Valvular Heart Diseases Include: stenosis, insufficiency (regurgitation orincompetence), or both. Stenosis is failure of a valve to opencompletely, thereby impeding forward flow. Insufficiency, in contrast, results from failureof a valve to close completely, thereby allowingreversed flow. Valvular abnormalities may be caused bycongenital disorders , or by acquired diseases.
Valvular degeneration caused by calcification:Calcific Aortic Stenosis:It is the consequence of calcification owing toprogressive and advanced age-associated"wear and tear“ injuryMorphology:The morphologic hallmark is heaped-up calcified masseswithin the aortic cusps.( a heavily calcified aortic valve removed at the time of surgical valve replacement )
Clinical Features: Cardiac output is maintained by development ofconcentric left ventricular (pressure overload)hypertrophy. The hypertrophied myocardium tends to beischemic and angina pectoris may appear. There may be impairment of both systolic anddiastolic myocardial function, with symptoms of CHF.
Mitral Annular Calcification: Degenerative calcific deposits in fibrous ring(annulus) of mitral valve. Generally does not affect valvular function. However, it may lead to:o regurgitation by interfering with systolic contractionof mitral valve ring.o stenosis by impairing opening of mitral leaflets.o arrhythmias and occasionally sudden death bycalcium deposits penetrating deeply and impinge onatrioventricular conduction system.
Mitral annulus calcification: pathology specimenThis autopsy specimen demonstrates thickened mitral valve leafelts, with marked stenosis.The mitral annulus calcification is seen as pale white lumps under the endothelium aroundthe margins of the valve
Myxomatous degeneration of mitral valve(mitral valve prolapse ): One or both mitral leaflets are "floppy" andprolapse, and balloon back into left atrium duringsystole. Most often in young women.Morphology: Ballooning of mitral leaflets. Leaflets are oftenenlarged, redundant, thick, and rubbery. Chordae tendineae are elongated, thinned, andoccasionally ruptured.
This is floppy mitral valve seen from above (left).
Pathogenesis: There is developmental defect of connective tissueproteins ( structural proteins). So it is a common feature of Marfan syndrome(caused by mutation in gene encoding fibrillin-1 )Clinical Features: Most patients are asymptomatic, discovered onroutine examination by presence of midsystolic click . When mitral regurgitation occurs, there is latesystolic or holosystolic murmur. A minority of patients have chest pain .
Rheumatic fever and Rheumatic heart diseases: : RF is an acute, immunologicallymediated, multisystem inflammatory disease thatoccurs a few weeks following an episode of group Astreptococcal pharyngitis. Acute rheumatic carditis during active phase of RFmay progress to chronic rheumatic heart disease. Chronic valvular deformities characterized bydeforming fibrotic valvular disease (particularlymitral stenosis)
Morphology: Acute RHD: Focal inflammatory lesions called Aschoff bodies( rheumatic granuloma ). Aschoff bodies consist of foci of degenerated collagensurrounded by lymphocytes , occasional plasmacells, and plump macrophages called Anitschkow cells(pathognomonic for RF). Anitschkow cells have abundant cytoplasm andcentral round-to-ovoid nuclei in which chromatin isdisposed as a central slender wavy ribbon (hencedesignation "caterpillar cells"). Some of larger macrophages become multinucleatedto form Aschoff giant cells.
Aschoff bodies may be found in any of three layers ofheart ( pericardium, myocardium, or endocardium )hence the lesion is called pancarditis. Involvement of endocardium and left-sided valvesresults in fibrinoid necrosis within cusps or alongchordae tendineae. On which sit small (1 to 2 mm) vegetations (verrucae)along lines of closure. These warty projections (verrucae) arise fromprecipitation of fibrin at sites of erosion, related tounderlying inflammation and collagen degeneration.
Chronic RHD: Characterized by organization of acute inflammationand subsequent fibrosis. Valvular leaflets become thickened and retracted. Microscopically: diffuse fibrosis andneovascularization that obliterate the originallyavascular leaflet architecture.In chronic rheumatic mitral valvulitis the valve leaflets and chordae tendineaeare thick, rigid, and interadherent.
Pathogenesis: Acute rheumatic fever is a hypersensitivity reactioninduced by group A streptococci. Antibodies directed against M proteins of certainstrains of streptococci, cross-react with glycoproteinantigens in heart, joints, and other tissues. The onset of symptoms 2 to 3 weeks after infectionand the absence of streptococci from the lesionssupport the concept that RF results from an immuneresponse against the offending bacteria.
