Clinical value of thallium-201 reinjection after delayed imaging in patient showing incomplete or no redistribution

To asses clinical value of Tl-201 (Tl) reinjection after delayed imaging, 30 patients who showed incomplete or no redistribution in stress-delayed Tl myocardial scintigraphy were studied. Of 76 myocardial segments with incomplete or no redistribution on the delayed images, 29 segments (38%) showed improvement of Tl uptake after Tl reinjection. Reinjection was considered effective in 24 segments (32%) where no or little redistribution were observed on the delayed images but improved after reinjection. The contrast ventriculography showed less wall motion abnormality in the segments with improvement after reinjection than that without improvement after reinjection (regional wall motion score: 2.55 +/- 0.50 vs. 0.59 +/- 0.97 p less than 0.01). History of myocardial infarction was also significantly less in the former (p less than 0.05). We conclude that Tl reinjection is useful in cases showing no or equivocal redistribution on the delayed images.     

Assessment of myocardial viability by 24-hour imaging after stress thallium-201 scintigraphy]

Twenty-four-hour delayed imaging after stress thallium-201 scintigraphy was assessed for more accurate detection of viable myocardium. Thirty-two patients with coronary artery disease who showed fixed perfusion abnormality (FPA) at 3 hr imaging after stress Tl study were evaluated with 24 hr delayed imaging. Of 37 areas with FPA, 19 areas (51%) showed redistribution (RD) at 24 hr imaging. After successful coronary artery bypass grafting (n = 19) or transluminal coronary angioplasty (n = 3), stress Tl scintigraphy was performed. Of 13 areas with RD at 24 hr imaging, 12 revealed improvement of Tl uptake after revascularization. On the other hand, of 12 areas with FPA until 24 hr, 8 showed no improvement. In conclusion, conventional stress Tl-201 scintigraphy underestimates myocardial viability, and additional 24 hr imaging permits more accurate assessment of myocardial viability.     

Attenuation correction improves the detection of viable myocardium by thallium-201 cardiac tomography in patients with previous myocardial infarction and left ventricular dysfunction.

The aim of this study was to determine the influence of attenuation-corrected thallium-201 stress/redistribution/reinjection single-photon emission tomography (SPET) on the number of viable segments in patients with previous myocardial infarction and dysfunctional myocardium. Fifty-one patients with previous myocardial infarction and left ventricular dysfunction were included in the study. In all patients, 201Tl non-corrected (NC) and attenuation-corrected (AC) SPET was performed using a stress/redistribution/reinjection protocol followed by coronary angiography. A semiquantitative analysis was performed using polar maps for NC and AC stress, redistribution and reinjection short-axis and vertical long-axis (apex) slices. Severe (perfusion defect below 50%/maximal count rate: PD < 50), mild and moderate persistent defects for redistribution and reinjection were evaluated for both NC and AC studies. A total of 1581 segments were evaluated by semiquantitative segmental analysis for both NC and AC studies for each redistribution and reinjection map. In the redistribution maps, NC revealed a total of 352 segments and AC a total of 222 segments with impaired perfusion below 50% of the maximal count rate (PD < 50). The mean number of affected segments was 6.9 +/- 5.5 in the case of NC and 4.4 +/- 4.8 in the case of AC (P < 0.001). In the reinjection maps, NC revealed a total of 263 non-viable segments (PD < 50) and AC a total of 169 non-viable segments. The mean number of affected segments was 5.2 +/- 5.3 in the case of NC and 3.3 +/- 4.2 in the case of AC (P < 0.001). Recovery of function was better predicted by AC than by NC in 20% of patients in the follow-up group. Therefore, the use of attenuation correction influences the extent of viable segments by showing more viable segments in either redistribution or reinjection maps. 201Tl imaging without attenuation correction may underestimate the extent of tissue viability, which may contribute to the lower sensitivity compared to fluorine-18-fluorodeoxyglucose positron emission tomography, where attenuation correction is a routinely performed procedure.     

