Long-term follow-up of thallium-201 myocardial scintigraphy in acute myocardial infarction--clinical significance of reverse redistribution during acute period

To clarify the viability of myocardium in acute myocardial infarction, we examined 18 patients scintigraphically. They underwent rest or stress imaging and delayed imaging of thallium-201 during acute, convalescent and chronic periods. During acute period, a scintigraphic finding of the delayed filling in was observed in 9 cases (50%; Redistribution group). Worsening of the delayed image was observed in 6 cases (33%; Reverse redistribution group). No scintigraphic change of the perfusion defect was observed in 3 cases (17%; No change group). In reverse redistribution group, a remarkable improvement of the delayed image was observed through acute, convalescent and chronic periods. In redistribution group and no change group, no significant improvement was observed. We conclude that the myocardium of the reverse redistribution region during acute period may be viable. In the reverse redistribution region, recanalization of the coronary artery possibly protects myocardial damage from necrosis.     

Assessment of myocardial damage in dilated-phase hypertrophic cardiomyopathy by using indium-111-antimyosin Fab myocardial scintigraphy

For the detection of myocardial cell damage, an 111In-antimyosin Fab study was carried out on seven patients (Group A) in the dilated phase of hypertrophic cardiomyopathy, seven patients (Group B) with dilated cardiomyopathy, and eight control patients (Group C). Imaging was done 48 hr after intravenous injection of 74 MBq of 111In-antimyosin Fab. Myocardial antimyosin uptake was visually graded as 0, +1, +2 or +3. A score of +2 or +3 was considered positive. The heart/lung ratio of antimyosin uptake (antimyosin index) also was determined. Antimyosin uptake was positive in seven (100%), nine (90%) and no (0%) patients in Groups A, B, and C, respectively. The antimyosin index in Groups A and B was 2.46 +/- 0.49 and 2.04 +/- 0.24, respectively, findings were significantly higher than that in Group C (1.51 +/- 0.13) (p less than 0.01). Positive biopsy findings were noted in only two patients in Group A. Thus, antimyosin uptake was increased in dilated phase hypertrophic cardiomyopathy and dilated cardiomyopathy, which suggests ongoing necrotic changes in these patients.     

Exercise myocardial perfusion scintigraphy is useful for evaluating myocardial ischemia even in the elderly

Pharmacologic stress testing is recommended to elderly patients as a valuable alternative to exercise testing. We examined whether exercise testing is as useful for evaluating myocardial ischemia in the elderly as in the young. The consecutive 1,508 patients who underwent exercise 201Tl single-photon emission computed tomography (SPECT) were divided into six age groups: 6-29 years (n = 56), 30-44 (n = 143), 45-54 (n = 311), 55-64 (n = 498), 65-74 (n = 402), and 75-88 (n = 98). Both heart rate and rate-pressure product at peak exercise were significantly lower in patients aged 75-88 than in the other five groups. The frequency of ischemic ST depression was higher in patients aged 75-88 than in those aged 6-74, although the difference was not significant. Moreover, the frequency of 201Tl transient defect was significantly higher in patients aged 75-88 than in those aged 6-74. On the other hand, the sensitivity of ischemic ST depression for 201Tl transient defect was similar among the six groups, but the specificity was significantly lower in patients aged 75-88 than in those aged 6-74. In conclusion, exercise 201Tl SPECT is useful for evaluating myocardial ischemia even in the elderly, but exercise electrocardiography has limitations such as lower specificity in the elderly than 201Tl SPECT.     

Reverse redistribution of Tc-99m-tetrofosmin in exercise myocardial SPECT in patients with hypertrophic cardiomyopathy

We examined the usefulness of Tc-99m-tetrofosmin in detecting exercise induced perfusion abnormalities in patients with hypertrophic cardiomyopathy (HCM) and to clarify time-related changes in myocardial distribution of Tc-99m-tetrofosmin after a single injection. We studied 44 consecutive patients with HCM by means of exercise/rest Tc-99m-tetrofosmin single photon emission computed tomography (SPECT). After injecting 370 MBq of Tc-99m-tetrofosmin at the peak exercise, the early SPECT imaging was performed at 30 min (EX-30) and the delayed imaging at 180 min (EX-180). Immediately after the delayed imaging, 740 MBq of Tc-99m-tetrofosmin was injected in the resting state, and the rest SPECT imaging was performed 30 min later. Exercise-induced regional perfusion defects and/or apparent reversible left ventricular cavity dilation were identified in 26 (68.2%) of the 44 patients. When EX-30 images and EX-180 images were compared, reverse redistribution was confirmed in 36 patients (81.8%). Reverse redistribution was detected most frequently in the septal portion of the anterior wall, followed by the septal portion of the posterior wall and the septum. Exercise/rest Tc-99m-tetrofosmin myocardial imaging was a useful method for assessing myocardial perfusion abnormalities in patients with HCM. Reverse redistribution was detected very frequently on early and delayed images of exercise. We assumed that reverse redistribution may reflect a retention disorder of Tc-99m-tetrofosmin caused by some metabolic dysfunction of myocytes.     

