Biomedical subjects

Daniel Bernstein

Publications and source records attributed to Daniel Bernstein.

27 records · Page 2Linked to original sources

PubMed2004

Genome-wide expression profiling of a cardiac pressure overload model identifies major metabolic and signaling pathway responses.

Cardiac hypertrophy is a predictor of cardiovascular morbidity and mortality independent of other risk factors. Pressure overload induces the development of left ventricular hypertrophy (LVH) and left atrial enlargement (LAE) in the mammalian heart. To systematically investigate the transcriptional changes, which mediate these processes, we have performed a genome-wide transcriptional profiling of each of the four heart chambers from mice subjected to transverse aortic constriction (TAC). A major new finding of this analysis is that during enlargement the left atrium undergoes radical changes in gene transcription that may play a significant role in pathophysiology. Structural changes in the LA and LV are correlated with significant changes in the transcriptional profile of these chambers, with thousands of differentially expressed known and novel factors. Statistical analysis of the results identified Gene Ontology biological process groups with significant group-wide changes, including angiogenesis, energy pathways, fatty acid oxidation, oxidative phosphorylation, cytoskeletal and matrix reorganization, and G-protein coupled receptor (GPCR) signaling. To facilitate future research, a searchable annotated Internet database has been constructed that allows access to the expression data presented here. Further study of these genes and processes will lead to better understanding of pathways involved in the pathophysiology of the cardiac response to pressure overload.

Animals↗

PubMed2004

Risk factors for recurrent rejection in pediatric heart transplantation: a multicenter experience.

BACKGROUND: Cardiac allograft rejection remains as a primary cause of death in the first 3 years after pediatric heart transplantation. Multiple episode of acute rejection in adult heart transplant recipients may accelerate the development of graft vasculopathy. We sought to quantify the time-related probability of recurrent rejection and identify risk factors for the development of recurrent rejection. METHODS: We analyzed data from 847 pediatric recipients who underwent transplantation between January 1, 1993 and December 31, 1998 at 22 centers in the Pediatric Heart Transplant Study (PHTS). Recurrent rejection and risk factors were evaluated using univariate and multivariate analyses. RESULTS: Five hundred fifty two patients had 1,072 rejection events and were the subject of the analyses. The highest risk of recurrent rejection occurs within 1 month after resolution of a previous rejection episode. Risk factors for recurrent rejection include the number of previous rejection events, the elapsed time since a previous rejection episode, and subjects of either Hispanic or African-American descent. Rejection associated with hemodynamic compromise and late rejection is associated with higher mortality. CONCLUSIONS: Recurrent rejection is a risk factor for mortality, especially in the presence of hemodynamic compromise. This association appears independent of the time post-transplantation. Use of surveillance biopsies appears warranted throughout the life of the transplant individual. Retransplantation should be considered among these subjects with recurrent rejection.

Adult↗

PubMed2004

Identifying cardiac transplant rejection in children: diagnostic utility of echocardiography, right heart catheterization and endomyocardial biopsy data.

BACKGROUND: There has been a continued search for alternative diagnostic techniques that do not necessitate endomyocardial biopsy for diagnosing rejection in cardiac transplant recipients. The purpose of this study is to evaluate the role of echocardiography and hemodynamic catheterization data compared with endomyocardial biopsy results, in rejection surveillance for the pediatric heart transplant recipient. METHODS: A prospective, blinded evaluation was performed utilizing echocardiographic and standard right heart catheterization parameters to predict acute rejection episodes. RESULTS: Forty-nine patients underwent 281 biopsies. Two groups were defined: those with Grade <2 rejection and those with grade > or =2 rejection. None of the echocardiographic variables showed significant differences between the study groups and all group data were within normal limits. Mixed venous saturation, mean right atrial pressure, right ventricular end-diastolic pressure and mean pulmonary artery pressure were found to be statistically significant between groups. Receiver-operator characteristic (ROC) curves were constructed to determine the extent to which the various parameters were clinically useful. The ROC found little clinical usefulness for all variables, including those found to be statistically significant. CONCLUSIONS: Differences in both echocardiographic and hemodynamic data were not clinically significant between the 2 groups of patients. Although many of the catheterization-derived parameters were statistically significant, they did not permit effective discrimination between groups. This is the only clinically relevant application of such data and may explain the conflicting previous reports. It is only through analyses such as ROC that the clinical application (or lack thereof) can be appreciated in this population.

