Dual isotope myocardial scintigraphy (201thallium at rest/99 M technetium tetrofosmin with exercise) in the detection of reversible hypoperfusion

The dual-isotope technique (rest 201Tl and stress 99mTc-sestamibi) is useful to assess myocardial perfusion in coronary disease patients. 99mTc-labeled tetrofosmin is a radiopharmaceutical whose characteristics are similar to sestamibi. Thus, we decided to use it to detect reversible myocardial hypoperfusion in patients with a background of myocardial infarction and ischemia. A sequential dual-isotope scintigraphy (3 mCi rest 201Tl and 25 mCi stress 99mTc-tetrofosmin) with 24-hour 201Tl redistribution (RD) was performed in 20 patients with previously confirmed myocardial infarction and clinical and ergometric signs of ischemia. Each patient also underwent a stress-redistribution protocol with redistribution at 4 and 24 hours post injection with 201Tl scintigraphy within two weeks of the first study. The qualitative uptake analysis showed no significant differences in the number of myocardial segments with severe reduction of tracer uptake on stress that improved at rest or in RD images, even if 24-hour RD images were considered. The quantitative global uptake analysis showed a similar defect reversibility with both protocols; however if 24-hour RD images were considered the uptake improvement was significant only when compared with the rest 201Tl images in dual-isotope scintigraphy protocol (75+/-8% vs. 81+/-9% of peak activity, rest vs. 24-hour RD; p<0.01) and not when compared with the 4-hour RD in the 201Tl scintigraphy. On the other hand, when only the segments with severely reduced uptake (<50% of peak activity) were analyzed, the 24-hour RD improved myocardial uptake significantly (p<0.001 vs. rest and vs 4-hour RD) in both protocols. We conclude that a sequential dual-isotope rest 201Tl/stress 99mTc-tetrofosmin scintigraphy is comparable with stress-redistribution 201Tl scintigraphy to detect reversible myocardial hypoperfusion; however in both cases, the addition of 24-hour images increases its usefulness in severely hypoperfused segments, if the uptake of the radiopharmaceutic is quantified.     

Thallium-201 SPECT in coronary artery disease patients with left bundle branch block

Fourteen patients with left bundle branch block (LBBB) underwent immediate postexercise and 3-hr delayed 201Tl single photon emission computed tomography (SPECT) with quantitative analysis using bullseye polar maps. Test performance in detecting individual coronary artery stenosis greater than or equal to 50% demonstrated 100% sensitivity. Specificity was 100% for circumflex stenosis, 78% for right coronary stenosis, but only 10% for left anterior descending coronary stenosis. This very low specificity was due to the fact that 3/4 (75%) patients with left anterior descending stenosis and also 9/10 (90%) patients with normal left anterior descending coronary arteries had immediate septal perfusion defects with redistribution in all cases at 3 hr. Septal abnormalities were most marked in patients who achieved high peak heart rates (greater than 170 bpm). Thus, with LBBB, 201Tl SPECT is indeterminate for left anterior descending coronary disease.     

Assessment of resting thallium-201 reinjection after stress-delayed Tl imaging (I): Comparison with 24-hour scan and regional wall motion

Clinical value of resting reinjection of 1 mCi (37 MBq) of Tl after stress-delayed scan was assessed in comparison with 24 hr delayed scan and regional wall motion (RWM) in 37 patients with coronary artery disease. Of 101 segments with initial perfusion abnormality, concordant findings were observed after Tl reinjection in 67 segments (66%). But redistribution (RD) after Tl reinjection was observed in 19 of the 52 persistent defect (PD) segments (37%), and complete RD was observed 15 of the 43 segments (35%) where 3 hr scan showed incomplete RD. On the other hand, concordant findings were observed on 24 hr delayed scan in 11 of the 20 segments with perfusion abnormality (55%). RD on 24 hr delayed scan was observed in 5 of the 13 PD (38%), but it was not apparent in 3 of the 7 segments where 3 hr scan showed RD. Furthermore the segments which showed RD after Tl reinjection in PD segments tend to have less severe RWM abnormality than the sustained PD segments (RWM score: 1.65 +/- 1.17 vs. 2.29 +/- 1.05, p less than 0.05). These data indicate that Tl reinjection which permits assessment of RD with good quality images on the same day is considered as a valuable means for assessing myocardial viability.     

