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

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

Worsening of left ventricular ejection fraction induced by dipyridamole on Tl-201 gated myocardial perfusion imaging predicts significant coronary artery disease

BACKGROUND: Vasodilator stress on myocardial perfusion imaging has been found to induce ischemic stunning, which may present as transient worsening of left ventricular ejection fraction (LVEF) or regional wall motion abnormality. This study aimed to evaluate the significance of stress-induced worsening of LVEF in the diagnosis of coronary artery disease (CAD) on dipyridamole thallium 201 gated single photon emission computed tomography (SPECT). METHODS AND RESULTS: The study included 126 patients who underwent dipyridamole Tl-201 gated SPECT and coronary angiography within 3 months. Poststress and 4-hour rest images were obtained, and LVEF was calculated by use of automated software (QGS 3.0). A decrease in LVEF of 6% or greater from rest to poststress was considered significant, and this threshold was determined by the serial reproducibility assessment of Tl-201 gated SPECT. If worsening of LVEF was used as the criterion for detecting significant CAD (> or = 70% coronary stenoses in > or = 1 vessel), the sensitivity, specificity, positive predictive value, and negative predictive value were 35%, 93%, 90%, and 44%, respectively. CONCLUSION: Dipyridamole-induced worsening of LVEF, as shown by Tl-201 gated SPECT, is a valuable nonperfusion marker of significant CAD. Although the sensitivity of LVEF worsening in detecting significant CAD is only 35%, the specificity is as high as 93%.     

201Tl定量门控心肌灌注体层显像与99mTc-红细胞门控心血池显像测定左心室射血分数的对比研究

目的 探讨201Tl定量门控心肌灌注体层显像与99mTc-红细胞门控心血池显像测量左心室射血分数(LVEF)的相关性.方法 72例受检者接受201Tl静息门控心肌灌注体层显像,用AUTOQUANT 4.21软件测量LVEF,并与24 h内的静息99mTc-红细胞平衡法门控心血池显像结果进行比较.结果 ①门控心肌灌注体层显像与门控心血池显像测量LVEF值的结果呈明显正相关(r=0.554,P=-0.000),两种方法无统计学差别(t=1.194,P＞0.05).②不同疾病组之间两种测量方法无统计学差异(P值均大于0.05).③门控心肌灌注体层显像及门控心血池显像测量的LVEF值分别为(64.68±10.77)%和(62.46±8.99)%,门控心肌灌注体层显像测量的LVEF值要比门控心血池显像高出3.55%.结论 201Tl门控心肌灌注体层显像与99mTc-红细胞门控心血池显像测量LVEF值的相关性好且结果准确,但门控心肌灌注体层显像的LVEF测量值要稍高于门控心血池显像.     

Left ventricular ejection fraction and volumes on rest gated 201Tl perfusion SPECT: comparison with two-dimensional echocardiography

BACKGROUND: Rest gated 201Tl images are considered to be of poor count statistics due to lower energy and low photon flux of 201Tl in addition to increased attenuation and low dose that can be administered. We compared the left ventricular ejection fraction (LVEF), end diastolic (EDV) and end systolic volume (ESV) obtained on 4 h gated rest 201Tl myocardial perfusion single photon emission computed tomography (SPECT) with those obtained by two-dimensional echocardiography (2-D ECHO) in patients with known or suspected coronary artery disease (CAD). METHODS: Eighty-two consecutive patients who underwent gated 201Tl stress-rest myocardial perfusion SPECT and 2-D ECHO were studied. The gated thallium images were processed with Siemens e-soft autocardiac processor and LVEF, EDV and ESV were evaluated using Emory Cardiac Toolbox. The same parameters were also assessed on the 2-D ECHO using the modified Simpson method for comparison. RESULTS: Out of 82 rest gated images, one study was excluded because of poor count statistics. In 81 (99%) patients there was good linear correlation with 2-D ECHO values and rest gated 201Tl SPECT images for EDV, ESV and LVEF. Pearson's correlation co-efficient (r value) for EDV, ESV and LVEF between the two methods was 0.78, 0.79 and 0.88, respectively. A Bland-Altman plot showed close agreement with LVEF but not for EDV and ESV. CONCLUSION: These results suggest that the 4 h rest gated 201Tl study gives a reliable value for the LVEF compared to 2-D ECHO and can be used in routine clinical practice.     

