Evaluation of a Clinical Decision Support System for the most evidence-based approach to managing perioperative anticoagulation.

STUDY OBJECTIVE: We explored the feasibility of a Clinical Decision Support System (CDSS) to guide evidence-based perioperative anticoagulation. DESIGN: Prospective randomised clinical management simulation multicentre study. SETTING: Five University and 11 general hospitals in Germany. PARTICIPANTS: We enrolled physicians (anaesthesiologist (n = 73), trauma surgeons (n = 2), unknown (n = 1)) with different professional experience. INTERVENTIONS: A CDSS based on a multiple-choice test was developed and validated at the University Hospital of Frankfurt (phase-I). The CDSS comprised European guidelines for the management of anticoagulation in cardiology, cardio-thoracic, non-cardio-thoracic surgery and anaesthesiology. Phase-II compared the efficiency of physicians in identifying evidence-based approach of managing perioperative anticoagulation. In total 168 physicians were randomised to CDSS (PERI-KOAG) or CONTROL. MEASUREMENTS: Overall mean score and association of processing time and professional experience were analysed. The multiple-choice test consists of 11 cases and two correct answers per question were required to gain 100% success rate (=22 points). MAIN RESULTS: In total 76 physicians completed the questionnaire (n = 42 PERI-KOAG; n = 34 CONTROL; attrition rate 54%). Overall mean score (max. 100% = 22 points) was significantly higher in PERI-KOAG compared to CONTROL (82 ± 15% vs. 70 ± 10%; 18 ± 3 vs. 15 ± 2 points; P = 0.0003). A longer processing time is associated with significantly increased overall mean scores in PERI-KOAG (≥33 min. 89 ± 10% (20 ± 2 points) vs. <33 min. 73 ± 15% (16 ± 3 points), P = 0.0005) but not in CONTROL (≥33 min. 74 ± 13% (16 ± 3 points) vs. <33 min. 69 ± 9% (15 ± 2 points), P = 0.11). Within PERI-KOAG, there is a tendency towards higher results within the more experienced group (>5 years), but no significant difference to less (≤5 years) experienced colleagues (87 ± 10% (19 ± 2 points) vs. 78 ± 17% (17 ± 4 points), P = 0.08). However, an association between professional experience and success rate in CONTROL has not been shown (71 ± 8% vs. 70 ± 13%, 16 ± 2 vs. 15 ± 3 points; P = 0.66). CONCLUSIONS: CDSS significantly improved the identification of evidence-based treatment approaches. A precise usage of CDSS is mandatory to maximise efficiency.

Cerebrospinal Fluid Concentrations of Meropenem and Vancomycin in Ventriculitis Patients Obtained by TDM-Guided Continuous Infusion.

Effective antibiotic therapy of cerebral infections such as meningitis or ventriculitis is hindered by low penetration into the cerebrospinal fluid (CSF). Because continuous infusion of meropenem and vancomycin and routine therapeutic drug monitoring (TDM) have been proposed to optimize antimicrobial exposure in ventriculitis patients, an individualized dosing strategy was implemented in our department. We present a retrospective analysis of meropenem and vancomycin concentrations in serum and CSF in the first nine ventriculitis patients treated with continuous infusion and TDM-guided dose optimization aiming at 20-30 mg/L. Median initial dosing was 8.8 g/24 h meropenem and 4.25 g/24 h vancomycin, respectively, resulting in median serum concentrations of 21.3 mg/L for meropenem and 24.5 mg/L for vancomycin and CSF concentrations of 3.4 mg/L for meropenem and 1.7 mg/L for vancomycin. Median CSF penetration was 15% for meropenem and 7% for vancomycin. With initial dosing, all but one patient achieved CSF concentrations above 1 mg/L. Dose adjustment according to TDM ensured sufficient CSF concentrations in all patients within 48 h of treatment. Given the limited penetration, continuous infusion of meropenem and vancomycin based on renal function and TDM-guided dose optimization appears a reasonable approach to attain sufficient CSF concentrations in ventriculitis patients.

TLR2-Dependent Reversible Oxidation of Connexin 43 at Cys260 Modifies Electrical Coupling After Experimental Myocardial Ischemia/Reperfusion.

