Tetrahydrobiopterin restores impaired coronary microvascular dysfunction in hypercholesterolaemia

Purpose Tetrahydrobiopterin (BH₄) is an essential co-factor for the synthesis of nitric oxide (NO), and BH₄ deficiency may cause impaired NO synthase (NOS) activity. We studied whether BH₄ deficiency contributes to the coronary microcirculatory dysfunction observed in patients with hypercholesterolaemia.Methods Myocardial blood flow (MBF; ml min^–1 g^–1) was measured at rest, during adenosine-induced (140 g kg^–1 min^–1 over 7 min) hyperaemia (mainly non-endothelium dependent) and immediately after supine bicycle exercise (endothelium-dependent) stress in ten healthy volunteers and in nine hypercholesterolaemic subjects using ¹⁵O-labelled water and positron emission tomography. Measurements were repeated 60 min later, after intravenous infusion of BH₄ (10 mg kg^–1 body weight over 30 min). Adenosine-induced hyperaemic MBF is considered to represent (near) maximal flow. Flow reserve utilisation was calculated as the ratio of exercise-induced to adenosine-induced hyperaemic MBF and expressed as percent to indicate how much of the maximal (adenosine-induced) hyperaemia can be achieved by bicycle stress.Results BH₄ increased exercise-induced hyperaemia in controls (2.96±0.58 vs 3.41±0.73 ml min^–1 g^–1, p<0.05) and hypercholesterolaemic subjects (2.47±0.78 vs 2.70±0.72 ml min^–1 g^–1, p<0.01) but had no influence on MBF at rest or during adenosine-induced hyperaemia in controls (4.52±1.10 vs 4.85±0.45 ml min^–1 g^–1, p=NS) or hypercholesterolaemic subjects (4.86±1.18 vs 4.53±0.93 ml min^–1 g^–1, p=NS). Flow reserve utilisation remained unchanged in controls (70±17% vs 71±19%, p=NS) but increased significantly in hypercholesterolaemic subjects (53±15% vs 66±14%, p<0.05).Conclusion BH₄ restores flow reserve utilisation of the coronary microcirculation in hypercholesterolaemic subjects, suggesting that BH₄ deficiency may contribute to coronary microcirculatory dysfunction in hypercholesterolaemia.The first two authors have contributed equally to the present project.An erratum to this article can be found at     

Clearance of thallium-201 from the peripheral blood: Comparison of immediate and standard thallium-201 reinjection

As several reinjection procedures have shown encouraging results in terms of imaging, we investigated whether the kinetics of thallium-201 would differ between the standard stress-redistribution-reinjection approach and the stress-immediate reinjection approach. In 53 consecutive patients with undiagnosed chest pain, 75 MBq (2 mCi)²⁰¹Tl was injected at maximal exercise. In 26 of these patients (group I), 37 MBq (1 mCi)²⁰¹Tl was reinjected immediately after completing the exercise images (the immediate reinjection procedure) and in 27 patients (group II), 37 MBq (1 mCi)²⁰¹Tl was reinjected after completing 3-h redistribution images (the standard reinjection procedure). Mean peak²⁰¹Tl blood activity after exercise was 17.7±12.5 kBq/ml (4.8±3.4 mCi/ml) for group I versus 16.4±9.2 kBq/ml (4.4±2.5 mCi/ml) for group II (NS). The relative increase in²⁰¹Tl blood activity after reinjection of half the initial dose [37 MBq (1 mCi)] exceeded 50% of the initial peak in both groups. The relative amount of²⁰¹Tl delivered to the myocardium was assessed by the area under the curve after both exercise and reinjection, and was 117%±72% for group I and 112%±73% for group II (NS). Blood clearance of²⁰¹Tl was at least biexponential. Mean early decay constants (₁) after exercise and reinjection were 0.30±0.18 min^–1 and 0.22±0.046 min^–1 respectively for group I (T _1/2 2.3 min and 3.2 min respectively, NS), and 0.30±0.12 min^–1 and 0.24±0.07 min^–1 respectively for group II (T _1/2 2.3 min and 2.9 min respectively, NS). For both procedures no significant differences were found between ₁ after exercise and ₁ after injection. The mean late clearance (₂) from the blood was 0.032±0.056 min^–1 and 0.012±0.012 min^–1 respectively for group I (T _1/2 21.6 min and 57.7 min respectively, NS), and 0.036±0.030 min^–1 and 0.014±0.014 min^–1 respectively for group II (T _1/2 19.3 min and 49.5 min respectively, NS). Also, no significant differences were found between ₂ after exercise for both groups and between ₂ after reinjection for both groups. We conclude that reinjection of 37 MBq (1 mCi)²⁰¹Tl (half the initial dose) results in a relative increase in the initial peak and a relative increase in the amount of²⁰¹Tl delivered to the myocardium of more than 50% for both the standard and the immediate reinjection procedure. The clearance of²⁰¹Tl from the blood was not influenced by exercise or by the time of reinjection. Based on²⁰¹Tl kinetics as measured in the peripheral blood, there is no reason to postpone reinjection until 3–4 h following exercise.     

