Assessment of Takotsubo cardiomyopathy (transient left ventricular apical ballooning) using99mTc-tetrofosmin,123I-BMIPP,123I-MIBG and99mTc-PYP myocardial SPECT

We compared Takotsubo cardiomyopathy (transient left ventricular apical ballooning) with acute myocardial infarction (AMI) using two-dimensional echocardiography, 99mTc-tetrofosmin, 99mTc-PYP, 123I-BMIPP and 123I-MIBG myocardial SPECT. METHODS: We examined 7 patients with Takotsubo cardiomyopathy and 7 with AMI at the time of emergency admission (acute phase), and 2-14 days (subacute phase), one month (chronic phase), and 3 months (chronic II phase) after the attack. The left ventricle was divided into nine regions on echocardiograms and SPECT images, and the degree of abnormalities in each region was scored according to five grades from normal (0) to severely abnormal (4). RESULTS: Coronary angiography showed the absence of stenotic regions in patients with Takotsubo cardiomyopathy, and severely stenotic and/or occlusive lesions in patients with AMI. The total ST segment elevation on electrocardiograms (mm) was 7.8 +/- 3.7 in those with Takotsubo cardiomyopathy, and 7.3 +/- 3.9 in patients with AMI. Abnormal wall motion scores on echocardiograms were 14.2 +/- 4.6, 4.7 +/- 4.0, 1.7 +/- 2.0 and 0.5 +/- 0.4 during the acute, subacute, chronic and chronic II phases, respectively, in patients with Takotsubo cardiomyopathy, and 14.0 +/- 4.3, 11.4 +/- 3.9, 8.8 +/- 3.6 and 5.2 +/- 4.8 in those with AMI. Abnormal myocardial perfusion scores on 99mTc-tetrofosmin images were 11.8 +/- 3.5, 3.2 +/- 3.0, 0.5 +/- 1.2 and 0.2 +/- 0.4 during the acute, subacute, chronic and chronic II phases, in patients with Takotsubo cardiomyopathy, and 16.2 +/- 4.3, 13.9 +/- 4.6, 7.9 +/- 4.6 and 5.0 +/- 4.5, respectively, in those with AMI. Abnormal myocardial fatty acid scores on 123I-BMIPP images were 12.6 +/- 3.7, 6.8 +/- 3.2 and 0.4 +/- 0.6 during the subacute, chronic and chronic II phases, respectively, in patients with Takotsubo cardiomyopathy, and 16.5 +/- 5.1, 14.7 +/- 4.8 and 7.5 +/- 4.5 in those with AMI. Abnormal myocardial sympathetic nerve function scores on 123I-MIBG images were 14.8 +/- 4.0, 8.8 +/- 4.0 and 0.4 +/- 0.6 during the subacute, chronic, chronic II phases, respectively, in patients with Takotsubo cardiomyopathy, and 18.6 +/- 6.5, 16.8 +/- 6.8 and 12.9 +/- 5.2 in those with AMI. Myocardial 99mTc-PYP uptake was abnormal not only in patients with AMI but also in those with Takotsubo cardiomyopathy during the acute phase. CONCLUSIONS: Takotsubo cardiomyopathy might represent a stunned myocardium caused by a disturbance of the coronary microcirculation.     

MRI for the diagnosis of left ventricular apical ballooning syndrome (LVABS)

To compare MRI findings of left ventricular apical ballooning syndrome (LVABS) with those of acute myocardial infarction (AMI). Fifteen patients with a LVABS (group 1) and 25 patients with an AMI (group 2) were explored by MRI within 24 h after admission. Comparison of both groups for the number and location of myocardial segments with abnormal wall motion and abnormal perfusion or delayed enhancement was performed. The number of involved segments was higher in group 1 than in group 2 (p < 0.001). In group 1, segments with abnormal wall motion were distributed in more than one vascular territory in all patients and confined to the medial, distal, and apical regions of the left ventricle. Subendocardial hypoenhancement was observed in 16/25 patients (64%) in group 2 and in none of group 1 (p < 0.001). All patients in group 2 demonstrated delayed-enhancement abnormalities in a vascular distribution, whereas none in group 1 presented this abnormality (p < 0.001). Diffusely distributed segmental wall-motion abnormalities and absence of first-pass perfusion hypoenhancement and of delayed enhancement at MRI help to differentiate LVABS from AMI. In the acute phase or in some difficult cases, cardiac MRI should become routine to confirm the diagnosis of LVABS.     

