A Brief Review of Congestive Heart Failure
If you suffer from heart failure, then you know that it is a problem congestion.
Heart failure, more popularly known as congestive heart failure, is a clinical syndrome characterized by the signs and symptoms of fluid overload such as shortness of breath and accumulation of fluid in the lungs and elsewhere (such as the legs or in the abdomen). Heart failure is also characterized by manifestations of inadequate oxygen levels to organs, which creates symptoms such as fatigue and poor exercise tolerance. These signs and symptoms occur when the heart is unable to generate enough cardiac output (or, more simply, forward blood flow) to sustain the needs of the body's tissues.
Congestive heart failure is one of the most prevalent medical conditions, especially in the aging population. Estimates of healthcare expenditures for the diagnosis and treatment of congestive heart failure in the United States alone hover close to $10 billion annually. More troubling is the statistic that the five-year mortality rate of patients with congestive heart failure can be as high as 50 percent in the United States.
The good news is that the diagnosis and management of heart failure continue to evolve with more sophisticated medical knowledge and techniques, and doctors can now offer their patients with heart failure a program of diet, exercise, and medicines that will substantially improve their functional capacity and quality of life.
What is Diastolic Dysfunction?
Unfortunately, I am not going to get through this article about heart failure without using some fancy medical words. One of them is diastolic, and when I use that word I also have to use the word systolic.
It has been shown that between 30 percent to 50 percent of patients with congestive heart failure actually have adequate systolic function. This means that the heart muscle as a pump (or as an organ that moves blood throughout the body with the contraction of its muscles) is not functioning properly. As a result, the patient has a reduced ejection fraction, which is just a way of saying that the amount of blood that is pumped through and out of the heart is less than that in patients who have normal hearts.
Those patients who have normal heart muscle pump function but still suffer from the signs and symptoms of heart failure may have diastolic dysfunction. In this condition, the left ventricle of the heart (that is to say, the main pumping chamber of the heart) can sometimes be stiff and therefore cannot fill with blood normally. Increased pressures are required to fill the left ventricle properly in those patients with diastolic dysfunction. As a result, the elevated pressures required for filling of the left ventricle with oxygenated blood may lead to fluid overload in the lungs—and, therefore, congestion of the lungs and shortness of breath. Additionally, the overall reduced filling of the left ventricle may lead to reduced cardiac output—and, therefore, fatigue and poor exercise tolerance.
What is the Effect on Survival of Diastolic Dysfunction?
In general, the prognosis for patients with congestive heart failure predominantly due to diastolic dysfunction is better than for those patients with systolic dysfunction.
What Causes Diastolic Heart Failure?
Although the mechanisms underlying the development of diastolic heart failure are complicated and difficult to understand in layman's terms, the simplest way to think about diastolic dysfunction is to visualize the main pumping chamber of the heart (the left ventricle) as an organ that expands and fills with blood and then contracts via its muscles to push the blood forward to the body's tissues.
Diastole is that period of time when the left ventricle expands and fills with blood. Several factors determine the overall function of the left ventricle during diastole and include left ventricular relaxation and stiffness as well as left atrial function. The left atrium is the chamber of the heart that serves as a reservoir of blood for the left ventricle.
In a normal left ventricle, the stiffness of its walls is low during diastole (filling period) as blood enters the chamber from the left atrium. As the blood enters the left ventricle, it expands with the increased volume. There are relatively small increases in pressure because of the elasticity (ability to stretch) of the tissues and the heart muscles.
In a patient with diastolic dysfunction, the left ventricle has decreased elasticity (an inability to stretch) due to a variety of causes (see next section) and cannot adequately fill its chamber with blood to maintain an adequate cardiac output without increases in pressures (to overcome the stiffness). As a result of these higher-than-normal left ventricular filling pressures, the patient with diastolic dysfunction may experience any combination of symptoms of congestive heart failure including fatigue, poor exercise tolerance, shortness of breath, and fluid accumulation in the legs or lungs or abdomen.
The most common causes of diastolic heart failure are hypertensive heart disease and coronary artery disease.
Coronary Artery Disease
Coronary artery disease, otherwise known as ischemic heart disease, involves the narrowing of the arteries that supply oxygenated blood to the heart muscle. This disorder affects left ventricular relaxation by limiting the availability of energy compounds carried by the oxygenated blood that are needed to help the heart muscle to relax. Acute ischemic syndromes such as heart attacks will also further increase wall stiffness because of the scar that is formed from damaged heart muscle.
Hypertensive Heart Disease
Hypertensive heart disease is a fancy way of describing heart disease that is caused by high blood pressure. Hypertensive heart disease, especially in older people, causes a thickening of the heart muscles. As a result of this increased wall thickness, the heart muscle becomes stiffer.
The Cardiomyopathies
The term cardiomyopathy generally refers to a primary disease process of heart muscle. There are several different types of cardiomyopathies. Restrictive cardiomyopathies refer to a diverse group of conditions characterized by restriction of diastolic filling, increased stiffness of the heart muscle, and smaller left ventricular cavity size. Examples of disorders that can lead to restrictive heart conditions include amyloidosis, radiation treatment, and some types of muscular dystrophy.
Hypertrophic cardiomyopathy refers to primary thickening of the heart muscle and abnormal arrangement of muscle fibers within the walls. Again, this process of heart muscle thickening leads to restriction of diastolic filling and increased stiffness.
Dilated cardiomyopathy refers to the dilatation (enlargement or widening) of the left ventricular cavity. Dilated cardiomyopathy is typically associated with a decrease in systolic function (overall pump function), but can also contribute to diastolic function.