双核素心肌显像检测存活心肌的对比研究

目的 对比多巴酚丁胺负荷201Tl/静息99Tcm-甲氧基异丁基异腈(MIBI)双核素同步心肌断层显像及多巴酚丁胺负荷-再分布/再注射201Tl心肌断层显像法检测存活心肌的作用.方法 对160例临床怀疑有冠心病的患者予静息状态下静脉注射740 MBq99Tcm-MIBI,休息15 min后进行多巴酚丁胺负荷试验,在达到终止指标时静脉注射111 MSq201TICI.注射后观察5-lO min,分别行早期(10 min)、延迟(3 h)99Tcm-MIBI和201Tl双核素同步心肌断层显像.对早期负荷201Tl图像发现放射性缺损,延迟再分布201Tl和静息99Tcm-MIBI图像未见放射性填充的患者再注射37 MBq201TICI,30min后行再注射心肌灌注显像.负荷枷201Tl图像示放射性缺损,静息99Tcm-MIBI、再分布201Tl及再注射201Tl图像中发现任何一种放射性填充者均为存活心肌.断层显像后2周内全部患者进行了冠状动脉造影.采用SAS 6.12软件进行x2检验.结果 (1) 160例患者冠状动脉造影均发现冠状动脉狭窄.其中单支病变76例、双支病变5l例、三支病变33例.(2)152例多巴酚丁胺负荷201Tl图像发现放射性缺损的患者中,63例201Tl再分布和静息99Tcm-MIBI图像均发现放射性填充,5例201Tl再分布发现放射性填充而静息99Tcm-MIBI图像未见放射性填充,9例静息99Tcm-MIBI图像发现放射性填充而2001Tl再分布未见放射性填允,75例201Tl再分布和静息99Tcm-MIBI图像均未发现放射性填充,负荷201Tl-延迟再分布显像(66.0%,68/103)和负荷201Tl/静息99Tcm-MIBI显像(69.9%,72/103)鉴别存活心肌的灵敏度差异无统计学意义(x2=O.36,P>0.05).(3)75例201Tl再分布和静息99Tcm-MIBI图像均未发现放射性填充患者中,再注射201Tl显像后有26例放射性填充,再注射201Tl显像较单纯201Tl再分布或静息99Tcm-MIBI显像多检测出34.7%(26/75)患者有存活心肌.(4)8例多巴酚丁胺负荷201Tl、201Tl再分布图像和静息99Tcm-MIBI图像均未发现放射性稀疏,为假阴性,其中3例为三支冠状动脉病变,1例为双支冠状动脉病变(狭窄分别为90%及60%),3例为单支冠状动脉病变(狭窄<75%2例,85%1例),1例冠状动脉闭塞后有充分的侧枝循环.结论 多巴酚丁胺负荷-再分布/再注射201Tl心肌断层显像鉴别存活心肌优于多巴酚丁胺负荷201Tl/静息99Tcm-MIBI双核素同步心肌断层显像,是一种有效、无创的鉴别存活心肌的方法.     

Myocardial emission computed tomography with iodine-123-labeled beta-methyl-branched fatty acid in patients with hypertrophic cardiomyopathy.

We studied whether emission computed tomography (ECT) with 123I-labeled 15-(p-iodophenyl)-3R,S-methylpentadecanoic acid (BMIPP) shows myocardial distribution different from 201Tl in hypertrophic cardiomyopathy. In 10 patients with asymmetric septal hypertrophy (ASH), 5 with diffuse hypertrophy and 2 with apical hypertrophy, ECT was acquired 30 min (early) and 4 hr (late) after injection of 123I-BMIPP at rest and was compared with ECT with 201Tl. In 10 patients with ASH, the relative regional uptake (RRU) of the septum was lower in the early 123I-BMIPP study than in the 201Tl study, although that of the posterior wall was similar. In the early and late 123I-BMIPP studies, the RRU of the septum was lower in 10 patients with ASH than in 7 without ASH, although that of the posterior wall was similar. In the 201Tl study, however, the RRU of both the septum and posterior wall was similar in those with and without ASH. Moreover, in 16 patients, the apparent left ventricular size was larger in the early 123I-BMIPP study than in the 201Tl study, which suggested reduced 123I-BMIPP uptake in the subendocardium. In patients with hypertrophic cardiomyopathy, thus, 123I-BMIPP imaging may reveal impaired regional fatty acid utilization, which is independent of regional perfusion.     

