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Zdrowie i medycyna

Course: Zdrowie i medycyna > Jednostka 3

Lekcja 5: Niewydolność serca

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What is heart failure?

Elizabeth Taylor (actress), Jim Morrison (film writer, poet, songwriter), River Phoenix (actor, environmentalist), Isaac Asimov (scientist, historian, novelist), Boris Yeltsin (politician), Andre the Giant (wrestler, actor)... the list goes on. One thing they and millions of other people share is that they died of heart failure, a condition in which your heart is unable to pump blood efficiently, meaning that it cannot meet the body’s demands for blood and oxygen. It is sometimes referred to as congestive heart failure, as fluid retention in the lungs and/or body is a characteristic sign.

How does the heart work?

Your heart is a muscular organ that pumps blood through your circulatory system (the blood transportation system comprising of your heart, arteries, capillaries and veins) to all parts of your body. It is divided into four chambers. The two upper chambers, called atria, are joined to the two lower chambers, called ventricles. An internal partition separates the left atrium and ventricle from the right atrium and ventricle. The atria receive blood that is returning to the heart from the circulation, which then flows into the ventricles - the heart’s pumps. The right ventricular pump sends blood out of the heart to the lungs, while the left ventricular pump sends blood out to the rest of your tissues and organs. The left ventricular muscle wall is thicker than that of the right, as pumping blood to the lungs is a relatively easy task compared to pumping it all the way around the body.

Blood circulates through the chambers of your heart in a specific sequence. The right ventricle pumps blood out of your heart to your lungs, where it picks up oxygen. It returns from the lungs and flows into the left atrium and then into the left ventricle, which pumps it back out into the circulatory system that supplies the rest of your body, it finally returns back to the heart, flowing into the right atrium. One-way valves between the heart’s chambers keep the blood cycling through the heart in the right direction. The valves have flaps, called cusps, which open when blood is pumped through them and snap shut to prevent back-flow. The heart sounds are produced when the atrioventricular valves, followed by the semilunar valves snap shut. The cycling of blood through your heart occurs in two phases: diastole, or the period of time when the ventricles are relaxed allowing blood to flow into them from the atria; and systole, the period of time when the ventricles contract and eject blood into the aorta and pulmonary artery. These phases make up one cardiac cycle, or heartbeat.

Doctors use one or more physical measures to assess how well your heart is working. These include cardiac output, which is the volume of blood your heart pumps through the circulatory system in one minute; stroke volume, which is the volume of blood pumped out by the left ventricle in one heartbeat; and the ejection fraction, which is the fraction of blood pumped out of your heart by your ventricles with each heartbeat. If you are a healthy adult, the normal range for cardiac output is 4 L/minute to 8 L/minute, your stroke volume will be between 55 mL and 100 mL, and the ejection fraction will be between 55% and 70%.

What goes wrong when your heart fails?

Heart failure is caused by any condition that damages or weakens your heart, reducing its ability to pump blood efficiently such as heart attacks, high blood pressure, coronary artery disease, or infection. Initially your heart tries to make up for the loss of cardiac output, by developing more muscle mass, enlarging, and pumping faster. Changes may also occur in your circulatory system, as your body adjusts to lower cardiac output. For example, your blood vessels may narrow to increase blood pressure, and blood may be diverted away from less essential tissues and organs, such as the kidneys, as the body tries to compensate for the heart’s reduced power. Overtime, the increased workload leads to changes in the heart muscle itself (known as remodelling), causing it to stiffen, and further reducing its ability to pump blood efficiently, which leads to worsening heart failure. As your heart increasingly struggles to keep up with the body’s demand for blood and oxygen, characteristic signs and symptoms of heart failure begin to appear.

Heart failure can involve the left side, the right side, or both sides of the heart. The left ventricle is the stronger of the heart’s two pumps. Left-sided heart failure is more common, and may subsequently cause the right side to fail.

Left-sided heart failure: There are two types of left-sided heart failure, systolic failure and diastolic failure. Systolic heart failure occurs when the contraction of the muscle wall of the left ventricle malfunctions, which compromises its pumping action. This causes a decrease in the ejection fraction below the normal range, and over time, enlargement of the ventricle. Diastolic heart failure occurs when the left ventricle muscle wall is unable to relax normally, because the muscle has become stiff. When this happens, the heart does not fill properly, although the ejection fraction usually remains within the normal range, the stroke volume is reduced. Regardless of the malfunction, left-sided heart failure leaves the heart unable to pump enough blood into the circulation to meet the body’s demands, and increased pressure within the heart causes blood to backup in the pulmonary circulation, producing congestion in your lungs.

