Human Cardiovascular system - Congestive-Heart-Failure
What is Congestive Heart Failure or CHF?
The body is made up of living cells that require a constant supply of oxygen and nutrients in order to survive and remain functional. This fuel (oxygen and nutrients) is delivered to the body cells in the form of blood that is pumped by the heart. If the heart muscle weakens, the amount of blood pumped is proportionately reduced. Heart failure occurs when the heart is unable to pump enough blood to meet the usual demands of the body. The circulation of blood within the body is carried out within a closed circuit. In other words, all the blood that is pumped to the body is returned to the heart. The rising back pressure of blood in a failing or weakened heart is faced by all parts (liver, lungs, legs, etc.) of the body that empty into the pump. These organs get congested or flooded with fluid as a result of the back pressure. The congestion of the body due to back pressure from a failing heart is known as congestive heart failure or CHF. The reduced forward flow of the pump directly impacts on all areas that it supplies blood to. For example, fatigue will occur if the muscles in the arms and legs get a reduced supply of oxygen and nutrients (carried by blood).
How common is CHF?
Heart failure is a common condition that affects more than 4.5 million people in the USA, with nearly half a million new cases being diagnosed each year.
- Approximately, 1.2 to 2% of the population has heart failure, and 75-80% of these patients are greater than 65 years of age (in whom the likelihood of heart failure increases to 6-10%)
- It is also estimated that nearly 20 million people have unsuspected heart failure, and are likely to develop symptoms in the next 1 -5 years.
- Heart failure is responsible for >11 million visits to a physician!!!s office and results in 3.5 million hospitalizations per year. One-third of these patients require repeat hospitalization within three months.
How serious is CHF?
Each year, approximately a quarter of a million people die from heart failure.
- The number of deaths from heart failure, either as a primary or secondary cause has increased 6-fold over the last 40 years.
- It is the leading cause of hospitalization in in people who are 65 years or older.
- The risk of death is 5 - 10% per year in patients with mild symptoms and as high as 30-40% in those with severe disease.
- Annually, it is estimated that $25-40 billion is spent in the USA, in the care of patients with heart failure, $8-15 billion is spent in hospitalizations and the rest in medications, home health care, etc. The estimates do not include indirect costs such as loss of productivity.
- The cost of hospitalization for heart failure is twice that for all forms of cancer.
What are the causes of CHF?
Damage of heart muscle as a result of coronary artery disease is by far the most common cause of CHF and accounts for nearly two-thirds of all cases. Other causes include:
- Hypertension or high blood pressure (4%)
- Toxic injury to the heart from high levels of alcohol, viral infection, etc. (2-4%)
- Diseases of the heart valves (4%)
- Unknown or idiopathic causes (20%)
- Related to pregnancy, in rare cases
What are the symptoms or complaints of CHF?
As noted earlier, heart failure occurs when the heart is unable to supply enough blood to meet the usual demands of the body. The first is caused by reduced forward flow of the pump, and the second by congestion created by the backing-up of fluid and pressure. a weakened heart reduces the amount of blood that it pumps to the arms, legs, brain and other parts of the body. When a person with heart failure exercises or performs a physical activity (walking to the mailbox, etc.), the weakened heart is unable to proportionately increase blood supply to the arms and legs. This results in fatigue during exertion. Reduced blood supply to the brain may cause dizziness. Remember, that all organs (liver, lungs, legs, etc.) return blood to the heart. When the heart begins to fail or weaken, it is unable to pump blood forward as quickly as it receives it. This backs up fluid and increases the pressure within all the organs. Let us examine a few of these organs and see how they cope with congestion LUNGS: When the lungs get congested, two things happen. Firstly, they become stiffer and it takes more of an effort to breathe. Secondly, fluid starts to escape into the air sacs (alveoli; pronounced al-vee-o-lie) where oxygen is taken up by blood. The fluid interferes with oxygen exchange and can markedly aggravate shortness of breath. Patients with CHF may experience one or more of the following breathing problems: - Shortness of breath during exertion: This may be one of the earliest symptoms of CHF and patients have a rather predictable pattern. For example, shortness of breath may initially occur only after the patient has walked a mile. As CHF worsens, the shortness of breath is brought on by lesser exertion, such as walking only half a city block, or even around the house. - Requiring extra pillows at night to help breathing: A patient with CHF may have to sleep on two pillows just to be able to breathe comfortably at night. With worsening CHF, the same patient may need to prop his or her head on three or even four pillows to rest comfortably at night. - If CHF gets even worse, patients may not be able to sleep comfortably, even when they use three or four pillows. They may have to sleep sitting up in a chair or recliner. - Sudden and severe shortness of breath in the middle of the night: This problem may awaken the patient from a sound sleep and force him or her to sit or even stand up. This is known as P.N.D. or paroxysmal (sudden onset) nocturnal (night) dyspnea (shortness of breath. Pronounced disp-nee-ya) and usually lasts around 5-15 minutes. In most cases, P.N.D. resolves as quickly and as dramatically as it occurs. - Pulmonary or lung edema: A weakened or failing heart can cause a serious build up of fluid within the lung tissue, as was seen in the flooded valley example. If this is severe enough, it can cause a large amount of fluid to escape out of the blood vessels. The fluid enters and begins to fill air sacs (where blood normally takes up oxygen and releases carbon dioxide) of the lungs. The fluid in the air sacs (known as alveoli; pronounced al-vee-o-lie) interferes with oxygenation of the blood and results in severe shortness of breath. This can occur any time of the day or night and is a medical emergency that requires treatment in a hospital. LEGS, ANKLES & FEET: Blood from the feet and legs is returned to the heart. In a weakened or failing heart, there is a back-up of fluid and pressure in these areas since the heart is unable to pump blood as promptly as it is received. This increased congestion within the feet and legs causes fluid to seep out or escape from the blood vessels. The free fluid makes its way to the area below the skin and fatty tissue. The feet. ankles and legs begin to bloat up with fluid and increases in size causing edema (pronounced ed-ee-ma) or swelling of the legs. INCREASED BODY WEIGHT: As a result of edema in the legs and other parts of the body, more than 10 pounds of free water may be present in the tissue of the body. In addition to the feet and legs, the fingers and hands may also swell and wedding bands may suddenly become too tight. Fluid may also escape within the cavity of the abdomen causing the belly to appear swollen and clothes to feel tight.
How does the body respond to CHF?
When the body perceives a decrease in the pumping ability or output of the heart, specific reflexes are triggered to allow it to cope with this problem. God equipped us with these reflexes to help survive injury and blood loss until our heart has had a chance to recover. These reflexes were not designed as a long term measure to support a very sick heart. It is very important to remember this concept!. With blood loss, the heart is forced to work with a smaller volume of circulating blood. This smaller volume results in decreased filling of the heart. The heart muscle is composed of units known as actin and myosin. These units serve as the contracting mechanism of the heart, very similar in its action to spring devices that are used in a gym. Therefore, it comes as no surprise that decreased filling of the heart would be expected to cause a reduction in the pumping ability of the heart. If the body suffered from an excessive reduction in the circulating volume (as with severe blood loss or even with marked dehydration), the output of the heart would be reduced so drastically that it would not be able to maintain the blood pressure of a patient. This would cause a very low blood pressure or even result in shock. The output of the heart can also be reduced when its muscle is weakened or failing. As less blood is pushed out, more blood is left behind. The body compensates for the reduced output by trying to increase its filling. First, the veins that return blood to the heart is constricted or reduced in caliber (as shown above). This shunts more blood to the heart. Secondly, the kidney releases chemical substances that causes the body to retain sodium and water. This in turn increases the volume of circulating blood. Both of these mechanisms cause the heart to dilate or enlarge in an attempt to take advantage of Frank-Starling!!!s law However, the Frank-Starling!!!s law also points out that increased stretch of the elastic heart muscle increases its recoil within set limits. If these limits are exceeded (when the elastic heart muscle strips are stretched beyond a certain point), the heart muscle looses its recoil or elasticity. You can compare this to an exercise spring (above) that has been stretched too far and now cannot spring back like it used to. Increased filling of the failing heart with associated decreased emptying causes back-pressure or congestion of all the parts of the body that have to return blood to it. This causes fluid build up and swelling of the feet, ankles, legs, liver, lungs, etc., as previously discussed. If the body!!!s need for nutrients cannot be met by the struggling heart, the system now calls upon another emergency measure which is a ration system. Blood supply to the brain and vital organs are given the highest priority, while supply to relatively less important parts of the body (skin, muscles of the arms and legs, etc.) is drastically reduced. This is made possible by selective constriction (contraction) of the arteries that supply blood to the less vital organs, while the arteries to the brain, etc. are left wide open. The above stop gap rationing system ensures adequate blood supply to the brain by reducing supply to parts of the body that have less or intermediate importance. However, the constriction or clamping down of the arteries creates a new problem by increasing the resistance against which the failing heart has to pump against. This load makes the heart fail even further. In summary, all the above mechanisms serve as a safety back-up systems that can temporarily increase the output of the heart. If the heart does not recover, or if it continues to weaken, all of these mechanisms turn into a self-destruct mechanism. The fittest survive, while others need medications to counteract the above reflexes. Remember that these measures were designed to combat a low output of a normal heart (as caused by blood loss during an accident) and can only temporarily help a failing heart.
