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 greater than or equal to 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 less than 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.     

Myocardial perfusion damage after mediastinal irradiation for Hodgkin's disease: a thallium-201 single photon emission tomography study

Conflicting data have been reported on the incidence of myocardial abnormalities after mediastinal irradiation for Hodgkin's disease. We studied myocardial perfusion in 31 clinically asymptomatic patients (13 male, 18 female, mean age 35 years) 7 years (range 3–11 years) after mantle field radiotherapy. Thallium-201 tomoscintigraphic data were obtained after exercise, 4 h later and at rest (8–15 days later). Images were analysed visually and quantitatively (sectorial quantification of ²⁰¹T1 uptake on the bull's eye images of the short-axis slices) compared with those of 35 subjects with a low likelihood of coronary artery disease. Twenty-five tomographic data sets were available. Images were visually abnormal in 21 patients (84%) showing an heterogeneous ²⁰¹Tl uptake. In 68%, the sectorial ²⁰¹Tl uptake was lower than the mean ²⁰¹Tl uptake value minus 2 standard deviations measured in subjects with a low likelihood of coronary artery disease. Significant redistribution (quantitatively assessed 10%) was present in 10 patients (40%). In most of the patients, the location and the shape of the defect(s) could not be anatomically related to an epicardial coronary vessel disease. These results indicate that after mediastinal irradiation the ²⁰¹Tl myocardial uptake is frequently abnormal. The observed patterns suggest a disease of the small coronary vessels and/or the existence of a myocardial fibrosis rather than epicardial coronary artery disease.     

Quantitative thallium-201 scintigraphy after dipyridamole infusion combined with low level exercise in healthy volunteers

To establish test specific normal limits for quantitative analysis of uptake and washout of ²⁰¹Tl after dipyridamole infusion combined with low level exercise, 20 healthy volunteers were studied with low likelihood of coronary artery disease (CAD) assessed by a stepwise probability analysis based on age, sex, symptoms, resting electrocardiogram, and exercise electrocardiography. Likelihood of CAD in these volunteers was calculated as 1%. After dipyridamole infusion combined with low level exercise, one volunteer complained of headache; no other side effects were observed. There were no chest pain complaints. Maximal hemodynamic changes were achieved during the 6th and 7th min of the test. No ST segment depression was recorded. Visual analysis of the ²⁰¹Tl scintigrams was normal in all volunteers. Mean regional washout at 4 h was 44.37%±2.11%. The regional washout in the 70° LAO view (46.65%±1.10%) was significantly higher than in the anterior and 30° LAO views (43.44%±1.50% and 43.02%±1.45%, respectively). Profiles of uptake and washout of ²⁰¹Tl were different after dipyridamole infusion combined with low level exercise as compared to maximal exercise. Thus, in quantitative analysis of ²⁰¹Tl scintigraphy after dipyridamole infusion in conjunction with low level exercise as applied in the present study, it is mandatory to use normal limits of uptake and washout of ²⁰¹Tl derived from healthy volunteers who underwent the same combined protocol.     

Evaluation of myocardial function with the 201Thallium scintimetry in various diseases of the heart

To assess the validity of the quantitative ²⁰¹Tl scintimetry in various diseases of the heart (coronary heart disease with and without myocardial infarction, non-coronary cardiomyopathy, scleroderma heart disease and asymmetric septal hypertrophy with IHSS), the ²⁰¹Tl myocardial uptake values for five standardized projections (a) were correlated with the grade of LAD stenosis, (b) the pattern of myocardial wall motion and (c) were compared with the ²⁰¹Tl uptake values derived from normal patients. Significant reduction (c) of ²⁰¹Tl myocardial uptake could in individual cases be evaluated in acute myocardial infarction (95%), in dys-and akinesia (90%), in hypokinesia (71%), in scleroderma heart disease (50%), in non-coronary cardiomyopathy (50%) as well as in normokinesia (28%) when associated with LAD stenosis. The mean values (b) of ²⁰¹Tl uptake in normo-and hypokinesia significantly differed between these two groups and from those evaluated in dys-and akinesia. The latter group showed the lowest ²⁰¹Tl uptake values computed which in some cases were very close to the mean mediastinal ²⁰¹Tl uptake. The correlation (a) of individual ²⁰¹Tl values demonstrated that ²⁰¹Tl distribution in the myocardium is not only equivalent to myocardial perfusion but is corresponding with the myocardial function. In non-coronary cardiomyopathy reduced ²⁰¹Tl values sometimes could not be separated from values in coronary heart disease (and myocardial infarction). A regional increase of myocardial mass as in septal hypertrophy correlated well with an augmented ²⁰¹Tl uptake when referred to the ²⁰¹Tl storage in the mediastinum.Dedicated to Prof. Dr. F.E. Stieve, Berlin, on the occasion of his 60th birthday     

