DIAGNOSIS OF INFECTIVE ENDOCARDITIS

Infective Endocarditis Among Persons Aged 18-64 Years Living with Human Immunodeficiency Virus, Hepatitis C Infection, or Opioid Use Disorder, United States, 2007-2017

BACKGROUND

Infective endocarditis (IE) is a life-threatening bacterial infection of the heart valves, most often diagnosed in older persons and persons with prior cardiac surgery. It is also associated with injection drug use, a behavior that has increased in recent years along with the US opioid crisis.

METHODS

We conducted a retrospective cohort analysis of commercial and Medicaid health insurance databases to estimate incident cases of IE in the United States in 2017, stratified by persons living with human immunodeficiency virus (HIV), hepatitis C virus (HCV), and opioid use disorder (OUD). We also estimated annual percentage changes (EAPCs) in IE from 2007-2017 among persons with commercial insurance.

RESULTS

The weighted incidence rate of IE was 13.8 cases per 100 000 persons among persons with commercial insurance, and 78.7 among those with Medicaid. The incidence rate of IE among commercially insured persons increased slightly from 2007-2017 (EAPC, 1.0%). It decreased among commercially insured persons living with HIV, from 148.0 in 2007 to 112.1 in 2017 (EAPC, -4.3%), and increased among those with HCV infection, from 172.4 in 2007 to 238.6 in 2017 (EAPC, 3.2%). Among persons aged 18-29 years with HCV infection, IE increased from 322.3 in 2007 to 1007.1 in 2017 (EAPC, 16.3%), and among those with OUD it increased from 156.4 in 2007 to 642.9 in 2017 (EAPC, 14.8%).

CONCLUSIONS

The incidence rate of IE increased markedly among young persons with HCV infections or OUD. This increase appears to parallel the ongoing national opioid crisis. Harm reduction with syringe services programs, medications for opioid use disorder, and safe injection practices can prevent the spread of HIV, HCV, and IE.

2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease: Executive Summary: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

This executive summary of the valvular heart disease guideline provides recommendations for clinicians to diagnose and manage valvular heart disease as well as supporting documentation to encourage their use.

METHODS

A comprehensive literature search was conducted from January 1, 2010, to March 1, 2020, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, Cochrane, Agency for Healthcare Research and Quality Reports, and other selected database relevant to this guideline. Structure: Many recommendations from the earlier valvular heart disease guidelines have been updated with new evidence and provides newer options for diagnosis and treatment of valvular heart disease. This summary includes only the recommendations from the full guideline which focus on diagnostic work-up, the timing and choice of surgical and catheter interventions, and recommendations for medical therapy. The reader is referred to the full guideline for graphical flow charts, text, and tables with additional details about the rationale for and implementation of each recommendation, and the evidence tables detailing the data considered in developing these guidelines.

A case of fever of unknown origin and recurrent hospital admissions in a cardiac patient: emergence of Enterobacter cloacae

A 72-year-old gentleman with significant cardiac history and a pacemaker in situ initially presented to the emergency department 5 days after he had his pacemaker-unit batteries changed. He had deranged vital signs, productive cough and fever. His chest plain radiograph did not show evidence of infection; however, he had right basal crackles on auscultation, which suggested a lower respiratory tract infection. He was treated with intravenous co-amoxiclav and supportive therapy, which led to his improvement. The patient was discharged but had to be readmitted a total of four times over the span of 4 months due to recurrent fever and associated symptoms. Transthoracic and transoesophageal echocardiograms and CT of the neck/thorax/abdomen/pelvis were done to look for endocarditis, pacemaker-unit infection and other sources of infection. However, these did not show any evidence of infection. He did have persistent raised inflammatory markers and two blood cultures growing Enterobacter cloacae. A fluorodeoxyglucose positron emission tomography scan was done, which showed evidence of pacemaker lead infection. His pacemaker unit was removed, which led to cessation of his symptoms and normalisation of his inflammatory markers. He had no further hospital admissions to date and has been regularly followed up in an outpatient cardiology clinic.

