Sebastian J. Buss

High-Mobility Group Box-1 in Ischemia-Reperfusion Injury of the Heart

Background— High-mobility group box-1 (HMGB1) is a nuclear factor released by necrotic cells and by activated immune cells. HMGB1 signals via members of the toll-like receptor family and the receptor for advanced glycation end products (RAGE). Although HMGB1 has been implicated in ischemia/reperfusion (I/R) injury of the liver and lung, its role in I/R injury of the heart remains unclear. Methods and Results— Here, we demonstrate that HMGB1 acts as an early mediator of inflammation and organ damage in I/R injury of the heart. HMGB1 levels were already elevated 30 minutes after hypoxia in vitro and in ischemic injury of the heart in vivo. Treatment of mice with recombinant HMGB1 worsened I/R injury, whereas treatment with HMGB1 box A significantly reduced infarct size and markers of tissue damage. In addition, HMGB1 inhibition with recombinant HMGB1 box A suggested an involvement of the mitogen-activated protein kinases jun N-terminal kinase and extracellular signal-regulated kinase 1/2, as well as the nuclear transcription factor nuclear factor-&kgr;B in I/R injury. Interestingly, infarct size and markers of tissue damage were not affected by administration of recombinant HMGB1 or HMGB1 antagonists in RAGE−/− mice, which demonstrated significantly reduced damage in reperfused hearts compared with wild-type mice. Coincubation studies using recombinant HMGB1 in vitro induced an inflammatory response in isolated macrophages from wild-type mice but not in macrophages from RAGE−/− mice. Conclusions— HMGB1 plays a major role in the early event of I/R injury by binding to RAGE, resulting in the activation of proinflammatory pathways and enhanced myocardial injury. Therefore, blockage of HMGB1 might represent a novel therapeutic strategy in I/R injury.

Longitudinal left ventricular function for prediction of survival in systemic light-chain amyloidosis: incremental value compared with clinical and biochemical markers.

OBJECTIVES The aim of the study was to determine whether longitudinal left ventricular (LV) function provides prognostic information in a large cohort of patients with systemic light-chain (AL) amyloidosis. BACKGROUND AL amyloidosis is associated with a high incidence of cardiovascular events. Reduced myocardial longitudinal function is one of the hallmarks of myocardial involvement in this rare disease. METHODS Two hundred six consecutive patients with biopsy-proven AL amyloidosis were investigated in this prospective observational study. Echocardiographic imaging parameters, mean tissue Doppler-derived longitudinal strain (LS), and two-dimensional global longitudinal strain (2D-GLS) of the LV, cardiac serological biomarkers, and comprehensive clinical disease characteristics were assessed. The primary endpoint was all-cause mortality or heart transplantation. RESULTS After a median follow-up of 1207 days, LS and 2D-GLS were significant predictors of survival in AL amyloidosis. The cutoff values discriminating survivors from nonsurvivors were -10.65% for LS and -11.78% for 2D-GLS. In a multivariable echocardiographic Cox model, only diastolic dysfunction and 2D-GLS remained as independent predictors of survival. In comprehensive clinical models, 2D-GLS (p < 0.0001), diastolic dysfunction (p < 0.01), the pathologic free light chains (p < 0.05), cardiac troponin-T (cTnT) (p < 0.01), and the Karnofsky index (p < 0.001) remained as independent predictors. 2D-GLS delineated a superior prognostic value compared with that derived from pathologic free light chains or cTnT in patients evaluated before firstline chemotherapy (n = 113; p < 0.0001), and remained the only independent predictor besides the Karnofsky index in subjects with preserved LV ejection fraction (≥50%; n = 127; p < 0.01). LS and 2D-GLS both offered significant incremental information (p < 0.001) for the assessment of outcome compared with clinical variables (age, Karnofsky index, and New York Heart Association functional class) and serological biomarkers. CONCLUSIONS In the largest serial investigation reported so far, reduced LV longitudinal function served as an independent predictor of survival in AL amyloidosis and offered incremental information beyond standard clinical and serological parameters.

