[Clinical application of gated SPECT imaging to regional function assessment: current status and limitations]

It is likely that clinical applications of ECG-gated single-photon emission computed tomography (SPECT) are established in nuclear cardiology practice because of the improved diagnostic accuracy of gated SPECT imaging for the detection of coronary artery disease and because this technique enables not only simultaneous assessment of myocardial perfusion and function but also improvement of risk stratification of coronary patients. Although a gated approach with SPECT imaging has been demonstrated to have high reproducibility and reliability for quantifying global function, there are several limitations in appropriate processing of 4-dimensional data for quantitative assessment of regional function. Even if limited spatial and temporal resolutions and a lack of attenuation and scatter corrections are disregarded, sufficient data collection, image-quality control, and precise application of algorithms to gated SPECT data are prerequisite. The results of several kinds of quantitative analysis of regional cardiac function, such as regional wall motion (distance deviation of the inner myocardial border), regional ejection fraction, percent wall thickening, and percent count increase with or without self-normalization have been reported. Further clinical application of quantitative regional function assessment by a gated SPECT technique, however, requires standardization of data acquisition, data analysis, and data presentation with appropriate quantitative parameters; production of a standard map using quantitative values; and validation study by comparison with results of visual analysis and other modalities in a large-scale patient population.

Charcot-Marie-Tooth disease type 2A caused by mutation in a microtubule motor KIF1Bbeta

The kinesin superfamily motor protein KIF1B has been shown to transport mitochondria. Here, we describe an isoform of KIF1B, KIF1Bbeta, that is distinct from KIF1B in its cargo binding domain. KIF1B knockout mice die at birth from apnea due to nervous system defects. Death of knockout neurons in culture can be rescued by expression of the beta isoform. The KIF1B heterozygotes have a defect in transporting synaptic vesicle precursors and suffer from progressive muscle weakness similar to human neuropathies. Charcot-Marie-Tooth disease type 2A was previously mapped to an interval containing KIF1B. We show that CMT2A patients contain a loss-of-function mutation in the motor domain of the KIF1B gene. This is clear indication that defects in axonal transport due to a mutated motor protein can underlie human peripheral neuropathy.

Studies on the prevalence of complicated atrial arrhythmias, flutter, and fibrillation in patients with reciprocating supraventricular tachycardia before and after successful catheter ablation

Atrial flutter and AF are complications in approximately 30% of cases of paroxysmal supraventricular tachycardia (PSVT)-indicated catheter ablation, and it is of interest to determine if therapeutic modification for PSVT would eliminate combined atrial tachyarrhythmia like atrial flutter and AF. The aim of this study was to determine the incidence and the risk of atrial tachyarrhythmias after catheter ablation of PSVT. A total of 152 patients (age range 12-74, mean 41 +/- 17 years) with accessory pathway (n = 106) and/or dual atrioventricular nodal conduction (n = 46) were enrolled in a 2-year follow-up program after successful catheter ablation. Possible risks on clinical background (age, sex, PSVT duration, hemodynamic instability during attacks), premature atrial contraction (PACs) on Holter monitoring, echocardiographic left atrial size, and electrophysiological property (insertion site, conduction type, effective refractory period) were evaluated. Atrial flutter and AF were complications in 53 (35%) of the subjects, who were elderly and had a longer PSVT history with a larger left atrial dimension and frequent PACs; however, the electrophysiological properties were similar. After a 2-year follow-up period 36 (24%) of the patients still exhibited PAC runs, including 13 (9%) with atrial flutter and AF, each one of whom were complicated with nonlethal cerebral thromboembolism and congestive heart failure. Multiplelogistic-regression analysis revealed that advanced age (> or = 41 years, P = 0.0152) and frequent PACs (> or = 1% of total daily QRS counts, P = 0.0426) on Holter monitoring are the risk factors of PAC runs and/or atrial flutter and AF. In conclusion, successful ablation for PSVT is thought to be beneficial for preventing atrial flutter and AF. However, careful follow-up to monitor for the recurrence and atrial flutter and AF related complications, especially in patients of solitary atrial flutter and AF without reciprocating tachycardia and with frequent PAC.