Relation between myocardial response to dobutamine stress and sympathetic nerve activation in patients with idiopathic dilated cardiomyopathy: A comparison of123I-MIBG scintigraphic and echocardiographic data

It is likely that a close association exists between findings obtained by two methods: dobutamine stress echocardiography and 123I-MIBG scintigraphy. Both of these methods are associated with beta-adrenergic receptor mechanisms. This study was conducted to demonstrate the relation between myocardial response to dobutamine stress and sympathetic nerve release of norepinephrine in the failing heart. In 12 patients with heart failure due to idiopathic dilated cardiomyopathy, the myocardial effects of dobutamine stress were evaluated by low-dose dobutamine stress echocardiography: and sympathetic nerve function was evaluated by scintigraphic imaging with iodine-123 [123I] meta-iodobenzylguanidine (MIBG), an analogue of norepinephrine. Echocardiography provided quantitative assessment of wall motion and left ventricular dilation; radiotracer studies with 123I-MIBG provided quantitative assessment of the heart-to-mediastinum (H/M) uptake ratio and washout rate. Results showed that H/M correlated with baseline wall motion (r = 0.682, p = 0.0146), wall motion after dobutamine stress (r = 0.758, p = 0.0043), the change in wall motion (r = 0.667, p = 0.0178), and with left ventricular diastolic diameter (r = 0.837, p = 0.0007). In addition, the 123I-MIBG washout rate correlated with baseline wall motion (r = 0.608, p = 0.0360), wall motion after dobutamine stress (r = 0.703, p = 0.0107), and with the change in wall motion (r = 0.664, p = 0.0185). Wall motion, especially in the myocardial response to dobutamine stress, is related to sympathetic nerve activity in heart failure.     

Simultaneous assessment of Tc-99m-sestamibi and I-123-BMIPP myocardial distribution in patients with myocardial infarction: Evaluation of left ventricular function with ECG-gated myocardial SPECT

123I-labeled 15-(p-iodophenyl)-3R,S-methyl pentadecanoic acid (BMIPP) is a branched-chain free fatty acid that is used to evaluate various cardiac diseases. The aim of the present study was to investigate the relationship between myocardial perfusion (99mTc-sestamibi) and BMIPP uptake, and to correlate perfusion and metabolic alterations with regional left ventricular dysfunction in patients with myocardial infarction (MI). ECG-gated dual-isotope myocardial SPECT was performed on 130 patients with MI with sestamibi (555 MBq) and BMIPP (148 MBq). The patients were classified into 3 groups according to PTCA therapy and the interval between the onset of infarction and RI injection (OR time). Group A (n = 56) included patients whose OR time was less than one month and who had undergone successful PTCA, Group B (n = 36) had OR times of less than one month and had conservative medical therapy, and Group C (n = 38) had OR times of over one month. The severity scores of the dual-isotope images were calculated from the defect scores in 9 segments. From the ECG-gated SPECT data with sestamibi, the left ventricular ejection fraction (LVEF; %) and regional wall motion were determined automatically using the QGS program LVEF obtained from gated SPECT correlated well with the severity scores for sestamibi and BMIPP (r = -0.68 and -0.76, respectively). The delta severity scores (BMIPP scores - sestamibi scores) of Group A were significantly higher than those of the other two groups (3.6 +/- 3.0 vs. 1.5 +/- 1.7 and 1.0 +/- 1.4, p < 0.001 ). The rate of dysfunctional segments with normal sestamihi distribution was significantly higher in Group A than in Group C (20.7% vs. 6.7%, p < 0.001). ECG-gated dual-isotope SPECT is useful since myocardial perfusion, fatty acid metabolism and left ventricular function can be analyzed during a single examination, so that this procedure has the potential to provide comprehensive information when evaluating patients with ischemic heart disease.     

Serial change of iodine-123 metaiodobenzylguanidine (MIBG) myocardial concentration in patients with dilated cardiomyopathy

Serial change of the metaiodobenzylguanidine iodine-123 (¹²³I-MIBG) myocardial concentration was investigated in patients with dilated cardiomyopathy (DCM). Eight DCM patients and 6 control subjects were examined. After the injection of thallium-201 and ¹²³I-MIBG, planar chest images were obtained simultaneously for both tracers in every 30–60 min over 5 h. Serial changes of myocardial uptake ratio (MUR) were compared for both tracers. In DCM, the initial MUR of ¹²³I-MIBG did not differ significantly from that of the controls. The washout of ¹²³I-MIBG from the myocardium, however, was significantly increased in DCM. In particular, the decrease in the early phase (15–45 min) was significantly larger in DCM than in the controls (21.2%±7.5% vs. 5.3%±4.0%, P <0.01), showing a significant negative correlation with the left ventricular ejection fraction (r = –0.72 P < 0.05). For ²⁰¹TI, neither the initial MUR nor the washout rate different significantly between the two. Thus, an early rapid decrease of the ¹²³I-MIBG myocardial concentration might characterize DCM and reflect the severity of this disease. Offprint requests to: K. Yamakado     

