Comparison of thallium-201 single-photon emission tomography after rest injection and fluorodeoxyglucose positron emission tomography for assessment of myocardial viability in patients with chronic coronary artery disease

This prospective study in 42 patients with chronic coronary artery disease and severe wall motion abnormalities (sWMA) on cineventriculography (24 patients with previous myocardial infarction; ejection fraction, 45%±13%) was designed to compare myocardial thallium-201 uptake after rest injection and normalized fluorodeoxyglucose (¹⁸FDG) uptake (after oral glucose load) for assessment of a rest ²⁰¹Tl protocol to evaluate myocardial viability. The left ventricle was divided into the supply territory of the left anterior descending coronary artery (LAD) and the lateral wall and posterior territory (inferior, posterior and posteroseptal segments) because of the high variability of left circumflex and right coronary artery supply territories. Segmental ²⁰¹Tl uptake in single-photon emission tomography (SPET) and segmental normalized ¹⁸FDG uptake (13 segments per patient) showed a close linear relationship in the LAD territory (r=0.79) and in the lateral wall (r=0.77), while the correlation in the posterior territory was considerably lower (r=0.52). ²⁰¹Tl/¹⁸FDG concordance was defined as an ¹⁸FDG uptake exceeding ²⁰¹Tl uptake by < 20%. Discordance was assumed if ¹⁸FDG exceeded ²⁰¹Tl uptake by at least 20%. Concordant results were shown by 81% (439/541) of segments. In segments with severe ²⁰¹Tl reduction ( 50% of peak, n=78) discordance was observed in 10% of segments in the LAD territory and lateral wall (n=62) and in 44% of segments in the posterior territory (n=16). In segments with moderate ²⁰¹Tl reduction (51%–75%, n=205) discordance occured in 12% (LAD and lateral wall, n=126) or 46% (posterior territory, n=79) of segments, respectively. Severe defects were defined as the entire area with ²⁰¹Tl uptake 50% within a defined territory. Discordance was observed in 6/43 (14%) of these. Of 90 areas with sWMA on cineventriculography, 12 showed discordant results. Ten of these 12 discordant areas affected septum or posterior wall. In areas with normal wall motion or only mild hypokinesis, discordance occured in the septum or posterior wall in 22% whereas the figure for the anterior or lateral wall was only 2%. These results point to a significant role of photon attenuation in ²⁰¹Tl SPET imaging in the septum and posterior wall. It is concluded that ²⁰¹Tl SPET using a rest protocol identifies viable myocardium in the supply area of the LAD and in the lateral wall with high accuracy compared to ¹⁸FDG positron emission tomography while disordance in the posterior territory may be governed by photon attenuation in the SPET study rather than by a pathophysiological difference. Correspondence to: C. Aftehoefer     

Effects of physical stress and pharmacologically induced coronary dilation on myocardial and non-myocardial 201Thallium-uptake

After subtraction of the ²⁰¹Tl background radioactivity which was obtained from the paracardiac region, left ventricular (LV)-²⁰¹Tl net uptake at rest correlated with (1) the LV-muscle mass and therefore with (2) the LV-oxygen consumption. In normal LV, after maximum coronary dilation with dipyridamole, LV-²⁰¹Tl net uptake increased little more than LV-oxygen consumption but by factor of 2.27 less than was coronary vascular reserve. In coronary heart disease (c.h.d.), dipyridamole caused a significantly smaller increase of LV-²⁰¹Tl uptake (factor 1.16) than in normal LV myocardium (factor 1.76). This correlated well with the severity of the disease. Therefore, in maximum coronary dilation passive transport mechanisms may be responsible for augmented uptake and changed LV distribution of ²⁰¹Tl which depends on the perfusion pattern. In exercise, the ²⁰¹Tl-background radioactivity decreased from 54% (at rest) to 35% in normal patients and to 44% in c.h.d. Stressed thigh muscles accumulated ²⁰¹Tl 4.72-fold more than at rest. Therefore, it is still questionable if the myocardium during exercise receives enough ²⁰¹Tl to be labelled maximum. Since the LV-²⁰¹Tl count rates in c.h.d., measured over the maximum uptake area were increased to the same amount as in normal myocardium neither in coronary dilation nor during exercise, the validity of using the maximum LV-²⁰¹Tl uptake as a reference for the minimum one under these conditions is problematic.     