Technetium-99m sestamibi/tetrofosmin myocardial perfusion scanning in cardiac and noncardiac sarcoidosis

Left ventricular (LV) and right ventricular (RV) involvement in sarcoidosis must be firmly confirmed to determine patients' prognosis. We examined whether myocardial perfusion images using technetium-99m single photon emission computed tomography (SPECT) have a diagnostic benefit in the evaluation of biventricular involvement. Sixteen patients with sarcoidosis, aged 21-78 (54 +/- 12) years old, 5 males and 11 females, complicated with cardiac disease (cardiac sarcoidosis, n = 6) including tachyarrhythmias of ventricular origin (n = 5), atrioventricular block (n = 4), and congestive heart failure (NYHA > or = II, n = 1), were enrolled in this study. Myocardial SPECT using technetium-99m sestamibi or tetrofosmin was performed and semiquantitatively scored for comparison with 25 control subjects. Perfusion abnormalities were more frequently recognized in sarcoidosis (LV 5/16, 31% and RV 14/16, 88% vs. LV 0/25, 0% and RV 8/25, 32% in controls). LV involvement had a close correlation with atrioventricular block and with congestive heart failure, and multiple sites of RV involvement correlated with ventricular tachyarrhythmia of RV origin. Total number of defect segments were highest in cardiac sarcoidosis (18/30, 60% vs. 19/60, 32% in noncardiac sarcoidosis, and 11/150, 7% in controls, p = 0.0001), and semiquantitatively evaluated total LV and RV scores (ranging from 0 to 18) were higher than those of controls (15.1 +/- 1.8 vs. 11.4 +/- 3.0 in noncardiac sarcoidosis, and 9.0 +/- 5.0 in cardiac sarcoidosis) and exhibited a significant positive linear correlation with the RV ejection fraction (y = 19.8 + 1.83x, r = 0.786, p = 0.001). Biventricular SPECT using technetium-99m is clinically useful for the noninvasive evaluation of both ventricular involvements in sarcoidosis.

Effects of a phosphodiesterase III inhibitor on circulating blood volume after cardiopulmonary bypass

Using a new method based on pulse dye densitometry, circulating blood volume (BV) was measured without direct sampling in patients undergoing open-heart surgery, and the effects of phosphodiesterase (PDE) III inhibitor administration during cardiopulmonary bypass (CPB) were evaluated. Sixteen patients scheduled for elective coronary artery bypass grafting were randomly assigned to the PDE III inhibitor group or control group. BV was determined before CPB, and immediately, and 4 and 12h after operation. After declamping of the aorta, the PDE III inhibitor amrinone (1 mg/kg) was infused as a single bolus into the venous reservoir in the PDE III inhibitor group. BV decreased significantly soon after the operation in the control group. It did not decrease in the PDE III inhibitor group (48.6 +/- 44 and 60.6 +/- 8.0 ml/kg for the control and PDE III inhibitor groups. respectively). Four hours after surgery and beyond no significant changes in BV were observed in either group. The body fluid balance was negative in both groups. In conclusion, a single administration of PDE III inhibitor during CPB was found to sustain BV soon after operation and, therefore, is useful for postoperative management of open-heart surgery.

Defect in human myocardial long-chain fatty acid uptake is caused by FAT/CD36 mutations

Because of the importance of long-chain fatty acids (LCFAs) as a myocardial energy substrate, myocardial LCFA metabolism has been of particular interest for the understanding of cardiac pathophysiology. Recently, by using radiolabeled LCFA analogues, myocardial LCFA metabolism has been clinically evaluated, which revealed a total defect of myocardial LCFA accumulation in a small number of subjects. The mechanism for the cellular LCFA uptake process is still disputable, but recent results suggest that fatty acid translocase (FAT)/CD36 is a transporter in the heart. In the present study, we analyzed mutations and protein expression of the FAT/CD36 gene in 47 patients who showed total lack of the accumulation of a radiolabeled LCFA analogue in the heart. All the patients carried two mutations in the FAT/CD36 gene, and expression of the FAT/CD36 protein was not detected on either platelet or monocyte membranes. Our results showed the link between mutations of the FAT/CD36 gene and a defect in the accumulation of LCFAs in the human heart.

