Jian Wang1, Bo Xiang2, Hung-yu Lin3, Hong-yu Liu4, Darren Freed5, Rakesh C Arora5, Gang-hong Tian2. 1. 1] Department of Vascular Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China [2] National Research Council, Winnipeg, Manitoba, Canada R3B 1Y6 [3] Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P5. 2. 1] National Research Council, Winnipeg, Manitoba, Canada R3B 1Y6 [2] Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P5. 3. National Research Council, Winnipeg, Manitoba, Canada R3B 1Y6. 4. Department of Cardiovascular Surgery, the First Affiliated Hospital, Harbin Medical University, Harbin 150001, China. 5. 1] National Research Council, Winnipeg, Manitoba, Canada R3B 1Y6 [2] Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P5 [3] Cardiac Science Program, Institute of Cardiovascular Science, St Boniface General Hospital, Winnipeg, Manitoba, Canada R2H 2A6.
Abstract
AIM: To investigate the relationship between the collateral circulation and contrast-enhanced MR signal change for myocardial infarction (MI) in pigs. METHODS: Pigs underwent permanent ligation of two diagonal branches of the left anterior descending artery. First-pass perfusion (FPP) MRI (for detecting myocardial perfusion abnormalities) and delayed enhancement (DE) MRI (for estimating myocardial infarction) using Gd-DTPA were performed at 2 h, 7 d and 4 weeks after the coronary occlusion. Myocardial blood flow (MBF) was evaluated using nonradioactive red-colored microspheres. Histological examination was performed to characterize the infarcts. RESULTS: Acute MI performed at 2 h afterwards was characterized by hypoenhancement in both FPP- and DE-MRI, with small and almost unchanged FPP-signal intensity (SI) and DE-SI due to negligible MBF. Subacute MI detected 7 d afterwards showed small but significantly increaseing FPP-SI, and was visible as a sluggish hyperenhancement in DE-MRI with considerably higher DE-SI compared to the normal myocardium; the MBF approached the half-normal value. Chronic MI detected at 4 weeks afterwards showed increasing FPP-SI comparable to the normal myocardium, and a rapid hyperenhancement in DE-MRI with even higher DE-SI; the MBF was close to the normal value. The MBF was correlated with FPP-SI (r=+0.94, P<0.01) and with the peak DE-SI (r=+0.92, P<0.01) at the three MI stages. Remodeled vessels were observed at intra-infarction and peri-infarction zones during the subacute and chronic periods. CONCLUSION: Progressive collateral recovery determines the characteristic profiles of contrast-enhanced MRI in acute, subacute and chronic myocardial infarction in pigs. The FPP- and DE-MRI signal profiles not only depend on the loss of tissue viability and enlarged interstitial space, but also on establishing a collateral circulation.
AIM: To investigate the relationship between the collateral circulation and contrast-enhanced MR signal change for myocardial infarction (MI) in pigs. METHODS:Pigs underwent permanent ligation of two diagonal branches of the left anterior descending artery. First-pass perfusion (FPP) MRI (for detecting myocardial perfusion abnormalities) and delayed enhancement (DE) MRI (for estimating myocardial infarction) using Gd-DTPA were performed at 2 h, 7 d and 4 weeks after the coronary occlusion. Myocardial blood flow (MBF) was evaluated using nonradioactive red-colored microspheres. Histological examination was performed to characterize the infarcts. RESULTS: Acute MI performed at 2 h afterwards was characterized by hypoenhancement in both FPP- and DE-MRI, with small and almost unchanged FPP-signal intensity (SI) and DE-SI due to negligible MBF. Subacute MI detected 7 d afterwards showed small but significantly increaseing FPP-SI, and was visible as a sluggish hyperenhancement in DE-MRI with considerably higher DE-SI compared to the normal myocardium; the MBF approached the half-normal value. Chronic MI detected at 4 weeks afterwards showed increasing FPP-SI comparable to the normal myocardium, and a rapid hyperenhancement in DE-MRI with even higher DE-SI; the MBF was close to the normal value. The MBF was correlated with FPP-SI (r=+0.94, P<0.01) and with the peak DE-SI (r=+0.92, P<0.01) at the three MI stages. Remodeled vessels were observed at intra-infarction and peri-infarction zones during the subacute and chronic periods. CONCLUSION: Progressive collateral recovery determines the characteristic profiles of contrast-enhanced MRI in acute, subacute and chronic myocardial infarction in pigs. The FPP- and DE-MRI signal profiles not only depend on the loss of tissue viability and enlarged interstitial space, but also on establishing a collateral circulation.
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