Myocardial infarct size after reperfusion therapy: Assessment with Gd-DTPA-enhanced MR imaging

In 21 patients with proved acute myocardial infarction, the size of the infarct was estimated with serial magnetic resonance (MR) imaging after intravenous injection of gadolinium diethylenetriaminepentaaceticacid (DTPA) (0.2 mmol per kilogram of body weight). Early reperfusion after thrombolytic therapy or percutaneous transluminal coronary angioplasty performed during the acute phase of infarction was documented with coronary angiography in nine patients (group 1). In 12 patients (group 2), no reperfusion was achieved (n = 5) or no thrombolytic therapy was given (n = 7). All group 2 patients were considered to have no reperfusion. Infarct sizes measured with MR imaging were significantly smaller in group 1 than in group 2 at 8 days ± 4 after infarct onset (8% ± 5% vs 15% ± 4%, respectively; P < .001). Serial MR images showed individual variations in infarct size, findings that may be clinically significant. Estimation of infarct size with Gd-DTPA-enhanced MR imaging is accurate in demonstrating the effect of successful reperfusion therapy on infarct size

Acute Myocardial Infarction: Comparison of T2‐Weighted and T1‐Weighted Gadolinium‐DTPA Enhanced MR Imaging

Magnetic resonance images were obtained from 32 patients with acute myocardial infarction, using a four‐echo technique (echo time (TE) = 30, 60, 90, and 120 ms) pre‐gadolinium(Gd)‐DTPA injection and a TE = 30 ms sequence pre‐ and post‐Gd‐DTPA. Intensity ratios of infarcted and normal myocardium were calculated, as were contrast‐to‐noise and signal‐to‐noise ratios. The four intensity ratios pre‐Gd‐DTPA were 1.20 ±0.15, 1.42 ± 0.22, 1.78 ± 0.38, and 1.99 ± 0.60 for TE = 30, 60, 90, and 120 ms, respectively, and 1.42 ± 0.19 post‐Gd‐DTPA (p = NS for post‐Gd‐DTPA vs TE = 60, p = 0.007 for TE = 90 vs TE = 120, p < 0.0001 for all other comparisons). The four contrast‐to‐noise ratios pre‐Gd‐DTPA were 1.69 ± 0.97, 2.69 ± 1.13, 3.17 ± 1.15, and 2.90 ± 1.09 for TE = 30, 60, 90, and 120 ms, respectively, and 2.71 ± 1.26 post‐Gd‐DTPA (p = NS for post‐Gd‐DTPA vs TE = 60, 90, and 120, p = NS for TE = 120 vs TE = 60 and 90, p< 0.01 for all other comparisons). The four signal‐to‐noise ratios pre‐Gd‐DTPA were 8.67 ± 1.47, 6.52 ± 0.76, 5.20 ± 0.64, 4.17 ± 0.53 for TE = 30, 60, 90, and 120 ms, respectively, and 9.17 ± 1.92 post‐Gd‐DTPA (p = 0.03 for post‐Gd‐DTPA vs TE = 30, p < 0.0001 for all other comparisons). In conclusion, the detectabilities of acute myocardial infarction were similar at TE = 60 ms and at Gd‐DTPA enhanced short‐TE MR imaging. However, image quality proved to be superior using the Gd‐DTPA enhanced short‐TE technique. © 1991 Academic Press, Inc

Gadolinium-enhanced magnetic resonance imaging in acute myocardial infarction

To evaluate the usefulness of the paramagnetic contrast agent Gadolinium-DTPA (diethylenetriaminepentaacetic acid) in Magnetic Resonance Imaging of acute myocardial infarction, we studied a total of 45 patients with a first acute myocardial infarction by ECG-gated magnetic resonance imaging before and after intravenous administration of 0.1 mmol/kg Gadolinium-DTPA. All patients received thrombolytic treatment by intravenous streptokinase. The magnetic resonance imaging studies were performed after a mean of 88 h (range 15-241) after the acute onset of acute myocardial infarction. Five patients without evidence of cardiac disease served as controls. Spin-echo measurements (TE 30 ms) were made using a Philips Gyroscan (0.5 Tesla) or a Teslacon II (0.6 Tesla). The 45 patients were divided into four groups of patients. In Group I (5 patients) Gadolinium-DTPA improved the detection of myocardial infarction by Gadolinium-DTPA. In Group II (20 patients) the magnetic resonance imaging procedure was repeated every 10 min for up to 40 min following administration of Gadolinium-DTPA. Optimal contrast enhancement was obtained 20-25 min after Gadolinium-DTPA. In Group III (27 patients) signal intensities were significantly higher in the patients who underwent the magnetic resonance imaging study more than 72 h (mean 120) after the acute event, suggesting increased accumulation of Gadolinium-DTPA in a more advanced stage of the infarction process. In Group IV (45 patients) Gadolinium-DTPA was administered in an attempt to distinguish between reperfused and nonreperfused myocardial areas after thrombolytic treatment for acute myocardial infarction. The signal intensities did not differ, but reperfused areas showed a more homogeneous aspect whereas nonreperfused areas were visualized as a more heterogeneous contrast enhancement. It is concluded that magnetic resonance imaging using the contrast agent Gadolinium-DTPA significantly improves the detection of infarcted myocardial areas and may be of particular value in patients with acute myocardial infarction who undergo reperfusion therapy

Follow-up of regional myocardial T2 relaxation times in patients with myocardial infarction evaluated with magnetic resonance imaging