Effect of coronary artery bypass grafting on native coronary artery stenosis. Comparison of internal thoracic artery and saphenous vein grafts

BACKGROUND

The purpose of this study was to investigate the influence of coronary artery bypass grafting on the degree of stenosis of the native coronary artery.

METHODS

EXPERIMENTAL DESIGN

retrospective data analysis.

SETTING

University hospital.

PATIENTS

consecutive patients undergoing coronary artery bypass grafting (n=52). Bypasses using internal thoracic artery grafts (n=26) and saphenous vein grafts (n=37) to incompletely occluded coronary arteries were studied.

INTERVENTIONS

coronary artery bypass grafting using internal thoracic artery or saphenous vein grafts.

MEASURES

stenosis of the native coronary artery on angiography.

RESULTS

Three recipient coronary arteries bypassed with internal thoracic artery grafts (12%) and 14 recipient coronary arteries bypassed with saphenous vein grafts (38%) showed progression of narrowing (p=0.024). Two recipient coronary arteries bypassed with internal thoracic artery grafts (8%) and 13 recipient coronary arteries bypassed with saphenous vein grafts (35%) showed total occlusion (p=0.016). Hypertension, hyperlipidemia, diabetes mellitus, and smoking history did not correlate with progression of stenosis of the native coronary arteries. Graft flow measured during surgery in the saphenous vein grafts was not significantly different between the group that exhibited progression of the native stenosis and the group that did not.

CONCLUSIONS

Coronary artery bypass grafting with saphenous vein grafts may result in progression of stenosis of the recipient coronary artery. This is less likely after coronary artery bypass grafting with internal thoracic artery grafts. This difference may be due to the ability of the pedicled internal thoracic artery graft to regulate flow. Thus competitive flow in the native coronary artery is minimized. This has significant clinical implications.

[Usefulness of right ventricular Doppler index for predicting outcome in patients with dilated cardiomyopathy]

OBJECTIVES

Left ventricular Doppler index (LVDI) is believed to be a useful echocardiographic index of systolic and diastolic ventricular function. However, the usefulness of right ventricular Doppler index (RVDI) remains uncertain, especially in dilated cardiomyopathy. The predictive value of RVDI for estimating long-term cardiac events, including cardiac death, was investigated.

METHODS

Fifty-nine consecutive patients with dilated cardiomyopathy (41 males and 18 females, mean age 52 +/- 15 years) were enrolled in this follow-up study. RVDI and LVDI were calculated as follows: DI = (isovolumic contraction time + isovolumic relaxation time)/ejection time.

RESULTS

During a follow-up period of 3.7 +/- 3.0 years, 27 (46%) of the patients exhibited cardiac events, including cardiac death (n = 9), heart failure (n = 16) and tachyarrhythmias (n = 2) requiring in-hospital treatment. Patients with these cardiac events had higher LVDI and RVDI at the initial follow-up examination, and RVDI had a significant linear correlation with LVDI (LVDI = 0.550 + 0.452 x RVDI, r = 0.530, p = 0.0001). The 6-year survival rate was significantly lower in patients with both LVDI > or = 0.78 and RVDI > or = 0.49 than in other patients (50% vs 75%, respectively, p = 0.009). Cox proportional hazards model analysis showed that RVDI > or = 0.49 was the independent predictor of cardiac events (p = 0.0153) and cardiac death (p = 0.0003).