Biopsy↗

PubMed2003

Exercise assessment of transgenic models of human cardiovascular disease.

Exercise provides one of the most severe, yet physiological, stresses to the intact cardiovascular system and is a major determinant of the utilization of metabolic substrates. The adaptations to exercise are the result of a coordinated response of multiple organ systems, including cardiovascular, pulmonary, endocrine-metabolic, immunologic, and skeletal muscle. With the proliferation of genetically altered murine models of cardiovascular disease, the importance of developing methods of accurate physiological phenotyping is critical. There are numerous examples of transgenic models in which the baseline cardiovascular phenotype is unchanged or minimally changed from the wild type, only to become manifest during the stress of exercise testing. In this review, we cover the basics of the murine cardiovascular response to exercise and the importance of attending to strain differences, compare different exercise methodologies (constant workload treadmill, incremental workload treadmill, swimming) and hemodynamic monitoring systems, and examine the murine response to exercise conditioning. Several examples where exercise studies have contributed to the elucidation of cardiovascular phenotypes are reviewed: the beta-adrenergic receptor knockouts, phospholamban knockout, dystrophin knockout (mdx), and the mutant alpha-myosin heavy chain (R403Q) transgenic.

Animals↗

PubMed2003

Atrial tachyarrhythmias and permanent pacing after pediatric heart transplantation.

BACKGROUND: Atrial tachyarrhythmias have been reported in as high as 50% of adult heart recipients. Limited information is available on arrhythmias in pediatric transplant patients. Our objective was to determine the prevalence and significance of atrial tachyarrhythmias and permanent pacing following pediatric heart transplantation. METHODS: A retrospective review of the medical records, electrocardiograms, and Holter recordings of all consecutive patients following heart transplantation at Children's Hospital, Boston (n = 104) and Lucile Packard Children's Hospital, Stanford (n = 123) was performed. The study group consisted of 227 patients with a median age at transplant of 10.2 yrs (1 day-23.3 yrs). RESULTS: Atrial tachyarrhythmias occurred in 32 patients (14%) at a median of 15 days post-transplant (1 day-9.2 yrs) and included atrial flutter (n = 13), atrial fibrillation (n = 7), ectopic atrial tachycardia (n = 5), atrioventricular reciprocating tachycardia or atrioventricular node reentry (n = 5), and other (n = 2). Atrial flutter was the only tachyarrhythmia associated with allograft rejection (6/13 atrial flutter vs. 0/7 atrial fibrillation vs. 0/5 ectopic atrial tachycardia, p = 0.03). Patients with atrial fibrillation had a 2.5 fold (95%CI 1.7-3.5) higher risk of death or retransplant compared to patients without atrial fibrillation. Ectopic atrial tachycardia tended to occur in younger recipients compared to atrial fibrillation and flutter (2.7 yrs vs 18.6 yrs and 8.5 yrs respectively, p = 0.06) and was associated with a benign clinical course. There was no association between atrial tachyarrhythmias and graft ischemic time, surgical technique, or coronary artery disease. Pacemakers were required in 12 patients (5.2%), 7 with sinus node dysfunction and 5 for intermittent complete atrioventricular block. There was no consistent association between the need for permanent pacing and coronary artery disease, rejection, or surgical technique. CONCLUSIONS: Atrial tachyarrhythmias and permanent pacing were uncommon in this cohort of pediatric heart transplant recipients. Association with cardiac rejection, clinical course, and mortality varied depending on the tachyarrhythmia mechanism.

Atrial Fibrillation↗

PubMed2002

Cardiovascular and metabolic alterations in mice lacking beta1- and beta2-adrenergic receptors.

Targeted disruption of murine beta-adrenergic receptor (beta-AR) genes has helped to clarify the role of specific beta-AR subtypes in regulating cardiovascular development and function. In the mouse, the beta1-AR is primarily responsible for sympathetic regulation of both cardiac chronotropy and inotropy. In contrast, all three beta-ARs play a role in regulating peripheral vascular tone. The impact of ablation of both beta1- and beta2-ARs on cardiac development and on resting cardiovascular and metabolic parameters is remarkably minimal. However, exercise stress reveals additional important contributions of beta1- and beta2-ARs to cardiovascular performance.

Animals↗

PubMed2002

Long-term follow-up after total lymphoid irradiation in pediatric heart transplant recipients.