Infective endocarditis: a review for nurses

Infective endocarditis (IE) is a relatively uncommon condition that can present with a variety of noncardiac symptoms, making diagnosis of this condition challenging. Although IE is no longer uniformly fatal as it was in the preantibiotic era, it still has a high mortality rate. The major risk factor for IE, rheumatic fever, has decreased significantly in the industrialized west, but the incidence of IE remains as high as it was in the preantibiotic era. Today, IE has changed from a disease primarily of the young to one of the elderly. The increase in frequency of IE seems to be related to the fact that individuals are now living longer with chronic heart diseases and are having invasive medical procedures performed more often. The 2 main approaches to treating IE are the use of antibiotics and cardiac surgery. This article provides an overview of IE, epidemiology, pathogenesis, clinical manifestations, diagnosis criteria, and treatment options for IE.

Infective Endocarditis

Infective endocarditis is a life-threatening illness associated with significant morbidity and mortality. Previously a uniformly fatal disease, antibiotic therapy has reduced the mortality of native valve endocarditis to less than 20%. The incidence of infective endocarditis has not decreased, however, and 20,000 new cases are reported each year. Continued improvement in the prognosis of endocarditis is largely dependent on early and accurate diagnosis of the disease and its complications. Echocardiography has assumed an important role in the evaluation of infective endocarditis, both for the detection of vegetations and in the assessment of complications of the infectious process.

Identification of species of viridans group streptococci in clinical blood culture isolates by sequence analysis of the RNase P RNA gene, rnpB

OBJECTIVES

Viridans group streptococci (VGS) cause severe diseases such as infective endocarditis and septicaemia. Genetically, VGS species are very close to each other and it is difficult to identify them to species level with conventional methods. The aims of the present study were to use sequence analysis of the RNase P RNA gene (rnpB) to identify VGS species in clinical blood culture isolates, and to compare the results with the API 20 Strep system that is based on phenotypical characteristics.

METHODS

Strains from patients with septicaemia or endocarditis were analysed with PCR amplification and sequence analysis of the rnpB gene. Clinical data were registered as well.

RESULTS

One hundred and thirty two VGS clinical blood culture isolates from patients with septicaemia (n=95) or infective endocarditis (n=36) were analysed; all but one were identified by rnpB. Streptococcus oralis, Streptococcus sanguinis and Streptococcus gordonii strains were most common in the patients with infective endocarditis. In the isolates from patients with haematological diseases, Streptococcus mitis and S. oralis dominated. In addition in 76 of the isolates it was possible to compare the results from rnpB analysis and the API 20 Strep system. In 39/76 (51%) of the isolates the results were concordant to species level; in 55 isolates there were no results from API 20 Strep.

CONCLUSION

Sequence analysis of the RNase P RNA gene (rnpB) showed that almost all isolates could be identified. This could be of importance for evaluation of the portal of entry in patients with septicaemia or infective endocarditis.

Role of Streptococcus gordonii surface proteins SspA/SspB and Hsa in platelet function

Streptococcus gordonii colonization of damaged heart surfaces in infective endocarditis is dependent upon the recognition of host receptors by specific bacterial surface proteins. However, despite several attempts to identify the mechanisms involved in this interaction, the nature of the bacterial proteins required remains poorly understood. This study provides clear evidence that several S. gordonii surface proteins participate in the interaction with platelets to support platelet adhesion and induce platelet aggregation. S. gordonii strains were found to support strong (DL1-Challis, SK12, SK184, and Blackburn) or moderate (UB1545 delta hsa and CH1-Challis) adhesion or failed to support platelet adhesion (M5, M99, and Channon). In addition, under flow conditions, platelets rolled and subsequently adhered to immobilized S. gordonii at low shear (50 s(-1)) in an Hsa-dependent manner but did not interact with S. gordonii DL1 at any shear rate of >50 s(-1). S. gordonii strains either induced (DL1-Challis, SK12, SK184, UB1545 delta hsa, and M99) or failed to induce (M5, CH1-Challis, Channon, and Blackburn) platelet aggregation. Using a proteomic approach to identify differential cell wall protein expression between aggregating (DL1) and nonaggregating (Blackburn) strains, we identified antigen I/antigen II family proteins SspA and SspB. The overexpression of SspA or SspB in platelet-nonreactive Lactococcus lactis induced GPIIb/GPIIIa-dependent platelet aggregation similar to that seen with S. gordonii DL1. However, they failed to support platelet adhesion. Thus, S. gordonii has distinct mechanisms for supporting platelet adhesion and inducing platelet aggregation. Differential protein expression between strains may be important for the pathogenesis of invasive diseases such as infective endocarditis.