Significance of fill-in after thallium-201 reinjection following delayed imaging: comparison with regional wall motion and angiographic findings

To identify reversible defects, reinjection of a small amount of thallium-201 (201Tl) following 3-hr delayed imaging was performed in 60 patients with coronary artery disease who had perfusion abnormalities on their post-exercise 201Tl images. Thallium-201 uptake was visually scored and judged as normal (Group 1), reversible defect (Group II), new fill-in after reinjection (Group IIIa) and no fill-in even after reinjection (Group IIIb). New fill-in after reinjection was observed in 27 segments of the 85 segments (32%), showing persistent defect on the stress and delayed images. The wall motion in Group IIIa was worse than Group II but better than Group IIIb. Group IIIa showed Q-wave on ECG more often (69%) than Group II (27%) (p less than 0.01), but less often than Group IIIb (85%) (p less than 0.05). These data indicate that the reinjection 201Tl imaging often identifies new fill-in in the areas of no redistribution on the delayed images and it may hold promise for assessing tissue viability which the conventional imaging may underestimate.     

Twenty-four-hour Tl-201 delayed scan underestimates myocardial viability in patients with acute myocardial infarction after percutaneous transluminal coronary angioplasty

BACKGROUND: Myocardial viability in area at risk of acute myocardial infarction (AMI) after reperfusion therapy may be underestimated by the 24-hour images due to reverse redistribution (r-RD). METHODS: Subjects were 37 AMI patients in whom Tc-99m pyrophosphate (PYP)/Tl-201 dual-isotope SPECT was positive. The 24-hour delayed scan was performed with only a Tl window. One month later, follow up rest Tl SPECT was performed to evaluate myocardial viability. In early (at PYP/Tl-201 dual-isotope SPECT), 24-hour, and one month follow up Tl studies, Tl uptake in the area of AMI was scored into four grades: 3 as normal to 0 as severely reduced. The scores were evaluated. RESULTS: Among the 37 AMI lesions, there were 16 r-RD, 3 RD, 16 fixed defect (FD) and 2 normal (positive PYP and normal Tl). Mean Tl scores were early; 1.4 +/- 1.1, 24-hr; 0.9 +/- 0.9 and one month; 1.3 +/- 1.1. The 24-hour Tl score was lower than the early and one month Tl scores (p < 0.01). CONCLUSION: Reverse redistribution is frequently observed in an area at risk where PYP SPECT was positive. Nuclear medicine physicians should be aware of the existence of frequent r-RD in Tl scan to avoid the underestimation of myocardial viability in the acute phase after PTCA.     

The value and limitation of resting 201Tl reinjection after stress-redistribution imaging for the assessment of myocardial viability: comparison with wall motion improvement by revascularization]

Clinical value and limitation of resting reinjection of small dose of thallium (37 MBq) for the assessment of myocardial viability were evaluated. The results were compared with the degree of wall motion improvement by revascularization to infarcted myocardium supplied by chronic total vessels in 12 patients with old myocardial infarction. Thallium uptake was visually scored and judged as normal, reversible defect (Group 1), new fill in after reinjection (Group 2A), and no fill in even after reinjection (Group 2B). Among 53 segments with initial perfusion abnormality, 21 segments reverted to almost normal, while 32 segments remained abnormal on redistribution images. New fill in after reinjection was observed in 11 segments of 32 segments showing persisting defect on stress and delayed image (37%). Wall motion score index of Group 2A improved significantly higher than Group 2B (p less than 0.01) and almost equal to Group 1, suggesting the utility of reinjection for the assessment of tissue viability which may be underestimated by conventional imaging. But significant wall motion improvement (greater than or equal to 0.6 mean SD/chords) was observed in 6 segments (29%) of 21 segments showing neither redistribution nor fill in after reinjection. These data indicate that small dose of thallium reinjection may enhance detection of viable but jeopardized myocardium, although some underestimation of viability remained to be resolved.     

Value of thallium-201 early reinjection for assessment of myocardial viability

To assess the efficacy of early reinjection forpredicting post intervention improvement in thallium-201 (Tl) uptake and regional wall motion, we reinjected a small dose of Tl following post-stress imaging and obtained reinjection early images (10 min after early reinjection) and reinjection delayed images (3 hr afterwards) in 40 patients who were referred to us for revascularization (group I). Twenty-nine patients in group I also underwent conventional stress-redistribution Tl scintigraphy (group II). Conventional stress-redistribution Tl scintigraphy was repeated after intervention. Contrast left ventriculography was performed before and after intervention and changes in regional wall motion were assessed in 22 of 40 patients. In group I, the predictive value for improvement and no improvement (the accuracy) of reinjection early images in perfusion was 83%, while that of reinjection delayed images was 91%. Furthermore, the accuracy of reinjection early images in regional wall motion was 80%, while it was 91% for reinjection delayed images. In group II, the accuracy in perfusion was 78% and the value in regional wall motion was 70%. Both accuracy in perfusion and in regional wall motion obtained from reinjection delayed images were significantly higher than the values in group II (p < 0.05). These data suggest that early reinjection is useful for predicting postintervention thallium uptake and regional wall motion.     