The two-view radionuclide ventriculogram. Advantages of the LPO view.

This report is a prospective study of 33 male patients who underwent both contrast ventriculography (CVG) and radionuclide ventriculography (RVG) within a 24-hour period. Expert, blinded observers graded the left ventricle's regional wall motion (RWM) in the left anterior descending (LAD), left circumflex (LCx), and posterior descending arterial (PDA) distributions on right anterior oblique (RAO), and left anterior oblique (LAO) CVGs, and on anterior (ANT), LAO, 70 degrees left anterior oblique (LAO70), and left posterior oblique (LPO) RVGs. When statistically compared with CVG RWM standard data, RVG studies composed of LAO and LPO views were equal to the RVG studies composed of ANT, LAO, and LAO70 views in assessment of the LAD and LCx distributions. The RVG with LAO and LPO views was superior to the RVG with ANT, LAO, LAO70 in the detection of the posterior descending artery RWM. The authors conclude that accurate assessment of RWM is efficiently performed with the RVG composed of LAO and LPO views.     

Usefulness of resting thallium-201 delayed imaging for detecting myocardial viability in patients with previous myocardial infarction

To test the feasibility of resting thallium-201 (²⁰¹Tl) initial and delayed scintigraphy for detecting the area of viable myocardium, we performed single photon emission computed tomography (SPECT) in 57 patients with previous myocardial infarction (MI). All had received coronary arteriography (CAG) and left ventriculography (LVG). Initial and delayed myocardial imagings were carried out 10 min and 2 hours, respectively, after the injection of²⁰¹Tl at rest. Redistribution was judged by visual interpretation and/or the circumferential profile curve, and found in the infarcted or its adjacent area in 40 of the 57 cases (70.2%). A negative washout (net increase of²⁰¹Tl uptake in delayed image) was detected in 17 of these 40 cases. In 10 of the 57 patients, both exercise and rest-injected²⁰¹Tl myocardial images were obtained at exercise and rest, and compared visually. The areas of abnormal perfusion were smaller in the resting delayed images than those seen after exercise in 9 of the 10 cases, and were equal in one case. Thus, resting²⁰¹Tl delayed myocardial scintigraphy appears to reduce the underestimation of the size of the viable myocardium by the usual²⁰¹Tl images obtained after exercise or by single initial images obtained at rest in patients with previous MI.     

Comparison of 201Tl SPET and treadmill exercise testing in patients with Kawasaki disease

About 4% of children with Kawasaki disease ultimately develop ischaemic heart disease. Therefore, the early detection, non-invasive monitoring and long-term follow-up of myocardial ischaemia are essential. We compared the sensitivity and specificity of 201Tl single photon emission tomography (SPET) and treadmill exercise in the detection of myocardial ischaemia in 23 patients (19 boys, 4 girls) with Kawasaki disease. They were divided into two groups according to the results of coronary angiography. Group I consisted of 11 patients with coronary abnormalities; Group II consisted of 12 patients with no coronary abnormalities. The sensitivity, specificity, false-positive and false-negative rates for detecting coronary arterial lesions were 72.7% (8/11), 58.3% (7/12), 38.5% (5/13) and 30% (3/10) for 201Tl SPET, and 45.5% (5/11), 100% (12/12), 0% (0/5) and 33.3% (6/18) for treadmill exercise, respectively. We conclude that 201Tl SPET is more sensitive than treadmill exercise for the detection of coronary arterial abnormalities, but that the specificity of treadmill exercise is better than that of 201Tl scintigraphy. Coronary artery lesions detected by coronary angiography have good concordance of ischaemic areas with perfusion defects detected by 201Tl SPET. When ischaemic findings on 201Tl SPET and/or positive treadmill exercise testing are noted, coronary angiography is strongly indicated to detect possible stenotic lesions in the coronary arteries.     

