How to protect the heart in septic shock: a hypothesis on the pathophysiology and treatment of septic heart failure

Role of M6a Methylation in Myocardial Ischemia-Reperfusion Injury and Doxorubicin-Induced Cardiotoxicity

Cardiovascular disease remains the leading cause of death worldwide, with acute myocardial infarction and anticancer drug-induced cardiotoxicity being the significant factors. The most effective treatment for acute myocardial infarction is rapid restoration of coronary blood flow by thrombolytic therapy or percutaneous coronary intervention. However, myocardial ischemia-reperfusion injury (MI/RI) after reperfusion therapy is common in acute myocardial infarction, thus affecting the prognosis of patients with acute myocardial infarction. There is no effective treatment for MI/RI. Anthracyclines such as Doxorubicin (DOX) have limited clinical use due to their cardiotoxicity, and the mechanism of DOX-induced cardiac injury is complex and not yet fully understood. N6-methyladenosine (m6A) plays a crucial role in many biological processes. Emerging evidence suggests that m6A methylation plays a critical regulatory role in MI/RI and DOX-induced cardiotoxicity (DIC), suggesting that m6A may serve as a novel biomarker and therapeutic target for MI/RI and DIC. M6A methylation may mediate the pathophysiological processes of MI/RI and DIC by regulating cellular autophagy, apoptosis, oxidative stress, and inflammatory response. In this paper, we first focus on the relationship between m6A methylation and MI/RI, then further elucidate that m6A methylation may mediate the pathophysiological process of MI/RI through the regulation of cellular autophagy, apoptosis, oxidative stress, and inflammatory response. Finally, briefly outline the roles played by m6A in DIC, which will provide a new methodology and direction for the research and treatment of MI/RI and DIC.

Inflammatory mechanisms and intervention strategies for sepsis-induced myocardial dysfunction

Sepsis-induced myocardial dysfunction (SIMD) is the leading cause of death in patients with sepsis in the intensive care units. The main manifestations of SIMD are systolic and diastolic dysfunctions of the myocardium. Despite our initial understanding of the SIMD over the past three decades, the incidence and mortality of SIMD remain high. This may be attributed to the large degree of heterogeneity among the initiating factors, disease processes, and host states involved in SIMD. Previously, organ dysfunction caused by sepsis was thought to be an impairment brought about by an excessive inflammatory response. However, many recent studies have shown that SIMD is a consequence of a combination of factors shaped by the inflammatory responses between the pathogen and the host. In this article, we review the mechanisms of the inflammatory responses and potential novel therapeutic strategies in SIMD.

Takotsubo syndrome and dialysis: an uncommon association?

This review was performed to investigate the association between treatment with dialysis and Takotsubo syndrome in patients with end-stage renal disease. We systematically explored the PubMed database using the search terms "Takotsubo cardiomyopathy" and/or "stress-induced cardiomyopathy" and/or "Takotsubo syndrome" in combination with "dialysis" and "uremia." Of 3630 articles found, 8 articles reporting 10 cases were selected for analysis. Most patients were women, and their age ranged from 51 to 84 years. Diabetes mellitus and hypertension were diagnosed in 40% of patients, and glomerular disease was diagnosed in 30%. One only patient was treated with peritoneal dialysis; all others were treated with hemodialysis. The outcome was unfavorable in only one patient. An association between Takotsubo syndrome and dialysis is uncommon, but not negligible, and comorbidities play a major role in determining the clinical outcome.

Addressing the Global Burden of Trauma in Major Surgery

Despite a technically perfect procedure, surgical stress can determine the success or failure of an operation. Surgical trauma is often referred to as the "neglected step-child" of global health in terms of patient numbers, mortality, morbidity, and costs. A staggering 234 million major surgeries are performed every year, and depending upon country and institution, up to 4% of patients will die before leaving hospital, up to 15% will have serious post-operative morbidity, and 5-15% will be readmitted within 30 days. These percentages equate to around 1000 deaths and 4000 major complications every hour, and it has been estimated that 50% may be preventable. New frontline drugs are urgently required to make major surgery safer for the patient and more predictable for the surgeon. We review the basic physiology of the stress response from neuroendocrine to genomic systems, and discuss the paucity of clinical data supporting the use of statins, beta-adrenergic blockers and calcium-channel blockers. Since cardiac-related complications are the most common, particularly in the elderly, a key strategy would be to improve ventricular-arterial coupling to safeguard the endothelium and maintain tissue oxygenation. Reduced O2 supply is associated with glycocalyx shedding, decreased endothelial barrier function, fluid leakage, inflammation, and coagulopathy. A healthy endothelium may prevent these "secondary hit" complications, including possibly immunosuppression. Thus, the four pillars of whole body resynchronization during surgical trauma, and targets for new therapies, are: (1) the CNS, (2) the heart, (3) arterial supply and venous return functions, and (4) the endothelium. This is termed the Central-Cardio-Vascular-Endothelium (CCVE) coupling hypothesis. Since similar sterile injury cascades exist in critical illness, accidental trauma, hemorrhage, cardiac arrest, infection and burns, new drugs that improve CCVE coupling may find wide utility in civilian and military medicine.

