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.     

Septal stunning by dipyridamole stress shown on quantitative gated perfusion SPECT in a child with hypertrophic cardiomyopathy.

PURPOSE: Myocardial ischemia is an important problem in hypertrophic cardiomyopathy. Stunning is an important mechanism in progressive dysfunction of the ischemic myocardium. In this report, the authors found prolonged myocardial stunning in a child with hypertrophic cardiomyopathy that was induced by dipyridamole stress on quantitative gated SPECT. MATERIALS AND METHODS: A 6-year-old boy with septal hypertrophy underwent rest and dipyridamole stress gated myocardial SPECT. Software was used to quantify automatically segmental perfusion and function at rest and after stress. RESULTS: Perfusion imaging showed a reversible perfusion decrease in the hypertrophic septum. Cine-gated imaging of the septum showed dyskinesia and a severe abnormality of systolic thickening during the poststress period, whereas it showed nearly complete recovery at rest. Quantified regional perfusion and function indices also showed this perfusion decrease and myocardial dysfunction after dipyridamole stress. CONCLUSION: In a child with hypertrophic cardiomyopathy, myocardial stunning was induced by dipyridamole stress, in accordance with decreased perfusion reserve.     

Importance of gated imaging in both phases of myocardial perfusion SPECT: myocardial stunning after dipyridamole infusion

We present the case report of a 72-y-old woman who underwent (99m)Tc-sestamibi gated myocardial perfusion SPECT with a 2-d protocol. SPECT images revealed ischemia of the apical, anteroapical, apicoseptal, and septal walls. Postdipyridamole gated SPECT revealed significant deterioration in the left ventricular ejection fraction (LVEF), wall motion, and systolic wall thickening relative to the findings obtained with rest gated SPECT. Myocardial stunning is a lingering contractile dysfunction that occurs after a brief ischemic insult. Myocardial stunning after dynamic exercise or pharmacologic stress tests has been demonstrated. Thus, the use of gated SPECT in both phases of perfusion studies may add useful information about cardiac function, as a poststress study alone probably reflects stunned myocardium in some patients undergoing ischemic stress tests. The difference between poststress LVEF and rest LVEF may have a powerful impact on prognosis, as it seems to depend on the extent and severity of induced ischemia.     

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%.     

Characteristics of regional myocardial stunning after exercise in gated myocardial SPECT.

BACKGROUND: A number of studies have demonstrated prolonged left ventricular (LV) global dysfunction after exercise-induced ischemia in gated myocardial single photon emission tomography (SPECT) as a manifestation of exercise-induced stunning. This study investigated the residual effects of exercise on postexercise LV regional function and its implications on the detection of stunning in gated SPECT. METHODS AND RESULTS: Fifty-three subjects with known or suspected coronary artery disease and 10 control subjects underwent myocardial SPECT according to a same-day exercise-rest protocol. Both postexercise and resting images were gated and acquired 1 hour after injection of technetium 99m tetrofosmin. The LV global ejection fraction and segmental systolic wall thickening were quantitated with the use of an automatic program. Segmental perfusion was assessed semiquantitatively on summed nongated tomograms. Wall thickening index (WTI), the ratio of systolic wall thickening of a segment to that of a corresponding control segment, was significantly lower after exercise than at rest in the reversible defect (RD) segments (0.66 +/- 0.24 vs 0.78 +/- 0.24; P <.0001). In patients with exercise-induced ischemia, the difference in WTI between rest and after exercise was significantly greater in the RD segments, which represented ischemia, than in the non-RD segments. Postexercise WTIs were not different from the resting values in subjects with no perfusion abnormalities or who had fixed defects (infarction). Significant postexercise dysfunction was present in 44% of the RD segments, compared with 5% of the normal and 3% of the fixed defect segments. Postexercise segmental dysfunction was correlated with the segmental reversibility score, the difference in defect scores between exercise and rest images (n = 82, Spearman rank correlation coefficient = -0.78, P <.0001). Among 19 patients with ischemia, 9 (47%) exhibited concurrent segmental and global dysfunction, but segmental dysfunction persisted in the absence of global dysfunction in 4 additional patients (21%). CONCLUSIONS: Significant postexercise LV regional dysfunction, consistent with the concept of stunning, occurs in the region of severe ischemia. The incidence and magnitude of regional stunning are determined by the severity of ischemia. For the detection of stunning in gated SPECT, LV regional dysfunction may be more sensitive than global dysfunction.     