201Tl and 99mTc-MIBI gated SPECT in patients with large perfusion defects and left ventricular dysfunction: comparison with equilibrium radionuclide angiography.

Left ventricular ejection fraction (LVEF) is a major prognostic factor in coronary artery disease and may be computed by 99mTc-methoxyisobutyl isonitrile (MIBI) gated SPECT. However, 201Tl remains widely used for assessing myocardial perfusion and viability. Therefore, we evaluated the feasibility and accuracy of both 99mTc-MIBI and 201Tl gated SPECT in assessing LVEF in patients with myocardial infarction, large perfusion defects and left ventricular (LV) dysfunction. METHODS: Fifty consecutive patients (43 men, 7 women; mean age 61 +/- 17 y) with a history of myocardial infarction (anterior, 26; inferior, 18; lateral, 6) were studied. All patients underwent equilibnum radionuclide angiography (ERNA) and rest myocardial gated SPECT, either 1 h after the injection of 1110 MBq 99mTc-MIBI (n = 19, group 1) or 4 h after the injection of 185-203 MBq 201Tl (n = 31, group 2) using a 90 degrees dual-head camera. After filtered backprojection (Butterworth filter: order 5, cutoff 0.25 99mTc or 0.20 201Tl), LVEF was calculated from reconstructed gated SPECT with a previously validated semiautomatic commercially available software quantitative gated SPECT (QGS). Perfusion defects were expressed as a percentage of the whole myocardium planimetered by bull's-eye polar map of composite nongated SPECT. RESULTS: Gated SPECT image quality was considered suitable for LVEF measurement in all patients. Mean perfusion defects were 36% +/- 18% (group 1), 33% +/- 17% (group 2), 34% +/- 17% (group 1 + group 2). LVEF was underestimated using gated SPECT compared with ERNA (34% +/- 12% and 39% +/- 12%, respectively; P = 0.0001). Correlations were high (group 1, r= 0.88; group 2, r = 0.76; group 1 + group 2, r = 0.82), and Bland-Altman plots showed a fair agreement between gated SPECT and ERNA. The difference between the two methods did not vary as LVEF, perfusion defect size or seventy increased or when the mitral valve plane was involved in the defect. CONCLUSION: LVEF measurement is feasible using myocardial gated SPECT with the QGS method in patients with large perfusion defects and LV dysfunction. However, both 201Tl and 99mTc-MIBI gated SPECT similarly and significantly underestimated LVEF in patients with LV dysfunction and large perfusion defects.     

Overestimation of postischemic myocardial stunning on gated SPECT imaging: Correlation with echocardiography

Background  Postischemic global and regional left ventricular (LV) dysfunction on stressgated single photon emission computed tomography (SPECT) imaging is attributed widely to myocardial stunning. We sought to determine the specificity of gated SPECT for the detection of myocardial stunning after ischemic stress. Methods and Results  Twenty-seven patients with an ischemic response to stress on dual-isotope exercise SPECT were enrolled prospectively. Transthoracic echocardiography was performed just before stress gated SPECT for assessment of regional wall motion and quantitative LV ejection fraction (LVEF). The 17 myocardial segments for each patient were scored for myocardial perfusion by stress gated SPECT, and regional wall motion by stress gated SPECT and echo. Of the 459 myocardial segments, 41% had perfusion defects, 15% had stress gated SPECT regional wall motion abnormality, 4.8% had poststress echo regional wall motion abnormality, and 3.9% had baseline regional wall motion abnormality. Overall, a stress gated SPECT regional wall motion abnormality had a sensitivity of 100% and a specificity of 89%. Among reversible perfusion defects of moderate severity or more, a stress gated SPECT regional wall motion abnormality had a specificity of 41% and a positive predictive value of 8%. Stress gated SPECT LVEF was similar to poststress echo LVEF for all patients, but significantly lower in patients with reversible perfusion defects of moderate severity or more. Conclusion  Post-stress gated SPECT imaging overestimates global and regional myocardial stunning. Caution should be exercised in interpreting poststress global or regional LV function on stress gated SPECT in scans with reversible ischemia.     

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.     

Myocardial tracking, a new method to calculate ejection fraction with gated SPECT: validation with (201)Tl versus planar angiography.