β₁-adrenoceptor stimulation promotes LPS-induced cardiomyocyte apoptosis through activating PKA and enhancing CaMKII and IκBα phosphorylation

INTRODUCTION

Caspase activation and cardiomyocyte apoptosis have been implicated in lipopolysaccharide (LPS)-induced cardiac contractile dysfunction. We have recently demonstrated that β1-adrenoceptor (AR) activation by endogenous norepinephrine contributes to cardiomyocyte apoptosis in endotoxemic mice. Here, we further investigated the molecular mechanisms for the enhancing effect of β₁-AR activation on LPS-induced cardiomyocyte apoptosis.

METHODS

The adult mouse ventricular myocytes were exposed to LPS, dobutamine, protein kinase A (PKA) inhibitor or/and nifedipine, an L-type Ca(2+) channel blocker. Male BALB/c mice were treated with LPS or/ and β₁-AR antagonist, atenolol. Cardiomyocyte apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeling (TUNEL) assay and apoptosis-associated molecules were detected.

RESULTS

LPS induced apoptosis in adult mouse ventricular myocytes, dobutamine (DOB), a β₁-AR agonist, promoted apoptosis, caspase-8, 9 and 3 activation and increased cytosolic Ca(2+) concentration in LPS-challenged cardiomyocytes. DOB also up-regulated TNF-α expression, decreased Bcl-2 levels, promoted Bax translocation to mitochondria, mitochondrial membrane potential loss and cytochrome c release as well as IκBα, p38 MAPK, JNK and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) phosphorylation in LPS-treated cardiomyocytes. PKA inhibitor abolished the effects of DOB on caspase-9 activation, Bcl-2 levels as well as JNK and p38 MAPK phosphorylation, but not on IκBα phosphorylation, TNF-α expression and caspase-8 activation in LPS-stimulated cardiomyocytes. Pretreatment with nifedipine not only significantly blocked the enhancing effects of DOB on LPS-induced elevation in cytosolic Ca(2+) concentration and CaMKII phosphorylation in cardiomyocytes, but also partly reversed the effects of DOB on caspase-9 and caspase-3/7 activities in LPS-treated cardiomyocytes. Furthermore, atenolol suppressed TNF-α expression, JNK, p38 MAPK and CaMKII phosphorylation, increased Bcl-2 expression, and inhibited cytochrome c release and cardiomyocyte apoptosis in the myocardium of endotoxemic mice.

CONCLUSIONS

β1-AR activation promotes LPS-induced apoptosis through activating PKA, increasing CaMKII phosphorylation as well as enhancing IκBα phosphorylation and TNF-α expression in cardiomyocytes.

Transport stress induces apoptosis in rat myocardial tissue via activation of the mitogen-activated protein kinase signaling pathways

The present study aimed to elucidate the mechanism of myocardial damage induced by simulated transport stress. Sprague-Dawley rats were subjected to 35 °C and 60 rpm (0.1×g rcf) on a constant temperature shaker. The blood samples were prepared for detection of epinephrine (E), norepinephrine (NE), atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and serum cardiac troponin T (cTNT); myocardium samples were prepared for morphological examination and signaling protein quantitative. The result showed that plasma norepinephrine (NE) and epinephrine (E) concentrations increased in all stressed groups (P < 0.01). Levels of serum cardiac troponin T (cTNT) were elevated in both the S2d (P < 0.05) and S3d groups (P < 0.01). The concentration of plasma BNP was increased significantly in S3d group (P < 0.05); the difference in ANP was not remarkable. Morphological observation demonstrated obvious microstructure and ultrastructure damage after simulated transport stress. There was also a significant increase in the number of TUNEL-positive cardiomyocytes in stressed hearts. Western blot analysis found that the mitogen-activated protein kinase (MAPK) pathways were activated by strengthening phosphorylation of ASK-1, JNK, P38 and ERK in rat myocardial tissue after simulated transport stress (P < 0.05, P < 0.01). In addition, the ratio of pro-apoptotic Bax and anti-apoptotic Bcl-2 proteins was increased in stressed rats (P < 0.01), and the amount of cleaved-caspase3 increased in all stressed rats (P < 0.01). The expression of cleaved-caspase9 protein was also elevated in S2d and S3d groups (P < 0.01). Consequently simulated transport stress induced obvious myocardial damage, which may be attributed to the activation of caspase 9-mediated mitochondrial apoptotic pathway and MAPK pathways.