Facilitated transport of glucose from blood to brain in man and the effect of moderate hypoglycaemia on cerebral glucose utilization

The effect of steady-state moderate hypoglycaemia on human brain homeostasis has been studied with positron emission tomography using [U-¹¹C]-D-glucose as tracer. To rule out any effects of insulin, the plasma insulin concentration was maintained at the same level under normo- and hypoglycaemic conditions. Reduction of blood glucose by 55% increased the glucose clearance through the blood-brain barrier by 50% and reduced brain glucose consumption by 40%. Blood flow was not affected. The results are consistent with facilitated transport of glucose from blood to brain in humans. The maximal transport rate of glucose from blood to brain was found to be 62±19 (mean±SEM) mol hg^–1 min^–1, and the half-saturation constant was found to be 4.1 + 2.3 mM.Offprint requests to: G. Blomqvist     

Iodine-131 treatment and chromosomal damage: in vivo dose-effect relationship

Although it is well known that radiation induces chromosomal aberrations, there is a lack of information on the in vivo dose-effect relationship in patients receiving iodine-131 treatment, and the results of previous studies are controversial. In this study, the sister chromatid exchange (SCE) method was employed to investigate acute and late chromosomal damage (CD) in the peripheral lymphocytes of 15 patients who received various doses of ¹³¹I (259–3,700 MBq), either for thyrotoxicosis (TTX) or for ablation treatment in differentiated thyroid cancer (DTC). The SCE frequencies in cultured peripheral lymphocytes were determined before treatment (to assess basal SCE frequencies), on the 3rd day (to assess acute SCE frequencies) and 6 months later (to assess late SCE frequencies). The basal, acute and late SCE frequencies (mean±SD) were 3.19±0.93, 10.83±1.72 and 5.75±2.06, respectively, in the whole group, and these values differed significantly from each other (P<0.001). In order to perform a quantitative evaluation of the present data and a comparative analysis with the results of previous studies reported in the literature, we defined acute and late effects using a damage ratio (DR) and a recovery ratio (RR), based on the basal, acute and late data for individual patients. No statistically significant difference was found in the DR between DTC and TTX patients (76.4%±11.5% vs 67.6%±9.0%), while the mean RR was higher in TTX patients than in the DTC group (75.2%±24.4% vs 36.8%±13.7%). The DR on the 3rd day was not related to the administered ¹³¹I dose in the whole group, but a negative correlation was found between the ¹³¹I dose and the RR at the 6th month (r=–0.60, P=0.04). The best fit for this relationship was obtained by a linear-quadratic model, as y=104.89x–28.4x²+38.1 (R²=0.51, P=0.04). On the other hand, comparative analysis with the results of previous studies with comparable sampling times revealed that the best fit for the relationships between the administered dose of ¹³¹I and DR and RR were obtained with a linear-quadratic model (Y=D+D²) rather than a linear one. However, there was an interesting difference in comparison with in vitro studies, in that we found the coefficient to have a negative value, suggesting the disappearance of damaged lymphocytes from the peripheral circulation in a dose-dependent manner following ¹³¹I treatment. Further studies are therefore needed to clarify the effect of the negative value on the biological dosimetry approach in continuous internal low LET radiation, as in the case of ¹³¹I treatment.     

