Effect of preoperative ivabradine on hemodynamics during elective off-pump CABG.

Background: Ivabradine is a specific heart rate (HR)-lowering agent which blocks the cardiac pacemaker If channels. It reduces the HR without causing a negative inotropic or lusitropic effect, thus preserving ventricular contractility. The authors hypothesized that its usefulness in lowering HR can be utilized in patients undergoing off-pump coronary artery bypass (OPCAB) surgery. Objective: To study the effects of preoperative ivabradine on hemodynamics (during surgery) in patients undergoing elective OPCAB surgery. Methods: Fifty patients, New York Heart Association (NYHA) class I and II, were randomized into group I (control, n = 25) and group II (ivabradine group, n = 25). In group I, patients received the usual anti-anginal medications in the preoperative period, as per the institutional protocol. In group II, patients received ivabradine 5 mg twice daily for 3 days before surgery, in addition to the usual anti-anginal medications. Anesthesia was induced with fentanyl, thiopentone sodium, and pancuronium bromide as a muscle relaxant and maintained with fentanyl, midazolam, pancuronium bromide, and isoflurane. The hemodynamic parameters [HR and mean arterial pressure (MAP)] and pulmonary artery (PA) catheter-derived data were recorded at the baseline (before induction), 3 min after the induction of anesthesia at 1 min and 3 min after intubation and at 5 min and 30 min after protamine administration. Intraoperatively, hemodynamic data (HR and MAP) were recorded every 10 min, except during distal anastomosis of the coronary arteries when it was recorded every 5 min. Post-operatively, at 24 hours, the levels of troponin T and brain natriuretic peptide (BNP) were measured. This trial's CTRI registration number is CTRI/005858. Results: The HR in group II was lower when compared to group I (range 59.6-72.4 beats/min and 65.8-80.2 beats/min, respectively) throughout the study period. MAP was comparable [range (78.5-87.8 mm Hg) vs. (78.9-88.5 mm Hg) in group II vs. group I, respectively] throughout the study period. Intraoperatively, 5 patients received metoprolol in group I to control the HR, whereas none of the patients in group II required metoprolol. The incidence of preoperative bradycardia (HR <60 beats/min) was higher in group II (20%) vs. group I (8%). There was no difference in both the groups in terms of troponin T and BNP level after 24 hours, time to extubation, requirement of inotropes, incidence of arrhythmias, in-hospital morbidity, and 30-day mortality. Conclusion: Ivabradine can be safely used along with other anti-anginal agents during the preoperative period in patients undergoing OPCAB surgery. It helps to maintain a lower HR during surgery and reduces the need for beta-blockers in the intraoperative period, a desirable and beneficial effect in situations where the use of beta-blockers may be potentially harmful. Further studies are needed to evaluate the beneficial effects of perioperative Ivabradine in patients with moderate-to-severe left ventricular dysfunction.

UR-144, synthetic cannabinoid receptor agonist, induced cardiomyoblast toxicity mechanism comprises cytoplasmic Ca2+ and DAPK1 related autophagy and necrosis.

UR-144, a cannabinoid receptor agonist, is widely used alone or in combination with other synthetic cannabinoids (SCs) all over the world. At overdose, cardiovascular symptoms have been reported and the underlying molecular mechanisms of these adverse effects are not known. It is highly important to clarify the toxic effects of UR-144 for the treatment of poisoning. In the present study, the molecular mechanism of cytotoxic effects of UR-144 is evaluated on a cardiomyoblastic cell line using WST-1 and LDH assays. Apoptosis/necrosis, autophagy, and ROS (reactive oxygen species) levels were determined using flow cytometry. Cytoplasmic Ca2+ levels were measured by using a fluorogenic calcium-binding dye. Released and cytoplasmic troponin T levels, a specific marker of cardiotoxicity, were examined with western blot. For the evaluation of the role of DAPK1, on UR-144-induced cell death, DAPK1 activity and DAPK1 protein level were investigated. Its cytotoxic effects increased in a dose-dependent manner for WST-1 and LDH assays, while membrane damage, one of the signs of necrotic cell death, was more remarkable than damage to mitochondria. Cytoplasmic Ca2+ levels rose after high-dose UR-144 treatment and inhibition of DAPK1 activity ameliorated UR-144-induced cytotoxicity. Released troponin T significantly increased at a dose of 200 µM. ROS and total antioxidant capacity of cells were both reduced following high dose UR-144 treatment. The results indicated that UR-144-induced autophagic and necrotic cell death might be a consequence of elevated cytoplasmic Ca2+ levels and DAPK1 activation. However, in vivo/clinical studies are needed to identify molecular mechanisms of cardiotoxic effects of UR-144.

