Assessment of systolic wall thickening using technetium-99m methoxyisobutylisonitrile in patients with coronary artery disease: relation to thallium-201 scintigraphy with re-injection

The results of resting planar ECG-gated technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI) imaging were compared with those of thallium-201 (TI) reinjection after exercise-redistribution scintigraphy in 20 patients (19 men, 1 woman, mean age 53±10 years) with angiographically proven coronary artery disease. Eight normal subjects (seven men, one woman, mean age 50±8 years) constituted the control group. In these subjects, only resting^99mTc-MIBI imaging was performed. The standardized percent count increase from end-diastole to end-systole was calculated as an index of wall thickening in 13 segments for each study. Regional wall thickening index (WTI) and^99mTc-MIBI uptake were significantly different (P<0.05) among segments classified as normal, reversible defects, irreversible defects with increased tracer uptake after re-injection (Re+) or irreversible defects with unchanged tracer uptake after re-injection (Re-) on TI imaging. Furthermore, WTI and^99mTc-MIBI uptake were significantly higher (P<0.05) in Resegments with moderate reduction of T1 uptake (50% of peak activity) than in Re- segments with severe reduction of TI uptake (<50% of peak activity). A significant relationship between WTI and the results of TI scintigraphy was observed (rho=0.71,P<0.0001). The percentage of Re- segments with severe reduction of WTI was significantly higher compared to Re+ segments (64% vs 3%,P<0.01). Furthermore, compared with moderate Re- segments, a significantly higher percentage of severe Re- segments showed a severe reduction of WTI (86% vs 48%,P<0.01). Our data document a close relationship between^99mTc-MIBI regional wall thickening, myocardial perfusion and TI uptake after reinjection. The results of this study suggest that regional WTI decreased significantly as myocardial perfusion decreased. In addition, regional wall thickening was preserved in segments with exercise-induced ischaemia and enhanced TI uptake after re-injection.     

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.     

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.     

Resting technetium-99m methoxyisobutylisonitrile cardiac imaging in chronic coronary artery disease: comparison with rest-redistribution thallium-201 scintigraphy

We studied 19 patients with angiographically proven coronary artery disease and left ventricular dysfunction (ejection fraction 33% ± 8%) by resting technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI) and rest-redistribution thallium-201 cardiac imaging. Thallium and (^99mTc-MIBI) studies were visually analysed. Of 285 segments, 203 (71%) had normal thallium uptake, 48 (17%) showed reversible thallium defects and 34 (12%) showed irreversible thallium defects. Of these 34 irreversible thallium defects, 19 (56%) were moderate and 15 (44%) were severe. Of the corresponding 285 segments, 200 (70%) had normal ^99mTc-MIBI uptake, while 37 (13%) showed moderate and 48 (17%) showed severe reduction of 99 ^99mTc-MIBI uptake. Myocardial segmental agreement for regional uptake score between initial thallium and resting (^99mTc-MIBI) images was 90% (=0.78). Segmental agreement between delayed thallium and resting ⁹⁹Tc-MIBI images was 77% (=0.44). In particular, in 26 (9%) segments ^99mTc-MIBI uptake was severely reduced while delayed thallium uptake was normal or only moderately reduced. These data suggest that although rest-redistribution thallium and resting (^99mTc-MIBI) cardiac imaging provide concordant results in the majority of myocardial segments, some segments with severely reduced resting ^99mTc-MIBI uptake may contain viable but hypoperfused myocardium. Thus, conclusions on myocardial viability based on ^99mTc-MIBI uptake should be made with caution in chronic coronary artery disease.     