MELD Score as a Predictor of Early Death in Patients Undergoing Elective Transjugular Intrahepatic Portosystemic Shunt (TIPS) Procedures

Purpose To Evaluate the MELD score as a predictor of 30-day mortality in patients undergoing elective TIPS procedures.Methods This was a retrospective, IRB-approved study. The medical records of all patients who underwent a TIPS procedure between May 1, 1999 and June 1, 2003 in a single institution were reviewed. Patients who underwent elective TIPS were selected. Elective TIPS was performed in 119 patients with a mean age of 55.1 (± 9.6) years. The MELD and Child-Pugh scores before TIPS, etiology of cirrhosis, portosystemic gradients before and after TIPS, procedure time, and procedural complications were obtained from the medical records. The MELD and Child-Pugh scores before TIPS were compared between the survivor group (SG) and the early death (EDG) group. The early death rate was calculated for MELD score subgroups (1–10, 11–17, 18–24, and >24). Data were analyzed using the Fisher exact test, chi-square test and independent-sample t-test. A p value of less than 0.05 was considered significant.Results Technical success rate was 100%. The early death rate was 10.9% (13/119). The mean MELD scores before TIPS were 19.4 (± 5.9) (EDG) and 14 (± 4.2) (SG) (p=0.025). The early death rate was highest in the pre-TIPS MELD > 24 subgroup. The Child-Pugh scores were 9.0 (± 1.6) (SG) and 9.8±1.06 (EDG) (p=0.08). The mean portosystemic gradients before TIPS were 20.5 (± 7.7) mmHg (EDG) and 22.7 (± 7.3) (SG) (p > 1) and the mean portosystemic gradients after TIPS were 6.5 (± 3.5) (EDG) and 6.9 (± 2.4) (SG) (p > 1). The mean procedural times were 95.6 (± 8.4) min (EDG) and 89.2 (± 7.5) min (SG) (p > 1). No early death was attributed to a fatal complication during TIPS.Conclusion The MELD score is useful in identifying patients at a higher risk of early death after an elective TIPS. On th basis of our results, we do not endorse elective TIPS in patients with MELD scores > 24.     

Dobutamine 99mTc-MIBI single-photon emission tomography: non-exercise-dependent detection of haemodynamically significant coronary artery stenoses

Dobutamine pharmacological stress testing in conjunction with technetium-99m methoxyisobutylisonitrile single-photon emission tomography (MIBI SPET) may be a useful alternative to convential exercise stress MIBI SPET for the detection and localisation of coronary artery stenoses. Therefore, 35 patients with stenoses ( 50% diameter reduction) of one or more coronary arteries were selected for dobutamine MIBI SPET. Each patient underwent MIBI injection at rest and during dobutamine infusion with incremental doses (5, 10, 15 and 20 g kg^–1 min^–1). A conventional exercise stress test (EST) was performed in all patients. Peak double product during steady-state dobutamine infusion (18 200 ± 4200 mmHg min^–1) was lower (P = 0.0001) than during EST (21 700 ± 4900 mmHg min^–1). Image quality was good in all but one patient, who had to be excluded from data analysis due to excessive hepatobiliary MIBI activity. Dobutamine-induced perfusion abnormalities were observed in 30/34 MIBI SPET studies, resulting in an overall detection rate for coronary artery disease of 88%. A pathological EST was observed in 23/34 patients (68%). The detection rate of individual coronary artery stenoses was 85% (28/33) for stenosess with a severe diameter reduction (>70%) and 50% (12/24) for stenoses with a moderate diameter reduction ( 50–70%). In particular, sensitivity and specificity for the detection of moderate and severe stenoses ( 50%) were 75%/100% for left anterior descending, 67%/95% for left circumflex and 67%/69% for right coronary artery stenoses. Dobutamine MIBI SPET is a well-tolerated, non-exercise-dependent test for detection and localisation of haemodynamically significant coronary artery stenoses. The use of dobutamine allows a stepwise increase in pharmacological stress similar to EST and is especially useful in patients who are unable to exercise. Correspondence to: E. Voth     

Relation of coronary vasoreactivity and coronary calcification in asymptomatic subjects with a family history of premature coronary artery disease

