Cardiac Pathology

• Pathology of heart valve disease:

  • Calcific valve disease - most prevalent heart valve disease - normal anatomy of the heart valve is distorted by calcified tissue in the intima of the valve so that it cannot function physiologically correctly - it's a degenerative process
  • Features of calcific heart disease:
  • Aortic stenosis
  • Mitral valve annulus calcification
  • Prosthetic tissue based valves may calcify
• Pathology of heart valve disease:

  • Bicuspid valve disease - congenital disorder - normal 3 cusp structure is lost and replaced by just 2 cusps - so cusps become distorted and don't function properly
  • Mitral valve prolapse
  • Functional valve disorders - cause turbulence of the blood
  • Systemic inflammatory disorders - eg systemic lupus erythematosus (inflammation can affect the heart valves, which can lead on to calcific valve disease)
  • Rheumatic heart disease
  • Infective endocarditis
• Rheumatic fever is a condition which can occur 2-3 weeks after a streptococcal URTI (upper respiratory tract infection). Predominantly a childhood disorder. Occurs mainly nowadays in Central Africa, Middle East & India - associated with poor nutrition and overcrowding. Self-limiting disease, often characterised by recurrent attacks.
• Inflammation occurs at multiple sites in rheumatic fever (an autoimmune disorder):

  • Heart
  • Rheumatic heart disease
  • Endocarditis (lining of heart is inflamed)
  • Myocarditis (Aschoff bodies form - inflammation within cardiac muscle)
  • Pericarditis
  • Arteries
  • Arteritis
  • Joints
  • Flitting polyarthritis - inflammation of joints
  • Skin
  • Erythema marginatum rash
  • Other skin rashes
  • Subcutaneous nodules
• Pathogenesis of rheumatic fever:

  • Bacterial culture of affected tissues negative (no microorganisms in heart valve)
  • Antibodies form in relation to streptococcal polysaccharide
  • Antistreptolylin O titres (ASOT) raised in rheumatic fever - how you test for it
  • Antibodies cross-react with cardiac antigens
• • Child has a sore throat due to beta-haemolytic streptococcus
  • That will travel to a lymph node where there will be an immune response
  • Antibodies will be generated against the beta-haemolytic streptococcus
  • These then cross react with the heart valves giving vegetations, with the cardiac muscle giving collections of macrophages within it (Aschoff bodies) and may form fibrinous pericarditis

  
• Repeated episodes of rheumatic fever can lead to:

  • Fibrosis of endocardium & valves
  • Vegetations developing on heart valve leaflets made of platelets and fibrin (no microorganisms - sterile - result of antibody cross reaction causing inflammation of the heart valve leaflets)
  • Fusion of heart valve leaflets would then result
  • And ultimately distortion and calcification of heart valves
  • Mitral valve most commonly affected  - 90% - leads to mitral stenosis and incompetence
  • Aortic valve less commonly affected - 40% - leads to aortic stenosis and incompetence
• Infective endocarditis is an acute or chronic disease resulting from infection of a focal area of the endocardium.
• Infective endocarditis sites:

  • Heart valve - most common
  • Mural endocardium - particularly if a myocardial infarct has taken place resulting in damage to the endocardium lining the heart chambers
  • Congenital defect in the heart lining
• Heart valve disease, damage to the endocardium and congenital defects create areas of susceptibility in the cardiac endothelium where bacteria can lodge. To have endocarditis, you need some predisposing areas or defects in the heart endothelium where bacteria can land and lodge.
• Source of microorganism for infective endocarditis: most often arise from normal flora causing bacteraemia (the passive transfer of bacteria in the bloodstream). Sites:

  • Oropharynx - streptococci (Strep. viridans)
  • Skin - staphylococci, candida fungi, venepuncture, cannulation, surgery
  • GIT - Strep. faecalis, colonoscopy, surgery
  • GUT - Strep. faecalis, cytoscopy, surgery
• Disorders that predispose to infective endocarditis:

  • Acquired valvular heart disease with stenosis or regurgitation
  • Hypertrophic cardiomyopathy (heart is enlarged)
  • Previous infective endocarditis
  • Structural congenital heart disease, including surgically corrected or palliated structural conditions, but excluding isolated atrial septal defect, fully repaired ventricular septal defect or fully repaired patent ductus arteriosus, and closure devices that are judged to be endothelialised
  • Valve replacement
• Pathogenesis of infective endocarditis:

  • Focal area of abnormal endocardium
  • Valves or cordae tendineae are particular targets
  • Platelet and fibrin deposition (vegetation) creates a site where bacteria/fungi can land
  • Bacteraemia (circulation of organisms)
  • Bacteria land on and colonise vegetation
  • Blanket of platelets and fibrin fall over those - thickening the vegetation
  • Bacteria proliferate
  • Vegetation grows
  • Small nodule -> large friable mass
• Local effects of infective endocarditis:

  • Valve incompetence - doesn't work v well - regurgitation
  • Perforation of valve leaflets
  • Rupture of cordae tendinae - causes valves to then prolapse
  • Myocarditis
  • Embolism of coronary vessels when bacterial colonies break up
• Systemic effects of infective endocarditis:

  • Fever, weight loss & malaise
  • Splenomegaly
  • Embolism (passive transfer of material in the blood that will eventually lodge somewhere - in this case the embolus will be bacterial, so we may see local infections resulting from the embolism)
  • Most visible signs are from embolism - may see:
  • Abscesses occurring in the spleen, kidney or brain
  • Haemorrhages of skin & nail bed, or mucous membranes or retina
  • Glomerulonephritis
  • Finger clubbing
• Diagnosis of infective endocarditis:

  • Auscultation - because may get abnormal heart sounds
  • Blood tests - FBC (full blood count), ESR (erythrocyte sedimentation rate)
  • Blood cultures
  • Echocardiogram
  • Electrocardiogram
  • CT/MRI imaging of heart
• Treatment of infective endocarditis:

  • Antibiotics
  • Surgical removal of the valve and replacement with a prosthetic one
• Antibiotic prophylaxis for infective endocarditis:

  • Antibiotics are not needed before dental work in any patients with native valve disease who have not undergone either valve replacement or repair
  • There is controversy over high-risk patients with previous infective endocarditis and replacement heart valves or valve repair surgery
• Antibiotic prophylaxis for infective endocarditis:

  • Although the National Institute for Health and Care Excellence (NICE) does not recommend antibiotics in these high-risk patients, all international guidelines do and most cardiologists and cardiac surgeons follow these rather than NICE
  • Dental surveillace and optimal oral hygiene should be encouraged in all patients with native or operated heart valve disease