Abstract 3099: Absolute Quantification of Rest Myocardial Blood Flow by Cardiac Magnetic Resonance can provide Improved Prediction of Functional Recovery in Patients with Acute Myocardial Infarction.
Background: Previous studies demonstrated that transmural extent of late gadolinium enhancement (LGE) within one week after acute myocardial infarction (MI) is 30 – 40% larger than that after 6 months, indicating that myocardial segments showing 50 –75% transmural extent of LGE early after MI onset may exhibit functional recovery. The purpose of this study was to evaluate if combined assessment of regional myocardial blood flow (MBF) and transmural extent of LGE can provide more accurate prediction of functional recovery as compared with LGE alone in patients with acute MI.
Methods: Thirty patients (66 +/− 12 years) within one week (4.4 +/− 2.2 days) after onset of MI underwent cine MRI, rest myocardial perfusion MRI and LGE MRI. Rest MBF in 16 LV myocardial segments was quantified from rest myocardial perfusion MRI, by using a model based perfusion quantification software. Dual bolus method was used to correct for nonlinearity of blood signal on perfusion MRI. Transmural extent of LGE was measured in the corresponding 16 myocardial segments. Cine MRI was obtained 6 months after onset of MI to evaluate recovery of systolic wall thickening.
Results: MI was observed on LGE MRI in 207 of 480 segments. The averaged MBF in acute state was 79.9 +/−41.7 ml/min/100g in the segments with functional recovery after 6 months, and was 43.3 +/−23.0 ml/min/100g in the segments without functional recovery (p<0.01). ROC analysis revealed that absolute quantification of rest MBF in patients with acute MI has high diagnostic accuracy for predicting functional recovery after 6 months (Az=0.80). By using a threshold MBF value of 35ml/min/100g, rest MBF measurement can identify 160 (95%) of 168 viable segments, while LGE MRI detects 141 (84%) of 168 viable segments. Thus, 19 (70%) of 27 segments that was incorrectly defined as nonviable by LGE MRI alone can be correctly diagnosed as viable by combining rest MBF quantification.
Conclusion: Quantitative assessment of MBF is an objective method that can substantially reduce underestimation of functional recovery when compared with LGE MRI alone in patients early after onset of MI.