Septic cardiomyopathy

Clinical implications of septic cardiomyopathy: A narrative review

Sepsis is caused by the body's dysregulated response to infection, which can lead to multiorgan injury and death. Patients with sepsis may develop acute cardiac dysfunction, termed septic cardiomyopathy, which is a global but reversible dysfunction of both sides of the heart. This narrative review discusses the mechanistic changes in the heart during septic cardiomyopathy, its diagnosis, existing treatment options regarding severity and course, and emerging treatment approaches. Although no standardized definition for septic cardiomyopathy exists, it is described as a reversible myocardial dysfunction that typically resolves within 7 to 10 days. Septic cardiomyopathy is often diagnosed based on electrocardiography, cardiac magnetic resonance imaging, biomarkers, and direct invasive and noninvasive measures of cardiac output. Presently, the treatment of septic cardiomyopathy is similar to that of sepsis, primarily focusing on acute interventions. Treatments for cardiomyopathy often include angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and diuretics. However, because of profound hypotension in sepsis, many cardiomyopathy treatments are contraindicated in patients with septic cardiomyopathy. Substantial efforts have been made to study the pathophysiological mechanisms and diagnostic options; however, the lack of a uniform definition for septic cardiomyopathy is challenging for physicians when considering treatments. Another challenge for physicians is that the treatment for septic cardiomyopathy has only focused on acute intervention, whereas the treatment for other cardiomyopathies has been provided on a long-term basis. A better understanding of the underlying mechanisms of septic cardiomyopathy may contribute to the development of a unified definition of the condition and novel treatment options.

Therapeutic S100A8/A9 blockade inhibits myocardial and systemic inflammation and mitigates sepsis-induced myocardial dysfunction

BACKGROUND AND AIMS

The triggering factors of sepsis-induced myocardial dysfunction (SIMD) are poorly understood and are not addressed by current treatments. S100A8/A9 is a pro-inflammatory alarmin abundantly secreted by activated neutrophils during infection and inflammation. We investigated the efficacy of S100A8/A9 blockade as a potential new treatment in SIMD.

METHODS

The relationship between plasma S100A8/A9 and cardiac dysfunction was assessed in a cohort of 62 patients with severe sepsis admitted to the intensive care unit of Linköping University Hospital, Sweden. We used S100A8/A9 blockade with the small-molecule inhibitor ABR-238901 and S100A9-/- mice for therapeutic and mechanistic studies on endotoxemia-induced cardiac dysfunction in mice.

RESULTS

In sepsis patients, elevated plasma S100A8/A9 was associated with left-ventricular (LV) systolic dysfunction and increased SOFA score. In wild-type mice, 5 mg/kg of bacterial lipopolysaccharide (LPS) induced rapid plasma S100A8/A9 increase and acute LV dysfunction. Two ABR-238901 doses (30 mg/kg) administered intraperitoneally with a 6 h interval, starting directly after LPS or at a later time-point when LV dysfunction is fully established, efficiently prevented and reversed the phenotype, respectively. In contrast, dexamethasone did not improve cardiac function compared to PBS-treated endotoxemic controls. S100A8/A9 inhibition potently reduced systemic levels of inflammatory mediators, prevented upregulation of inflammatory genes and restored mitochondrial function in the myocardium. The S100A9-/- mice were protected against LPS-induced LV dysfunction to an extent comparable with pharmacologic S100A8/A9 blockade. The ABR-238901 treatment did not induce an additional improvement of LV function in the S100A9-/- mice, confirming target specificity.

CONCLUSION

Elevated S100A8/A9 is associated with the development of LV dysfunction in severe sepsis patients and in a mouse model of endotoxemia. Pharmacological blockade of S100A8/A9 with ABR-238901 has potent anti-inflammatory effects, mitigates myocardial dysfunction and might represent a novel therapeutic strategy for patients with severe sepsis.