Role of High-Sensitivity Troponin-T And N-Terminal Pro B-Type Natriuretic Peptide as an Early Predictor of Myocardial Dysfunction in Aneurysmal Subarachnoid Hemorrhage: A Prospective Observational Study.

Background: Acute cardiac complications are commonly seen in aneurysmal subarachnoid hemorrhage (aSAH) patients and may vary from subclinical electrocardiographic abnormalities, or reduced ejection fraction on echocardiography, elevated levels of cardiac markers (cardiac troponin and Brain natriuretic peptide) to heart failure. Objective: This study was done to evaluate the role of cardiac markers (high-sensitive Troponin-T and N-terminal pro-B-type natriuretic peptide) in early identification of cardiac complications and hence dysfunction. Methods: All consecutive patients with aSAH without any previous cardiac history were included. At admission, neurological evaluation using Hunt and Hess grading (H and H grade), with electrocardiography to look for any changes, echocardiography for ejection fraction, and any wall motion abnormalities was also done. The serial serum levels of high-sensitive Troponin-T (hsTnT) and N-terminal pro B-type natriuretic peptide (NT pro-BNP) for 7 consecutive days was measured with hsTnT >0.14 ng/ml and NT pro-BNP >150 pg/mL considered elevated. Results: A total of 69 patients were included. The elevated peak level of hsTnT and NT pro-BNP was seen in 55.1% and 69.6% of patients. A positive correlation was seen between hsTnT (P = 0.033) and NT pro-BNP (P = 0.011) and poor SAH grade (H and H grade 3-5), similarly, abnormal ECG also significantly correlated with elevated peak hsTnT (P = 0.002) and NT proBNP (P = 0.000). Also, significant difference in peak hsTnT (P = 0.000) and NT-proBNP (P = 0.000) in patients with or without reduced ejection fraction (EF). Conclusion: The elevated peak levels of hsTnT and NTproBNP along with ECG and echocardiography abnormalities may help in early identification of myocardial injury, hence cardiac dysfunction.

Bergapten mediated inflammatory and apoptosis through AMPK/eNOS/AKT signaling pathway of isoproterenol-induced myocardial infarction in Wistar rats.

Bergapten (BeG) is explored for its anti-inflammatory and antioxidant properties. Myocardial infarction (MI) is reported to be one of the leading cardiovascular diseases characterized by mitochondrial dysfunction and apoptosis. The main purpose of this study is to assess the cardiopreventive effects of BeG (50 mg/kg) in isoproterenol (ISO)-induced MI in Wistar rats. The increased infarct size after ISO induction was reduced simultaneously on treatment with BeG. Similarly, augmented levels of cardiac biomarkers, namely cardiac troponin T, creatine kinase (CK), cardiac troponin I, and CK-MB were also suppressed by BeG. The increased rate of lipid hydroperoxides and thiobarbituric acid reactive substances owing to the oxidative stress caused by free radical generation in ISO-induced rats were also inhibited by BeG. Antioxidants reduce oxidative stress by scavenging free radicals. ISO induction reduces these antioxidant enzymes glutathione peroxidase, catalase, superoxide dismutase, and glutathione, and levels causing oxidative cardiac damage to the heart tissue. BeG supplementation improved these enzymes synthesis preventing potential damage to the myocardium. Inflammation caused by ISO pretreatment increased the secretion of proinflammatory cytokines in ISO-induced rats. Pretreatment with BeG suppressed these inflammatory cytokines to a normal level in ISO + BeG-treated rats. The histopathological examination of the morphological characteristics showed that the intensity of cardiac damage caused by ISO induction was less in BeG pretreated rats with less inflammatory cells and no necrosis. BeG also showed promising results in the molecular alteration of AMP-activated protein kinase/endothelial nitric oxide synthase/protein kinase B signaling molecules. These observations emphasize the cardioprotective effects of BeG and its potential use as a drug in the near future.