CONCLUSIONS

RVDI is clinically useful for estimating the outcome of patients with dilated cardiomyopathy.

Cardiac surgery in patients with end-stage renal disease. Utility of continuous ambulatory peritoneal dialysis

OBJECTIVES

The number of patients with end-stage renal disease undergoing open heart surgery continues to grow. We evaluated continuous ambulatory peritoneal dialysis and the extracorporeal ultrafiltration method during cardiopulmonary bypass in the management of these difficult patients.

METHODS

These 2 methods were used in 4 patients with renal failure who underwent open heart surgery between July 1997 and March 1999. Preoperative continuous ambulatory peritoneal dialysis was conducted using standard protocols. Extracorporeal ultrafiltration method was used only during cardiopulmonary bypass. Continuous ambulatory peritoneal dialysis was initiated upon arrival at the intensive care unit. Mean follow-up was 12 months.

RESULTS

Postoperative blood urea nitrogen and creatinine concentrations were lower than preoperative concentrations. No patients required hemodialysis. All 4 patients were discharged to their homes. No deaths occurred.

CONCLUSIONS

Continuous ambulatory peritoneal dialysis and extracorporeal ultrafiltration method are combined to treat patients with end-stage renal disease who require open heart surgery. This combination is simple, and does not require specialized personnel, and obviates the hemodynamic instability associated with hemodialysis.

CD2- CD4+ CD56+ hematodermic/hematolymphoid malignancy

BACKGROUND

CD2- CD4+ CD56+ lymphoid malignancy has been only rarely reported the last 5 years. It is characterized by a high incidence of cutaneous involvement, cytologically agranular cells, aggressive clinical course, and negative Epstein-Barr virus (EBV) involvement.

OBSERVATION

We describe a Japanese patient with a unique hematolymphoid malignancy characterized by an involvement of skin, nasopharyngeal region, bone marrow, lymph node, and a CD4+ CD43+ CD56+ CD2- CD3- CD8- and terminal deoxynucleotidyl transferase phenotype. Clinically, the cutaneous eruptions were purplish, hard, multiple nodules. Histologically, a massive proliferation of atypical pleomorphic cells with medium-sized nuclei were observed throughout the dermis. No clonal rearrangement of T-cell receptor (TCR)-beta gene or immunoglobulin heavy chain J gene was found, and no positive identification of EBV by in situ hybridization for EBV-encoded small nuclear RNA was found. The patient underwent high-dose chemotherapy with autografting of peripheral blood stem cells; however, the tumors quickly relapsed.

CONCLUSION

We gathered data from 17 cases of lymphoid malignancy from the literature sharing immunophenotypic and genotypic features similar to those of our case, including CD2- CD4+ CD56+ and germline rearrangement of TCR. Although the cellular origin could not be decided, this malignancy was found to have 100% affinity for skin, a short course, and poor prognosis.

Role of the central nervous system in the development of hypertension produced by chronic nitric oxide blockade in rats

We examined the role of the central nervous system, and particularly the renin-angiotensin (RA) system, in the development of hypertension produced by chronic inhibition of NO synthesis. In experiment 1, Wistar rats drank either nitro-L-arginine-methyl ester (L-NAME) or tap water. Before L-NAME treatment rats were divided into 6 groups. Four of them were administered either losartan or artificial cerebroventricular fluid (a-CSF) intracerebroventricularly (i.c.v.) for 1 week using an osmotic mini pump. The other two groups were administered the same amount of losartan intravenously (i.v.). In experiment 2, cardiovascular responses to acute i.c.v. losartan and muscimol, a GABA(A) agonist, were examined in conscious L-NAME-treated rats. Finally, in experiment 3, effects of ablation of the AV3V (anteroventral third ventricle) area, known to be one of the centers of cardiovascular control, were tested in the development of L-NAME hypertension. The development of hypertension by L-NAME treatment was attenuated with chronic i.c.v. losartan in a dose-dependent manner, while i.v. losartan had no effect. One week after cessation of i.c.v. losartan, blood pressure was elevated to the same level as in a-CSF-infused, L-NAME-treated rats. Acute i.c.v. losartan produced no cardiovascular changes in either L-NAME-treated or control rats. On the other hand, although i.c.v. muscimol elicited depressor effects in both groups, these responses were significantly larger in L-NAME-treated rats. Cardiovascular responses to i.v. hexamethonium were similar in both groups. The existence of prior lesions in the AV3V area significantly attenuated the development of L-NAME-induced hypertension. These results indicate that the central RA system plays an important role in the development of hypertension produced by chronic inhibition of NO synthase. Moreover, disorder of the central GABA system, rather than that of the RA system, might be important in the maintenance of hypertension in this model.