Idiopathic hypertrophic sub-aortic stenosis (IHSS): a new diagnostic method using ECG-gated thallium-201 myocardial scintigraphy

A new diagnostic method for idiopathic hypertrophic sub-aortic stenosis (IHSS), using synchronized ECG gated 201Tl myocardial scintigraphy, is described. Twenty patients previously diagnosed as IHSS were evaluated by sequential three-view ECG gated 201Tl and 45 degrees left anterior oblique multigated (MUGA) cardiac blood pool imaging (Group A). The results were compared with two control groups: 20 patients with no previous history of heart disease (Group B), and 20 patients with coronary ischaemic heart disease (Group C). We suggest the following combination of scintigraphic signs as typical and diagnostic to obstructive IHSS: Elevated left ventricular ejection fraction (mean 83.9% +/- 6.15S.D. versus 72.5% +/- 5.35S.D. and 51.2% +/- 13.65S.D. in Groups B and C respectively); Systolic left ventricular cavity obliteration (71% of obstructive IHSS patients versus 0% in Groups B and C); A ratio of more than 1.3:1 in septal to free wall thickness (100% of patients with IHSS); Perfusion/wall-motion mismatch of septum was demonstrated in all (100%) of patients with IHSS (versus 0% in Group B and 10% in Group C). We suggest this last finding as a new specific diagnostic sign for IHSS, with the ability to differentiate between patients with ischaemic coronary heart disease and IHSS patients; whilst both groups may present chest pains, the first group was characterized by 'matching' of perfusion and motion of the affected myocardial wall while the patients with IHSS had 'mismatching' of these parameters. We suggest gated 201Tl myocardial scintigraphy as an additional sensitive tool for the early diagnosis and evaluation of IHSS patients.     

Clinical significance of I-123 MIBG myocardial scintigraphy for evaluating the severity of congestive heart failure

We studied the significance of I-123 MIBG (metaiodobenzylguanidine) myocardial scintigraphy for evaluating the severity of congestive heart failure. I-123 MIBG scintigraphy was performed in 7 patients with congestive heart failure (CHF) of NYHA class I-III (6 with dilated cardiomyopathy and 1 with Adriamycine cardiomyopathy) and in 2 normals. The SPECT and anterior planar myocardial images were obtained 15 minutes after (initial images) and 4 hours after (delayed images) an injection of I-123 MIBG (111 MBq). Compared with normals, patients with CHF demonstrated (1) low myocardial uptake and (2) rapid myocardial washout of I-123 MIBG, indicating myocardial sympathetic disarrangement. Then, quantitating these abnormalities with the heart to upper mediastinum uptake ratio (H/B) and the percent washout rate (%WR) during 4 hours, respectively, we compared these two indices with LV ejection fraction (EF) at rest measured by echocardiography and exercise capacity (max VO2 and VO2 at anaerobic threshold (AT] determined with respiratory gas exchange analysis during maximal bicycle exercise. H/B was lower and %WR was greater in patients with CHF than in normals. H/B correlated with EF (r = 0.77, p less than 0.05) and AT (r = 0.74, p less than 0.05). On the other hand, %WR significantly correlated with EF (r = 0.79, p less than 0.05), max VO2 (r = -0.74, p less than 0.05) and AT (r = -0.81, p less than 0.05). Thus, H/B and %WR were closely related to the severity of CHF. These results suggest that I-123 MIBG myocardial scintigraphy and the quantitative analysis of I-123 MIBG myocardial uptake provide useful information about the severity of CHF.     