The protective role of neuregulin-1: A potential therapy for sepsis-induced cardiomyopathy

The extremely high mortality of sepsis in intensive care units, caused primarily by sepsis-induced cardiomyopathy, is a pressing issue. Current studies have revealed the importance of the neuregulin-1 (NRG-1)/ErbB signaling axis at the cardiovascular level and the positive effect of NRG-1 on cardiac function in patients with heart failure. To investigate the protective mechanism of NRG-1 against myocardial injury in septic rats, a cecal ligation and puncture (CLP) model was applied. Animals were administered either a vehicle or recombinant human NRG-1 (rhNRG-1, 10μg/kg). Their survival rates were noted 24h after CLP. The hemodynamic method was used to evaluate their cardiac function. The myocardial morphology was observed. An enzyme-linked immunosorbent assay was used to detect the level of cardiac troponin-T (cTn-T), cytokines, and angiotensin II (Ang II) in the serum and myocardium. Compared with the vehicle, rhNRG-1 improved survival of rats and prevented hemodynamic derangement, as reflected in the increased mean arterial pressure, left ventricular systolic pressure, ±dp/dt max, and decreased left ventricular end-diastolic pressure (P<0.05). Furthermore, the serum levels of cTn-T and pro-inflammatory cytokines (tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, and IL-6) were significantly increased in vehicle-treated rats but reduced in rhNRG-1-treated rats. The latter also showed decreased concentration of macrophage inhibitory factor and Ang II in the myocardium (P<0.05). These results suggest that NRG-1 improved cardiac function and protected cardiomyocytes of rats from CLP-induced sepsis by suppressing the immune inflammatory response and excessive activation of the renin-angiotensin-aldosterone system. Ultimately, NRG-1 increased the survival rate of rats.

Circulating Histones Are Major Mediators of Cardiac Injury in Patients With Sepsis

OBJECTIVE

To investigate the impact of circulating histones on cardiac injury and dysfunction in a murine model and patients with sepsis.

DESIGN

Prospective, observational clinical study with in vivo and ex vivo translational laboratory investigations.

SETTING

General ICU and university research laboratory.

SUBJECTS

Sixty-five septic patients and 27 healthy volunteers. Twelve-week-old male C57BL/6N mice.

INTERVENTIONS

Serial blood samples from 65 patients with sepsis were analyzed, and left ventricular function was assessed by echocardiography. Patients' sera were incubated with cultured cardiomyocytes in the presence or absence of antihistone antibody, and cellular viability was assessed. Murine sepsis was initiated by intraperitoneal Escherichia coli injection (10(8) colony-forming unit/mouse) in 12-week-old male C57BL/6N mice, and the effect of antihistone antibody (10 mg/kg) was studied. Murine blood samples were collected serially, and left ventricular function was assessed by intraventricular catheters and electrocardiography.

MEASUREMENTS AND MAIN RESULTS

Circulating histones and cardiac troponins in human and murine plasma were quantified. In 65 patients with sepsis, circulating histones were significantly elevated compared with healthy controls (n = 27) and linearly correlated with cardiac troponin T levels (rs = 0.650; p < 0.001), noradrenaline doses required to achieve hemodynamic stability (rs = 0.608; p < 0.001), Sequential Organ Failure Assessment scores (p = 0.028), and mortality (p = 0.008). In a subset of 36 septic patients without prior cardiac disease, high histone levels were significantly associated with new-onset left ventricular dysfunction (p = 0.001) and arrhythmias (p = 0.01). Left ventricular dysfunction only predicted adverse outcomes when combined with elevated histones or cardiac troponin levels. Furthermore, patients' sera directly induced histone-specific cardiomyocyte death ex vivo, which was abrogated by antihistone antibodies. In vivo studies on septic mice confirmed the cause-effect relationship between circulating histones and the development of cardiac injury, arrhythmias, and left ventricular dysfunction.

CONCLUSION

Circulating histones are novel and important mediators of septic cardiomyopathy, which can potentially be utilized for prognostic and therapeutic purposes.