Assessment of myocardial perfusion and viability with technetium-99m methoxyisobutylisonitrile and thallium-201 rest redistribution in chronic coronary artery disease

We compare thallium-201 rest redistribution and fluorine-18 fluorodeoxyglucose ([¹⁸F]FDG) for the assessment of myocardial viability within technetium-99m methoxyisobutylisonitrile (MIBI) perfusion defects in 27 patients with chronic stable coronary artery disease. The following studies were performed: (1) stress^99mTc-MIBI, (2) rest^99mTc-MIBI, (3)²⁰¹T1 rest-redistribution single-photon emission tomography, (4) [¹⁸F]FDG positron emission tomography. The left ventricle was devided into 11 segments on matched tomographic images. The segment with the highest activity at stress was taken as the reference (activity=100%). Perfusion defects at^99mTc-MIBI rest were classified as severe (activity<50%), moderate (activity 50%–60%) or mild (activity 60%–85%). Uptakes of [¹⁸F]FDG and rest-redistributed²⁰¹Tl were recognized as significant if they exceeded 50% of that in the reference segment. Among the 33 segments with severe^99mTc-MIBI rest perfusion defects, 21 had significant [¹⁸F]FDG and 10 significant rest-redistributed²⁰¹Tl uptake. As regards the 37 segments with moderate defects, [¹⁸F]FDG was present in 29 and²⁰¹Tl in 31, while of the 134 segments with mild defects, 128 showed [¹⁸F]FDG uptake, and 131,²⁰¹Tl uptake. In conclusion, there is an inverse relationship between the severity of^99mTc-MIBI perfusion defects and the uptake of rest-redistributed²⁰¹Tl and [¹⁸F]FDG. Both tracers are adequate markers of viability in mild and moderate defects; in severe defects²⁰¹Tl might underestimate the presence of viability as assessed by [¹⁸F]FDG.     

Impaired coronary circulation in acute myocardial infarction: A dipyridamole-thallium-201 study

Coronary flow reserve is not fully restored immediately after revascularization of an occluded vessel. The present study examined the coronary flow impairment in patients with acute myocardial infarction (AMI) after successful balloon angioplasty or spontaneous recanalization (without residual epicardial coronary stenosis). Fourteen patients underwent thallium-201 dipyridamole scintigraphy in the acute phase (mean 5.9 days) and in the chronic phase (mean 24.6 days) after AMI. A²⁰¹Tl reinjection study was carried out only in the acute phase of AMI. The fill-in phenomenon was assessed by the %²⁰¹Tl uptake in the infarct region after²⁰¹Tl reijection, and positive (n=8) and negative (n=6) fill-in groups were distinguished. The %²⁰¹Tl uptake increased from the acute phase study to the chronic phase study in the positive fill-in group (56.1%±4.1% to 74.4%±13.6%,P<0.001), whereas it decreased in the negative fill-in group (54.0%±10.6% to 43.7%±9.9%,P<0.05). The change in %²⁰¹Tl uptake following reinjection was significantly correlated with the improvement in regional ventricular wall motion in the chronic phase (r=0.85,P<0.001). We conclude that the impaired coronary flow reserve persisted after balloon angioplasty or spontaneous recanalization, which might indicate the presence of “microvascular stunning”. The increase in %²⁰¹Tl uptake predicted the change in ventricular wall motion.     

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     

Quantitative exercise technetium-99m tetrofosmin myocardial tomography for the identification and localization of coronary artery disease

The aim of this study was to evaluate the accuracy of quantitative 1-day exercise-rest technetium-99m tetrofosmin tomography in the identification of patients with coronary artery disease (CAD) and in the detection of individual stenosed coronary vessels. Sixty-one patients with suspected CAD who underwent coronary angiography and 13 normal volunteers were studied. All patients were submitted to two i.v. injections of^99mTc-tetrofosmin, one at peak exercise (370 MBq) and the other (1110 MBq) at rest 3 h after exercise (images 15–30 min after injection for both studies). All patients with CAD (0% luminal stenosis) (n=50) had an abnormal^99mTc-tetrofosmin tomogram. Only one patient without significant coronary narrowing showed abnormal findings. Overall sensitivity, specificity and diagnostic accuracy in the detection of individual stenosed vessels were 77%, 93% and 85%, respectively. Sensitivity and diagnostic accuracy in the identification of individuals stenosed coronary vessels were significantly higher (P<0.05) in patients with single-vessel disease (n=21) than in those with multivessel disease (n=29). Sensitivity, specificity and accuracy for detecting individual diseased vessels were similar in patients without previous myocardial infarction (n=26) and in those with previous myocardial infarction (n=35). In myocardial territories related to non-infarcted areas (n=128), sensitivity and specificity in the detection of stenosed vessels were 70% and 95%, respectively. In infarcted areas (n=55), sensitivity and specificity in the detection of stenosed vessels were 85% (P=NS vs non-infarcted areas) and 75% (P<0.05 vs non-infarcted areas), respectively. Finally, sensitivity was significantly lower (P<0.05) in vascular territories supplied by vessels with moderate stenosis (50%–75%) than in those supplied by vessels with severe stenosis (>75%). The results of this study demonstrate that quantitative 1-day exercise-rest^99mTc-tetrofosmin single-photon emission tomographic imaging is a suitable and accurate technique to identify patients with CAD and to detect individual stenosed coronary vessels.     