Increased cytosolic calcium buffering contributes to a cellular arrhythmogenic substrate in iPSC-cardiomyocytes from patients with dilated cardiomyopathy.

Dilated cardiomyopathy (DCM) is a major risk factor for heart failure and is associated with the development of life-threatening cardiac arrhythmias. Using a patient-specific induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM) model harbouring a mutation in cardiac troponin T (R173W), we aim to examine the cellular basis of arrhythmogenesis in DCM patients with this mutation. iPSC from control (Ctrl) and DCM-TnT-R173W donors from the same family were differentiated into iPSC-CM and analysed through optical action potential (AP) recordings, simultaneous measurement of cytosolic calcium concentration ([Ca2+]i) and membrane currents and separately assayed using field stimulation to detect the threshold for AP- and [Ca2+]i-alternans development. AP duration was unaltered in TnT-R173W iPSC-CM. Nevertheless, TnT-R173W iPSC-CM showed a strikingly low stimulation threshold for AP- and [Ca2+]i-alternans. Myofilaments are known to play a role as intracellular Ca2+ buffers and here we show increased Ca2+ affinity of intracellular buffers in TnT-R173W cells, indicating increased myofilament sensitivity to Ca2+. Similarly, EMD57033, a myofilament Ca2+ sensitiser, replicated the abnormal [Ca2+]i dynamics observed in TnT-R173W samples and lowered the threshold for alternans development. In contrast, application of a Ca2+ desensitiser (blebbistatin) to TnT-R173W iPSC-CM was able to phenotypically rescue Ca2+ dynamics, normalising Ca2+ transient profile and minimising the occurrence of Ca2+ alternans at physiological frequencies. This finding suggests that increased Ca2+ buffering likely plays a major arrhythmogenic role in patients with DCM, specifically in those with mutations in cardiac troponin T. In addition, we propose that modulation of myofilament Ca2+ sensitivity could be an effective anti-arrhythmic target for pharmacological management of this disease.

The modulatory effect of lithium on doxorubicin-induced cardiotoxicity in rat.

Doxorubicin is an effective anti-neoplastic agent application of which has been limited due to its cardiotoxic side effects. Lithium is widely used for treatment of neuropsychiatric symptoms in bipolar disorders. Lines of evidence point to the cardioprotective effects of lithium against heart injuries. The current study aims to investigate the protective effects of lithium against doxorubicin-induced cardiotoxicity in rat model. Male Wistar rats were treated with 300 mg/kg p.o. lithium in their water supply and/or doxorubicin (1.25 mg/kg, i.p.), four times per week for four weeks. General conditions, mortality rate and body weight were measured during the experiment. At the end of the experiment, ECG parameters and papillary muscle contractility force were assessed. Serum samples were collected to measure the lithium concentrations as well as cardiac troponin T level (cTNT, a biomarker of cardiac injury). In addition, heart weight was measured and the cardiac tissues were evaluated both macroscopically and microscopically. The results of the present study indicate that lithium might diminish mortality rate, general toxicity (edema, alopecia and cachexia), improve S(alpha)-T segment and QT interval prolongations as well as heart contractility force. Application of lithium could inhibit the increase of cardiac troponin T and formation of myocardial lesions. These outcomes show the protective effects of lithium against doxorubicin-induced cardiotoxicity in rat. On the whole, the results of the present study suggest that lithium might be considered as a new indication for the prevention of doxorubicin-induced cardiotoxicity.

Admission troponin T, advanced age and male gender identify patients with improved myocardial tissue perfusion after abciximab administration for ST-segment elevation myocardial infarction.

The aim was to investigate the effect of abciximab on microvascular perfusion in different subgroups of patients undergoing direct PCI for acute STEMI. We enrolled 145 consecutive patients with TIMI grade 3 flow after direct PCI for acute STEMI. The GPIIb/IIIa inhibitor abciximab was administered in 57 patients (39.3%). Myocardial perfusion was the primary outcome measure and was assessed by analysis of cardiac troponin T wash-out. Treatment effects on myocardial perfusion and clinical outcome were tested for predefined subgroups including patients with an admission cTnT > or = 0.1 microg/L, diabetes mellitus, male gender, age > 70 years, and time from symptom onset to reperfusion > 6 hours. A significant improvement of cTnT wash-out was seen in patients with an admission cTnT > or = 0.1 microg/L, in males and in older patients. Improved tissue level reperfusion did not translate into a significant reduction of cardiac mortality or the incidence of the combined endpoint consisting of cardiac death, nonfatal reinfarction and need for target vessel revascularisation during 30 day- and long-term follow-up (mean 274 days). In conclusion, adjunctive administration of abciximab improves myocardial perfusion in patients with normal epicardial flow after direct PCI, particularly in patients with an cTnT > or = 0.1 microg/L on admission, age over 70 years and male gender.

