The Cardiovascular System Textbook Resource: An Introduction to Human Disease, Pathology and Pathophysiology Correlations, 7th Ed. By Leonard V. Crowley Congenital Heart Disease • These are defects of the heart in into which a patient is born. Valves or heart chambers are structurally unsound. Sometimes these conditions are the result of infection in utero as in the case of German measles infection. Others are the result of malpositions of the fetus, intrauterine injuries, and chromosomal abnormalities. Some congenital heart diseases may be corrected by surgery. Other abnormalities may cause little variation from normal living while others cause rapid death. Valvular Heart Diseases • Rheumatic Heart Disease • Non-rheumatic Aortic Stenosis • Mitral Valve Prolapse • Serotonin Related Heart Valve Damage • Infective Endocarditis Rheumatic Fever • This is not an infection, but it is a hypersensitivity immune reaction brought about because of group A beta hemolytic Streptococcus infection. Antibodies to the streptococcus cross react with the person’s own tissues. Patients with this disease have arthritic symptoms in joints along with inflammation of the heart. Scarring of the heart can lead to heart complications like valve stenosis and eventual heart failure. Persons with rheumatic fever are given prophylactic penicillin therapy to prevent further infection and subsequent hypersensitivity response. Nonrheumatic Aortic Stenosis • The aortic valve usually has three cusps, but in people with nonrheumatic aortic stenosis, the valve has two cusps. Opening and closing of the defective valve causes thickening, rigidity, and calcification of the valve. The strain associated with constricted blood flow causes ventricular hypertrophy and eventual heart failure. Treatment may require replacing the defective valve with an artificial valve. Risk factors associated with increased chance of aortic stenosis are hypertension, high cholesterol, and diabetes Mitral Valve Prolapse • Mitral valve prolapse is mitral regurgitation or backflow of blood through closed mitral leaflets. Many times the disease is caused by degenerative connective tissue changes of the valve leaflets. This can cause strain of the chordae and papillary muscles to cause arrhythmia. Prophylactic antibiotic therapy is recommended for persons with mitral valve prolapse who undergo dental or surgical procedures. Serotonin-Related Heart Valve Damage • Serotonin is a chemical produced by neuroendocrine cells. Excessive levels of serotonin (5-hydroxytryptamine) is related to types of heart valve destruction through overproliferation of valvular related connective tissue. Some drugs, like those used in migraine treatment and similar to serotonin also cause valve defects. The weight loss drugs fenfluramine and phentermine were recalled because of a link to heart valve damage. Infective Endocarditis • Subacute infective endocarditis is a damage to a heart valve because of inflammation and infection at the valve. Transient bacteria from skin infections, tooth extractions, and other minor infections are carried to the valve site. This causes platelet activation and thrombus formation. Thrombi may cause infarcts in many different organs. Infective Endocarditis cont… • Acute infective endocarditis occurs when highly pathogenic microorganisms in the bloodstream infect a normal heart valve. Pieces of infected valve often reach the pulmonary arteries and lodge in the lungs causing pulmonary infarcts and lung abscesses. Staphylococci is the usual pathogen involved in this type of infection. Intravenous drug abusers are at high risk for this disease. Coronary Heart Disease • Arteriosclerosis, narrowing of the arteries because of accumulations on the vessel wall, causes injury to large coronary arteries. Plaque accumulations and atheromatous plaques occur in the arteries predisposing the vessel to thrombus formations and subsequent myocardial ischemia and infarcts. Clinical manifestation of the disease range from a patient being asymptomatic to one or some in following manifestations: angina pectoris, Prinzmetal’s angina, arrhythmia, cardiac arrest, myocardial infarction Cardiac Arrest • Cardiac arrest is the cessation of cardiac contractions (asystole) . It is associated with coronary disease, shock, trauma, drug abuse, respiratory distress, etc.. This is a type of heart attack. Myocardial Infarction • Myocardial infarction is the necrosis of heart muscle and it too is a type of heart attack. Four mechanisms may trigger a myocardial infarction in persons with coronary artery disease. These are coronary thrombosis, hemorrhage into an atheromatous plaque, arterial spasm, andsudden myocardial oxygen requirements. Myocardial Infarction Complication • Arrhythmias- abnormal cardiac rhythms • Heart failure- loss of normal cardiac function. • Intracardial thrombi-thrombi form at the ventricular wall covering the endocardial surface. • Pericarditis- fluid accumulation at the pericardial sac. • Cardiac rupture- blood accumulates through ruptured cardiac tissue causing inefficient blood output. • Papillary muscle dysfunction- the papillary muscles do not contract during ventricular systole causing mitral valve prolapse • Ventricular aneurysm- an outward bulging of a healing infarct that causes the left ventricle not to contract. Electrocardiogram • A tool to identify myocardial infarction occurrences and the severity of the infarct. It measures electrical transmissions associated with heart contractions. Blood Tests to Identify Myocardial Infarcts • The following enzymes in heart muscles increase during myocardial infarctions: Troponin T, Troponin I, creatinine kinase, creatinine kinase isoenzyme test, lactic dehydrogenase, myoglobin MI Treatments • Thrombus dissolving drugs are used. Streptokinase is commonly used for this purpose • Drugs to reduce platelet aggregations are also used. (Aspirin, heparin) • Methods to restore coronary blood flow like angioplasty are also used. • Pacemakers are also surgically implanted for persons with heart blocks.
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