What is diastolic heart failure or CHF?
The left ventricle (LV) or major pumping chamber of the heart empties during systole (pronounced sis-tull-e). The filling process of the LV is known as diastole (pronounced die-as-tull-e). Traditionally, CHF usually refers to failure or weakness of the pumping or systolic action of the heart. However, CHF can also occur in patients who have well preserved systolic function but have problems with diastole or filling of the LV. The walls of the LV are made up of fairly elastic muscle which stretches when it is filled up with blood returned by the body. The LV becomes stiffer and less elastic when it is severely thickened as a result of long standing, uncontrolled high blood pressure or certain types of heart disease such as hypertrophic (pronounced hi-per-trow-fic) cardiomyopathy (pronounced car-dee-o-my-op-a-thee). Stiffness of the LV can also be caused by a disease known as restrictive cardiomyopathy. With increased stiffness of its walls, the LV requires a higher volume of blood to stretch it adequately. In other words, less blood will not be able to stretch and fill the LV. To understand this concept, let us compare the elasticity or filling of a balloon to that of an automobile tire. A balloon can be inflated with air with the use relatively low pressure. On the other hand, the flat automobile tire on the left requires a considerably greater amount of pressure to inflate it. Now imagine if you will that the balloon and tire are both of the same size or volume. The air pressure within the balloon will be far less than that of the automobile tire. In other words the pressure within diastole or filling of the LV is far greater when its walls are very stiff. The high pressure is reflected back to the lungs, the right ventricle and to the body. As the pressure rises, the lungs, legs, etc., become congested in a manner similar to that of CHF caused by weakness of the heart muscle. This is known as diastolic failure of the heart and can be seen even when the pumping ability of the heart is well preserved.
How is CHF diagnosed?
The diagnosis of CHF is first suspected when the patient provides a history and complains about fatigue, shortness of breath, swelling and weight gain. Physical examination by the physician helps to strengthen the suspicion or even confirm the diagnosis. At this time, the physician will usually order an EKG (to determine if there is evidence of a prior heart attack, signs of increased wall thickness, irregular heart beats, etc.). A chest x-ray will show if the heart is enlarged and whether or not the lungs are congested or filled with fluid. An echocardiogram is an extremely important test that helps determine the size, thickness and function of the various heart chambers and valves. It also helps estimate pressure within the lungs and determine whether or not the patients volume of blood is excessive. Based upon the above evaluation, the physician may order a Holter monitor if irregular heart beats are suspected or seen, a stress test (regular, echocardiographic, nuclear or chemical) if coronary disease is suspected or even recommend cardiac catheterization.
How is CHF treated?
The treatment of CHF is divided into the following four parts:
- Prevention of initial cardiac injury: Coronary artery disease and hypertension are the two commonest causes of CHF. Dietary restrictions, exercise, weight reduction in obese individuals, cessation of smoking, and treatment of risk factors like a high cholesterol level and diabetes are important cornerstones in the prevention of CAD. Use of medications to control blood pressure also goes a long way in preventing CHF. Since heavy use of alcohol can contribute to the development of CHF, such a tendency needs to be discouraged.
- Prevention of further injury: Aggressive early treatment of a heart attack reduces the amount of damaged muscle and decreases the likelihood and severity of CHF.
- Prevention of post-injury deterioration: Studies have shown that patients who have suffered considerable muscle damage after a heart attack tend to do better if they are maintained on a class of drugs known as ACE inhibitors. It is believed that these medications prevent further deterioration.
- General treatment of CHF.
