Chapter 18 part 2

Endocardial and Valvular Diseases

• Endocardial and valvular structures may be damaged by:
  • Inflammation and scarring
  • Calcification
  • Congenital malformations
• These damages cause altered hemodynamics of the heart and increase myocardial workload.

Stenosis and Regurgitation

• Stenosis: Failure of the valve to open completely results in extra pressure work for the heart.
• Regurgitation: Inability of a valve to close completely results in extra volume work for the heart.

Mitral Valve Prolapse (MVP)

• Degeneration of the mitral valve.
• Associated with connective tissue disorders: Marfan syndrome and Scoliosis.
• The valve becomes "floppy."
• Incidence: 3%, higher in females than males (F>>M).
• Easily detected on echocardiogram.

MVP: Clinical Features

• Usually asymptomatic.
• Mid-systolic "click" may be audible.
• Holosystolic murmur if regurgitation is present.
• Occasional chest pain, dyspnea.
• Potential complications: 3% risk of infective endocarditis, mitral insufficiency, and arrhythmias.

Artificial Valves

• Mechanical valves.
• Xenografts (porcine).
• 60% of xenografts have complications within 10 years.

Acute Rheumatic Fever and Rheumatic Heart Disease

• Rheumatic fever is a diffuse, inflammatory disease caused by a delayed immune response to infection by group A beta-hemolytic streptococci.
• Presents as a febrile illness.
• Characterized by inflammation of the joints, skin, nervous system, and heart.
• If left untreated, rheumatic fever causes rheumatic heart disease.

Jones Criteria for Acute Rheumatic Fever

• Diagnosis requires two major criteria, or one major and two minor criteria, along with evidence of a previous strep infection.
  • Major Criteria:
    • C: Carditis
    • A: Migratory polyarthritis
    • N: Nodules (subcutaneous)
    • C: Sydenham chorea
    • ER: Erythema marginatum

Rheumatic Heart Disease

• Acute inflammatory disease that follows infection with group A β-hemolytic streptococci.
• Antibodies against streptococcal antigens damage connective tissue in joints, heart, and skin.
• Occurs mainly in children.
• Can lead to:
  • Mitral valve stenosis
  • Rheumatic mitral valvulitis

Infective Endocarditis

• Invasion and colonization of endocardial structures by microorganisms, resulting in inflammation.
• Most common bacteria:
  • Usually Streptococcus
  • Sometimes Staphylococcus

Endocarditis: Etiology and Pathogenesis

• Inflammation of the endocardium.
• Agents: Bacteria, viruses, fungi, rickettsiae, and parasites.
• Predisposing factors: Hypercoagulable states and inflammatory conditions (SLE).
• Pathogenesis:
  • "Prepared" endocardium
  • Blood-borne microorganism adherence
  • Microorganism proliferation

Factors Contributing to Infective Endocarditis

• Endothelial damage due to:
  • Turbulent blood flow (valvular dysfunction)
  • Cardiac catheterization
• Development of thrombi.
• Pathogen entry into bloodstream via:
  • Genitourinary procedures
  • Hemodialysis
  • Intravenous drug abuse
  • Skin infection
  • Cardiac surgery
• Bacteremia.
• Failure of platelet inhibition causing platelet deposition.
• Failure of mechanisms of self-defense (serum complement, antibodies).
• Bacterial infiltration of platelet-fibrin thrombi.
• Colonization on endocardial surfaces.
• Adherence of more platelets and formation of more fibrin leading to vegetation growth.

Myocardial Diseases

• Myocarditis: Inflammatory disorder of the heart muscle characterized by necrosis and degeneration of myocytes.
• Cardiomyopathy: Disorders of the heart muscle, may be genetic or acquired, and is non-inflammatory.

Myocarditis

• Causes include microbial agents, immune-mediated diseases, physical agents.
• Viral etiology most common (Coxsackie B virus), bacteria, parasites.
• Inflammatory diseases (SLE).
• Toxins (drugs, radiation).
• Characterized by left ventricular dysfunction and general dilation of all four chambers.

