Perspectives on the value of biomarkers in acute cardiac care and implications for strategic management

Lactate and Myocardiac Energy Metabolism

The myocardium is capable of utilizing different energy substrates, which is referred to as "metabolic flexibility." This process assures ATP production from fatty acids, glucose, lactate, amino acids, and ketones, in the face of varying metabolic contexts. In the normal physiological state, the oxidation of fatty acids contributes to approximately 60% of energy required, and the oxidation of other substrates provides the rest. The accumulation of lactate in ischemic and hypoxic tissues has traditionally be considered as a by-product, and of little utility. However, recent evidence suggests that lactate may represent an important fuel for the myocardium during exercise or myocadiac stress. This new paradigm drives increasing interest in understanding its role in cardiac metabolism under both physiological and pathological conditions. In recent years, blood lactate has been regarded as a signal of stress in cardiac disease, linking to prognosis in patients with myocardial ischemia or heart failure. In this review, we discuss the importance of lactate as an energy source and its relevance to the progression and management of heart diseases.

Evaluation of intracoronary blood from obstructive vessel in patients of ST-elevation myocardial infarction undergoing PPCI

Objective

Information available on acid–base imbalance in ST-elevation myocardial infarction (STEMI) submitted to primary percutaneous intervention is limited and no data were present on intracoronary blood analysis, extracted from obstructed artery.

Methods

This was a prospective study conducted over 12 months in which STEMI patients presenting in emergency and undergoing primary percutaneous coronary intervention were included. Blood gas analysis of intracoronary arterial blood from obstructed vessel and peripheral arterial blood was performed. Patients in whom adequate intracoronary sample could not be obtained were excluded. Intracoronary and peripheral arterial blood gas measurements were correlated and relationship of intracoronary parameters were compared with clinical parameters, investigational markers and short-term outcome.

Results

The mean age of study population was 54.8 years and average symptom onset to door time was 162 min. On comparing intracoronary blood with peripheral blood arterial obtained, pH (95% confidence interval [CI] −0.01 to 0.02;p = 0.44), lactate (95% CI 0.03–0.1;p = 0.28), bicarbonate (95% CI 0.6–1.5;p = 0.64), pCO₂ (95% CI 1.1–2.4;p = 0.79) and pO₂ (95% CI 3.2–47.5; p = 0.06) were all found to be statistically insignificant. Intracoronary hyperlactatemia was present in patients presenting with higher symptom onset to door time (p = 0.025). Systolic blood pressure (SBP) (p = 0.03) was also significantly lower in patients who had high intracoronary lactate levels.

Conclusion

The evaluation of intracoronary blood provides no additional information regarding the prognosis and short-term (30-day) outcome of the patients when compared with peripheral blood. However, there was a significant intracoronary hyperlactatemia in patients presenting late after symptom onset. SBP was also significantly less in patients with high intracoronary lactate, which signifies that predominant cause of hyperlactatemia was systemic hypoperfusion rather than local increase in lactate levels.

Inverse changes in plasma tetranectin and titin levels in patients with type 2 diabetes mellitus: a potential predictor of acute myocardial infarction?

An early intervention using biomarkers to predict acute myocardial infarction (AMI) will effectively reduce global heart attack incidence, particularly among high-risk patients with type 2 diabetes mellitus (T2DM). This study attempted to identify potential biomarkers by detecting changes in the levels of plasma proteins in T2DM patients following onset of AMI in comparison with those without AMI. Volunteer T2DM patients without AMI (control; n=10) and T2DM patients with AMI (n=10) were recruited. Plasma samples from these patients were evaluated via two-dimensional gel electrophoresis (2DE) to screen for proteins with level changes between the two groups. The abundance of spots on gel images was analyzed using Progenesis SameSpots and subjected to false discovery rate (FDR) analysis. Protein spots with statistically significant changes of at least 1.5 fold were selected for mass spectrometry (MS) analysis. Due to strong cardiac connections, tetranectin and titin were evaluated by enzymelinked immunosorbent assay (ELISA). The adjusted P-values and fold changes between the two groups resulted in identification of 34 protein spots with significantly altered abundance. Upon MS analysis, 17 plasma proteins were identified: tetranectin, titin, clusterin, haptoglobin, myosin-13, zinc fnger protein 445, DNA repair protein RAD50, serum albumin, apolipoprotein A-IV, caspase-6, aminoacyl tRNA synthase complex-interacting multifunctional protein 1, serotransferrin, retinol-binding protein 4, transthyretin, alpha-1-antitrypsin, apolipoprotein A-I and serum amyloid A. Comparable patterns of changes in tetranectin and titin between the control and AMI groups were confirmed using ELISA. In summary, tetranectin and titin in plasma appeared to be closely associated with the onset of AMI among T2DM patients and can be used as potential biomarkers for prediction of a cardiac event, though this requires validation in a prospective cohort study.