Medications that are commonly used in the treatment of CHF:
- ACE inhibitor
- Angiotensin-2 blocker or ARB
- Carvedilol or Coreg*
- Beta blocker
Diuretics plus reduction of salt and fluid intake: All patients with CHF benefit from moderate salt restriction with daily measurement of weight. This permits the use of lower and safer doses of diuretics or water pills, which include furosamide (Lasix). torsemide (Demadex), bumetanide (Bumex), HCTZ (hydrochlorothiazide), etc. As noted earlier, CHF results in retention of salt and water. This causes an in increased body weight, swelling and shortness of breath. Diuretics or water pills are effective because they increase the excretion of urine and sodium (which is contained in salt). There are several different types of diuretics available. Their selection is based upon the patient!!!s kidney function and severity of heart failure. At times, a combination of two diuretics may be used . The goal of this form of treatment is to eliminate symptoms and the physical signs of fluid retention. Measurement of daily weight is important in monitoring diuretic treatment. A steady weight gain could indicate inadequate effects. Patients need to remember that diuretics have a tendency to increase thirst. The purpose of taking a diuretic is defeated if one succumbs to thirst and drinks an extra 1500 cc of fluids after taking taking a diuretic and making the same amount of urine. Check with your physician about the amount of fluids that you are allowed per day. Then stick to that restriction. You need to use a measuring cup to help determine your fluid intake, or at least know the size of your drinking glass (i.e., 6 ounces, etc.). Remember that fluids include water, juice, coffee, tea, soda, milk, soups and any fluid that is liquid at room temperature (popsicle, ice and gelatin). Also, note that watermelon, when eaten in large amounts, can result in the intake of a lot of fluid. Taking a diuretic can result in the depletion of important electrolytes or minerals like potassium. For this reason, the use of a diuretic is frequently accompanied by the addition of a medication that contains potassium. Alternatively, your physician may combine a different type of diuretic (potassium sparing) which will help reduce the wasting of potassium. Potassium sparing diuretics include Maxzide, Dyazide, Triamterene-HCTZ, spironololactone etc. Excessive use of diuretics can decrease the volume of circulating blood. This in turn can result in decreased blood pressure, weakness and worsening kidney function. It is more likely to occur if one has a reduced intake of fluids (loss of appetite, nausea, etc.), or loose fluids due to diarrhea and vomiting. Monitoring of your weight and periodic check of your potassium level and kidney function helps to avoid this problem. While taking a diuretic, your physician may advise you to eat foods that are rich in potassium. Very good sources of potassium include bananas, cantaloupe, honey dew melon, prunes, grapefruit and oranges. Good sources of potassium are cooked dried beans, cooked greens, sweet potato, green lima beans, white potato, winter squash, fruit cocktail, raisins, apple juice and peaches. Patients with CHF also need to limit the intake of salt. Most of the sodium (component of salt) comes from our salt shaker and from processed food that include canned food, boxed mixes, and most ready-to-eat foods in the grocery store. We also take in sodium with salted nuts, fast foods, salad dressing, buttermilk, soup, salt pork, bacon, cereals, vegetable juice, cheese, pickles, cured meats, peanut butter, snack foods, and sauces. A patient can significantly improve the management of CHF by paying attention to food labels. ACE (angiotensin-converting enzyme) Inhibitors: ACE inhibitors are an extremely important in the treatment of CHF. They are almost always employed, unless contraindicated or not tolerated by the patient. Remember that ACE is released in a patient with CHF and is responsible for making certain arteries constrict or clamp down. In the pump and balloon example discussed previously (and shown above), ACE is responsible for increasing blood flow to the brain and other vital organs by constricting arteries and reducing flow to the less essential skin and muscle of the arm and legs. Unfortunately, this action increases the resistance against which the heart has to contract. This translates to extra work for a heart that is already weak and failing. Ironically, an action that was designed to help a heart with a reduced output turns out to be harmful to the failing heart. ACE inhibitor drugs blocks the ACE system and relax the walls of the artery. This lowers pressure and the resistance against which the failing heart has to pump against and reduces the work that it has to perform. Multiple research studies have shown that ACE inhibitors , when used in patients with CHF, can improve symptoms, decrease the need for emergency care, reduce the dosage of diuretics, and lower the risk of death. Examples of ACE Inhibitors include benazepril (captopril (enalapril (fosinopril (Lisnopril (moxepril (perindopril (quinapril (ramipril (trandolapril (etc. Many ACE Inhibitors are also marketed in combination with a diuretic (HCTZ). The following is additionally noted with ACE inhibitors:
- Side-effects may occur early but does not necessarily prevent long-term use if the dosage of this drug and other medications are adjusted.
- Significant improvement in symptoms may be delayed for several months. So do not give up hope in the early stages.
- ACE inhibitors reduce disease progression, even when patients do not note a significant improvement in symptoms.