Myocardial scintigraphy with thallium-201 and technetium-99m-hexakis-methoxyisobutylisonitrile in left bundle branch block: a study in patients with and without coronary artery disease

In left bundle branch block (LBBB) thallium-201 myocardial scintigraphy frequently reveals septal abnormalities in the absence of coronary artery disease (CAD) and gives rise to false-positive results in patients with suspected CAD. It has not yet been clarified which pathophysiological mechanism is responsible for these perfusion abnormalities. A total of 66 patients with constant LBBB were investigated with ²⁰¹T1 or technetium-99m-hexakis-methoxyisobutylisonitrile (MIBI), 62 underwent coronary angiography. Of 12 patients without left anterior descending artery (LAD) or right coronary artery (RCA) stenoses, 11 had a reversible septal activity deficit after ²⁰¹T1 stress injection, whereas 20 of 22 patients without relevant CAD showed a constant stress/rest septal deficit using MIBI. Regarding patients with significant LAD and/or RCA stenoses, both radiopharmaceuticals almost always showed a reversible septal deficit: with ²⁰¹T1 in 15 of 16 individuals and with MIBI in 14 of 15. In 12 patients ²⁰¹T1 was reinjected at rest. In those who had LAD or RCA stenoses (n = 5), early septal activity uptake after stress injection was poorer than that after rest injection; in the absence of CAD (n = 7), septal stress uptake corresponded with that of rest injection. It is concluded that septal perfusion abnormalities in LBBB and the absence of CAD are characterized by an exercise-independent reduction of septal blood flow per mass of viable myocardium and that stress/rest injection protocols of myocardial perfusion tracers are able to differentiate between LBBB with and without CAD.Dedicated to Prof. Dr. Dr. h.c. H. Hundeshagen on the occasion of his 65th birthday Correspondence to: W.H. Knapp     

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.     

Perfusion and functional abnormalities outside the septal region in patients with left bundle branch block assessed with gated SPECT.

BACKGROUND: The presence of a left bundle branch block (LBBB) pattern on the electrocardiogram may frequently lead to perfusion defects in the septum not necessarily due to ischemic heart disease, but probably due to abnormal septal wall motion. The introduction of gated single photon emission computed tomography (SPECT) allows the evaluation of myocardial perfusion and function in one study. Accordingly, we analysed perfusion and function and the relation between perfusion and regional function in the septal region in patients with a LBBB without evidence of a previously sustained myocardial infarction. METHODS: We selected 37 patients with a LBBB without a history of a previous myocardial infarction, which was confirmed by echocardiography and/or coronary angiography. All patients underwent technetium-99m tetrofosmin gated SPECT myocardial imaging. Twelve control patients with a low likelihood of coronary artery disease and a normal technetium-99m tetrofosmin gated SPECT myocardial perfusion scintigram were selected as a reference population. The left ventricle (LV) was divided into 18 segments, which were scored for perfusion and function (wall motion and wall thickening) on a 4-point scale. RESULTS: The average LV end-diastolic volume was higher and the average LV ejection fraction was lower in patients with LBBB as compared to controls (142+/-90 vs. 81+/-18 ml, and 48+/-19 vs 62+/-7%, p=0.03 and p=0.02, respectively). Not only in the septum, but also in the other segments, reduced myocardial perfusion and abnormal wall motion/wall thickening was observed in the patients with LBBB (p<0.0001 vs controls). Patients with LBBB showed no correlation between perfusion and function in the septum, and between perfusion in septum and global LV function (r=0.21, p=0.2; r=0.10, p=0.6, respectively). Conversely, a good correlation was found between perfusion and function, either regional or global, in the remote segments (both r=0.79, p<0.0001). CONCLUSIONS: We conclude that patients with LBBB without a previous myocardial infarction show cardiomyopathic changes with perfusion and wall motion abnormalities, involving the entire left ventricle. The severity of diminished septal perfusion is not directly associated with the severity of septal wall motion abnormalities or global LV function. However, in the myocardial segments remote from the septum, reduced perfusion is closely associated with functional abnormalities.     

