Tetsuro Fudo

Relation of left ventricular perfusion and wall motion with metabolic activity in persistent defects on thallium-201 tomography in healed myocardial infarction

Myocardial viability in persistent thallium (TI)-201 defect is a controversial subject. To assess metabolic activity in segments with persistent defect, stress TI-201 tomography and positron emission tomography using nitrogen-13 ammonia and fluorine-18 2-fluoro-deoxyglucose (FDG) were performed in 28 patients with healed myocardial infarction. The segments with TI-201 perfusion defect in electrocardiogram-determined infarcted areas were selected for assessment. Stress perfusion defect was detected in 61 segments by TI-201 tomography. Twenty-two patients (36%) showed transient defects with redistribution (group 1) and 39 showed persistent defects (group 2). Increase in FDG uptake was observed in 95% in group 1. Among group 2 patients, 15 segments (38%) showed an increase in FDG uptake (group 2A) while the remaining 24 (62%) did not have an increased uptake (group 2B). The decrease in nitrogen-13 ammonia perfusion was more severe in group 2B (-23 +/- 7%) than in group 2A (-13 +/- 9%) (p less than 0.005) and group 1 (-10 +/- 4%) (p less than 0.001). In addition, wall motion scores tended to be lower in group 2B (0.21 +/- 0.71), compared with group 2A (0.67 +/- 0.70) (p = 0.05) and group 1 (0.77 +/- 0.60) (p less than 0.01). These data indicate that metabolic viability was observed in approximately 40% of the segments with persistent TI-201 defect. Preservation of regional perfusion and wall motion in these areas was similar to that in areas with transient TI-201 defect.

F-18 deoxyglucose and stress N-13 ammonia positron emission tomography in anterior wall healed myocardial infarction

To evaluate myocardial blood flow and glucose utilization, N-13 ammonia (NH3) and F-18 deoxyglucose positron emission tomography scanning was performed in 22 patients with previous anterior wall myocardial infarction, using a high-resolution, multi-slice, whole-body scanner. The N-13 ammonia study was performed at rest and after exercise. The F-18 deoxyglucose study was performed at rest after fasting greater than 5 hours. The N-13 ammonia study revealed a hypoperfused area in 19 of the 22 patients (86%), that corresponded to the infarcted regions as diagnosed by electrocardiography, coronary arteriography and left ventriculography (21 patients). The hypoperfused areas expanded after exercise in 16 of 22 patients (73%). F-18 deoxyglucose uptake was observed in these hypoperfused areas, especially in patients with hypokinetic wall motion on left ventriculography and in exercise-induced hypoperfused areas. However, positron emission tomography demonstrated diffuse uptake of F-18 deoxyglucose in 3 of 8 patients with dyskinetic wall motion. Thus, metabolically active myocardium in infarcted areas or periinfarct ischemia can be visualized with F-18 deoxyglucose and stress N-13 ammonia studies.

Non-Q wave versus Q wave myocardial infarction: regional myocardial metabolism and blood flow assessed by positron emission tomography

This study compared regional myocardial blood flow at rest and during supine exercise as well as regional myocardial glucose utilization in the fasting condition in 22 patients, 11 with antecedent non-Q wave and 11 with antecedent Q wave infarction. With use of N-13 (nitrogen-13) ammonia and F-18 (fluorine-18) deoxyglucose as tracers of blood flow and exogenous glucose utilization and positron emission tomography, hypoperfused areas were noted at rest and during exercise in all 11 patients (100%) with Q wave infarction. Among the 11 patients with non-Q wave infarction such areas were noted in only 5 (45%) at rest and in 8 (73%) during exercise. Furthermore, segmentally enhanced F-18 deoxyglucose uptake corresponding to the infarcted areas (identified electrocardiographically) was seen in 10 (91%) of the 11 patients with non-Q wave infarction but in only 4 (36%) of the 11 patients with Q wave infarction (p less than 0.01). In conclusion, segmental F-18 deoxyglucose uptake as a possible sign of myocardial viability was seen more frequently in non-Q wave than in Q wave infarction and, importantly, regionally enhanced F-18 deoxyglucose uptake occurred even in the absence of segmental rest or exercise blood flow abnormalities, or both, in 5 (45%) of 11 patients with non-Q wave infarction.