Left ventricular ejection fraction (LVEF) and viability are essential variables for the prognosis of myocardial infarction and can be measured simultaneously by (201)Tl gated SPECT; however, most algorithms tend to underestimate LVEF. This study aimed to evaluate a new myocardial tracking algorithm, MyoTrack (MTK), for automatic LVEF calculation. METHODS: A rest/redistribution (20 min/4 h) (201)Tl gated SPECT protocol followed immediately by a (99m)Tc equilibrium radionuclide angiography (ERNA) was performed in 75 patients with history of myocardial infarction. Quality of myocardial uptake was evaluated from count statistics and automatic quantification of defect sizes and severities (CardioMatch). LVEFs were calculated both with Germano's quantitative gated SPECT (QGS) algorithm and with MTK. Briefly, the originality of this algorithm resides in the unique end-diastole segmentation, matching to a template and motion field tracking throughout the cardiac cycle. RESULTS: ERNA LVEF averaged 33% +/- 14%. QGS significantly underestimated this value at 20 min (30% +/- 13%, P < 0.001) and at 4 h (30% +/- 13%, P < 0.0001). By contrast, MTK did not miscalculate LVEF at 20 min (34% +/- 14%, probability value was not significant) though a similar underestimation occurred at 4 h (31% +/- 13%, P < 0.02). Individual differences between early and late gated SPECT values and differences between gated SPECT and ERNA values did not correlate with the extension of perfusion defects, count statistics, or heart rate. CONCLUSION: MTK algorithm accurately calculates LVEF on early/high-count images compared with ERNA [corrected], even in patients with severe perfusion defects, but tends to underestimate LVEF on delayed/low-contrast images, as other algorithms do.     

Correct spatial normalization of myocardial perfusion SPECT improves detection of multivessel coronary artery disease

BACKGROUND: This study sought to improve the detection of multivessel coronary artery disease (CAD) with the use of rest and exercise single photon emission computed tomography (SPECT) perfusion scintigraphy by developing a processing scheme, which provides proper regional normalization of the images for interpretation. When SPECT perfusion images are interpreted, one area of myocardium serves as "normal." We hypothesized that if this "normal" region changes location from rest to stress, the stress images must be adjusted for proper interpretation. By taking into account the level of tracer activity in this "normal" area on the resting images, we could more accurately identify patients with multivessel CAD.Methods and results Dual-isotope rest (thallium 201) and exercise dobutamine or adenosine stress (technetium 99m sestamibi) perfusion SPECT studies were examined in 258 patients with 2- or 3-vessel CAD on coronary arteriography performed within 6 months of each other (mean interval, 19 days). If a shift in regional location of the "normal" segment from rest to stress was present, the images were (1) interpreted in the usual fashion for the number of vessels with ischemia (PRE-NORM) and (2) reinterpreted after quantitative normalization (ie, adjusting the display window until the intensity of the "normal" segment was matched at rest and stress [POST-NORM]). Interpretation was performed with blinding to arteriographic results. An angiographic stenosis was defined as luminal diameter stenosis greater than 50%. Three control groups comprising (1) single-vessel CAD (n = 119), (2) no significant angiographic CAD (n = 118), and (3) a normalcy group of low pre- and post-test probability of CAD (n = 44) were also studied to determine the incidence of false-positive results induced by the renormalization technique. A shift in the "normal" segment occurred in 81 studies of 258 patients (31%), 80 of which were read as abnormal PRE-NORM (sensitivity, 99%); however, for their 216 stenosed vessels, only 143 were detected PRE-NORM (vessel sensitivity, 66%; accuracy, 65%). The mean POST-NORM change in the display was 11%. POST-NORM, all 82 patients' studies were interpreted as abnormal (sensitivity, 100%), and 196 of 216 vascular territories were abnormal (vessel sensitivity, 91%; accuracy, 83%; both P <.0001 vs PRE-NORM). In the single-vessel disease, no significant disease, and normalcy groups, 19 of 119, 15 of 118, and 11 of 44 patients, respectively, demonstrated a shift in the peak pixel location. However, there were no significant changes in single-vessel sensitivity, angiographic specificity, or normalcy in these patients. CONCLUSIONS: With multivessel CAD, the "normal" region on SPECT often changes in location from rest to stress, potentially masking the extent and severity of multivessel ischemia. Renormalization of the images to match their resting level before image interpretation allows diagnosis of contralateral ischemia and strikingly improves the detection of multivessel CAD, without a substantive loss in specificity.     

