Valve Disorders

MITRAL STENOSIS

 Definition

• Mitral valve thickens and gets narrower, blocking blood flow fro. the left atrium to left ventricle

Physiology

• Function of the heart is the transport of oxygen, carbon dioxide, nutrients and waste products
• Cardiac cycle consists of:
• Systole - the phase of contraction during which the chambers eject blood
• Diastole - the phase of relaxation during which the chambers fill with blood. When heart pumps, myocardial layer contracts and relaxes.
• Blood flow:
1. Deoxygenated blood enters the right atrium through the superior and inferior vena cava
2. Enters the right ventricle via the tricuspid valve
3. Travels through the pulmonic valve to pulmonary arteries and lungs
4. Oxygenated blood returns from the lungs through the pulmonary veins into the left atrium and enters the left ventricle via the bicuspid (mitral) valve
5. From the left ventricle, through the aortic valve through the aorta to the systemic cicrculation
• The heart itself is supplied with blood by the left and right coronary arteries
• The vascular system is a continuous network of blood vessels
• the arterial system consists of arteries, arterioles and capillaries and delivers oxygenated blood to tissues
• Oxygen, nutrients and metabolic waste are exchanged at the cellular level
• The venous system, veins and venules, returns the blood to the heart

Heart Infections: Rheumatic Heart Diseases (Rheumatic Endocarditis)

 Definition and Related Terms

• Rheumatic Heart Disease - damage to the heart by one or more episodes of rheumatic fever. Pathogen is a group A streptococci.
• Rheumatic Endocarditis - damage to the heart, particularly the valves, resulting in valve leakage (regurgitation) and/or stenosis. To compensate, the heart's chambers enlarge and walls thicken.

Epidemiology

• Worldwide, 15-20 million new cases of rheumatic fever are reported each year
• Rheumatic Fever - follows a Group A streptococcal infection. We could prevent it by finding and treating streptococcal pharyngitis
• Where malnutrition and crowded living are common, rheumatic fever is most common in children between ages 5 and 15.
• Rheumatic Fever strikes most often during cool, damp weather. In the US, it is most common in the Northern States.
• It is unknown how and why group A streptococcal infections cause the lesions called Aschoff bodies
• Damage depends on site of infection: most often the mitral valve in females and the aortic valve in males
• Malfunction of these valves leads to severe pericarditis, and sometimes pericardial effusion and fatal heart failure. Of those who survive this complication, about 20% die within ten (10) years.

Heart Infections: Endocarditis

 Definition and Related Terms

• An infection of the endocardium, heart valves,  or cardiac prosthesis resulting from bacterial or fungal invasion
• Endocarditis can be classified as:

1. Native valve endocarditis
2. Endocarditis in IV drug users
3. Prosthetic valve endocarditis

Epidemiology

• With proper treatment, about 70% of clients recover
• The prognosis is worse when endocarditis damages valve severely or involves a prosthetic valve
• Infective endocarditis occurs in 50-60% of clients with previous valvular disorders
• Systemic Lupus Erythematosus (SLE) often leads to nonbacterial endocarditis
• In 12-35% of clients, with subacute endocarditis, lesions produce clots that show the findings of splenic, renal, cerebral or pulmonary infarction, or peripheral vascular occlusion

Heart Infections: Myocarditis

Myocarditis

• an inflammatory condition of the myocardium that may be caused by
• viral infection
• bacterial infection
• fungal infection
• serum sickness
• rheumatic fever
• chemical agent
• as a complication of collagen disease (Systemic Lupus Erythematosus)

Epidemiology

• may be acute or chronic and may occur at any age
• usually an acute virus and self-limited, but it may lead to acute heart failure

Findings

• depends on the type of infection, degree of myocardial damage, capacity of myocardium to recover, and host resistance
• may be minor or unnoticed - fatigue and dyspnea, palpitations, occasional precordial discomfort manifestations such as mild chest soreness and persistent fever
• recent upper respiration with fever, viral pharyngitis or tonsillitis
• cardiac enlargement
• abnormal heart sounds - murmur, S3 or S4 or friction rub

Levine's Grading of Heart Murmurs