Cardiac phase-synchronized myocardial thallium-201 single-photon emission tomography using list mode data acquisition and iterative tomographic reconstruction

The purpose of this study was to determine whether data acquisition in the list mode and iterative tomographic reconstruction would render feasible cardiac phase-synchronized thallium-201 single-photon emission tomography (SPET) of the myocardium under routine conditions without modifications in tracer dose, acquisition time, or number of steps of the a gamma camera. Seventy non-selected patients underwent²⁰¹Tl SPET imaging according to a routine protocol (74 MBq/2 mCi²⁰¹Tl, 180° rotation of the gamma camera, 32 steps, 30 min). Gamma camera data, ECG, and a time signal were recorded in list mode. The cardiac cycle was divided into eight phases, the end-diastolic phase encompassing the QRS complex, and the end-systolic phase the T wave. Both phase- and non-phase-synchronized tomograms based on the same list mode data were reconstructed iteratively. Phase-synchronized and non-synchronized images were compared. Patients were divided into two groups depending on whether or not coronary artery disease had been definitely diagnosed prior to SPET imaging. The numbers of patients in both groups demonstrating defects visible on the phase-synchronized but not on the non-synchronized images were compared. It was found that both postexercise and redistribution phase tomograms were suited for interpretation. The changes from end-diastolic to end-systolic images allowed a comparative assessment of regional wall motility and tracer uptake. End-diastolic tomograms provided the best definition of defects. Additional defects not apparent on non-synchronized images were visible in 40 patients, six of whom did not show any defect on the non-synchronized images. Of 42 patients in whom coronary artery disease had been definitely diagnosed, 19 had additional defects not visible on the non-synchronized images, in comparison to 21 of 28 in whom coronary artery disease was suspected (P<0.02; ²). It is concluded that cardiac phase-synchronized²⁰¹Tl SPET of the myocardium was made feasible by list mode data acquisition and iterative reconstruction. The additional findings on the phase-synchronized tomograms, not visible on the non-synchronized ones, represented genuine defects. Cardiac phase-synchronized²⁰¹Tl SPET is advantageous in allowing simultaneous assessment of regional wall motion and tracer uptake, and in visualizing smaller defects.     

Thallium-201 right lung/heart ratio during exercise in patients with coronary artery disease: relation to thallium-201 myocardial single-photon emission tomography, rest and exercise left ventricular function and coronary angiography

The aim of this study was to correlate lung thallium-201 uptake on exercise with ²⁰¹Tl single-photon emission tomography (SPET) myocardial perfusion imaging, rest and exercise equilibrium radionuclide angiographic and coronary angiographic findings in patients with coronary artery disease (CAD) using a simple, reproducible lung/heart (L/H) ratio that would be easy to use in clinical practice. L/H ratio was defined on the anterior planar image obtained during exercise ²⁰¹Tl SPET acquisition as the mean counts per pixel in an entire right lung field region of interest divided by the mean counts per pixel in the hottest myocardial wall region of interest. We studied 103 patients. Fifty-nine patients (group I) with <5% likelihood of CAD were used as a reference group. In 44 CAD patients (group II), L/H ratio was compared with ²⁰¹Tl SPET, radionuclide angiographic and coronary angiographic variables. The group I L/H ratio of 0.35±0.05 (mean ±1 SD) was significantly lower (P<0.001) than the group II L/H ratio of 0.45±0.10. An L/H ratio >0.45 (mean + 2 SD in group I) was considered abnormal. In group II, L/H ratio showed a significant correlation with stress and rest ²⁰¹Tl perfusion defect size (r = 0.39 and r = 0.42, P<0.01, respectively), but not with extent of ischaemic myocardium. The mean L/H ratio was 0.41±0.10 in patients with one-vessel disease (n = 15), 0.46±0.08 in those with two-vessel disease (n = 17) and 0.47±0.12 in those with three-vessel disease (n = 12), but no significant difference was found between the three subgroups. L/H ratio showed a significant inverse relation with rest and exercise left ventricular ejection fraction (r = –0.37 and r = –0.50, P<0.05 and P<0.001, respectively). Using stepwise multiple regression analysis, exercise left ventricular ejection fraction and previous history of hypertension were the sole two variables independently predictive of the L/H ratio. In conclusion, although lung thallium uptake is usually found to correlate with extent and severity of CAD, increased L/H ratio should primarily be considered as a marker of exercise-induced left ventricular systolic and perhaps diastolic dysfunction, probably independent of the underlying cardiac disease. Received 14 January and in revised form 22 February 1999     

Left ventricular dysfunction in coronary artery disease: Comparison between rest-redistribution thallium 201 and resting technetium 99m methoxyisobutyl isonitrile cardiac imaging

Background

We compared rest-redistribution thallium 201 and resting technetium 99m methoxyisobutyl isonitrile (MIBI) cardiac imaging in 29 men with angiographically proven coronary artery disease and regional ventricular dysfunction. Left ventricular ejection fraction at radionuclide angiography was 35%±9%.