We have shown previously that during myocardial ischemia/reperfusion (MI/R), toll-like receptor 2 (TLR2) signaling regulates connexin 43 (Cx43) subcellular localization and function and dampens arrhythmia formation. We aimed to identify sites capable of TLR2-dependent redox modification within Cx43. Post-ischemic TLR2-/- or wild-type (WT) mouse hearts were analyzed by OxICAT. Cx43 was mutated to exclude redox modification and transfected into HL-1 cardiomyocytes (CM) that were challenged with a TLR2 agonist. We identified Cys260 of Cx43 to be susceptible to reversible oxidation MI/R; TLR2-/- leads to reduced H2O2 production in post-ischemic isolated mitochondria and subsequently reduced oxidation of Cx43 at Cys260. Cx43 was dephosphorylated in WT, while phosphorylation was preserved in TLR2-/-. Mutation of Cx43 (C260A) and lentiviral transfection in HL-1 CM accelerated pacemaker activity and reduced activity after TLR2 ligand stimulation. We here provide evidence for TLR2-dependent reversible oxidation of Cx43 at Cys260, which led to decreased Cx43 phosphorylation and affected CM pacemaker frequency and intercellular communication.

Systemic TLR2 Antibody Application in Renal Ischaemia and Reperfusion Injury Decreases AKT Phosphorylation and Increases Apoptosis in the Mouse Kidney.

Acute kidney injury remains an important cause of renal dysfunction. In this context, Toll-like receptors have been demonstrated to play a critical role in the induction of innate and inflammatory responses. Among these, Toll-like receptor 2 (TLR2) is constitutively expressed in tubular epithelial cells (TECs) of the kidney and is also known to mediate ischaemia reperfusion (IR) injury. Adult male C57BL/6JRj mice were randomized into seven groups (n = 8): a non-operative control group (CTRL) and six interventional groups in which mice were subjected to a 30 min. bilateral renal ischaemia. Immediately before reperfusion, mice were treated either with saline or with TLR2 antibody (clone T2.5) and harvested after ischaemia and reperfusion for 3, 24 and 48 hr. Analysed kidney homogenates of TLR2 antibody-treated mice displayed significantly decreased levels of TLR2 protein after 3 hr of IR compared to saline-treated mice. Accordingly, the degree of AKT phosphorylation was significantly decreased after 3 hr of IR compared to saline-treated animals. TUNEL staining revealed significantly higher apoptosis rates in TLR2 antibody-treated animals compared to saline-treated mice after 3 and 24 hr of IR. Further, a positive correlation between TLR2 protein expression and phosphorylation of AKT as well as a negative correlation with the number of TUNEL-positive cells could be observed. Inhibition of TLR2 and its signalling pathway by a single application of TLR2 antibody results in reduced phosphorylation of AKT and consecutively increased apoptosis.

Takotsubo Cardiomyopathy Triggered by Venous Air Embolism During Craniotomy in the Sitting Position.

BACKGROUND: We present a case of stress-induced cardiomyopathy (Takotsubo cardiomyopathy) caused by a venous air embolism during a craniotomy performed in the sitting position. CASE DESCRIPTION: A 69-year-old woman was admitted to the neurosurgical department and scheduled for elective resection of a cerebellar metastasis in the sitting position. After craniotomy and opening of the posterior fossa, a venous air embolism was detected via transesophageal echocardiography. The patient immediately presented with cardiac decompensation with signs of takotsubo or stress-induced cardiomyopathy. CONCLUSIONS: Intensivists and anesthesiologists in the operating room and in intensive care units need to be aware of stress-induced cardiomyopathy as a probably underdiagnosed disease entity, especially as management differs significantly from other forms of cardiogenic shock. Diagnosis can be accomplished quickly by bedside echocardiography, emphasizing the need for availability of this tool and the integration of stress-induced cardiomyopathy in diagnostic algorithms in the intensive care unit.

The Role of ABO Blood Group in Cerebral Vasospasm, Associated Intracranial Hemorrhage, and Delayed Cerebral Ischemia in 470 Patients with Subarachnoid Hemorrhage.