Sodium bicarbonate-augmented stress thallium myocardial scintigraphy

It is well known that sodium bicarbonate in pharmacological doses induces transient alkalosis, causing intracellular transport of serum potassium. The aims of this study were (a) to investigate whether, in humans, myocardial thallium-201 uptake can be augmented by pretreatment with a single bolus of sodium bicarbonate at a pharmacological dose, (b) to verify general safety aspects of the intervention and (c) to evaluate the clinical implications of augmentation of ²⁰¹Tl uptake, if any. Routine exercise myocardial scintigraphy was performed twice in eight adult volunteers (five normal and three abnormal), once without intervention and the second time (within a week) following intravenous administration of sodium bicarbonate (88 mEq in 50 ml) as a slow bolus 1 h prior to the injection of ²⁰¹Tl. Conventional myocardial thallium study was compared with sodium bicarbonate interventional myocardial scintigraphy with respect to myocardial uptake (counts per minute per mCi injected dose), washout patterns in normal and abnormal myocardial segments, and overall clinical interpretation based on planar and single-photon emission tomographic (SPET) images. All patients remained asymptomatic after the intervention. A mean increase of 53% in myocardial uptake of thallium was noted in post-exercise acquisitions after the intervention, confirming uptake of the tracer via the potassium-hydrogen pump and its augmentation by transient alkalosis. The washout pattern remained unchanged. The visual quality of planar and SPET images improved significantly after the intervention. Out of the five abnormal myocardial segments identified in three cases, four showed significant filling-in after the intervention, causing the diagnosis to be upgraded from partial scar to ischaemia, or from ischaemia to normal. The overall scan impression changed in two out of three such cases. Sodium bicarbonate augmentation may have significant implications for stress-thallium scintigraphy and may be a new parameter for defining myocardial viability.     

Effect of ribose on thallium-201 myocardial redistribution

Myocardial 201Tl redistribution after transient ischemia may be too slow to allow identification of a reversible myocardial defect within the routine 201Tl imaging period. To determine whether 201Tl redistribution could be affected by a metabolic intervention, intravenous ribose was administered postischemia. Seventeen domestic swine were subjected to a 10-min ischemic period followed by either a 30-min i.v. ribose (n = 8) or saline (n = 9) infusion. Thallium-201 was injected during ischemia and myocardial 201Tl activity was continuously monitored in ischemic and nonischemic regions with miniature CdTe radiation detection probes. Coronary flow in the ischemic region was reduced to 25% of that in the nonischemic regions in both saline and ribose groups. The 201Tl time-activity curves demonstrated a significant enhancement of % 201Tl redistribution in the ribose-treated animals at the end of ribose infusion: Ribose (48 +/- 11%), Saline (20 +/- 4%), p less than 0.05. Alteration of 201Tl kinetics by ribose may permit earlier recognition of 201Tl myocardial redistribution after transient ischemia.     

Clinical validation of simultaneous dual-isotope myocardial scintigraphy

Simultaneous dual-isotope (rest thallium-201/stress technetium-99m sestamibi) myocardial single-photon emission tomography (SPET) would be an ideal procedure; however, (99m)Tc cross-talk on the (201)Tl window hampers its routine use. Photon energy recovery (PER) is a spectral deconvolution technique validated for scatter and cross-talk removal in phantom studies and a limited series of patients. In this study we aimed to validate the technique in 295 patients within a context of clinical routine practice. Conventional separate rest (201)Tl myocardial SPET data sets were visually compared with simultaneous dual-isotope data sets corrected by PER. Conventional separate rest (201)Tl data sets were identical to dual PER-corrected (201)Tl data sets in 173 (58.6%) patients. As dual PER (201)Tl data sets are corrected for (99m)Tc cross-talk but also for (201)Tl scatter, they were compared with separate rest (201)Tl data sets corrected by PER in the 122 discordant patients. No difference was found in 77 (26.1%) patients. In 26 (8.8%) patients, the difference consisted in the presence of a defect on dual PER (201)Tl data sets only, mirroring an ischaemic defect on (99m)Tc-sestamibi data sets. This difference can be attributed to the influence of stress on the kinetics of (201)Tl injected at rest. In the remaining 19 (6.4%) patients, the difference between separate and simultaneous PER-corrected data sets was scored as mild in 11 and moderate in eight patients and seemed to be related to multiple methodological factors. It is concluded that PER correctly removes (99m)Tc cross-talk. With the addition of an appropriate attenuation correction, the PER technique may allow the routine use of simultaneous dual-isotope myocardial scintigraphy in the near future.     

Reverse redistribution: Revisited with myocardial contrast echocardiography

The aim of this study is to better understand the pattern and nature of reverse redistribution (RR) in myocardial perfusion imaging. In 20 consecutive acute myocardial infarction (MI) patients, frequency of RR was correlated with that of subendocardial MI that was detected by myocardial contrast echocardiography (MCE). RR was judged to be present when there was more than one grade of worsening in perfusion on 24 hr delayed images compared with the initial rest images. MCE evaluated no opacification in the subendocardial myocardium to suggest subendocardial MI. Kendall's nonparametric correlation coefficiency was calculated. Concordant cases were 15 of 20 (75%) and correlation was statistically significant (p = 0.0285). Our results suggested that RR was correlated with MCE-detected nontransmural MI.