A 201Tl perfusion defect in a case with rate-dependent left bundle-branch block (LBBB)

We present a case report of a 67-year-old woman with rate-dependent left bundle-branch block (LBBB). Although coronary angiography demonstrated no significant obstructive lesions, a reversible focal defect developed on ²⁰¹Tl myocardial scintigraphy when LBBB was induced by right-atrial pacing.     

Assessment of myocardial viability by 24-hour imaging after stress thallium-201 scintigraphy]

Twenty-four-hour delayed imaging after stress thallium-201 scintigraphy was assessed for more accurate detection of viable myocardium. Thirty-two patients with coronary artery disease who showed fixed perfusion abnormality (FPA) at 3 hr imaging after stress Tl study were evaluated with 24 hr delayed imaging. Of 37 areas with FPA, 19 areas (51%) showed redistribution (RD) at 24 hr imaging. After successful coronary artery bypass grafting (n = 19) or transluminal coronary angioplasty (n = 3), stress Tl scintigraphy was performed. Of 13 areas with RD at 24 hr imaging, 12 revealed improvement of Tl uptake after revascularization. On the other hand, of 12 areas with FPA until 24 hr, 8 showed no improvement. In conclusion, conventional stress Tl-201 scintigraphy underestimates myocardial viability, and additional 24 hr imaging permits more accurate assessment of myocardial viability.     

Is septal glucose metabolism altered in patients with left bundle branch block and ischemic cardiomyopathy?

Left bundle branch block (LBBB) is common in patients with heart failure (HF) and contributes to left ventricular (LV) dysfunction. The abnormal septal motion may alter septal metabolic demand but this has not been well characterized in patients with ischemic cardiomyopathy (ICM) and LV dysfunction. The aim of this study was to determine the effect of LBBB on septal metabolism in patients with ICM, LV dysfunction, and LBBB. METHODS: Fifty-three patients with LV dysfunction and ICM were identified: 34 with LBBB, 19 with normal QRS (30% of this patient population. Absence of this finding was often associated with lateral wall perfusion defects, suggesting an alteration in the metabolic demand on the septum. This may have implications for HF therapies such as resynchronization and requires further study.     

Prognosis in patients with left bundle branch block and normal dipyridamole thallium-201 scintigraphy

Background  The presence of complete left bundle branch block (LBBB) is commonly associated with a poorer prognosis, especially in patients with coronary artery disease (CAD). In the general population with suspected CAD and normal intraventricular conduction, a normal dipyridamole-thallium scintigraphy is a strong marker of a favorable outcome. Objective  Our objective was to assess the prognosis in patients with LBBB and a normal dipyridamole thallium-201 scintigram. Population and methods  Patients with complete LBBB and normal myocardial perfusion on dipyridamole SPECT thallium-201 scintigraphy performed in our center for suspected CAD between 1988 and 1995 were monitored for clinical events. Results  Sixty-nine patients (36 women and 33 men) with a mean age of 59 years (range 56 to 61) were monitored for a mean period of 33 months (range 25 to 35). During this period, 4 patients had unstable angina, 2 of whom underwent myocardial revascularization. There were no deaths or myocardial infarction. All events occurred at least 2 years after the thallium-201 scintigraphy. Conclusion  The presence of a normal myocardial perfusion with dipyridamole thallium-201 scintigraphy in this group of patients with suspected CAD and LBBB was associated with a very good prognosis, a low rate of clinical events occurring only 2 years after the myocardial scintigraphy, and no hard events.     

