Heart Failure
When the myocardium can’t pump effectively enough to meet the body’s metabolic needs, heart failure occurs. Usually, the loss in pumping ability is a symptom of
an underlying heart problem such as coronary artery disease. Heart failure can involve the left side of the heart, the right side of the heart, or both. However, it usually affects the left side of the heart first. Left-sided heart failure is classified as systolic or diastolic. (See Categorizing heart failure.)
an underlying heart problem such as coronary artery disease. Heart failure can involve the left side of the heart, the right side of the heart, or both. However, it usually affects the left side of the heart first. Left-sided heart failure is classified as systolic or diastolic. (See Categorizing heart failure.)
Categorizing heart failure
Heart failure is usually classified by the site of failure (left-sided, right-sided, or both). It may also be classified as systolic or diastolic. These classifications represent different clinical aspects of heart failure, not distinct diseases.
Left-sided heart failure
Failure of the left ventricle to pump blood to the vital organs and periphery is usually caused by myocardial infarction (MI). Decreased left ventricular output causes fluid to accumulate in the lungs, precipitating dyspnea, orthopnea, and paroxysmal nocturnal dyspnea.
Right-sided heart failure
Resulting from failure of the right ventricle to pump sufficient blood to the lungs, right-sided heart failure is usually caused by disorders that increase pulmonary vascular resistance, such as pulmonary embolism, pulmonic stenosis, and pulmonary hypertension. Right-sided heart failure produces congestive hepatomegaly, ascites, and edema.
Systolic failure
Systolic failure occurs when the heart’s ability to contract decreases. The heart can’t pump with enough force to pump a sufficient amount of blood into circulation.
Diastolic failure
Diastolic failure occurs when the heart has a problem relaxing. The heart can’t properly fill with blood because the muscle has become stiff.
For many patients, the symptoms of heart failure restrict the ability to perform activities of daily living, severely affecting quality of life. Advances in diagnostic and therapeutic techniques have greatly improved the outlook for these patients, but the prognosis still depends on the underlying cause and its response to treatment.
Causes
Heart failure commonly results from a primary abnormality of the heart muscle (such as an infarction) that impairs ventricular function to the point that the heart can no longer pump a sufficient amount of blood. Heart failure can also result from causes not related to myocardial function. These include:
mechanical disturbances in ventricular filling during diastole, which result from blood volume that is insufficient for the ventricle to pump. This occurs in mitral stenosis secondary to rheumatic heart disease or constrictive pericarditis and atrial fibrillation.
systolic hemodynamic disturbances—such as excessive cardiac workload caused by volume overloading or pressure overload—that limit the heart’s pumping ability. These disturbances can result from mitral or aortic insufficiency, which causes volume overloading, and aortic stenosis or systemic hypertension, which results in increased resistance to ventricular emptying.
In addition, certain conditions can predispose the patient to heart failure, particularly if he has some form of underlying heart disease. These include:
arrhythmias—such as tachyarrhythmias, which can reduce ventricular filling time; bradycardia, which can reduce cardiac output; and arrhythmias that disrupt the normal atrial and ventricular filling synchrony
pregnancy and thyrotoxicosis because of the increased demand for cardiac output
pulmonary embolism because it elevates pulmonary artery pressures that can cause right-sided heart failure
infections because increased metabolic demands further burden the heart
anemia because to meet the oxygen needs of the tissues, cardiac output must increase
increased physical activity, emotional stress, increased sodium or water intake, or failure to comply with the prescribed treatment regimen for the underlying heart disease.
