Análisis de fase en estudios Gated-SPECT como predictor de mortalidad en pacientes con enfermedad coronaria y función ventricular izquierda deprimida / Phase analysis in Gated-SPECT studies as a predictor of mortality in patients with coronary diseases and impaired left ventricular function

Resumen Antecedentes: La enfermedad coronaria es una de las principales causas de morbimortalidad en los países occidentales. En etapas avanzadas de la enfermedad, los procesos de remodelación miocárdica pueden conducir a insuficiencia cardíaca progresiva y disfunción ventricular izquierda. El análisis de fase de los estudios de perfusión miocárdica Gated-SPECT muestra parámetros que han sido caracterizados como marcadores válidos de asincronía ventricular. Objetivo: Evaluar los parámetros del análisis de fase en Gated-SPECT como predictores independientes de mortalidad en pacientes con enfermedad coronaria avanzada e insuficiencia ventricular izquierda. Materiales y método: Estudio retrospectivo de cohortes históricas de 185 pacientes consecutivos (140 hombres; edad media=67,6±12,7 años) a los que, entre enero de 2009 y marzo de 2011, se les hizo estudio isotópico de perfusión miocárdica con estimulación farmacológica con resultado positivo para isquemia/necrosis con FEVI ≤ 55%. Adicionalmente, se les realizó seguimiento medio de 32,4±10,5 meses registrándose la aparición de eventos cardíacos mayores (infarto agudo de miocardio no mortal, ingreso hospitalario y revascularización coronaria tardía) y mortalidad total. Resultados: Durante el seguimiento se registraron eventos mayores en 51 pacientes así como 28 fallecimientos, de los cuales, 82,1% mostró valores alterados de los parámetros de fase: media=141,1(±17,6(; desviación estándar=15,8(±10,1(; ancho de banda=59,1(±36( y FEVI=42,4%±10,8%. El análisis de Cox mostró al ancho de banda como un predictor independiente de muerte, disminuyendo significativamente la supervivencia y aumentando el riesgo de muerte (hazard ratio=2,68; p<0,05). Conclusiones: El ancho de banda en el análisis de fase se comporta como un predictor independiente de muerte en pacientes con miocardiopatía conocida y FEVI deprimida.

Abstract Background: Coronary disease is one of the main causes of morbidity and mortality in western countries. In the advanced stages of the disease the myocardial remodelling processes can lead to progressive heart failure and left ventricular impairment. The phase analysis of Gated-SPECT studies of myocardial perfusion show parameters that have been characterised as valid marker of ventricular asynchrony. Objective: To evaluate the phase analysis parameters in Gated SPECT as independent predictors of mortality in patients with advanced coronary disease and left ventricular failure. Materials and method: A retrospective historic cohort study was conducted on 185 consecutive patients (140 males; mean age = 67.6±12.7 years) on whom, between January 2009 and March 2011, an isotope myocardial perfusion study was carried out with pharmacologic stimulation and with a positive result for ischaemia / necrosis, and with a LVEF ≤ 55%. A mean follow-up of 32.4 ±10.5 months was also performed, recording the appearance of major cardiac events (non-fatal acute myocardial infarctions, hospital admission, delayed coronary revascularisation, and total mortality. Results: Major events were recorded in 51 patients during follow-up. There were also 28 deaths, of which 82.1% showed abnormal values of the phase parameters: media=141.1(±17.6(; standard deviation=15.8(±10.1(; bandwidth=59.1(±36(, and LVEF = 42.4%±10.8%. The Cox analysis showed the bandwidth as an independent predictor of death, significantly reducing the survival and increasing the risk of death (hazard ratio=2.68; P<.05). Conclusions: The bandwidth in the phase analysis behaves as an independent predictive factor in patients with known myocardial disease and an impaired LVEF.

