Prosthetic Valve Endocarditis - Causes, Symptoms, and Treatment

What Is Prosthetic Valve Endocarditis?

Prosthetic valve endocarditis is a condition caused by microbial infection of the prosthetic valves of the heart. It is considered one of the most severe forms of infective endocarditis. This bacterial infection affects around 20 % of the population at risk. Based on the stages when the individual is affected post-operatively, the condition is classified as follows:

• Early Prosthetic Valve Endocarditis: The infection is acquired within a year of surgery.

• Late Prosthetic Valve Endocarditis: An individual is infected after a year of valve replacement surgery.

The microorganisms which affect early and late stages differ. Thus, the classification proves helpful.

How Is Prosthetic Valve Endocarditis Caused?

Prosthetic valve endocarditis is a condition caused by microbial infection. Depending on the period and place of contamination of the prosthetic valves, various microbes account for the disease. Common pathogens involved during the course of the disease include

• Staphylococcus aureus.

• Coagulase-negative staphylococci.

• Streptococcus.

• Enterococcus.

• Staphylococcus epidermidis.

Based on the microorganism cultured from the site of infection, the form of prosthetic valve endocarditis can be identified as follows:

• When infected during the surgery or within a few hours to days of surgery, the patients form a paravalvular abscess (infective necrosis of the valves). The bacteria associated with early prosthetic valve endocarditis is a Staphylococcus aureus (the most common infective organism). Other microbes involved include coagulase-negative staphylococci, gram-negative bacilli, and Candida species.

• During the second month to about a year, if a person is infected, the infection is acquired through nosocomial (hospital-acquired) or community spread. Bacteria commonly cause infection the second month after surgery or within a year. Common bacteria involved include Streptococcus, Staphylococcus aureus, and coagulase-negative Staphylococcus. One rarely found bacteria are Enterococcus.

In cases with late prosthetic valve endocarditis, the infection is commonly infected by Streptococci and S. aureus and less commonly by coagulase-negative Staphylococci and Enterococci.

What Are the Symptoms of Prosthetic Valve Endocarditis?

Prosthetic valve endocarditis can be manifested clinically based on the symptoms presented by the patients, which are as follows:

• Fever.

• Breathlessness.

• Pleuritic chest pain.

• Anorexia.

• Weight Loss.

• Headache.

• Myalgia.

• Arthralgia.

• Night sweats.

• Abdominal pain.

• Cough.

• Cardiac murmurs

• Splenomegaly.

Some other symptoms which are less commonly observed:

• Petechiae: These are the dermatological findings; these blue, purple spots are observed on the extremities, palate (roof of the mouth), and conjunctivae of the eyes. These lesions are seen in 40 % of the patients.

• Splinter Hemorrhages: These are the lesions found on the nail beds, appear as red-brown lines, and do not blanch on pressure.

• Janeway Lesions: These lesions are erythematous macules on the palms and soles.

• Osler Nodes: These subcutaneous violaceous nodules are mostly on the pads of the fingers and toes.

• Roth Spots: They are exudative, edematous hemorrhagic retina lesions with pale centers.

How Is Prosthetic Valve Endocarditis Diagnosed?

Following are the diagnostic test that helps in diagnosing and determining Prosthetic valve endocarditis:

• Blood Investigations: Blood samples are collected from three different sites; blood cultures help determine the causative bacteria. Modified Duke's criteria are used to confirm the diagnosis.

• Transesophageal Echo (TEE): It is also used as a diagnostic test. This diagnostic test helps in identifying vegetation, determining the valve dysfunction, identifying the extent of infection in the periprosthetic area, determining the prognosis of the disease and scheduling and planning for surgery, and noting the improvement in the condition postoperatively.

• Chest X-Ray: X-ray is ordered to evaluate lungs.

• Cardiac Computed Tomography Angiogram CTA: The patients who cannot be diagnosed by transesophageal echo undergo a cardiac computed tomography angiogram to confirm the diagnosis. This is generally performed in suspected cases or patients with a history of previous bacteremia (bacteria in the blood culture).

• 18F-FDG PET/CT: It is an effective diagnostic method that helps monitor progress after treatment.

• Magnetic Resonance Imaging (MRI): MRI is advised to determine the spread and damage in severe cases where the emboli reach the brain.

What Is the Differential Diagnosis of Prosthetic Valve Endocarditis?

Some other conditions that have a similar presentation as that of Prosthetic valve endocarditis are:

• Native valve endocarditis.

• Atrial myxoma.

• Libman-Sacks endocarditis.

• Nonbacterial thrombotic endocarditis (NBTE).

• Rheumatic fever.

How Is Prosthetic Valve Endocarditis Treated?

Management of Prosthetic valve endocarditis can be categorized as follows:

Medicinal Treatment:

Antibiotics are used in the treatment. The choice of drug depends on the causative bacteria. Antibiotic therapy is started after confirming the condition's cause by collecting reports of at least three samples from different sites.

Therapy for Patients with Infection Due to Gram-Positive Cocci:

• Oxacillin for six weeks, Rifampin for six weeks, Gentamicin for two weeks,

• Cefazolin or Cefotaxime for six weeks, Rifampin for six weeks, and Gentamicin for two weeks.

• Vancomycin for six weeks, Rifampin for six weeks, and two weeks of Gentamicin.

Prosthetic Valve Endocarditis Due to Streptococcus:

• Penicillin G, Ceftriaxone, or Amoxicillin is prescribed for six weeks. For patients allergic to Penicillin, Vancomycin is prescribed for six weeks.

Prosthetic Valve Endocarditis Due to Enterococcus:

• Ampicillin + Ceftriaxone for six weeks.

• Amoxicillin + Gentamicin for four to six weeks.

• Vancomycin + Gentamicin for six weeks.

Therapy for Critically Ill Patients Whose Reports for Labs Are Due:

• Ampicillin + Gentamicin + Flucloxacillin or Oxacillin

• Vancomycin + Gentamicin (if allergic to Penicillin)

• Vancomycin + Gentamicin + Rifampin if early prosthetic valve endocarditis (under one year) or healthcare-associated endocarditis.

Surgical Treatment:

Surgical intervention is required if:

• Antibiotics are ineffective even when taken for five to seven days.

• Severe prosthetic valve abnormality.

• Development of abscess or penetrating lesions.

• Patients who develop heart failure.

Early surgical interventions help prevent mortality; even after surgery, antibiotic prophylaxis is recommended for six weeks.

What Are the Complications of Prosthetic Valve Endocarditis?

• Prosthetic valve endocarditis affects all body systems, but the most common complications are seen in the cardiac system, resulting in heart failure. Heart failure is the most common cardiac complication.

• Non-cardiac complications include metastatic abscess formation or a mycotic aneurysm.

• Nephritic complications include renal abscess, glomerulonephritis, and acute renal failure.

Conclusion:

Prosthetic valve endocarditis is a condition caused by bacterial infection of the prosthetic valve. The bacteria can infect during surgery or after the surgery. The condition can be treated if diagnosed early. The cases which are misdiagnosed or become severe can be fatal.