Methods and Results

Regional left ventricular wall motion was assessed on gated^99mTc MIBI images according to a 3-point scale (0=normal, 1=hypokinetic, 2=akinetic or dyskinetic).²⁰¹Tl and^99mTc MIBI uptake values were analyzed quantitatively. A total of 435 myocardial segments were classified on the basis of wall motion analysis into three groups: group 1 (normal wall motion;n=201), group 2 (hypokinetic;n=132), and group 3 (akinetic or dyskinetic;n=102).²⁰¹Tl and^99mTc MIBI uptake values were significantly higher in groups 1 and 2 compared with group 3 (p<0.05) and in group 1 compared with group 2 (p<0.05). When²⁰¹Tl and^99mTc MIBI uptake values were directly compared, no significant differences in groups 1 and 2 were observed. In group 3,^99mTc MIBI uptake (67%±14%) was significantly lower (p<0.001) than initial (72%±11%) and delayed²⁰¹Tl uptake (73%±12%).

Conclusion

Thus rest-redistribution²⁰¹Tl and resting^99mTc MIBI cardiac imaging reflect the severity of left ventricular dysfunction in coronary artery disease. However, in segments with severely impaired regional ventricular function,²⁰¹Tl uptake is significantly higher than^99mTc MIBI uptake.     

Feasibility of myocardial dual-isotope perfusion imaging combined with gated single photon emission tomography for assessing coronary artery disease.

The clinical feasibility of both dual-isotope single photon emission tomography (SPET) and gated SPET have been described. The present study evaluates the feasibility of combining gated SPET with exercise 201Tl/rest 99mTc-tetrofosmin dual-isotope SPET corrected for scatter. Ninety-one patients with known or suspected coronary artery disease underwent cardiac catheterization and coronary angiography. Twenty-nine of them underwent exercise 201Tl/rest 99mTc-tetrofosmin dual-isotope SPET with a second 201Tl injection 3 h after the initial 201Tl injection (protocol 1). We then segregated a Bull's eye polar map into three coronary artery territories and quantified the relative regional uptake. The remaining 62 patients underwent exercise 201Tl/rest 99mTc-tetrofosmin dual-isotope SPET combined with gated SPET. We visually evaluated exercise and rest images from the three coronary artery territories. Left ventricular (LV) function was assessed globally by means of the LV ejection fraction and regionally by means of visual scoring analysis, compared with left ventriculography (LVG). The correlation between rest 99mTc-tetrofosmin and 201Tl reinjection images in 87 areas of coronary artery territory (r=0.89, P<0.01) and in 13 infarcted areas (r =0.94, P<0.01) was very close in protocol 1. The overall values for vessel-related sensitivity, specificity and accuracy were 88%, 79% and 82%, respectively, in protocol 2. The correlation between gated SPET and LVG was significant and linear with respect to the LV ejection fraction (r=0.77, P<0.01). The wall motion score from visual evaluation in gated SPET revealed a close overall agreement with LVG (concordance rate, 88%; kappa, 0.670). Exercise 201Tl/rest 99mTc-tetrofosmin dual-isotope SPET with scatter correction for assessing the coronary artery disease offers excellent diagnostic accuracy and the additional gated SPET provides useful information about LV function similar to that for LVG. This sequential protocol requires only 2 h to generate much useful clinical information.     

Prediction of left ventricular dilatation with thallium-201 SPET imaging after primary angioplasty in patients with acute myocardial infarction

Progressive ventricular dilatation is an important prognostic factor in patients with acute myocardial infarction. We evaluated clinical, angiographic, echocardiographic and thallium-201 single-photon emission tomography (SPET) imaging variables predictive of the change in left ventricular volume during a 7-month follow-up period after primary angioplasty in patients with acute myocardial infarction. Thirty-six patients with first acute myocardial infarction treated with primary angioplasty within 12 h of onset underwent 201Tl SPET imaging (5.8+/-2.1 days after angioplasty). Changes in left ventricular volume were assessed over the 7-month period. The left ventricle dilated significantly after angioplasty ( P<0.001). Multivariate analysis revealed that the number of segments with 201Tl uptake <40% of peak activity was a single independent predictor of increase in end-diastolic volume index between 1 week and 7 months ( R2=0.41, P< 0.001). The presence of two or more segments with 201Tl uptake <40% predicted an increase in end-diastolic volume index of > or =6 ml/m2 with positive and negative predictive values of 85% (17/20) and 75% (12/16), respectively. It is concluded that, following primary angioplasty in patients with acute myocardial infarction, the extent of myocardial infarction assessed by 201Tl SPET can identify those who will develop ventricular dilatation during the subsequent 7 months.     