Prognostic value of rest gated SPECT myocardial perfusion in patients with chronic heart failure / 医学研究生学报

Objective Chronic heart failure ( CHF) is a disease with high morbidity, and mortality.The study was designed to explore the prognostic value of rest gated SPECT myocardial perfusion ( GSMPI) in patients with chronic heart failure. Methods This study was a prospective study, in which 142 CHF patients was included from January 1, 2011 to December 31, 2012.All patients underwent GSMPI, further, summed rest score ( SRS) , left ventricular ejection fraction ( LVEF) , end-diastolic volume ( EDV) , end-systolic volume ( ESV) and phase standard deviation ( PSD) were recorded.All the patients were followed up.Primary endpoint was the major adverse cardiac events ( MACE) .Additionally, we analyzed the independent predictive factor of MACE occurrence by using the Cox proportional hazard model. Results during the follow-up, MACE occurred in 65 cases.The median time to MACE occur-rence was 28(5-48) months.The 3-year MACE free survival rate was 64.3%.Multivariate Cox proportional hazards regression analysis showed that cardiac function grade[HR(95%CI):1.761(1.087~4.824), P=0.005], NT-proBNP[HR(95%CI):1.153(1.125~5.997), P =0.009], LVEF[HR(95%CI): 1.945(1.138 ~ 6.131), P=0.019], SRS[HR(95%CI):1.517(1.108~4.278), P=0.027] and PSD[HR(95%CI):1.442(1.156~5.339), P=0.032] were all independent predictors of MACE. Conclusion GSMPI may be a prognostic factor for the patients with chronic heart failure.

Diagnóstico de isquemia miocárdica silente en diabéticos tipo 2 mediante electrocardiograma, ergometría y Gated-SPECT / Diagnosis of silent myocardial ischemia in type 2 diabetic patietns by electrocardiogram, ergometry and Gated-SPECT

Para determinar la relación entre los factores de riesgos ateroscleróticos y la isquémica miocárdica silente fueron estudiados 31 pacientes diabéticos tipo 2 asintomáticos con exámenes de laboratorio, electrocardiograma, ergometría, Gated-SPECT y coronariografía. Los pacientes fueron clasificados en dos grupos: SPECT positivo y SPECT negativo. Se realizaron pruebas de asociación para cada variable y se construyeron curvas ROC para identificar marcadores de riesgo. En el 35,5 por ciento de los pacientes se detectó isquemia miocárdica silente con una buena correlación angiográfica. Se evidenció asociación significativa entre SPECT positivo y los factores de riesgo ateroscleróticos: valores bajos de HDLc, antecedentes patológicos familiares de cardiopatía isquémica y enfermedad vascular periférica. Los modelos de regresión logística concluyeron que valores bajos de HDLc unidos a antecedentes patológicos familiares de cardiopatía isquémica podrían ser fuertes predictores de isquemia miocárdica silente en diabéticos tipo 2 asintomáticos.

31 aymptomatic type 2 diabetic patients were studied by lab tests, electrocardiogram, ergometry, Gated-SPECT and coronariography to determine the relation between the atherosclerotic risk factors and the silent myocardial ischemia. Patients were classified into two groups: positive SPECT and negative SPECT. Association tests were made for each variable and ROC curves were constructed to identify risk markers. In 35,5 percent of the patients silent myocardial ischemia was detected with a good angiographic correlation. A siginificant association was evidenced between positive SPECT and the atherosclerotic risk factors, namely, low values of HDLc, family pathological history of ischemic heart disease and peripheral vascular disease. The logistic regression models showed that low values of HDLc together with family pathological history of ischemic heart disease may be strong predictors of silent myocardial ischemia in asymptomatic type 2 diabetic patients.