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.     

Thallium-201 single photon emission tomography of myocardium: Additional information in reinjection studies is dependent on collateral circulation

A second thallium-201 injection under resting conditions is able to improve the differentiation between myocardial scar and ischaemia when compared with simple redistribution imaging. The aim of this study was to evaluate the dependence of this improvement on the degree of stenosis and the presence of collaterals. Single photon emission tomography (SPET) studies under exercise, redistribution and reinjection conditions were performed on 84 patients with 181 stenotic vessels (70 left anterior descending, 47 left circumflex, 64 right coronary artery) and compared with angiography. An improvement of the ²⁰¹Tl uptake in the reinjection image was observed in 53% of the myocardial areas served by a coronary artery with a stenosis of over 90%. This is compared with 13% of the areas served by a vessel with a stenosis between 50% and 90%. 90% of the collateralized areas showed a fill-in effect, but only 7 of the 118 without angiographically visible collateralization (6%). The dependence of the fill-in effect, collateralization and stenosis was highly significant (² test, p < 0.0001). In our patient group, there was much greater benefit from the reinjection study in vessels with a > 90% narrowing. The fill-in effect was closely correlated to the presence of collaterals. In these cases, the fill-in may be an indication for hibernating myocardium. Offprint requests to: P. Bartenstein     

201Tl-redistribution analysis in early and delayed myocordial scintigrams of patients with coronary heart disease (CHD)

Scans were performed on 8 healthy subjects and 25 with coronary heart disease proven by angiography and ventriculography including 6 with previous myocardial infarction at rest, exercise, and 1 and 2 h after exercise. Data were collected by a gamma camera interfaced to a data collection system. In healthy subjects ²⁰¹Tl distribution was homogeneous at rest and after exercise, the count rate ranging between 100%—as set in the region of maximum—and 80% over other regions of myocardium. In 19 patients with coronary heart disease it was uniform only at rest; 6 patients with previous myocardial infarction had locally diminished ²⁰¹Tl uptake even at rest. In patients with coronary heart disease without previous myocardial infarction, scans made immediately after exercise showed significant ²⁰¹Tl hypofixation in region of minimum, the count rate of which was less than 80% of the count rate as determined over region of maximum, ²⁰¹Tl uptake. Scans made 1 and 2 h after exercise had filling-in of ²⁰¹Tl within the region of minimum the count rate of which returned to the normal range of at least 80% of the count rate measured over region of maximum uptake. This return to resting distribution was called ²⁰¹Tl redistribution. Six patients with coronary heart disease and previous myocardial infarction had ²⁰¹Tl defects larger after exercise than at rest, without redistribution being observed. Redistribution in late postexercise scans is a sign of reversible ischemia in coronary heart disease. Scans at rest may be omitted in coronary heart disease, because transient ischemia is undetectable, unless spontaneous angina occurs during scan procedure.     

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.     

Comparison of technetium 99m Q12 and thallium 201 for detection of angiographically documented coronary artery disease in humans

Background

^99mTc-labeled Q12 (^99mTc-Q12) is a new imaging agent that produces myocardial visualization in humans. This study examined the hypothesis that a 100-minute rest-exercise tomographic imaging protocol after injection of^99mTc-Q12 can be used to detect the presence or absence of coronary artery stenoses.