Fluorine-18 deoxyglucose PET for assessment of viable myocardium in perfusion defects in 99mTc-MIBI SPET: a comparative study in patients with coronary artery disease

Extent and frequency of viable tissue in myocardial segments yielding a perfusion defect on technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI), single photon emission tomography (SPET) at rest was prospectively investigated with 2-¹⁸F-2-deoxyglucose (¹⁸FDG) positron emission tomography (PET) in 46 patients with chronic coronary artery disease (CAD). Of these, 43 had a history of old myocardial infarction. For comparative visual and quantitative evaluation of identical anatomical slices, PET image files were converted into the SPET file structure and into the same matrix size. SPET and PET images were documented and visually (9 segments/patient) or semiquantitatively evaluated by a target-like polar map. Relative perfusion was expressed in percentage of peak ^99mTc-MIBI uptake. Sample ¹⁸FDG uptake was related to the ¹⁸FDG uptake in the area of such maximal perfusion (¹⁸FDG uptake was 100% at the 100% ^99mTc-MIBI uptake area). Of 414 segments, 167 (40%) revealed a resting perfusion defect. ¹⁸FDG uptake was present in 38 (23%) of the defects, while another 40 (24%) segments yielded ¹⁸FDG uptake in the periphery of the defect. When grouped according to the degree of ^99mTc-MIBI uptake-reduction (in percentage of peak activity), 80% of severe defects (30% of peak uptake), 48% of moderate (31%–50% of peak uptake) and 31% of mild (>50% of peak uptake) defects were considered as non-viable on the basis of ¹⁸FDG uptake. Complete viability was found in none of the severe defects in contrast to 29% of moderate and 35% of mild perfusion defects. From these data we conclude that ^99mTc-MIBI uptake as a myocardial perfusion marker underestimates myocardial viability in patients with chronic CAD and after myocardial infarction. Nevertheless, only moderate reductions of ^99mTc-MIBI uptake seem to imply a greater likelihood for viability. Comparative analysis of metabolism and flow is possible with different tomographic systems and is valuable for clinical evaluation of the cardiac patient. Offprint requests to: C. AltehoeferThis paper presents in part results of the doctoral thesis of C. Feinendegen and was supported in part by the EEC Concerted Action on PET in Cardiology.It is dedicated to Prof. L.E. Feinendegen, Jülich/Düsseldorf on the occasion of his 65th birthday.     

Adenosine coronary vasodilation quantitative technetium 99m methoxy isobutyl isonitrile myocardial tomography in the identification and localization of coronary artery disease

Background

Exercise and dipyridamole ^99mTc-labeled methoxy isobutyl isonitrile (MIBI) myocardial scintigraphy have been widely used for the diagnosis of coronary artery disease (CAD). However, only limited data on adenosine ^99mTc-labeled MIBI cardiac imaging are currently available. This study was designed to assess the accuracy of quantitative adenosinerest ^99mTc-labeled MIBI tomography in the diagnosis and localization of CAD.