Respiratory Motion Detection and Correction in ECG-Gated SPECT: a New Approach

OBJECTIVE: Gated myocardial perfusion single-photon emission computed tomography (GSPECT) has been established as an accurate and reproducible diagnostic and prognostic technique for the assessment of myocardial perfusion and function. Respiratory motion is among the major factors that may affect the quality of myocardial perfusion imaging (MPI) and consequently the accuracy of the examination. In this study, we have proposed a new approach for the tracking of respiratory motion and the correction of unwanted respiratory motion by the use of respiratory-cardiac gated-SPECT (RC-GSPECT). In addition, we have evaluated the use of RC-GSPECT for quantitative and visual assessment of myocardial perfusion and function. MATERIALS AND METHODS: Twenty-six patients with known or suspected coronary artery disease (CAD)-underwent two-day stress and rest (99m)Tc-Tetrofosmin myocardial scintigraphy using both conventional GSPECT and RC-GSPECT methods. The respiratory signals were induced by use of a CT real-time position management (RPM) respiratory gating interface. A PIO-D144 card, which is transistor-transistor logic (TTL) compatible, was used as the input interface for simultaneous detection of both ECG and respiration signals. RESULTS: A total of 26 patients with known or suspected CAD were examined in this study. Stress and rest myocardial respiratory motion in the vertical direction was 8.8-16.6 mm (mean, 12.4 +/- 2.9 mm) and 7.8-11.8 mm (mean, 9.5 +/- 1.6 mm), respectively. The percentages of tracer intensity in the inferior, inferoseptal and septal walls as well as the inferior to lateral (I/L) uptake ratio was significantly higher with the use of RC-GSPECT as compared to the use of GSPECT (p < 0.01). In a left ventricular ejection fraction (LVEF) correlation analysis between the use of rest GSPECT and RC-GSPECT with echocardiography, better correlation was noted between RC-GSPECT and echocardiography as compared with the use of GSPECT (y = 0.9654x + 1.6514; r = 0.93, p < 0.001 versus y = 0.8046x + 5.1704; r = 0.89, p < 0.001). Nineteen (19/26) patients (73.1%) showed abnormal myocardial perfusion scans with reversible regional myocardial defects; of the 19 patients, 14 (14/26) patients underwent coronary angiography. CONCLUSION: Respiratory induced motion can be successfully corrected simultaneously with the use of ECG-gated SPECT in MPI studies using this proposed technique. Moreover, the use of ECG-gated SPECT improved image quality, especially in the inferior and septal regions that are mostly affected by diaphragmatic attenuation. However, the effect of respiratory correction depends mainly on the patient respiratory pattern and may be clinically relevant in certain cases.

Correlación entre la fracción de expulsión obtenida con SPECT sincronizado y ventriculografía con radionúclidos en pacientes con cardiopatía isquémica / Correlatin betweeen left ventricular ejection fraction assessed by gated spect and radionuclide ventriculograhyy

Antecedentes : Recientemente se ha propuesto el empleo del SPECT sincronizado para la medición de fracción de expulsión, volúmenes y movilidad de la pared ventricular. El objetivo de este estudio es evaluar la fracción de expulsión (FE) obtenida con el programa de SPECT sincronizado (QGS, Cedars Sinai) en comparación con la ventriculografía en equilibrio en pacientes isquémicos. Método : Estudiamos 50 pacientes consecutivos con cardiopatía isquémica, a los cuales se les realizó ventriculografía radioisotópica con la técnica de equilibrio in vitro modificada y SPECT sincronizado con un protocolo dual (Talio 201reposo/Tc-99m SestaMIBI esfuerzo) utilizando el programa QGS (Cedars Sinai). Resultados : Se observó una correlación del 92% entre los dos métodos. En el análisis por subgrupos, la correlación más alta (r = 0.89) se encontró en el grupo 2, que incluye a los pacientes con disfunción ventricular moderada (FE 30-50%), mientras que en los pacientes con disfunción ventricular severa (grupo 3, FE < 30%) se encontró una correlación menor (r = 0.76) que en el grupo 2, pero mayor que en los pacientes con FE > 50% (grupo 1). Conclusiones : Existe una buena correlación entre la FE del ventrículo izquierdo obtenida con el método de SPECT sincronizado y la ventriculografía en equilibrio, independientemente de la cifra de FE.

Background : Recently, the use of Gated SPECT to assess ejection fraction, volumes and ventricular wall motion has been suggested. The aim of this study is to compare the ejection fraction (EF) obtained by Gated SPECT (QGS, Cedars Sinai) with the values obtained through equilibrium ventriculography in patients with ischemic heart disease. Methods : We studied 50 consecutive patients that were diagnosed by equilibrium radioisotopic ventriculography and Gated SPECT with a dual protocol (Tl-201rest/Tc-99m SestaMIBI stress) using the QGS, Cedars Sinai software. Results : We found a 92% correlation between both tests. In the subgroup analysis, the higher correlation (r = 0.89) was found in group 2, which included patients with moderate ventricular dysfunction (EF 30-50%), wereas, in patients with severe ventricular dysfunction (group 3, EF < 30%), the correlation was lower (r = 0.76) than in group 2, but higher than in patients with EF > 50% (group 1). Conclusions : There is a good correlation between EF obtained with Gated SPECT and equilibrium ventriculography, regardless of the EF value. (Arch Cardiol Mex 2004; 74:25-30).