Electron-beam computed tomography (EBCT) allows non-invasive imaging of coronary calcification and has been promoted as a screening tool for coronary artery disease (CAD) in asymptomatic high-risk subjects. This study assessed the relation of coronary calcifications to alterations in coronary vascular reactivity by means of positron emission tomography (PET) in asymptomatic subjects with a familial history of premature CAD. Twenty-one subjects (mean age 51±10 years) underwent EBCT imaging for coronary calcifications expressed as the coronary calcium score (CCS according to Agatston) and rest/adenosine-stress nitrogen-13 ammonia PET with quantification of myocardial blood flow (MBF) and coronary flow reserve (CFR). The mean CCS was 237±256 (median 146, range 0–915). The CCS was <100 in eight subjects and >100 units in 13. As defined by age-related thresholds, 15 subjects had an increased CCS (>75th percentile). Overall mean resting and stress MBF and CFR were 71±16 ml 100 g^–1 min^–1, 218±54 ml 100 g^–1 min^–1 and 3.20±0.77, respectively. Three subjects with CCS ranging from 114 to 451 units had an abnormal CFR (<2.5). There was no relation between CCS and resting or stress MBF or CFR (r=0.17, 0.18 and 0.10, respectively). In asymptomatic subjects a pathological CCS was five times more prevalent than an abnormal CFR. The absence of any close relationship between CCS and CFR reflects the fact that quantitative myocardial perfusion imaging with PET characterises the dynamic process of vascular reactivity while EBCT is a measure of more stable calcified lesions in the arterial wall whose presence is closely related to age.     

Genetic polymorphism of desialyzed alpha2 HS-glycoprotein by ultrathin isoelectric focusing

Summary The genetically determined polymorphism of ₂ HS-glycoprotein was analyzed by immunoblotting ultrathin-layer polyacrylamide gel isoelectric focusing in the pH range 4–6.5 and neuraminidase pretreated sera. In a Libyan population sample from Tripoli (n=110) three common phenotypes, ₂ HSG 1–1, 2–1, and 2–2, were observed. The allele frequencies were ₂ HSG¹=0.8364 and ₂ HSG²=0.1636. The theoretical exclusion rate in cases of disputed paternity is 11.8%.     

PET imaging of brain with the β-amyloid probe, [11C]6-OH-BTA-1, in a transgenic mouse model of Alzheimer’s disease

Purpose The purpose of this study was to evaluate the capacity of [¹¹C]6-OH-BTA-1 and positron emission tomography (PET) to quantify -amyloid (A) plaques in the Tg2576 mouse model of Alzheimers disease (AD).Methods PET imaging was performed with the NIH ATLAS small animal scanner in six elderly transgenic mice (Tg2576; age 22.0±1.8 months; 23.6±2.6 g) overexpressing a mutated form of human -amyloid precursor protein (APP) known to result in the production of A plaques, and in six elderly wild-type litter mates (age 21.8±1.6 months; 29.5±4.7 g). Dynamic PET scans were performed for 30 min in each mouse under 1% isoflurane inhalation anesthesia after a bolus injection of 13–46 MBq of [¹¹C]6-OH-BTA-1. PET data were reconstructed with 3D OSEM. On the coronal PET image, irregular regions of interest (ROIs) were placed on frontal cortex (FR), parietal cortex (PA), striatum (ST), thalamus (TH), pons (PO), and cerebellum (CE), guided by a mouse stereotaxic atlas. Time–activity curves (TACs) (expressed as percent injected dose per gram normalized to body weight: % ID-kg/g) were obtained for FR, PA, ST, TH, PO, and CE. ROI-to-CE radioactivity ratios were also calculated. Following PET scans, sections of mouse brain prepared from anesthetized and fixative-perfused mice were stained with thioflavin-S.Results TACs for [¹¹C]6-OH-BTA-1 in all ROIs peaked early (at 30–55 s), with radioactivity washing out quickly thereafter in both transgenic and wild-type mice. Peak uptake in all regions was significantly lower in transgenic mice than in wild-type mice. During the later part of the washout phase (12–30 min), the mean FR/CE and PA/CE ratios were higher in transgenic than in wild-type mice (1.06±0.04 vs 0.98±0.07, p=0.04; 1.06±0.09 vs 0.93±0.08 p=0.02) while ST/CE, TH/CE, and PO/CE ratios were not. Ex vivo staining revealed widespread A plaques in cortex, but not in cerebellum of transgenic mice or in any brain regions of wild-type mice.Conclusion Marked reductions in brain uptake of this radioligand in transgenic mice may be due to reduced cerebral blood flow relative to that in wild-type mice. Specific [¹¹C]6-OH-BTA-1 binding to A plaques, if any, is probably very low, as reflected in the small FR/CE and PA/CE ratio differences. FR/CE and PA/CE ratios are considerably higher in AD patients while A plaque densities in 22-month-old transgenic mice may be expected to show essentially the same density as is observed in the AD brain. This implies that the absence of tracer retention in 22-month-old transgenic mice may be due to the smaller number of A plaque binding sites and/or to lower affinity of the binding sites for [¹¹C]6-OH-BTA-1 as compared with AD patients. [¹¹C]6-OH-BTA-1 shows excellent brain uptake in mice.This work was presented at the 51st Annual Meeting of the Society of Nuclear Medicine in Philadelphia, PA, June 19–23, 2004.     