Transient ischemic stunning of the myocardium in stress thallium-201 gated SPET myocardial perfusion imaging: segmental analysis of myocardial perfusion,wall motion and wall thickening changes

Prolonged and persistent myocardial stunning has recently been demonstrated using technetium-99m sestamibi gated single-photon emission tomography (SPET) myocardial perfusion imaging post exercise or pharmacological stress test. In this study, we investigated the early postischemic transient myocardial stunning on early and delayed poststress thallium-201 gated SPET myocardial perfusion imaging using segmental wall motion (WM) and wall thickening (WT) analysis. A total of 1,680 segments from 84 patients' studies (53 men and 31 women, mean age 60 years) were evaluated on both early and delayed thallium-201 gated SPET treadmill exercise (59) or dobutamine stress (25) myocardial perfusion imaging. Semiquantitative analysis of perfusion, WM and WT in all segments was performed by two observers. Segments were classified according to changes in WM and WT between early and delayed images into normal, fixed abnormality, or improved abnormality (transient stunning), and were further classified according to changes in perfusion into normal, fixed defects, or ischemic. There were significant correlations between perfusion and WM, perfusion and WT, and WM and WT segmental scores on both early and delayed images. Transient stunning was seen significantly ( P < 0.001) more often in ischemic segments than were normal or fixed perfusion defects using WM (58%) and WT (50%) assessments. There was also a significant correlation between the severity of ischemia and transient stunning with either WM ( P < 0.05) or WT ( P < 0.005) evaluation. Segmental myocardial contractility assessment from gated SPET (201)Tl myocardial perfusion imaging using WM and WT was comparable, and results correlated well with the myocardial perfusion assessment. Early transient myocardial stunning was frequently observed in ischemic segments and was related to the severity of myocardial ischemia.     

Does motion analysis in postexercise gated sestamibi SPECT reflect rest left ventricular motion even in severe coronary artery disease?

PURPOSE: Evidence has suggested that postexercise gated Tc-99m sestamibi SPECT (GSPECT) provides combined information about resting wall motion and exercise perfusion. No data have been published about possible differences in wall motion analysis between postexercise and resting GSPECT. METHODS: Fifty patients underwent postexercise (symptom-limited bicycle stress) and rest GSPECT and cardiac catheterization with contrast ventriculography. In 35 patients, additional rest planar Tc-99m RBC radionuclide ventriculography (RNV) was performed. Four observers independently performed left ventricular ejection fraction (LVEF) calculations and visual analysis of regional wall motion (graded in four stages) for all studies. RESULTS: The LVEF calculations in GSPECT revealed a statistically significant difference between postexercise (45.8 +/- 15.7%) and rest (48.0 +/- 16.1%; P < 0.05) determination. Postrest GSPECT LVEF showed a better correlation with LVEF determination performed with contrast ventriculography and RNV than did postexercise GSPECT LVEF. The reduced postexercise wall motion could be shown in segments with exercise-induced ischemia and in those with normal regional perfusion but not in segments with irreversibly abnormal perfusion. CONCLUSIONS: Postexercise GSPECT provides reliable information regarding global wall motion even in severe coronary artery disease, but regional wall motion is underestimated compared with rest GSPECT, because of an imprecise surface detection algorithm in ischemic wall segments and possibly postexercise stunning in severe coronary artery disease.     

