Aortic Valve Endocarditis


Article Author:
Nauman Khalid
Evan Shlofmitz


Article Editor:
Sarah Ahmad


Editors In Chief:
Kranthi Sitammagari
Mayank Singhal


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Trevor Nezwek
Radia Jamil
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Hussain Sajjad
Steve Bhimji
Muhammad Hashmi
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beata Beatty
Beenish Sohail
Nazia Sadiq
Hajira Basit
Phillip Hynes


Updated:
6/30/2019 12:25:34 PM

Introduction

Infective endocarditis occurs globally and is the infection of the endocardial surface of the native valve, prosthetic heart valve, or an implanted cardiac device such as a permanent pacemaker or a cardioverter defibrillator.[1] Over the past few decades, there has been a change in both the host and the pathogen. Staphylococcus aureus has surpassed Streptococcus as the most common etiologic pathogen worldwide and especially in the developed world given its common association with health-care contact and invasive procedures. Changes in the host include older and sicker patients who carry a high burden of comorbidities. Resistance to antibiotics is another challenge threatening healthcare worldwide and seems to be growing.

Despite technological advances in diagnostic and therapeutic modalities, the overall mortality has not improved. Aortic valve infective endocarditis is a life-threatening disease associated with high mortality and morbidity. In this chapter, we will provide an overview of the infective endocarditis with a particular emphasis on the aortic valve endocarditis. The term native valve endocarditis denotes a cardiac infection that involves the leaflets of the valves, the endocardial surface, chordae tendinae, congenital defects, and anastomosis sites. Prosthetic valve endocarditis is defined by an infection involving the artificial valves, conduits, catheters, assist devices, pacemakers, defibrillators, or other artificial intracardiac structures.

Etiology

The etiology of infective endocarditis has its basis on whether the valve is native or prosthetic and for prosthetic valve endocarditis, the etiology is dependent upon the timing with early phase defined as less than two months and late phase defined as greater than 12 months. The native valve infective endocarditis is most commonly caused by Streptococcus viridans and Staphylococcus aureus. For the early phase, prosthetic valve endocarditis causative agents include coagulase-negative staphylococci (Staphylococcus epidermidis) and Staphylococcus aureus whereas for late phase the key culprits include Streptococcus viridans and Staphylococcus aureus. Enterococci enter the bloodstream as a consequence of gastrointestinal or genitourinary tracts manipulation. Streptococcus bovis and Clostridium septicum are associated with colonic malignancies whereas HACEK group agents (Haemophilus, Aggregatibacter (previously Actinobacillus), Cardiobacterium, Eikenella, Kingella) infect patients with poor dental hygiene or from needle contaminate with saliva in intravenous drug users. Fungal endocarditis is the gravest form of infective endocarditis, and the risk factors include prosthetic heart valves, intravenous drug use, and an immunocompromised state.

Epidemiology

Infective endocarditis can community-acquired, or it can be related to healthcare exposure. The epidemiological trends and disease patterns of infective endocarditis have evolved across the globe. In developing countries, rheumatic heart disease remains the key risk factor, and affected patients are usually younger, and community-acquired, penicillin-sensitive streptococci typically cause the infection.[1] In developed world degenerative valve disease, malignancy, intravenous drug use, diabetes mellitus, and congenital heart disease are the predominant risk factors, and the mean age of the patients is older than the ’70s. The cases of healthcare-acquired infective endocarditis due to Staphylococcal infection has surged over the past two decades owing to increase in the use of invasive procedures, cardiovascular implantable electronic devices, long-term intravenous lines, percutaneous, minimally invasive and prosthetic heart valves.[2] There has been an increased incidence of infective endocarditis after minimally invasive aortic valve surgery or percutaneous transcatheter aortic valve replacement.[3]

Pathophysiology

The pathophysiologic underpinning of infective endocarditis involves the following steps: bacteremia (spontaneous or hospital-acquired) that delivers the pathogen to the surface of the valve, adherence of the circulating pathogen to the prepared valve surface and ultimately the invasion of the valvular leaflets. Circulating pathogen do not adhere to the normal endothelium. Injury of the valve alters the architecture of the endothelial cells rendering them susceptible to colonization with bacteria.[4]

History and Physical

History is crucial, and patients describe fevers, chills, dyspnea, orthopnea, night sweats, fatigue, and weight loss. Patients can also present with a transient ischemic attack, stroke, myocardial infarction, or heart failure symptoms. On physical exam, patients with aortic valve endocarditis may demonstrate an aortic insufficiency diastolic murmur (new or change in preexisting murmur) and signs of heart failure if aortic valve function is compromised. Other sequelae may include neurological findings such as vision loss, weakness, or peripheral stigmata of the disease as described above including splinter hemorrhages, Osler nodes, Roth spots, Janeway lesions, organomegaly, and hematuria if kidneys involved.