Dual isotope myocardial scintigraphy (201thallium at rest/99 M technetium tetrofosmin with exercise) in the detection of reversible hypoperfusion

The dual-isotope technique (rest 201Tl and stress 99mTc-sestamibi) is useful to assess myocardial perfusion in coronary disease patients. 99mTc-labeled tetrofosmin is a radiopharmaceutical whose characteristics are similar to sestamibi. Thus, we decided to use it to detect reversible myocardial hypoperfusion in patients with a background of myocardial infarction and ischemia. A sequential dual-isotope scintigraphy (3 mCi rest 201Tl and 25 mCi stress 99mTc-tetrofosmin) with 24-hour 201Tl redistribution (RD) was performed in 20 patients with previously confirmed myocardial infarction and clinical and ergometric signs of ischemia. Each patient also underwent a stress-redistribution protocol with redistribution at 4 and 24 hours post injection with 201Tl scintigraphy within two weeks of the first study. The qualitative uptake analysis showed no significant differences in the number of myocardial segments with severe reduction of tracer uptake on stress that improved at rest or in RD images, even if 24-hour RD images were considered. The quantitative global uptake analysis showed a similar defect reversibility with both protocols; however if 24-hour RD images were considered the uptake improvement was significant only when compared with the rest 201Tl images in dual-isotope scintigraphy protocol (75+/-8% vs. 81+/-9% of peak activity, rest vs. 24-hour RD; p<0.01) and not when compared with the 4-hour RD in the 201Tl scintigraphy. On the other hand, when only the segments with severely reduced uptake (<50% of peak activity) were analyzed, the 24-hour RD improved myocardial uptake significantly (p<0.001 vs. rest and vs 4-hour RD) in both protocols. We conclude that a sequential dual-isotope rest 201Tl/stress 99mTc-tetrofosmin scintigraphy is comparable with stress-redistribution 201Tl scintigraphy to detect reversible myocardial hypoperfusion; however in both cases, the addition of 24-hour images increases its usefulness in severely hypoperfused segments, if the uptake of the radiopharmaceutic is quantified.     

Evaluation of I-123-BMIPP myocardial SPECT on the detection of ischemic heart disease by comparing with stress thallium-201 myocardial SPECT]

To evaluate the usefulness of I-123-BMIPP as a tracer of fatty acid metabolism in ischemic heart disease, we performed both rest BMIPP myocardial SPECT and stress thallium-201 (Tl) SPECT in 15 patients with prior myocardial infarction, and compared the segmental findings each other. The abnormality of BMIPP images was more intense than that of Tl redistribution images (Tl-RD) in more than 60% of the abnormal segments. The degree of myocardial uptake of BMIPP was more concordant with that of Tl stress scan (Tl-EX) than with that of Tl-RD. This agreement of the findings between BMIPP and Tl-EX was found more remarkably in the regions of incomplete Tl redistribution or in the collateralized regions. These results revealed that ischemia in the jeopardized regions was able to be detected even by rest BMIPP scan. Abnormal findings in BMIPP were observed in more than 95% of segments with persistent defects or incomplete redistribution in Tl, but observed in only 41 or 45% of segments with complete redistribution. Normal findings in BMIPP were observed in 94% of normal segments in Tl. From these results, we can speculate that abnormal regions in BMIPP may have necrotic or ischemic myocardial tissue and normal regions in BMIPP may not have necrotic tissue. These results suggest that I-123-BMIPP may be available to detect myocardial ischemia or infarction in the clinical study. Additionally, the difference in findings between the early images and the delayed images in rest BMIPP scan was observed with relatively high incidence (14% of regions and 73% of patients). More detailed analysis will be required to reveal the importance of this difference.     

Assessment of myocardial viability with 201Tl SPET and reinjection technique: a quantitative approach.