Methods and Results

Fifty-seven consecutive patients with suspected CAD who underwent coronary angiography and 22 normal volunteers were studied. All patients underwent ^99mTc-labeled MIBI tomography after administration of adenosine (140 μg/kg intravenously for 6 minutes) and at rest. A total of 171 vascular coronary territories were analyzed quantitatively. All patients with CAD (≥50% luminal stenosis) (n=55) had abnormal ^99mTc-labeled MIBI tomograms. The normalcy rate was 86% by quantitative analysis. Overall sensitivity, specificity, and diagnostic accuracy for detection of individual stenosed vessels were 84%, 87%, and 85%, respectively. In patients with one-vessel CAD (n=24), sensitivity and diagnostic accuracy in the detection of individual stenosed vessels were significantly (p<0.05) higher compared with patients with multivessel CAD (n=31). Moreover, 75% of patients with one-vessel disease showed a scintigraphic pattern characterized by the presence of perfusion defects in only one coronary artery territory, and 74% of patients with multivessel disease showed a scintigraphic pattern characterized by the presence of perfusion defects in two or more coronary artery territories. Sensitivity, specificity, and diagnostic accuracy for detecting individual diseased vessels were similar in patients without previous myocardial infarction (n=18) compared with those with previous myocardial infarction (n=39). In myocardial territories related to noninfarcted areas (n=124), sensitivity and specificity in the detection of stenosed vessels were 75% and 88%. In infarcted areas (n=47), sensitivity and specificity in the detection of stenosed vessels were 98% and 80% (differences not significant vs noninfarcted areas).

Conclusions

Adenosine-controlled coronary vasodilation combined with quantitative ^99mTc-labeled MIBI tomography is accurate for identifying patients with CAD and localizing individual stenosed coronary arteries.     

A comparison of99mTc-MIBI myocardial SPET with electron beam computed tomography in the assessment of coronary artery disease

We compared technetium-99m methoxyisobutylisonitrile (MIBI) myocardial perfusion single-photon emission tomography (SPET) (MPS) and electron beam computed tomography (EBCT) in order to assess their respective value in the detection of coronary artery disease (CAD).^99mTc-MIBI SPET (stress-resting) and EBCT studies were performed in 51 patients with suspected CAD who underwent coronary angiography (CAG). CAG showed that of the 51 patients, 36 had coronary stenosis 50% while 15 had normal results. A moderate positive rank correlation was found between coronary calcification detected by EBCT and MPS score (r _s=0.5283,P<0.01). The concordance between EBCT and MPS for the evaluation of CAD was 72.5% (37/51). The sensitivity of EBCT in detecting CAD in 51 patients was comparable to that of MPS (81% vs 94%, NS). However, the accuracy of EBCT was lower than that of MPS (78% vs 94%,P<0.025). As regards the detection of individual coronary artery disease, there was no significant difference in sensitivity between EBCT and MPS (65% vs 75%, NS); however, the specificity and accuracy of EBCT were lower than those of MPS (specificity: 77% vs 95%,P<0.005; accuracy 71% vs 85%,P<0.005). The sensitivity, specificity and accuracy of MPS in detecting single-vessel disease were higher than those of EBCT (sensitivity: 86% vs 42%,P<0.025; specificity: 96% vs 70%,P<0.025; accuracy: 93% vs 61%,P<0.005). However, no significant differences in the sensitivity, specificity and accuracy of MPS and EBCT were found in respect of multivessel disease. In conclusion:^99mTc-MIBI myocardial perfusion SPET and EBCT provide different information in the assessment of CAD. The sensitivity of EBCT for the detection of CAD is comparable with that of MPS; however, the specificity and accuracy of EBCT are lower than those of MPS. More reliable results will be obtained if both myocardial perfusion SPET and EBCT are performed.     

Assessment of non-reperfused and reperfused myocardial infarction using diffusible or deposited radiolabelled perfusion imaging agents