Left bundle branch block and coronary artery disease: Accuracy of dipyridamole thallium-201 single-photon emission computed tomography in patients with exercise anteroseptal perfusion defects

Background  Reduced septal or anteroseptal uptake of thallium-201 during exercise is frequently observed in patients with left bundle branch block (LBBB) even in the absence of left anterior descending (LAD) coronary artery disease. The purpose of this study was to evaluate prospectively the accuracy of dipyridamole²⁰¹TI single-photon emission computed tomography (SPECT) in detecting LAD coronary artery disease in patients with LBBB and septal or anteroseptal perfusion defects on exercise²⁰¹TI SPECT. Methods and Results  Twelve consecutive patients (10 men and two women) with complete LBBB and septal or anteroseptal perfusion defects on exercise²⁰¹TI SPECT underwent dipyridamole²⁰¹TI SPECT. The delay between dipyridamole and exercise was 2 to 30 days. Coronary angiography was performed during this period in all patients. Six (50%) of 12 patients with exercise perfusion defects showed normal perfusion after dipyridamole; all had normal coronary angiograms. The remaining six patients also had positive results of dipyridamole studies, two with moderate and four with severe septal or anteroseptal perfusion defects. Coronary angiography showed significant (>50%) LAD coronary artery stenosis in three patients; three patients with severe septal or anteroseptal perfusion defects after dipyridamole had normal coronary angiograms. Neither the evaluation of apical involvement nor the presence of dilated ventricles, decreased left ventricular ejection fraction, or wall motion abnormalities could help to identify (or explain) false-positive results. Conclusion  This study confirms that dipyridamole is more accurate than exercise in excluding LAD coronary artery disease. However, there are still false-positive results and the severity of the septal or anteroseptal perfusion defect does not add additional information to identify LAD coronary artery disease. Coronary angiography is thus necessary for positive dipyridamole study results to identify coronary artery disease as a major prognostic factor in patients with LBBB.     

Dobutamine stress thallium-201 single-photon emission tomography versus echocardiography for evaluation of the extent and location of coronary artery disease late after myocardial infarction.

Dobutamine stress echocardiography and thallium-201 myocardial perfusion scintigraphy are clinically useful methods for the evaluation of coronary artery disease (CAD). However, the relative merits of these imaging modalities in the evaluation of the extent of CAD after myocardial infarction have not been well studied. The aim of this study was to compare the accuracy of dobutamine stress echocardiography and simultaneous 201Tl single-photon emission tomography (SPET) imaging for the diagnosis and localization of CAD late after acute myocardial infarction. Dobutamine (up to 40 micrograms kg-1 min-1)-atropine (up to 1 mg) stress echocardiography in conjunction with stress-reinjection 201Tl SPET was performed for the evaluation of myocardial ischaemia in 90 patients with previous myocardial infarction who underwent coronary angiography. Significant CAD was predicted on bases of myocardial ischemia (new or worsening wall motion abnormalities on echocardiography and reversible perfusion defects on 201Tl SPET). Significant CAD (> or = 50% luminal diameter stenosis) was detected in 73 (81%) patients. The sensitivity, specificity and accuracy of echocardiography in detecting remote ischaemia for the diagnosis of remote CAD (present in 53 patients) were, respectively, 79% (CI 70%-88%), 85% (CI 77%-93%) and 81% (CI 73%-90%), while the corresponding figures for 201Tl SPET were 75% (CI 66%-85%), 78% (CI 69%-87%) and 76% (CI 67%-86%) respectively (P = NS vs echocardiography). The sensitivity, specificity and accuracy of echocardiography in detecting peri-infarction ischaemia for the diagnosis of infarct-related artery stenosis (present in 70 patients) were, respectively, 77% (CI 68%-86%), 85% (CI 78%-92%) and 79% (CI 70%-87%) while the corresponding figures for 201Tl SPET were 73% (CI 64%-82%), 85% (CI 78%-92%) and 76% (CI 67%-84%) respectively (P = NS vs echocardiography). The agreement between the two methods for the diagnosis of peri-infarction and remote ischaemia was 70% (kappa = 0.37) and 80% (kappa = 0.59) respectively. It is concluded that dobutamine stress echocardiography and 201Tl SPET have comparable accuracy for the diagnosis of infarct related and remote CAD in patients with previous myocardial infarction. The agreement between the methods is higher for the diagnosis of remote CAD than for that of peri-infarction ischaemia.     