The definition of viable myocardium after an acute myocardial infarction (MI) is important as it will determine which therapeutic option will be best for the patient. In 201Tl scintigraphy it has been shown that late redistribution (8-24 h) or reinjection may help to identify viable myocardium which does not appear to reperfuse on the 4 h redistribution image. In a prospective study 20 patients with a persistent defect seen on both stress and redistribution images were imaged after reinjection of 201Tl. On visual analysis a total of 180 segments were studied, 85 were normal, 18 reperfused at redistribution and a further nine (in six patients) after reinjection. Bull's-eye analysis at stress demonstrated a mean defect size of 279 pixels, S.D. +/- 74. After redistribution, there was no significant change in mean defect size (227 +/- 96 pixels). At reinjection, there was a significant reduction in mean defect size (189 +/- 107 pixels) (P < 0.05, paired 't'-test). Quantification shows a significant reduction in defect size between stress and reinjection. The use of the 201Tl reinjection technique in patients with a fixed perfusion deficit on stress and redistribution images improves the detection of viable myocardium and is to be preferred to a method of redistribution analysis alone.     

Left ventricular systolic wall motion after exercise stress and myocardial perfusion in patients with ischemic heart disease--investigation by ECG gated myocardial tomography

To investigate regional left ventricular (LV) wall motion (WM) after recovery from myocardial ischemia, we performed ECG-gated myocardial perfusion tomography with 99mTc-MIBI (G-SPECT) in patients with ischemic heart disease (IHD). In addition, we compared the left ventricular (LV) systolic function obtained by G-SPECT at rest with that obtained by contrast left ventriculography (LVG). We performed G-SPECT at 30 minutes after exercise stress (Ex-30) and 3 hours after exercise (rest). LVWM and LV ejection fractions (EF) were analyzed by the QGS (quantitative gated SPECT) program. The LV was divided into 9 segments and regional WM (RWM) was analyzed quantitatively. In addition, myocardial perfusion was assessed quantitatively. In 64 patients with several different types of heart disease, EF obtained by G-SPECT correlated well with LVG-EF (r = 0.907, p < 0.001), and RWM of G-SPECT coincided well with that of LVG (kappa value 0.67, p < 0.01). Eighty patients with suspected IHD were divided according to Ex-Rest myocardial perfusion. In 83% of patients with Ex-induced perfusion abnormalities disappeared completely at rest, and in 58% of patients with Ex-induced abnormalities disappeared incompletely, RWM abnormalities which were observed at Ex-30 improved at rest and as did EF. In 79% of patients with a fixed defect (FD), RWM abnormalities and EF at Ex-30 did not differ with those at rest, but in 12% of the patients, the RWM abnormality of Ex-30 improved at rest. In most myocardial segments that had recovered from transient ischemia, RWM abnormalities persisted at least 30 minutes after Ex (stunning). In a small portion of the myocardial segments regarded as having myocardial necrosis because of a fixed perfusion abnormality, RWM abnormalities at Ex-30 improved at rest. These segments were supposed to contain viable myocardium. In conclusion, G-SPECT is a powerful method for clarifying the relation between the regional systolic function and myocardial perfusion.     

201Tl与13N-NH3、18F-FDG PET心肌显像判断存活心肌的对比研究

目的　比较再注射2 0 1T1心肌显像与联合应用13 N NH3 及18F 脱氧葡萄糖 (FDG)心肌PET显像判断存活心肌的临床价值。方法　 2 0例心肌梗死患者 ,行2 0 1T1SPECT负荷、再分布、再注射显像及13 N NH3 、18F FDGPET心肌显像。将左室分成 9个节段 ,以视觉评价法对放射性分布进行 4级评分。获得2 0 1T1SPECT再分布、再注射像及18F FDGPET显像的局部心肌摄取率 (%ID)。结果　PET判定为存活心肌的 48个节段中 ,45个节段 (93.8% ) 2 0 1T1再注射像也判定为存活心肌。在2 0 1T1再分布像示放射性分布严重低下的 2 4个节段 ,2 0 1T1再注射像与PET显像判定存活心肌的一致率为 87.5 % ,其中 37.5 %为存活心肌节段 ,5 0 %为无存活心肌节段。 2种显像方法的 %ID无明显差异 ,且呈显著正相关 (r=0 .72 2 )。结论　再注射2 0 1T1心肌显像判断存活心肌的准确性与PET心肌显像相似 ,有较大的临床应用价值。     

Incremental value of assessment of regional wall motion for detection of multivessel coronary artery disease in exercise (201)Tl gated myocardial perfusion imaging.