Thallium gated SPECT: relation between immediate post-stress evolution of ejection fraction and severity of perfusion pattern

BACKGROUND AND AIMS: A significant decrease of left ventricular ejection fraction (LVEF) at stress has been reported with 99Tc(m) gated single-photon emission computed tomography (gSPECT) in severe myocardial stunning up to 1 h after exercise. This study was designed to show whether 201Tl gSPECT can measure LVEF evolution from rest to stress in routine examination and give additional information to perfusion interpretation since acquisition starts immediately after stress test. METHODS: Post-exercise and rest 201Tl gSPECT were performed in 187 patients with suspected coronary artery disease. Myocardial perfusion was quantified by 20-segment analysis. Patients were divided into four groups according to their summed perfusion score, reversibility rate and electrocardiographic findings, i.e. in order of severity: I = normal perfusion, II = fixed defect owing to a myocardial infarction, III = full reversible ischaemia, and IV = partial reversible ischaemia. LVEF was calculated by Germano's automatic algorithm. RESULTS: Normal subjects (n = 29) and infarcted patients (n = 34) showed a significant LVEF increase between rest and stress, +7 +/- 9% and +5 +/- 7% respectively. In full reversible ischaemic patients (n = 46), stress LVEF showed no increase (+1 +/- 8%) and this group was statistically different from both group I and group II. Furthermore, when ischaemia was partially reversible (n = 31), LVEF decreased significantly (-3 +/- 8%), particularly when exercise tests were abnormal (-4 +/- 8%). Group IV was statistically different from groups I and II. CONCLUSIONS: Good agreement exists between the severity of ischaemic perfusion pattern and LVEF degradation at stress, which is consistent with previously published data using 99Tc(m) gSPECT. Additionally, the use of 201Tl for immediate post-exercise imaging allows the observation of a physiological LVEF increase in normal and infarcted patients.     

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.     

Accuracy of exercise stress technetium 99m sestamibi SPECT imaging in the evaluation of the extent and location of coronary artery disease in patients with an earlier myocardial infarction

BACKGROUND: This study assessed the accuracy of exercise methoxy isobutyl isonitrile (MIBI) single photon emission computed tomography (SPECT) in the evaluation of the extent of coronary artery disease (CAD) in patients with an earlier myocardial infarction. METHODS AND RESULTS: We studied 135 patients (mean age, 57+/-10 years; 115 men) at a mean of 4.1 years (median, 1 year) after myocardial infarction with symptom-limited bicycle exercise stress and rest MIBI SPECT imaging. Coronary angiography was performed within 3 months. Significant CAD was defined as a stenosis of 50% or larger in luminal diameter in 1 or more major coronary arteries. Myocardial perfusion defects (fixed, reversible, or both) were detected in 107 of the 113 patients with significant CAD and in 10 of the 22 patients without significant CAD (sensitivity, 95%; CI, 91 to 99; specificity, 55%; CI, 46 to 63, and accuracy, 88%; CI, 82 to 94). The specificity rate increased to 73% (CI, 65 to 80) by using only reversible perfusion defects as a means of predicting CAD. Reversible perfusion abnormalities were more frequent in patients with multivessel CAD than in patients with single-vessel CAD (51 of 64 [80%] vs. 27 of 49 [55%], P<.01). Myocardial perfusion abnormalities in 2 vascular regions, which is suggestive of multivessel CAD, were detected in 35 of the 64 patients with and in 9 of the 71 patients without multivessel CAD (sensitivity for detecting CAD in more than one vascular region, 55%; CI, 46 to 63, specificity, 87%; CI, 81 to 93, and accuracy, 72%; CI, 64 to 80). The sensitivity rates for the diagnosis of left anterior descending coronary artery, left circumflex, and right coronary artery based on any defect were 80%, 70%, and 63%, respectively. The corresponding specificity rates were 70%, 76%, and 73%, respectively. CONCLUSIONS: Exercise MIBI SPECT imaging is an accurate method for the diagnosis and localization of CAD in patients with an earlier myocardial infarction. The technique provides a high specificity and moderate sensitivity for the diagnosis of multivessel CAD on the basis of myocardial perfusion abnormalities in more than 1 vascular region.     