Evaluation

The Modified Duke Criteria are applicable in the evaluation of patients suspected of infective endocarditis. Three categories include definite infective endocarditis, possible infective endocarditis, or rejected infective endocarditis.[5]

Definite infective endocarditis further subclassifies into[6][5][7]:

  • Definite infective endocarditis by pathological criteria: where microorganisms are present on culture or histologic examination of the vegetation, embolized vegetation or an intracardiac abscess, or pathological lesions demonstrating active endocarditis
  • Definite infective endocarditis by clinical criteria: defined by the presence of two major criteria, one major criterion plus three minor criteria, or five minor criteria in The Modified Duke Criteria

Major clinical criteria are defined as follows[5]:

  • Multiple positive blood cultures, single positive culture for Coxiella burnetii or antiphase I IgG antibody titer greater than 1 to 800
  • Endocardial involvement (presence of new valvular regurgitation
  • Presence of vegetation, abscess or dehiscence (worsening or a change of pre-existing murmur does not meet criteria)

Minor clinical criteria are as follows[5]:

  • Predisposing heart condition or use of intravenous drug use
  • Fever with body temperature greater than 38 degrees C (100.4 degrees F)
  • Vascular phenomena: arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhages, and Janeway lesion
  • Immunologic phenomena: glomerulonephritis, Osler nodes, Roth spots, and rheumatoid factor, and
  • Positive blood culture that does not meet the major criteria

Possible infective endocarditis criteria are when there are one major criterion and one minor criterion or three minor criteria present. Rejected infective endocarditis is defined when there is likely an alternative diagnosis, or there is no pathological evidence of IE with fewer than 4 days of antibiotic therapy or there is the resolution of clinical symptoms with fewer than 4 days of antibiotic therapy.[5]

It is important to note that prior antibiotic therapy may mask the histopathological evidence of infective endocarditis. Vegetation on an echocardiogram is an oscillating intracardiac mass on the valve or supporting structures, in the path of regurgitant jets. Presence of abscess or partial dehiscence of prosthetic valve also fulfills echocardiographic criteria of infective endocarditis. A transthoracic echocardiogram should be validated by transesophageal echocardiogram in the evaluation for patients with suspected infective endocarditis whenever indicated.

Treatment / Management

The American Heart Association published its updated guidelines for infective endocarditis in 2015.[8] In those guidelines, specific recommendations are for the following[8]:

  • Native valve highly susceptible (MIC less than or equal to 0.12 mcg/ml) viridans group streptococci (VGS) infective endocarditis
  • VGS and S. gallolyticus (bovis) with MIC greater than 0.12 to less than 0.5 mcg/ml
  • A defective and Granulicatella species, and VGS with penicillin MIC greater than or equal to 0.5 mcg/ml
  • VGS or S. gallolyticus involving prosthetic material
  • Staphylococci, Staphylococci involving prosthetic material
  • Enterococci, HACEK micro-organisms
  • Non-HACEK gram-negative bacilli, culture-negative endocarditis and fungi

Recommendations for antimicrobial therapy, according to the causative pathogen are complex and well summarized in the 2015 American Heart Association practice guidelines.[8] Treatment for left-sided infective endocarditis (aortic and mitral) is similar, and the recommendations are based on the pathogen, its susceptibility, timeline (acute vs. subacute) and whether it is native or prosthetic valve infective endocarditis. Generally speaking, for subacute native valve infective endocarditis, S. viridans and enterococci need to be covered, and the usual treatment involves IV penicillin (2.4 g, every 4 hours) for up to 4 weeks with gentamicin (1 mg/kg, every 12 hours) for 2 weeks (for suspected aminoglycoside-susceptible enterococci).

Adjunctive therapy with aminoglycosides for native valve infective endocarditis is not recommended because of the risk of renal toxicity and because it doesn’t decrease mortality. Likewise, rifampin is not recommended because of the risk of hepatotoxicity. However, if the culprit is aminoglycoside-susceptible enterococci, then gentamicin can be added to the regimen.[9] Additionally, for prosthetic valve infective endocarditis, the combination therapy of vancomycin and aminoglycoside or rifampin is acceptable. For acute native valve, infective endocarditis treatment S. aureus needs to be covered. The treatment includes nafcillin for methicillin-susceptible S. aureus (MSSA) or cefazolin if patients are allergic to nafcillin. For methicillin-resistant Staphylococcus aureus (MRSA), vancomycin is the recommended antibiotic. The alternative is daptomycin, which requires closer monitoring for dosing. Candida and Aspergillus may respond to medical therapy 5-fluorouracil and amphotericin B respectively, however, these patients frequently require surgical therapy. Among patients with mechanical valve endocarditis who have experienced a central nervous system embolic event, it is reasonable to discontinue for 2 weeks all forms of anticoagulation.[8]