Quantitative gated myocardial perfusion SPECT / 대한핵의학회잡지

Myocardial perfusion imaging has been increasingly used to provide prognostic data and guidance on the choice of appropriate management of patients with known or suspected coronary artery disease. The electrocardiogram gated myocardial SPECT program is coming into wide use with an advent of 99mTc-labeled tracers and an improvement of SPECT machines. The gated technique permits measurement of important cardiac prognostic indicators without any further discomforts or radiation burden in patients underwent standard myocardial perfusion SPECT. In addition, gated study significantly improves diagnostic yield by reducing the number of borderline interpretations and could find myocardial stunning and viable myocardium. Gated single photon emission computed tomography (SPECT) imaging allows the automated calculation of end-diastolic volume, end-systolic volume, ejection fraction, myocardial mass and the assessment of regional wall motion and thickening, and it have dramatically improved assessment of coronary artery disease in routine nuclear practice. This allows the simultaneous assessment of both perfusion and function within the same acquisition, and serves as a cost-effective technique for providing more diagnostic data with fewer diagnostic tests. Because the diagnostic and prognostic power derived from knowledge of left ventricular function can be added to that provided by assessing myocardial perfusion, gated SPECT imaging has rapidly gained widespread acceptance and is now used on a routine clinical basis in a growing number of laboratories, including South Korea. The gated SPECT technique for measurement of left ventricular parameters has been validated against a variety of well established techniques. In this work, overview of gated myocardial perfusion SPECT focus on functional parameters is presented.

Normal Limits of Left Ventricular Volumes and Ejection Fraction Measured by Gated Myocardial Perfusion SPECT: Comparison of Tc-99m MIBI and Tl-201 / 대한핵의학회잡지

PURPOSE: We evaluated radioisotope and sex-specific differences of normal limits for left ventricle volumes (LVVs) and ejection fraction (EF) using myocardial perfusion gated SPECT (g-SPECT). MATERIALS AND METHODS: Rest Tl-201/post-stress Tc-99m MIBI g-SPECT measurements with acquisitions of 8-frame were evaluated for 70 patients (mean age 55 +/- 14, 56% female) who either had 50%) (n = 58). LVEF, LVVs were automatically determined by quantitative gated SPECT using QGS program. RESULTS: Similar results were obtained for mean LVEF between Tc-99m MIBI (62% +/- 7%) and Tl-201 (63% +/- 8%) g-SPECT measurements. In Contrast, Tl-201 g-SPECT had significantly lower LVVs values (EDV; 74 +/- 23 mL, ESV; 28 +/- 14 mL) than Tc-99m MIBI g-SPECT (EDV; 82 +/- 25 mL, ESV; 32 +/- 15 mL) (p< 0.05). Women had significantly lower EDV (Tc-99m MIBI; 71 +/- 18 mL, Tl-201; 65 +/- 17 mL), and ESV values (Tc-99m MIBI; 27 +/- 10 mL, Tl-201; 23 +/- 8 mL) compared with EDV (Tc-99m MIBI; 96 +/- 27 mL, Tl-201; 85 +/- 24 mL), and ESV values (Tc-99m MIBI; 40 +/- 17 mL, Tl-201; 36 +/- 16 mL) of men (p< 0.05). Women had significantly higher LV EF values (65% +/- 7%) than men (60% +/- 8%) by Tl-201 gated SPECT (p< 0.05). CONCLUSION: These data suggest significant differeuces in normal limits for LVVs and EF, according to genders and radiopharmaceutical. Therefore, the evaluation of cardiac function in patients should consider radioisotope and sex-matched normal values.

Reproducibility of an Automatic Quantitation of Regional Myocardial Wall Motion and Systolic Thickening on Gated Tc-99m-MIBI Myocardial SPECT / 대한핵의학회잡지

PURPOSE: The aim of this study is to investigate the reproducibility of the quantitative assessment of segmental wall motion and systolic thickening provided by an automatic quantitation algorithm. MATERIALS AND METHODS: Tc-99m-MIBI gated myocardial SPECT with dipyridamole stress was performed in 31 patients with known or suspected coronary artery disease (4 with single, 6 with two, 11 with triple vessel disease; ejection fraction 51+/-14%) twice consecutively in the same position. Myocardium was divided into 20 segments. Segmental wall motion and systolic thickening were calculated and expressed in mm and % increase respectively, using AutoQUANTTM software. The reproducibility of this quantitative measurement of wall motion and thickening was tested. RESULTS: Correlations between repeated measurements on consecutive gated SPECT were excellent for wall motion (r=0.95) and systolic thickening (r=0.88). On Bland-Altman analysis, two standard deviation was 2 mm for repeated measurement of segmental wall motion, and 20% for that of systolic thickening. The weighted kappa values of repeated measurements were 0.807 for wall motion and 0.708 for systolic thickening. Sex, perfusion, or segmental location had no influence on reproducibility. CONCLUSION: Segmental wall motion and systolic thickening quantified using AutoQUANTTM software on gated myocardial SPECT offers good reproducibility and is significantly different when the change is more than 2 mm for wall motion and more than 20% for systolic thickening.

