PET "reversed mismatch pattern" early after acute myocardial infarction: follow-up of flow, metabolism and function
The aim of this study was to evaluate changes of flow, metabolism and left ventricular function in patients revealing a "reversed mismatch" pattern (reduced glucose uptake relative to perfusion) on positron emission tomography (PET) early after myocardial infarction. In 19 out of 68 patients (28%), prospectively included in the GUSTO-I or STAR studies, a PET reversed mismatch pattern in the infarct-related region was found. All patients received thrombolytic therapy within 3 h after onset of pain and coronary angiography 90 min later. 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG)/nitrogen-13-labelled ammonia (13NH3) PET was performed after 5 days and 3 months. In 12 of the 19 patients, functional recovery was investigated with two-dimensional echocardiography at the same time points. In the infarct-related region, normalized 13NH3 uptake was 76%±11% at 5 days and 85%±10% at 3 months (P<0.00001). Absolute blood flow in this region was 75±25 ml/min per 100 g at 5 days and 80±19 ml/min per 100 g at 3 months. At 5 days, normalized 18F-FDG uptake in the infarct-related region was decreased (51%±12%). At 3 months, 18F-FDG uptake in this region had significantly recovered (75%±11%, P<0.00001). In the infarct-related region, absolute FDG metabolism was 17±6 µmol/min per 100 g at 5 days and 26±9 µmol/min per 100 g at 3 months (P<0.0001). At 5 days, normalized 18F-FDG uptake was more severely decreased as compared to the normalized 13NH3 uptake (P<0.00001) in the infarct-related region, resulting in a reversed mismatch pattern (25%±13% of the left ventricle). At 3 months, 18F-FDG metabolism had partially recovered, giving rise to a change into a PET match pattern. Reversed mismatch regions were present in only 7%±7% of the left ventricle at that time. The ratio of 18F-FDG uptake to 13NH3 uptake in the infarct-related region increased from 0.67±0.8 at 5 days to 0.88±0.09 at 3 months (P<0.00001). No functional recovery was observed in the infarct-related region (the 5-day and 3-month wall motion scores were both 2.5±0.5). In patients with a myocardial infarction showing a PET reversed mismatch pattern 5 days after thrombolytic therapy, recovery of 18F-FDG uptake was found but no functional recovery was observed at 3-month follow-up.