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Dysfunctional but viable myocardium - ischemic heart disease assessed by magnetic resonance imaging and single photon emission computed tomography

Ugander, Martin LU (2005)
Abstract (Swedish)
Popular Abstract in Swedish

En hjärtinfarkt definieras som celldöd i hjärtmuskeln, och om celldöden är omfattande, orsakar den en oåterkallelig nedsättning i hjärtats pumpfunktion. Pumpfunktionen kan även vara långvarigt nedsatt p.g.a. att hjärtat inte får tillräckligt med blod. Man kan då förbättra pumpfunktionen genom att återställa blodtillförseln med en operation. För att kunna hitta områden i hjärtat med nedsatt funktion men levande hjärtmuskel ("dysfunctional but viable myocardium") är det nödvändigt att bedöma tre egenskaper: (1) hjärtats pumpfunktion, (2) dess genomblödning (perfusion) och (3) huruvida cellerna lever eller ej.



Delarbete I beskriver utvecklingen av en ny metod för att objektivt... (More)
Popular Abstract in Swedish

En hjärtinfarkt definieras som celldöd i hjärtmuskeln, och om celldöden är omfattande, orsakar den en oåterkallelig nedsättning i hjärtats pumpfunktion. Pumpfunktionen kan även vara långvarigt nedsatt p.g.a. att hjärtat inte får tillräckligt med blod. Man kan då förbättra pumpfunktionen genom att återställa blodtillförseln med en operation. För att kunna hitta områden i hjärtat med nedsatt funktion men levande hjärtmuskel ("dysfunctional but viable myocardium") är det nödvändigt att bedöma tre egenskaper: (1) hjärtats pumpfunktion, (2) dess genomblödning (perfusion) och (3) huruvida cellerna lever eller ej.



Delarbete I beskriver utvecklingen av en ny metod för att objektivt mäta dessa tre egenskaper med hjälp av funktionsbilder och infarktbilder från magnetisk resonanstomografi (MR) och bilder av perfusion från SPECT (en metod för att avbilda hjärtmuskelns genomblödning med en radioaktiv isotop som injiceras i blodet). Metoden implementerades och mätresultaten visade god överensstämmelse med visuell bedömning.



Delarbete II visar att pumpfunktionen i ett område beror mer på funktionen i omgivande hjärtmuskel än på utbredningen av infarkt i området. Delarbete III visar att hjärtats totala pumpfunktion varierar påtagligt i förhållande till den totala infarktstorleken, men att det föreligger en maximalt förväntad pumpfunktion i förhållande till infarktstorlek. Dessa arbeten visar att det varken går att påvisa eller utesluta förekomsten av infarkt genom att endast värdera pumpfunktionen.



Delarbete IV visar att även om perfusionen ökar tidigt efter en operation så kan funktionsåterhämtningen i levande hjärtmuskel vara fördröjd i områden i nära anslutning till infarkt. Detta ökar vår förståelse för återhämtningsförloppet efter en operation.



Varken regional eller total pumpfunktion korrelerar starkt till infarkt, men områden som delvis drabbats av infarkt uppvisar fördröjd funktionsåterhämtning efter operation. Sammanfattningsvis visar avhandlingen på vikten av att direkt avbilda infarkt med MR för att kunna bedöma möjligheten till funktionsåterhämtning i hjärtmuskel efter operation. (Less)
Abstract
The assessment of ischemic heart disease (IHD) often focuses on the detection of dysfunctional but viable myocardium which may improve in function following revascularization. Dysfunctional but viable myocardium is identified by distinct characteristics with regards to function, perfusion and viability. Therefore, in Paper I we developed a method for quantitative polar representation of left ventricular myocardial function, perfusion and viability using single photon emission computed tomography (SPECT) and cardiac magnetic resonance (CMR). Polar representation of these parameters was feasible, and the quantitative method agreed with visual assessment.



Paper II showed that wall thickening decreases with increasing... (More)
The assessment of ischemic heart disease (IHD) often focuses on the detection of dysfunctional but viable myocardium which may improve in function following revascularization. Dysfunctional but viable myocardium is identified by distinct characteristics with regards to function, perfusion and viability. Therefore, in Paper I we developed a method for quantitative polar representation of left ventricular myocardial function, perfusion and viability using single photon emission computed tomography (SPECT) and cardiac magnetic resonance (CMR). Polar representation of these parameters was feasible, and the quantitative method agreed with visual assessment.



Paper II showed that wall thickening decreases with increasing infarct transmurality. However, the variation in wall thickening was large, and importantly, influenced more so by the function of adjacent myocardium than by infarct transmurality. This underscores the difficulty of using resting function alone to accurately assess myocardial infarction in revascularized IHD.