Multi-echo spin-echo cardiac magnetic resonance imaging studies (echo times 30, 60, 90 and 120 ms) were performed in 19 patients with a 7-14-day (mean 10) old myocardial infarction and were repeated in 13 patients 4-7 months (mean 6) later. Also, 10 normal subjects were studied with magnetic resonance imaging. T2 relaxation times of certain left ventricular segments were calculated from the signal intensities at echo times of 30 and 90 ms. Compared to normal individuals, the mean T2 values on the early magnetic resonance images of the patients with inferior infarction showed significantly prolonged T2 times in the inferiorly localized segments, while on the follow-up magnetic resonance images the T2 times had almost returned to the normal range. Also the patients with anterior infarction showed significantly prolonged T2 times in the anteriorly localized segments on the early nuclear magnetic resonance images, but the T2 times remained prolonged at the follow-up magnetic resonance images. For every patient a myocardial damage score was determined, which was defined as the sum of the segmental T2 values in the patients minus the upper limit of normal T2 values obtained from the normal volunteers ( = mean normal + 2SD). The damage score on both the early and late magnetic resonance imaging study correlated well with infarct size determined by myocardial enzyme release. Only the patients with an inferior infarction showed a significant decrease in damage score at follow-up magnetic resonance imaging. It is concluded that the regional T2 relaxation times are increased in infarcted myocardial regions and may remain prolonged for at least up to 7 months after the acute event, particularly in patients with an anterior infarction. These findings demonstrate the clinical potential of T2-weighted magnetic resonance imaging studies for detecting myocardial infarction, and estimating infarct size for an extended period after acute myocardial infarction

Acute, subacute, and chronic myocardial infarction: Quantitative analysis of gadolinium-enhanced MR images

The value of gadolinium enhancement to enable detection of infarcted myocardium at T1-weighted magnetic resonance (MR) imaging was assessed in 84 patients after acute myocardial infarction (AMI). Five healthy subjects served as controls. All patients underwent MR imaging before and 20 minutes after administration of gadopentetate dimeglumine. Contrast enhancement of normal myocardium varied 7% ± 4 after administration of gadopentetate dimeglumine. Mean intensity ratio after gadolinium enhancement in group 1 (imaging less than 1 week after AMI), group 2 (imaging 1-3 weeks after AMI), and group 3 (imaging 3-6 weeks after AMI) was significantly higher than before gadolinium enhancement. In group 4 (imaging more than 6 weeks after AMI), no significant difference was observed. After gadolinium enhancement, the intensity ratio was abnormally increased in 82% of the MR examinations in group 1, in 62% of group 2, in 58% of group 3, and in 12% of group 4. Gadolinium enhancement improved visualization of myocardial infarction at MR imaging up to 6 weeks after onset of symptoms and had a maximal effect within 1 week after AMI

Magnetic resonance imaging of myocardial infarction: Correlation with enzymatic, angiographic, and radionuclide findings

Spin-echo cardiac magnetic resonance imaging studies were performed in 20 patients with a first 7-to 14-day-old (mean 10) myocardial infarction. The magnetic resonance imaging findings were compared with coronary angiography (14 patients), myocardial enzyme release (18 patients), radionuclide angiography (19 patients), and thallium-201 perfusion scintigraphy (19 patients). Regional T2 relaxation times determined from the signal intensities at echo times 30 msec and 90 msec were significantly prolonged in the infarcted areas. Based on abnormal T2 times for every patient, a regional and a total myocardial damage score was determined. The infarct-related artery was correctly identified in 93% of patients by magnetic resonance imaging, in 79% of patients by thallium-201 scintigraphy, and in 62% of patients by radionuclide angiography. The total damage score correlated well with enzymatic infarct size (r = 0.75, p < 0.001). The correlation between left ventricular end-systolic volume index determined by magnetic resonance imaging and by radionuclide angiography was r = 0.89 (p < 0.002). The left ventricular end-systolic volume index correlated significantly with enzymatic infarct size (r = 0.72, p < 0.001), total damage score (r = 0.68, p < 0.002), and radionuclide left ventricular ejection fraction (r = -0.68, p < 0.002). Correlations between the magnetic resonance damage score and the thallium-201 perfusion score were r = 0.60 (p < 0.01) for the exercise images, and r = 0.72 (p < 0.001) for the redistribution images. This study shows that spin-echo magnetic resonance imaging is quite comparable with the established noninvasive imaging modalities currently used in patients with acute myocardial infarction

Improved detection of acute myocardial infarction by magnetic resonance imaging using Gadolinium-DTPA

To assess the value of the paramagnetic contrast agent Gadolinium (Gd)-DTPA in Magnetic Resonance Imaging (MRI) of acute myocardial infarction (AMI), we studied 20 patients with a first AMI by ECG-gated MRI before and after intravenous administration of 0.15mmol/kg Gd-DTPA. The MRI studies were performed after a mean of 98 hours (range 15-241) after the acute onset of AMI. Spin-echo measurements (TE 30 msec) were made using a Philips Gyroscan (0.5 Tesla). After performing the baseline MRI scans, the MRI procedure was repeated every 10 minutes for up to 40 minutes following injection of Gd-DTPA. In 18 (90%) patients contrast enhancement in the infarcted myocardial areas was observed after Gd-DTPA. In these patients intensity versus region curves, derived from 9 to 11 adjacent myocardial regions of interest, showed increased signal intensities in the infarcted areas after administration of Gd-DTPA. The precontrast signal intensity ratio between infarcted and normal myocardium was 1.14±0.15 (mean±SD); the postcontrast ratios at 10 minutes were 1.41±0.21 (P <0.05), at 20 minutes 1.61±0.19 (P <0.01), at 30 minutes 1.43±0.20 (P < 0.05), and at 40 minutes 1.33±0.20 (P=NS). It is concluded that MRI using the contrast agent Gd-DTPA significantly improves the visualization and detection of infarcted myocardial areas in patients with AMI and that optimal contrast enhancement is obtained 20 minutes after administration of Gd-DTPA