If medical therapy fails, surgical intervention is often necessary. Class I indications for surgery in patients with infective endocarditis include valvular dysfunction with symptoms of congestive heart failure, left-sided infective endocarditis caused by Staphylococcus aureus, fungal, or other highly resistant microorganisms, infective endocarditis with conduction defects or heart block, annular or aortic abscess, persistent infection 5 to 7 days after initiation of antibiotic therapy [10]. For native valve endocarditis, eradication of the infected valvular tissue with subsequent valve repair or replacement is the primary therapy. For native valve endocarditis limited to the leaflets/cusps, repair should be performed whenever feasible (Class I) [10]. For prosthetic valve endocarditis that spares the aortic root and annulus after radical resection, implantation of a new prosthetic valve (tissue or mechanical) is reasonable (Class IIa).[10]However, if the annulus is destroyed or if the infection has spread beyond the aortic root, then reconstruction and the use of an allograft or a biologic tissue root is preferable to a prosthetic valved conduit (Class IIa).[10]

Differential Diagnosis

The principal differential diagnoses for infective endocarditis include the following:

  1. Nonbacterial thrombotic endocarditis which was formerly known as marantic endocarditis - causes small sterile vegetations on the valve leaflets; predisposing conditions for this include certain malignancies and hypercoagulable states
  2. Libman–Sacks endocarditis: causes verrucous vegetations and is associated with systemic lupus erythematosus
  3. Vasculitis
  4. Connective tissue disease
  5. Fever of unknown origin

Prognosis

The in-hospital mortality for infective endocarditis is around 20%.[9] Risk factors for increased mortality include advanced age, infective endocarditis caused by S. Aureus P. aeruginosa, Enterobacteriaceae, or fungi, a heavy burden of comorbidities (end-stage renal disease requiring hemodialysis, prosthetic valve endocarditis, severe heart failure, stroke, abscess, severe immunosuppression due to HIV infection, and development of perivalvular extension or a myocardial abscess).[9] Embolic events to the brain are a significant cause of morbidity and mortality in patients with infective endocarditis. In a study of 1437 consecutive patients with left-sided endocarditis, the incidence of stroke in patients receiving appropriate antimicrobial therapy was 4.82 per 1000 patient days in the first week of therapy and fell to 1.71 per 1000 patient days in the second week suggesting that early initiation of antimicrobial therapy dramatically reduces risk of stroke.[11]

Complications

Aortic valve endocarditis complications include congestive heart failure due to valve damage, annular abscess, mycotic aneurysms of the sinus of Valsalva which can result in pericarditis, hemopericardium, and cardiac tamponade, or fistulas to the cardiac chambers.[12] Involvement of the conduction system may cause atrioventricular blocks. Neurologic complications include thromboembolic events and mycotic aneurysms from septic embolization of vegetations.[12] Systemic embolization to other organs, including liver kidneys, and spleen results in end-organ damage.

Deterrence and Patient Education

Early recognition and timely management of infective endocarditis are imperative to ensure optimal clinical outcomes. Patients should receive education regarding the prognosis, risk factors, signs and symptoms, and management aspects of infective endocarditis. 

Enhancing Healthcare Team Outcomes

Aortic valve infective endocarditis is a life-threatening condition with poor prognosis. Despite technological advances over the past few decades, the mortality remains high. Early recognition and prompt institution of antimicrobial therapy can help optimize patient outcomes. A multidisciplinary approach involves physicians, specialists, specialty-trained nurses, and pharmacists, all collaborating across disciplines to achieve optimal patient results. [Level V]


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Aortic Valve Endocarditis - Questions

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A 40-year-old man with a medical history of hypertension, hyperlipidemia and a congenital bicuspid aortic valve being managed for infective endocarditis from methicillin-sensitive Staphylococcus aureus with intravenous nafcillin is seen in follow-up clinic. Physical examination discloses temperature of 37.4 C. Blood pressure is 120/70 mmHg, and pulse rate of 72 per minute. A transthoracic echocardiogram shows a bicuspid aortic valve with small vegetation, now aortic insufficiency. A 12-lead electrocardiogram shows a PR interval of 220 ms, which is increased from his baseline PR interval of 140 ms. Which of the following tests should be done at this point?



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A 40-year-old man with a previous medical history of the congenital bicuspid aortic valve and an episode of infective endocarditis 20 years ago is planning to undergo a dental procedure which will involve dental extraction. He read on the internet that some patients require antibiotic prophylaxis prior to invasive dental procedures. Based on the latest guidelines infective endocarditis prophylaxis is recommended for which of the following conditions?