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

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

Mechanism for abnormal thallium-201 myocardial scintigraphy in patients with left bundle branch block in the absence of angiographic coronary artery disease

Patients with left bundle branch block (LBBB) often show abnormal images on exercise thallium (T1)-201 scintigraphy without evidence of significant coronary stenosis. We investigated the mechanism for this phenomenon. Six patients with LBBB and without significant coronary stenosis underwent T1-201 SPECT, ECG-gated SPECT imaging with Tc-99m-methoxyisobutyl-isonitrile (MIBI), and atrial pacing stress test. The % count amplitude in Tc-99m-MIBI images was calculated as [(maximal counts) - (minimal counts)]/(minimal counts) x 100. Though all patients had a low count in the septal and inferior wall in T1-201 SPECT images, there was no ischemic production of lactate during an atrial pacing stress test. Nevertheless, gated SPECT images showed attenuated septal activity during systole. In patients with LBBB, the ratios of % count amplitude at the septum to that at the lateral wall at rest (0.47 +/- 0.05, mean +/- SE) were significantly less than the controls (n = 5, 0.83 +/- 0.12, p = 0.014). In conclusion, these results suggest that abnormal T1-201 SPECT images of the septum in patients with LBBB are partially caused by impaired septal wall thickening during systole. Such an abnormal wall motion may reduce blood flow demands to the septum, resulting in reduction of coronary blood flow with little ischemia.     

Value and limitation of stress thallium-201 single photon emission computed tomography: comparison with nitrogen-13 ammonia positron tomography

The diagnostic value of exercise 201Tl single photon emission computed tomography (SPECT) for assessing coronary artery disease (CAD) was comparatively evaluated with exercise [13N] ammonia positron emission tomography (PET). Fifty-one patients underwent both stress-delayed SPECT imaging using a rotational gamma camera and stress-rest PET imaging using a high resolution PET camera. Of 48 CAD patients, SPECT showed abnormal perfusion in 46 patients (96%), while PET detected perfusion abnormalities in 47 (98%). The sensitivity for detecting disease in individual coronary arteries (greater than 50% stenosis) was also similar for SPECT (81%) and PET (88%). When their interpretations were classified as normal, transient defect, and fixed defect in 765 myocardial segments, SPECT and PET findings were concordant in 606 segments (79%). However, 66 segments showed a fixed defect by SPECT but a transient defect by PET, whereas there were only nine segments showing a transient defect by SPECT and a fixed defect by PET. PET identified transient defects in 34% of the myocardial segments showing a fixed defect by SPECT. We conclude that both stress SPECT and PET showed high and similar sensitivities for detecting CAD and individual stenosed vessels. Since stress-delayed SPECT with single tracer injection detected fewer transient defects, it may underestimate the presence of myocardial ischemia, compared with high resolution PET imaging with two tracer injections.     

Comparative study of201Tl-scintigraphic image and myocardial pathologic findings in patients with dilated cardiomyopathy

