National Trends and Outcomes of Acute Myocardial Infarction After Transcatheter Aortic Valve Replacement.

BACKGROUND: Prior studies have reported decreased use of an invasive approach for acute myocardial infarction (AMI) in patients undergoing transcatheter aortic valve replacement (TAVR). OBJECTIVES: The aim of this study was to determine whether prior TAVR affects the use of subsequent coronary revascularization and outcomes of AMI in a contemporary national data set. METHODS: Consecutive TAVR patients from 2016 to 2022 were identified from the U.S. Vizient Clinical Data Base who were hospitalized after the index TAVR hospitalization with ST-segment elevation myocardial infarction (STEMI) or non-ST-segment elevation myocardial infarction (NSTEMI). Patients with STEMI or NSTEMI with or without prior TAVR from the same time period were compared for the use of coronary angiography, revascularization, and in-hospital outcomes. Propensity score matching was used to account for imbalances in patient characteristics. RESULTS: Among 206,229 patients who underwent TAVR, the incidence of STEMI was 25 events per 100,000 person-years of follow-up, and that of NSTEMI was 229 events per 100,000 person-years. After propensity matching, the use of coronary revascularization was similar in the prior TAVR and no TAVR cohorts in both the STEMI (65.3% vs 63.9%; P = 0.81) and NSTEMI (41.4% vs 41.7%; P = 0.88) subgroups. Compared with patients without prior TAVR, in-hospital mortality was higher in the prior TAVR cohort in patients with STEMI (27.1% vs 16.7%; P = 0.03) and lower in those with NSTEMI (5.8% vs 8.2%; P = 0.02). CONCLUSIONS: In this large, national retrospective study, AMI events after TAVR were infrequent. There were no differences in the use of coronary revascularization for STEMI or NSTEMI in TAVR patients compared with the non-TAVR population. In-hospital mortality for STEMI is higher in TAVR patients compared with those without prior TAVR.

The Northern New England Rapid Deployment Valve Experience: Survival and Procedural Outcomes From 2015 to 2021.

OBJECTIVE: The optimal approach and choice of initial aortic valve replacement (AVR) is evolving in the growing era of transcatheter AVR. Further survival and hemodynamic data are needed to compare the emerging role of rapid deployment (rdAVR) versus stented (sAVR) valve options for AVR. METHODS: The Northern New England Cardiovascular Database was queried for patients undergoing either isolated AVR or AVR + coronary artery bypass grafting (CABG) with rdAVR or sAVR aortic valves between 2015 and 2021. Exclusion criteria included endocarditis, mechanical valves, dissection, emergency case status, and prior sternotomy. This resulted in a cohort including 1,616 sAVR and 538 rdAVR cases. After propensity weighting, procedural characteristics, hemodynamic variables, and survival outcomes were examined. RESULTS: The breakdown of the overall cohort (2,154) included 1,164 isolated AVR (222 rdAVR, 942 sAVR) and 990 AVR + CABG (316 rdAVR, 674 sAVR). After inverse propensity weighting, cohorts were well matched, notable only for more patients <50 years in the sAVR group (4.0% vs 1.9%, standardized mean difference [SMD] = -0.12). Cross-clamp (89 vs 64 min, SMD = -0.71) and cardiopulmonary bypass (121 vs 91 min, SMD = -0.68) times were considerably longer for sAVR versus rdAVR. Immediate postreplacement aortic gradient decreased with larger valve size but did not differ significantly between comparable sAVR and rdAVR valve sizes or overall (6.5 vs 6.7 mm Hg, SMD = 0.09). Implanted rdAVR tended to be larger with 51% either size L or XL versus 37.4% of sAVR ≥25 mm. Despite a temporal decrease in pacemaker rate within the rdAVR cohort, the overall pacemaker frequency was less in sAVR versus rdAVR (4.4% vs 7.4%, SMD = 0.12), and significantly higher rates were seen in size L (10.3% vs 3.7%, P < 0.002) and XL (15% vs 5.6%, P < 0.004) rdAVR versus sAVR. No significant difference in major adverse cardiac events (4.6% vs 4.6%, SMD = 0.01), 30-day survival (1.5% vs 2.6%, SMD = 0.08), or long-term survival out to 4 years were seen between sAVR and rdAVR. CONCLUSIONS: Rapid deployment valves offer a safe alternative to sAVR with significantly decreased cross-clamp and cardiopulmonary bypass times. Despite larger implantation sizes, we did not appreciate a comparative difference in immediate postoperative gradients, and although pacemaker rates are improving, they remain higher in rdAVR compared with sAVR. Longer-term hemodynamic and survival follow-up are needed.