Adenosine-induced long-standing postischemic left ventricular dysfunction evaluated with gated SPECT

OBJECTIVES: This study was performed to determine the after-effects of pharmacologic stress (adenosine) on left ventricular (LV) function-end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (LVEF)-with Tl-201 and Tc-99m MIBI SPECT. METHODS: A total of 263 patients were grouped according to the time interval between isotope injection and imaging. Group A: within 1 hour (n = 99; men, n = 48; women, n = 51; mean age: 63.2 years), subgrouped as patients with no perfusion defect (NPD; n = 61), reversible defect (RD; n = 33), and fixed defect (FD; n = 5). Group B: 1 to 2 hours (n = 110; men, n = 66; woman, n = 44; mean age, 63 years), NPD (n = 64), RD (n = 26), and FD (n = 20). 3) Group C: 2 to 3 hours (n = 54; men, n = 30; women, n = 24; mean age, 62 years); NPD (n = 22), RD (n = 17), and FD (n = 15). All patients were in sinus rhythm during the study and had no prior history of myocardial infarction. RESULTS: In group A, in the patients with RD, poststress LVEF was significantly depressed after adenosine infusion (53.1 +/- 9.5% vs 58.3 +/- 10.2%, P < 0.001) and showed a wall motion abnormality, which was worse after stress than during rest. The mean difference in LVEF (DeltaLVEF) between rest and stress was 5.2%. The DeltaLVEF in those patients with RD was significantly higher than that in the NPD (0.9%, P < 0.01) or FD (2.1%, P < 0.05) subgroups. Twenty of the 33 patients (60.6%) with RD showed an increase in LVEF > or = 5% from poststress to rest, and the poststress ESV (43.3 +/- 19.0 mL) was significantly higher than the ESV (38.5 +/- 18.4 mL, P < 0.01) at rest, but there was no significant difference in the EDV (90.5 +/- 26.4 vs 89.7 +/- 26.2 mL). In group B, DeltaLVEF was 1.5%, 4.4%, and 1.2% in patients with NPD, RD, and FD respectively. In group C, DeltaLVEF was 2.5%, 3.2%, and 0.9% in patients with NPD, RD, and FD respectively, and there was no significant difference in DeltaLVEF among patients. In group C, 4 of 17 patients (23.5%) with RD showed an increase in LVEF > or = 5% from poststress to rest. CONCLUSION: These results showed that adenosine stress-induced postischemic LV dysfunction is well noted on early quantitative gated SPECT in patients with RD and can also be observed on delayed gated SPECT, even though the incidence of LV dysfunction is less than that in early gated SPECT.     

Effect of reversible hypoperfusion on left ventricular volumes measured with gated SPECT at rest and after adenosine infusion

BACKGROUND: The aims of this study were to assess the degree of postischemic left ventricular (LV) dilatation after adenosine stress and to determine the extent to which LV volumes measured with gated single photon emission computed tomography (SPECT) correspond to those obtained by echocardiography. METHODS: Eight-frame gated SPECT with a 2-day technetium-99m tetrofosmin acquisition protocol was used. End-diastolic (EDV) and end-systolic (ESV) volumes were measured automatically with the quantitative gated SPECT algorithm. Reversible myocardial hypoperfusion was evaluated with a 16-segment, 4-point perfusion score model. LV volumes at rest were also measured with echocardiography by use of the biplane Simpson rule. RESULTS: Twenty-two patients (group 1) showed normal perfusion and normal LV systolic function, whereas 33 patients (group 2) had evident coronary heart disease with reversible hypoperfusion. Patients in group 2 had greater EDV and ESV than those in group 1 both at rest and poststress. A greater reduction in ESV from poststress to rest was seen in group 2, which resulted in a slight increase in ejection fraction for patients in this group. The change in ESV from poststress to rest was significantly influenced by the degree of reversible hypoperfusion and by the change in heart rate from poststress to rest. We found a good correlation between LV volumes measured with gated SPECT and echocardiography. CONCLUSION: LV volume measurements with quantitative gated SPECT are comparable to those obtained with echocardiography. Patients with ischemic heart disease have greater LV volumes than patients with normal perfusion. Exercise-augmented adenosine infusion in patients with ischemic heart disease affects ESV more than EDV. This response is partly modulated by the degree of reversible hypoperfusion and possibly represents a minor degree of poststress stunning.     