Assessment of ejection fraction with Tl-201 gated SPECT in myocardial infarction: Precision in a rest-redistribution study and accuracy versus planar angiography

BACKGROUND. Viability and left ventricular ejection fraction (LVEF) are essential measures for the assessment of myocardial infarction (MI). These 2 variables may be evaluated simultaneously by means of thallium-201 gated single photon emission computed tomography (SPECT); however, the precision and accuracy of LVEF measurements with this isotope remain controversial, particularly in cases of extended perfusion defects and poor count densities. METHODS AND RESULTS. Fifty patients with a history of MI underwent a 20-minute rest and a 4-hour redistribution Tl-201 gated SPECT viability protocol, immediately followed by a technetium-99m planar equilibrium radionuclide angiography (ERNA). On gated SPECT images, various count statistics were calculated, and perfusion was automatically quantified by means of CardioMatch, which provided both the size and severity of MI defects. Rest and redistribution LVEFs were determined from gated SPECT with Germano's algorithm, whereas LVEFs were calculated from ERNA using the manufacturer's software. Mean LVEF values calculated with rest gated SPECT, redistribution gated SPECT, and planar ERNA were 30% +/- 13%, 30% +/- 13% and 33% +/- 13%, respectively. Significant differences between repeated gated SPECT LVEFs were not shown by means of the paired t test. Correlation coefficients were high between 20-minute and 4-hour scans (r = 0.89) and between gated SPECT and ERNA (r = 0.88 and r = 0.92 at 20 minutes and 4 hours, respectively). Additionally, close agreement between gated SPECT and ERNA was shown by means of the Bland-Altman plot, despite an underestimation of 3 units. Finally, neither the technical conditions (count density, heart rate, lung uptake, etc) nor the perfusion alteration (size, severity, redistribution) appeared to interfere with the precision and accuracy of gated SPECT LVEF measurement. CONCLUSION. Tl-201 gated SPECT is a precise method for assessing LVEF within the same patient at 4-hour intervals, even with a substantial count decay, and it gives accurate results compared with planar ERNA, even in the case of large perfusion defects.     

Post-stress end-systolic left ventricular dilation: a marker of endocardial post-ischemic stunning

Several studies have shown the accuracy of gated single photon emission computed tomography (SPECT) using thallium-201 and technetium tracers in the assessment of myocardial perfusion and function. Gated SPECT has been successfully utilized to detect post-stress left ventricular ejection fraction (LVEF) reduction resulting from post-ischemic stunning in patients with coronary obstruction. The aim of this study was to evaluate whether the post-stress LVEF impairment could be related to the post-stress end-systolic ventricular dilation resulting from post-ischemic endocardial stunning. Two hundred and eighty-two consecutive patients were studied by conventional diagnostic 2 day stress/rest gated SPECT following injection of 925 MBq of 99mTc-tetrofosmin using a dual-headed SPECT camera. One hundred and forty-seven of these patients (52%) showed reversible perfusion defects, 69 (24%) permanent defects and the remaining 66 (24%) had normal perfusion. One hundred and thirty-eight of these patients had a history of myocardial infarction (MI) and 19% underwent coronary angiography without an intervening cardiac event. Perfusion was analysed on ungated images using 20 segments scored on a five-point scale (0, normal; 4, no uptake), while wall thickening (WT) was assessed visually on stress/rest end-systolic images using a four-point score (0, normal; 3, absence of WT). LVEF and volumes were calculated using an automatic algorithm. The post-stress and rest ratios were determined for both end-diastolic (EDV) and end-systolic (ESV) volume. Normal values for all these parameters were obtained using data from 149 patients with a low likelihood (<5%) of coronary artery disease (CAD). In 50 of the 147 (34%) of patients with reversible perfusion defects, post-stress LVEF was >5% lower than rest values (stunned group), while the remaining 97 patients did not show a significant LVEF change (group 2A). The percentage of patients who developed exercise-induced angina, the percentage of patients who underwent coronary angiography and the segmental summed perfusion and WT scores were significantly higher in the stunned group compared with group 2A. Only ESV increased significantly post-stress, and this increase occurred only in stunned patients. Both EDV and ESV ratios were significantly higher in the stunned group compared with normal controls (P=0.008 and P<0.000001, respectively) and with the subgroup 2A (P=0.011 and P<10(-12), respectively). The ESV stress/rest ratio correlated significantly with the summed WT difference score by univariate analysis in stunned patients. It can be concluded that the post-stress ESV dilation, obtained by stress/rest gated SPECT, seems to be due to endocardial post-ischemic stunning. The stunned patients showed more severe clinical, angiographic, perfusion and function parameters.     