Clinical performance and radiation dosimetry of no-carrier-added vs carrier-added 123I-metaiodobenzylguanidine (MIBG) for the assessment of cardiac sympathetic nerve activity

Purpose We hypothesized that assessment of myocardial sympathetic activity with no-carrier-added (nca) ¹²³I-meta-iodobenzylguanidine (MIBG) compared to carrier-added (ca) ¹²³I-MIBG would lead to an improvement of clinical performance without major differences in radiation dosimetry. Methods In nine healthy volunteers, 15 min and 4 h planar thoracic scintigrams and conjugate whole-body scans were performed up to 48 h following intravenous injection of 185 MBq ¹²³I-MIBG. The subjects were given both nca and ca ¹²³I-MIBG. Early heart/mediastinal ratios (H/M), late H/M ratios and myocardial washout were calculated. The fraction of administered activity in ten source organs was quantified from the attenuation-corrected geometric mean counts in conjugate views. Radiation-absorbed doses were estimated with OLINDA/EXM software. Results Both early and late H/M were higher for nca ¹²³I-MIBG (ca ¹²³I-MIBG early H/M 2.46 ± 0.15 vs nca ¹²³I-MIBG 2.84 ± 0.15, p = 0.001 and ca ¹²³I-MIBG late H/M 2.69 ± 0.14 vs nca ¹²³I-MIBG 3.34 ± 0.18, p = 0.002). Myocardial washout showed a longer retention time for nca ¹²³I-MIBG (p < 0.001). The effective dose equivalent (adult male model) for nca ¹²³I-MIBG was similar to that for ca ¹²³I-MIBG (0.025 ± 0.002 mSv/MBq vs 0.026 ± 0.002 mSv/MBq, p = 0.055, respectively). Conclusion No-carrier-added ¹²³I-MIBG yields a higher relative myocardial uptake and is associated with a higher myocardial retention. This difference between nca ¹²³I-MIBG and ca ¹²³I-MIBG in myocardial uptake did not result in major differences in estimated absorbed doses. Therefore, nca ¹²³I-MIBG is to be preferred over ca ¹²³I-MIBG for the assessment of cardiac sympathetic activity.     

Impact of sympathetic innervation on recurrent life-threatening arrhythmias in the follow-up of patients with idiopathic ventricular fibrillation

Purpose Idiopathic ventricular fibrillation (IVF) is defined as VF in the absence of any identifiable structural or functional cardiac disease. The underlying pathophysiological mechanisms are unknown. This study was performed to investigate the potential impact of sympathetic dysfunction, assessed by ¹²³I-meta-iodo-benzylguanidine scintigraphy (¹²³I-MIBG SPECT), on the long-term prognosis of patients with IVF.Methods ¹²³I-MIBG SPECT was performed in 20 patients (mean age 37±13 years) with IVF. Mean follow-up of patients after study entry was 7.2±1.5 years (range 4.9–10.5 years). Ten patients (five men, five women; mean age 43±12 years; p=NS versus study group) with medullary carcinoma of the thyroid gland served as an age-matched control group.Results Abnormal ¹²³I-MIBG uptake was observed in 13 patients (65%). During follow-up, 18 episodes of VF/fast polymorphic ventricular tachycardias occurred in four IVF patients with abnormal ¹²³I-MIBG uptake whereas only two episodes of monomorphic ventricular tachycardia (and no VF) occurred in a single IVF patient with normal ¹²³I-MIBG uptake.Conclusion Impairment of sympathetic innervation may indicate a higher risk of future recurrent episodes of life-threatening ventricular tachyarrhythmias in patients with IVF. Studies in larger cohorts are required to validate the significance of ¹²³I-MIBG SPECT during the long-term follow-up of these patients.The first two named authors contributed equally to this work.     

