Cardiovascular Pathology


May be asymptomatic or minimally symptomatic

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May be asymptomatic or minimally symptomatic

  • May rapidly develop heart failure, arrhythmias, or may cause sudden death

  • There may be a murmur due to cardiac dilatation causing mitral regurgitation

  • May heal completely, or may progress to dilated cardiomyopathy years later

    Notes:

    Grossly, hearts with active myocarditis are described as soft and flabby. The myocardium may be mottled and the heart may be dilated. Microscopically, viral myocarditis is characterized by a (nonspecific) lymphocytic infiltrate with myocyte necrosis.



    Chagasic Myocarditis




    • Chagas disease – the protozoan bug is Trypanosoma cruzi

    • Important in South America – 80% with heart involvement – may be lethal or may go into chronic phase

    • Transmitted by insects such as reduvid bug

    • Microscopically see parasites within myocytes and mixed inflammation

    Note:

    T. Cruzi may also cause destruction of the myenteric plexus of the esophagus, duodenum, colon and ureter with subsequent dilatation of these viscera (megacolon).




    Giant Cell Myocarditis




    • Has a rapid onset with a poor prognosis

    • Microscopically see myocardial necrosis with lymphocytes, plasma cells, eosinophils and giant cells

    • Has some overlap with sarcoidosis, but sarcoidosis has a more insidious onset

    • Some patients may recover completely or with some myocardial fibrosis

    • Etiology is unknown




    Hypersensitivity Myocarditis




    • Due to hypersensitivity reaction to drugs such as methyldopa, sulfonamides

    • Microscopically see interstitial inflammatory infiltrates, mainly perivascular, with lymphocytes, macrophages, and lots of eosinophils




    Some Causes of Metabolic Myocardial Injury



    • Iron overload (hemochromatosis)

    • Hyperthyroidism  tachycardia, palpitations, cardiomegaly, sometimes arrhythmias

    • Hypothyroidism   stroke volume & rate, sluggish flow, may get myxedema of heart

    • Disorders of energy use (carnitine def, FOX disorders, mitochondrial disorders)

    Note:

    Iron accumulates in cardiac myocytes and interferes with metal dependent enzyme systems.

    Hypothyroidism may cause myxedema of the heart with myofiber swelling, basophilic change, loss of cross striations, and increased mucopolysaccharide content of the interstitium.

    Some disorders of energy metabolism can cause death in infancy and be confused with SIDS (example LCHAD deficiency).



    Cardiomyopathy




    • Originally defined as a “primary” abnormality of the myocardium, i.e. cause unknown (not always true now)

    • Excludes so-called “ischemic” CM

    • CM may be divided into three classic clinical/functional/pathologic patterns:

    • Dilated CM – most common ~ 90%

    • Hypertrophic CM

    • Restrictive – rarest




    Dilated Cardiomyopathy




    • Features a rounded, dilated heart (esp LV) which also usually is hypertrophied

    • The heart is hypocontractile  CHF

    • Poor prognosis, 50% mortality in 2 years

    • May affect any age

    • May be treated by cardiac transplant

    • A variant is arrhythmogenic right ventricular dysplasia (cardiomyopathy) – a heritable defect that causes heart failure and may cause sudden death in young persons (see Robbins text)

    Note:

    Dilated CM is also known as congestive cardiomyopathy. Dilated CM may cause death either by heart failure or arrhythmia.




    Causes of Dilated CM



    • Burned out myocarditis

    • EtOH or other toxicity

    • Peripartum CM occurs late in pregnancy or several weeks to months postpartum – poorly understood – possibly related to circulating anti-angiogenic factors

    • Genetic – 30% to 50% of cases, variable inheritance, mostly autosomal dominant, & variable defects - one is abnormal cytoskeletal protein like Duchenne & Becker muscular dystrophy

    • Mostly the cause is unknown

    Notes:

    The progression from viral myocarditis to dilated cardiomyopathy has been demonstrated by serial myocardial biopsies. However, in most cases of DCM, the heart shows little or no residual inflammation.

    Toxic causes of DCM are hard to prove – no good way to tell apart from other DCM.