Clinical Features: RF is characterized by major manifestations:(1) Migratory polyarthritis of large joints.(2) Carditis.(3) Subcutaneous nodules.(4) Erythema marginatum of skin.(5) Sydenham chorea ( neurologic disorder withinvoluntary purposeless, rapid movements ). The diagnosis is established by so-called Jonescriteria: presence of two major manifestations, orone major and two minor manifestations (fever, arthralgia, or elevated blood levels of acutephase reactants-CRP).
Acute RF appears most often in children betweenages 5 and 15 years. 20% of first attacks occur in middle or later life. Although pharyngeal cultures for streptococciare negative by the time the illness begins. Antibodies to one or more streptococcal enzymessuch as (streptolysin O and DNAse B) are presentand can be detected in sera of most patients.
INFECTIVE ENDOCARDITIS (IE ): Characterized by colonization or invasion ofheart valves or endocardium by a microbe. Leading to formation of bulky friable vegetationscomposed of thrombotic debris and organisms. Often associated with destruction of underlyingcardiac tissues. Although fungi, rickettsiae (Q fever), and chlamydiaemay be responsible for these infections, most casesare bacterial (bacterial endocarditis).
Etiology and Pathogenesis: Classified into acute and subacute forms:o Acute endocarditis: destructive infection ofpreviously normal heart valve with a highly virulentorganism (S. aureus ) as in intravenous drug abusers.o Subacute endocarditis: organisms of low virulence(Streptococcus viridans ) cause infection inpreviously deformed valves. Prosthetic valve endocarditis is caused bycoagulase-negative staphylococci ( S. epidermidis).
Morphology: In both subacute and acute forms:friable, bulky, destructive vegetations containingfibrin, inflammatory cells, and bacteria or otherorganisms are present on heart valves . The aortic and mitral valves are most common sitesof infection The vegetations may be single or multiple andmay involve more than one valve. Vegetations sometimes erode into underlyingmyocardium to produce an abscess cavity (ringabscess).
Fungal endocarditis cause large vegetations thandoes bacterial infection. Systemic emboli may occur because of friable natureof vegetations, and may cause infarcts inbrain, kidneys, myocardium, and other tissues. Because embolic fragments contain large numbersof virulent organisms, abscesses often developat sites of such infarcts (septic infarcts). With time: fibrosis, calcification, and chronicinflammatory infiltrate may develop.
Mitral vegetation in a 78-year-old man with infective endocarditis.Intraoperative photograph shows a large vegetation (arrow) adhering toposterior mitral leaflet (arrowhead).
Diagnostic Criteria for Infective EndocarditisPathologic Criteria:Microorganisms, demonstrated by culture or histologic examination, in a vegetation, embolus from avegetation, or intracardiac abscess.Clinical Criteria:Major:-Positive blood culture(s) indicating characteristic organism.Echocardiographic findings ; including valve-related or implant-related mass or abscess, orpartial separation of artificial valve.New valvular regurgitation.Minor:-Predisposing heart lesion or intravenous drug use.Fever.Vascular lesions ; including arterial petechiae, subungual/splinter hemorrhages , emboli, septic infarcts,mycotic aneurysm, intracranial hemorrhage, Janeway lesions.Immunologic phenomena ; including glomerulonephritis, Osler nodes, Roth spots, rheumatoid factor.Microbiologic evidence ; including single culture showing uncharacteristic organism.Echocardiographic findings consistent with but not diagnostic of endocarditis ; including new valvularregurgitation, pericarditis.
Diagnosis by Duke Criteria requires pathologicor clinical criteria. If clinical criteria are used: 2 major, or1 major + 3 minor, or 5 minor criteria . Janeway lesions: small erythematous lesions onpalms and soles. Osler nodes: small subcutaneous nodules in pulpof digits. Roth spots: oval retinal hemorrhages with palecenters. Prevention of IE : by prophylactic antibiotics inpatient with cardiac anomaly or artificial valve whohave a dental, surgical, or other invasive procedure.
Nonbacterial Thrombotic Endocarditis (NBTE): characterized by deposition of small masses(1 to 5 mm) of fibrin, platelets, and other bloodcomponents on leaflets of cardiac valves. In contrast to vegetations of IE, valvular lesions ofNBTE are nondestructive, sterile (do not containmicroorganisms). NBTE is often encountered in debilitatedpatients, such as those with cancer or sepsis (hencepreviously termed marantic endocarditis). NBTE may producing emboli and resultant infarctsin brain, heart, or elsewhere.