Assessment of reversible perfusion defects in exercise (201)Tl perfusion SPECT has low sensitivity and high specificity for detection of multivessel coronary artery disease (CAD). The goal of this study was to evaluate whether worsening of left ventricular regional wall motion assessed by an automated algorithm in exercise (201)Tl electrocardiography-gated SPECT had incremental diagnostic value over perfusion data for detection of multivessel CAD. METHODS: Two hundred one patients underwent exercise (201)Tl gated SPECT. Software that automatically analyzes left ventricular function was used to assess exercise and rest regional wall motion. Regional wall motion on initial images was compared with that on rest images, that is, delayed images for patients without reinjection images and reinjection images for patients with reinjection images. The left ventricle was divided into 9 segments, with individual segments assigned to 3 coronary territories. Worsening of wall motion was defined as worsening in any segment on initial images compared with rest images. RESULTS: Of 73 patients with multivessel CAD, 20 (27.4%) had reversible perfusion defects in multiple coronary territories, 26 (35.6%) exhibited worsening of regional wall motion in multiple territories, and 37 (50.7%) had reversible perfusion defects or worsening of regional wall motion in multiple territories. The sensitivity of the combination of reversible perfusion defect and worsening of regional wall motion was significantly higher than that of reversible perfusion defect alone for detection of multivessel CAD (50.7% vs. 27.4%, P < 0.05). The specificity of the combination of reversible perfusion defect and worsening of regional wall motion for detecting multivessel CAD did not differ from that of reversible perfusion defect alone and that of worsening of regional wall motion alone (94.5% vs. 99.2% and 97.7%, respectively, P = not statistically significant). CONCLUSION: Combined assessment of worsening of left ventricular regional wall motion by exercise and perfusion data in exercise (201)Tl gated myocardial SPECT was more sensitive, with acceptable specificity, than was assessment with perfusion data alone for detection of multivessel CAD.     

Usefulness of reinjection image for evaluating viable myocardium in the infarcted zone on exercise thallium-201 SPECT

Reinjection images were obtained in 23 patients with myocardial infarction by the additional injection of 37 MBq of thallium-201 after obtaining 4 hour delayed images on exercise thallium-201 SPECT (TSPECT). A redistribution index (RI) was derived of the changes in perfusion defects between immediate and 4 hour delayed images as well as immediate and reinjection images on polar bull's eye maps. The RI of reinjection images (46 +/- 27%) was significantly greater than that of 4 hour delayed images (26 +/- 26%) in patients with myocardial infarction (p less than 0.01). Significant redistribution after reinjection occurred in 4 of 9 patients (44%) without significant redistribution on 4 hour delayed images. Improvement in redistribution on reinjection images correlated significantly to the small extent of coronary artery disease and collateral development. The appearance of redistribution from 4 hour delayed imaging to reinjection imaging also might reflect the function of collateral development in the resting state in patients without significant redistribution on 4 hour delayed images. It has been demonstrated that underestimated viable myocardium on 4 hour delayed images in the infarcted zone can be better assessed on reinjection images. This reinjection technique is recommended in patients with no or partial redistribution on 4 hour delayed images.     

Metabolic activity in the areas of new fill-in after thallium-201 reinjection: comparison with positron emission tomography using fluorine-18-deoxyglucose

Reinjection of thallium-201 after recording the 3-hr delayed scan often demonstrates improvement in areas of persistent abnormalities. To determine the metabolic activity of these areas, the changes seen on stress/redistribution/reinjection thallium SPECT were compared with PET using fluorine-18-fluorodeoxyglucose (FDG) in 18 patients with coronary artery disease. Of 48 segments showing no redistribution on the delayed scan, the reinjection scan identified new fill-in in 20 segments (42%), all of which demonstrated FDG uptake. In contrast, only 7 of the 28 segments (25%) showing no fill-in after reinjection were PET viable (p less than 0.01). Eleven patients had coronary bypass graft surgery after the radionuclide study. The majority of the segments showing redistribution (87%) and new fill-in after reinjection (65%) improved in wall motion, whereas only eight segments (25%) without new fill-in improved after surgery. Of those without new fill-in, two segments showing PET ischemia improved in wall motion, whereas the remaining six segments showing PET scar did not improve after surgery. Thus, the segments showing new fill-in after reinjection are PET viable myocardium. However, reinjection thallium imaging still underestimates the extent of tissue viability compared to PET imaging.     

