. We therefore used DE-MRI to investigate how duration of ischaemia affects final infarct size normalized to myocardium at risk in humans (Paper IV). The results showed that 20-40 % of myocardium at risk was infarcted after 2-3 hours of occlusion, indicating that a major part of myocardium at risk may be salvaged if reperfusion is performed within the first few hours of occlusion.



In order to study infarct evolution in humans, we first investigated the correlation between perfusion defect size assessed by myocardial single photon emission computed tomography (SPECT) perfusion imaging with final infarct size by DE-MRI (Paper I), showing that measurements by the two methods do not differ much for revascularized myocardial infarction.



Biochemical markers of cardiac injury are used to estimate myocardial infarct size. The agreement between cumulative as well as peak values of biochemical markers and DE-MRI in patients with an occluded coronary artery was studied for Paper II.We showed that in order to estimate infarct size, serial measurements may be substituted by acquisitions at 3, 6, and 12 hours after reperfusion, saving both cost and time in the clinical setting.



Finally, experimental infarction in pig was studied in collaboration with Uppsala University in order to provide a basis for further investigations on how MR contrast agents distribute in perfused and non-perfused myocardium in humans (Paper III). This study showed that perfusion is needed for delivery of contrast agent, and that the non-perfused myocardium, despite absence of contrast agent in this region, appears bright when nulling the signal from viable perfused myocardium using inversion-recovery DE-MRI. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Dr Arai, Andrew, NIH
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Cardiovascular system, Fysiologi, Physiology, humans, cardiac troponin T, creatine kinase isoenzyme MB, delayed contrast-enhanced magnetic resonance imaging, single photon emission computed tomography, myocardial perfusion, myocardial infarct size, myocardium at risk, duration of ischaemia, Kardiovaskulära systemet
in
Lund University Faculty of Medicine Doctoral Dissertation Series
volume
72
pages
122 pages
publisher
Department of Clinical Physiology, Lund University
defense location
Föreläsningssal 1, Universitetssjukhuset i Lund
defense date
2005-10-01 09:00
ISSN
1652-8220
ISBN
91-85439-75-4
language
English
LU publication?
yes
id
81e99fbd-ddd5-48af-881d-80288d77b425 (old id 545358)
date added to LUP
2007-09-18 19:36:31
date last changed
2016-09-19 08:44:55
@phdthesis{81e99fbd-ddd5-48af-881d-80288d77b425,
  abstract     = {The effect of duration of ischaemia on final infarct size is well established in animal studies, but not fully evaluated in humans. Delayed contrast-enhanced magnetic resonance imaging (DE-MRI) can be used to distinguish between viable and non-viable myocardium and thus to quantify infarct size. We therefore used DE-MRI to investigate how duration of ischaemia affects final infarct size normalized to myocardium at risk in humans (Paper IV). The results showed that 20-40 % of myocardium at risk was infarcted after 2-3 hours of occlusion, indicating that a major part of myocardium at risk may be salvaged if reperfusion is performed within the first few hours of occlusion.<br/><br>
<br/><br>
In order to study infarct evolution in humans, we first investigated the correlation between perfusion defect size assessed by myocardial single photon emission computed tomography (SPECT) perfusion imaging with final infarct size by DE-MRI (Paper I), showing that measurements by the two methods do not differ much for revascularized myocardial infarction.<br/><br>
<br/><br>
Biochemical markers of cardiac injury are used to estimate myocardial infarct size. The agreement between cumulative as well as peak values of biochemical markers and DE-MRI in patients with an occluded coronary artery was studied for Paper II.We showed that in order to estimate infarct size, serial measurements may be substituted by acquisitions at 3, 6, and 12 hours after reperfusion, saving both cost and time in the clinical setting.<br/><br>
<br/><br>
Finally, experimental infarction in pig was studied in collaboration with Uppsala University in order to provide a basis for further investigations on how MR contrast agents distribute in perfused and non-perfused myocardium in humans (Paper III). This study showed that perfusion is needed for delivery of contrast agent, and that the non-perfused myocardium, despite absence of contrast agent in this region, appears bright when nulling the signal from viable perfused myocardium using inversion-recovery DE-MRI.},
  author       = {Hedström, Erik},
  isbn         = {91-85439-75-4},
  issn         = {1652-8220},
  keyword      = {Cardiovascular system,Fysiologi,Physiology,humans,cardiac troponin T,creatine kinase isoenzyme MB,delayed contrast-enhanced magnetic resonance imaging,single photon emission computed tomography,myocardial perfusion,myocardial infarct size,myocardium at risk,duration of ischaemia,Kardiovaskulära systemet},
  language     = {eng},
  pages        = {122},
  publisher    = {Department of Clinical Physiology, Lund University},
  school       = {Lund University},
  series       = {Lund University Faculty of Medicine Doctoral Dissertation Series},
  title        = {Acute Myocardial Infarction: The Relationship between Duration of Ischaemia and Infarct Size in Humans - Assessment by MRI and SPECT},
  volume       = {72},
  year         = {2005},
}