Impaired exercise-related myocardial uptake of technetium-99m-tetrofosmin in relation to coronary narrowing and diabetic state: assessment with quantitative single photon emission computed tomography

Despite the diagnostic efficacy of stress myocardial perfusion imaging, the correlation between the actual perfusion tracer activity and diseased state of a coronary artery has not been studied in detail. We estimated exercise-related perfusion augmentation in relation to disease states of a coronary artery in diabetic and non-diabetic patients by a newly developed quantitative technetium (Tc)-99m-tetrofosmin myocardial imaging technique. Tc-99m-tetrofosmin tomographic imaging with an exercise-rest protocol was performed in 26 stable coronary patients and in 8 age-matched controls. Percent increase (%IR) in myocardial count during symptom-limited submaximal exercise-stress was calculated in 16 non-infarcted polar map segments and in each coronary territory by a subtraction technique with corrections for physical decay and injected tracer doses, and the results were compared with those of angiographically quantified coronary diameter stenosis (%DS). Percent IR and peak heart rate during exercise showed a positive linear correlation both in coronary territories with significant stenosis (%DS > or = 75%) and in control or nonstenotic (%DS < 75%) territories. The regression line in stenotic regions was, however. significantly (p < 0.01) shifted downward compared to that in non-stenotic regions. Percent IR in stenotic regions showed a significant inverse correlation with %DS. Coronary stenosis of 75% or more was identified by a %IR cutoff value of 40% with 77% sensitivity, 70% specificity, and an accuracy of 72%. In coronary territories with a %DS of less than 75%, %IR in diabetic patients was significantly lower (46+/-15%) than that in nondiabetic patients (61+/-25%). Thus, blunted exercise-related augmentation of myocardial uptake of Tc-99m-tetrofosmin correlates with the severity of coronary narrowing and diabetic state.

Right ventricular abnormalities assessed by myocardial single-photon emission computed tomography using technetium-99m sestamibi/tetrofosmin in right ventricle-originated ventricular tachyarrhythmias

OBJECTIVES

We sought to determine whether right ventricular (RV) perfusion imaging with technetium-99m (Tc-99m) sestamibi or tetrofosmin single-photon emission computed tomography has diagnostic benefit for RV-originated ventricular tachyarrhythmias (RVT).

BACKGROUND

Identification of RV abnormalities is clinically important to establish RVT etiology.

METHODS

Forty-seven patients with RVT (23 with idiopathic and 24 with organic RVT due to arrhythmogenic RV or dilated cardiomyopathy, cardiac sarcoidosis or myocarditis) were compared to 25 control subjects. Right ventricular uptake score, as assessed by modified tomographic imaging, and regional RV count relative to peak left ventricular (LV) count (RV/LV count ratio) were compared with RV regional and global function.