Property of electrocardiogram gated single photon emission tomography by 99mTc-methoxy isobutyl isonitrile]

99mTc-methoxy isobutyl isonitrile (MIBI) is a new developed myocardial perfusion imaging agent. Because this compound has higher photon energy than thallium (Tl), electrocardiogram gated single photon emission tomography (SPECT): end-diastolic (ED) and end-systolic (ES) short axis (SA) images could be taken. To investigate property of gated MIBI SPECT, MIBI myocardial scintigraphy, Tl scintigraphy (TMS) and analysis of left ventricular wall motion were performed in 6 patients with myocardial infarction. Left ventricle was divided into 8 segments. Perfusion defect (PD) was scored: "0" (normal), "1" (hypo-perfusion), "2" (defect). Wall motion abnormality (WMA) was also scored: "0" (normokinesis), "1" (hypo-kinesis), "2" (a-, dys-kinesis). Severity and extent of PD and WMA were calculated. Severity of WMA was 3.0 +/- 2.0 (M +/- SD), severity of PD was 3.3 +/- 1.7 in TMS, 3.7 +/- 1.3 in no-gated MIBI, 5.0 +/- 0.6 in ES-MIBI, 7.3 +/- 2.0 in ED-MIBI. Extent of WMA was 2.3 +/- 1.0. Extent of PD was 2.5 +/- 1.3 in TMS, 3.0 +/- 1.6 in no-gated MIBI, 3.5 +/- 0.8 in ES-MIBI, 4.8 +/- 1.0 in ED-MIBI. Compared with wall motion abnormality, severity and extent of PD in ED-MIBI was larger. From our data, it is concluded that perfusion defect in ED-MIBI was overestimated significantly. When we evaluate gated MIBI image, we must consider this property.     

Myocardial perfusion in patients with left bundle branch block and without coronary artery disease]

For the evaluation of myocardial perfusion in patients with left bundle branch block (LBBB), we performed exercise stress (Ex)-redistribution (RD) myocardial tomography with thallium-201 (201Tl) in 23 patients with LBBB and without coronary artery disease (CAD). Myocardial images in patients with LBBB were compared with those of 9 patients with CAD who showed Ex induced transient septal defect. Bull'-eye maps (201Tl distribution maps at Ex and RD and 201Tl washout rate [WOR] map) were made from myocardial tomograms. In 23 patients with LBBB, 15 patients (65%) developed myocardial perfusion abnormality. In 10 (67%) of these 15 patients, transient perfusion defect appeared in the entire septum (diffuse type). On the other hand in 5 patients (33%), localized fixed perfusion defect developed at the boundary between septum and anterior wall (focal type). In focal type, every patient had other disease such as hypertension, aortic stenosis or sick sinus syndrome. While in patients with diffuse type, other diseases were observed in 30% (p less than 0.05) and they were limited to hypertension or diabetes mellitus. These facts suggested that mechanisms of perfusion abnormalities might be different between these two groups. We compared the perfusion abnormality between LBBB diffuse type and CAD. The extent of the defects was not different between two groups. Although apex was included within the defect in 89% of CAD population, apical defect was observed in only 20% of diffuse type (p less than 0.05). Minimal 201Tl WOR and 201Tl uptake ratio of septum to lateral wall indicated that exercise induced septal defect was slighter in diffuse type than CAD.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prediction of improvement of regional left ventricular function after revascularization using different perfusion-metabolism criteria.