Purpose Incomplete microvascular reperfusion is often observed in patients undergoing thrombolytic therapy or angioplasty for acute myocardial infarction and has important prognostic implications. We compared the myocardial uptake of diffusible (²⁰¹Tl) and deposited (^99mTcN-NOET) perfusion imaging agents in the setting of experimental infarction. Methods Rats were subjected to permanent coronary occlusion (OCC, n=10) or to 45-min occlusion and reperfusion (REP, n=17). Seven days later, the tracers were co-injected and the animals were euthanised 15 min (all ten rats in the OCC group and 12 rats in the REP group) or 120 min (five rats from the REP group, euthanised at this time point to evaluate any redistribution of the tracers: REP-RED group) afterwards. Infarct size determination and ^99mTcN-NOET/²⁰¹Tl ex vivo imaging were performed. Regional flow and tissue oedema were quantified using radioactive microspheres and ^99mTc-DTPA, respectively. Results ^99mTcN-NOET and ²⁰¹Tl defect magnitudes were similar in OCC animals (0.11±0.01 vs 0.13±0.01). In REP animals, ²⁰¹Tl defect magnitude (0.25±0.02) was significantly lower than the magnitude of ^99mTcN-NOET and flow defects (0.14±0.03 and 0.17±0.01, respectively; p<0.05), despite the lack of ²⁰¹Tl redistribution (REP-RED animals). ^99mTc-DTPA indicated the presence of oedema in the reperfused area. Blood distribution studies showed that, unlike ^99mTcN-NOET, ²⁰¹Tl plasma activity was mostly unbound to plasma proteins. Conclusion ^99mTcN-NOET and ²⁰¹Tl delineated the non-viable area in chronic non-reperfused and reperfused myocardial infarction. The significantly decreased ²⁰¹Tl defect in reperfused infarction was likely due to partial diffusion of the tracer from the plasma into the oedema present in the infarcted area. Deposited perfusion tracers might be better suited than diffusible agents for the assessment of regional flow following reperfusion of myocardial infarction.     

Comparison of technetium-99m sestamibi left ventricular wall motion and perfusion studies with thallium-201 perfusion imaging: in search of the combination of variables with the highest accuracy in predicting coronary artery disease

Measurements of myocardial perfusion and ventricular function are expected to provide additional information in the detection of coronary artery disease (CAD). The purpose of this study was threefold: (1) to determine to what extent technetium-99m sestamibi wall motion yields different information compared with^99mTc-sestamibi and thallium-201 perfusion; (2) to test which information unique to either study is of value in diagnosing CAD; and (3) to assess the combination of variables with the highest diagnostic accuracy. Perfusion and wall motion scores (at rest and during exercise) obtained from visual and quantitative planar²⁰¹T1 and^99mTc-sestamibi scintigraphy of 60 patients with suspected CAD were compared with the angiographic results by means of a polytomous logistic regression model and the diagnostic values were compared with one another. All univariate variables were significantly related to the probability of CAD and its extent. Comparative studies revealed a large degree of correlation between²⁰¹T1 stress and redistribution variables. The rest^99mTc-sestamibi and wall motion studies contained partially different information. Stepwise logistic regression analysis showed the strongest diagnostic power for the combination of²⁰¹Tl visual analysis of the stress images with quantitative redistribution images (sensitivity 93%, specificity 71%). The diagnostic power was similar for all combinations of visual and quantitative analyses of the exercise and redistribution images. The strongest diagnostic power of the^99mTc-sestamibi variables was the score of the diastolic stress image (sensitivity 91%, specificity 79%). Comparable sensitivity and specificity estimates were found when both optimal models were compared. Wall motion studies did not have additional diagnostic power. Although^99mTc-sestamibi wall motion studies, both at rest and during exercise, provide information in addition to the^99mTc-sestamibi or²⁰¹Tl myocardial perfusion variables, the information does not enhance the diagnostic power with regard to the prediction of CAD.     

Myocardial flow reserve is influenced by both coronary artery stenosis severity and coronary risk factors in patients with suspected coronary artery disease