RESULTS

Regional RV uptake score correlated well with the RV/LV count ratio, and segmental abnormality was more frequently (p = 0.001) detected in the organic RVT group (22 [92%] of 24 patients) than in the idiopathic RVT group (4 [17%] of 23 patients) or the control group (8 [32%] of 25 patients). The total RV score (8.4+/-3.8) in the organic RVT group was significantly lower than that in the idiopathic RVT group (15.6+/-1.6) or the control group (15.1+/-1.8). The total RV score correlated with RV EF (r = 0.702, p<0.001). A total RV score <12 differentiated the organic RVT group from the other two groups, with a sensitivity of 79% and a specificity of 100%. The asynergic RV regions had a significantly lower RV/LV count ratio and RV score as compared with the nonasynergic regions and were identified by RV assessment, with a sensitivity of 76.1% and a specificity of 76.6%.

CONCLUSIONS

Right ventricular perfusion tomography using a Tc-99m-labeled tracer is clinically useful for the noninvasive detection of RV myocardial damage in patients with RVT and for differentiating organic from idiopathic RVT.

Expression of a system L neutral amino acid transporter at the blood-brain barrier

Amino acid transport system L has been proposed to be one of the major nutrient transport systems at the blood-brain barrier. Using immunohistochemical analyses, a system L transporter LAT1 was shown to be expressed in the brain capillary endothelial cells in rats. Because LAT1 was coexpressed with 4F2 heavy chain which brings LAT1 to the plasma membrane, LAT1 is proposed to be functional in the plasma membrane of brain capillary endothelial cells. Both LAT1 and 4F2hc immunoreactivities were detected in a double line appearance surrounding endothelial cell nuclei, suggesting both proteins are present in the luminal and abluminal membranes. LAT1 is, thus, a blood-brain barrier system L transporter responsible for the permeation of aromatic or branched-chain amino acids and amino acid-related drugs such as L-DOPA.

The C-terminal tail domain of neurofilament protein-H (NF-H) forms the crossbridges and regulates neurofilament bundle formation

In order to study the role of NF-H in a neurofilament network formation in neurons, we coexpressed NF-H with neurofilament protein-L (NF-L) in Sf9 cells using the baculovirus expression system. Electron microscopy observations revealed that parallel arrays of 10 nm filaments with frequent crossbridges between adjacent filaments were formed in the cytoplasm of Sf9 cells infected with the recombinant virus that co-expressed NF-L and NF-H. To explore the function of the C-terminal tail domain of NF-H, various deletion mutants lacking portions of the tail domain were constructed, and each of them was coexpressed with NF-L. The results show that the tail domain of NF-H is a structural component of crossbridges and is involved in parallel bundle formation of neurofilaments, as core filaments of the axon. The last 191 amino acids of the C-terminal tail domain of NF-H play a key role in crossbridge formation.

Studies on hemodynamic instability in paroxysmal supraventricular tachycardia: noninvasive evaluations by head-up tilt testing and power spectrum analysis on electrocardiographic RR variation

Hemodynamic instability is a crucial determinant of the best therapeutic option in paroxysmal supraventricular tachycardia (PSVT). However, it is still unclear if hemodynamic instability is tachycardia dependent or independent. We performed frequency-domain analysis of electrocardiographic RR variations during induced PSVT and head-up tilt tests after successful ablation to investigate the role of autonomic vasomotor function in hemodynamic instability during PSVT. Thirty-six patients with (syncope group, n = 18) and without (nonsyncope group, n = 18) syncope and/or presyncope during PSVT were enrolled in this study. Serial blood pressure, heart rate, and variations in heart rate during induced PSVT and head-up tilt tests were examined. Initial blood pressure fall and heart rate changes during induced PSVT were greater in the syncope group than in the nonsyncope group. A significant positive linear relationship was found between these two. Delayed blood pressure fall was observed in the syncope group, independent of heart rate changes. Syncope in PSVT could be predicted from the results of head-up tilt tests with 82% accuracy. Heart rate responses after isoproterenol infusion were significantly greater in the syncope group than in the nonsyncope group. The changes in low frequency to high frequency (LF:HF) values during induced PSVT and head-up tilt tests were significantly greater in the syncope group than in the nonsyncope group, and an exponential correlation was found between LF:HF changes in both tests. We conclude that PSVT rate and vasomotor reaction are related with hemodynamic instability during PSVT and head-up tilt testing is a useful method for determining if patients will have syncope during PSVT.