In Paper III we assessed the relationship between left ventricular ejection fraction (LVEF) and infarct size and found that LVEF cannot be used to estimate infarct size, and vice versa. However, the study showed that LVEF can be used to estimate a maximum predicted infarct size, and that infarct size can be used to estimate a maximum predicted LVEF. These results emphasize the importance of direct infarct imaging by CMR when attempting to estimate the size of infarction in patients with IHD.



Paper IV was designed to assess the time course of recovery of myocardial perfusion and function after revascularization. The recovery of perfusion was found to occur in the first month, while the recovery of function was delayed in segments with non-transmural infarction.



In summary, the presented studies emphasize the importance of direct infarct imaging by CMR for the accurate identification of infarction in the assessment of dysfunctional myocardium. Neither regional nor global myocardial function have a close correlation to infarction, but the presence of non-transmural infarction is a marker for delayed recovery of function following revascularization. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • M.D., Professor Bonow, Robert O., Division of Cardiology, Northwestern University, Chicago, IL, USA
organization
publishing date
type
Thesis
publication status
published
subject
keywords
medicinsk instrumentering, tomografi, radiologi, medical instrumentation, Klinisk fysiologi, radiology, tomography, Clinical physics, non-invasive imaging, myocardial infarction, viability, Physiology, Fysiologi, Cardiovascular system, Kardiovaskulära systemet
pages
155 pages
publisher
Department of Clinical Physiology, Lund University
defense location
Segerfalksalen, Wallenberg Neuroscience Center, Sölvegatan 17, Lund, Sweden
defense date
2006-02-04 10:00
ISSN
1652-8220
ISBN
91-85439-84-3
language
English
LU publication?
yes
id
35ef5ea6-43b7-4069-a2cb-35f7c73a8d63 (old id 545445)
date added to LUP
2007-09-25 11:40:07
date last changed
2016-09-19 08:44:52
@phdthesis{35ef5ea6-43b7-4069-a2cb-35f7c73a8d63,
  abstract     = {The assessment of ischemic heart disease (IHD) often focuses on the detection of dysfunctional but viable myocardium which may improve in function following revascularization. Dysfunctional but viable myocardium is identified by distinct characteristics with regards to function, perfusion and viability. Therefore, in Paper I we developed a method for quantitative polar representation of left ventricular myocardial function, perfusion and viability using single photon emission computed tomography (SPECT) and cardiac magnetic resonance (CMR). Polar representation of these parameters was feasible, and the quantitative method agreed with visual assessment.<br/><br>
<br/><br>
Paper II showed that wall thickening decreases with increasing infarct transmurality. However, the variation in wall thickening was large, and importantly, influenced more so by the function of adjacent myocardium than by infarct transmurality. This underscores the difficulty of using resting function alone to accurately assess myocardial infarction in revascularized IHD.<br/><br>
<br/><br>
In Paper III we assessed the relationship between left ventricular ejection fraction (LVEF) and infarct size and found that LVEF cannot be used to estimate infarct size, and vice versa. However, the study showed that LVEF can be used to estimate a maximum predicted infarct size, and that infarct size can be used to estimate a maximum predicted LVEF. These results emphasize the importance of direct infarct imaging by CMR when attempting to estimate the size of infarction in patients with IHD.<br/><br>
<br/><br>
Paper IV was designed to assess the time course of recovery of myocardial perfusion and function after revascularization. The recovery of perfusion was found to occur in the first month, while the recovery of function was delayed in segments with non-transmural infarction.<br/><br>
<br/><br>
In summary, the presented studies emphasize the importance of direct infarct imaging by CMR for the accurate identification of infarction in the assessment of dysfunctional myocardium. Neither regional nor global myocardial function have a close correlation to infarction, but the presence of non-transmural infarction is a marker for delayed recovery of function following revascularization.},
  author       = {Ugander, Martin},
  isbn         = {91-85439-84-3},
  issn         = {1652-8220},
  keyword      = {medicinsk instrumentering,tomografi,radiologi,medical instrumentation,Klinisk fysiologi,radiology,tomography,Clinical physics,non-invasive imaging,myocardial infarction,viability,Physiology,Fysiologi,Cardiovascular system,Kardiovaskulära systemet},
  language     = {eng},
  pages        = {155},
  publisher    = {Department of Clinical Physiology, Lund University},
  school       = {Lund University},
  title        = {Dysfunctional but viable myocardium - ischemic heart disease assessed by magnetic resonance imaging and single photon emission computed tomography},
  year         = {2005},
}