Right-sided heart failure: This usually occurs as a result of left-sided heart failure. When the left side of your heart fails, the pressure increases in the right side. Over time, this damages and weakens the right side of your heart, which then also loses pumping power. This causes blood to back up in circulatory system supplying the rest of your body causing fluid retention (edema) in your limbs (particularly your legs, ankles, and feet) within your abdomen, and around your liver.

Reduced cardiac output and blood supply may have multiple effects in various organs and tissues. These include:

An increased heart rate due to increased sympathetic nervous system activity, the part of the nervous system responsible for accelerating heart rate, constricting blood vessels and raising blood pressure. Although increased heart rate helps maintain cardiac output, it also means more oxygen is needed by the heart itself - increased cardiac perfusion may worsen coronary artery disease or cause arrhythmias, as well as stimulate increases in muscle mass leading to heart enlargement.
Increased blood pressure due to sympathetic nervous system activity (increases the amount of work the heart has to perform).
Increased blood volume and blood pressure due to secretion of antidiuretic hormone in response to sympathetic nervous system activity, which causes fluid retention in the kidneys.
Salt and fluid retention by the kidneys caused as a result of reduced blood flow to the kidneys, which ultimately leads to the secretion of aldosterone, a hormone that stimulates absorption of sodium (Nastart superscript, plus, end superscript) by the kidneys, and regulates the balance of salt and water in the bloodstream.
Heart muscle remodelling caused by chronically high levels of a number of hormones including catecholamines, renin, angiotensin, and aldosterone.
Decreased muscle strength due skeletal muscle atrophy resulting from reduced perfusion.
Impaired liver function and jaundice caused by severe liver congestion.

Signs and symptoms of heart failure

Heart failure is a clinical syndrome (a disorder that causes a group of signs and symptoms) rather than a specific disease. The combination of symptoms that you experience will depend on any underlying conditions you may have, as well as the specific malfunctions within the heart itself. The most common symptoms include shortness of breath, especially with exercise or when you lay down, fatigue, weakness, and swelling in your legs, ankles and feet. Although all of these signs and symptoms may be caused by heart failure, they also commonly occur as a result of other heart or lung diseases; for example, arrhythmia, or pulmonary embolism. The combination of symptoms you experience largely depends on which side, or sides, of your heart are malfunctioning.

Left-sided heart failure reduces cardiac output to the body’s organs and tissues; however, the first symptoms are often caused by fluid buildup and impaired gas exchange in the lungs. Typical signs and symptoms include shortness of breath, rapid breathing, orthopnea (shortness of breath when lying flat, paroxysmal nocturnal dyspnea (attacks of severe shortness of breath and coughing that generally occur at night), and sometimes crackling noises that can be heard coming from the lungs. Reduced cardiac output may also cause general fatigue due to the reduced ability to oxygenate blood and deliver it around the body, and your healthcare provider may be able to hear abnormal heart sounds or murmurs that sometimes occur when the heart is enlarged, when blood pressure inside the heart is raised, or when the heart valves are malfunctioning. In more severe cases of heart failure, you may experience other symptoms related to a lack of oxygen in the organs and tissues, such as cold, clammy hands and feet, cyanosis (blue or purplish colored skin), weakness, dizziness, and fainting.

Right-sided heart failure occurs in about one in 20 cases of heart failure, often following left-sided heart failure. Many of the symptoms are related to fluid retention in various organs and tissues. In particular, congestion in peripheral capillary beds causes swelling under the skin (peripheral edema) that may move around according to the forces of gravity. For example, your feet and ankles may swell when you are standing up, while areas of your lower back may swell when you are lying down (known as sacral edema). Peripheral edema in your legs may then lead to nocturia, the need to urinate frequently during the night. This happens because fluid retained in your legs during the day flows back into your bloodstream when you lay down, and is processed into urine in your kidneys while you sleep. In more severe cases, the edema caused by right-sided heart failure, may result in pitting peripheral edema, a swollen abdomen due to fluid retention in the space within the abdominal cavity (ascites), or liver enlargement due to fluid retention around the liver.

What causes heart failure?

Many different conditions and diseases may lead to heart failure, the most common being a heart attack, which occurs when one or more coronary arteries (the arteries supplying the heart with blood and oxygen) get blocked. This starves part of the heart muscle of oxygen, and can cause permanent damage that may lead to heart failure. The second most common cause of heart failure is hypertension or high blood pressure. Other risk factors that contribute to heart failure include heart valve disease, infections of the heart or lungs, excessive alcohol or drug use, diabetes, smoking, obesity, high cholesterol, an overactive thyroid, anemia, and congenital heart disease.

How likely are you to get heart failure?