Segmental analysis of SPECT 99mTc-methoxy isobutyl isonitrile and 201Tl myocardial imaging in ischaemic heart disease

To study the potential usefulness of 99mTc-methoxy isobutyl isonitrile (99mTc-MIBI) as a substitute for 201Tl in assessing patients with ischaemic heart disease, 24 patients underwent 1 day rest and exercise 99mTc-MIBI single photon emission computerised tomography (SPECT) 1 week after SPECT exercise 201Tl. All patients were catheterized within 1 month after myocardial imaging. In 17 patients, resting first pass radionuclide angiography (FPRNA) was performed with 99mTc-MIBI. The heart to lung ratio for 99mTc-MIBI and 201Tl was calculated both at rest and exercise. The segmental analysis for myocardial perfusion reveals that 87/96 segments (91%) were correctly classified by SPECT 201Tl and 84/96 segments (88%) were correctly classified by 99mTc-MIBI. A significant correlation was present between LVEF measured by 99mTc-MIBI FPRNA and contrast ventriculography (r = 0.85, P less than 0.0001). The heart to lung ratio both at rest and exercise for 99mTc-MIBI is significantly higher than 201Tl (P less than 0.01 and less than 0.001 respectively). We conclude that 99mTc-MIBI is a promising agent for simultaneous evaluation of myocardial perfusion and cardiac function.     

Identification of extensive coronary artery disease: Incremental value of exercise Tl-201 SPECT to clinical and stress test variables

BACKGROUND: The ability of the size of a total myocardial perfusion defect (MPD) to detect extensive coronary artery disease (CAD) is currently suboptimal with exercise thallium 201 single photon emission computed tomography (SPECT). To improve its performance, exercise electrocardiography and indirect scintigraphic markers of extensive CAD were proposed (increased right ventricular Tl-201 uptake, lung-to-heart [L/H] ratio, and left ventricular transient ischemic dilation ratio). We aimed to determine the additive value of these criteria for the detection of extensive CAD. METHODS AND RESULTS: The population included 338 patients who underwent exercise Tl-201 SPECT and coronary angiography. Patients were classified as having extensive CAD (left main, multivessel, or 1-vessel proximal left anterior descending CAD) or limited CAD (1-vessel disease other than proximal left anterior descending CAD or no CAD). First, Tl-201 SPECT provided higher diagnostic value than exercise electrocardiography. Second, age, percent target heart rate achieved, total MPD, and L/H ratio were independent predictors of extensive CAD. Third, visually estimated abnormal right ventricular Tl-201 uptake did not present additional information. Fourth, L/H ratio presented a higher diagnostic accuracy than left ventricular transient ischemic dilation ratio. CONCLUSIONS: With exercise Tl-201 SPECT, age, percent target heart rate achieved, total MPD, and L/H ratio were independent predictors of extensive CAD.     

The influence of post-exercise cardiac changes on thallium-gated myocardial perfusion scintigraphy findings in normal subjects