Differential kinetics of [123I]β-CIT binding to dopamine and serotonin transporters

Iodine-123-labelled 3-(4-iodophenyl)tropane-2-carboxylic acid ([¹²³I]-CIT) labels both the dopamine transporter (DAT) and the serotonin transporter (5-HTT) and this ligand is able to clarify pathological changes in both dopaminergic and serotonergic systems. However, the differential kinetics of -CIT binding to DAT and 5-HTT has not been clarified fully. In this study we examined time-activity curves of [¹²³I]-CIT in individual regions in the rat brain. Using cerebellum as the reference region,k ₃ andk ₄ values were estimated by a two-compartment kinetic analysis. In the striatum, the kinetics was slowest among all brain areas. In this area specific binding reached its peak 4 h after the injection. In the hypothalamus, specific binding reached its peak 1 h after the injection and its amount did not change until 4 h after the injection. In the occipital cortex, the binding and washout of the ligand were fastest among all brain regions. Estimatedk ₃ values were 0.040±0.003 in the striatum, 0.019±0.002 in the hypothalamus and 0.082±0.011 in the occipital cortex (min^–t, mean ±SD). Estimatedk ₄ values were 0.0034±0.0005 in the striatum, 0.0071±0.0009 in the hypothalamus and 0.083±0.013 in the occipital cortex (min^–1, mean ±SD). Therefore binding kinetics of [¹²³I]-CIT in the region rich in DAT is apparently different from that in the region rich in 5-HTT. These results will provide fundamental data to image both DAT and 5-HTT in one series of examinations with [¹²³I]-CIT.     

Imaging of serotonin and dopamine transporters in the living human brain

Alterations in brain serotonin (5-HT) and dopamine (DA) activity are associated with several neuropsychiatric disorders, but until now it has not been possible to simultaneously visualize or quantify the 5-HT and the DA transporter density in the living human brain. In this paper we report on the imaging of 5-HT and DA transporters in 28 healthy controls with single-photon emission tomography using iodine-123 labelled 2-carbomethoxy-3-(4-iodophenyl)tropane ([¹²³I]-CIT) as the tracer. The [¹²³I]-CIT distribution showed the most prominent 5-HT activity in the medial frontal cortex, hypothalamus, midbrain and occipital cortex and the greatest DA activity in the basal ganglia. The specific binding of the 5-HT transporters in the medial frontal cortex was 0.377±0.031 and that of the DA transporters in the basal ganglia, 0.916±0.007. Gjedde-Patlak plots indicated two separate components: the first was assumed to represent 5-HT transporters with a slope of 1.29±0.27 h^–1 and the second, DA transporters with a slope of 0.30±0.04 h^–1. This distinct kinetic pattern and the fact that 5-HT and DA transporters are situated in different parts of the brain provides an opportunity to study in vivo patients suffering from various neuropsychiatric disorders.     

Measurements of the rubidium isotopic activities and the elution parameters of 81mKr generators using a standardized 114mIn source

A method is described for measuring a number of parameters associated with an inorganic ion-exchange krypton generator. These are the activities of rubidium isotopes in inorganic ion-exchange krypton generators, the ^81mKr extraction rate, the ^81mKr activity delivered to patients during ventilation studies, the elution efficiency, and the radionuclide purity of the eluted gas. The method is based on the calibration of detectors, Ge(Li) and NaI(Tl), with a standardized ^114mIn source at matching photon energies. The average activities present in our generators at the end of bombardment (EOB) were 14.6±3.8 mCi (⁸¹Rb), 6.2±1.6 mCi (^82mRb) and 53±9.4 Ci (⁸³Rb). The ^81mKr extraction rate 2 h post-EOB was 10.2±2.3 mCi/min at an air flowrate of 1 l/min. The ^81mKr activity delivered to patients during a ventilation study was 91±16 mCi. The elution efficiency of the generators averaged 50%±7% at an air flowrate of 1 l/min. The eluted gas contained Rb radioisotopic impurities in trace quantities of approximately 0.06 Ci/l.     