Limited performance of quantitative assessment of myocardial function by thallium-201 gated myocardial single-photon emission tomography

We investigated the reproducibility between thallium-201 and technetium-99m methoxyisobutylisonitrile (MIBI) gated single-photon emission tomography (SPET) for the assessment of indices of myocardial function such as end-diastolic and end-systolic volume (EDV, ESV), ejection fraction (EF) and wall motion. Rest 201Tl (111 MBq) gated SPET was sequentially performed twice in 20 patients. Rest 201Tl gated SPET and rest 99mTc-MIBI (370 MBq) gated SPET were performed 24 h apart in 40 patients. Wall motion was graded using the surface display of the Cedars quantitative gated SPET (QGS) software. EDV, ESV and EF were also measured using the QGS software. The reproducibility of functional assessment on rest 201Tl gated SPET was compared with that on 99mTc-MIBI gated SPET, and also with that between 201Tl gated SPET and 99mTc-MIBI gated SPET performed on the next day. The two standard deviation (2 SD) values for EDV, ESV and EF on the Bland-Altman plot were 29 ml, 19 ml and 12%, respectively, on repeated 201Tl gated SPET, compared with 14 ml, 11 ml and 5.3% on repeated 99mTc-MIBI gated SPET. The correlations were good (r=0.96, 0.97 and 0.87) between the two measurements of EDV, ESV and EF on repeated rest studies with 201Tl and 99mTc-MIBI gated SPET. However, Bland-Altman analysis revealed that the 2 SD values between the two measurements were 31 ml, 23 ml and 12%. We were able to score the wall motion in all cases using the 3D surface display of the QGS on 201Tl gated SPET. The kappa value of the wall motion grade on the repeated 201Tl study was 0.35, while that of the wall motion grade on the repeated 99mTc-MIBI study was 0.76. The kappa value was 0.49 for grading of wall motion on repeated rest studies with 201Tl and 99mTc-MIBI. In conclusion, QGS helped determine EDV, ESV, EF and wall motion on 201Tl gated SPET. Because the EDV, ESV and EF were less reproducible on repeated 201Tl gated SPET or on 201Tl gated SPET and 99mTc-MIBI gated SPET on the next day than on repeated 99mTc-MIBI gated SPET, functional measurement on 201Tl gated SPET did not seem to be interchangeable with that on 99mTc-MIBI gated SPET.     

Fast technetium 99m-labeled sestamibi gated single-photon emission computed tomography for evaluation of myocardial function

Background

This study assesses the feasibility of ^99mTc-labeled sestamibi electrocardiographic gated single-photon emission computed tomography (SPECT) with a short acquisition time (6.7 minutes, “fast” gated SPECT) for the evaluation of stress myocardial perfusion and poststress myocardial function. Simultaneous assessment of stress perfusion and poststress function is possible with standard gated SPECT acquisition (19.3 minutes) of stress-injected sestamibi. Sestamibi gated SPECT can be used to evaluate regional wall motion (RWM), thickening, and left ventricular ejection fraction (LVEF); the feasibility of fast gated SPECT has not been evaluated previously.

Methods and Results

Fifty patients were studied who underwent treadmill exercise, sestamibi injection (25 to 30 mCi), and standard gated SPECT 15 minutes after exercise, immediately followed by fast gated SPECT. All patients underwent rest ²⁰¹TI SPECT before exercise testing. All studies were analyzed by semiquantitative visual scoring. Both standard and fast gated SPECT were read for stress perfusion and poststress wall motion and thickening, dividing the left ventricle into 20 segments, on a 5-point scale described previously. The measurement of LVEF used a previously described automatic algorithm. Average myocardial counts per pixel were 58±19 for standard gated SPECT and 13±4 for fast gated SPECT (p=0.0001). Heart/lung ratio was 10.2±4.8 for regular gated SPECT and 10.3±5.7 for fast gated SPECT (difference not significant). Perfusion analysis showed exact agreement in 92% of the segments (κ=0.76; p<0.01). Correlation between LVEFs measured from standard and fast gated SPECT was 0.94. Analysis of 998 segments (two segments were uninterpretable) showed exact agreement in 96% (κ=0.89; p<0.001) for RWM and 94% (κ=0.83; p<0.001) for thickening between standard and fast gated SPECT. In 225 segments with abnormal RWM and 189 segments with abnormal thickening by both standard and fast gated SPECT, exact agreements were 0.92 for RWM (κ=0.90; p<0.001), and 0.87 for thickening (κ=0.80; p<0.01).