OBJECTIVE: Rupture of an intracranial aneurysm usually presents with an acute onset and requires multidisciplinary intensive care treatment and the overall death and disability rates are high. The ABO blood type is known to play an important role in hemostasis, thrombosis, and vascular NO response. The aspect of ABO blood type in onset, clinical progress, and outcome after subarachnoid hemorrhage (SAH) is largely unexplored. We conducted this study to elucidate the association of ABO blood type with the occurrence and outcome of aneurysmal SAH. METHODS: In our retrospective study, 470 patients with aneurysmal SAH treated at our institution were included. We performed a χ2 test for comparison between blood types and World Federation of Neurosurgical Societies admission status, cerebral vasospasm, delayed infarction, associated intracerebral hemorrhage and Fisher grade for analysis for their association with SAH. RESULTS: No significant difference between blood type and the reviewed variables for SAH outcome were identified: World Federation of Neurosurgical Societies admission status (odds ratio, 1.12; 95% confidence interval [CI], 0.7-1.6; P = 0.56); SAH-associated intracerebral hemorrhage (odds ratio, 0.81; 95% CI, 0.5-1.3; P = 0.36); cerebral vasospasm (odds ratio, 1.08; 95% CI, 0.7-1.6; P = 0.71); DCI (odds ratio, 1.23; 95% CI, 0.8-1.8; P = 0.30); Fisher grade (odds ratio, 1.13; 95% CI, 0.7-1.6; P = 0.19). CONCLUSIONS: Although a possible relationship between the ABO blood group and the clinical course of patients with SAH was hypothesized, our study showed no significant influence of patient's ABO blood type on cerebral vasospasm onset, SAH-associated intracerebral hemorrhage, or delayed infarction.

An Essential Role for SHARPIN in the Regulation of Caspase 1 Activity in Sepsis.

Sepsis is burdened by high mortality due to uncontrolled inflammatory response to pathogens. Increased caspase 1 activation causing maturation of IL1ß/18 remains a therapeutic challenge in sepsis. SHARPIN (shank-associated regulator of G-protein signaling homology domain-interacting protein), a component of the LUBAC (linear ubiquitin chain-assembly complex), regulates inflammation, with unknown effects on caspase 1 activation. Mice lacking Casp1, Casp11, or both in a Sharpin-deficient background were generated, exposed to lipopolysaccharide-induced endotoxemia, and injected with caspase 1 inhibitor. We monitored survival, Il1ß/18, and caspase 1/11 levels in plasma and organs and deciphered mechanisms of SHARPIN-dependent caspase 1 inhibition. A correlation between LUBAC and active caspase 1 was found in blood mononuclear cells from septic patients. SHARPIN bound caspase 1 and disrupted p20/p10 dimer formation, the last step of caspase 1 processing, thereby inhibiting enzyme activation and maturation of IL1ß/18 in a LUBAC-independent manner. In septic patients, LUBAC-independent decline in SHARPIN correlated with enhancement of active caspase 1 in circulating mononuclear cells. Septic Sharpin-deficient mice displayed enrichment in mature Il1ß/18 and active caspase 1, and shortened survival. Inhibition of caspase 1 reduced levels of Il1ß/18 and splenic cell death, and prolonged survival in septic Sharpin-deficient mice. Our findings identify SHARPIN as a potent in vivo caspase 1 inhibitor and propose the caspase 1-SHARPIN interaction as a target in sepsis.

Dislocated Pacemaker Electrode Simulating Focal Epileptic State in a Patient with Subdural Hematoma-Case Report and Review of the Literature.

BACKGROUND: Due to demographic changes, the number of patients with traumatic brain injury carrying a cardiac resynchronization therapy device is increasing. One of the common complications of subdural hematoma (SDH) is epilepsy, whereas one of the most frequent early complications after cardiac resynchronization therapy device implantation is lead dislocation. The latter might then cause unintended skeletal muscle stimulation that might be misinterpreted in seizure-prone patients. CASE DESCRIPTION: An 86-year-old female patient with an initially conservatively treated SDH on the right side presented with a tonic muscle contraction in her left arm 2 weeks after the trauma not responding to antiepileptic therapy. A computed tomography scan revealed residual hematoma on the right side with regular, time-dependent resorption. The muscle contraction was misdiagnosed as a focal epileptic state leading to evacuation of the chronic SDH. Additionally, routine postoperative chest radiographs were performed. Postoperatively, the tonic muscle contraction in her arm persisted. Chest radiographs revealed a dislocation of the left ventricular electrode, which appeared retracted into the left subclavian vein, next to the plexus brachialis. After deactivating the electrode, the alleged focal state ceased. CONCLUSIONS: In case of refractory treatment of epilepsy, dislocation of pacemaker electrodes is a, most certainly, rare but possible differential diagnosis. Confirmation of electrode position and function is easily and quickly feasible and will help prevent futile seizure-directed therapy.