Technetium-99m pyrophosphate/thallium-201 dual-isotope SPECT imaging predicts reperfusion injury in patients with acute myocardial infarction after reperfusion

Purpose  Microcirculatory failure after reperfusion is clinically indicated to cause reperfusion injury whereas excessive intracellular calcium ion overload is experimentally proved as a key mechanism of reperfusion injury. We hypothesized that technetium-99m (^99mTc) pyrophosphate (Tc-PYP) uptake in injured but viable infarct-related myocardium with preserved myocardial perfusion after reperfusion estimated by thallium-201 (²⁰¹Tl) uptake would be associated with final functional recovery. Methods  Dual-isotope Tc-PYP/²⁰¹Tl single-photon emission computed tomography (SPECT) was performed 2 days after successful reperfusion therapy in patients with first acute myocardial infarction, and 50 patients (63 ± 13 years old, female 22%) with preserved ²⁰¹Tl uptakes of ≥50% in reperfused myocardium was followed for 1 month. Tc-PYP uptake was assessed as the heart-to-sternum (H/S) ratio. Two-dimensional echocardiography was also performed 2 days and 1 month after reperfusion to evaluate functional recovery. Results  High Tc-PYP uptake, defined as the H/S ratio ≥0.81, was predictive of chronic phase no functional recovery (73.7% in 14 of 19 patients with high uptake vs 16.1% in five of 31 patients without those, p < 0.0001). After adjustment for potential confounding variables, including electrocardiographic persistent ST segment elevation at 1 h after reperfusion, high Tc-PYP uptake remained independently predictive of no functional recovery with odds ratio of 8.7 (95% confidential interval = 2 to 38.7; p = 0.005). Conclusion  High Tc-PYP uptake in reperfused but viable infarct-related myocardium was a powerful predictor of no functional recovery, which may reflect excessive intracellular calcium ion overload caused by reperfusion injury. Tc-PYP/²⁰¹Tl dual-isotope SPECT imaging can provide prognostic information after reperfusion.     

Dynamic123I-MIBG SPECT reflects sympathetic nervous integrity and predicts clinical outcome in patients with chronic heart failure

123I-metaiodobenzylguanidine (123I-MIBG) is useful for assessment of the severity and prognosis of patients with chronic heart failure (CHF). To examine 123I-MIBG kinetics in the early phase soon after tracer injection, we performed dynamic single photon emission computed tomography (SPECT) in 76 patients with CHF and 17 control subjects. The consecutive 15 images of 2 min-dynamic SPECT were acquired for 30 min after injection. From 0 to 4 min, a significant amount of radioactivity existed in the blood pool, thus we calculated washout rate of 123I-MIBG from 4 to 30 min (%WR-E). Patients were followed up with an end-point of cardiac death or re-hospitalization for 16 months (6-30 months). As the NYHA functional class advanced, %WR-E increased (control, NYHA class I, II, and III: 9 +/- 4%, 10 +/- 5%, 12 +/- 5%, and 17 +/- 5%*, respectively, *p < 0.01 vs. all other groups). Significant correlation was found between %WR-E and conventional WR from 30 min to 240 min (r = 0.606, p < 0.0001). %WR-E was positively correlated with left ventricular end-diastolic dimension (r = 0.372, p < 0.01) and was inversely correlated with left ventricular fractional shortening (r = -0.316, p < 0.02). The normal upper limit of %WR-E was defined as mean + 2SD value of 17 control subjects (17.1%). Patients with abnormally rapid %WR-E levels had a higher cardiac event rate than those with normal %WR-E levels (57% vs. 12%, p < 0.0001). These data suggest that washout rate of 123I-MIBG in the early phase from 4 min to 30 min (%WR-E) reflects cardiac sympathetic nervous integrity and is useful to evaluate the severity and prognosis of patients with CHF. The present results indicate a potential role of dynamic SPECT in shortening the 123I-MIBG imaging protocol.     

Anti-tachycardia therapy can improve altered cardiac adrenergic function in tachycardia-induced cardiomyopathy

We investigated whether anti-tachycardia therapy might improve the altered cardiac adrenergic and systolic function in tachycardia-induced cardiomyopathy (TC) in contrast to dilated cardiomyopathy (DCM). The subjects were 23 patients with heart failure, consisting of 8 patients with TC (43.6 +/- 10.0 yrs) and 15 with DCM (45.3 +/- 8.2 yrs). TC was determined as impairment of left ventricular function secondary to chronic or very frequent arrhythmia during more than 10% of the day. All patients were receiving anti-tachycardia treatment. Cardiac 123I-MIBG uptake was assessed as the heart/mediastinum activity ratio (H/M) before and after treatment. LVEF was also assessed. In the baseline study, H/M and LVEF showed no difference between TC and DCM (2.21 +/- 0.44 vs. 2.10 +/- 0.42, 35.3 +/- 13.1 vs. 36.0 +/- 10.9%, respectively). After treatment, the degree of change in H/M and LVEF differed significantly (0.41 +/- 0.34 vs. 0.08 +/- 0.20, 20.5 +/- 14.4 vs. -2.1 +/- 9.6%, p < 0.01). In TC, heart failure improved after a shorter duration of treatment (p < 0.05). In conclusion, anti-tachycardia therapy can improve altered cardiac adrenergic function and systolic function in patients with TC over a shorter period than in those with DCM.     

