What does SVEs (Subacute Viral Endocarditis) mean in a medical context?

Subacute Bacterial Endocarditis (SBE): Definition and Clinical Significance

SVE (Subacute Bacterial Endocarditis) is an infection of the heart's endocardial surface that develops gradually over weeks to months, primarily caused by less virulent organisms like viridans streptococci, and characterized by indolent symptoms including low-grade fever, fatigue, and weight loss. 1, 2

Etiology and Microbiology

• Subacute bacterial endocarditis is most commonly caused by viridans group streptococci, including Streptococcus sanguis, S. oralis, S. salivarius, S. mutans, and Gemella morbillorum 1
• Less commonly, it may be caused by Staphylococcus epidermidis, fastidious Haemophilus species, and other organisms with lower virulence 1
• Typically develops on abnormal or damaged heart valves after asymptomatic bacteremia from infected gums or the genitourinary/gastrointestinal tract 1

Clinical Presentation

• Presents as an indolent, gradually progressive infection with symptoms developing over weeks to months 1, 2
• Common symptoms include:
  • Low-grade fever
  • Fatigue and malaise
  • Unexpected weight loss
  • Night sweats
  • Heart murmurs (new or changing) 1, 3
• May present with various non-specific symptoms that can confuse initial assessment, leading to delayed diagnosis 1, 4

Risk Factors

• Pre-existing cardiac abnormalities (most common):
  • Mitral valve prolapse
  • Bicuspid aortic valve
  • Rheumatic heart disease
  • Congenital heart defects 5, 6, 3
• Dental procedures without appropriate antibiotic prophylaxis in high-risk patients 5
• Poor dental hygiene 1
• Advanced age 1

Diagnosis

• Blood cultures are the cornerstone of diagnosis, with multiple sets recommended to increase yield 1
• Echocardiography is essential:
  • Transthoracic echocardiography (TTE) is recommended as first-line imaging 1
  • Transesophageal echocardiography (TEE) should be performed when clinical suspicion remains high despite negative TTE 1
• Modified Duke criteria are used for definitive diagnosis, incorporating clinical, microbiological, and imaging findings 1

Complications

• Embolic events (cerebral, renal, splenic, coronary, peripheral) 5, 6
• Valvular destruction leading to heart failure 1
• Perivalvular abscess formation 1
• Conduction abnormalities (heart block) when infection extends into the cardiac conduction system 1
• Cerebrovascular accidents (strokes) from septic emboli 5, 4

Treatment

• Antimicrobial therapy:
  • For viridans streptococci: Penicillin or ceftriaxone for 4-6 weeks, sometimes with synergistic aminoglycoside in the first 2 weeks 1, 7
  • For culture-negative cases with subacute presentation: Coverage for S. aureus, viridans group streptococci, HACEK organisms, and enterococci is reasonable 1
• Surgical intervention is indicated for:
  • Heart failure due to valve dysfunction
  • Uncontrolled infection (abscess, enlarging vegetation)
  • Prevention of embolism with large vegetations (>10mm) 1
• Monitoring should include regular clinical assessment and echocardiographic follow-up 1, 7

Prognosis

• Untreated endocarditis is almost always fatal 1
• With appropriate antimicrobial therapy, prognosis is generally good for uncomplicated cases 1, 7
• Poor prognostic factors include:
  • Development of cardiac rhythm disturbances 1
  • Heart failure 1
  • Neurological complications 5, 4
  • Perivalvular extension of infection 1

Differentiation from Acute Bacterial Endocarditis

• Acute bacterial endocarditis:
  • Develops rapidly (days)
  • Typically caused by more virulent organisms (S. aureus, group A hemolytic streptococci)
  • Can develop on normal valves
  • Presents with high fever, toxic appearance, and rapid valve destruction 1
• Subacute bacterial endocarditis:
  • Develops gradually (weeks to months)
  • Caused by less virulent organisms
  • Usually requires abnormal valves
  • Presents with indolent symptoms and gradual valve damage 1, 2

Prevention

• Antibiotic prophylaxis is no longer universally recommended for all patients with valvular heart disease undergoing dental procedures, but should be considered for highest-risk patients 5, 6
• Good oral hygiene and regular dental care are important preventive measures 1
• Prompt treatment of bacteremia from any source is essential 4