Attenuation of myocardial injury by HMGB1 blockade during ischemia/reperfusion is toll-like receptor 2-dependent.

Genetic or pharmacological ablation of toll-like receptor 2 (TLR2) protects against myocardial ischemia/reperfusion injury (MI/R). However, the endogenous ligand responsible for TLR2 activation has not yet been detected. The objective of this study was to identify HMGB1 as an activator of TLR2 signalling during MI/R. C57BL/6 wild-type (WT) or TLR2(-/-)-mice were injected with vehicle, HMGB1, or HMGB1 BoxA one hour before myocardial ischemia (30 min) and reperfusion (24 hrs). Infarct size, cardiac troponin T, leukocyte infiltration, HMGB1 release, TLR4-, TLR9-, and RAGE-expression were quantified. HMGB1 plasma levels were measured in patients undergoing coronary artery bypass graft (CABG) surgery. HMGB1 antagonist BoxA reduced cardiomyocyte necrosis during MI/R in WT mice, accompanied by reduced leukocyte infiltration. Injection of HMGB1 did, however, not increase infarct size in WT animals. In TLR2(-/-)-hearts, neither BoxA nor HMGB1 affected infarct size. No differences in RAGE and TLR9 expression could be detected, while TLR2(-/-)-mice display increased TLR4 and HMGB1 expression. Plasma levels of HMGB1 were increased MI/R in TLR2(-/-)-mice after CABG surgery in patients carrying a TLR2 polymorphism (Arg753Gln). We here provide evidence that absence of TLR2 signalling abrogates infarct-sparing effects of HMGB1 blockade.

Priming with synthetic oligonucleotides attenuates pressure overload-induced inflammation and cardiac hypertrophy in mice.

AIMS: Inflammation and Toll-like receptor (TLR) signalling have been linked to the development of cardiac hypertrophy following transverse aortic constriction (TAC). In the present study, we investigated whether pre-treatment with the synthetic TLR9 ligands 1668-thioate or 1612-thioate modulates the progression of TAC-induced cardiac inflammation and hypertrophy. METHODS AND RESULTS: C57BL/6N-mice were pre-treated with 1668-thioate, 1612-thioate (0.25 nmol/g, i.p.), or phosphate-buffered saline 16 h prior to TAC or sham surgery. Heart-weight/body-weight ratio (HW/BW), cardiomyocyte cell size, cellular macrophage accumulation, myofibroblast differentiation, and collagen deposition were investigated for up to 28 days. Cardiac function was monitored using a pressure-volume catheter and M-mode echocardiography. Inflammatory gene expression in the heart was analysed via gene array, while the time course of mRNA expression of key inflammatory mediators was assessed via RT-qPCR. TAC increased the HW/BW ratio and cardiomyocyte cell size and induced macrophage accumulation, myofibroblast differentiation, and collagen deposition. These changes were accompanied by cardiac inflammation and a significant loss of left ventricular function. Pre-treatment with cytosine-phosphate-guanine (CpG)-containing 1668-thioate attenuated the inflammatory response, the progression of cardiac hypertrophy, and cardiac remodelling, which resulted in a prolonged preservation of left ventricular function. These changes were induced to a smaller extent by the use of the non-CG-containing oligodeoxynucleotide 1612-thioate. CONCLUSION: Pre-treatment with 1668-thioate attenuated cardiac hypertrophy following pressure overload, possibly by modifying the hypertrophy-induced inflammatory response, thereby reducing cardiac growth and fibrosis as well as delaying loss of cardiac function.

In vivo electrophysiological characterization of TASK-1 deficient mice.