Purpose Myocardial flow reserve (MFR) measurement has an important role in assessing the functional severity of coronary artery stenosis. However, a discrepancy between the anatomical severity of coronary artery stenosis and MFR is often observed. Such a discrepancy may be explained by coronary risk factors. In this study, we aimed to investigate the influence of coronary artery stenosis severity and risk factors on MFR.Methods Seventy-four patients suspected to have coronary artery disease and seven age-matched healthy volunteers were enrolled. Myocardial blood flow (MBF) and MFR were measured using ¹⁵O-labelled water PET. Regional MFR was calculated in regions with significant coronary artery stenosis (stenotic regions) and in regions without significant stenosis (remote regions). The contributions of coronary artery stenosis severity and coronary risk factors were assessed using univariate and multivariate analyses.Results In stenotic regions, MFR correlated inversely with coronary artery stenosis severity (r=−0.50, p<0.01). Univariate analysis did not show any significant difference in MFR between the patients with and the patients without each risk factor. In remote regions, however, MFR was significantly decreased in the diabetes and smoking groups (each p<0.05). By multivariate analysis, diabetes and smoking were independent predictors of MFR (each p<0.05). In the group with more than one risk factor, MFR was significantly lower (2.78±0.79) than in the other group (3.40±1.22, p<0.05).Conclusion MFR is influenced not only by coronary stenosis severity but also by coronary risk factors. In particular, the influence of risk factors should be considered in regions without severe coronary stenosis.This study received no financial sponsorship.     

Technetium 99m-labeled tetrofosmin myocardial tomography in patients with coronary artery disease: Comparison between adenosine and dynamic exercise stress testing

Background

Pharmacologic coronary vasodilation with adenosine, combined with myocardial scintigraphy, is a useful test for the diagnosis of coronary artery disease (CAD) in patients unable to exercise. It has been demonstrated recently that exercise ^99mTc-labeled tetrofosmin cardiac imaging can be used for the detection of CAD. However, no data are available comparing ^99mTc-labeled tetrofosmin adenosine and exercise tests in the same patients.

Methods and Results

The results of adenosine and exercise ^99mTc-labeled tetrofosmin myocardial tomography were compared in 41 patients (37 men and four women; mean age 53±8 years) with suspected or known CAD who underwent coronary angiography. All patients were submitted, on separate days, to three injections of ^99mTc-labeled tetrofosmin (740 MBq intravenously): one at rest, one during bicycle exercise, and one during adenosine infusion (140 μg/kg/min for 6 minutes with injection of ^99mTc-labeled tetrofosmin at 4 minutes). A total of 902 myocardial segments were analyzed quantitatively. One patient had normal coronary vessels, 19 patients had single-vessel CAD, 12 patients had two-vessel CAD, and nine patients had three-vessel CAD (>50% coronary stenosis) on coronary angiography. Adenosine induced a significant increase in heart rate (88±16 beats/min at peak vs 72±11 beats/min at rest; p<0.01). Systolic and diastolic blood pressure was not significantly different after adenosine infusion compared with rest. Double product was 22931 ± 7039 at peak exercise and 11229±3413 after adenosine (p<0.01). Agreement on the presence of abnormal single-photon emission computed tomography by adenosine and exercise was 100% by quantitative analysis. In all segments a significant relationship between exercise and adenosine ^99mTc-99m-labeled tetrofosmin uptake was observed (r=0.90; p<0.001). Segmental agreement for regional ^99mTc-labeled tetrofosmin uptake score between exercise and adenosine was observed in 737 (82%) of the 902 segments (kappa value of 0.66). Concordance between the two studies for identification of perfusion status was observed in 809 (90%) of the segments (kappa value of 0.80). Sensitivity and specificity for detection of stenosed vessels were not different for dynamic exercise stress testing and adenosine ^99mTc-labeled tetrofosmin cardiac tomography.

Conclusions

Despite different hemodynamic effects, adenosine and dynamic exercise ^99mTc-labeled tetrofosmin single-photon emission computed tomographic imaging provides similar information in the diagnosis and localization of CAD.     

European multi-centre comparison of thallium 201 and technetium 99m methoxyisobutylisonitrile in ischaemic heart disease

Fifty-six patients in Europe were entered into a multi-centre study to compare the accuracy of technetium 99m methoxyisobutylisonitrile (^99mTc-MIBI) for the detection of coronary artery disease (CAD) with thallium 201 (²⁰¹T1) chloride perfusion scanning. The results showed a high degree of concordance between the two radiopharmaceuticals. Some 81% (678/840) of myocardial segments showed the same result (normal, infarct or ischaemia), and 80% (45/56) of patients had the same diagnosis. Overall detection of CAD in patients was 98% for²⁰¹T1 and 96% for^99mTc-MIBI. Detection of CAD in total arteries was 68% for both agents. In this study^99mTc-MIBI was as accurate as²⁰¹T1 for the detection of coronary artery stenoses.     