Increased myocardial uptake of 18F-fluorodeoxyglucose (FDG) in regions with perfusion defects (perfusion-FDG mismatch) has been shown to predict functional recovery after revascularization; conversely, a concordant decrease in perfusion and FDG uptake (perfusion-FDG match) represents scar tissue (varying from subendocardial to transmural scar) that will not improve in contractile function after revascularization. Several recent studies have used a mild reduction in perfusion or FDG uptake (or both) as an indicator of viable tissue. To our knowledge, this criterion has not been validated against functional outcome after revascularization. This study aimed to compare the predictive value for functional recovery of these different perfusion-metabolism criteria. METHODS: Forty-two patients referred for revascularization were studied with early resting 201Tl SPECT (to evaluate perfusion) and FDG SPECT. Contractile function was evaluated before and 3-4 mo after revascularization using two-dimensional echocardiography. Angiography was not repeated. RESULTS: Two hundred six dysfunctional segments were identified; functional recovery occurred in 71 segments. The 206 dysfunctional segments were divided into five groups: group I, segments (n = 37) with normal perfusion; group II, segments (n = 69) with a mild reduction in perfusion (> or =60% of normal 201Tl uptake) without increased FDG uptake (mild match); group III, segments (n = 29) with a mild reduction in perfusion and increased FDG uptake (mild mismatch); group IV, segments (n = 46) with a more severe reduction in perfusion (<60% of normal 201Tl uptake) without increased FDG uptake (severe match); and group V, segments (n = 25) with a 201Tl activity < 60% and increased FDG uptake (severe mismatch). The mean wall motion score improved significantly in groups I, III and V but not in groups II and IV. Improvement of function was observed in 76% of group I segments, in 69% of group III segments and in 68% of group V segments. In contrast, only 13% of group II segments and 7% of group IV segments improved after revascularization. CONCLUSION: The results indicate that normal perfusion and mismatch patterns (either mild or severe) are predictive of functional recovery, whereas match patterns (either mild or severe) are predictive of absence of recovery. Match patterns are likely to represent different degrees of scar tissue, ranging from subendocardial to transmural scars. To identify segments with a high likelihood of improvement of function after revascularization, integration of information on perfusion and FDG uptake appears mandatory.     

Improved detection of myocardial perfusion reversibility by rest-nitroglycerin Tc-99m-MIBI: Comparison with Tl-201 reinjection

BACKGROUND: The role of nitroglycerin (NTG) in Tc-99m-methoxyisobutil isonitrile (MIBI) studies to improve the assessment of myocardial viability in patients with coronary artery disease and its comparison with TI-201 reinjection has not yet been clarified. This study aimed to test whether sublingual administration of NTG could improve the capability of Tc-99m-MIBI to detect reversibility in exercise-induced perfusion defects and to compare it with the TI-201 stress-redistribution-reinjection protocol. METHODS AND RESULTS: Thirty-eight patients (33 men, 5 women; mean age 49.3 +/- 8.2 years with previous myocardial infarction [mean evolution 7.1 +/- 3.9 months]) underwent exercise, redistribution, and reinjection TI-201 imaging, as well as exercise, rest, and NTG MIBI myocardial scintigraphy (3-day protocol). A total of 494 myocardial segments were assessed by quantitative analysis. Of the 136 myocardial segments with fixed defects on exercise-rest sestamibi imaging, 109 (80%) did not change after NTG MIBI study, and 27 (20%) demonstrated enhanced uptake. In the 140 myocardial segments with fixed defects on exercise-redistribution thallium imaging, 112 (80%) did not improve after TI-201 reinjection study, and 28 (20%) showed increased activity. The observed agreement on reversibility detection between NTG MIBI and TI-201 reinjection, with the 210 segments with perfusion defects used for this analysis on both studies, was 78%, with a significant kappa = .56 +/- .07 SE. CONCLUSION: Our data suggest that the use of an NTG MIBI protocol results in an incremental improvement for detecting exercise-induced perfusion defect reversibility and achieves results similar to those from a TI-201 reinjection protocol.     

Value of linsidomin in assessing myocardial viability with thallium-201 SPECT.

Myocardial viability can be assessed with rest/24 h redistribution (201)Tl myocardial single photon emission computed tomography (SPECT). The intravenous injection of vasodilators induces an early redistribution of (201)Tl and shortens the total examination time. The aim of this study was to compare the images after injection of linsidomin with the 24 h images. We studied 51 consecutive patients (38 males, 13 females), aged 66+/-11 years, referred for assessment of myocardial viability after acute myocardial infarction. SPECT acquisition at rest (30 projections over 180 degrees, 30 s per projection) was performed 20 min after injection of (201)Tl. A second acquisition (same parameters) was performed 2 min after intravenous injection of linsidomin (2 mg). A delayed acquisition was performed on the following day (50 s per step). Myocardial perfusion at rest was normal in 111 of 255 segments. For the 144 other segments, 24 h images were similar to the images acquired after the injection of linsidomin in 94% of cases (136 of 144 segments). The 24 h images showed partial redistribution that was not present after linsidomin in only eight segments (6%). Injection of linsidomin after rest acquisition can provide a reliable and more rapid assessment of myocardial viability. This very simple protocol (rest/linsidomin (201)Tl myocardial SPECT) can be performed in less than 1 h.