BACKGROUND: Total lymphoid irradiation (TLI) is used to treat recurrent allograft rejection. Short-term success and complication rates have been reported in pediatric and adult cardiac transplant populations. We report the long-term efficacy and safety of TLI in treating intractable rejection in pediatric patients. METHODS: Eight pediatric patients were treated with TLI (7 for recurrent rejection, 1 for risk of medication non-compliance). Therapy consisted of a mid-plane dose of 8 Gy administered with a 6-MeV linear accelerator using an anterior-posterior opposed technique. We reviewed outcomes for a total of 40 patient-years of follow-up. RESULTS: We encountered rejection (>Grade 2 by International Society for Heart and Lung Transplantation criteria) in 56.7% +/- 34.7% of biopsies performed within 90 days before TLI. Rejection rates dropped to 3.1% +/- 8.8% within the first 90 days (p < 0.005) after therapy and remained low at 5.6% +/- 1.3% (p < 0.05) during the first year after completion of TLI. Median time from TLI to the first subsequent rejection episode was 305 days (range, 77-1,920 days). Long-term follow-up (>3 years) of 5 patients demonstrated a continuing low incidence of rejection. Non-Hodgkin's lymphoma was diagnosed in 1 of 8 patients, graft coronary artery disease in 4 of 8 patients, and restrictive cardiomyopathy in 1 of 8 patients after TLI. CONCLUSIONS: Total lymphoid irradiation is an effective treatment for recurrent rejection and has short- and long-term efficacy. Morbid events may include cancer, graft coronary artery disease, and restrictive cardiomyopathy.

Adolescent↗

PubMed2002

Efficacy and safety of atorvastatin after pediatric heart transplantation.

BACKGROUND: Lipid abnormalities are prevalent after pediatric and adult heart transplantation. 3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors are efficacious and safe and can lower the incidence of graft coronary artery disease after heart transplantation in adults. Given the high prevalence of lipid abnormalities and the increased recognition of graft coronary disease in children, we retrospectively investigated the efficacy and safety of atorvastatin among pediatric heart transplant recipients. METHODS: Thirty-eight patients were started on atorvastatin 48.2 +/- 54.4 months after transplantation. Atorvastatin dosage was 0.2 +/- 0.1 mg/kg per day. No patient had changes in drug dose unless there was evidence for rhabdomyolysis, myositis or an asymptomatic rise in creatine kinase above normal. Laboratory studies included total cholesterol, triglycerides; high, low and very low-density lipoproteins (HDL, LDL and VLDL, respectively); creatine kinase; creatine; and serum alanine transaminase. RESULTS: Significant declines in total cholesterol (20%), triglyceride (18%) and LDL (26%) were observed after starting atorvastatin therapy. There were no significant changes in HDL or VLDL compared with baseline. There were also no differences in alanine transaminase pre- vs post-atorvastatin therapy. Complications included muscle pain (n = 2) and asymptomatic elevations in creatine kinase (n = 2). Two of these 4 patients developed rhabdomyolysis. Excluding these 4 patients, creatine kinase did not rise compared with baseline. No patient developed alterations in renal function. CONCLUSIONS: Use of atorvastatin in pediatric heart transplant recipients is effective in lowering total cholesterol, triglyceride and LDL without altering HDL levels. Complications included rhabdomyolysis, seen in 5%. Baseline and routine screening of creatine kinase should be employed in all pediatric patients undergoing HMG-CoA reductase inhibitor therapy.

Adolescent↗

PubMed2002

Abnormal cardiac function associated with sympathetic nervous system hyperactivity in mice.

alpha(2A)-Adrenergic receptors (ARs) in the midbrain regulate sympathetic nervous system activity, and both alpha(2A)-ARs and alpha(2C)-ARs regulate catecholamine release from sympathetic nerve terminals in cardiac tissue. Disruption of both alpha(2A)- and alpha(2C)-ARs in mice leads to chronically elevated sympathetic tone and decreased cardiac function by 4 mo of age. These knockout mice have increased mortality, reduced exercise capacity, decreased peak oxygen uptake, and decreased cardiac contractility relative to wild-type controls. Moreover, we observed significant abnormalities in the ultrastructure of cardiac myocytes from alpha(2A)/alpha(2C)-AR knockout mice by electron microscopy. Our results demonstrate that chronic elevation of sympathetic tone can lead to abnormal cardiac function in the absence of prior myocardial injury or genetically induced alterations in myocardial structural or functional proteins. These mice provide a physiologically relevant animal model for investigating the role of the sympathetic nervous system in the development and progression of heart failure.

Animals↗