BACKGROUND/AIMS: TASK-1 is a potassium channel predominantly expressed in heart and brain. We have previously shown that anesthetized TASK-1(-/-)mice have prolonged QT intervals in surface electrocardiograms (ECGs). In addition, heart rate variability quantified by time and frequency domain parameters was significantly altered in TASK-1(-/-) mice with a sympathetic preponderance. Aims of the present study were the analysis of QT intervals by telemetric ECGs, to determine potential influences of anesthesia and ß-adrenergic stimulation on repolarization in surface ECGs, to investigate in vivo electrophysiological parameters by intracardiac electrical stimulation and to quantify heart rate turbulence after ischemia/reperfusion or ventricular pacing in TASK-1(+/+) and TASK-1(-/-) mice. METHODS: Rate corrected QT intervals (QTc) were recorded in conscious mice by telemetry and in surface ECGs following administration of various anesthetics (tribromoethanol (Avertin(®)), pentobarbital and isoflurane). TASK-1(+/+) and TASK-1(-/-) mice were characterized by programmed electrical stimulation using an intracardiac octapolar catheter. The baroreceptor reflex was analyzed by heart rate turbulence (turbulence onset and slope) after ischemia/reperfusion and by stimulated premature ventricular contractions. RESULTS: Telemetric and surface ECGs in mice sedated with Avertin(®) and pentobarbital, showed a significantly lengthened rate corrected QT interval in TASK-1(-/-) mice (telemetry: TASK-1(+/+) 43±3ms vs. TASK-1(-/-) 49±5ms, n=6, p<0.05; Avertin(®): TASK-1(+/+) 36±8ms vs. TASK-1(-/-) 48±4ms, n=13/16, p<0.0001). The prolongation of the QT interval was most pronounced at lower heart rates. Isoflurane, known for its stimulatory effects on the TASK channel family, attenuated the rate corrected QT interval prolongation in TASK-1(-/-)mice. Intracardiac electrical stimulation revealed normal values for electrical conduction and refractoriness. No significant arrhythmias after atrial and ventricular burst stimulation were induced before and after adrenergic challenge in both genotypes. Turbulence onset after premature ventricular contraction was significantly altered in TASK-1(-/-) mice. CONCLUSION: TASK-1(-/-) mice exhibit a phenotype of QT prolongation, which distinct relation to heart rate. TASK-1 deficiency does neither alter key electrophysiological parameters nor increases atrial/ventricular vulnerability after electrical stimulation. The heart rate response after premature ventricular contractions is significantly abolished indicating a diminished baroreceptor reflex in TASK-1(-/-) mice.

Systemic inflammation after aortic cross clamping is influenced by Toll-like receptor 2 preconditioning and deficiency.

BACKGROUND: The perioperative morbidity and mortality of abdominal aortic aneurysm repair is linked to systemic inflammation. Important triggers of the latter are Toll-like receptors (TLRs), which play a central role in innate immunity. Ischemia/reperfusion (I/R) injury can be influenced by either TLR stimulation before I/R (preconditioning) or TLR dysfunction (deficiency or polymorphism). The influence of TLR2 stimulation or deficiency on systemic cytokine release and organ damage after aortic cross clamping has not been evaluated yet. METHODS: Wild type (WT) and TLR2-deficient mice were subjected to 1 h ischemia and 2 or 4 h reperfusion of the infrarenal aorta. One group of WT mice was preconditioned with the synthetic TLR2 agonist Pam(3)Cys-Ser-Lys(4) (Pam(3)CSK(4)). Sham-operated animals without I/R served as controls. Plasma levels of interleukin (IL)-1ß, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12, granulocyte macrophage-colony stimulating factor, tumor necrosis factor-α, alanine transaminase (ALT), aspartate transaminase (AST), lactate dehydrogenase (LDH), and creatinine were measured. RESULTS: I/R injury caused by transient clamping of the infrarenal aorta led to a time-dependent increase of all measured cytokines except IL-4, IL-5, and granulocyte macrophage-colony stimulating factor. This was accompanied by elevated markers of organ damage (ALT, AST, and LDH) except creatinine. Preconditioning with Pam(3)CSK(4) led to lower plasma concentrations of all cytokines, with the exception of anti-inflammatory IL-10 which was significantly upregulated. Furthermore, ALT, AST, and LDH plasma concentrations were lower in the preconditioning group. TLR2-deficient mice similarly showed reduced signs of systemic inflammation and organ damage, although less distinctive. IL-2, IL-6, IL-12, ALT, and LDH were time dependently lower compared with WT mice. IL-10 concentration was higher in TLR2-deficient mice compared with WT. CONCLUSIONS: Both, preconditioning via TLR2 and TLR2 deficiency, ameliorate systemic inflammation and organ damage during I/R injury caused by clamping of the infrarenal aorta. Compared with untreated WT animals, Pam(3)CSK(4) preconditioned and TLR2-deficient mice showed lower concentrations of pro-inflammatory cytokines, whereas anti-inflammatory IL-10 was elevated in both groups. This was accompanied by reduced organ dysfunction parameters.

Akt or phosphoinositide-3-kinase inhibition reverses cardio-protection in Toll-like receptor 2 deficient mice.