Lung uptake of technetium 99m sestamibi: Relation to clinical,exercise, hemodynamic,and left ventricular function variables

Background

Technetium 99m sestamibi (2-methoxyisobutyl isonitrile [MIBI]) is a relatively new radiopharmaceutical with improved imaging characteristics for exercise myocardial perfusion studies compared with thallium 201. Although increased lung uptake of²⁰¹Tl has been shown to have important clinical significance, reflecting severity of coronary artery disease and left ventricular function, the factors affecting MIBI lung uptake are unknown. Therefore we examined the potential clinical, exercise, hemodynamic, myocardial perfusion, and ventricular function determinants of lung uptake of MIBI on exercise myocardial perfusion studies.

Methods and Results

The study cohort consisted of 103 patients referred for evaluation of coronary artery disease with exercise MIBI myocardial perfusion imaging. All patients underwent both a standard 1-day rest-stress MIBI planar imaging protocol and rest echocardiography. With the anterior-view stress images obtained 1 hour after MIBI injection, regions of interest were drawn over peak lung and myocardial activities and a lung/heart ratio was calculated. Multivariate regression analysis was used to relate the lung/heart ratio to clinical, exercise and hemodynamic, myocardial perfusion, and echocardiographic left ventricular function scores. We found no significant relation between lung/heart ratio and any patient variable.

Conclusions

Unlike²⁰¹Tl, lung uptake of MIBI is not related to indexes of exercise, left ventricular dysfunction, or perfusion abnormalities. Thus MIBI lung uptake does not appear to have the same clinical significance as²⁰¹Tl lung uptake.     

Stress induced right ventricular dysfunction: An indication of reversible right ventricular ischaemia

Stress induced changes in left ventricular ejection fraction are widely used in the detection and assessment of coronary artery disease. This study demonstrates that right ventricular dysfunction may also occur, and assesses its significance in terms of coronary artery anatomy. This study involved 14 normal subjects and 26 with coronary artery disease investigated by equilibrium radionuclide ventriculography, at rest and during maximal dynamic exercise. Mean normal resting right ventricular ejection fraction (RVEF) was 0.40 (SD 0.118), and all normal subjects increased RVEF with stress (mean RVEF+0.13 SD 0.099). Mean RVEF in the subjects with coronary artery disease was significantly lower at 0.00 (SD 0.080), but there was overlap between the two groups. The largest falls in RVEF were seen if the right coronary artery was occluded without retrograde filling. In this subgroup with the most severely compromised right ventricular perfusion (nine subjects), RVEF always fell with stress, and mean RVEF was-0.08 (SD 0.050). There was no significant correlation between LVEF and RVEF, implying that the right ventricular dysfunction was due to right ventricular ischaemia, rather than secondary to left ventricular dysfunction. Stress induced right ventricular ischaemia can therefore be detected readily by radionuclide ventriculography.     

Recovery of impaired left ventricular function in patients with acute myocardial infarction is predicted by the discordance in defect size on123I-BMIPP and201TI SPET images

A discrepancy between myocardial perfusion defect and wall motion abnormalities is frequently found early after coronary reperfusion in patients with acute myocardial infarction. The purpose of this study was to assess recovery of impaired left ventricular function by reference to the discordance in defect size between myocardial fatty acid uptake and myocardial perfusion using combined single-photon emission tomographic (SPET) imaging early after coronary perfusion therapy. In 37 patients with acute myocardial infarction, iodine-123 15(p-iodophenyl)-3(R, S)-methylpentadecanoic acid (BMIPP) and thallium-201 SPET scans were performed early after coronary reperfusion. A severity score was determined from the extent of the imaging defect with each tracer. Left ventricular wall motion score (WMS) and ejection fraction (EF) were obtained at admission and at 4 weeks after the onset of infarction. In 32 of the 37 patients, discordance in defect sizes delineated with the two SPET studies was found during the acute stage. The severity score for BMIPP was larger than that for²⁰¹Tl during the acute stage (7.7±2.4 vs 4.4±2.5,P <0.001). There was a fair correlation between the severity score for BMIPP and WMS (r=0.82,P <0.0001), but a poor correlation between that for²⁰¹Tl and WMS. The extent of discordance in severity scores between BMIPP and²⁰¹Tl during the acute stage correlated well with the extent of the improvement in WMS (r=0.86,P <0.0001) and that of EF (r=0.85,P <0.0001). We conclude that the discordance in defect size on BMIPP and²⁰¹TI SPET images during the acute stage of infarction is an early predictor of the viability of the myocardium at risk of infarction.     