Impact of the COVID-19 Pandemic on Infective Endocarditis Management and Outcomes: Analysis of a National Clinical Database.

COVID-19 has widely affected health care delivery, but its impact on the management of infective endocarditis (IE), including valve surgery, is uncertain. We compared the national trends in admissions, demographics, and outcomes of IE before and after COVID-19 onset, using a national sample of IE admissions between 2016 and 2022 from the Vizient Clinical Database. The pre-COVID-19 and post-COVID-19 time periods were separated by the start of the second quarter of 2020, the time during which the COVID-19 pandemic was declared. For all admissions and for admissions involving valve surgery, pre-COVID-19 versus post-COVID-19 baseline characteristics and outcomes were compared using 2-sample t tests or chi-square tests. Propensity score-matched cohorts were similarly compared. Before COVID-19, there were 82,867 overall and 11,337 valve-related surgical admissions, and after COVID-19, there were 45,672 overall and 6,322 valve-related surgical admissions. In the matched analysis for all admissions, the in-hospital mortality increased from 11.4% to 12.4% after COVID-19 onset (p <0.001); in-hospital stroke (4.9% vs 6.0%, p <0.001), myocardial infarction (1.3% vs 1.4%, p = 0.03), and aspiration pneumonia (1.8% vs 2.4%, p <0.001) also increased, whereas other complications remained stable. In the matched analysis of surgical admissions, there was decreased in-hospital mortality (7.7% vs 6.7%, p = 0.03) and intensive care unit stay (8.5 ± 12.5 vs 8.0 ± 12.6 days, p = 0.04); other outcomes remained stable. In conclusion, patients admitted with IE after COVID-19 were more medically complex with worsened outcomes and mortality, whereas patients who underwent valve surgery had stable outcomes and improved mortality despite the pandemic.

Left Ventricular Gene Expression in Heart Failure With Preserved Ejection Fraction-Profibrotic and Proinflammatory Pathways and Genes.

BACKGROUND: Heart failure with preserved ejection fraction (HFpEF) is increasingly prevalent and has few treatments. The molecular mechanisms and resultant signaling pathways that underlie the development of HFpEF are poorly defined. It has been proposed that activation of proinflammatory pathways plays a role in the development of cardiac fibrosis. The signature of gene expression (transcriptome) of previously validated left ventricular biopsies obtained from patients with HFpEF and matched referent controls allows for an unbiased assessment of proinflammatory and profibrotic signaling pathways and genes. METHODS: Epicardial left ventricular biopsies from stringently selected HFpEF patients (HFpEF, n=16) and referent control patients (CTR, n=14) were obtained during aortocoronary bypass surgery. The subepicardial myocardium was flash-frozen to build a repository that was parallel-processed for RNA sequencing to allow for an unsupervised in-depth comparison of the left ventricular transcriptome. RESULTS: The average patient age was 67±10 years. When compared with controls, patients with HFpEF were hypertensive with a higher body mass index (kg/m2: 30±5 versus 37±6; P<0.01) and elevated NT-proBNP levels (pg/mL: 155 [89-328] versus 1554 [888-2178]; P<0.001). The transcriptome analysis revealed differential expression of 477 genes many of which were involved in profibrotic pathways including extracellular matrix production and posttranslational modification but no proinflammatory signature. CONCLUSIONS: The transcriptome analysis of left ventricular myocardial samples from patients with HFpEF confirms an overabundant extracellular matrix gene expression, the basis of myocardial fibrosis, without a signature of activated proinflammatory pathways or genes.

Trends and Predictors of Short Length of Stay Following Transcatheter Aortic Valve Replacement.