Conclusions

Our data demonstrate that fast sestamibi gated SPECT is feasible and yields results equivalent to those of standard sestamibi gated SPECT with respect to left ventricular regional and global function.     

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.     

Clinical usefulness of 201Tl/99mTc-PYP dual myocardial quantitative gated SPECT program using low-dose dobutamine loading in assessment of myocardial viability in patient with acute myocardial infarction--a case report

An 86-year-old man with chest pain was admitted to our hospital. Coronary angiography revealed 99% stenosis of the mid segment of the left anterior descending coronary artery, therefore, a coronary stent was implanted. Immediately after the stent implantation, 99% stenosis occurred at the proximal site of the 1st diagonal artery because of stent jeal. On the 4th hospital day, ECG-gated 201TL/99mTc-PYP dual myocardial quantitative gated SPECT was performed at rest and during low-dose dobutamine loading. The 201Tl scintigraphy revealed moderately reduced uptake in the anterior, septal and apical walls, and 99mTc-PYP uptake was observed in the mid-anterior wall. A three-dimensional surface display of gated 201Tl SPECT images showed severe hypokinesis in the anterior, septal and apical walls at rest. On the other hand, during low-dose dobutamine loading, improved wall motion was observed in the basal anterior and septal walls, while no change was observed in the midanterior and apical wall movements. Three-dimensional surface display of gated 201Tl/99mTc-PYP dual SPECT images revealed similar patterns of wall motion as those of gated 201Tl SPECT images at rest. During low-dose dobutamine loading, on the other hand, a three-dimensional surface display of gated 201Tl/99mTc-PYP dual SPECT images revealed improved wall motion in the basal anterior, septal and apical walls, but worsened wall motion of the mid-anterior wall. After 6 months, a follow-up coronary angiography revealed no re-stenosis of the stent, but 99% stenosis at the proximal aspect of the 1st diagonal artery. Left ventriculography revealed improved wall motion in the apex and akinesis of the mid-anterior wall. These wall motion findings were similar to those visualized in the three-dimensional surface display of gated 201Tl/99mTc-PYP dual SPECT images during low-dose dobutamine loading in the acute phase. These results suggest that 201Tl/99mTc-PYP dual myocardial quantitative gated SPECT using low-dose dobutamine loading could be useful for the assessment of myocardial viability after reperfusion therapy in patients with acute myocardial infarction.     

Combined analysis of resting regional wall thickening and stress perfusion with electrocardiographic-gated technetium 99m-labeled sestamibi single-photon emission computed tomography: Prediction of stress defect reversibility

Background  The high photon flux and stable distribution of the myocardial perfusion agent ^99mTc-labeled sestamibi allow the perfusion data to be acquired in an electrocardiographic (ECG)-gated mode, such that information on resting regional wall thickening may be obtained simultaneously with stress perfusion data. The objective of this study was to assess whether visual analysis of resting regional wall thickening provided by ECG-gated acquisition of ^99mTc-labeled sestamibi stress perfusion images correlates with and predicts the reversibility of stress-induced perfusion defects, potentially obviating the need for rest imaging. Methods and Results  Fifty-nine patients referred for myocardial perfusion imaging were studied with rest and stress single-photon emission computed tomographic (SPECT) sestamibi imaging, and the stress perfusion data were acquired in an ECG-gated mode. Visual analysis of the presence and reversibility of stress perfusion defects on standard imaging was correlated with the wall thickening data from the poststress gated SPECT images. Quantitative circumferential profile analysis of the short-axis images was performed to assess the influence of relative stress perfusion defect severity on the correlation between wall thickening and defect reversibility. Among the 72 segments with stress-induced perfusion defects and visually apparent wall thickening on ECG-gated SPECT images, 69 were reversible on rest imaging (positive predictive value of 96% for wall thickening to predict stress defect reversibility). Of the 35 segments with stress-induced defects and no apparent wall thickening on ECG-gated SPECT images, however, 14 (40%) demonstrated significant stress defect reversibility on rest imaging. This result represents a negative predictive value of only 60% for the lack of apparent wall thickening to predict correctly an irreversible stress defect. Among the segments with reversible stress perfusion defects and visually apparent wall thickening, relative stress sestamibi activity was higher (51%±10%, [percentage of peak]) than in segments with reversible stress defects and no visually apparent wall thickening (39%±4% of peak activity [p<0.0001]). Conclusions  Visual evidence of wall thickening by poststress ECG-gated SPECT sestamibi imaging in the territory of a stress-induced perfusion defect correlates highly with stress defect reversibility on rest imaging and may obviate the need to perform rest imaging, thereby potentially reducing the time and cost involved in myocardial perfusion imaging. The absence of visually apparent wall thickening, however, underestimates the prevalence of stress defect reversibility on rest imaging; in such instances, rest imaging must be performed to differentiate ischemia from infarction in the territory of a stress perfusion defect.     