Effects of perindopril on cardiac sympathetic nerve activity in patients with congestive heart failure: comparison with enalapril

Purpose The production of aldosterone in the heart is suppressed by the angiotensin-converting enzyme (ACE) inhibitor perindopril in patients with congestive heart failure (CHF). Moreover, perindopril has been reported to have more cardioprotective effects than enalapril.Materials and methods Forty patients with CHF [left ventricular ejection fraction (LVEF) <45%; mean 33±7%] were randomly assigned to perindopril (2 mg/day; n=20) or enalapril (5 mg/day; n=20). All patients were also treated with diuretics. The delayed heart/mediastinum count (H/M) ratio, delayed total defect score (TDS) and washout rate (WR) were determined from ¹²³I-meta-iodobenzylguanidine (MIBG) images, and plasma brain natriuretic peptide (BNP) concentrations were measured before and 6 months after treatment. The left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV) and LVEF were also determined by echocardiography.Results After treatment, in patients receiving perindopril, TDS decreased from 39±10 to 34±9 (P<0.01), H/M ratios increased from 1.62±0.27 to 1.76±0.29 (P<0.01), WR decreased from 50±14% to 42±14% (P<0.05) and plasma BNP concentrations decreased from 226±155 to 141±90 pg/ml (P<0.0005). In addition, the LVEDV decreased from 180±30 to 161±30 ml (P<0.05) and the LVESV decreased from 122±35 to 105±36 ml (P<0.05). Although the LVEF tended to increase, the change was not statistically significant (from 33±8% to 36±12%; P=NS). On the other hand, there were no significant changes in these parameters in patients receiving enalapril.Conclusion Plasma BNP concentrations, ¹²³I-MIBG scintigraphic and echocardiographic parameters improved after 6 months of perindopril treatment. These findings indicate that perindopril treatment can ameliorate the cardiac sympathetic nerve activity and the left ventricular performance in patients with CHF.     

Quantitation of cardiac sympathetic innervation in rabbits using 11C-hydroxyephedrine PET: relation to 123I-MIBG uptake

Purpose Although ¹¹C-hydroxyephedrine (¹¹C-HED) PET is used to map cardiac sympathetic innervation, no studies have shown the feasibility of quantitation of ¹¹C-HED PET in small- to medium-sized animals. Furthermore, its relation to ¹²³I-MIBG uptake, the most widely used sympathetic nervous tracer, is unknown. The aims of this study were to establish in vivo sympathetic nerve imaging in rabbits using ¹¹C-HED PET, and to compare the retention of ¹¹C-HED with that of ¹²³I-MIBG.Methods Twelve rabbits were assigned to three groups; control (n=4), chemical denervation by 6-hydroxydopamine (6-OHDA) (n=4) and reserpine treated to inhibit vesicular uptake (n=4). After simultaneous injection of ¹¹C-HED and ¹²³I-MIBG, all animals underwent dynamic ¹¹C-HED PET for 40 min with arterial blood sampling. The ¹¹C-HED retention fraction and normalised ¹¹C-HED activity measured by tissue sampling were compared with those measured by PET.Results Both the ¹¹C-HED retention fraction and the normalised ¹¹C-HED activity measured by PET correlated closely with those measured by tissue sampling (R=0.96027, p<0.001 and R=0.97282, p<0.001, respectively). Inhibition study by 6-OHDA resulted in a significant reduction in retention (90%) for both ¹¹C-HED and ¹²³I-MIBG. Reserpine pretreatment reduced ¹¹C-HED retention by 50%, but did not reduce ¹²³I-MIBG retention at 40 min after injection.Conclusion Non-invasive quantitation of cardiac sympathetic innervation using ¹¹C-HED PET is feasible and gives reliable estimates of cardiac sympathetic innervation in rabbits. Additionally, although both ¹¹C-HED and ¹²³I-MIBG are specific for sympathetic neurons, ¹¹C-HED may be more specific for intravesicular uptake than ¹²³I-MIBG in some situations, such as that seen in reserpine pretreatment.     

