MR-Signalverhalten des 4 Wochen alten okklusiven Myokardinfarktes im Tierexperiment

Zusammenfassung.

Ziel: Untersuchung des 4 Wochen alten okklusiven Myokardinfarktes in T₁- und T₂-gewichteten Aufnahmen nach Gd-DTPA im Vergleich zur Histologie. Material und Methoden: Bei 7 Schafen wurde nach Thorakotomie ein Ramus diagonalis ligiert und ein anterolateraler Infarkt induziert. Nach 4 Wochen erfolgte 15 min vor Entnahme des Herzens in 5 Tieren eine Injektion von 0,1 mmol Gd-DTPA/kg. Die in vitro MR-Bildgebung bei 1,5 T umfaßte T₁- und T₂-gewichtete Spin-Echo Aufnahmen. Regionale Myokarddicke und Signalintensität (SI) wurde in jeweils 36 Segmenten pro Kurzachsenschicht gemessen und mit der Histologie verglichen. Ergebnisse: Histologisch fand sich jeweils ein anterolateraler Infarkt, welcher mit der hyperintensen Region im T₁-Bild (195 von insgesamt 1296 Segmenten) nach Gd-DTPA übereinstimmte. Mit 122 Segmenten war die Ausdehnung von Gewebsanteilen mit erhöhter T₂-SI im Infarkt geringer. In diesen Regionen lag histologisch kapillarreiches Granulationsgewebe vor, während eine Erhöhung der T₁-SI nach Gd-Injektion ohne signifikante T₂-SI Erhöhung in bereits fibrotisch organisiertem Infarkt gefunden wurde. Insgesamt bestand bei erhöhter SI eine Abnahme der Wanddicke (3,8 ± 1,2 mm) gegenüber Regionen mit normaler SI (9,8 ± 1,1 mm, p < 0,001). Schlußfolgerung: Anhand von T₂- und T₁-Aufnahmen nach Gd-DTPA kann im Infarkt zwischen Granulations- und Bindegewebe differenziert werden.

MR Signal Behaviour of Four-Week-Old Occlusive Myocardial Infarctions in Sheep.

Purpose: To correlate signal behaviour in T₁- and T₂-weighted images after Gd-DTPA with regional histopathology in occlusive myocardial infarction (MI). Methods: Ligation of a diagonal branch of the LAD was performed in seven sheep. Four weeks later 0.1 mmol Gd-DTPA/kg were injected in five sheep 15 min before cardiac arrest and the sheep were slaughtered. In vitro imaging was performed at 1.5 T included T₁- and T₂-weighted spin echo sequences in long and short axis views. Signal intensities (SI) were determined in 36 myocardial segments per slice and compared to macro- and microscopy. Results: In all animals an antero-lateral infarct region was evident histologically. This region presented with increased T₂ SI and T₁ SI after Gd-DTPA. The number of segments with increased SI in T₁-weighted images was higher (n = 195 segments) compared to segments with increased T₂ SI (n = 122 segments). Granulation tissue could be differentiated from rarely vascularized connective tissue at a high level of significance (p < 0.001) by T₁ and T₂ SI analysis. Wall thickness was significantly decreased in necrotic myocardium (3.8 ± 1.2 mm) compared to normal tissue (9.8 ± 1.1 mm, p < 0.001). Conclusion: In four-week-old occlusive MI the extent of necrosis can be accurately assessed by analysis of post contrast T₁-weighted images. Considering regional T₂ SI, granulation tissue can be differentiated from regions with predominant fibrous organisation.

