Previous infection and the risk of ischaemic stroke in Italy: the IN2 study

New Directions in Infection-Associated Ischemic Stroke

The relationship between infections and stroke has not been fully characterized, probably delaying the development of specific treatments. This narrative review addresses mechanisms of stroke linked to infections, including hypercoagulability, endothelial dysfunction, vasculitis, and impaired thrombolysis. SARS-CoV-2, the virus that causes COVID-19, may promote the development of stroke, which may represent its most severe neurological complication. The development of specific therapies for infection-associated stroke remains a profound challenge. Perhaps the most important remaining issue is the distinction between infections that trigger a stroke versus infections that are truly incidental. This distinction likely requires the establishment of appropriate biomarkers, candidates of which are elevated levels of fibrin D-dimer and anticardiolipin/antiphospholipid antibodies. These candidate biomarkers might have potential use in identifying pathogenic infections preceding stroke, which is a precursor to establishing specific therapies for this syndrome.

Ischemic Stroke and Asymptomatic Pulmonary Opacities

PURPOSE

Pulmonary opacities are described in many chest radiograph reports in stroke patients and are often asymptomatic. The aim of this study is to investigate the clinical features associated with asymptomatic pulmonary opacities (APO) and evaluate APO prognostic value in ischemic stroke.

METHODS

We prospectively analyzed patients with acute ischemic stroke without pneumonia symptoms referred to our stroke center. All patients underwent a chest x-ray within 48 hours after admission. We divided patients with APO (defined as asymptomatic area of increased pulmonary attenuation) and patients without APO. Firstly, we compared clinical, laboratory, and echocardiographic parameters between groups; secondly, APO were evaluated as a possible predictor of the neurological severity at discharge and functional outcome at 90 days.

RESULTS

We included 162 patients, 78 of whom had APO. On univariate analysis, we observed a significant difference between patients with APO and patients without APO in terms of neutrophils (73,56±10,10 vs 69,72±12,29; p=0,031), atrial fibrillation (AF, paroxysmal 27,4% vs 25,6%; permanent 19% vs 2,6%; p<0,002), cardioembolic etiology (37,2% vs 22,7%, p <0,033), thrombectomy (58,3% vs 42,9%, p <0,05), dysphagia/vomit (34,5% vs 14,10%, p<0,005), admission NIHSS (14,20±5,98 vs 10,29±5,82, p=0,001), discharge NIHSS (8,68±6,73 vs 5,64±6,20; p=0,003), and 90 days mRS (3,47±2,12 vs 2,31±1,93; p=0,001). On multivariate analysis, APO were significantly associated with admission NIHSS and AF. APO were a predictor of outcome on univariate analysis, but not on multivariate.

CONCLUSION

APO in acute ischemic stroke are associated with AF. APO were not a predictor of neurological and functional outcome.

Assessing short-term risk of ischemic stroke in relation to all prescribed medications

We examined the short-term risk of stroke associated with drugs prescribed in Norway or Sweden in a comprehensive, hypothesis-free manner using comprehensive nation-wide data. We identified 27,680 and 92,561 cases with a first ischemic stroke via the patient- and the cause-of-death registers in Norway (2004–2014) and Sweden (2005–2014), respectively, and linked these data to prescription databases. A case-crossover design was used that compares the drugs dispensed within 1 to 14 days before the date of ischemic stroke occurrence with those dispensed 29 to 42 days before the index event. A Bolasso approach, a version of the Lasso regression algorithm, was used to select drugs that acutely either increase or decrease the apparent risk of ischemic stroke. Application of the Bolasso regression algorithm selected 19 drugs which were associated with increased risk for ischemic stroke and 11 drugs with decreased risk in both countries. Morphine in combination with antispasmodics was associated with a particularly high risk of stroke (odds ratio 7.09, 95% confidence intervals 4.81–10.47). Several potentially intriguing associations, both within and across pharmacological classes, merit further investigation in focused, follow-up studies.