Dissociated Oxygen Consumption and Carbon Dioxide Production in the Post-Cardiac Arrest Rat: A Novel Metabolic Phenotype

BACKGROUND

The concept that resuscitation from cardiac arrest (CA) results in a metabolic injury is broadly accepted, yet patients never receive this diagnosis. We sought to find evidence of metabolic injuries after CA by measuring O2 consumption and CO2 production (VCO2) in a rodent model. In addition, we tested the effect of inspired 100% O2 on the metabolism.

METHODS AND RESULTS

Rats were anesthetized and randomized into 3 groups: resuscitation from 10-minute asphyxia with inhaled 100% O2 (CA-fraction of inspired O2 [FIO2] 1.0), with 30% O2 (CA-FIO2 0.3), and sham with 30% O2 (sham-FIO2 0.3). Animals were resuscitated with manual cardiopulmonary resuscitation. The volume of extracted O2 (VO2) and VCO2 were measured for a 2-hour period after resuscitation. The respiratory quotient (RQ) was RQ=VCO2/VO2. VCO2 was elevated in CA-FIO2 1.0 and CA-FIO2 0.3 when compared with sham-FIO2 0.3 in minutes 5 to 40 after resuscitation (CA-FIO2 1.0: 16.7±2.2, P<0.01; CA-FIO2 0.3: 17.4±1.4, P<0.01; versus sham-FIO2 0.3: 13.6±1.1 mL/kg per minute), and then returned to normal. VO2 in CA-FIO2 1.0 and CA-FIO2 0.3 increased gradually and was significantly higher than sham-FIO2 0.3 2 hours after resuscitation (CA-FIO2 1.0: 28.7±6.7, P<0.01; CA-FIO2 0.3: 24.4±2.3, P<0.01; versus sham-FIO2 0.3: 15.8±2.4 mL/kg per minute). The RQ of CA animals persistently decreased (CA-FIO2 1.0: 0.54±0.12 versus CA-FIO2 0.3: 0.68±0.05 versus sham-FIO2 0.3: 0.93±0.11, P<0.01 overall).

CONCLUSIONS

CA altered cellular metabolism resulting in increased VO2 with normal VCO2. Normal VCO2 suggests that the postresuscitation Krebs cycle is operating at a presumably healthy rate. Increased VO2 in the face of normal VCO2 suggests a significant alteration in O2 utilization in postresuscitation. Several RQ values fell well outside the normally cited range of 0.7 to 1.0. Higher FIO2 may increase VO2, leading to even lower RQ values.

Differential expression of B-type natriuretic peptide between left and right ventricles, with particular regard to sudden cardiac death