Methoxyisobutylisonitrile (MIBI) Tc 99m SPECT to establish a correlate to coronary flow reserve,the perfusion reserve,from global and regional myocardial uptake after exercise and rest

With^99mTc-MIBI SPECT and a 4 h exercise (E; 150 MBq iv) and rest (R; 800 MBq iv) protocol global and regional left ventricular (LV) myocardial uptake was determined in 70 patients with angiographicall, confirmed coronary heart disease (CHD) and in 10 controls. The aim was to establish an E/R ratio as a correlate to coronary vascular reserve, representing perfusion reserve (PR). E/R ratios, obtained from total LV myocardium or from normal or impaired regions, were > 1.19 under all conditions, indicating the presence of higher flow during exercise than at rest (even in areas of low flow). Global PR separated (P<0.01) controls (1.63±0.21; mean ± SD) from severely diseased patients (1.29 ±0.14 in 2- or 3-vessel disease) only. Improved differential diagnosis was gained from calibrating the regional E/R ratio to regional differences (E minus R) of uptake. For the left ventricle regional PRs (RPR) for 25 ROIs of the target, framing the myocardium, were determined RPR at the regional maximum of^99mTc-MIBI uptake was similar in both controls (1.66) and patients (1.63), indicating a high probability of meeting some areas with functionally normal perfusion in patients with CHD. RPR allowed sufficient separation (P<0.025) concerning the degree of coronary artery stenosis (RPR in occlusion, 0.26; stenosis >75%, 0.39; <75%, 0.56). In controls, the overall value for RPR was 1.14+0.28 (P< 0.001). LV global PR and RPR were useful in separating patients with CHD vs controls and in classifying the severity of vascular stenosis.Dedicated to Prof. Dr. D. Emrich, Göttingen on the occasion of his 60^th birthday     

Myocardial washout rate of resting 99mTc-Sestamibi (MIBI) uptake to differentiate between normal perfusion and severe three-vessel coronary artery disease documented with invasive coronary angiography

Objectives

Patients with severe coronary artery disease (CAD) may present impaired mitochondrial function to enhance ^99mTc-sestamibi (MIBI) washout from ischemic myocardium. In this study, we aimed to study the MIBI washout rate (WR) between patients with three-vessel CAD (3V-CAD) confirmed by invasive coronary angiography and healthy normal volunteers (HNV) to evaluate the potential utility of MIBI WR to differentiate between these two populations and to stratify the CAD severity.

Methods

Ten HNV (male = 5, age = 56 ± 10 years) and eight 3V-CAD patients (male = 4, age = 62 ± 8 years) with 3V lumen stenosis ≥50 % were enrolled for this study. Each study subject had a resting MIBI perfusion scan at 90 min and a repeated scan at 4 h post the MIBI injection. Global WR (GWR) and regional WR (RWR) were quantified with the percentage difference of decay-corrected polar maps obtained from the two scans and compared between the HNV and 3V-CAD groups. For the 3V-CAD group, the severity of CAD was assessed with CAD severity scores (CADSS) utilizing degree and location of obstructive lesions (stenosis ≥50 %) for quantification and compared with WR to evaluate the correlation between these two variables.

Results

Significantly higher GWR was observed in the 3V-CAD (21.1 ± 4.6 %) group than the HNV group (9.5 ± 4.9 %) (p < 0.001). RWR values in left anterior descending (LAD), right coronary artery (RCA) and left circumflex (LCX) in the 3V-CAD group were also higher than those of the HNV group (LAD 20.7 ± 5.9 vs 9.4 ± 5.6, p < 0.001; RCA 21.3 ± 4.8 vs 9.2 ± 5.8, p < 0.001; LCX 20.5 ± 7.2 vs 10.1 ± 4.4, p = 0.002). Additionally, the linear correlation of GWR and total CADSS for the whole myocardium was strong and statistically significant (y = 0.86x ? 1.12, r ² = 0.73, p = 0.006).