Other Less Common Causes
It is worth mentioning that there are other less common conditions affecting the heart that may also lead to diastolic dysfunction. Among those conditions is myocarditis, which is an inflammation of the muscular walls of the heart due often to infection. Similarly, pericarditis, which is an inflammation of the pericardium (the sac of tissues that surrounds the heart) can also cause diastolic dysfunction.
Those patients who have received a heart transplant or have received certain chemotherapeutic drugs may also develop the signs and symptoms of diastolic dysfunction.
Which Diagnostic Tests Should You Undergo?
Echocardiography, or ultrasound of the heart, is the most useful diagnostic test for detecting evidence of diastolic dysfunction. Not only is echocardiography portable and safe, but it is also a noninvasive method of studying the function of the heart muscle. That means that there is usually no need for needles or intravenous lines. Echocardiography measures left ventricular performance by assessing the overall ejection fraction. I previously described the concept of ejection fraction as the amount of blood that is pumped through the heart and out into the body.
Additional studies that are typically needed to evaluate the signs and symptoms of heart failure due to either systolic or diastolic dysfunction include an
electrocardiogram, chestx-ray, thyroid function tests, complete blood count, and kidney function blood tests.
How Do We Treat Diastolic Heart Failure?
There are several aspects to treating diastolic dysfunction, or more accurately, heart failure due to diastolic dysfunction. First and foremost, the underlying condition that has caused the diastolic heart failure (such as hypertensive heart disease or coronary artery disease) must be treated. Second, removal of excess fluid with a diuretic is often utilized in the treatment of diastolic heart failure. Third, slowing down the heart rate in order to increase the amount of time in diastole (which is that period of time when the left ventricle fills with oxygenated blood) is advised. Finally, ensuring that the atrium is functioning properly with a normal rhythm should be encouraged so that the atrium can facilitate the filling of the left ventricle with oxygenated blood during diastole.
Diuretics to Remove Excess Fluid
Patients with heart failure with signs of fluid overload should be started on a diuretic. There are many signs of fluid overload. When a patient complains of shortness of breath with exercise or very minimal exercise, when he or she wakes up in the middle of the night with shortness of breath—paroxysmal nocturnal dyspnea—and when he or she requires several pillows at night to sleep comfortably—orthopnea—then there is fluid overload in the lungs. Swollen legs and a swollen abdomen also indicate fluid overload. Swelling in the legs is often termed lower extremity edema and swelling in the abdomen due to accumulation of fluid is termed ascites. My patients will often tell me that they know they are retaining fluid when they feel their clothes fitting more snugly, especially around the waistline.
Diuretics are a class of medications that cause removal of fluid via the kidneys. In other words, diuretics cause the removal of fluid through urination. Patients often note that they are urinating more frequently when on a diuretic. Commonly used diuretics are loop diuretics such as furosemide (or Lasix) and thiazide diuretics such as hydrochlorothiazide. More severe states of congestion, or fluid overload, can be treated with intravenous diuretics and sometimes dialysis. However, caution must be maintained by your physician not to remove too much fluid.
In conjunction with taking diuretics, patients with fluid overload due to a congestive state should adhere to a strict low-salt diet.
Slowing Down the Heart Rate
Without getting too technical about the mechanism of why slowing down the heart rate helps in the treatment of diastolic heart failure, just remember that diastole is that period of time in the cardiac cycle when the left ventricle fills with oxygenated blood. A slower heart rate translates into a longer time in diastole. Hence, more oxygenated blood will fill the left ventricle when the diastolic time is prolonged.
In order to achieve slower heart rates, medications such as beta blockers, examples of which include lopressor, toprol, coreg, propanolol, and atenolol, are often used. Other medications such as calcium channel blockers are sometimes used for this aim as well.
Relaxing the Left Ventricle
Several studies have shown that one particular class of medications called ACE inhibitors can improve the relaxation of the left ventricle and cause it to be less stiff. ACE inhibitors are angiotension-converting enzyme inhibitors; this enzyme is involved in the regulation of salt in the body. There are many different brands of ACE inhibitors on the market today, but some of the more commonly known ones are Zestril, Prinivil, Vasotec, and captopril.
Interestingly, it has also be shown in several studies that ACE inhibitors can substantially reduce the mass of the left ventricle over a long term, such as that seen in patients with a thickened heart due to chronic high blood pressure. This reduced mass will allow better filling of the left ventricle with oxygenated blood. The more oxygenated blood that becomes available to the left ventricle, the more oxygenated blood that becomes available to the rest of the body.
Maintaining Normal Rhythm in the Atrium
As I mentioned earlier, the left atrium is the reservoir of blood for the left ventricle. If the atrium is working properly and has a normal rhythm, then there is adequate flow of oxygenated blood from the atrium to the ventricle. If the atrium does not have a regular and normal rhythm (one example would be atrial fibrillation, which is an irregular heart beat) then there is reduced filling of the left ventricle by the left atrium.
Conclusion
The treatment of heart failure due to diastolic dysfunction has two major goals. First, the underlying heart condition that is causing the heart failure, such as high blood pressure or coronary artery disease, should be recognized. Second, the manifestations of heart failure that affect quality of life, such as shortness of breath and fatigue, should be treated and either improved or eliminated. While both goals should be addressed when the patient presents with heart failure, the immediate relief of shortness of breath and improvement of exercise tolerance can be initiated while a strategy is devised to correct the underlying heart problem.
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