Reproducibility of Gated Myocardial Perfusion SPECT for the Assessment of Myocardial Function : Comparison with Thallium-201 and Technetium-99m-MIBI / 대한핵의학회잡지

PURPOSE: We compared the reproducibility of 201Tl and 99mTc-sestamibi (MIBI) gated SPECT measurement of myocardial function using the Germano algorithm. MATERIALS AND METHODS: Gated SPECT acquisition was repeated in the same position in 30 patients who received 201Tl and in 26 who received 99mTc-MIBI. The quantification of end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF) on 201Tl and 99mTc-MIBI gated SPECT was processed independently using Cedars quantitative gated SPECT software. The reproducibility of the assessment of myocardial function on 201Tl gated SPECT was compared with that of 99mTc-MIBI gated SPECT. RESULTS: Correlation between the two measurements for volumes and EF was excellent by the repeated gated SPECT studies of 201Tl (r=0.928 to 0.986; p<0.05) and 99mTc-MIBI (r=0.979 to 0.997; p<0.05). However, Bland Altman analysis revealed the 95% limits of agreement (2 SD) for volumes and EF were tighter by repeated 99mTc-MIBI gated SPECT (EDV: 14.1 ml, ESV: 9.4 ml and EF: 5.5%) than by repeated 201Tl gated SPECT (EDV: 24.1 ml, ESV: 18.6 ml and EF: 10.3%). The root mean square (RMS) values of the coefficient of variation (CV) for volumes and EFs were smaller by repeated 99mTc-MIBI gated SPECT (EDV: 2.1 ml, ESV: 2.7 ml and EF: 2.3%) than by repeated 201Tl gated SPECT (EDV: 3.2 ml, ESV: 3.5 ml and EF: 5.2%). CONCLUSION: 99mTc-MIBI provides more reproducible volumes and EF than 201Tl on repeated acquisition gated SPECT. 99mTc-MIBI gated SPECT is the preferable method for the clinical monitoring of myocardial function.

Echocardiographic Assessment of Left Ventricular Systolic Function in Comparision with Automatic Quantification of 201TI Gated Peerfusion SPECT

BACKGROUND AND OBJECTIVES: Assessment of left ventricular systolic function is an important clinical variable with respect to diagnosis, prognosis and treatment in various clinical situation. Automatic quantification of ventricular volume and ejection fraction by delineating 3 dimensional endocardial boundaries from the gated perfusion SPECT was validated. The purposes of this study were to assess the agreement of left ventricular ejection fraction determined by two-dimensional echocardiography and automatic quantification of perfusion SPECT and compare different echocardiographic methods with the reference method, automatic quantification of perfusion SPECT. METHOD: Twenty seven patients (20 men, 7 women; mean age 60+/-12) with acute myocardial infarction (anterior: 16, inferior: 7, lateral: 4) and twenty one patients (12 men, 9 women; mean age 60+/-12) without myocardial infarction history and regional wall motion abnormality in echocardiography were studied. All patients had two-dimensional echocardiography and 201Tl perfusion SPECT performed within 5 days of each other. Ejection fraction of left ventricle was calculated by echocardiography using modified Simpson's method and M-mode method. Also, ejection fraction of left ventricle was estimated by 201Tl perfusion SPECT using automatic software (quantitative gated SPECT[QGS]; Cedars-Sinai Medical Center, Los Angels, CA). RESULTS: The agreement of ejection fraction between M-mode method and QGS (limit of agreement -3.48, 3.2; average limit of agreement 6.68) in control group was better than that between modified Simpson's method and QGS (limit of agreement 0.04, 8.42; limit of agreement average limit of agreement 8.38). But, The agreement of ejection fraction between modified Simpson's method and QGS in the acute myocardial infarction group (limit of agreement; -15.31, 10.01; average limit of agreement 12.66) was better than that between M-mode method and QGS (limit of agreement -17.82, 13.86; average limit of agreement 15.84). The agreement of ejection fraction between modified Simpson's method and QGS (limit of agreement; -8.49, 5.74; average limit of agreement 7.12) in the anterior myocardial infarction was more accordancy than lateral and inferior wall infarction (limit of agreement; -12.11, 13.74; average limit of agreement 12.92). CONCLUSION: The M-mode method in patients without regional wall motion abnormality and modified Simpson's method in patients with regional wall motion abnormality, especially in anterior wall infarction seen to be useful method for the assessment of left ventricular ejection fraction.