A comparison of resting images from two myocardial perfusion tracers

We have compared stress-redistribution and delayed rest thallium-201 with rest technetium-99m methoxyisobutylisonitrile (MIBI) tomograms in order to compare the tracers for the assessment of myocardial viability and to validate a rapid protocol combining the two tracers. We studied 30 consecutive patients with known or suspected coronary artery disease [group 1: 16 with normal left ventricular function, mean left ventricular ejection fraction (LVEF) 55%, SD 6%; group 2: 14 with abnormal function, mean LVEF 28%, SD 8%].²⁰¹Tl was injected during infusion of adenosine followed by acquisition of conventional stress and redistribution tomograms. On a separate day,²⁰¹Tl was injected at rest with imaging 4 h later.^99mTc-MIBI was then given at rest and imaging was performed. Three images were compared: redistribution²⁰¹Tl, rest²⁰¹Tl, and rest^99mTc-MIBI. Tracer activity was classified visually and quantitatively in nine segments and segments with>50% activity were defined as containing clinically significant viable myocardium. Mean (±SD) global tracer uptake as a percentage of maximum was similar in group 1 (rest²⁰¹Tl 69%±12%, redistribution²⁰¹Tl 69%±15%, rest^99mTc-MIBI 70%±13%, ANOVAP>0.05), but in group 2 mean tracer uptake was significantly greater in the rest²⁰¹Tl images (59%±16%) than in redistribution²⁰¹Tl images (53%±17%) or rest^99mTc-MIBI images (53%±19%) (ANOVAP=0.02). Overall agreement for regional uptake score was excellent ( from 0.79 to 0.84), although there were a significant number of segments with less uptake shown by redistribution²⁰¹Tl and by rest^99mTc-MIBI than by rest²⁰¹Tl in group 2 (P<0.001). The number of segments with significant viable myocardium in group 1 was very similar between the three images (P>0.05) but in group 2 rest²⁰¹Tl identified significantly more segments as viable than the other images (McNemarP<0.001). Thus²⁰¹Tl and^99mTc-MIBI provide similar information in patients without prior infarction and with normal left ventricular function (group 1), and a rapid protocol with stress²⁰¹Tl injection and imaging followed immediately by rest^99mTc-MIBI injection and imaging is feasible. In patients with abnormal left ventricular function and prior infarction (group 2),^99mTc-MIBI may underestimate the extent of clinically significant viable myocardium.     

Comparison between 360° and 180° data sampling in thallium-201 rest-redistribution single-photon emission tomography to predict functional recovery after revascularization

Whether 360° or 180° imaging should be used in cardiac thallium-201 single-photon emission tomography (SPET) studies to detect coronary artery disease remains controversial. Moreover, the relative diagnostic accuracy of 360° and 180°²⁰¹Tl SPET for the assessment of myocardial viability has never previously been studied. The aim of this study was to perform a direct comparison between 180° and 360° data sampling to detect viable myocardium in patients undergoing revascularization; in order to allow optimal detection of viability a rest-redistribution protocol was used. The²⁰¹Tl results were compared with improvement of regional wall motion abnormalities after the revascularization, which was considered as the gold standard for myocardial viability. Thirty-two patients, scheduled for revascularization, underwent rest-redistribution²⁰¹Tl SPET, using a 360° arc. Raw data along a 180° arc (45° RAO to LPO) were selected from the original 360° data sets (both early an late²⁰¹Tl images). All SPET data were analysed semi-quantitatively using circumferential profiles of the short-axis images; the data were displayed in polar maps. Criteria for viability included percentage²⁰¹Tl redistribution and percentage²⁰¹Tl activity on the late image. Regional wall motion was assessed with two-dimensional echocardiography before and 3 months after revascularization. The sensitivities of 360° and 180° imaging for the prediction of functional recovery were 82% and 89%, respectively, whereas the specificities were 51% and 55%, respectively. The diagnostic accuracy of 360° imaging was 62% and that of 180° imaging 67%. This study shows that 360° and 180° imaging have comparable diagnostic accuracy in the prediction of functional recovery after revascularization. With the newer dual-head gamma camera systems with each detector opposing each other, 360° imaging may be preferred.     