Comprehensive model for simultaneous MRI determination of perfusion and permeability using a blood-pool agent in rats rhabdomyosarcoma

To present a new compartmental analysis model developed to simultaneously measure tissue perfusion and capillary permeability in a tumor using MRI and a macromolecular contrast medium. Rhadomyosarcomas were implanted subcutaneously in 20 rats and studied by 1.5-T MRI using a fast gradient echo sequence (2D fast SPGR TR/TE/ 13 ms/1.2 ms/60°) after injection of a macromolecular contrast medium. The left ventricle and tumor signal intensities were converted into concentrations and modeled using compartmental analysis, yielding tumor perfusion F, distribution volume V_distribution, volume transfer constant K^trans, rate constant of influx k_pe, and initial extraction (fraction) E. Tumor perfusion was F=43±29 ml·min^–1·100 g^–1. The permeability study allowed the measurement of k_pe=0.37±0.12 min^–1 and K^trans=0.01±0.0031 min^–1. The blood volume could be assimilated to the distribution volume (V_distribution=2.9±1.01%) since the capillary leakage was small. The simultaneous assessment of perfusion and permeability allowed quantification of the initial extraction (fraction) E=2.34±1.05%. Quantification of both tumor perfusion and capillary leakage is feasible using MRI using a macromolecular blood pool agent. The method should improve tumor characterization.     

The significance of the aminoterminal propeptide of type III procollagen in paroxysmal nocturnal haemoglobinuria and myelofibrosis

The level of the aminoterminal propeptide Col 1–3 of type III procollagen (PC-III) was determined in patients with paroxysmal nocturnal haemoglobinuria (PNH) and primary myelofibrosis (PMF), to study whether PC-III can be used as a parameter for the rate and/or degree of bone marrow replacement with collagen. Normal PC-III levels were found in PNH (6.6±1.1 g/l; N: 8.6±1.8 g/l), while significantly increased levels were found in PMF (24.8±2.2 g/l).During a follow-up of 1 year, a slight increase of 2 g/l occurred in three patients with a stable fibrosis, while one patient with more active disease demonstrated an increase of 25 g/l. Treatment with acetylsalicylic acid led to a decline of PC-III as well as -thromboglobulin level, although normalization did not occur. It was demonstrated by means of gel filtration that the antigens related to the PC-III peptide were heterogenous, and that in PMF at least two main peaks were present, with molecular masses equal to and smaller than PC-III peptide.These data demonstrate that the radioimmunoassay cannot be used for the quantitative determination of PC-III; nevertheless it gives some insight in the process of bone marrow fibrosis.     

Prospective evaluation of two different injection techniques for MR arthrography of the hip

The aim of the study was to evaluate prospectively the technical feasibility and discomfort of two different injection techniques for MR arthrography of the hip. Sixty-one consecutive patients undergoing MR arthrography of the hip (68 hips) were randomly injected either at the femoral head (36 hips) or the femoral neck (32 hips). The patients rated discomfort during and 0–72 h after arthrography using a visual analogue scale (VAS, 0=did not feel anything, 100=unbearable). The volume injected, the distance between the needle tract and the neurovascular bundle, the duration of the procedure and the extra-articular contrast leakage were measured. No significant differences were found for the volume injected, the distance between the needle tract and the neurovascular bundle, or the procedure duration. Volume of extra-articular contrast leakage was statistically significantly different (head 1±2 cm³, neck 3±5 cm³, P=0.024). The VAS score for needle advancement was significantly different (head 25±20, neck 19±23, P=0.031). No significant differences were found for the VAS score regarding delayed discomfort. Before the examination the arthrography-related discomfort was overestimated by 74% (50/68), correctly anticipated by 22% (15/68) and underestimated by 4% (3/68) of the patients. MR-related discomfort was overestimated by 32% (22/68), correctly anticipated by 57% (39/68) and underestimated by 10% (7/68) of the patients. Both hip puncture techniques were well tolerated. The neck injection technique produced less discomfort and was associated with greater extra-articular contrast leakage.     