BACKGROUND: Minimalist approaches to Transcatheter aortic valve replacement (TAVR) have allowed for improved efficiency in care of patients. We hypothesized that improved efficiencies in care process may have led to increased adoption of a one night length of stay (LOS) in this patient group. OBJECTIVES: The authors aimed to study temporal trends in short length of stay following TAVR. METHODS: This is a nationwide temporal trends study using the 2016-2019 National In Patient Sample (NIS) registry. Short stay was defined as LOS of one night or less. Trends in proportion of patients with short stay were obtained. A multivariate model to identify predictors of short stay was built after adjusting for confounders. Secondary analysis of temporal trends was stratified by presence or absence of major complications (major bleeding requiring transfusion or pacemaker implantation [PPMI]). RESULTS: A total of 217,110 patients were included in the weighted sample. The proportion of patients with short stay significantly increased for those with and without complications (Ptrend < 0.001). The morbidity burden, as defined by the proportion of patients with a Charlson comorbidity index (CCI) score of ≥2 and rate of major complications decreased significantly. On multivariate analysis short stay was predicted by male sex, white ethnicity, Southern/Western regions and lower CCI score. Patients with major bleeding requiring transfusion or PPMI were less likely to have short stay (aOR 0.23 and aOR 0.12, p < 0.001 respectively). CONCLUSION: There is a national trend towards shorter LOS following TAVR. There is a decrease in major post procedural complication rates from 2016 to 2019.

Integrated cardiothoracic surgery match: Trends among applicants compared with other surgical subspecialties.

OBJECTIVE: The objective of this study was to evaluate trends, qualifications, race/ethnicity, and gender of applicants to integrated cardiothoracic (CT I-6) residency programs and compare them with other competitive surgical subspecialties. METHODS: Data were collected from the National Residency Matching Program, Electronic Residency Application Service, and Association of American Medical Colleges for thoracic surgery, orthopedic surgery, neurological surgery, otolaryngology (ENT), plastic surgery, and vascular surgery for 2010 t0 2020. Applicant gender, race/ethnicity, Alpha Omega Alpha (AOA) membership, United States Medical Licensing Examination scores, research productivity, and graduation from a top-40 medical school were analyzed. RESULTS: From 2010 to 2020, CT I-6 experienced growth in postgraduate year 1 positions (280.0%), total applicants (62.2%), and US senior applicants (59.2%). No growth in CT I-6 positions (38) or programs (29) occurred from 2016 to 2020. CT I-6 had the lowest match rates among total applicants (31.7%) and US seniors (41.0%) in 2020. CT I-6 had fewer female applicants compared with ENT (P < .001) and plastic surgery (P < .001), but more than orthopedic surgery (P < .001). Although most CT I-6 US applicants self-identified as White (75.0%), there were more Asian applicants compared with applicants for orthopedic surgery (P < .001), ENT (P < .001), plastic surgery (P < .001), and neurological surgery (P < .01). Matched applicants averaged the highest Step 2-Clinical Knowledge scores (255.1), AOA membership (48.5%), and graduation rates from top-40 medical schools (54.5%). CONCLUSIONS: Despite tremendous growth in positions, CT I-6 has consistently been the most difficult surgical subspecialty to match. CT I-6 has recently attracted an increasingly diverse applicant pool. For the 2019 to 2020 National Residency Matching Program Match Cycle, successful applicants had the highest Step 2-Clinical Knowledge scores, AOA membership rates, and graduation rates from a top-40 medical school among all surgical subspecialties examined.

Assessment of the Early Disabling Effects of Coronary Artery Bypass Graft Surgery Using Direct Measures of Physical Function.

PURPOSE: Coronary artery bypass graft (CABG) surgery is an important treatment option in patients with coronary artery disease. Despite its beneficial effects, CABG surgery and its subsequent hospitalization may reduce physical functional capacity in patients, contributing to physical disability. Our objective was to assess the early disabling effects of CABG surgery and its subsequent hospitalization using direct measurements of physical function. METHODS: Patients (n = 44) were assessed pre-surgery and at hospital discharge for physical function using the Short Physical Performance Battery (SPPB) and self-reported physical and mental health by questionnaire. RESULTS: The total SPPB score (P < .001) and all of its components (P < .01-.001) decreased markedly following CABG surgery and hospitalization, with greater reductions in total SPPB score (P < .05) and gait speed (P < .01) in patients with higher body mass index. While CABG surgery and hospitalization reduced patient-reported physical function, changes in these indices largely did not correlate with changes in SPPB outcomes. CONCLUSION: Our results show the early disabling effects of CABG surgery and hospitalization on directly measured physical function, and that patients with higher body mass index had greater reductions. In addition, our results underscore the need to perform direct measurements of physical function to describe reductions in physiological functional capacity. These findings suggest the need for inpatient rehabilitation or early mobility programs to address this decline in physical function.