Pre-Test Likelihood, Experience of Operators and Additive Diagnostic Efficacy of Gated Attenuation-Corrected Myocardial SPECT in coronary Artery disease

BACKGROUND AND OBJECTIVES: We investigated if gated and/or attenuation-corrected SPECT improved performance of experienced or in-experienced operators in the diagnosis of coronary artery disease (CAD) or stenosed arteries in patients having intermediate or high pretest likelihood. MATERIALS AND METHODS: Rest/dipyridamole stress gated attenuation-corrected SPECT was performed in 81 patients (M:F=48:33, 62+/-8.6 years old, of high (n=38) or intermediate (n=43) pre-test likelihood for CAD, 1 vessel; 14, 2 vessel; 19, 3 vessel disease; 31, normal; 17). Two experienced and one novice physicians graded 1 (normal) to 5 (definitely abnormal) for each artery 1) by conventional rest Tl-201/stress Tc-99m-MIBI SPECT, 2) 1) plus viewing gated SPECT (+gated) and 3) 2) plus attenuation-corrected SPECT (+AC gated). Areas under curves (AUC) of receiver operating characteristic (ROC) curves were compared. RESULTS: AUC was greater in patients with high likelihood than intermediate likelihood. Novice physician performed better in diagnosing RCA stenosis (AUC: 0.53 for usual, 0.58 for +gated, and 0.66 for +AC gated) in patients with intermediate likelihood. AUC was not different for the diagnosis of CAD and LAD or LCx. Performance of experienced physicians was not different regardless of pre-test likelihood. Novice operator's specificity increased from 53% to 73% for CAD, and 62% to 89% (p<0.05) for RCA in patients with intermediate likelihood. CONCLUSION: We conclude that gated attenuation-corrected SPECT was helpful only for novice physician to diagnose RCA stenosis by increasing specificity in patients with intermediate likelihood. Even for inexperienced physician, these methods were not helpful in patients with high pre-test likelihood or for LAD or LCX.

Predictive Values of Gated Myocardial SPECT for Wall Motion Improvement After Bypass Surgery / 대한핵의학회잡지

We studied to investigate the predictive values of gated SPECT for the improvement of wall motion after bypass surgery. As we compared postoperative SPECT with preoperative ones, we defined viability as wall motion improvement. We performed rest 71-201/stress Tc-99m-MIBI gated SPECT in 25 patients before and 3 months after bypass surgery. Myocardial wall motion was graded as normal, hypokinesia, akinesia, and dyskinesia by pair-wise visual analysis of gated pre and postoperative SPECT's on the same monitor screen. Myocardial wall thickening was determined good or poor Among 92 segments with wall motion abnormalities before operation, 69 (75%) improved and 23 did not. Before operation, we could find segments with good systolic thickening in 64 segments among total 92. Thickening of the remaining 28 was poor. Wall motion improved postoperatively in 45 segments (70%) among 64 with good thickening. Twenty four(86%) among 28 segments with poor thickening had also improved. We grouped segments into mild(hypokinetic) and severe(akinetic/dyskinetic) ones. Among 33 segments with severe motion abnormalities, 14 had good thickening and 19 did not. Nine(60%) improved out of 14 segments having severe abnormality with good thickening. However, 16(84%) segments out of 19 having severe abnormality with poor thickening also improved. Neither degree of perfusion decrease nor severity of wall motion abnormalities could explain the high rate of false negatives. In conclusion, as we defined viability as wall motion improvement by comparing pre and postoperative SPECT, systolic thickening observed by gated Tc-99m-MIBI SPECT in myocardial segments with wall motion abnormalities predicted wall motion improvement after bypass surgery. However, poor thickening could not be referred as evidence of nonviable myocardium both in mild and severe contractile dysfunction, so that we might need stimulation study such as dobutamine echocardiography or dobutamine gated SPECT.