Risks of treatment with ACE inhibitors include decreased blood pressure, dizziness, worsening kidney function, potassium retention, cough (in 5-15% of cases), and an allergic reaction known as angioedema (in less than 1% of cases) that can result in swelling of the face and tongue with associated difficulty in breathing. Angiotensin-2 Receptor blockers or ARB: This class of drugs, as a group, is relatively new, compared to ACE inhibitors, and are also used in the treatment of CHF, particularly when ACE inhibitors are not tolerated by the patient because of side-effects. Studies have demonstrated a beneficial effect of ARBs in CHF, similar to that seen with ACE inhibitors. Although differing in chemical structure and its point of action, angiotensin-2 inhibitors dilate or open-up the arteries. This reduces the workload of the failing heart, improves symptoms and decreases the risk of death. The big advantage of this class of drugs it is far less likely to produce cough and angioedema. Available examples of ARBs include losartan (Cozaar), valsartan (Diovan), irbesartan (Avapro), candesartan (Atacand), telmisartan (Micardis), eprosartan (Teventen), olmesartan (Benicar), etc. Like ACE inhibitors, several ARBs are also marketed in combination with a diuretic (HCTZ). Carvedilol or As the output of the heart drops in patients with CHF, the body is stressed and releases catecholamines (pronounced caty-chole-a-meens). They are also called adrenergic (pronounced ad-ree-ner-jic) agents because they are released by the adrenal gland (which sits on top of the kidneys). Adrenaline is such an adrenergic substance. It increases the heart rate and stimulates the weak heart muscle to contract more forcefully. This is known as a beta adrenergic effect and increases the work that the heart has to perform. The sick heart gets tired and sicker as it works harder! The adrenergic substances also cause the arterial walls to constrict or tighten. This is known as alpha adrenergic effect and helps to raise the blood pressure when the weak heart cannot do so on its own. However, as in the case of ACE activity, this increases the resistance against which the weak heart has to pump, putting an additional load on the struggling heart. Carvedilol is a fairly new class of drugs that is being used in the treatment of CHF. The drug blocks both the alpha and beta blocking effects of the adrenergic substances produced by the body. The heart rate is slowed, the weak heart muscle is protected from the whipping or stimulating effects (thus reducing the chance of further deterioration) and the arteries are dilated so as to make it easier for the heart to empty. All these actions, like those of ACE inhibitors are CHF-friendly. Carvedilol, like ACE inhibitors have been shown to improve symptoms, decrease the need for hospitalization and improve survival in patients with CHF. Carvedilol and other agents in its class are always considered in the treatment of CHF unless they are contraindicated or not tolerated. They are generally avoided in patients with asthma, extremely slow heart rates and very low blood pressure. Beta blockers: A beta blocker blocks the beta adrenergic effects of adrenaline and thus prevents the sick heart from b eing forced to work harder. This conservation effort has a protective effect. Unlike carvedilol, beta blockers do not block the alpha receptor and are thus usually considered to be less effective in the treatment of CHF. However, like carvedilol and ACE inhibitors, beta blockers are generally expected to improve symptoms, decrease the need for hospitalization and improve survival in patients with CHF. Beta blockers are usually selected because they are frequently less expensive than carvedilol. Also, certain beta blockers like metoprolol (and bisoprolol (are better tolerated than carvedilol in certain patients with lung disease. Similarly, beta blockers like pindolol (and acebutolol (may be used in patients who tend to have a slower heart beat. Hydralazine: Hydralazine is a drug that dilates arteries and thus reduces the work that the weak heart muscle performs in pumping blood through them. However, this drug is not shown to be generally beneficial as ACE inhibitors in prolonging the life of all patients with CHF. However, a combination of hydralazine and isosorbide (a long acting form of nitroglycerin) has been shown to benefit African American patients with CHF. Digitalis or Digoxin: Digoxin is recommended in the treatment of CHF that is caused by a weakened heart muscle. It is used in conjunction with other agents such as diuretics, ACE inhibitors and adrenergic blockers like carvedilol. Although it stimulates the weak heart muscle to contract a little more vigorously, it is felt that the long term beneficial effects of the drug may be related to the indirect inhibition of adrenergic substance release. Digitalis is also useful in treating certain types of rapid heart beat (atrial fibrillation and atrial flutter) that may accompany CHF. Other drugs and devices that may be used in the treatment of CHF include spironolactone (Aldactone, which has been shown to preserve potassium and reduce the deterioration of CHF), warfarin or Coumadin or blood thinners (that reduce the risk of blood clots), antiarrhythmic agents (to treat dangerous irregular heart beats), blood pressure medications (when ACE inhibitors are unable to control the high blood pressure, or is contraindicated). More recently, specialized Bi-V or bi-ventricular pacemakers may be recommended in select patients with CHF and a left bundle branch block. Also, an ICD (implantable cardioverter-defibrilator) or a Bi-V ICD may be considered in patients with CHF due to coronary artery disease and prior heart attacks.