Sepsis, venous return, and teleology

An understanding of heart-circulation interaction is crucial to our ability to guide our patients through an episode of septic shock. Our knowledge has advanced greatly in the last one hundred years. There are, however, certain empirical phenomena that may lead us to question the wisdom of our prevailing treatment algorithm. Three extreme but iatrogenically possible haemodynamic states exist. Firstly, inappropriately low venous return; secondly, overzealous arteriolar constriction; and finally, misguided inotropy and chronotropy. Following an unsuccessful fluid challenge, it would be logical to first set the venous tone, then set the cardiac rate and contractility, and finally set the peripheral vascular resistance. It is hypothesized that a combination of dihydroergotamine, milrinone and esmolol should be superior to a combination of noradrenaline and dobutamine for surviving sepsis.

Sepsis-induced myocardial depression and takotsubo syndrome

Abstract Background and objectives: Myocardial depression in the setting of sepsis and septic shock is common and has been recognized for a long time. The aim of this study is to find out an association and causal link between sepsis and takotsubo syndrome (TS).

METHODS

Fifteen cases of TS were studied. Critical review of the literature dealing with sepsis and myocardial depression was done Results: Fifteen cases of sepsis-induced TS are described. Fifty-three per cent of the patients were men. The ages ranged from 39 to 76 years (mean age 60 years). Two-thirds of the patients had ST-elevation myocardial infarction ECG changes. Complications occurred in 80% of the patients. No specific types of sepsis or micro-organisms were associated with the development of TS. Critical review of the sepsis-induced myocardial depression shows that the left ventricular dysfunction, which is reversible within one-to-two weeks, is characterized by segmental ventricular dysfunction, and involvement of the right ventricle in one fourth of cases. These features are also consistent with TS.

CONCLUSIONS

Sepsis triggers TS, which may be the cause of the majority of cases of sepsis-induced myocardial depression. Acute cardiac sympathetic disruption with noradrenaline spill-over may be the cause of sepsis-induced TS.

Takotsubo Cardiomyopathy and Acute Infectious Diseases

Takotsubo cardiomyopathy (TTC), also defined as “stress cardiomyopathy,” is characterized by a systolic dysfunction localized in the apical and medial left ventricles. Takotsubo cardiomyopathy is more prevalent in females and it is usually related to an event triggered by physical or emotional stress. We systematically explored PubMed and Embase medical information source to identify case reports showing association between infection and TTC. For each kind of infection, we collected a set of data, including pathogen, site of infection, clinical outcome, patient age and sex, and author and year of publication. We found 26 articles dealing with 27 case reports (74% women). The mean age was 61.4 ± 13.7 years and bacterial infections were more frequent (n = 23, 85.2%). In 14 cases, there was a culture-based definition of the bacterial strain: gram+ in 8 cases (57.1%) and gram− in 6 cases (42.9%). Clinical outcome was always favorable.

Effect of induced mild hypothermia on two pro-inflammatory cytokines and oxidative parameters during experimental acute sepsis

This study aimed to determine the effect of induced mild hypothermia (34°C) on the production of two cytokines (interleukin (IL-6) and tumor necrosis factor (TNF)alpha) and reactive nitrogen and oxygen species in plasma and the heart of acutely septic rats. After anesthesia and in conditions of normothermia (38°C) or mild hypothermia (34°C), acute sepsis was induced by cecal ligation and perforation. For each temperature three groups were formed: (1) baseline (blood sample collected at T0 hour), (2) sham (blood sample at T4 hours) and (3) septic (blood sample at T4 hours). At either temperature sepsis induced a significant increase in plasma IL-6, TNF-alpha and HO• concentration, compared with the sham groups (P≤0.016). Compared with the normothermic septic group, septic rats exposed to mild hypothermia showed a mild decrease in TNF-alpha concentration (104±50 pg/ml vs. 215±114 pg/ml; P>0.05) and a significant decrease in IL-6 (1131±402 pg/ml vs. 2494±691 pg/ml, P=0.038). At either temperature sepsis induced no enhancement within the heart of lipoperoxidation (malondialdehyde content) or antioxidant activities (superoxide dismutase and catalase). In conclusion, during acute sepsis, induced mild hypothermia appears to reduce some pro-inflammatory and oxidative responses. This may, in part, explain the beneficial effect of hypothermia on survival duration of septic rats.