BACKGROUND AND AIM: During recovery after exercise, the heart rate and blood pressure return to a resting state more rapidly than the end-systolic left ventricular dimensions and fractional shortening. The aim of this study was to assess how exercise-related cardiac changes affect the interpretation of myocardial perfusion images in normal subjects. Systolic cardiac parameters on gated stress and rest images were evaluated in healthy young and elderly subjects. METHODS: Twenty-six healthy young and 20 healthy elderly subjects participated in the study. An injection of 111-130 MBq of thallium-201 (201Tl) was given at peak exercise. Rest images were acquired 2.5 h after stress acquisition, 15 min after a second injection of 18.5-37 MBq of 201Tl. Data were analysed using automatic-processing software for quantitative gated single photon emission computed tomography (SPECT) (QGS). The parameters derived from QGS were the end-systolic volume (ESV), end-diastolic volume (EDV), left ventricular ejection fraction (LVEF), end-systolic surface area (ESSA) and end-diastolic surface area (EDSA). The difference between wall thickening in the basal and apical segments (Delta WT) was also calculated. Perfusion images were visually assessed for differences in cardiac size, evidence of reversible hypoperfusion and hot spots. RESULTS: In the young group, LVEF was approximately 6% higher at stress than at rest. EDV, ESV, ESSA and EDSA were all significantly lower, and Delta WT was significantly higher, at stress than at rest. In the elderly group, the mean LVEF at stress was slightly higher than the finding at rest (P<0.05). Visual evaluation of perfusion images revealed mild reversible stress hypoperfusion in the inferoseptal region in eight young male subjects. CONCLUSIONS: In healthy young subjects, post-exercise cardiac changes affect systolic functions detected on gated thallium myocardial perfusion scintigraphy, resulting in a smaller heart size during stress. This finding, accompanied by a significant difference in apex to base counts during stress, may cause basal portions of the heart to appear ischaemic. The absence of these findings in the elderly suggests a decrease in contractility with age.     

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.     

Impaired Coronary Flow Reserve Is the Most Important Marker of Viable Myocardium in the Myocardial Segment-Based Analysis of Dual-Isotope Gated Myocardial Perfusion Single-Photon Emission Computed Tomography

Objective

The aim of this study was to investigate the most robust predictor of myocardial viability among stress/rest reversibility (coronary flow reserve [CFR] impairment), ²⁰¹Tl perfusion status at rest, ²⁰¹Tl 24 hours redistribution and systolic wall thickening of ^99mTc-methoxyisobutylisonitrile using a dual isotope gated myocardial perfusion single-photon emission computed tomography (SPECT) in patients with coronary artery disease (CAD) who were re-vascularized with a coronary artery bypass graft (CABG) surgery.

Materials and Methods

A total of 39 patients with CAD was enrolled (34 men and 5 women), aged between 36 and 72 years (mean 58 ± 8 standard in years) who underwent both pre- and 3 months post-CABG myocardial SPECT. We analyzed 17 myocardial segments per patient. Perfusion status and wall motion were semi-quantitatively evaluated using a 4-point grading system. Viable myocardium was defined as dysfunctional myocardium which showed wall motion improvement after CABG.

Results

The left ventricular ejection fraction (LVEF) significantly increased from 37.8 ± 9.0% to 45.5 ± 12.3% (p < 0.001) in 22 patients who had a pre-CABG LVEF lower than 50%. Among 590 myocardial segments in the re-vascularized area, 115 showed abnormal wall motion before CABG and 73.9% (85 of 115) had wall motion improvement after CABG. In the univariate analysis (n = 115 segments), stress/rest reversibility (p < 0.001) and ²⁰¹Tl rest perfusion status (p = 0.024) were significant predictors of wall motion improvement. However, in multiple logistic regression analysis, stress/rest reversibility alone was a significant predictor for post-CABG wall motion improvement (p < 0.001).

Conclusion

Stress/rest reversibility (impaired CFR) during dual-isotope gated myocardial perfusion SPECT was the single most important predictor of wall motion improvement after CABG.     

Ribose facilitates thallium-201 redistribution in patients with coronary artery disease

To investigate whether i.v. infusion of ribose, an adenine nucleotide precursor, postischemia facilitates thallium-201 (201Tl) redistribution and improves identification of ischemic myocardium in patients with coronary artery disease (CAD), 17 patients underwent two exercise 201Tl stress tests, performed 1-2 wk apart. After immediate postexercise planar imaging, patients received either i.v. ribose (3.3 mg/kg/min x 30 min) or saline as a control. Additional imaging was performed 1 and 4 hr postexercise. Reversible defects were identified by count-profile analysis. Significantly more (nearly twice as many) reversible 201Tl defects were identified on the post-ribose images compared to the post-saline (control) images at both 1 and 4 hr postexercise (p less than 0.001). Quantitative analyses of the coronary arteriogram was available in 13 patients and confirmed that the additional reversible defects were in myocardial regions supplied by stenosed arteries. We conclude that ribose appears to facilitate 201Tl redistribution in patients with CAD and enhances identification of ischemic myocardium.