MR Tomographie - Myokardinfarkt - Gadolinium-DTPA

Magnetic Resonance Imaging - Myocardium, Infarction - Gadolinium-DTPA

Literatur

• 1 Karolle B L, Carlson R E, Aisen A M, Buda A J. Transmural distribution of myocardial edema by NMR relaxometry following myocardial ischemia and reperfusion.  Am Heart J. 1991;  122 655-664
• 2 McNamara M T, Tscholakoff D, Revel D, Soulen R, Schlechtmann N, Botvinick E, Higgins C B. Differentiation of reversible and irreversible myocardial injury by MR imaging with and without Gadolinium-DTPA.  Radiology. 1986;  158 765-769
• 3 Lima J AC, Judd R M, Bazille A, Schulman S P, Atalar E, Zerhouni E A. Regional heterogenity of human myocardial infarcts demonstrated by contrast-enhanced MRI-potential mechanisms.  Circulation. 1995;  92 1117-1125
• 4 Miller S, Huppert P E, Nägele T, Helber U, Brechtel K, Hoffmeister H M, Claussen C D. MR-tomographische Untersuchung myokardialer Funktion und Perfusion nach Myokardinfarkt.  Fortschr Röntgenstr. 1997;  167 399-405
• 5 de Roos A, van Rossum A C, van der Wall E E, Postema S, Doornbos J, Matheijssen N A, van Dijkman P RM, Visser F C, van Voorthuisen A E. Reperfused and nonreperfused myocardial infarction: Diagnostic potential of Gd-DTPA-enhanced MR imaging.  Radiology. 1989;  172 717-720
• 6 Sobel B E, Bresnahan G F, Shell W E, Yoder R D. Estimation of infarct size in man and its relation to prognosis.  Circulation. 1972;  46 640-648
• 7 The Multicenter Postinfarction Research Group . Risk stratification and survival after myocardial infarction.  N Engl J Med. 1983;  309 331-336
• 8 Dendale P, Franken P R, Block P, Pratikakis Y, de Roos A. Contrast enhanced and functional magnetic resonance imaging for the detection of viable myocardium after infarction.  Am Heart J. 1998;  135 875-880
• 9 Fishbein M C. Reperfusion injury.  Clin Cardiol. 1990;  13 213-217
• 10 Wesbey G E, Higgins C B, McNamara M T, Engelstad B L, Lipton M J, Sievers R, Ehman R L, Lovin J, Brasch R C. Effect of Gadolinium-DTPA on the magnetic relaxation times of normal and infarcted myocardium.  Radiology. 1984;  153 165-169
• 11 Kim R J, Chen E L, Lima J AC, Judd R M. Myocardial Gd-DTPA kinetics determine MRI contrast enhancement and reflect the extent and severity of myocardial injury after acute reperfused infarction.  Circulation. 1996;  94 3318-3326
• 12 Schmiedl A, Schnabel P A, Richter J. Cellular edema and alterations in metabolite content in the ischemic and reperfused canine heart following different forms of cardiac arrest.  Path Res Pract. 1996; 
• 13 Donahue K M, Weisskoff R M, Burstein D. Water diffusion and exchange as they influence contrast enhancement.  JMRI. 1997;  7 102-110
• 14 Lim T H, Lee D H, Kim Y H, Park S W, Park P H, Seo D M, Kim S T, Lee T K, Mun C W. Occlusive and reperfused myocardial infarction: Detection by using MR imaging with Gadolinium Polylysine enhancement.  Radiology. 1993;  189 765-768
• 15 Ovice M, Didier R, De Lorgeril M, Pichard J B, Dandis G, Delaye J, Renaud S, Amiel M. Quantitation of reperfused myocardial infarction by Gd-DOTA-enhanced magnetic resonance imaging.  Invest Radiol. 1991;  26 1065-1070
• 16 Yu K K, Saeed M, Wendland M F, Dae M W, Velasquez-Rocha S, Derugin N, Higgins C B. Comparison of T1-enhancing and magnetic susceptibility magnetic resonance contrast agents for demarcation of the jeopardy area in experimental myocardial infarction.  Invest Radiol. 1993;  28 1015-1023
• 17 Judd R M, Lugo-Olivieri C H, Masazumi A, Kondo T, Croisille P, Lima J AC, Mohan V, Becker L C, Zerhouni E A. Physiological basis of myocardial contrast enhancement in fast magnetic resonance images of 2-day-old reperfused canine infarcts.  Circulation. 1995;  92 1902-1910
• 18 Johnston D L, Gupta V K, Wendt R E, Mahmarian J J, Verani M S. Detection of viable myocardium in segments with fixed defects on Thallium-201 scintigraphy: Usefulness of magnetic resonance imaging early after acute myocardial infarction.  Magn Reson Imaging. 1993;  11 949-956
• 19 Rogers W J, Kramer C M, Geskin G, Hu Y-L, Theobald T M, Vido D A, Petroulo S, Reichek N. Early contrast enhanced MRI predicts late functional recovery after reperfused myocardial infarction.  Circulation. 1999;  99 744-750
• 20 Ramani K, Judd R M, Holly T A, Parrish T B, Rigolin V H, Parker M A, Callahan C, Fitzgerald S W, Bonow R O, Klocke F J. Contrast magnetic resonance imaging in the assessment of myocardial viability in patients with stable coronary artery disease and left ventricular dysfunction.  Circulation. 1998;  98 2687-2694
• 21 Higgins C B, Herfkens R, Lipton M J. Nuclear magnetic resonance imaging of acute myocardial infarction in dogs: Alterations in magnetic relaxation times.  Am J Cardiol. 1983;  52 184-188
• 22 Yuasa K, Kazuro S, Kawamitsu H, Tetsuya I, Toshio S, Yutaka I. Quantification of occlusive and reperfused myocardial infarct size with Gd-DTPA-enhanced MR imaging.  Eur J Radiol. 1993;  17 150-154
• 23 Krauss H, van der Wall E E, van der Laarse A, Doornbos J, de Roos A, Matheijssen N AA, van Dijkman P RM, van Voorthuisen A E, Bruschke A VG. Follow-up of regional myocardial T₂ relaxation times in patients with myocardial infarction evaluated with magnetic resonance imaging.  Eur J Radiol. 1990;  11 110-119
• 24 Garcia-Dorado D, Oliveras J, Gili J, Sanz E, Pérez-Villa F, Barrabés J, Carreras M J, Solares J, Soler-Soler J. Analysis of myocardial oedema by magnetic resonance imaging early after coronary artery occlusion with or without reperfusion.  Cardiovascular Research. 1993;  27 1462-1469
• 25 Saeed M, Wendland M F, Masui T, Higgins C B. Reperfused myocardial infarctions on T₁- and susceptibility-enhanced MRI: Evidence for loss of compartimentalization of contrast media.  Magn Reson Med. 1994;  31 31-39
• 26 Wu K C, Zerhouni E A, Judd R M, Lugo-Olivieri C H, Barouch L A, Schulman S P, Blumenthal R S, Lima J AC. Prognostic significance of microvascular obstruction by magnetic resonance imaging in patients with acute myocardial infarction.  Circulation. 1998;  97 765-772