Proportional anatomical stereotactic atlas for visual interpretation of brain SPET perfusion images

A semi-automatic method was developed to determine the anterior (AC) and posterior (PC) commissures on brain single-photon emission tomographic (SPET) perfusion images, and then to draw the proportional anatomical Talairach's grid on each axial SPET image. First, the AC-PC line was defined on SPET images from the linear regression of four internal landmarks (frontal pole of the brain, inferior limit of the anterior corpus callosum, sub-thalamic point and occipital pole). Second, the SPET position of AC and PC points on the AC-PC line was automatically determined from measurements made on hard copies of magnetic resonance (MR) images of the patients. Finally, a proportional Talairach's grid was automatically drawn on each axial SPET image. To assess the accuracy of localization of AC and PC points, co-registered technetium-99m hexamethylpropylene amine oxime SPET and MR images from 11 subjects were used. The mean displacements between estimated points on SPET and true points on MRI (x=sagittal, y=frontal and z=axial displacement) were calculated. The mean displacements (in mm) were x=–1.4±1.8, y=–1.7±3.3 and z=–1.1±2.5 for AC, and x=–1.8±1.8, y=0.3±3.2 and =–1.3±2.7 for PC. These displacements represented an error of less than 5 mm at the anterior or posterior pole of the brain or at the vertex. Intra- and inter-observer comparisons did not reveal significant differences in mean displacements. Thus, this semi-automatic method results in reproducible and accurate stereotactic localization of SPET perfusion abnormalities. This method can be used routinely for repeat follow-up studies in the same subject as well as in different individuals without requiring SPET MRI co-registration.     

Sympathetic innervation of the left ventricle is impaired in arrhythmogenic right ventricular disease

Arrhythmogenic right ventricular disease (ARVD) is a disease of unknown origin that primarily affects the right ventricle and is characterized by ventricular tachyarrhythmias which may lead to syncope and even, though rarely, sudden cardiac death. In 25 patients with ARVD, sympathetic innervation of the left ventricle was assessed by iodine-123 metaiodobenzylguanidine single photon emission tomography (1231-MIBG SPET). In addition, thallium-201 SPET was performed. The diagnosis of ARVD was made by an electrophysiological study and right and left heart catheterization including right ventricular endomyocardial biopsy. Ischaemic heart disease was excluded by coronary angiography. A group of seven patients without any evidence of heart disease served as a control group. Twenty-two of the 25 patients showed reduced uptake of ¹²³I-MIBG. The abnormal areas were located predominantly in posterior and posteroseptal segments of the heart. No focus of increased ¹²³I-MIBG activity could be demonstrated. No patient had signs of left ventricular involvement on left ventricular angiography. In contrast to the results of the ¹²³I-MIBG SPET, those of ²⁰¹TI SPET were normal in 16 patients. The remaining nine patients showed areas of slight hypoperfusion not correlated with the reduced ¹²³I-MIBG uptake. ¹²³I-MIBG scintigraphy allows detection of left ventricular adrenergic dysinnervation in ARVD patients without morphological or functional abnormalities of the left ventricle. Correspondence to: H. Lerch     

Combined thallium 201/technetium 99m-labeled pyrophosphate tomography for identification of the “culprit” vessel in acute myocardial infarction

Background

Many previous investigations have used the presence of transient ischemic ²⁰¹Tl perfusion defect to localize coronary artery stenosis. This study reports the results of ²⁰¹Tl tomography alone and combined ²⁰¹Tl/^99mTc-labeled pyrophosphate (^99mTc PYP) tomography employed to identify the infarct-related vessel in patients with acute myocardial infarction (AMI).

Methods and Results

All short-axis images were evaluated by dividing each left ventricular slice into eight equal sectors. In addition, for combined ²⁰¹Tl/^99mTc PYP tomography, two sectors were added to evaluate involvement of the right ventricle. In a preevaluation phase of the study, the sectors were assigned to the supplying coronary arteries in 75 patients with single chronic myocardial infarction related to the left anterior descending coronary artery (LAD), left circumflex artery (LCX), or right coronary artery (RCA). In this pilot phase, ²⁰¹Tl tomograms were reviewed in conjunction with the angiographic data. This assignment was then tested prospectively in 117 patients with AMI. As confirmed by angiography, the AMI was related to the LAC, LCX, and RCA in 54, 17, and 46 patients, respectively. Sensitivity and specificity for ^99mTc PYP accumulation on combined ²⁰¹Tl/^99mTc PYP tomography were 98% a nd 100% for the LAD, 88% and 99% for the LCX, and 98% and 96% for the RCA, respectively. For ²⁰¹Tl tomography, sensitivity and specificity for identification of the culprit vessel were 94% and 89% for the LAD, 82% and 91% for the LCX, and 72% and 96% for the RCA, respectively.