Survival benefit after revascularization is independent of left ventricular ejection fraction improvement in patients with previous myocardial infarction and viable myocardium

Purpose This study was designed to assess the relationships among myocardial viability, changes in left ventricular (LV) ejection fraction after coronary revascularization and long-term event-free survival in patients with previous myocardial infarction and LV dysfunction. Methods We studied 253 patients with previous myocardial infarction and evidence of dysfunctional viable myocardium as assessed by echocardiography and ^99mTc-sestamibi imaging. Coronary revascularization was performed in 142 patients, while 111 were medically treated. In revascularized patients, echocardiography was repeated 12 months later to detect LV ejection fraction improvement, defined as an increase of 5% compared with baseline. All patients were followed for a mean period of 52±29 months. Cardiac death and non-fatal myocardial infarction were considered as events. Results Event-free survival was higher in revascularized than in medically treated patients (P<0.001). Ejection fraction increased by 5% in 82 (58%) revascularized patients, and the extent of viable myocardium was the strongest predictor of such improvement (P<0.001). Event-free survival was similar for patients with (n=82) and patients without (n=60) LV ejection fraction improvement after revascularization, and it was better in revascularized than in medically treated patients in the presence of either substantial (5 viable segments) or low–intermediate (1–4 viable segments) viability (both P<0.01).Conclusion In patients with previous myocardial infarction and evidence of viable myocardium, coronary revascularization procedures improve outcome at long-term follow-up independently of LV ejection fraction improvement.     

A comparison of dobutamine and maximal exercise as stress for thallium scintigraphy

In the assessment and evaluation of patients with suspected coronary artery disease there is a need for pharmacological stress combined with thallium scintigraphy. Thallium images were obtained following stress both with dobutamine infusion (5–20 g kg^–1 min^–1) and with symptom-limited bicycle ergometry in 20 patients (age 39–70 years) with chest pain who had been admitted for coronary angiography. Percentage thallium uptake was calculated using a region of interest technique. Detailed comparison was performed of the presence, size and distribution of left ventricular thallium perfusion defects; the percentage thallium uptake in ventricles, lung and liver; and the haemodynamic response to stress. Each stress produced a similar number of abnormal segments in each of three views (total EX 166/300; DOB 167/295), but exercise produced larger defects in the anterior view (P<0.025). Thallium uptake in left and right ventricles and relative uptake to lungs were similar, but dobutamine produced higher relative liver uptake [EX 1.55 (0.67); DOB 2.97 (1.23) P<0.0001]. Fourteen patients were able to tolerate dobutamine 20 g kg^–1 min^–1. The ratio of peak stress to rest double product was smaller with dobutamine in both patients with (DOB 1.3; EX 2.0; P<0.0047) and patients without -blockade (DOB 1.5; EX 2.4; P<0.008). Dobutamine produced fewer conventional stress endpoints of chest pain and ST depression. In conclusion, dobutamine produces a well-tolerated incremental pharmacological stress with thallium images similar to maximal exercise, and provides a useful alternative stress in patients unable to perform adequate dynamic exercise.Correspondence to: D.R. Wallbridge     

Further investigations of morpholino pretargeting in mice—establishing quantitative relations in tumor