Assessment of ampulla (Takotsubo) cardiomyopathy with coronary angiography, two-dimensional echocardiography and 99mTc-tetrofosmin myocardial single photon emission computed tomography

We studied the causative mechanism of ampulla (Takotsubo) cardiomyopathy. METHODS: We examined 7 patients with ampulla cardiomyopathy by means of coronary angiography, two-dimensional echocardiography and 99Tc-tetrofosmin myocardial SPECT at the time of emergency admission (acute phase), at 3 to 5 days after the attack (subacute phase) and at 1 month after the attack (chronic phase). The left ventricle was divided into 9 regions on two-dimensional echocardiograms and 99mTc-tetrofosmin myocardial SPECT images, then the degree of abnormalities in each region was scored in four grades from normal (0) to severely abnormal (3). We injected nicorandil into the coronary arteries and determined the elevation in the ST segment before and after administration. RESULTS: Coronary angiography did not show stenotic lesions in any patient. The acute, subacute and chronic phase myocardial perfusion scores on 99mTc-tetrofosmin myocardial SPECT were 11.2 +/- 3.4, 2.7 +/- 2.3 and 0.4 +/- 0.5, respectively, and wall motion scores on echocardiograms were 13.0 +/- 3.6, 4.4 +/- 2.2 and 0.6 +/- 0.6, respectively, indicating improvement in all scores during the subacute phase (p < 0.01). The elevation in the ST segment (mm) on the electrocardiogram was improved from 8.3 +/- 2.7 to 4.9 +/- 1.9 after the administration of nicorandil (p < 0.05). CONCLUSION: These findings indicated that coronary microvascular spasm is one causative mechanism of ampulla cardiomyopathy.     

Comparison of emory and cedars-sinai methods for assessment of left ventricular function from gated myocardial perfusion SPECT in patients with a small heart

To evaluate the effect of left ventricular (LV) size on the calculation of LV function from gated myocardial SPECT with Emory and Cedars-Sinai programs, we performed 99mTc-tetrofosmin gated SPECT on 49 patients with ischemic heart disease. End-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF) were semi-automatically calculated by each program. All patients underwent left ventriculography (LVG) within 3 months before and after the SPECT study. We grouped the patients into 22 with a calculated ESV obtained from LVG of over 50 ml (group A) and 27 with an ESV value of 50 ml or below (group B). We then compared the ESV values from gated SPECT with those from LVG in each group. In group A, the ESV from both Emory and Cedars-Sinai programs similarly correlated well with those from LVG (r = 0.92 and r = 0.93, respectively), but in group B, the ESV calculated from the Cedars-Sinai program correlated less with those from LVG (r = 0.53) than those from the Emory program did (r = 0.70). The calculated LV volumes had more errors in the Cedars-Sinai program than in the Emory program, when a patient had a small heart.     

99mTc-Diethyl-iodo-HIDA (JODIDA): A new hepatobiliary agent in clinical comparison with 99mTc-diisopropyl-HIDA (DISIDA) in jaundiced patients

The new HIDA derivative, ^99mTc-dimethyl-iodine-HIDA (JODIDA), was compared with ^99mTc-diisopropyl-HIDA (DISIDA) in 17 patients with jaundice by means of paired cholescintigraphic imaging studies. The following parameters were visually assessed: the extent of urinary tract visualization, biliary contrast and appearance time, and gallbladder visualization and appearance time. In the 6 patients with a total bilirubin level of between 19 and 66 mol/l (1.1 and 3.9 mg/dl), both radiopharmaceuticals gave similar results except for the moderate visualization of the urinary tract with DISIDA in contrast to JODIDA. In the remaining 11 patients with a total bilirubin level between 102 and 1303 mol/l (6 and 76 mg/dl), JODIDA showed significant advantages over DISIDA: non-visualization of the urinary tract, stronger and faster biliary contrast, and better gallbladder visualization. JODIDA thus offered substantial diagnostic advantages over DISIDA in 8 of these patients. In 4 patients, the differential diagnosis of jaundice (intrahepatic or mechanical disorder) was possible with JODIDA, whereas DISIDA either could not visualize intestinal or gallbladder activity at all or could not differentiate it from the urinary tract. In one patients, JODIDA offered faster (18 h) diagnosis. In the remaining 3 patients, other, substantially false interpretations could be avoided through the use of JODIDA. Further clinical experience with JODIDA in more than 40 patients confirmed the results of this study. We concluded that JODIDA is of significant advantage over DISIDA in clinical situations such as total bilirubin level above 80–100 mol/l (4.7 to 5.8 mg/dl), examination of small children and critically ill patients and suggestion of bile leakage. As there are also no clinical disadvantages, it could become the rediopharmaceutical of choice for hepatobiliary imaging.     