    The etiology of peripartum CM may be multifactorial, including factors such as hypertension, volume overload, poor nutrition, possible metabolic abnormalities or autoimmune phenomena; recent evidence suggests that it may be related to circulating anti-angiogenic factors (see Robbins text).



    Morphology of Dilated CM




    • Rounded, dilated heart, 2 –3x expected weight

    • LV wall may be thinner due to dilatation

    • May see endocardial fibrosis, may see mural thrombus in chambers

    • Coronary arteries OK

    • Valves OK, but possible regurg of AV valves due to annulus dilatation

    • Histology not too exciting – myocyte hypertrophy, some interstitial fibrosis, rarely some residual myocarditis




    Hypertrophic Cardiomyopathy



    • Has many names:

      • Idiopathic hypertrophic subaortic stenosis

      • Hypertrophic obstructive cardiomyopathy

      • Asymmetric septal hypertrophy

    • Features a heart that is normal in shape, but with marked wall thickening due to hypertrophy (esp LV) often with asymmetric thickening of the septum and narrowing of the LV cavity

    • The heart is hypercontractile without LV cavity dilatation

    • The problem is diastolic filling and LVOT obstruction

    • Has a better prognosis than DCM, but may cause angina, CHF, A-fib, mural thrombus, infective endocarditis of MV

    • Can affect children or adults

    • HCM is one of the most common causes of sudden death in young athletes

    Notes:

    The septum may bulge into the left ventricular outflow tract. This acts in concert with the adjacent anterior leaflet of the mitral valve to produce left ventricular outflow tract obstruction. A harsh systolic ejection murmur may be present.

    Late cardiac dilatation in the course of HCM may actually relieve the LVOT obstruction.

    To diagnose HCM, it is necessary to rule out other causes of myocardial hypertrophy such as hypertension and aortic stenosis.

    Sudden death may be due to blockage of the left ventricular outflow by the anterior leaflet of the mitral valve. The leaflet may be sucked into the LVOT by “venturi” action of the blood flowing through the narrowed passage.

    HCM can be managed medically better than DCM.



    Causes of Hypertrophic CM




    • Has a genetic basis in all cases. Most are familial and typically autosomal dominant with variable expression; the rest are sporadic

    • Often genetic errors are in coding for contractile proteins; >100 mutations known

    • Newer evidence suggests that HCM may arise from a defect in energy transfer from mitochondria to sarcomeres

    • Investigation of family members of patients with HCM is indicated.




    Morphology of Hypertrophic CM




    • Thickened LV wall at the expense of the cavity, often with asymmetric septal thickening and bulge of septum into LVOT

    • Heart may be normal in shape (may look normal on a routine chest X-ray), but 2-3x expected weight

    • Anterior leaflet of MV is thickened, and there may be a “friction lesion” on the LVOT

    • Histology shows myocyte hypertrophy, some interstitial fibrosis, and sometimes myofiber disarray, especially in septum

    Note:

    Myofibrillar disarray within cardiac myocytes in HCM can be seen with electron microscopy.




    Restrictive Cardiomyopathy




    • This is a disorder of ventricular compliance – The heart is normal in shape but stiff

    • Constrictive pericarditis is clinically similar – heart is mechanically prevented from contracting well




    Causes of Restrictive CM



    • Things that infiltrate and stiffen the myocardium:

      • Amyloidosis

      • Sarcoidosis

      • Metastatic tumor

      • Some storage diseases

      • Endomyocardial fibrosis (a tropical disease of unknown cause)



    • Things that thicken and stiffen the myocardium and endocardium:

      • Endocardial fibroelastosis (in children - occurs with some types of congenital heart disease and rarely occurs alone)

      • Loeffler endomyocarditis (assoc. with eosinophilia or eosinophilic leukemia)

      • Endomyocardial fibrosis (a tropical disease of unknown cause)

    • Idiopathic restrictive CM – myocardium shows patchy or diffuse fibrosis

    Note:

    In RCM the heart is about normal size and the myocardium is firm (“waxy” in amyloidosis).




