HF – heart failure 心力衰竭
cardiac muscle – 心肌
sarcomere – n. 肌（原纤维）节
contractile – a. 有收缩性的
actin – n. 肌动蛋白
myosin – n. 肌球蛋白
troponin – n. 肌钙蛋白
actomyosin – n. 肌动球蛋白
hypoxic – a. 含氧量低，缺氧的
cardiomegaly – n. 心肌扩大
anabolic – a. 蛋白同化的，合成代谢的
anabolic steroid – 促蛋白合成甾类
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Heart Failure 心力衰竭
HF is a syndrome that usually involves dysfunction of the cardiac muscle, of which the sarcomere is the basic unit. The sarcomere contains two contractile proteins, actin and myosin. When a cardiac muscle cell is stimulated, calcium enters the cell and inactivates the troponin, allowing the actin and myosin to form actomyosin bridges. The formation of these bridges allows the muscle fibers to slide together or contract. The formation of these bridges and subsequent contraction require a constant supply of oxygen, glucose, and calcium.
HF can occur with any of the disorders that damage or overwork the heart muscle:
破坏心肌或使心肌过劳的任何疾病都可能引起心衰：
l Coronary artery disease (CAD) is the leading cause of HF, accounting for approximately 95% of the cases diagnosed. CAD results in an insufficient supply of blood to meet the oxygen demands of the myocardium. Consequently, the muscles become hypoxic and can no longer function efficiently. When CAD evolves into a myocardial infarction (MI), muscle cells die or are damaged, leading to an inefficient pumping effort.
l Cardiomyopathy (a disease of the heart muscle that leads to an enlarged heart, cardiomegaly, and eventually to complete muscle failure and death) can occur as a result of a viral infection, alcoholism, anabolic steroid abuse, or a collagen disorder. It causes muscle alterations and ineffective contraction and pumping.
l Hypertension eventually leads to an enlarged cardiac muscle because the heart must work harder than normal to pump against the high pressure in the arteries. Hypertension puts constant increased demands for oxygen on the system because the heart is pumping so forcibly.
l Valvular heart disease leads to an overload of the ventricles because the valves do not close tightly, which allows blood to leak backward into the ventricles. This overloading leads to muscle stretching and increased demand for oxygen and energy as the heart muscle must constantly contract harder. (Valvular heart disease is seen less often today owing to the success of cardiac surgery and effective treatment for rheumatic fever.)
The end result of all of these conditions is that the heart muscle cannot pump blood effectively throughout the vascular system. If the left ventricle pumps inefficiently, blood backs up into the lungs, causing pulmonary vessel congestion and fluid leakage into the alveoli and lung tissue. If the right side of the heart is the primary problem, blood backs up in the venous system leading to the right side of the heart. Liver congestion and edema of the legs and feet reflect right-sided failure.
1. Which of the following patients are MOST at risk for developing heart failure? Select-all-that-apply:
A. A 69 year old male with a history of alcohol abuse and is recovering from a myocardial infarction.
B. A 55 year old female with a health history of asthma and hypoparathyroidism.
C. A 30 year old male with a history of endocarditis and has severe mitral stenosis.
D. A 45 year old female with lung cancer stage 2.
E. A 58 year old female with uncontrolled hypertension and is being treated for influenza. 2. A patient is being discharged home after hospitalization of left ventricular systolic dysfunction. As the nurse providing discharge teaching to the patient, which statement is NOT a correct statement about this condition?
A. "Signs and symptoms of this type of heart failure can include: dyspnea, persistent cough, difficulty breathing while lying down, and weight gain."
B. "It is important to monitor your daily weights, fluid and salt intake."
C. "Left-sided heart failure can lead to right-sided heart failure, if left untreated."
D. "This type of heart failure can build up pressure in the hepatic veins and cause them to become congested with fluid which leads to peripheral edema."
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答案 Answers 1. A, C, E. Rationale: These patients are at most risk for heart failure. Remember risks factor for developing heart failure include: remember the mnemonic FAILURE: Faulty heart valves ( Option C mitral stenosis in this case), Arrhythmias, Infarction (Option A), Lineage, Uncontrolled hypertension (Option E), Recreational drug usage, Evaders (Option E with influenza) 2. D. Rationale: This is a description of right-sided heart failure NOT left ventricular systolic dysfunction. Left-sided systolic dysfunction is where the left side of the heart is unable to CONTRACT efficiently which causes blood to back-up into the lungs...leading to pulmonary edema.
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