The aim of the present study was to investigate the differential expression of B-type natriuretic peptide (BNP) between the left and right ventricle (RV) in sudden cardiac death (SCD). A total of 26 forensic autopsy cases of sudden death (survival time <30 min, postmortem interval <48 h or frozen within 6 h following death) in the present institute were examined. The cases consisted of acute ischemic heart disease (AIHD, n=15) with/without apparent myocardial necrosis as a sign of infarction (acute myocardial infarction, n=6; ischemic heart disease, IHD, n=9), and arrhythmogenic right ventricular cardiomyopathy (ARVC/D, n=5), in addition to traffic accidents and high falls without any pre existing heart disease as control (C, total n=6). BNP was investigated in all cases by the colloidal gold method, hematoxylin-eosin staining, immunohistochemistry (IHC) and the molecular pathological method. The IHC results demonstrated that a positive BNP immunostaining was detected in all groups; however, there was no difference between different causes of death. Pericardial N-terminal (NT)-proBNP concentration was significantly increased in deaths resulting from AIHD and ARVC/D compared with control group. The relative quantification of BNP mRNA demonstrated that relative expression levels of BNP mRNA were significantly increased in the left ventricle (LV) in the AIHD group, and in the RV of the ARVC/D group. The relative quantification difference and ratio of BNP mRNA between LV and RV demonstrated a significantly greater value in the AIHD group compared with control group. BNP mRNA in myocardium and NT-proBNP concentration in pericardial fluid were elevated in SCD patients, and left ventricular dysfunction predominated in AIHD patients, whereas right ventricular dysfunction predominated in ARVC/D patients. The results of the present study suggest the possible use of molecular pathology of BNP for the determination of terminal cardiac function in SCD and analysis of its fatal mechanism in forensic practice.

Diagnostic Value of Soluble Suppression of Tumorigenicity-2 for Heart Failure

Background:

Many studies have explored the diagnostic performance of soluble suppression of tumorigenicity-2 (sST2) for heart failure (HF), but the results are inconsistent. Here, we performed a meta-analysis to assess the role of sST2 in the diagnosis of HF.

Methods:

We searched PubMed, Web of Science, Cochrane Library, China National Knowledge Infrastructure, and Wanfang Database from inception to April 2015. Studies that investigated the diagnostic role of sST2 for HF were reviewed. The numbers of true-positive, false-positive, false-negative, and true-negative results were extracted to calculate pooled diagnostic odds ratio (DOR) with 95% confidence interval (CI) and the summary receiver operating characteristic curve and area under the curve (AUC). The Spearman correlation coefficient was used to check the threshold effect. The Cochran Q statistic (P < 0.05) and the inconsistency index (I² > 50%) were used to assess the nonthreshold effect. Meta-regression was conducted to explore the source of heterogeneity; subgroup analysis showed the results in different subgroups. Finally, the Deeks’ test was performed to assess the publication bias.

Results:

Nine articles including 10 studies were included in the meta-analysis. The pooled sensitivity was 0.84 (95% CI: 0.81–0.86), and pooled specificity was 0.74 (95% CI: 0.72–0.76). The summary DOR was 8.49 (95% CI: 4.54–15.86), and AUC was 0.81 (standard error: 0.03). The Spearman correlation coefficient identified the nonsignificant threshold effect (coefficient = 0.49, P = 0.148), but the nonthreshold effect heterogeneity was significant (Cochran Q = 58.52, P < 0.0001; I² = 84.6%). Meta-regression found that characteristics of controls might be the suggestive source of nonthreshold effect heterogeneity (P = 0.095). Subgroup analysis found that DOR was 5.65 and 7.86, respectively for the controls of hospital patients and healthy populations. Deeks’ test demonstrated that there was no publication bias (P = 0.616).

Conclusion:

The meta-analysis illustrated that sST2 might play a role in diagnosing HF.

Natriuretic peptides as biomarkers of cardiac endocrine function in heart failure: new challenges and perspectives

Several studies indicated that B-type natriuretic peptide (BNP) assay is able to detect patients even in the early phases of heart failure (HF), when the myocardial remodeling process may be still reversible. BNP assay may assist the physician to initiate appropriate and prompt pharmacological treatments. However, clinical relevance and result interpretation of BNP assay for the guide of therapy or in particular clinical conditions, such as renal failure or treatment with inhibitors of enzymes degrading BNP in HF patients, are still debated. The aim of this article is to discuss some still controversial issues concerning the clinical use of measurement of cardiac natriuretic peptides, and also to provide a general overview and some perspectives related to pathophysiological mechanisms of HF.

Role of Biomarkers in the Diagnosis, Risk Assessment, and Management of Pulmonary Hypertension

Pulmonary hypertension is a severe and debilitating disease with no definite cure, and the domain of targeted therapies is a promising field for better management of this severe condition. The disease comprises pulmonary arterial remodeling, hypoxia, endothelial dysfunction, and inflammation, with subsequent organ damage including right heart and liver dysfunction. Biomarkers have a valuable role at different levels of the disease, from diagnosis to risk assessment and management, in order to decrease the burden of the disease in terms of both morbidity and mortality.