Extrinsic and Intrinsic Responses in the Development and Progression of Atherosclerosis

Atherosclerosis is a multifactorial disease that is thought to be primarily inflammatory in origin. Given the contribution of inflammation to the development and progression of atherosclerosis, other conditions that are characterised by a dysregulated inflammatory response have also been proposed to play a role. The purpose of this review is to organise and present the various inflammatory processes that can affect atherosclerosis into two broad categories: extrinsic or host-independent and intrinsic or host-dependent. Within these two categories, we will discuss various processes that may contribute to the development and progression of atherosclerosis and the clinical studies describing these associations. Although the clinical trials investigating anti-inflammatory therapies have to date provided mixed results, further studies, particularly in conjunction with lipid-lowering and blood pressure lowering therapies should be considered.

Neurological consequences of COVID-19: what have we learned and where do we go from here?

The coronavirus disease-19 (COVID-19) pandemic is an unprecedented worldwide health crisis. COVID-19 is caused by SARS-CoV-2, a highly infectious pathogen that is genetically similar to SARS-CoV. Similar to other recent coronavirus outbreaks, including SARS and MERS, SARS-CoV-2 infected patients typically present with fever, dry cough, fatigue, and lower respiratory system dysfunction, including high rates of pneumonia and acute respiratory distress syndrome (ARDS); however, a rapidly accumulating set of clinical studies revealed atypical symptoms of COVID-19 that involve neurological signs, including headaches, anosmia, nausea, dysgeusia, damage to respiratory centers, and cerebral infarction. These unexpected findings may provide important clues regarding the pathological sequela of SARS-CoV-2 infection. Moreover, no efficacious therapies or vaccines are currently available, complicating the clinical management of COVID-19 patients and emphasizing the public health need for controlled, hypothesis-driven experimental studies to provide a framework for therapeutic development. In this mini-review, we summarize the current body of literature regarding the central nervous system (CNS) effects of SARS-CoV-2 and discuss several potential targets for therapeutic development to reduce neurological consequences in COVID-19 patients.

Neurologic complications of COVID-19

BACKGROUND

Much of the focus regarding the global pandemic of coronavirus disease of 2019 (COVID-19) has been on the cardiovascular, pulmonary, and hematologic complications. However, neurologic complications have arisen as an increasingly recognized area of morbidity and mortality.

OBJECTIVE

This brief report summarizes the neurologic complications associated with COVID-19 with an emphasis on the emergency medicine clinician.

DISCUSSION

COVID-19 has infected over 3.5 million people and killed over 240,000 people worldwide. While pulmonary complications are profound, the neurologic system is also significantly impacted, with complications including acute cerebrovascular events, encephalitis, Guillain-Barré syndrome, acute necrotizing hemorrhagic encephalopathy, and hemophagocytic lymphohistiocytosis. Additionally, patients on immunosuppressive medications for pre-existing neurologic issues are at an increased risk for complications with COVID-19 infection, and many of the currently proposed COVID-19 therapies can interact with these medications.

CONCLUSIONS

When caring for COVID-19 patients, emergency medicine clinicians should be aware of the neurologic complications from COVID-19.

Ischemic stroke and infectious diseases in low-income and middle-income countries

PURPOSE OF REVIEW

To address the important relationships between stroke and infection, focusing on the most frequent infections found in low-income and middle-income countries.

RECENT FINDINGS

Stroke is one of the leading causes of mortality and disability worldwide, with a great proportion of the stroke burden occurring in low-income and middle-income countries. Infectious diseases are still a great health problem in developing countries and it is possible that the proportion of infection-related strokes is greater in these nations. Infectious diseases and stroke have a bidirectional relationship. Common infections may act as risk factors and can trigger stroke through different mechanisms in their acute phase. Several intracranial and systemic infections can cause stroke as a direct complication, such as Chagas disease, neurosyphilis, tuberculous meningitis, and neurocysticercosis. These conditions are of particular interest to low-income and middle-income countries, but also relevant to high-income nations because of increasing migration. Finally, infection is a frequent poststroke complication, with great impact in the patient outcome.