Assessment of contractile response to dobutamine stress by means of ECG-gated myocardial SPECT: Comparison with myocardial perfusion and fatty acid metabolism

The present study assessed left ventricular performance during dobutamine stress measured using gated SPECT, and compared the results to myocardial perfusion and fatty acid metabolism. METHODS: Thirty-six patients with myocardial infarction given (99m)Tc-sestamibi or (99m)Tc-tetrofosmin were examined by gated SPECT at rest and during dobutamine stress (4-20 microg x kg(-1) x min(-1)). After acquiring data at the highest dose, 201TlCl was injected and dual-isotope SPECT was performed to assess myocardial ischemia. Thirty of 36 patients also underwent myocardial SPECT with 123I-BMIPP. Regional wall motion changes during dobutamine infusion were determined from the gated SPECT data and classified as: (1) Improvement, (2) Worsening, (3) No change, and (4) Biphasic response. For myocardial segments of each infarct area, stress 201Tl, rest (99m)Tc and (123)I-BMIPP uptakes were graded on a five-point scoring system of defects from 0 (normal) to 4 (grossly defective). RESULTS: Rest 99mTc defect score index (DSI) in No change area was significantly higher than that in Biphasic area. The ADSI (stress 201Tl - rest (99m)Tc) in Biphasic area was significantly higher than those in Improvement and No change areas. The deltaDSI (BMIPP - (99m)Tc) in Worsening area tended to be higher than that in No Change area. Conclusions: Regional contractile response to dobutamine stress analyzed by gated SPECT showed that the response in-myocardial infarct areas could be classified by rest and stress myocardial perfusion and BMIPP accumulation.     

Perfusion and mechanical analysis with technetium-99m 2-methoxy-isobutyl-isonitrile in a case of dilated cardiomyopathy

With technetium-99m 2-methoxy-isobutyl-isonitrile (99mTc-MIBI), regional wall thickening in a patient with dilated cardiomyopathy was analyzed by the first component Fourier method. The regional wall thickening was compared with thallium-201 and 99mTc-MIBI SPECT imaging. Thallium-201 SPECT images showed mildly reduced perfusion in the posterior wall and redistribution in the septum, whereas 99mTc-MIBI images showed heterogeneous accumulation around the left ventricular circumference. By means of phase analysis, diffusely decreased wall thickening and discontinuity of percent wall thickening in neighboring segments were observed throughout the left ventricle. Regional wall motion and wall thickening correlated roughly. However, discrepancies between the mechanical function and myocardial perfusion, and discrepancies in regional myocardial perfusion between thallium-201 and 99mTc-MIBI were observed.     

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

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

Usefulness and limitations of ECG-gated myocardial single-photon emission computed tomography with 99mTc-methoxy-isobutyl-isonitrile (MIBI) in patients with prior myocardial infarction]