Inherited cardiomyopathies as a troponin disease.

Troponin, one of the sarcomeric proteins, plays a central role in the Ca(2+) regulation of contraction in vertebrate skeletal and cardiac muscles. It consists of three subunits with distinct structure and function, troponin T, troponin I, and troponin C, and their accurate and complex intermolecular interaction in response to the rapid rise and fall of Ca(2+) in cardiomyocytes plays a key role in maintaining the normal cardiac pump function. More than 200 mutations in the cardiac sarcomeric proteins, including myosin heavy and light chains, actin, troponin, tropomyosin, myosin-binding protein-C, and titin/connectin, have been found to cause various types of cardiomyopathy in human since 1990, and more than 60 mutations in human cardiac troponin subunits have been identified in dilated, hypertrophic, and restrictive forms of cardiomyopathy. In this review, we have focused on the mutations in the genes for human cardiac troponin subunits and discussed their functional consequences that might be involved in the primary mechanisms for the pathogenesis of these different types of cardiomyopathy.

Identification of novel anti-angiogenic factors by in silico functional gene screening method.

Angiogenesis, the formation of new blood vessels out of pre-existing capillaries, occurs in a variety of pathophysiological conditions, and is regulated by a balance of angiogenic activators and inhibitors. To identify novel angiogenic factors, we developed a gene screening method by combining the prediction analysis of transcription factor (TF) binding site and the chromosomal localization analysis. First, we analyzed the promoter sequences from known angiogenesis-related factors using the MATINSPECTOR program in TRANSFAC database. Interestingly, we found that the binding site of LMO2 complex is highly conserved in the promoter regions of these factors. Second, we analyzed chromosome loci based on the hypothesis that angiogenesis-related factors might be co-localized in a specific chromosomal band. We found that angiogenesis-related factors are localized in specific 14 chromosomal bands including 5q31 and 19q13 using AngioDB and LocusLink database mining. From these two approaches, we identified 32 novel candidates that have the LMO2 complex binding site in their promoter and are located on one of 14 chromosomal bands. Among them, human recombinant troponin T and spectrin markedly inhibited the neovascularization in vivo and in vitro. Collectively, we suggest that the combination of the prediction analysis of TF binding site and the chromosomal localization analysis might be a useful strategy for gene screening of angiogenesis.

Cardiac troponin T isoforms demonstrate similar effects on mechanical performance in a regulated contractile system.

Alteration of troponin T (TnT) isoform expression has been reported in human and animal models of myocardial failure. The two adult beef cardiac TnT isoforms (TnT(3) and TnT(4)) were isolated for comparative functional analysis. Thin filaments were reconstituted containing pure populations of the isoforms. The in vitro motility assay was used to directly compare the effect of the two TnT isoforms on force and unloaded shortening as a function of free calcium. We found no significant differences between the two isoforms in terms of calcium sensitivity, cooperativity, or maximal activation (velocity and force) as assessed in a fully calcium-regulated system. Activation by myosin strong binding was similar for thin filaments containing either of the two TnT isoforms. Whereas maximally activated velocity and cooperativity was depressed at pH 6.5, no difference between thin filaments containing the two isoforms was detected. From the small magnitude of the TnT isoform shifts detected in myocardial failure and the lack of significant mechanical effect detected in the motility assay, variable TnT isoform expression is unlikely to be any functional significance in heart failure.

Functional consequences of the deletion mutation deltaGlu160 in human cardiac troponin T.