Improvement in Physical Function After Coronary Artery Bypass Graft Surgery Using a Novel Rehabilitation Intervention: A RANDOMIZED CONTROLLED TRIAL.

PURPOSE: Cardiorespiratory and skeletal muscle deconditioning occurs following coronary artery bypass graft surgery and hospitalization. Outpatient, phase 2 cardiac rehabilitation (CR) is designed to remediate this deconditioning but typically does not begin until several weeks following hospital discharge. Although an exercise program between discharge and the start of CR could improve functional recovery, implementation of exercise at this time is complicated by postoperative physical limitations and restrictions. Our objective was to assess the utility of neuromuscular electrical stimulation (NMES) as an adjunct to current rehabilitative care following postsurgical discharge and prior to entry into CR on indices of physical function in patients undergoing coronary artery bypass graft surgery. METHODS: Patients were randomized to 4 wk of bilateral, NMES (5 d/wk) to their quadriceps muscles or no intervention (control). Physical function testing was performed at hospital discharge and 4 wk post-discharge using the Short Physical Performance Battery and the 6-min walk tests. Data from 37 patients (19 control/18 NMES) who completed the trial were analyzed. The trial was registered at ClinicalTrials.gov (NCT03892460). RESULTS: Physical function measures improved from discharge to 4 wk post-surgery across our entire cohort (P < .001). Patients randomized to NMES, however, showed greater improvements in 6-min walk test distance and power output compared with controls (P < .01). CONCLUSION: Our results provide evidence supporting the utility of NMES to accelerate recovery of physical function after coronary artery bypass graft surgery.

Long-term seizure, cognitive, and psychiatric outcome following trans-middle temporal gyrus amygdalohippocampectomy and standard temporal lobectomy.

OBJECT: Previous comparisons of standard temporal lobectomy (STL) and selective amygdalohippocampectomy (SelAH) have been limited by inadequate long-term follow-up, variable definitions of favorable outcome, and inadequate consideration of psychiatric comorbidities. METHODS: The authors performed a retrospective analysis of seizure, cognitive, and psychiatric outcomes in a noncontemporaneous cohort of 69 patients with unilateral refractory temporal lobe epilepsy and MRI evidence of mesial temporal sclerosis after either an STL or an SelAH and examined seizure, cognitive, and psychiatric outcomes. RESULTS: The mean duration of follow-up for STL was 9.7 years (range 1-18 years), and for trans-middle temporal gyrus SelAH (mtg-SelAH) it was 6.85 years (range 1-15 years). There was no significant difference in seizure outcome when "favorable" was defined as time to loss of Engel Class I or II status; better seizure outcome was seen in the STL group when "favorable" was defined as time to loss of Engel Class IA status (p=0.034). Further analysis revealed a higher occurrence of seizures solely during attempted medication withdrawal in the mtg-SelAH group than in the STL group (p=0.016). The authors found no significant difference in the effect of surgery type on any cognitive and most psychiatric variables. Standard temporal lobectomy was associated with significantly higher scores on assessment of postsurgical paranoia (p=0.048). CONCLUSIONS: Overall, few differences in seizure, cognitive, and psychiatric outcome were found between STL and mtg-SelAH on long-term follow-up. Longer exposure to medication side effects after mtg-SelAH may adversely affect quality of life but is unlikely to cause additional functional impairment. In patients with high levels of presurgical psychiatric disease, mtg-SelAH may be the preferred surgery type.

Use of a postoperative insulin protocol decreases wound infection in diabetics undergoing lower extremity bypass.