To evaluate the relationship between regional wall motion and 99mTc-methoxy-isobutyl-isonitrile (MIBI) uptake, ECG-gated single-photon emission computed tomography (SPECT) with 99mTc-MIBI was performed in 20 patients with prior myocardial infarction. The left ventricular images at end-diastole (ED) and end-systole (ES) were divided into 39 segments, respectively. Based on circumferential profile analysis, relative uptake (%EDc, %ESc), percent count increase (% delta C), and normalized percent count increase (% delta Cn) were analyzed in each segment and compared with regional wall motion indices assessed by echocardiography and left ventriculography. ECG-gated SPECT with 99mTc-MIBI provided high contrast tomograms of the left ventricular myocardium. %EDc and %ESc showed good correlations with regional wall motion indices. % delta C and % delta Cn, however, showed lower correlations compared with %EDc and %ESc. In conclusion, high-quality left ventricular images were obtained with 99mTc-MIBI ECG-gated SPECT, but quantitative analysis based on only percent count increase (% delta C) have limitations for evaluation of regional wall motion.     

Nitrate-enhanced gated technetium 99m sestamibi SPECT for evaluating regional wall motion at baseline and during low-dose dobutamine infusion in patients with chronic coronary artery disease and left ventricular dysfunction: Comparison with two-dimensional echocardiography

BACKGROUND: The value of gated single photon emission computed tomography (SPECT) in the assessment of wall motion (WM) in patients with severe perfusion defects and in the evaluation of low-dose dobutamine (LDD)-induced changes is not yet established. In patients with chronic coronary artery disease who have left ventricular (LV) dysfunction, the results of nitrate-enhanced technetium 99m sestamibi (sestamibi) gated SPECT for the evaluation of resting and LDD WM were compared with those of baseline and LDD echocardiography (LDDE). METHODS AND RESULTS: Thirty-seven patients underwent echocardiography and nitrate-enhanced sestamibi gated SPECT within 1 week at rest and during LDD infusion. WM was scored from 1 (normal) to 4 (dyskinetic) by using a 16-segment model. Segments with sestamibi uptake less than 30% were considered unsuitable for WM analysis (36 of 592 segments). Echocardiography was technically unreliable in 10 of 592 segments. The precise agreement between echocardiography and gated SPECT for baseline regional WM was 68.4% (kappa = 0.54), without significant differences for the involved coronary artery territory. The agreement for +/- 1 WM scoring was 96.5% (kappa = 0.94). Contractile reserve during LDD was detected by means of echocardiography in 36% and by means of sestamibi gated SPECT in 33% of baseline asynergic segments. Agreement for detection of WM improvement in response to LDD was 74% (kappa = 0.41). The overall and +/-1 WM score agreement for LDD WM was 67.5% (kappa = 0.50) and 94.7% (kappa = 0.91), respectively. A significant correlation between echocardiography and gated SPECT was observed for both baseline (p = 0.78) and LDD (p = 0.74) WM score index. CONCLUSIONS: In patients with coronary artery disease who have LV dysfunction, nitrate-enhanced sestamibi gated SPECT allows a reliable WM evaluation, both at rest and during LDD infusion, in almost all segments and provides results in agreement with LDDE.     

Dipyridamole technetium-99m-2-methoxy isobutyl isonitrile tomoscintigraphic imaging for identifying diseased coronary vessels: comparison with thallium-201 stress-rest study

A same-day double injection protocol employing 99mTc-methoxyisobutyl isonitrile (MIBI) and myocardial single-photon emission computed tomography (SPECT) for detecting coronary artery disease (CAD) was assessed in 30 patients. SPECT was performed 1 hr after a first injection (250 MBq) of 99mTc-MIBI, given after 0.56 mg/kg dipyridamole (DPD) infusion. Patients were then reinjected at rest (750 MBq) and were reimaged 1 hr later. Within 1 wk, all patients underwent a complete stress-rest SPECT thallium study. Of the 330 myocardial segments evaluated, 25 were judged ischemic by both techniques, while persistent defects were demonstrated in 50 and in 47 with 99mTc-MIBI and 201TI, respectively. Six regions were considered for diseased vessels identification. Sensitivity and specificity for CAD were 100% and 75%, respectively, for both 201TI and 99mTc-MIBI. Sensitivity for identification of diseased vessels by 201TI was 68% for LAD, 89% for RCA, and 80% for LCX as opposed to 75%, 89% and 80%, respectively, by 99mTc-MIBI. Specificity was 93% in both cases for LAD, 73% and 63% for RCA, and 53% and 46% for LCX.