Cardiomyopathy

• Classified by cause or functional impairment:
  • Dilated
  • Hypertrophic
  • Restrictive

Dilated Cardiomyopathy

• Cardiac failure associated with dilation of one or both ventricular chambers.
• May be related to:
  • Alcohol toxicity
  • Pregnancy
  • Postviral myocarditis
  • Genetic abnormality
• Slow progression of biventricular heart failure with low ejection fraction.
• 50% die in 2 years.
• Characterized by ineffective contractions.
• Main causes: Myocarditis and alcohol abuse (ETOH).

Hypertrophic Cardiomyopathy

• Thickened, hyperkinetic ventricular muscle mass.
• Septum may be affected, leading to idiopathic hypertrophic subaortic stenosis.
• Genetic abnormality involving:
  • Beta-myosin heavy chain
  • Troponin T
  • Alpha-tropomyosin
  • Myosin binding protein C
• Pathology: Massive hypertrophy, asymmetric septum, disarray of myocytes, interstitial fibrosis.
• Clinical features: Decreased chamber volume, decreased stroke volume (SV), decreased diastolic filling.

Restrictive Cardiomyopathy

• Rarest form of cardiomyopathy (idiopathic).
• Decreased ventricular compliance.
• Chiefly affects diastole.
• Normal chamber size and wall thickness.
• Decreased cardiac output and left-sided heart failure can result.

Pericardial Diseases

• Acute pericarditis
• Pericardial effusion
• Tamponade

Tamponade

• Acute tamponade can be fatal due to severe restriction of the heart.
• Signs: Venous congestion, elevated jugular venous pressure (JVP), distant heart sounds.
• Treatment: Relieving the pericardial pressure by aspirating the offending fluid.

Pericarditis

• Acute or chronic inflammation of the pericardium.
• The pericardium surrounds the heart and the pericardial cavity is filled with fluid.
• Two layers of pericardium.

Acute Pericarditis

• Causes:
  • Infection: virus, TB, bacteria
  • Connective tissue disease: SLE, RA
  • Drugs, cancer, renal failure, radiation, trauma, MI (Dressler’s syndrome)
  • Idiopathic
• Symptoms:
  • Pleuritic chest pain affected by position
  • Pericardial rub, fever
• Treatment: Treat underlying cause.

Congenital Heart Diseases

• Abnormality of the heart that is present from birth.
• Can be classified as causing cyanosis or not causing cyanosis.
  • Cyanotic defects
  • Acyanotic defects

Etiology and Incidence

• Congenital heart disease is the most common heart disorder in children.
• Overall incidence is 0.8% of all live births.
• May be attributed to:
  • Maternal rubella during the first trimester of pregnancy
  • Exposure to cardiac teratogens
  • Genetic influences

Pathophysiology

• Results in two primary pathologies:
  • Shunt: Abnormal path of blood flow through the heart or great vessels.
  • Obstruction: Interference with blood flow leading to increased workload of affected chamber.

Atrial Septal Defect (ASD)

• Abnormal opening between the atria.

Ventricular Septal Defect (VSD)

• Abnormal communication between the ventricles.
• Most common type of congenital heart lesion.

Relative Frequency of Cardiac Malformations at Birth

• Ventricular septal defect: 42%
• Atrial septal defect: 10%
• Pulmonic stenosis: 8%
• Patent ductus arteriosus: 7%
• Tetralogy of Fallot: 5%
• Coarctation of the aorta: 5%
• Atrioventricular septal defect: 4%
• Aortic stenosis: 4%
• Complete transposition of the great arteries: 4%
• Persistent truncus arteriosus: 1%
• Anomalous pulmonary venous connection: 1%
• Tricuspid atresia: 1%

Features of Heart Failure in Infants

• Poor feeding and failure to thrive.
• Respiratory distress (mainly tachypnea).
• Rapid heart rate (160 to 180 beats/min).
• Pulmonary rales or wheezing.
• Cardiomegaly and pulmonary edema on radiogram.
• Hepatomegaly (peripheral edema unusual).
• Gallop sounds.
• Color (ashen pale or faintly cyanotic).
• Excessive perspiration.
• Diminished urine output.