OBJECTIVE: Strict glucose control in patients undergoing coronary bypass grafting has been shown to decrease infectious complications, arrhythmias, and mortality. Our objective was to determine if strict glucose control reduced morbidity after lower extremity bypass (LEB). METHODS: A prospective pilot study at a single institution within the Vascular Study Group of New England was conducted from January 2009 to December 2010. Patients with diabetes and without undergoing LEB were placed on an intravenous (IV) insulin infusion for 3 days after surgery with titration of blood glucose from 80 to 150 mg/dL. The IV insulin study group (n = 104) was compared to a historic control group (n = 189) that received standard insulin treatment from the preceding 3 years. The Fisher exact test, t-tests, Wilcoxon rank-sum tests, χ(2), and logistic regression analyses were used to compare in-hospital morbidity. Stratified analyses were conducted to determine if findings differed based on the presence or absence of diabetes. RESULTS: There was no difference in postoperative complications between the two groups with regard to graft infection, myocardial infarction, dysrhythmia, primary patency at discharge, or mortality. Patients in the IV insulin group had significantly fewer in-hospital wound infections (4% vs 11%; odds ratio [OR], 0.32; 95% confidence interval [CI], 0.11-0.96; P = .047). This association strengthened after adjusting for potentially confounding baseline differences in gender, body mass index, and smoking status (adjusted OR, 0.22; 95% CI, 0.05-0.84; P = .03). When stratified by presence of diabetes, wound infections were decreased in the IV insulin group (0/44 [0%] vs 9/90 [10%]; P = .03). In patients without diabetes treated with IV insulin, there was no significant difference in wound infections (7% vs 12%; P = .42). CONCLUSIONS: Strict glucose control with a postoperative insulin infusion protocol significantly decreased the incidence of postoperative in-hospital wound infection in the diabetic population. These previously unreported findings from this single-institution prospective study warrant further investigation.

Omega-3 fatty acid treatment and T(2) whole brain relaxation times in bipolar disorder.

OBJECTIVE: The authors hypothesized that changes in brain membrane composition resulting from omega-3 fatty acid administration in patients with bipolar disorder would result in greater membrane fluidity, as detected by reductions in T(2) values. METHOD: Women with bipolar disorder (N=12) received omega-3 fatty acids for 4 weeks. A cohort of bipolar subjects (N=9) and a group without bipolar disorder (N=12) did not receive omega-3 fatty acids. T(2) values were acquired at baseline and after 4 weeks. RESULTS: Bipolar subjects who received omega-3 fatty acids had significant decreases in T(2). There was a dose-dependent effect when the bipolar omega-3 fatty acid group was subdivided into high- and low-dose cohorts. CONCLUSIONS: Omega-3 fatty acids lowered T(2) values, consistent with the hypothesis that the fluidity of cell membranes was altered. Further studies are needed to clarify the significance of alterations in brain physiology induced by omega-3 fatty acids, as reflected in T(2) values.

Lithium and valproic acid treatment effects on brain chemistry in bipolar disorder.

BACKGROUND: Prior work reported elevated gray matter (GM) lactate and Glx (glutamate + glutamine + GABA) concentrations in unmedicated patients with bipolar disorder (BP) compared with healthy controls (HC). This study examined whether lithium (Li) and valproic acid (VPA) treatment modulated these chemicals. METHODS: A subset of previously reported BP patients were treated with Li (n = 12, 3.6 +/- 1.9 months) or VPA (n = 9, 1.4 +/- 1.7 months) and compared untreated HC subjects (n = 12, 2.9 +/- 2.4 months) using proton echo-planar spectroscopic imaging. Regression analyses (voxel gray/white composition by chemistry) were performed at each time point, and change scores computed. Metabolite relaxation and regions of interest (ROI) were also examined. RESULTS: Across treatment, Li-treated BP subjects demonstrated GM Glx decreases (Li-HC, p =.08; Li-VPA p =.04) and GM myo-inositol increases (Li-HC p =.07; Li-VPA p =.12). Other measures were not significant. Serum Li levels were positively correlated with Glx decreases at the trend level. CONCLUSIONS: Li treatment of BP was associated with specific GM Glx decreases and myo-inositol increases. Findings are discussed in the context of cellular mechanisms postulated to underlie Li and VPA therapeutic efficacy.

Oral choline decreases brain purine levels in lithium-treated subjects with rapid-cycling bipolar disorder: a double-blind trial using proton and lithium magnetic resonance spectroscopy.