Heart failure is a very common condition. In 2010, over 40 million people were living with heart failure worldwidestart superscript, 1, end superscript, and it is predicted that one in five people will develop heart failure at some point during their lifetime.squared The prevalence of heart failure increases with age as the more common causes, such as coronary artery disease and high blood pressure are more prevalent in older populations. because heart failure is the final manifestation of all forms of cardiovascular disease, it is steadily increasing as the management of heart disease improves. Unfortunately, although treatments are improving, it still causes significant illness and death, with half of all patients diagnosed with heart failure dying within four years.cubed

How can you prevent heart failure?

Reducing your risk factors can go a long way towards preventing heart failure. For example, controlling high blood pressure and diabetes, maintaining healthy cholesterol levels, not smoking, eating a healthy diet, staying physically active, reducing stress, and taking any medications you may need for any of these conditions, all lower your risk of developing heart failure.

How is heart failure diagnosed and treated?

Diagnosing heart failure: There is no one specific test for heart failure. Your healthcare provider will likely start by taking a medical history, reviewing your symptoms and risk factors, and doing a physical examination to check for signs of congestion, or abnormal heart sounds. You may need to provide a blood sample to test for kidney, liver, or thyroid disease, all of which may affect heart function. In addition, you may undergo various imaging tests that visualize the condition of your lungs and heart. These include X-rays, computerized tomography (CT), or magnetic resonance imaging (MRI), which may reveal whether or not your heart is enlarged, and locate fluid buildup in your lungs or heart, as well as help diagnose other heart problems, including causes of heart failure. Other useful tests include: an electrocardiogram, which tests the electrical activity of your heart and can reveal abnormal heart rhythms; an echocardiogram, which can distinguish systolic (abnormal pumping) and diastolic heart failure (abnormal filling), as well as indicate valve problems, and other heart abnormalities; measurement of your ejection fraction (during an echocardiogram, or by a variety of other procedures), which can determine how well your heart is pumping, classify your heart failure, and help guide therapy; stress tests using a treadmill or a stationary bike, which measure how well your heart responds to exercise; a coronary angiogram and ventriculogram, which can reveal narrowed arteries, and the strength of the pumping action of the left ventricle and the health of the heart valves, respectively; and myocardial biopsy, which can help diagnose heart muscle diseases that cause heart failure.

Treating heart failure: There are two primary goals in the treatment of heart failure: symptom management and optimization of heart function to reduce the need for hospitalization, and help people live longer. Once the damage has been done to your heart muscle, it is generally not possible to reverse it; however, there are various interventions that can stop it or slow it from progressing, as well as relieve symptoms.

Treating the underlying cause or causes is usually the first approach to treating heart failure. This includes treatment of hypertension and lipid disorders, such as high cholesterol, as well as other conditions that may cause or contribute to heart failure, including arrhythmias, obesity, diabetes mellitus, anemia or thyroid disease. Lifestyle changes, such as modifying daily activities to reduce the stress on your heart, eating a healthy diet, reducing alcohol intake, losing weight, and quitting smoking are often recommended as part of the strategy to improve heart health.

Most people with heart failure will be prescribed two or more different types of medication aimed at optimizing heart function and restoring blood circulation. The ultimate effects of these drugs include dilating blood vessels, improving the pumping action of the heart muscle, and reducing edema. The different classes of drugs that are available to treat heart failure include angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers, beta blockers, diuretics, aldosterone antagonists, inotropes, and digitalis (digoxin). You may also be prescribed medications to relieve chest pain, or to help prevent blood clots.

Finally, there are also a number of surgical options to treat the underlying causes of heart failure, as well as for heart failure itself. These include coronary artery bypass graft, or angioplasty (unblocking of a blood vessel), implantation of pacemakers, or artificial heart valves, heart transplantation, implantation of left ventricular assist devices that increase the heart’s pumping action, and heart reconstruction to improve function by reducing the size of the heart.

Weź pod uwagę:

Although the body has mechanisms to counteract heart failure, there will be times when the decreased blood flow cannot keep up with body’s oxygen demands. Poor oxygenation of the body’s organs can cause ischemia in these tissues, which can be quite damaging, e.g., to the kidneys, heart, and brain. Many patients with congestive heart failure will present at the hospital with kidney damage and increased nitrogen in their blood. The primary function of the kidney is to filter the blood, but in order to function properly, it must also be well supplied with oxygen and nutrients. When blood flow to the kidney is reduced, kidney function is compromised due to the decreased supply of oxygen and nutrients, as well as a loss of filtering capacity. This leads to the accumulation of nitrogen and other waste products in the bloodstream.

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