Conclusion

This prospective study demonstrates that combined ²⁰¹Tl/^99mTc PYP tomography is highly accurate for identification of the infarct-related artery in AMI, even in patients with multivessel disease. Positive contrast visualization of myocardial necrosis in both the left and right ventricle allows for reliable differentiation between AMI related to the LCX or RCA territory. In comparison, for ²⁰¹Tl tomography the sensitivity to detect the culprit vessel, particularly the LCX and RCA, appears to be lower than for ²⁰¹Tl/^99mTc PYP imaging, particularly in patients with prior infarction or right dominant coronary artery.     

Single-photon emission tomography studies of rubidium-81 in the detection of ischaemic heart disease,using a stress-reinjection protocol

The present study was designed to determine the feasibility of using single-photon emission tomography (SPET) imaging with rubidium-81 (T _1/2 = 4.54 h) to detect ischaernic heart disease, using a stress-reinjection protocol and a specially constructed 511-keV hexagonal hole collimator for a standard gamma camera. The diagnostic performance of ⁸¹Rb SPET in detecting coronary artery disease (CAD) was investigated in 52 patients with a high prevalence of CAD. Coronary arteriography was performed in 34 patients, 25 of whom were classified as having significant stenosis (50%). At peak exercise (Cornell protocol), 111–222 MBq ⁸¹Rb was injected i.v. for stress imaging, and after 3 h of rest, 74–111 MBq was reinjected for rest imaging. The displayed short- and long-axis slices and the polar map images were interpreted qualitatively. In comparison to coronary arteriography, which served as the gold standard, the performance of ⁸¹Rb SPET revealed a sensitivity of 95% for the detection of CAD. Images of diagnostic quality were obtained in all patients, these being comparable to thallium-201 SPET images. In conclusion, these results indicate that the described method can be routinely used for the positron emitter ⁸¹Rb with a conventional gamma camera and special shielding. ⁸¹Rb has the well-known advantages of a potassium analogue and ⁸¹Rb SPET permits better visualization, particularly of the posterior wall of the myocardium, due to the higher photon energy. Considering the typical dose of ²⁰¹Tl used for SPET (74–148 MBq), a ⁸¹Rb SPET scan imposes a significantly lower radiation burden on the patient.     

Clinical value of triple-energy window scatter correction in simultaneous dual-isotope single-photon emission tomography with123I-BMIPP and201TI

To improve the image quality in simultaneous dual-isotope single-photon emission tomography (SPET) with iodine-123 labelled 15-(p-iodophenyl)-3-methylpentadecanoic acid (BMIPP) and thallium-201, we applied the triple-energy window method JEW) for correction of the cross-talk and scatter artifact. Seventy-one patients with coronary artery disease were included.²⁰¹T1 cross-talk into the¹²³I acquisition window (group 1,n = 30) and¹²³I cross-talk into the²⁰¹Tl window (group 2,n = 41) were studied. In group 1,¹²³I images were first obtained (single-isotope images), followed by²⁰¹Tl injection and SPET acquisition using dual-isotope windows (dual-isotope images). In group 2, the order was reversed. The dual-isotope SPET images with and without TEW were compared with the single-isotope images. Qualitative evaluation was performed by scoring the segmental defect pattern. Detectability of the mismatched fatty acid metabolism on dual-isotope SPET was evaluated by receiver operating characteristic (ROC) curve analysis. Segmental defect pattern agreement between dual and corrected single images was significantly improved by TEW correction (P<0.01). The agreement was particularly improved in segments with absence of uptake. There was no significant difference between TEW-corrected dual-isotope SPET and corresponding single-isotope SPET with regard to either % defect count or background activity. Mismatched fatty acid metabolism depicted by dual-isotope SPET predicted abnormal wall motion more accurately with TEW than without TEW. With TEW, a practical method for scatter and cross-talk correction in clinical settings, simultaneous dual¹²³I-BMIPP/²⁰¹Tl SPET is feasible for the assessment of myocardial perfusion/metabolism mismatch.     