OBJECTIVES: Oral choline administration has been reported to increase brain phosphatidylcholine levels. As phospholipid synthesis for maintaining membrane integrity in mammalian brain cells consumes approximately 10-15% of the total adenosine triphosphate (ATP) pool, an increased availability of brain choline may lead to an increase in ATP consumption. Given reports of genetic studies, which suggest mitochondrial dysfunction, and phosphorus (31P) magnetic resonance spectroscopy (MRS) studies, which report dysfunction in high-energy phosphate metabolism in patients with bipolar disorder, the current study is designed to evaluate the role of oral choline supplementation in modifying high-energy phosphate metabolism in subjects with bipolar disorder. METHODS: Eight lithium-treated patients with DSM-IV bipolar disorder, rapid cycling type were randomly assigned to 50 mg/kg/day of choline bitartrate or placebo for 12 weeks. Brain purine, choline and lithium levels were assessed using 1H- and 7Li-MRS. Patients received four to six MRS scans, at baseline and weeks 2, 3, 5, 8, 10 and 12 of treatment (n = 40 scans). Patients were assessed using the Clinical Global Impression Scale (CGIS), the Young Mania Rating Scale (YRMS) and the Hamilton Depression Rating Scale (HDRS) at each MRS scan. RESULTS: There were no significant differences in change-from-baseline measures of CGIS, YMRS, and HDRS, brain choline/creatine ratios, and brain lithium levels over a 12-week assessment period between the choline and placebo groups or within each group. However, the choline treatment group showed a significant decrease in purine metabolite ratios from baseline (purine/n-acetyl aspartate: coef = -0.08, z = -2.17, df = 22, p = 0.030; purine/choline: coef = -0.12, z = -1.97, df = 22, p = 0.049) compared to the placebo group, controlling for brain lithium level changes. Brain lithium level change was not a significant predictor of purine ratios. CONCLUSIONS: The current study reports that oral choline supplementation resulted in a significant decrease in brain purine levels over a 12-week treatment period in lithium-treated patients with DSM-IV bipolar disorder, rapid-cycling type, which may be related to the anti-manic effects of adjuvant choline. This result is consistent with mitochondrial dysfunction in bipolar disorder inadequately meeting the demand for increased ATP production as exogenous oral choline administration increases membrane phospholipid synthesis.

Multinuclear magnetic resonance spectroscopy of high-energy phosphate metabolites in human brain following oral supplementation of creatine-monohydrate.

Alterations in brain high-energy phosphate metabolism, determined by in vivo magnetic resonance spectroscopy (MRS), have been reported in subjects with a number of brain disorders including major depression, schizophrenia, and substance abuse. It is not clear to what extent these changes can be modified by pharmacological or nutritional means. To address this possibility, we evaluated changes in brain chemistry that were associated with oral creatine (Cr) administration. We hypothesized that oral Cr supplementation, by increasing brain creatine and high-energy phosphate stored in phosphocreatine, would result in an increase in the creatine resonance, as measured using proton 1H-MRS, and a decrease in the beta-nucleoside triphosphate (NTP) peak and an increase in the phosphocreatine (PCr) peak, as measured by phosphorus 31P-MRS, in brain of healthy human subjects. Fifteen healthy male subjects (age=22.9+/-2.2; body mass index=22.9+/-1.7), who were without any axis I disorders or physical or neurological illness, were recruited. Ten subjects took creatine-monohydrate, 0.3 g/kg/day for the first 7 days and 0.03 g/kg/day for the next 7 days (creatine group). Five comparison subjects took equivalent amounts of sucrose as placebo (placebo group). Both 1H- and 31P-MRS scans were acquired at baseline, as well as at day 7 and day 14 of oral supplementation. 1H-MRS: Water suppressed localized spectra were acquired using a single-voxel (1.5 cm x 2 cm x 2 cm) proton MRS PRESS sequence in the left frontal lobe. 31P-MRS: Phosphorus spectral data were recorded from a 5-cm-thick axial brain slice using a short-TE slice selective spin-echo pulse sequence. The creatine group had significantly increased brain creatine levels (8.1% and 9.3%, in creatine/N-acetyl aspartate and creatine/choline ratios, respectively) compared to the placebo group over the 2-week period. The creatine group had significantly decreased beta-NTP levels (7.8%) and marginally increased PCr (3.4%) over the same period. In addition, the brain inorganic phosphate level increased over the same period in the creatine group (9.8%). The current study is the first multinuclear (1H and 31P) MRS study to evaluate changes in brain high-energy phosphate metabolism following oral creatine supplementation in healthy human subjects. These findings suggest the possibility of using oral creatine supplementation to modify brain high-energy phosphate metabolism in subjects with various brain disorders, including major depression, schizophrenia, cocaine and opiate abuse, where alterations in brain high-energy phosphate metabolism have been reported.