Wnt Signaling Is Critical for Maladaptive Cardiac Hypertrophy and Accelerates Myocardial Remodeling

The evolutionary conserved Wnt signaling pathway regulates cardiogenesis. However, members of the Wnt pathway are also expressed in the adult heart. Although Wnt-signaling is quiescent under normal conditions, we noticed activation on pathological stress of the heart, such as chronic afterload increase. To examine the role of Wnt signaling on the postnatal heart, we modified the expression and function of the Wnt regulator dishevelled 1 (Dvl-1) both in transgenic mice with cardiac-specific overexpression of Dvl-1 (Dvl-1-Tg) and in cultured cardiac myocytes. Dvl-1-Tg mice (3 months) had severe cardiac hypertrophy (heart weight:body weight ratio: 5.2±0.3 mg/g wild-type [WT] versus 6.4±0.7 mg/g Dvl-1-Tg; P<0.01), an increase in cardiomyocyte size (86% increase in Dvl-1-Tg compared with WT; P<0.01) and marked raise of atrial natriuretic factor expression (12-fold increase versus WT; P<0.01). Hypertrophy was associated with left ventricular dilatation in Dvl-1-Tg and a reduction of ejection fraction (4.4±0.1 mm versus 5.5±0.2 mm, 80±2% and 43±4% in WT versus Dvl-1-Tg, respectively; P<0.01). Transgenic animals died prematurely before 6 months of age. Both canonical as well as noncanonical Wnt signaling branches were activated in the Dvl-1-Tg animals. Small interfering RNA–mediated depletion of Dvl-1 was used to further characterize the role of Dvl-1 in cardiac myocytes. Whereas baseline parameters were unaltered, &bgr;-adrenergic hypertrophic response was abrogated in Dvl-1 knockdown cardiac myocytes, indicating a mandatory role in &bgr;-adrenergic stimulation. Therefore, activation of Wnt signaling is sufficient and critical for the induction of myocardial hypertrophy and cardiomyopathy.

Identification of Cardiac Troponin I Sequence Motifs Leading to Heart Failure by Induction of Myocardial Inflammation and Fibrosis

Background— Despite the widespread use of cardiac troponins for diagnosis of myocyte injury and risk stratification in acute cardiac disorders, little is known about the long-term effects of the released troponins on cardiac function. Recently, we showed that an autoimmune response to cardiac troponin I (cTnI) induces severe inflammation and subsequent fibrosis in the myocardium. This autoimmune disorder predisposes to heart failure and cardiac death in mice. Methods and Results— To investigate the role of cTnI-specific T cells, T cells were isolated from splenocytes of mice immunized with murine cTnI (mcTnI). Wild-type mice that received mcTnI-specific T cells showed high mcTnI-specific antibody titers, increased production of the proinflammatory cytokines interleukin-1&bgr; and tumor necrosis factor-&agr;, severe inflammation and fibrosis in the myocardium, and reduced fractional shortening. To identify the antigenic determinants of troponin I responsible for the observed inflammation, fibrosis, and heart failure, 16 overlapping 16mer to 18mer peptides covering the entire amino acid sequence of mcTnI (211 residues) were synthesized. Only mice immunized with residues 105 to 122 of mcTnI developed significant inflammation and fibrosis in the myocardium, with increased expression of the inflammatory chemokines RANTES, monocyte chemotactic protein-1, macrophage inflammatory protein-1&agr;, macrophage inflammatory protein-1&bgr;, macrophage inflammatory protein-2, T-cell activation-3, and eotaxin and the chemokine receptors CCR1, CCR2, and CCR5. Mice immunized with the corresponding human cTnI residues 104 to 121 and the mcTnI residues 131 to 148 developed milder disease. Conclusions— Transfer of troponin I–specific T cells can induce inflammation and fibrosis in wild-type mice, which leads to deterioration of contractile function. Furthermore, 2 sequence motifs of cTnI that induce inflammation and fibrosis in the myocardium are characterized.

Assessment of myocardial deformation with cardiac magnetic resonance strain imaging improves risk stratification in patients with dilated cardiomyopathy.

AIMS To investigate the prognostic impact of left-ventricular (LV) cardiac magnetic resonance (CMR) deformation imaging in patients with non-ischaemic dilated cardiomyopathy (DCM) compared with late-gadolinium enhancement (LGE) quantification and LV ejection fraction (EF). METHODS AND RESULTS A total of 210 subjects with DCM were examined prospectively with standard CMR including measurement of LGE for quantification of myocardial fibrosis and feature tracking strain imaging for assessment of LV deformation. The predefined primary endpoint, a combination of cardiac death, heart transplantation, and aborted sudden cardiac death, occurred in 26 subjects during the median follow-up period of 5.3 years. LV radial, circumferential, and longitudinal strains were significantly associated with outcome. Using separate multivariate analysis models, global longitudinal strain (average of peak negative strain values) and mean longitudinal strain (negative peak of the mean curve of all segments) were independent prognostic parameters surpassing the value of global and mean LV radial and circumferential strain, as well as NT-proBNP, EF, and LGE mass. A global longitudinal strain greater than -12.5% predicted outcome even in patients with EF < 35% (P < 0.01) and in those with presence of LGE (P < 0.001). Mean longitudinal strain was further investigated using a clinical model with predefined cut-offs (EF < 35%, presence of LGE, NYHA class, mean longitudinal strain greater than -10%). Mean longitudinal strain exhibited an independent prognostic value surpassing that provided by NYHA, EF, and LGE (HR = 5.4, P < 0.01). CONCLUSION LV longitudinal strain assessed with CMR is an independent predictor of survival in DCM and offers incremental information for risk stratification beyond clinical parameters, biomarker, and standard CMR.