Ammonia Induces Autophagy through Dopamine Receptor D3 and MTOR

Hyperammonemia is frequently seen in tumor microenvironments as well as in liver diseases where it can lead to severe brain damage or death. Ammonia induces autophagy, a mechanism that tumor cells may use to protect themselves from external stresses. However, how cells sense ammonia has been unclear. Here we show that culture medium alone containing Glutamine can generate milimolar of ammonia at 37 degrees in the absence of cells. In addition, we reveal that ammonia acts through the G protein-coupled receptor DRD3 (Dopamine receptor D3) to induce autophagy. At the same time, ammonia induces DRD3 degradation, which involves PIK3C3/VPS34-dependent pathways. Ammonia inhibits MTOR (mechanistic target of Rapamycin) activity and localization in cells, which is mediated by DRD3. Therefore, ammonia has dual roles in autophagy: one to induce autophagy through DRD3 and MTOR, the other to increase autophagosomal pH to inhibit autophagic flux. Our study not only adds a new sensing and output pathway for DRD3 that bridges ammonia sensing and autophagy induction, but also provides potential mechanisms for the clinical consequences of hyperammonemia in brain damage, neurodegenerative diseases and tumors.

CXCR2 Inhibition Combined with Sorafenib Improved Antitumor and Antiangiogenic Response in Preclinical Models of Ovarian Cancer

Antiangiogenic therapy is important for the treatment of gynecological cancer. However, the therapeutic benefit derived from these treatments is transient, predominantly due to the selective activation of compensatory proangiogenic pathways that lead to rapid development of resistance. We aimed to identify and target potential alternative signaling to anti-vascular endothelial growth factor (VEGF) therapy, with a view toward developing a combination of antiangiogenic agents to provide extended therapeutic benefits. We developed a preclinical in vivo phenotypic resistance model of ovarian cancer resistant to antiangiogenic therapy. We measured dynamic changes in secreted chemokines and angiogenic signaling in tumors and plasma in response to anti-VEGF treatment, as tumors advanced from the initial responsive phase to progressive disease. In tumors that progressed following sorafenib treatment, gene and protein expression levels of proangiogenic CXC chemokines and their receptors were significantly elevated, compared with responsive tumors. The chemokine (C-X-C motif) ligand 8 (CXCL8), also known as interleukin-8 (IL-8) increase was time-dependent and coincided with the dynamics of tumor progression. We used SB225002, a pharmacological inhibitor of chemokine (C-X-C motif) receptor 2 (CXCR2), to disrupt the CXC chemokine-mediated functions of ovarian cancer cells in in vitro assays of cell growth inhibition, spheroid formation, and cell migration. The combination of CXCR2 inhibitor with sorafenib led to a synergistic inhibition of cell growth in vitro, and further stabilized tumor progression following sorafenib in vivo. Our results suggest that CXCR2-mediated chemokines may represent an important compensatory pathway that promotes resistance to antiangiogenic therapy in ovarian cancer. Thus, simultaneous blockage of this proangiogenic cytokine pathway using CXCR2 inhibitors and the VEGF receptor (VEGFR) pathway could improve the outcomes of antiangiogenic therapy.

Clinical significance of lactate in acute cardiac patients

Lactate, as a metabolite of easy and quick assessment, has been studied over time in critically ill patients in order to evaluate its prognostic ability. The present review is focused on the prognostic role of lactate levels in acute cardiac patients (that is with acute coronary syndrome, cardiogenic shock, cardiac arrest, non including post cardiac surgery patients). In patients with ST-elevation myocardial infarction treated with mechanical revascularization, hyperlactatemia identified a subset of patients at higher risk for early death and in-hospital complications, being strictly related mainly to hemodynamic derangement. The prognostic impact of hyperlactatemia on mortality has been documented in patients with cardiogenic shock and in those with cardiac arrest even if there is no cut-off value of lactate to be associated with worse outcome or to guide resuscitation or hemodynamic management. Therapeutic hypothermia seems to affect per se lactate values which have been shown to progressively decrease during hypothermia. The mechanism(s) accounting for lactate levels during hypothemia seem to be multiple ranging from the metabolic effects of reduced temperatures to the hemodynamic effects of hypothermia (i.e., reduced need of vasopressor agents). Serial lactate measurements over time, or lactate clearance, have been reported to be clinically more reliable than lactate absolute value also in acute cardiac patients. Despite differences in study design, timing of lactate measurements and type of acute cardiac conditions (i.e., cardiogenic shock, cardiac arrest, refractory cardiac arrest), available evidence strongly suggests that higher lactate levels can be observed on admission in non-survivors and that higher lactate clearance is associated with better outcome.