Significance of technetium-99m/thallium-201 overlap on simultaneous dual emission computed tomography in acute myocardial infarction.

To examine the significance of technetium-99m pyrophosphate/thallium-201 scintigraphic overlap as an indicator of identifying early coronary reperfusion (less than or equal to 3 hours), 32 patients, in whom coronary recanalization was attempted for acute myocardial infarction (AMI), underwent myocardial imaging 3 days after the onset of AMI. The imaging was performed by simultaneous dual emission computed tomography, which allows simultaneous recording of technetium-99m pyrophosphate and thallium-201 images and comparison between both images in the same slice. The patients were separated into 3 groups: 9 patients in whom reperfusion was successful and showed scintigraphic overlap (group A), 12 with successful recanalization but no overlap (group B) and 11 with neither coronary reflow nor overlap (group C). No patient in whom reperfusion failed showed scintigraphic overlap (p less than 0.05). Groups A and B were comparable in age, infarct vessel, collateral circulation, residual coronary stenosis and cumulative release of creatine kinase-MB isoenzyme. However, compared with group B, group A had a shorter interval between onset of AMi and reflow (2.5 +/- 0.8 vs 4.8 +/- 1.3 hours, p less than 0.001). The presence of scintigraphic overlap identified early coronary reflow with a sensitivity of 80%, specificity of 91%, positive predictive accuracy of 89% and negative predictive accuracy of 83%. Thus, technetium-99m/thallium-201 overlap on dual emission computed tomography can be used as an index of documenting early recanalization and might reflect the presence of salvaged myocardium adjacent to the necrotic tissue.

Early estimation of acute myocardial infarct size soon after coronary reperfusion using emission computed tomography with technetium-99m pyrophosphate

Early appearance of positive findings on a technetium-99m pyrophosphate scan has been shown to be associated with the presence of a reperfused acute myocardial infarction (AMI). Early technetium-99m pyrophosphate imaging was performed by emission computed tomography to evaluate reperfusion and to test the feasibility of estimating infarct size soon after coronary reperfusion based on acute positive tomographic findings. Twenty-seven patients with transmural AMI who were treated with intracoronary urokinase infusion followed by percutaneous transluminal coronary angioplasty underwent pyrophosphate imaging 8.7 +/- 2.1 hours after the onset of AMI. None of the 8 patients in whom reperfusion was unsuccessful had acute positive findings. Of 19 patients in whom reperfusion was successful, 17 had acute positive findings (p less than 0.001). In these 17, tomographic infarct volumes were determined from reconstructed transaxial images. The threshold for areas of increased pyrophosphate uptake within the infarct was set at 60% of peak activity by the computerized edge-detection algorithm. The total number of pixels in all transaxial sections showing increased tracer uptake were added and multiplied by a size factor and 1.05 g/cm3 muscle to determine infarct volume. The correlations of tomographic infarct volumes with peak serum creatine kinase (CK) levels (r = 0.82) and with cumulative release of CK-MB isoenzyme (r = 0.89) were good. Moreover, the time to positive imaging was significantly shorter than that to peak CK level (8.5 +/- 2.3 vs 10.4 +/- 2.2 hours, p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Increased fluorine-18 deoxyglucose uptake after percutaneous transluminal coronary angioplasty in recently infarcted myocardium.

Abstract Positron emission tomography (PET) allows the noninvasive assessment of relative myocardial perfusion and glucose utilization in humans. 1 Relative myocardial perfusion is assessed with nitrogen-13 ammonia and relative glucose utilization is assessed with the glucose analog fluorine-18 deoxyglucose. Using this technique, we will describe 2 patients whose infarcted areas revealed new fluorine-18 deoxyglucose uptake many weeks after successful percutaneous transluminal coronary angioplasty (PTCA).