Histologic pathologies of the myocardium in septic shock: a prospective observational study

Myocardial depression in septic shock is well known, but its pathophysiological genesis is incompletely understood. To assess the incidence and extent of stress-induced histologic myocardial alterations in septic shock, a prospective, observational, combined clinical and postmortem study was conducted, and 20 patients dying from septic shock were included. Exclusion criteria were younger than 18 years, pregnancy, open heart surgery or cardiopulmonary resuscitation, acute neurologic diseases, pheochromocytoma, and forensic autopsy. A systematic macropathologic evaluation was performed. Nine predefined heart sections were histologically screened for myocytolysis, interstitial fibrosis, contraction band necrosis, mononuclear infiltrates, interstitial edema, and tissue hemorrhage. Stress-induced pathologies were found in 90% to 100% of patients in all heart sections (myocytolysis, 100%; interstitial fibrosis, 100%; contraction band necrosis, 95%; mononuclear infiltrates, 90%; interstitial edema, 90%; tissue hemorrhage, 30%). The incidence and extent of contraction band necrosis, mononuclear infiltrates, and myocytolysis did not differ between sexes; patients with or without chronic β-blocker, calcium antagonist, and/or statin premedication; or between the binary use of different catecholamine agents (all comparisons P > 0.05). The maximum epinephrine dose correlated with the overall extent of mononuclear infiltrates (Spearman-Rho, r = 0.704; P = 0.05) and myocytolysis (Spearman-Rho, r = 0.933; P = 0.001). Maximum norepinephrine doses correlated with the extent of mononuclear infiltrates in the left ventricular anterior wall (Spearman-Rho, r = 0.519; P = 0.02). The total duration of catecholamine therapy was correlated with the extent of mononuclear infiltrates in the apex (Spearman-Rho, r = 0.571; P = 0.009) and right atrium (Spearman-Rho, r = 0.535; P = 0.02). In conclusion, our results suggest that histologic lesions potentially indicative of stress-induced cardiotoxicity can be observed in most patients dying from septic shock.

Calcium Channel Blockers as Initial Therapeutic Agents in Hypertension

Blood pressure (BP) control is central to health promotion and maintenance across the health care continuum. Optimal control has been associated with improved microvascular end organ outcomes, reduced morbidity and mortality, and improved quality of life. Calcium channel blockers (CCBs) are a frequently utilized first-line antihypertensive agent, either as a monotherapy or in combination, as advocated by the 2003 Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC VII). However, despite their ability to achieve BP parameters comparable to alternative agents, CCBs may be inducing heart failure (HF) pathology by a mechanism other than the well-known negative inotropic effects of nondihydropyridine CCBs and thus may be responsible for more incident HF than was previously thought. Review of current literature indicates that there is a strong association between all types of CCBs and incident HF, that this association is found in persons with and without preexisting myocardial dysfunction, that BP measurement alone is an insufficient measure of end organ preservation with CCB use, and that CCB-induced HF is more problematic with comorbid coronary disease, renal disease, and diabetes mellitus. Furthermore, current research suggests that these outcomes are a result of CCB-induced neurohormonal sympathetic activation, sustained CCB-generated nitric oxide production leading to inflammation and tissue destruction, and/or increased systemic calcification secondary to concurrent calcium supplementation. These findings suggest the pressing need for reevaluation of CCBs as first-line agents in treating hypertension and for possible revision of JNC VII hypertension guidelines.

Evaluation of L-lactate and cardiac troponin I in horses undergoing emergency abdominal surgery

OBJECTIVE

To evaluate changes in plasma cardiac troponin I (cTnI) and L-lactate (LLt) as prognostic indicators in horses undergoing emergency abdominal surgery.

DESIGN

Prospective observational study.

SETTING

Veterinary teaching hospital.

ANIMALS

Thirty-four horses undergoing emergency abdominal surgery.