Age- and gender-related normal left ventricular deformation assessed by cardiovascular magnetic resonance feature tracking.

BackgroundAssessment of left (LV) ventricular function is one of the most important tasks of cardiovascular magnetic resonance (CMR). Impairment of LV deformation is a strong predictor of cardiovascular outcome in various cardiac diseases like ischemic heart disease or cardiomyopathies. The aim of the study was to provide reference values for myocardial deformation derived from the CMR feature tracking imaging (FTI) algorithm in a reference population of healthy volunteers.MethodsFTI was applied to standard short axis and 2-, 3- and 4-chamber views of vector-ECG gated CMR cine SSFP sequences of 150 strictly selected healthy volunteers (75 male/female) of three age tertiles (mean age 45.8yrs). Global peak and mean radial, circumferential and longitudinal endo- and myocardial systolic strain values as well as early diastolic strain rates were measured using FTI within a standard protocol on a 1.5T whole body MR scanner.ResultsGlobal peak systolic values were 36.3 ± 8.7% for radial, −27.2 ± 4.0% for endocardial circumferential, −21.3 ± 3.3% for myocardial circumferential, −23.4 ± 3.4% for endocardial longitudinal and −21.6 ± 3.2% for myocardial longitudinal strain. Global peak values were -2.1 ± 0.5s−1 for radial, 2.1 ± 0.6s−1 for circumferential endocardial, 1.7 ± 0.5s−1 for circumferential myocardial, 1.8 (1.5-2.2)s−1 for longitudinal endocardial, 1.6 (1.4-2.0)s−1 for longitudinal myocardial early diastolic strain rates. Men showed a higher radial strain than women whereas the circumferential and longitudinal strains were lower resulting in less negative values. Circumferential and longitudinal strain rates were significantly higher in female subjects. Radial strain increased significantly with age whereas the diastolic function measured by the radial, circumferential and longitudinal strain rates showed a decrease.The coefficients of variation determined in ten further subjects, who underwent two CMR examinations within 12 days, were −4.8% for circumferential and −4.5% for longitudinal endocardial mean strains.ConclusionsMyocardial deformation analysis using FTI is a novel technique and robust when applied to standard cine CMR images providing the possibility of a reliable, objective quantification of global LV deformation. Since strain values and strain rates differed partly between genders as well as between age groups, the application of specific reference values as provided by this study is recommendable.

Left ventricular diastolic function in type 2 diabetes mellitus is associated with myocardial triglyceride content but not with impaired myocardial perfusion reserve

To study myocardial perfusion reserve and myocellular metabolic alterations indicated by triglyceride content as possible causes of diastolic dysfunction in patients with type 2 diabetes mellitus, preserved systolic function, and without clinically evident coronary artery disease.

Myocardial left ventricular dysfunction in patients with systemic lupus erythematosus: new insights from tissue Doppler and strain imaging.