Localization of exercise-induced myocardial ischemia with single view and biplanar radionuclide ventriculography: validation in single vessel coronary disease

The ability of single view and biplanar radionuclide ventriculography (RVG) to determine the location of myocardial ischemia during maximal graded supine bicycle exercise was assessed in 50 patients with chest pain, no prior myocardial infarction, and a single coronary stenosis of 50% luminal diameter narrowing at coronary angiography. A biplane collimator was used so that both right anterior oblique (RAO) gated first-pass and left anterior oblique (LAO) equilibrium RVG could be performed at rest and exercise. Results were compared with those obtained using 4-view ²⁰¹Tl myocardial scintigraphy in the same patients. Regional wall motion abnormalities (WMA) and ²⁰¹Tl perfusion defects were detected and assigned to individual coronary vessels by agreement between at least two of three independent observers, who read all studies blinded along with those from control subjects with chest pain but no angiographically significant coronary artery disease. When scintigraphic abnormalities were detected, both biplanar RVG (36/39=92%) and ²⁰¹Tl (25/25=100%) were more frequently correct in predicting the stenosed vessel than single view LAO RVG (24/32=75%) (P<0.05). At RVG only inferior WMA, in the RAO view, predicted right coronary stenosis. Only posterolateral WMA, in the LAO view, predicted left circumflex stenosis. Thus biplanar, but not single view, LAO exercise RVG is a reasonable alternative to exercise ²⁰¹Tl for localizing exercise-induced ischemic abnormalities to individual coronary stenoses.This work was supported by a Postgraduate Medical Research Scholarship from the National heart Foundation of Australia (Canberra), and by the Alfred Hospital Whole Time Medical Specialists (Melbourne)     

Relation between myocardial uptake of thallium-201 chloride and fluorine-18 fluorodeoxyglucose imaged with single-photon emission tomography in normal individuals

Recently, we have demonstrated the feasibility of imaging myocardial uptake of fluorine-18 fluorodeoxyglucose (FDG) with single-photon emission tomography (SPET) using a specially designed collimator. Thallium-201 was used to determine distribution of perfusion for comparison with FDG uptake. However, regional²⁰¹Tl and FDG activities may be different, based on differences in tracer attenuation and the use of different collimators. To study the relation between tracer activities imaged with SPET, nine healthy individuals underwent resting²⁰¹Tl SPET and FDG SPET during a hyperinsulinaemic euglycaemic clamp. The SPET data were analysed semiquantitatively, using circumferential profiles. Mean profiles of midventricular short-axis slices showed no significant difference between²⁰¹Tl and FDG activity. Regional fluctuations were similar for FDG and²⁰¹Tl; the highest tracer activities were observed in the lateral wall and the lowest activities in the septum. Finally, pooled data (n=1620 segmental activities) in nine individuals showed a linear correlation (P<0.0001) between²⁰¹Tl and FDG activity: FDG=0.76²⁰¹Tl + 0.23 (r=0.70). These data demonstrate the absence of major differences between regional²⁰¹Tl and FDG activity in normal myocardium, suggesting that no separate²⁰¹Tl and FDG SPET reference values are needed for comparison with patient studies.     

Prediction of post-revascularization functional recovery of asynergic myocardium using quantitative thallium-201 rest-redistribution tomography: has the reverse redistribution pattern an independent significance?

The significance of reverse redistribution on rest-redistribution thallium-201 myocardial scintigraphy is unclear. Previous studies suggested that reverse redistribution segments with normal resting activity include viable myocardium, whilst resting defects with further worsening correspond to scar. We evaluated whether reverse redistribution has an independent significance for the prediction of post-revascularization recovery, particularly as compared with the quantification of redistribution activity. We studied 26 coronary artery disease patients with left ventricular dysfunction, who underwent ²⁰¹Tl rest-redistribution single-photon emission tomography (SPET) and echocardiography before revascularization. Viability was defined by the detection of wall motion improvement on follow-up echocardiography. ²⁰¹Tl activity was considered normal if ≥80%, moderately reduced if <80% but ≥50%, and severely decreased if <50%. Reverse redistribution was defined as a defect in redistribution images with ≥10% decrease in relative ²⁰¹Tl activity compared with the resting value. Reverse redistribution was detected in 33 segments (10%). Baseline dysfunction was equally observed in the reverse redistribution and in the non-reverse redistribution segments (64% vs 56%, P=0.40) and the rate of asynergic segments with post-revascularization recovery was not different between the two groups (33% vs 54%, P=0.11). The rate of functional recovery in redistribution defects without reverse redistribution was 53% in moderate and 30% in severe defects; the corresponding values for the reverse redistribution segments were 50% and 27% (all non-significant versus non-reverse redistribution segments). For the prediction of post-revascularization recovery in asynergic segments, the detection of reverse redistribution on rest-redistribution ²⁰¹Tl SPET does not add any information to the quantitative analysis of redistribution activity. Received 19 November 1997 and in revised form 20 February 1998