    Cardiac Transplantation




    • ~2500/year worldwide; ~7 in 2013 at Riley

    • Acute cellular rejection is a form of lymphocytic myocarditis – controllable with drugs

    • Transplant arteriopathy is a long term complication (aka graft vascular disease, graft arteriosclerosis) – years to a decade or more – may cause sudden death

    Note:

    Acute cellular rejection is cell mediated and is controllable by drugs such as cyclosporine. Transplant vasculopathy on the other hand, may be mediated more by humoral means, and as yet is not controllable by drugs.



    Congenital Heart Disease (CHD)



    • Def: Abnormality of heart or great vessels present at birth (although may be discovered as an adult)

    • Usually refers to structural abnormalities such as abnormal chamber and vessel relationships, abnormal connections (holes), obstructions, absence or maldevelopment of structures, and other anatomic abnormalities

    • By convention, usually does not include congenital tumors, infections, cardiomyopathies

    • Ranges from trivial (bicuspid aortic valve) to lethal (absent left ventricle)

    • If severe, causes delayed development, failure to thrive, increased susceptibility to infectious diseases in childhood, cardiac failure, and rarely sudden cardiac death

    • Increased risk for endocarditis (generally true for any structural abnormality, congenital or acquired; i.e. prosthetic valve)

    • Increased risk during pregnancy for women with CHD

    • Hyperviscosity due to polycythemia

    • Nearly twice as many children die from CHD in the U.S. as from all forms of childhood cancer combined (Am. Heart Association, 2005)




    Causes of CHD




    • Usually unknown - probably multifactorial (may see discordance of CHD in identical twins!)

    • Around 5% chromosomal (Trisomies, Turner’s)

    • A major known cause is sporadic genetic abnormalities such as single gene mutations or small chromosomal losses (examples include Noonans, DiGeorge, numerous others)

    • May be seen in many malformation associations (VATER, polysplenia)

    • Rare infectious cause (rubella)

    Note: Robbins 9th edition has a good overview on gene defects that cause congenital heart defects (p. 532)

    Major CHD Defects Can Be Lumped into 3 Categories




    • Cyanotic - when blood from the right side of the heart (deoxygenated blood) enters the left side without going through the lungs (right to left shunt)

    • Noncyanotic - when blood from the left side of the heart enters the right side (left to right shunt)

    • “Other” (i.e. no shunts, example - obstructions)




    Right to Left Shunts




    • Cause cyanosis from early infancy (blue baby)

    • May be complicated by paradoxical emboli




    Left to Right Shunts



    • No (initial) cyanosis (pink baby)

    • Causes pressure (or volume) overload of the pulmonary circulation

    • Eventually can reverse shunt direction and become cyanotic (see below)



    Eisenmenger’s Syndrome




    • Is a switch from noncyanotic to cyanotic CHD due to reversal of shunt flow

    • Due to right ventricular hypertrophy and pulmonary vascular changes after prolonged pulmonary HTN

    • Too late to surgically repair since pulmonary vascular changes become irreversible

    • Not the same as Eisenmenger’s complex




    CHD with Right to Left Shunt (Cyanotic)




    • Tricuspid Atresia

    • TAPVR (TAPVC)

    • TOGV

    • Truncus Arteriosus

    • Tetralogy of Fallot (if sufficient pulmonary outflow restriction)

    • Hypoplastic left heart syndrome probably should be considered as cyanotic

    Note: All the cyanotic types start with a T except the last one.



    CHD with Left to Right Shunt (Noncyanotic)




    • ASD (increased pulmonary blood volume more than pressure)

    • VSD

    • AV septal defect (AV canal)

    • PDA

    Note: All the noncyanotic types have a D.




    Atrial Septal Defect (ASD)




    • 90% are “secundum” (at foramen ovale) - the rest are rare

    • Not the same as patent FO (present in up to 1/3 of normals)

    • Shunts left to right (noncyanotic)

    • May be asymptomatic for a long time (30 yo) or a life time

    • Increased lung volume of flow more than pressure

    • May eventually get volume hypertrophy of right ventricle, <10% develop irreversible pulmonary HTN

    Ventricular Septal Defect (VSD)



    • Most common cardiac anomaly

    • Frequently associated with other cardiac defects - about 30% isolated

    • Shunts left to right (noncyanotic) initially

    • About 90% involve membranous septum, others in muscular septum or below pulmonic valve