SUMMARY

Infectious diseases and stroke are common problems in low-income and middle-income countries. More studies are necessary to fully elucidate the real impact of infectious diseases on stroke burden, especially in countries where epidemiological data are still scarce.

[Possibilities for the diagnosis of inflammatory reaction in ischemic stroke]

AIM

To study diagnostic possibilities for determining the content of nitrite and N-nitroso compounds (NO₂^-+RNNO) in blood plasma and cerebrospinal fluid (CSF) in patients with acute ischemic stroke (IS).

MATERIAL AND METHODS

Twenty-four patients with IS were examined. The content of NO oxidation products was determined in venous blood and CSF by using an enzyme sensor based on the unique property of nitrite (NO₂^-), N-nitroso compounds (RNNO), S-nitrosothiols and dinitrosyl iron complexes to inhibit the enzyme catalase in the presence of halide ions. The study was conducted on the 1st day of IS.

RESULTS AND CONCLUSION

CSF in patients with IS contained nitrite and N-nitroso compounds (NO₂^-+RNNO) in concentrations ranging from 0.4 to 2.0 µm. The relationship between the size of IS and the concentration of NO₂^-+RNNO in CSF was shown. It was 1.01±0.13 µm in patients with medium IS and 0.71±0.07 µm in patients with small IS (U-criterion 16.5; p<0.05). There was no correlation between the severity of neurological deficit at the time of hospitalization and discharge from the hospital and the content of NO₂^-+RNNO in CSF (r=0.134; p>0.5; r=0.155; p>0.5, respectively). Plasma NO₂^-+RNNO levels were not associated with the presence and size of IS though they were elevated in patients with inflammatory complications. In conclusion, NO₂^-+RNNO can be considered as a marker of inflammation in patients with IS. Their presence in CSF reflects the extent of brain damage, but not the presence of concomitant inflammatory diseases.

Beneficial Effects of Vaccination on Cardiovascular Events: Myocardial Infarction, Stroke, Heart Failure

Influenza and pneumococcal infections have been suggested to be potential risk factors for causing adverse cardiovascular events, especially in high-risk patients. Vaccination against respiratory infections in patients with established cardiovascular disease (CVD) could serve as a potential cost-effective intervention to improve their clinical outcomes and cardiac societies have encouraged it. Previous studies have shown that influenza vaccination reduce mortality, acute coronary syndromes and hospitalization in patients with coronary heart disease (CHD) and/or heart failure (HF). However, there is a paucity of randomized prospective clinical trials in the field of the pneumococcal vaccination, and additional higher-quality evidence is needed. Furthermore, questions around the role of vaccination in the primary prevention of CVD, the optimal dose and timing are largely unanswered. The pathophysiologic mechanism in which vaccination provides cardiovascular protection may be related to the modification of the immune-inflammatory model of atherogenesis. The present review summarizes the current evidence and understanding for vaccination against influenza and streptococcus pneumoniae in CHD, HF and stroke and highlights its beneficial effect in the reduction of adverse cardiovascular events.

Systemic Inflammatory Response Syndrome (SIRS) and the Pattern and Risk of Sepsis Following Gastrointestinal Perforation

Background

Systemic inflammatory response syndrome (SIRS) is characterized by systemic inflammation and tissue injury. Secondary sepsis is a common critical illness associated with poor clinical outcome. The aim of this study was to investigate the risk of SIRS-positive and SIRS-negative sepsis following gastrointestinal (GI) perforation.

Material/Methods

A retrospective study included 51 patients with GI perforation who had clinical evidence of sepsis, with or without SIRS. Clinical outcome was assessed at day 30 using the Glasgow Outcome Scale (GOS) (score, 1–5) and the sequential organ failure assessment (SOFA) (score, 1–6) to determine organ function.