Usefulness of cytokines interleukin-6 and interleukin-2R concentrations in diagnosing active infective endocarditis involving native valves

The most important diagnostic value in infective endocarditis (IE) is isolation of the causative microorganism. Because premature antibiotic treatment is commonly administered before the assessment of blood cultures, the percentages of isolated microorganisms has decreased significantly within the last decades. Therefore, additional criteria for the diagnosis of IE may be helpful. It was hypothesized that assessment of interleukin-6 (IL-6) and interleukin-2R (IL-2R) may provide new diagnostic criteria for inflammation in IE. IL-6 and IL-2R serum concentrations, white blood cell count (WBC), and C-reactive protein (CRP) were measured in the blood of 47 patients with IE at the time of diagnosis and during treatment. WBC and CRP were elevated in patients with IE at the time of diagnosis. Both parameters were higher (p <0.05) in patients with positive blood cultures when compared with negative cultures. The differences persisted during the first week of treatment (p <0.01). In contrast, IL-6 and IL-2R concentrations were elevated (p <0.001) independently of the status of blood cultures. Serum concentrations of IL-6 and IL-2R decreased continuously during antibiotic treatment. Assessment of IL-6 and IL-2R could thus provide new diagnostic criteria for inflammation in IE, and these interleukins could also be suitable for monitoring the course of inflammation during treatment.

Complement activation in infective endocarditis: correlation with extracardiac manifestations and prognosis

In an infectious process complement activation is necessary for a proper immune and inflammatory response, but when exacerbated may cause tissue injuries. In infective endocarditis (IE) patients tend to develop high titres of circulating immune complexes (CIC) that activate complement. The aim of this study was to evaluate for the first time complement activation in IE for possible correlation with extracardiac manifestations and clinical prognosis. Twenty patients with IE, 14 healthy controls and 15 patients presenting mitral and aortic valve lesions (with no signs of either infection or other associated diseases), were studied. Plasma levels of C3adesArg, SC5b-9, C1rs-C1Inh and C3b(Bb)P were determined by ELISA and C3d by double decker immunoelectrophoresis. C3 and C4 levels were assayed by turbidimetry and CIC by ELISA. Elevation of plasma levels of all complement activation products, with the exception of C3b(Bb)P, indicated a significant classical pathway activation in IE patients when compared to controls (C3d: P < 0.00004; C3adesArg: P < 0.03, SC5b-9: P < 0.01, C1rs-C1Inh: P < 0.00007). CIC levels were significantly increased (P < 0.005) and C3 reduced in IE patients (P < 0.05). Elevated C3d (P < 0.02) and C3adesArg (P < 0.03) levels were associated with pulmonary manifestations. In addition, C3d was significantly elevated in the patients who died when compared to those who had a good recovery (P < 0.02). Our data demonstrate the activation of the complement classical pathway, most probably mediated by CIC, in IE and suggests C3d and C3adesArg as possible markers for extracardiac lesion and severity of the disease.

Postcardiac surgery infections

Infections following cardiac surgery, although generally uncommon, are associated with difficult management decisions and significant morbidity and mortality. They often present while the patient is either in a critical care unit, or requires CCU management. This review analyzes infections related to median sternotomy wounds, prosthetic heart valves, transvenous permanent pacemakers, automatic implantable cardioverter-defibrillators, and left ventricular assist devices. The diagnosis, microbiology, treatment and outcome of each is also discussed.