The contraction fraction (CF) in myocardial studies with Technetium-99m-isonitril (MIBI) — correlations with radionuclide ventriculography and infarct size measured by SPECT

Criteria for the detection of coronary artery disease in nuclear cardiology include visualization of perfusion defects and functional impairment of contraction. The purpose of this study is to combine both methods in one procedure with the new myocardial perfusion tracer, ^99mTc-methoxy-isobutyl-isonitril (MIBI), reducing time and radiation burden to the patient. Following an uncomplicated recovery, ten patients with first myocardial infarction participated in this study. Radionuclide ventriculography (RNV) was performed at rest and during exercise. Within 2–3 days, 370 MBq ^99mTc-MIBI were injected and SPECT acquisition commenced 1 h later. Data processing included a scar image in polar coordinates. Areas of significantly reduced tracer uptake were expressed as a percentage of the total myocardial area. Directly following SPECT, resting and maximum exercise gated planar LAO images were recorded and the contraction was quantified. The concept of the contraction fraction (CF) rested on the end systolic change in count distribution: their increase in density and their centripetal concentration. For comparison, geometrical inner edge detection techniques were also applied. All algorithms for describing an EF equivalent were verified by computer simulations, showing a perfect correlation over a wide range of preset EFs. When applied to the patient studies only the non geometric methods revealed a good correlation with the ejection fraction (EF) obtained by RNV, and with the infarct size measured by SPECT. The corresponding correlation coefficients (r), standard errors (SEE) and the regression lines read as follows (in %): CF=0.56×EF+24.8; r=0.87; SEE=4.98; CF=-0.53×SPECT+71.5; r=0.93; SEE=4.19. Thus, estimation of the left ventricular function by the above defined CF is feasible, easy to perform and clinically meaningful. In one procedure with ^99mTc-labelled MIBI not only the perfusion abnormalities were detectable, but also any reduction in function by a valied EF equivalent. Although the monochromatic gamma spectrum of the radionuclide provided better tissue penetrating power, the inner edge of the left ventricle was poorly outlined (especially in the stress studies) and does not lend itself to clinical routine practice.Supported in part by the grant LFS28 from the ministry of science, Stuttgart, Federal Republic of Germany     

The scintigraphic evaluation of myocardial infarction and regional ventricular performance using technetium-99m hexakis (t-butylisonitrile) technetium (I) (TBI): A new myocardial imaging agent

Technetium-99m hexakis (t-butylisonitrile) technetium (I) (^99mTc-TBI) is a new myocardial perfusion imaging agent. To determine its potential in the evaluation of myocardial infarction, 15 patients with suspected or confirmed acute infarction were studied by bedside imaging in the coronary care unit. Good-quality planar scintigrams in multiple projections were obtained in 13 patients. Gated perfusion studies were performed in 14 patients, and for comparison 13 of these were restudied 24–72 h later by standard gated equilibrium blood pool radionuclide ventriculography. Conventional and planar scintigraphic criteria for myocardial infarction (acute or old) agreed in 12 (92%) patients (k=0.81, p<0.05). All the infarctions detected by scintigraphy were associated with electrocardiographic Q-waves. Localization of infarction by the electrocardiogram and scintigraphy exhibited moderate agreement (k=0.49, p<0.1). Regional wall motion analysis by standard radionuclide ventriculography and gated ^99mTc-TBI scintigraphy were in complete agreement for 25 (64%) of 39 left ventricular segments (k=0.35, p<0.05). However, in 7 other segments, associated with areas of infarction, regional wall motion abnormalities were noted only on gated ^99mTc-TBI scintigraphy. Therefore, ^99mTc-TBI scintigraphy can readily provide data on regional myocardial perfusion and wall motion, permitting detection and localization of areas of myocardial infarction. The superior imaging properties, ready availability and low cost of ^99mTc point to the considerable potential value of ^99mTc-TBI in assessing patients with suspected or confirmed myocardial infarction.This work was done during the tenure of a British-American Research Fellowship of the American Heart Association and the British Heart Foundation, with Dr. S. Campbell the recipient     

Usefulness of cerebral blood flow (CBF) measurements to predict the functional outcome for rehabilitation in patients with cerebrovascular disease (CVD)