Methods and Results

Imaging with²⁰¹Tl and^99mTc-Q12 was performed in 20 patients with angiographically documented coronary artery disease and 10 “normal” subjects including two patients with chest pain and normal coronary arteriograms and eight subjects with a very low likelihood of occlusive coronary disease.^99mTc-Q12 was imaged beginning 15 minutes after injection at rest and with exercise. In the 20 patients, a corresponding myocardial defect was detected in blinded fashion in 18 with²⁰¹Tl and 17 with^99mTc-Q12 (difference not significant). Of 10 patients without evidence of coronary disease, nine had a normal²⁰¹Tl scan and eight had a normal^99mTc-Q12 scan (difference not significant). Agreement of^99mTc-Q12 and²⁰¹Tl imaging for detection of regional myocardial perfusion defects was excellent (κ=0.88). Identification of the presence or absence of angiographically documented coronary disease in individual coronary artery distributions was 80% and 82% for²⁰¹Tl imaging and 73% and 87% for^99mTc-Q12 (difference not significant).

Conclusion

^99mTc-Q12, used in a rest-exercise sequence that can be completed in 100 minutes, provided identification of regional myocardial perfusion defects similar to that of²⁰¹Tl.     

Quantification of myocardial ischemia and infarction with single photon emission computed tomography

To evaluate the feasibility of ²⁰¹Tl single photon emission computed tomography (SPECT) for quantitative detection of myocardial infarction and ischemia, scintigraphic studies were related to angiographic findings. In study A infarct sizes with SPECT were compared with the angiographic infarct sizes of 30 patients. A linear correlation was found for the % infarct of the left ventricular circumference between both methods (r=0.73; P< 0.001; mean infarct size 20.7%±10.5% (angio) vs 19.8%±12.9% (SPECT), mean±SD). Furthermore, a significant inverse correlation between scintigraphic infarct size and left ventricular ejection fraction (r=-0.87, P< 0.001) was obtained. In study B exercise/rest ²⁰¹Tl SPECT was used for quantification of myocardial ischemia. Forty-three patients underwent both stress ²⁰¹Tl SPECT and biplane exercise left ventriculography. Ischemia was expressed as % defect size of the left ventricular circumference. Sensitivity and specificity for detection of ischemia were 96% and 100% respectively with stress SPECT. Extent of myocardial ischemia correlated significantly with both methods (r=0.63; SPECT defect=1.0 angiographic ischemia +2%; P< 0.001). The regression followed the line of identity and the mean sizes of ischemia were identical (SPECT 12.2±7.6% vs 14.6±12.4% ventriculography, mean±SD) demonstrating the agreement of both methods. However, there was some intraindividual variance between the scintigraphic and the angiographic study. The sensitivity and specificity in single regions with SPECT were lower compared to the global test results. The correlation between the non invasive SPECT and the ventriculography in detection of myocardial infarction and ischemia indicates the clinical value of ²⁰¹Tl SPECT for diagnosis of coronary heart disease.Parts of the results were presented at the 58th sessions of the American Heart Association at Washington, DC (1985)     

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.     

Technetium-99m Q4: a prototype cationic perfusion radiotracer with myocardial washout

Technetium-99m Q4 is derived from an existing mixed ligand myocardial tracer (^99mTc-Q3) by the addition of an ester group to promote myocardial washout. Six subjects with single-vessel coronary disease documented by angiography and/or Q wave myocardial infarction documented by electrocardiography were studied with ^99mTc-Q4 injection during exercise and with comparative thallium-201 tomography. Six healthy volunteers were also studied with ^99mTc-Q4 imaging following injection at peak exercise. Tomographic images with ^99mTc-Q4 and ²⁰¹Tl each provided correct assessment of the presence or absence of coronary disease in 22 of 30 myocardial segments (73.3%). Six myocardial segments showed defect reversibility with ^99mTc-Q4, whereas 14 segments showed reversibility with ²⁰¹Tl, but the latter included three segments with no angiographic or electrocardiographic evidence of disease. In both normals and subjects with coronary artery disease, significant global washout of ^99mTc-Q4 was observed over 4 h. For five patients with angiographic evidence of unrevascularized coronary artery stenosis, the ischemic to normal zone count ratio increased from 0.782±0.107 at 45 min postexercise to 0.891±0.115 at 4 h postexercise (P = 0.016), suggesting occurrence of differential washout. It is concluded that addition of an ester group functionality to a previously studied mixed ligand cardiac tracer promotes global and regional myocardial tracer washout. Nevertheless, demonstration of perfusion defect reversibility with comparable frequency to that observed with ²⁰¹Tl stress and reinjection images, required separate injections of ^99mTc-Q4 at peak stress and at rest. Received 4 October and in revised form 19 December 1997     