Does primary stenting preserve cardiac function in myocardial infarction? A case-control study. NORTH-981 investigators. Network of revascularisation therapy in Hokkaido

OBJECTIVE

To investigate whether coronary stenting limits myocardial injury and preserves left ventricular function.

DESIGN AND SETTING

Prospective multicentre case-control study of primary percutaneous transluminal coronary angioplasty (PTCA) with and without stenting, performed in seven cardiovascular centres.

SUBJECTS AND METHODS

45 consecutive patients with acute myocardial infarction who were treated with successful primary stenting (Stent group) and did not have restenosis were paired with 45 matched control subjects with acute myocardial infarction treated by successful primary PTCA without stenting, also with no restenosis (POBA group).

RESULTS

In comparison with the POBA group, the Stent group-especially those patients with a left anterior descending coronary artery lesion-had a smaller hypokinesis area (mean (SD): 15. 1 (20.0) v 34.4 (24.3) chords), reduced hypokinesis area/risk area (25.2 (31.9)% v 58.8 (40.1)%), and a larger ejection fraction (63.3 (10.2)% v 51.7 (11.7)%) evaluated by quantitative left ventriculography using the centerline method. In the Stent group, the correlation between risk area and hypokinesis area was significantly shifted downward. Multiple logistic regression analysis on infarct size limitation (hypokinesis area/risk area < 50%) identified preinfarction angina in all subjects and preinfarction angina and stenting in patients with left anterior descending coronary artery lesions as explanatory factors.

CONCLUSIONS

Primary PTCA using a coronary stent is effective in preventing myocardial injury and restoring left ventricular function in patients with anterior acute myocardial infarction.

Two- and three-dimensional assessments of myocardial perfusion and function by using technetium-99m sestamibi gated SPECT with a combination of count- and image-based techniques

BACKGROUND

Although the myocardial gated single photon emission computed tomography (SPECT) technique makes it possible to assess concurrent myocardial perfusion and function, quantitative methods for analyzing and displaying gated SPECT data in 2- and 3-dimensional presentations for regional and global cardiac assessment have not been established.

METHODS AND RESULTS

We have developed an automated quantitative method for assessing perfusion and function by means of technetium-99m sestamibi gated SPECT with a computerized technique combining count-based and image-based methods. We have examined its validity in 91 patients by comparing its results with those of conventional techniques: contrast left ventriculography and radionuclide angiocardiography. In addition to color-scale displays of regional function, simultaneous 3-dimensional presentations of regional wall motion and perfusion have been produced. High reproducibility of gated SPECT analysis with this algorithm was demonstrated; interoperator errors (%CV) were 2.6% to 5.5%, and good intraobserver reproducibility was confirmed by means of high correlation coefficients (0.954 to 0.989). Left ventricular volumes assessed by means of contrast left ventriculography and by means of the gated SPECT technique showed significant correlations (left ventricular end-diastolic volume, y = 1.01x - 9.7, r = 0.845, P<.001, standard errors of the estimate [SEE] = 14 mL; left ventricular end-systolic volume, y = 1.03x - 1.4, r = 0.902, P<.001, SEE = 6 mL). Left ventricular ejection fraction determined by means of gated SPECT with the new algorithm closely correlated with that determined by means of radionuclide ventriculography (y = 1.05x - 0.6, r = 0.891, P<.001, SEE = 3 %). These parameters quantified by means of the present method correlated closely with those derived from the QGS program (r = 0.926 to 0.987).

CONCLUSION

In comparison with conventional techniques, myocardial gated SPECT with automated quantitative analysis provides accurate and reproducible data for global and regional function. Quantitative concurrent assessment of myocardial perfusion and function by using 2-and 3-dimensional representations appears to be superior to other modalities and to contribute to nuclear cardiology practice.