Prognostic value of sST2 added to BNP in acute heart failure with preserved or reduced ejection fraction

BACKGROUND

Natriuretic peptides and suppression of tumorigenicity 2 (ST2) represent two different physiopathological pathways. We evaluated the prognostic accuracy and complementarity of B-type natriuretic peptide (BNP) and soluble ST2 (sST2) plasma levels at discharge from a hospital admission for acute heart failure, both in patients with preserved (HFpEF) and depressed (HFrEF) systolic function.

METHODS AND RESULTS

We enrolled 195 consecutive patients discharged alive and followed them prospectively for 6 months. The endpoint was all-cause death or hospital readmission for heart failure. Seventy-six patients had HFpEF and 119 had HFrEF, of whom 23 (30.3%) and 43 (36.1%) reached the combined endpoint, respectively. In both HFpEF and HFrEF, having the two biomarkers into account added prognostic information, with the highest risk in patients with both biomarkers above the median in their group (approximately 40% hospitalization-free survival in both groups at 6 months). These associations translated into a significant fourfold increase in risk of the endpoint for one elevated biomarker and sevenfold for both biomarkers elevated in HFrEF, and no association for one elevated biomarker and fivefold increase in risk for both biomarkers elevated in HFpEF. Considering the reclassification of risk added to BNP by measurement of sST2, net reclassification index was 0.31 (p = 0.21) among patients with HFpEF and 0.70 (p < 0.001) among patients with HFrEF.

CONCLUSIONS

sST2 provides robust prognostic information in acute heart failure with HFrEF, while this pattern was less clear in HFpEF. When sST2 was measured together with BNP, it improved prognostic accuracy in both groups, more clearly in HFrEF.

Can Saliva Proteins Be Used to Predict the Onset of Acute Myocardial Infarction among High-Risk Patients?

Human saliva plays a pivotal role in digesting food and maintaining oral hygiene. The presence of electrolytes, mucus, glycoproteins, enzymes, antibacterial compounds, and gingival crevicular fluid in saliva ensures the optimum condition of oral cavity and general health condition. Saliva collection has been proven non-invasive, convenient, and inexpensive compared to conventional venipuncture procedure. These distinctive advantages provide a promising potential of saliva as a diagnostic fluid. Through comprehensive analysis, an array of salivary proteins and peptides may be beneficial as biomarkers in oral and systemic diseases. In this review, we discuss the utility of human salivary proteomes and tabulate the recent salivary biomarkers found in subjects with acute myocardial infarction as well as respective methods employed. In a clinical setting, since acute myocardial infarction contributes to large cases of mortality worldwide, an early intervention using these biomarkers will provide an effective solution to reduce global heart attack incidence particularly among its high-risk group of type-2 diabetes mellitus patients. The utility of salivary biomarkers will make the prediction of this cardiac event possible due to its reliability hence improve the quality of life of the patients. Current challenges in saliva collection are also addressed to improve the quality of saliva samples and produce robust biomarkers for future use in clinical applications.

Role of point of care - ST2, Galectin-3 and adrenomedullin in the evaluation and treatment of emergency patients

There have been many technological advances improving the work up and treatment of patients in the emergency department (ED). Point of care testing (POCT) is becoming more common, especially in the time compressed clinically high-pressured environment of the emergency department. In present times, emphasis of POCT has spurred search of novel biomarkers which promise earlier and more specific detection of disease. This article reviews the role of ST₂, Galectin-3 and Adrenomedullin in the acute care setting addressing the screening, diagnostic, and prognostic role of each marker for stratification of patients. Use of these markers has shown a strong correlation with early identification and efficient management in the ED.