Results

Fifty-one patients were included in the study (median age, 74 years; 37 male patients); 20 patients (39.2%) developed secondary sepsis; 16 patients (80%) had SIRS-negative sepsis; four patients had SIRS-positive sepsis. An increased SOFA score was a significant independent predictor of GI perforation with sepsis (5.4±3.1 vs. 1.5±2.8) (P<0.0001). Patients with GI perforation with SIRS-negative sepsis had a significantly less favorable outcome (5/16 vs. 2/35) (P=0.03). The risk of SIRS-negative sepsis following GI perforation was 39.2%, and the risk of mortality for SIRS-negative sepsis was 31.3%. In the Cox regression analysis, septic shock and septic encephalopathy were associated with a worse clinical outcome.

Conclusions

The findings of this study support the recognition of SIRS-negative sepsis following GI perforation as an important condition to recognize clinically, given its association with increased patient morbidity and mortality.

The association of adult vaccination with the risk of cerebrovascular ischemia: A systematic review and meta-analysis

There is mounting evidence supporting infection as an independent risk factor for ischemic stroke (IS), while preliminary data indicate that vaccination may prevent IS. We performed a systematic review and meta-analysis of available randomized clinical trials (RCTs) or prospective observational cohorts reporting associations of influenza vaccination (IV) and/or pneumococcal vaccination (PV) with IS. We identified a total of 12 studies (543,311 patients; 47.4% vaccinated). Vaccination was not related to the risk of IS (RR=1.06, 95%CI: 0.74-1.51, p=0.77), with no significant differences (p=0.26) among RCTs (RR=0.66, 95%CI: 0.30-1.47) and observational studies (RR=1.11, 95%CI: 0.76-1.61). Evidence of considerable heterogeneity was identified within observational studies (I²=98%), but not within RCTs (I²=0%). In subgroup analyses according to vaccination type, IV was associated with a significantly lower risk of IS (RR=0.87, 95%CI: 0.79-0.96, p=0.004) with moderate evidence of heterogeneity (I²=53%). No association was seen for PV (RR=1.38, 95%CI: 0.60-3.16, p=0.45), where considerable heterogeneity was identified (I²=97%). In the additional adjusted analyses of observational studies, vaccination tended to be associated with lower risk of IS (HRadjusted=0.87; 95%CI: 0.75-1.01; p=0.07). The findings of this meta-analysis indicate that IV may be associated with a lower risk of IS. This association was not reproduced for PV or the combination of two vaccines. Substantial heterogeneity was detected across observational studies for all outcome events, while moderate to low heterogeneity was identified across included RCTs. These preliminary findings require independent validation in large RCTs.

Immune-inflammatory responses in atherosclerosis: Role of an adaptive immunity mainly driven by T and B cells

Adaptive immune response plays an important role in atherogenesis. In atherosclerosis, the proinflammatory immune response driven by Th1 is predominant but the anti-inflammatory response mediated mainly by regulatory T cells is also present. The role of Th2 and Th17 cells in atherogenesis is still debated. In the plaque, other T helper cells can be observed such as Th9 and Th22 but is little is known about their impact in atherosclerosis. Heterogeneity of CD4(+) T cell subsets presented in the plaque may suggest for plasticity of T cell that can switch the phenotype dependening on the local microenvironment and activating/blocking stimuli. Effector T cells are able to recognize self-antigens released by necrotic and apoptotic vascular cells and induce a humoral immune reaction. Tth cells resided in the germinal centers help B cells to switch the antibody class to the production of high-affinity antibodies. Humoral immunity is mediated by B cells that release antigen-specific antibodies. A variety of B cell subsets were found in human and murine atherosclerotic plaques. In mice, B1 cells could spontaneously produce atheroprotective natural IgM antibodies. Conventional B2 lymphocytes secrete either proatherogenic IgG, IgA, and IgE or atheroprotective IgG and IgM antibodies reactive with oxidation-specific epitopes on atherosclerosis-associated antigens. A small population of innate response activator (IRA) B cells, which is phenotypically intermediate between B1 and B2 cells, produces IgM but possesses proatherosclerotic properties. Finally, there is a minor subset of splenic regulatory B cells (Bregs) that protect against atherosclerotic inflammation through support of generation of Tregs and production of anti-inflammatory cytokines IL-10 and TGF-β and proapoptotic molecules.