The objective of the present study was to characterize the production of²⁰¹Tl myocardial perfusion defects, the relation between the²⁰¹Tl multiple small defects and the myocardial damage indicated by myocardial fibrosis shown histopathologically in patients with dilated cardiomyopathy (DCM). Rest²⁰¹Tl scintigraphy was performed in thirty-seven patients with myocardial tissue fibrosis by endomyocardial biopsy, and without stenosis of the coronary artery.²⁰¹Tl myocardial SPECT images were visually classified into 4 grades according to the severity of inhomogeneous perfusion defects (IPD), 0: none, 1: slight, 2: moderate, 3: severe.²⁰¹Tl uptake, defect regions (DR), and coefficient of variation % (CV%) were also quantified by Bull’s eye quantification in nineteen patients. During cardiac catheterization, three biopsy specimens were obtained from the lateral wall to the apical region of the left ventricle and the amount of fibrosis was assessed by means of light microscopic morphometry. The myocardial fibrosis was also classified into 4 grades by a pointcounting method. Autopsy study was also assessed in six patients.²⁰¹Tl perfusion defects were observed in 35 (94.6%) patients, of whom 29 (78.4%) showed inhomogeneous perfusion defects. Twenty-four (64.9%) showed Stage 0 and 1²⁰¹Tl findings, and 21 (62.2%) had myocardial fibrosis in stage 1. Clinically, the correlation between the grades of the IPD, %²⁰¹Tl uptake, DR and CV% of myocardial uptake, which were calculated semiquantitatively by Bull’s eye image, and the histological grades of fibrosis were also good (IPD vs. fibrosis: r = 0.7014; %²⁰¹Tl uptake vs. fibrosis: r = ?0.6542; DR vs. fibrosis: r = 0.7027; CV% vs. fibrosis: r = 0.6985). The²⁰¹Tl SPECT findings were in close agreement with the severity of myocardial fibrosis confirmed by autopsy, but the grading of the IPD was not related to the ejection fraction or left ventricular diameter. It showed a higher rate of inhomogeneous²⁰¹Tl myocardial perfusion defects (78.4%) in patients with DCM. This result may contribute to the clinical evaluation of DCM or differentiation from other diseases. Furthermore, the grading of²⁰¹Tl inhomogeneous perfusion defects related to the myocardial fibrosis of left ventricular myocardium may contribute to speculation of the myocardial degenerative stage in clinical settings.     

Clinical significance of denervated but viable myocardium in patients with recanalized acute myocardial infarction.

In patients with acute myocardial infarction (MI), myocardial sympathetic innervation evaluated by 123I-metaiodobenzylguanidine myocardial scintigraphy is more sensitive to ischaemia than the associated perfusion abnormality of 201Tl myocardial scintigraphy. The purpose of this study was to evaluate the scintigraphic indices related to the recovery of left ventricular function after acute MI. 123I-metaiodobenzylguanidine and 201Tl-chloride imaging were performed in 15 patients (mean age 60 years, 13 men and 2 women) 2 weeks after the onset of acute MI. Using a 20-segment visual interpretation of the 201Tl image, myocardial segments were classified into persistent defect, redistribution or reverse redistribution, and normal 201Tl uptake. The extent of denervated segments showed a fair correlation with the ejection fraction on admission (r = -0.53, P = 0.04), whereas the extent of persistent defect had a close correlation with the ejection fraction at 4 months (r = -0.79, P = 0.01). There was a good correlation between the extent of denervated but viable myocardium and the change in ejection fraction from admission to 4 months (r = 0.68, P = 0.01). Thus, denervated but viable myocardium is a scintigraphic index related to the functional recovery of left ventricular pump function after acute MI.     

Minimum detectable defect thickness in SPECT myocardial perfusion test: phantom study with (99m)Tc and (201)Tl.

OBJECTIVE: The purpose of this study was to determine experimentally the minimum thickness (D(min)) of a defect inserted on the myocardial wall of a cardiac phantom at different locations that could be clearly detected in a SPECT perfusion study using (99m)Tc and (201)Tl. METHODS: Rectangular (or cylindrical) defects with the same thickness were inserted on the inner surface of a myocardial phantom at 5 different locations: anterior (ANT), septal (SEP), inferoposterior (IP), lateral (LAT), and apical (AP). For different defect thickness (from 1 to 7 mm, in increments of 1 mm) the myocardial SPECT perfusion study was performed with (99m)Tc and (201)Tl using the same protocol that we use for patients. Baseline studies (with no defect inserted) were also performed. The SPECT images of the myocardial phantom with defects were compared with baseline SPECT images to determine whether the defect could be clearly identified. RESULTS: The uniformity of the baseline SPECT images was analyzed very carefully where an IP artifact was detected. The D(min) was determined for (99m)Tc and (201)Tl at 3 radii of rotation: 21.0, 25.0, and 29.2 cm. CONCLUSION: To be detected on SPECT images, a defect must be of a thickness > or =D(min). A simple method for performing a quality control test for SPECT nuclear cardiology can be developed based on these findings.