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A healthy 50-year-old man presents with 4 to 5 days history of fever up to 38.9 C. Physical examination discloses a diastolic murmur on the left parasternal border. Transthoracic echocardiogram demonstrates severe aortic valve regurgitation, but no evidence of vegetations. Two sets of blood cultures return negative. Physical examination demonstrates no immunologic or embolic phenomenon. What is the diagnosis?



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A 70-year-old man with a history of permanent pacemaker implantation for complete heart block 2 years ago presents with fever. Blood cultures are positive for Staphylococcus aureus. Transesophageal echocardiography demonstrates a small vegetation on the aortic valve with no aortic insufficiency and no vegetation of the device leads. Device pocket examination is normal. What is the optimal management of this patient?



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A 40-year-old woman with a history of systemic lupus erythematosus controlled on hydroxychloroquine presents to the emergency department with a fever of 39 C. Physical examination reveals a soft diastolic murmur on the left sternal border. Blood pressure is 120/80 mmHg with a pulse of 76 beats per minute. A transthoracic echocardiogram reveals valve thickening on the arterial side of the aortic valve without any aortic insufficiency. Which of the following is the next best step in the management of this patient?



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Aortic Valve Endocarditis - References

References

Cahill TJ,Prendergast BD, Infective endocarditis. Lancet (London, England). 2016 Feb 27;     [PubMed]
Pant S,Patel NJ,Deshmukh A,Golwala H,Patel N,Badheka A,Hirsch GA,Mehta JL, Trends in infective endocarditis incidence, microbiology, and valve replacement in the United States from 2000 to 2011. Journal of the American College of Cardiology. 2015 May 19;     [PubMed]
Nishimura RA,Otto CM,Bonow RO,Carabello BA,Erwin JP 3rd,Guyton RA,O'Gara PT,Ruiz CE,Skubas NJ,Sorajja P,Sundt TM 3rd,Thomas JD,Anderson JL,Halperin JL,Albert NM,Bozkurt B,Brindis RG,Creager MA,Curtis LH,DeMets D,Guyton RA,Hochman JS,Kovacs RJ,Ohman EM,Pressler SJ,Sellke FW,Shen WK,Stevenson WG,Yancy CW, 2014 AHA/ACC guideline for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. The Journal of thoracic and cardiovascular surgery. 2014 Jul;     [PubMed]
Durack DT,Lukes AS,Bright DK, New criteria for diagnosis of infective endocarditis: utilization of specific echocardiographic findings. Duke Endocarditis Service. The American journal of medicine. 1994 Mar;     [PubMed]
Li JS,Sexton DJ,Mick N,Nettles R,Fowler VG Jr,Ryan T,Bashore T,Corey GR, Proposed modifications to the Duke criteria for the diagnosis of infective endocarditis. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 2000 Apr;     [PubMed]
Wang A,Gaca JG,Chu VH, Management Considerations in Infective Endocarditis: A Review. JAMA. 2018 Jul 3;     [PubMed]
Mylonakis E,Calderwood SB, Infective endocarditis in adults. The New England journal of medicine. 2001 Nov 1;     [PubMed]
Gossman WG,Khalid N, Minimally Invasive Aortic Valve Surgery . 2019 Jan     [PubMed]
Sullam PM,Drake TA,Sande MA, Pathogenesis of endocarditis. The American journal of medicine. 1985 Jun 28     [PubMed]
Baddour LM,Wilson WR,Bayer AS,Fowler VG Jr,Tleyjeh IM,Rybak MJ,Barsic B,Lockhart PB,Gewitz MH,Levison ME,Bolger AF,Steckelberg JM,Baltimore RS,Fink AM,O'Gara P,Taubert KA, Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Complications: A Scientific Statement for Healthcare Professionals From the American Heart Association. Circulation. 2015 Oct 13     [PubMed]
Pettersson GB,Coselli JS,Pettersson GB,Coselli JS,Hussain ST,Griffin B,Blackstone EH,Gordon SM,LeMaire SA,Woc-Colburn LE, 2016 The American Association for Thoracic Surgery (AATS) consensus guidelines: Surgical treatment of infective endocarditis: Executive summary. The Journal of thoracic and cardiovascular surgery. 2017 Jun     [PubMed]
Dickerman SA,Abrutyn E,Barsic B,Bouza E,Cecchi E,Moreno A,Doco-Lecompte T,Eisen DP,Fortes CQ,Fowler VG Jr,Lerakis S,Miro JM,Pappas P,Peterson GE,Rubinstein E,Sexton DJ,Suter F,Tornos P,Verhagen DW,Cabell CH, The relationship between the initiation of antimicrobial therapy and the incidence of stroke in infective endocarditis: an analysis from the ICE Prospective Cohort Study (ICE-PCS). American heart journal. 2007 Dec     [PubMed]

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