PURPOSE: The objectives of this study were to (1) elucidate the relationship between the mean CBF in the whole brain (Av.mCBF) before rehabilitation of CVD patients and the BI score before and after rehabilitation, (2) determine whether the efficacy of rehabilitation can be predicted by measurement of the Av.mCBF, and (3) investigate what part of the brain was most important to improving the BI score. MATERIALS AND METHODS: The Av.mCBFs in 160 patients with CVD were calculated by Patlak plots with 99mTc-HMPAO before rehabilitation, and we determined the BI score before and after rehabilitation. Based on the BI scores before and after rehabilitation, patients were divided into four groups: Group A, BI = 100; Group B, 80 < or = BI < or = 99; Group C, 60 < or = BI < or = 79; Group D, 0 < or = BI < or = 59. We evaluated the relationship between the Av.mCBF and BI score before and after rehabilitation. RESULTS: The Av.mCBF before rehabilitation showed a tendency to be more correlated with the BI score after rehabilitation (r = 0.414, p < 0.0001) than before rehabilitation (r = 0.272, p = 0.0006). After rehabilitation, there was a tendency for the Av.mCBF value to increase in direct proportion to the BI score of the group: it was highest in Group A and lowest in Group D. The strongest correlation was found between the frontal lobe regional CBF before rehabilitation and the BI score after rehabilitation (r = 0.343, p < 0.0001). CONCLUSIONS: Measurement of the Av.mCBF before rehabilitation of CVD patients will permit prediction of the efficacy of rehabilitation. Also the regional CBF of the frontal lobe is most important for improving the BI score.     

Use of iodine-123 metaiodobenzylguanidine scintigraphy for the detection of amiodarone induced pulmonary toxicity in a rabbit model: A comparative study with technetium-99m diethyltriaminepenta acetic acid radioaerosol scintigraphy

The purpose of the study was; (i) to determine whether 123I-MIBG scintigraphy is sensitive for detection of amiodarone induced pulmonary toxicity (AIPT) and (ii) to compare it with 99mTc-DTPA radioaerosol. Twelve white New Zealand rabbit with initial mean body weight 4.24 +/- 0.47 g were divided into two groups. AIPT group (n = 7) was administered amiodarone (20 mg/kg BW). The control group (n = 5) received the same amount of 0.9% saline. All animals underwent 123I-MIBG and 99mTc-DTPA radioaerosol scintigraphy at the end of the treatment period. 123I-MIBG static thorax images were obtained during 10 minutes at 15 minutes and 3-hours after intravenous injection of the radiopharmaceutical. Lung to heart ratios (LHR) and lung to mediastinum ratios (LMR), and retention index (LRI) of 123I-MIBG were determined. Two days after 123I-MIBG scintigraphy, 99mTc-DTPA radioaerosol scintigraphy was performed, and clearance from the lungs was measured for 10 min (1 min/frame) following termination of inhalation. 123I-MIBG lung retention index (LRI) was significantly higher in the AIPT group than the control (61 +/- 4.6 vs. 40 +/- 4.5, p = 0.01). Early LHR and LMR were significantly lower in the AIPT group than in the control group (p = 0.04, p = 0.01, respectively), whereas those of late LHR and LMR were not significantly different. T1/2 values of DTPA clearance were significantly increased in AIPT group according to the control group (55 +/- 7.2 vs. 86.6 +/- 18.5, p = 0.02). 123I-MIBG scintigraphy is a valuable tool for detecting AIPT in a rabbit model. Additionally, 99mTc-DTPA radioaerosol scintigraphy is an excellent comprehensive investigational tool for detecting AIPT with the added advantage of lower cost.     

Regional cardiac sympathetic reinnervation in transplanted human hearts detected by123I-MIBG SPECT imaging

The purpose of this study was to assess the regional cardiac sympathetic reinnervation late (> or = 1 year) after heart transplantation (HTX) by means of 123I-MIBG (MIBG) scintigraphy. Eight patients with a pretransplantation diagnosis of idiopathic dilated cardiomyopathy underwent MIBG scintigraphy more than one year after HTX. The presence or absence of regional MIBG uptake was evaluated in each SPECT image, and global MIBG uptake was semi-quantitatively assessed by the heart to mediastinum ratio (H/M). Five of 8 patients had visible MIBG uptake in both planar and SPECT images (PU group), whereas 3 of 8 patients had no uptake, 2 of them after a period of 2 years, and one of them as long as 5 years after HTX, respectively (NU group). Positive regional MIBG uptake involved the basal anterior region in all 5 patients, the basal septal region in 4 patients, the basal lateral region in 3 patients and the basal posterior region in 1 patient. The H/M value was 1.24+/-0.10 in the PU group and 1.09+/-0.03 in the NU group. In conclusion, MIBG SPECT can detect regional sympathetic reinnervation, indicating that basal septal and lateral regions next to the basal anterior are more likely to be reinnervated, but reinnervation is much less likely to occur in the midventricular and apical regions.