Conclusion

Patients with impaired mitochondrial function due to 3V-CAD had consistently higher global and regional rest ^99mTc-sestamibi washout rates than those of healthy normal volunteers. The global rest ^99mTc-sestamibi washout rate is a sensitive indicator to stratify the severity of 3V-CAD and to differentiate between severe 3V-CAD and normal perfusion populations.     

The (F)utility of the thallium-201 quantitative lung/myocardial ratio in the detection of coronary artery disease

Exercise-induced increases in pulmonary uptake of thallium-201 (²⁰¹Tl) have been associated with exercise-induced myocardial dysfunction. To evaluate this phenomenon more replicably, a quantitative semi-automated computer program was used to generate, from anterior exercise and delayed views, lung-myocardial ratios (LMR) of²⁰¹Tl uptake in 78 patients [40 normal, 38 with coronary artery disease (CAD)]. Patients with CAD had a significantly higher mean exercise lung myocardial ratio (EXLMR) than normals (30.8 vs. 27.3;P < 0.003). In patients with adequate exercise (85% of an age-adjusted maximal heart rate), the EXLMRs of CAD patients were significantly higher than those of normals (29.7 vs. 25.5;P=0.003). However, this difference between CAD and normal patients was not apparent in a patient subgroup with submaximal exercise levels (< 85% of an age-adjusted maximal heart rate). In both normal and CAD patients, EXLMR decreased with increasing exercise levels (r=-0.555;P=0.007). In patients with²⁰¹Tl scans lacking visually defined perfusion defects (visually normal), an elevated LMR detected 60% of CAD cases with 81% specificity. A considerably elevated EXLMR in patients achieving adequate exercise should suggest the presence of CAD, even if there are no visually apparent cardiac perfusion defects. With submaximal exercise, however, the EXLMR is not a useful discriminator between CAD patients and normals.     

Non-Q-wave myocardial infarction: impaired myocardial energy metabolism in regions with reduced 99mTc-MIBI accumulation

Reduced regional technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI) accumulation in patients with chronic non-Q-wave infarction (NQWI) but without significant coronary artery stenosis indicates non-transmural damage of the myocardial wall. The aim of this study was to characterise cardiac energy metabolism after NQWI using phosphorus-31 magnetic resonance spectroscopy (³¹P-MRS) and to compare the biochemical remodelling with changes in regional ^99mTc-MIBI uptake and with morphological and functional parameters assessed by magnetic resonance imaging (MRI). Fifteen patients with a history of NQWI, exclusion of significant coronary artery stenosis (<50% diameter stenosis) and hypokinesia of the anterior wall (group A) were examined with ³¹P-MRS to study the effects of NQWI on myocardial energy metabolism. Spectroscopic measurements were performed in the infarct-related myocardial region. Corresponding gradient-echo MR images and myocardial ^99mTc-MIBI single-photon emission tomography images were acquired for exact localisation of the infarct region. All examinations were performed at rest under anti-ischaemic medication. Data were compared with those of patients in whom coronary artery disease had been excluded by angiography (group B, n=10). All patients of group A displayed anterior wall hypokinesia in the infarcted area on both ventriculography and MRI, with a reduced myocardial accumulation of ^99mTc-MIBI (66.3%ᆟ.8% vs 95.6%DŽ.2% in group B). The mean wall thickness during the complete cardiac cycle (9.5ǃ.8 mm vs 13.1ǃ.1 mm in group B, P<0.001), the systolic wall thickening (2.6ǃ.4 mm vs 5.8ǃ.5 mm in group B, P<0.01) and the phosphocreatine/adenosine triphosphate ratio (1.12ǂ.22 vs 1.74ǂ.23 in group B, P<0.01) in the hypokinetic area were all significantly reduced. It is concluded that persisting hypokinetic myocardium after NQWI combined with reduced myocellular uptake of ^99mTc-MIBI displays a reduced PCr/ATP ratio. Our results indicate that morphological remodelling after NQWI is accompanied by fundamental changes in cardiac energy metabolism.