To explore the functional consequences of a deletion mutation of troponin T (DeltaGlu160) found in familial hypertrophic cardiomyopathy, the mutant human cardiac troponin T, and wild-type troponins T, I, and C were expressed in Escherichia coli and directly incorporated into isolated porcine cardiac myofibrils using our previously reported troponin exchange technique. The mutant troponin T showed a slightly reduced potency in replacing the endogenous troponin complex in myofibrils and did not affect the inhibitory action of troponin I but potentiated the neutralizing action of troponin C, suggesting that the deletion of a single amino acid, Glu-160, in the strong tropomyosin-binding region affects the tropomyosin binding affinity of the entire troponin T molecule and alters the interaction between troponin I and troponin C within ternary troponin complex in the thin filament. This mutation also increased the Ca(2+) sensitivity of the myofibrillar ATPase activity, as in the case of other mutations in troponin T with clinical phenotypes of poor prognosis similar to that of Glu160. These results provide strong evidence that the increased Ca(2+) sensitivity of cardiac myofilament is a typical functional consequence of the troponin T mutation associated with a malignant form of hypertrophic cardiomyopathy.

Relationship of cardiac troponin T and procoagulant activity in unstable angina.

OBJECTIVE: The present study sought to determine the incidence of increased procoagulant activity in patients with unstable angina (UAP), and to evaluate the relationship between cardiac troponin T (cTnT) and molecular markers of hemostatic activation. Method. We studied 44 patients with UAP further classified by plasma cTnT levels. All patients received an antithrombotic therapy consisting of therapeutic doses of unfractionated heparin and acetylsalicylic acid. Quantitative levels of cTnT and plasma concentrations of fibrin monomers (FM), prothrombin fragments F1+2, thrombin antithrombin III complexes (TAT), plasminogen and alpha2-antiplasmin were sampled serially within the first 48 h. RESULTS: Increased plasma concentrations of FM were detected in 45.5% of patients and were more frequently present among those with cTnT concentrations > or =0.1 ng/ml (13 of 18 vs 7 of 26 patients, p = 0.003). In these patients, mean plasma concentrations of FM were significantly higher than in patients with cTnT <0.1 ng/ml (7.93 +/- 2.3 vs 3.12 +/- 0.6 microg/ml, p = 0.02). There was a close relationship between plasma levels of cTnT and FM (r = 0.74, p <0.004), prothrombin fragments F1+2 (r = 0.71, p = 0.046) and a trend to significance was noted for TAT (r = 0.42, p = 0.055). No significant correlation was observed with markers of the fibrinolytic system (plasminogen and alpha2-anti-plasmin). Plasma levels of cTnT > or =0.1 ng/ml identified a concomitant increase of hemostatic markers with a sensitivity, specificity and positive predictive value of 65, 79, and 72% for FM, 63, 76, and 67% for prothrombin fragments F1+2, and 58, 66, and 39% for TAT, respectively. CONCLUSIONS: In patients with UAP, cTnT identifies patients with increased procoagulant activity and is closely related to plasma levels of molecular markers of hemostatic activation. Therefore, cTnT alone or in combination with one of these markers may be helpful to identify patients requiring more potent antithrombin or antiplatelet therapy.

Roles of troponin isoforms in pH dependence of contraction in rabbit fast and slow skeletal and cardiac muscles.

Skinned fibers prepared from rabbit fast and slow skeletal and cardiac muscles showed acidotic depression of the Ca2+ sensitivity of force generation, in which the magnitude depends on muscle type in the order of cardiac>fast skeletal>slow skeletal. Using a method that displaces whole troponin-complex in myofibrils with excess troponin T, the roles of Tn subunits in the differential pH dependence of the Ca2+ sensitivity of striated muscle were investigated by exchanging endogenous troponin I and troponin C in rabbit skinned cardiac muscle fibres with all possible combinations of the corresponding isoforms expressed in rabbit fast and slow skeletal and cardiac muscles. In fibers exchanged with fast skeletal or cardiac troponin I, cardiac troponin C confers a higher sensitivity to acidic pH on the Ca2+ sensitive force generation than fast skeletal troponin C independently of the isoform of troponin I present. On the other hand, fibres exchanged with slow skeletal troponin I exhibit the highest resistance to acidic pH in combination with either isoform of troponin C. These results indicate that troponin C is a determinant of the differential pH sensitivity of fast skeletal and cardiac muscles, while troponin I is a determinant of the pH sensitivity of slow skeletal muscle.