INTERVENTIONS

Serial blood sampling during various times during hospitalization (hospital admission, and 12, 24, 48, and 72 h postoperatively) evaluating cTnI and LLt concentrations.

MEASUREMENTS AND MAIN RESULTS

All horses required surgery for correction of a strangulating (n = 29) or nonstrangulating obstruction (n = 5) of the small or large intestine. Twenty-seven horses survived to discharge; 7 were euthanized either during (n = 1) or after (n = 6) surgery due to disease severity or systemic complications associated with the primary gastrointestinal lesion. Preoperative cTnI concentrations were increased above the normal reference interval in 24% of horses (8/34, median = 0.01 ng/mL, range = 0-12.23 ng/mL), whereas LLt concentrations were increased above the normal reference interval in 88% of horses (30/34, median = 3.37 mmol/L, range = 0.77-13.26 mmol/L). The LLt concentration was significantly higher (P < 0.05) in nonsurviving compared with surviving horses at admission, and at 24 and 72 hours postoperatively. No significant difference in the cTnI concentration was detected between groups at admission. However, the cTnI concentration was significantly higher (P<0.05) in nonsurviving compared with surviving horses at all time points postoperatively.

CONCLUSIONS

Measurement of both LLt and cTnI concentrations may provide information for prognostication in surgical colic horses. Marked increases in admission concentrations of LLt (median 7.56 mmol/L) and even moderate postoperative increases in cTnI concentration (median 0.97 ng/mL) may both indicate a poor prognosis in critically ill horses following abdominal surgery.

Alpha-2 agonists to reduce vasopressor requirements in septic shock?

One of the unsolved problems of septic shock is the poor responsiveness, or reduced vascular reactivity, to vasopressors used to increase blood pressure (BP). Attempts to restore vascular reactivity with NO inhibitors or low dose steroids have met with little success. Low vascular reactivity, which may lead to refractory shock and death, is linked to desensitization or down-regulation of alpha-1 adrenergic receptors. Our working hypothesis is that the use of alpha-2 agonists (e.g. clonidine or dexmedetomidine) in septic shock, in addition to the state-of-the-art treatment (including volume load and vasopressors), will reduce the vasopressor requirements needed to restore adequate BP. This counter-intuitive proposal is based on the fact that alpha-2 agonists will reduce the massive release of endogenous catecholamines. A decrease in plasma endogenous catecholamine concentrations will be followed by reduced down-regulation of alpha-1 receptors and/or a gradual re-sensitization of alpha-1 adrenergic receptors. In turn, this will lead to lowered vasopressor requirement, with respect to dose and duration. Our hypothesis, based on a reverse "denervation hypersensitivity", is at variance with accepted treatments, which rest only on volume load and vasopressors and emphasizes restoration of blood pressure per se. Several observations in the cardiology and anesthesia setting have shown increased vascular reactivity following alpha-2 agonist administration. Our preliminary observations in the setting of septic shock again suggest such increased vascular reactivity. Improved outcome was also observed. Rigorous work is warranted to verify reduced vasopressor requirement and improved outcome, when an alpha-2 agonist is combined with state-of -the-art treatment of septic shock.

The relationship between extravascular lung water and oxygenation in three patients with influenza A (H1N1)-induced respiratory failure

This case series reports the correlation between extravascular lung water (EVLW) and the partial arterial oxygen pressure/fractional inspiratory oxygen (PaO₂/FiO₂) ratio in three patients with severe influenza A (H1N1)-induced respiratory failure. All patients suffered from grave hypoxia (PaO₂, 26–42 mmHg) and were mechanically ventilated using biphasic airway pressure (PEEP, 12–15 mmHg; FiO₂, 0.8–1) in combination with prone positioning at 12 hourly intervals. All patients were monitored using the PICCO^® system for 8–11 days. During mechanical ventilation, a total of 62 simultaneous determinations of the PaO₂/FiO₂ ratio and EVLW were performed. A significant correlation between EVLW and the PaO₂/FiO₂ ratio (Spearman-rho correlation coefficient, –0.852; p < 0.001) was observed. In all patients, a decrease in EVLW was accompanied by an improvement in oxygenation. Serum lactate dehydrogenase levels were elevated in all patients and significantly correlated with EVLW during the intensive care unit stay (Spearman-rho correlation coefficient, 0.786; p < 0.001). In conclusion, EVLW seems increased in patients with severe H1N1-induced respiratory failure and appears to be closely correlated with impairments of oxygenatory function.