Chlamydia pneumoniae acute liver infection affects hepatic cholesterol and triglyceride metabolism in mice

OBJECTIVE

Chlamydia pneumoniae has been linked to atherosclerosis, strictly associated with hyperlipidemia. The liver plays a central role in the regulation of lipid metabolism. Since in animal models C. pneumoniae can be found at hepatic level, this study aims to elucidate whether C. pneumoniae infection accelerates atherosclerosis by affecting lipid metabolism.

METHODS

Thirty Balb/c mice were challenged intra-peritoneally with C. pneumoniae elementary bodies and thirty with Chlamydia trachomatis, serovar D. Thirty mice were injected with sucrose-phosphate-glutamate buffer, as negative controls. Seven days after infection, liver samples were examined both for presence of chlamydia and expression of genes involved in inflammation and lipid metabolism.

RESULTS

C. pneumoniae was isolated from 26 liver homogenates, whereas C. trachomatis was never re-cultivated (P < 0.001). C. pneumoniae infected mice showed significantly increased serum cholesterol and triglycerides levels compared both with negative controls (P < 0.001 and P = 0.0197, respectively) and C. trachomatis infected mice (P < 0.001). Liver bile acids were significantly reduced in C. pneumoniae compared to controls and C. trachomatis infected mice. In C. pneumoniae infected livers, cholesterol 7α-hydroxylase (Cyp7a1) and low-density lipoprotein receptor (Ldlr) mRNA levels were reduced, while inducible degrader of the low-density lipoprotein receptor (Idol) expression was increased. Hypertriglyceridemia was associated to reduced expression of hepatic carnitine palmitoyltransferase-1a (Cpt1a) and medium chain acyl-Coenzyme A dehydrogenase (Acadm). Pro-inflammatory cytokines gene expression was increased compared to negative controls. Conversely, in C. trachomatis infected animals, normal serum lipid levels were associated with elevated pro-inflammatory cytokines gene expression, linked to only a mild disturbance of lipid regulatory genes.

CONCLUSION

Our results indicate that C. pneumoniae mouse liver infection induces dyslipidemic effects with significant modifications of genes involved in lipid metabolism.

The influence of previous infections and antichlamydia pneumoniae seropositivity on functional outcome in ischemic stroke patients: results from the IN2 study

Although a growing attention is being paid to acute ischemic stroke patients, the correlation between clinical outcome and infectious events in this population has been poorly investigated. 749 ischemic stroke (mean age 71 years old, males 56%) patients were enrolled in this prospective case-control study by 11 Italian Stroke Units. Demographic data, vascular risk factors, previous infections and post-stroke infections (PSIs) were recorded. Blood samples were collected and the enzyme-linked immunoassay was chosen to measure Chlamydia pneumoniae IgG and IgA plasma antibodies (antibody titers were classified with specific cut-off levels: IgA > 1:16 and IgG > 1:64). Early poor outcome was defined as mRS score >2 at discharge, while poor outcome at 6-month follow-up. Univariate and multivariate analyses were performed. Median NIHSS was 7, IgA and IgG antichlamydia pneumoniae seropositivities were observed in 308 (37.1%) and 207 (23.6%) patients, respectively. Multivariate analyses showed significant correlations between PSIs and NIHSS (RR: 1.06; 95% CI 1.02-1.09; p < 0.001) and PSIs and IgA antichlamydia pneumoniae seropositivity (RR: 3.84; 95% CI 2.53-5.84; p < 0.001). Significant disability was associated with baseline NIHSS (RR: 1.32; 95% CI 1.16-1.50; p < 0.001), IgA (RR: 2.67; 95% CI 1.06-6.70; p = 0.035) and IgG antichlamydia (RR: 5.75; 95% CI 1.83-18.03; p = 0.003) seropositivity and atrial fibrillation (RR: 2.58; 95% CI 1.81-3.67; p < 0.001). While previous infections were not associated with functional outcome, antichlamydia antibodies play a negative role in ischemic stroke patients. Preventive strategies may reduce the stroke burden and improve the clinical outcome.