Has transesophageal echocardiography changed the approach to patients with suspected or known infective endocarditis?

Infective endocarditis is still a great clinical challenge. Its diagnosis is difficult to establish, and mortality has remained around 30%. Early diagnosis and optimal treatment are crucial fo prognosis improvement. Echocardiography plays an indispensable role in the management of this disease, especially with the recently introduced approach, transesophageal echocardiography (TEE). TEE can overcome the limitations of transthoracic echocardiography (TTE) and is superior to TTE in almost every way in providing earlier and more information for the diagnosis and treatment of infective endocarditis. TEE detects valve vegetations with much higher sensitivity and specificity than TTE. It can demonstrate smaller vegetations in the early stage of the disease and vegetations on atypical locations (e.g., mitral valve annulus), and provides detailed characterization of vegetations (e.g., location, size, mobility, and changes during treatment). Such information is of great prognostic value and may help in selecting proper treatment. TEE is more sensitive for detecting complications, such as mitral valve perforation, abscess, and subaortic complications, which respond poorly to medicine and for which timely surgery may be the best treatment. For those with prosthetic valve endocarditis, TEE is especially useful because TTE is greatly limited by the acoustic shadow of prostheses. Both positive and negative results of TEE examination are valuable for confirming or excluding infective endocarditis. TEE also plays a unique role in intraoperative monitoring and can assess surgical results before the chest is closed. TEE has become an invaluable tool for the diagnosis and management of patients with suspected or known infective endocarditis.

Assessing diagnostic criteria for active infective endocarditis

A study was performed to describe agreement among experts on their classification of patients, in the absence of information concerning risk factors, as to the presence of infective endocarditis (IE). The study also assessed the clinical characteristics that enabled the experts to determine that a patient had IE. All patients with a discharge diagnosis of IE were identified prospectively from 54 hospitals in the Delaware Valley over a 3-year period. Patients were part of a case-control study of risk factors for IE. Three infectious disease experts independently reviewed abstracted hospital records and classified each of 151 eligible patients as a definite, probable or possible case, or a probable noncase, both based on clinical judgement and using a modified standard definition. Experts were more likely to classify a patient as a definite case of IE on the basis of clinical judgement than by using the modified standard definition. Agreement between reviewers was 92 to 95% when they were distinguishing only probable non-cases from others. Agreement between reviewers on specific categories was lower (40 to 58%). The number of positive blood cultures was a strong predictor of a patient's being classified as a case, as was the type of infecting organism. It is concluded that experts are willing to make a definitive diagnosis of IE on the basis of blood culture information alone. Further supporting evidence, such as the presence of vegetation on an echocardiogram, is needed when blood culture results are ambiguous.

Application of transthoracic and transesophageal echocardiography in the diagnosis and management of infective endocarditis

Infective endocarditis continues to be a cause of significant cardiac morbidity and mortality. To improve the prognosis of patients with this disorder, early diagnosis is crucial but difficult to establish on the basis of clinical parameters alone. Echocardiography, both transthoracic and transesophageal techniques, has a major role in the detection of vegetations that are the hallmark of endocarditis. Valvular and perivalvular complications can also be well assessed by echocardiography. With the improved resolution provided by recent technologic advances in echocardiography, vegetations can be reliably detected in most patients with endocarditis. We propose that present diagnostic criteria for endocarditis be revised to include echocardiographic findings as a major parameter in the diagnosis. Finally, a diagnostic approach incorporating transthoracic and transesophageal echocardiography in these patients will be discussed taking into consideration the different degrees of clinical suspicion for the existence of the disease.

Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres

Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L less than 5 lambda) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (Ithr). Dependence of the latency on the stimulus strength (Ist) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L less than or equal to 2 lambda and Ithr less than or equal to Ist less than or equal to 1.1Ithr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.