Covalent bonds in AlMnSi icosahedral quasicrystalline approximant

Electron density distributions were obtained using the maximum entropy method with synchrotron radiation powder data. In the metallic Al12Re, metallic bonding was observed for the icosahedral Al12 cluster with central Re atom. In the nonmetallic alpha-AlMnSi 1/1 approximant, covalent bonds were found in the electron density distribution of the Mackay icosahedral cluster without central atom. Rather than the Hume-Rothery mechanism, the covalency of Al (Si) icosahedron and that between Al (Si) and Mn atoms is considered to be the origin of the pseudogap and nonmetallic behavior of alpha-AlMnSi.

Prognostic value of impaired myocardial fatty acid uptake in patients with acute myocardial infarction

Impaired cardiac fatty acid uptake, assessed by the radiolabelled fatty acid analogue beta-methyl-p-iodophenyl pentadecanoic acid (I-123-BMIPP), is observed in the myocardium following acute ischaemic events, but the long-term prognostic implication has not been established. This study aimed to determine the prognostic value of cardiac BMIPP uptake in patients with acute myocardial infarction. Following the assessment of thallium-201 and I-123-BMIPP uptake, 101 post-infarct patients were prospectively followed up with primary end points of cardiac death, heart failure and non-fatal infarction. During a mean follow-up of 28 months, three cardiac deaths, three non-fatal infarctions, 23 revascularizations and four recurrences of angina pectoris were observed. Multivariate analysis identified reduced uptake of BMIPP and perfusion, no beta-blocking treatment and greater thallium-BMIPP mismatch (i.e. larger BMIPP defect than thallium defect) as significant predictors for overall cardiac events. Prior myocardial infarction, reduced left ventricular ejection fraction and greater thallium-BMIPP mismatch were selected as independent predictors of harder cardiac events. Female patients, those with greater BMIPP defect or greater thallium-BMIPP mismatch showed worse clinical outcomes. The inclusion of BMIPP data improved the prognostic values of conventional significant predictors. In conclusion, impaired myocardial I-123-BMIPP uptake and perfusion-BMIPP mismatch are related to a high probability of fatal and non-fatal cardiac events, suggesting the aetiological relevance and prognostic value of impaired cardiac fatty acid metabolism in viable, but jeopardized, myocardium following acute myocardial infarction.

Nitric oxide is an excitatory modulator in the rostral ventrolateral medulla in rats

Nitric oxide is a messenger molecule having various functions in the brain. Previous studies have reported conflicting results for the roles of nitric oxide in the rostral ventrolateral medulla, a major center that regulates sympathetic and cardiovascular activities. We hypothesized that in this region, nitric oxide may have a biphasic effect on cardiovascular activity. Microinjection of a low dose (1 nmol) of a nitric oxide donor sodium nitroprusside or a cyclic GMP agonist 8-bromocyclic GMP into this area increased arterial pressure, whereas injection of a nitric oxide synthase inhibitor Nomega-nitro-L-arginine methyl ester or a soluble guanylate cyclase inhibitor methylene blue decreased arterial pressure. Microinjection of a high dose (100 nmol) of sodium nitroprusside decreased arterial pressure and inhibited spontaneous respiration with concomitant production of peroxynitrite, a strong cytotoxic oxidant. Increases in arterial pressure caused by microinjection of L-glutamate were inhibited after preinjection of Nomega-nitro-L-arginine methyl ester or methylene blue. Increases in arterial pressure caused by microinjection of sodium nitroprusside (1 nmol) were inhibited after preinjection of a glutamate receptor antagonist kynurenate. These results suggest that low doses of nitric oxide may increase arterial pressure, whereas high doses of nitric oxide may decrease arterial pressure through cytotoxic effects in the rostral ventrolateral medulla. They also indicate that nitric oxide may stimulate neurons both through activation of the nitric oxide cyclic GMP pathway and through modulation of glutamate receptor stimulation, and therefore, increase arterial pressure in rats.