AIM: Absence or inhibition of Toll-like receptor 2 (TLR2) signalling during murine myocardial ischaemia/reperfusion (MI/R) decreases myocardial necrosis and inflammation, thereby ameliorating cardiac dysfunction and improving survival. In the present study, we provide evidence for the involvement of the phosphoinositide-3-kinase/Akt pathway in TLR2-dependent reperfusion injury. METHODS: Adult male wild-type (WT) and TLR2(-/-) mice were subjected to myocardial ischaemia (30min) and reperfusion (4h). Animals were treated with phosphoinositide-3-kinase inhibitor wortmannin, Akt inhibitor V (triciribine), or vehicle 1h prior to MI/R. Protein expression levels of Akt1 and phosphoinositide-3-kinase and their respective phosphorylated forms were determined by Western blot analysis. Myocardial necrosis was quantified after staining with the tetrazolium method and by troponin T plasma levels. RESULTS: TLR2(-/-) mice displayed significantly increased Akt and phospho-Akt levels compared to WT mice, whilst no significant difference in phosphoinositide-3-kinase expression and phosphorylation could be observed. TLR2(-/-) mice also showed a blunted myocardial necrosis, the extent of which inversely correlated with Akt expression and degree of phosphorylation. Pharmacological inhibition of both, phosphoinositide-3-kinase or Akt, reversed the cardioprotection observed in TLR2(-/-) mice, whilst no effect could be observed in WT mice. CONCLUSION: Akt is an important mediator of cardioprotection in TLR2(-/-) animals during MI/R. The effect is, however, likely mediated by its genomic overexpression in the heart of TLR2(-/-) animals whilst Akt activation by phosphoinositide-3-kinase is unaltered.

Measure for measure-determination of infarct size in murine models of myocardial ischemia and reperfusion: a systematic review.

Myocardial ischemia/reperfusion injury (MI/R) is one of the most prominent topics of contemporary research. The frequent failure of potential therapeutic drugs and interventions to transfer to clinical practice demonstrates the limitations in using experimental animal models. Because a variety of transgenic animals are readily available in mice, researchers in recent years have made use of murine models rather than of larger animal models for experimental MI/R. This review focuses on in vivo and ex vivo murine models of MI/R and aims to characterize the source of our mechanistic understanding in mice. A systematic review of the literature demonstrated that there is great diversity among ex vivo (Langendorff) and in vivo models of MI/R.

Left ventricular dilation in toll-like receptor 2 deficient mice after myocardial ischemia/reperfusion through defective scar formation.

Restoration of myocardial blood flow after ischemia triggers an inflammatory response involving toll-like receptors (TLRs). TLR2(-/-)-mice show short-term advantages upon reperfusion injury as compared with WT controls. Accordingly, it has been shown that transient TLR2-blockade prior to reperfusion is associated with improved left-ventricular performance after myocardial scar formation. We present here adverse myocardial remodeling due to a chronic lack of TLR2 expression. Myocardial ischemia/reperfusion (MI/R) was surgically induced in C3HeN-mice by ligation of the left anterior descending coronary artery for 20 min, followed by 24 h or 28 days of reperfusion. TLR2(-/-)-mice and TLR2-Ab treated (T2.5) WT-mice displayed a reduction of infarct size, plasma troponin T concentrations, and leukocyte infiltration as compared with untreated controls after 24 h of reperfusion. After 28 days, however, magnetic resonance imaging revealed a marked left ventricular dilation in TLR2(-/-)-animals, which was associated with pronounced matrix remodeling characterized by reduced collagen and decorin density in the infarct scar. Our data show adverse effects on myocardial remodeling in TLR2(-/-)-mice. Although interception with TLR2 signaling is a promising concept for the prevention of reperfusion injury after myocardial ischemia, these data give cause for serious concern with respect to the time-point and duration of the potential treatment.

Functional role of TASK-1 in the heart: studies in TASK-1-deficient mice show prolonged cardiac repolarization and reduced heart rate variability.