Thallium-201 single photon emission computed tomography in patients with symptoms of heart disease and non-significant coronary artery lesions

Polar presentations of coronary angiograms and myocardial 201Tl SPECT were compared in 44 patients without significant coronary artery disease (less than 50% stenosis at angiography). Regions of reduced isotope activity (defects) were present in 18 patients (41%). Nine of these had angiographic and/or clinical evidence of non-coronary heart disease, such as documented or suspected myocardial infarction, dilated cardiomyopathy or other myocardial diseases. Such defects could be caused by impaired small vessel blood flow, abnormalities in cell membrane transport or relative differences in left ventricular wall thickness. In 9 patients defects were probably due to attenuation artifacts. Defects in patients with heart diseases were significantly larger than in those without obvious disease. The information content in coronary angiography and 201Tl SPECT overlap but are not congruent. Coronary angiography describes morphology of large coronary vessels, whereas 201Tl SPECT contains information of large and small vessel perfusion as well as membrane transport of 201Tl ions.     

Do β-blockers affect the diagnostic sensitivity of dobutamine stress thallium-201 single photon emission computed tomographic imaging?

Background  The effects of β-blockers on dobutamine stress ²⁰¹Tl tomographic imaging are not known. This study was undertaken to examine whether β-blockers affect the sensitivity of dobutamine stress ²⁰¹Tl imaging. Methods and Results  One hundred ten patients without previous myocardial infarction underwent dobutamine stress ²⁰¹Tl single photon emission computed tomography (SPECT) and coronary arteriography, both studies within a 1-week period. Dobutamine was infused at rates of 5, 10, 20, 30, and 40 μg/kg/min in 3-minute stages. Atropine (as much as 1 mg) was injected intravenously when the patient’s heart rate was <100 beats/min. Patients in group 1 (n=72) were receiving β-blockers and patients in group 2 (n=38) were not. The SPECT images in group 1 showed perfusion abnormalities in 62%, 87%, and 94% of patients with one-, two-, and three-vessel coronary artery disease (≥50% diameter stenosis), respectively, compared with 75%, 71% and 100% in group 2 (p not significant). The overall sensitivities were 82% (37 of 45) in group 1 and 80% (16 of 20) in group 2 (p not significant). The specificities were 81% (22 of 27) in group 1 and 83% (15 of 18) in group 2 (p not significant). The overall accuracies were the same for both groups (82%). Atropine was added more often in group 1 than in group 2 (37/72 vs 5/38, p<0.001). Conclusions  Our results suggest that β-blockers do not affect the sensitivity, specificity, and accuracy of dobutamine stress ²⁰¹Tl SPECT imaging for detecting coronary artery disease if atropine is given when the chronotropic response is inadequate. In patients receiving β-blockers, however, the addition of atropine to dobutamine stress is more frequently required.     

Amplitude analysis of stress technetium-99m methoxy isobutylisonitrile images in coronary artery disease.