Objective. Systemic lupus erythematosus (SLE) is associated with high cardiovascular morbidity and mortality. Cardiovascular involvement is frequently underestimated by routine imaging techniques. Our aim was to determine if new echocardiographic imaging modalities like tissue Doppler (TDI), strain rate (SRR), and strain (SRI) imaging detect abnormalities in left ventricular (LV) function in asymptomatic patients with SLE. Methods. Sixty-seven young patients with SLE (mean age 42 ± 10 yrs) without typical symptoms or signs of heart failure or angina, and a matched healthy control group (n = 40), underwent standard transthoracic echocardiography, TDI, SRR, and SRI imaging of the LV as well as assessment of disease characteristics. Results. Despite findings within the normal range on routine standard 2-dimensional echocardiography, SLE was associated with significantly impaired systolic and diastolic myocardial velocities of the LV measured by TDI [mean global TDI: systolic (s): 2.9 ± 0.9 vs 3.9 ± 0.7 cm/s, p < 0.05; early (e): 4.3 ± 1.5 vs 6.3 ± 1.3 cm/s, p < 0.05; late (a): 2.9 ± 0.8 vs 3.4 ± 0.8 cm/s, p < 0.05; values ± SD); SRR (s: −0.8 ± 0.1 vs −1.1 ± 0.1 s−1; e: 1.1 ± 0.2 vs 1.6 ± 0.3 s−1; a: 0.7 ± 0.1 vs 1.0 ± 0.2 s−1; all p < 0.05); and SR (−15.11 ± 2.2% vs −19.7 ± 1.9%; p < 0.05) compared to the control group. Further, elevated disease activity, measured with the ECLAM and the SLEDAI score, resulted in significantly lower values for LV longitudinal function measured by SRR and SR, but not by TDI. Conclusion. SLE is associated with a significant impairment of systolic and diastolic LV longitudinal function in patients without cardiac symptoms. New imaging modalities provide earlier insight into cardiovascular involvement in SLE and seem to be superior to standard echocardiography to detect subclinical myocardial disease.

Effects of Peyton's Four-Step Approach on Objective Performance Measures in Technical Skills Training: A Controlled Trial

Background: Although skills-lab training is widely used for training undergraduates in technical procedures, the way in which clinical skills are to be used and instructed remains a matter of debate. Purpose: We conducted a randomized controlled trial to evaluate the learning outcome of two different instructional approaches in the context of acquiring procedural–technical skills. Methods: Volunteer 2nd- and 3rd-year medical students were randomly assigned to an intervention group receiving instruction according to Peytons Four-Step Approach (IG; n = 17) or to a control group receiving standard instruction (CG; n = 17). Both groups were taught gastric-tube insertion using a manikin. Following each of the two forms of instruction, participants’ first independent gastric-tube insertions were video recorded and scored by two independent video assessors using binary checklists and global rating forms. The time required for each instructional approach and for the first independent performance of the skill was measured. Results: A total of 34 students agreed to participate in the trial. There were no statistically significant group differences with regard to age, sex, completed education in a medical profession, or completed medical clerkships. The groups did not differ in terms of correct stepwise performance of the procedure as assessed by a binary checklist (p < .802). However, ratings based on global rating scales assessing professionalism and accompanying patient-doctor communication proved significantly better in IG (both ps < .001). The length of the different instructional approaches did not differ significantly between the two groups (IG: 605 ± 65 s; CG: 572 ± 79 s; p < .122), but the time needed for the first independent performance of gastric-tube placement on the manikin was significantly shorter in IG (IG: 168 ± 30 s; CG: 242 ± 53 s; p < .001). Conclusions: Peytons Four-Step Approach is superior to standard instruction with respect to professionalism and accompanying doctor–patient communication and leads to faster performance when trainees perform the learned skill for the first time.

Injection of Nerve Growth Factor Into Stellate Ganglia Improves Norepinephrine Reuptake Into Failing Hearts

An impairment of cardiac norepinephrine reuptake through the neuronal norepinephrine transporter promotes depletion of cardiac norepinephrine stores and local cardiac sympathetic activation in heart failure. Nerve growth factor regulates differentiation and survival of adult sympathetic cells and is decreased in failing hearts. We hypothesized that injection of nerve growth factor into stellate ganglia normalizes cardiac norepinephrine homeostasis in experimental heart failure. Rats with transverse aortic constriction characterized by heart failure, depleted cardiac norepinephrine stores, and impaired cardiac norepinephrine reuptake were used as an experimental model. Nerve growth factor (20 &mgr;g) or saline was directly injected into left stellate ganglia 4 weeks after transverse aortic constriction. Thirty-two hours after injection, determinants of cardiac norepinephrine homeostasis were measured. As compared with saline, nerve growth factor refilled depleted cardiac norepinephrine stores and improved cardiac [3H]-norepinephrine uptake into isolated perfused hearts of transverse aortic constricted rats. In addition, pharmacological blockade of the norepinephrine transporter led to a higher increase in the overflow of endogenous norepinephrine from hearts of nerve growth factor-injected than saline-injected transverse aortic constricted rats. Norepinephrine transporter mRNA levels and the density of cardiac sympathetic nerves were not changed. Thirty-two hours after nerve growth factor injection, echocardiography revealed an increase in fractional shortening as compared with 2 days before injection. In conclusion, nerve growth factor attenuates local cardiac sympathetic overdrive of hypertrophic hearts by improving cardiac norepinephrine reuptake and might represent a novel therapeutic principle in the treatment of heart failure.