    • Small defects - well tolerated, may close spontaneously

    • Large defects - usually don’t close, and over time  Eisenmenger’s

    • Large defects - may have pulmonary hypertension and right ventricular hypertrophy even at birth

    • Large subaortic defects – may cause prolapse and insufficiency of aortic valve




    Tetralogy of Fallot (TOF) Four Cardinal Features



    1. RVOT obstruction (subpulmonic or valvular)

    2. VSD

    3. Overriding Aorta

    4. RV Hypertrophy - boot shaped heart

    • Most common cyanotic CHD

    • Sometimes ASD too (pentalogy)

    • Basic lesion is anterosuperior displacement of infundibular septum

    • May shunt either way depending on RVOT obstruction, but most are cyanotic from birth or soon after




      • Treated initially by systemic-to-pulmonic surgical shunt ( Blalock -Taussig) to direct more blood to lungs

      • Even untreated, may survive to adulthood (if PS not too bad)

      • May have paroxysmal hypoxemic spells (“tet” spells)




    Hypoplastic Left Heart Syndrome (HLHS)




    • Term for lesions that cause under-development (hypoplasia) of the left ventricle and ascending aorta

    • Significant aortic valvular stenosis or atresia are the usual causes (but not known what causes valve stenoses)

    • HLHS is surgically treatable by the Norwood procedure, but HLHS is a common indication for cardiac transplants in infants

    • The heart grossly appears to be “all right ventricle” with the left ventricle very small, sometimes slit-like or undetectable

    • The left ventricle may show thick endocardial fibroelastosis (EFE) due to high intraventricular pressure

    • Infants are dependent on the ductus after birth, and also need an “ASD” to shunt left atrial blood to the right

    Rev. 12/2013


    Appendix I – Rheumatic Fever Pearls



    • The interval between group A strep pharyngitis and RF = 1 to 5 weeks – average is about 3 weeks




    • Acute RF and poststreptococcal glomerulonephritis usually do not coexist




    • Severity of joint involvement is inversely proportional to heart involvement




    • In acute RF, heart involvement is typically not symptomatic unless there is heart failure or pericarditis




    • Mitral regurgitation may develop quickly (due to restricted mobility of leaflets or ventricular dilatation), but stenosis takes years




    • Sydenham’s chorea – a late manifestation of RF, female > male

      • May last for a week to >2 years!

      • Chorea is never seen with arthritis, but may coexist with carditis

      • Hypotonia and emotional disturbances are typical




    • PANDAS (pediatric autoimmune neuropsychiatric disorders associated with streptococcus) (see Wall Street Journal, December 13, 2011)

      • Includes obsessive compulsive disorder, tics, anxiety, irritability, hyperactivity, anorexia and urinary problems

      • May resolve with antibiotics, but may return & worsen if exposed to strep again

      • May be a version of Sydenham’s




    • Subcutaneous nodules – attached to tendon sheaths – extensor surfaces & over bony prominences of upper & lower extremities & mastoid. Histologically → Aschoff bodies




    • Erythema marginatum – red margin progresses as center clears, see on trunk and proximal limbs


    • RF complications may include pleural pain, pneumonia, abdominal pain, and appendicitis secondary to vasculitis



    Appendix II – Kawasaki Syndrome (Mucocutaneous Lymph Node Syndrome)


    • Kawasaki syndrome is rare, but it is the leading cause of acquired heart disease in children in the United States (great exam question?).




    • Kawasaki syndrome is an arteritis involving medium and small arteries, often unfortunately the coronary arteries.




    • The mucocutaneous lymph node syndrome in children is manifested by fever, conjunctival and oral erythema and erosion, erythema of the palms and soles, a skin rash often with desquamation, and enlargement of the cervical lymph nodes. It is usually self-limited.




    • Approximately 20% develop cardiovascular sequelae ranging from coronary artery ectasia to aneurysm formation to giant (>7 to 8 mm) aneurysm formation.




    • Death may occur in the acute phase of the disease or shortly thereafter due to coronary artery rupture or thrombosis, or aneurysms may persist after resolution of the acute disease and cause death years later.




    • The cause of Kawasaki’s is unknown, but it is probably a form of autoimmunity triggered by a variety of infections, most likely viral, in genetically susceptible individuals.






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