Etiology

HF is the eventual outcome of numerous cardiac diseases or disorders (Table 6-1).5 HF can be classified by the primary underlying etiology as ischemic or nonischemic, with 70% of HF related to ischemia. The most common causes of HF are CAD, hypertension, and dilated cardiomyopathy. CAD resulting in an acute MI and reduced ventricular function is a common presenting history. Nonischemic etiologies include hypertension, viral illness, thyroid disease, excessive alcohol use, illicit drug use, pregnancy-related heart disease, familial congenital disease, and valvular disorders such as mitral or tricuspid valve regurgitation or stenosis.

HF can also be classified based on the main component of the cardiac cycle leading to impaired ventricular function. A normal cardiac cycle is dependent on two components: systole and diastole. Expulsion of blood occurs during systole or contraction of the ventricles, while diastole relates to filling of the ventricles. Ejection fraction (EF) is the fraction of the volume present at the end of diastole that is pushed into the aorta during systole. Abnormal ventricular filling (diastolic dysfunction) and/or ventricular contraction (systolic dysfunction) can result in a similar decrease in CO and cause HF symptoms. Most HF is associated with evidence of LV systolic dysfunction (evidenced by a reduced EF) with or without a component of diastolic dysfunction, which coexists in up to two-thirds of patients. Isolated diastolic dysfunction, occurring in approximately one-third of HF patients, is diagnosed when a patient exhibits impaired ventricular filling with or without accompanying HF symptoms but normal systolic function. Long-standing hypertension is the leading cause of diastolic dysfunction. Ventricular dysfunction can also involve either the left or right chamber of the heart or both. This has implications for symptomatology, as right-sided failure manifests as systemic congestion, whereas left-sided failure results in pulmonary symptoms.

Table 6-1 Causes of Heart Failure

Systolic Dysfunction (Decreased Contractility)

• Dilated cardiomyopathies

• Ventricular hypertrophy

• Pressure overload (e.g., systemic or pulmonary hypertension, aortic or pulmonic valve stenosis)

• Volume overload (e.g., valvular regurgitation, shunts, high-output states) Diastolic Dysfunction (Restriction in Ventricular Filling)

• Increased ventricular stiffness

• Ventricular hypertrophy (e.g., hypertrophic cardiomyopathy, other examples above)

• Infiltrative myocardial diseases (e.g., amyloidosis, sarcoidosis, endomyocardial fibrosis)

• Myocardial ischemia and infarction

• Mitral or tricuspid valve stenosis

• Pericardial disease (e.g., pericarditis, pericardial tamponade) MI, myocardial infarction.

From Parker RB, Rodgers JE, Cavallari LH. Heart failure. In: DiPiro JT, Talbert RL, Yee GC, et al. (eds.) Pharmacotherapy: A Pathophysiologic Approach, 7th ed. New York: McGraw-Hill, 2008:174.

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