Purpose This laboratory has previously published on phosphorodiamidate morpholino (MORF) pretargeting of tumor in which an anti-tumor antibody conjugated with MORF (a DNA analogue) is first administered, followed at a later time by the radiolabeled complementary MORF (cMORF) as the effector. In the present study, the pharmacokinetics of the antibody and effector were measured under different conditions in mice to establish their quantitative relationships with tumor accumulations by pretargeting.Methods A cytosine-free 18 mer cMORF was conjugated with MAG₃ for ^99mTc labeling while the anti-CEA antibody MN14 was conjugated with DTPA for ¹¹¹In labeling and with MORF to impart binding affinity for radiolabeled cMORF. Mice bearing LS174T thigh tumors were used to study: (1) the pharmacokinetics of MN14-MORF by administering ¹¹¹In-MN14 at doses between 10 and 100 g with sacrifice at 2 days and at 30 g with sacrifice between 1 and 3 days; (2) the biodistribution of ^99mTc-cMORF following one to four injections (containing 0.15 g each and separated by 1 h) to animals having received 30 g of antibody–MORF 2 days earlier and with sacrifice at 3 h after the final injection; and (3) the influence on the biodistribution of ^99mTc-cMORF of a 2 to 4 day interval between the administration of 30 g of antibody–MORF and 0.30 g of ^99mTc-cMORF.Results (1) The biodistribution of antibody in percent accumulation (%ID or %ID/g) was largely independent of antibody dose but the absolute accumulation of antibody in tumor increased linearly with dose, showing no evidence of tumor saturation of CEA sites by MN14. Over 1–3 days post antibody administration, blood levels of radiolabeled antibody decreased as expected; however, tumor levels remained constant, thus showing an absence of antibody clearance in tumor over this period. (2) With fixed antibody–MORF dose and increasing number of injections of ^99mTc-cMORF, cumulative percent blood levels steadily decreased in agreement with the values calculated based on the antibody–MORF in blood. In contrast, cumulative percent tumor levels stayed fairly constant over the first two injections. Thus the antibody–MORF in tumor became saturated with cMORF more slowly than that in blood owing to delivery differences. (3) As expected, percent blood levels decreased with increasing interval between injections of antibody–MORF and ^99mTc-cMORF. The percent tumor accumulation, however, remained constant over the 3 day interval, thus demonstrating only slow loss of MORF expression in situ. The ^99mTc-cMORF accumulation in tumor after saturation was mathematically determined based on the antibody–MORF concentration in tumor while the blood levels of ^99mTc-cMORF were determined based on the concentration of antibody-MORF in blood.Conclusion Contrary to conclusions arrived at in our earlier study, the results of this study show that tumor CEA sites were not saturated even at the highest antibody dose investigated, that accessibility of MORF sites in tumor by ^99mTc-cMORF was unhindered and that the maximum percent tumor accumulation of ^99mTc-cMORF depended only on the tumor delivery efficiency of ^99mTc-cMORF.     

Quantification of baboon cortical S2 serotonin receptors in vivo with 3-N-(2′-Fl8)fluoroethylspiperone and positron emission tomography

We used the ligand 3-N-(2-F 18)fluoroethylspiperone (FESP) and positron emission tomography (PET) to quantify in vivo serotonin S₂ neuroreceptor density and affinity in the baboon frontal cortex. In the cortex, FESP binds specifically and exclusively to S₂ receptors, and an equilibrium is reached when the rate of ligand-receptor association and dissociation become equal. Using multiple studies in the same baboon, an equilibrium (saturation) analysis approach provided a linear Hill plot with a slope of 1.02 (r ² =0.988,P <0.0001), indicative of ligand binding to a single receptor class. Using serial PET scans, a dynamic approach was also used to quantify S₂ receptors in the frontal cortex of the baboon, which provided an estimate of receptor densityB _max =35.6 ± 10.9 pmol/g. The rate constants corresponding to transport into and out of tissue wereK _* ¹ = 0.2720 ± 0.0299 mol/min g andk _* ² = 0.0786 ± 0.0315 min^–1, respectively. The ligand-receptor dissociation constant wask _* ⁴ = 0.0154 ± 0.0109 min^–1.     

Evaluation of 111In labelled white blood cells by in vitro functional tests and electron microscopy

We have studied the influence of granulocyte labelling with commercially available ¹¹¹In-oxine, tropolone (trop) or home made ¹¹¹In-Mercapto pyridine (Merc) prepared by the method of Thakur (1985) on the cell structure by electron microscopy and on the cell function by enzymatic tests, random migration, chemotaxis, phagocytosis and bactericidal activity. The granulocytes were labelled with 400 Ci ¹¹¹In-oxine in saline or ¹¹¹In-trop or Merc in plasma. The effect of the chelating agents with and without addition of the tracer was studied (n=4) with varying concentrations: 5–10 g/ml oxine, 10–160 g/ml trop and 1–4 g/ml Merc. Chemotaxis and random migration were not affected by ¹¹¹In-trop and clearly supressed by ¹¹¹In-oxine and Merc; the other tests were normal. The cell structure was disturbed by Merc. The labelling efficiency was excellent with oxine (90%), acceptable with trop (30%–80%) and poor with Merc (10%–25%). Without ¹¹¹In, chemotaxis and random migration were normal up to a concentration of 80 g/ml trop, 8.5 g/ml oxine and 1 g/ml Merc. With addition of ¹¹¹In, chemotaxis and random migration were unaffected up to 80 gmg/ml by trop and markedly supressed by Merc and oxine. It is concluded that labelling with ¹¹¹In-trop assures intact cells.