TASK-1, a member of the recently identified K2P channel family, is mainly expressed in the heart and the nervous system. TASK-1 is regulated by several physiological and pathological conditions and functions as a background potassium channel. However, there are limited data concerning the significance of TASK-1 in cardiac physiology. We studied the functional role of TASK-1 in the heart by cardiac phenotyping the TASK-1-deficient mouse (TASK-1(-/-)). TASK-1 was predominantly expressed in the ventricles of control animals. Real-time PCR and immunoblot demonstrated that the expression of seven other K2P channels was unchanged in TASK-1(-/-) mice. No structural or functional abnormalities were found by histology and echocardiography. Electrophysiological studies recording monophasic action potentials (MAPs) showed a significant prolongation of action potential duration in spontaneously beating and atrially paced hearts, respectively. Surface ECGs of TASK-1(-/-) mice revealed a significant prolongation of the rate corrected QT interval. Telemetric ECG recordings for 24 h, during physical and pharmacological stress testing and after ischemia/reperfusion injury did not result in a higher incidence of arrhythmias. Infarct size was comparable in both genotypes. However, TASK-1(-/-) mice had a higher mean heart rate and significantly reduced heart rate variability (HRV). Time and frequency domain measurements as well as baroreceptor reflex testing revealed a sympathovagal imbalance with a shift to an increase in sympathetic influence in TASK-1(-/-) mice. In conclusion, TASK-1 plays a functional role in the repolarization of the cardiac action potential in vivo and contributes to the maintenance of HRV.

Toll-like receptor 2 signaling triggers fatal arrhythmias upon myocardial ischemia-reperfusion.

OBJECTIVE: Restoration of myocardial blood flow after ischemia triggers an inflammatory response involving toll-like receptors. Toll-like receptor 2 deficiency is associated with a reduced infarct size after myocardial ischemia and reperfusion. Because a marked mortality was observed in C3HeN wild-type mice, which was absent in TLR2 mice, we tested whether cardiac arrhythmias are the underlying pathology and aimed to elucidate how toll-like receptor 2 ligation might prevent lethal arrhythmias. DESIGN: Experimental animal model. SETTING: University hospital research laboratory. SUBJECTS: Male C3HeN mice. INTERVENTIONS: Myocardial ischemia and reperfusion was surgically induced by ligation of the left anterior descending coronary artery for 20 mins followed by 24 hrs of reperfusion. Electrocardiography was continuously recorded during the observation period through an implantable telemetry transmitter to detect cardiac arrhythmias during reperfusion. MEASUREMENTS AND MAIN RESULTS: Toll-like receptor 2 expression was associated with a 51% mortality rate (23 of 45 mice died) after myocardial ischemia and reperfusion. Absence of toll-like receptor 2 improved survival toward 100% (17 of 17 mice survived). Electrocardiography diagnostics in conscious animals and histologic analysis revealed that absence of toll-like receptor 2 signaling prevented the formation of pathologic heart rate turbulence after myocardial ischemia and reperfusion and modulated the density of connexin 43-positive gap junctions in the ischemic area compared with wild-type hearts, indicating arrhythmia as the cause underlying the observed mortality. CONCLUSIONS: The results presented here indicate toll-like receptor 2 as a novel target for the prevention of lethal arrhythmic complications after myocardial ischemia and reperfusion.

Therapeutic injection of PARP inhibitor INO-1001 preserves cardiac function in porcine myocardial ischemia and reperfusion without reducing infarct size.

Pharmacological protection from myocardial reperfusion injury, despite plenty of approaches, has still not been realized in humans. We studied the putative infarct size (IS)-sparing capacity of poly(ADP-ribose)polymerase inhibitor, INO-1001, and focused on cardiac functional recovery during reperfusion. Male farm-bred Landrace pigs were subjected to 1-h left anterior descending coronary artery occlusion followed by 3 h of reperfusion (control). Infarct size was determined by triphenyltetrazolium chloride/Evans blue staining. Plasma markers of myocardial injury (troponin T, creatine kinase, lactate dehydrogenase) were determined upon protocol completion. Cardiac function was continuously assessed via pulmonary and femoral artery catheters. INO-1001 (1 mg/kg) was administered upon reperfusion in the treatment group. As a positive control, untreated pigs were subjected to ischemic preconditioning (10-min left anterior descending coronary artery occlusion followed by 15-min reperfusion before the intervention). Ischemic preconditioning reduced myocardial damage reflected by a smaller IS and lower plasma markers of myocardial injury. INO-1001 did not reduce IS but significantly improved functional recovery (increased stroke volume, cardiac index, and mixed venous oxygen saturation) during reperfusion compared with vehicle-treated control and ischemic preconditioning. Although we could not confirm the IS-sparing capacities of poly(ADP-ribose)polymerase inhibitor, INO-1001, the drug holds the potential of hemodynamic improvement during reperfusion.