To determine the role of rest and stress gated technetium-99m methoxyisobutylisonitrile (sestamibi), in the detection of coronary artery disease, routine Fourier analysis of these images was performed with the best septal left anterior oblique (LAO) position of 20 patients (17 men, 3 women; aged 40-75 years) who also underwent rest or redistribution/stress single photon emission tomography (SPET) (99mTc-sestamibi and Thallium-201), gated blood pool imaging and coronary angiogram. There were 6 patients with single-vessel disease, 6 with two-vessel disease, 4 with three-vessel disease, 2 with coronary spasms, 1 with a patent graft and 1 with anginal episodes but a normal angiogram result. Three normal volunteers (2 women, 1 man; aged 24-26 years) also had rest and stress gated blood pool as well as rest and stress gated 99mTc-sestamibi imaging. Rest and stress 99mTc-sestamibi amplitude and phase images depicted regional myocardial wall shortening from the outer layer of the myocardium to the center of the left ventricle as follows: a high amplitude halo of maximal negative count rate variation; a circular thinner halo of negligible amplitude; a central region of maximal positive count rate variation, as the images evolved from end-diastole to end-systole. Similar patterns with regional differences represented abnormal myocardial wall shortening. 99mTc-sestamibi and 201Tl SPET images were in agreement in 90% of the patients and 92% of myocardial regions. 201Tl SPET detected 83% of angiographically proven lesions, as compared with 80% for 99mTc-setamibi SPET and 80% for the amplitude images. The amplitude images demonstrated a larger number of other abnormalities not predicted on the angiogram, probably because they were able to detect regions with a potential for flow improvement and transient regional wall shortening abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dipyridamole and exercise SPET provide different estimates of myocardial ischaemic areas: role of the severity of coronary stenoses and of the increase in heart rate during exercise

In patients unable to perform a maximal exercise test, dipyridamole single-photon emission tomography (SPET) has a higher capacity than exercise SPET to detect coronary artery disease (CAD). However, in patients with myocardial ischaemia who are able to perform a maximal exercise test, it is not known whether these two tests may be equally used to assess the areas of myocardial ischaemia. This study was aimed at comparing the results provided by dipyridamole and exercise SPET in CAD patients with documented exercise myocardial ischaemia. Forty CAD patients who had undergone exercise thallium-201 SPET and who had myocardial ischaemia documented by an unequivocally positive exercise test underwent an additional ²⁰¹Tl SPET study after dipyridamole infusion and low-level (40 W) exercise. The extent of defects was compared between the two tests and predictors of discrepant results were sought among data from exercise testing and coronary angiography. The extent of SPET defects was equivalent between the two tests in only 11 patients (28%), larger defects being observed with exercise in 18 [average difference: 12%±5% of left ventricle (LV)] and with dipyridamole in 11 (average difference: 15%±11% of LV). The best independent predictors of discrepancies between the two tests were: (1) increase in heart rate at exercise SPET, with defects being smaller at exercise than after dipyridamole in none of the patients with an increase >60 bpm (0/14), but in 42% of the others (11/26; P=0.004); and (2) an ischaemic territory related to a <70% coronary stenosis, for which SPET defects were always induced at exercise (10/10) but in only 30% (3/10) with dipyridamole (P=0.0004). Exercise and dipyridamole SPET provide different estimates of myocardial ischaemic areas. Dipyridamole allows the unmasking of perfusion abnormalities in patients who have low increases in heart rate at exercise SPET. However, dipyridamole is also much less efficient at inducing perfusion abnormalities in the ischaemic areas supplied by coronary stenoses of intermediate severity at rest angiography. Received 20 January 2000 and in revised form 18 March 2000     

Routine exercise testing or thallium-201 scintigraphy for prediction of cardiac events post-myocardial infarction?

The efficacy of 12 lead exercise testing and rest/exercise ²⁰¹Tl scintigraphy as indicators of coronary anatomy and prognosis was compared in 46 low risk survivors of acute myocardial infarction. The non invasive procedures were performed at discharge, and cardiac catheterization was performed six weeks post discharge. On exercise testing, ST depression in leads remote from the site of infarction was considered to indicate multivessel disease and reversible ischaemia. On ²⁰¹Tl scintigraphy, a perfusion defect remote from the site of infarction indicated multivessel disease, while a defect which reperfused at rest indicated reversible ischaemia. During the mean follow-up of 13±3 months, 14(30%) patients experienced cardiac events. Thallium scintigraphy was a more sensitive, but less specific, indicator of multivessel disease than exercise testing. Both exercise testing and ²⁰¹Tl scintigraphy had a similar sensitivity (79% vs 79%), specificity (78% vs 88%) and predictive accuracy (78% vs 85%) for predicting subsequent cardiac events. Thus, in our patient population, ²⁰¹Tl scintigraphy could not be demonstrated to be superior to routine exercise testing in low risk patients post myocardial infarction.