Porth's Essentials of Pathophysiology, 4e

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Heart Failure and Circulatory Shock

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factors other than systolic failure contribute to heart failure in the elderly. Preserved left ventricular function may be seen in 40% to 80% of older persons with heart failure. 44 There are four changes associated with aging that contribute to the development of heart failure in the elderly. 44–46 First, reduced responsiveness to β -adrenergic stimulation limits the heart’s capacity to maximally increase heart rate and contractility during an increase in activity or stress. A second major effect of aging is increased vascular stiffness, which leads to a progressive increase in systolic blood pressure with advancing age, which in turn contributes to the development of left ven- tricular hypertrophy and altered diastolic filling. Third, in addition to increased vascular stiffness, the heart itself becomes stiffer and less compliant with age. The changes in diastolic stiffness result in important altera- tions in diastolic filling and atrial function. A reduction in ventricular filling not only affects cardiac output, but also produces an elevation in diastolic pressure that is transmitted back to the left atrium, where it stretches the muscle wall and predisposes to atrial ectopic beats and atrial fibrillation. Fourth, aging alters myocardial metabolism at the level of the mitochondria. Although older mitochondria may be able to generate sufficient ATP to meet the normal energy needs of the heart, they may be less able to respond under stress. Clinical Manifestations The manifestations of heart failure in the elderly often are masked by other disease. 1,2 Nocturia or nocturnal inconti- nence is an early heart failure symptom but may be caused by other conditions such as prostatic hypertrophy. Lower extremity edemamay reflect venous insufficiency. Impaired perfusion of the gastrointestinal tract is a common cause of anorexia and profound loss of lean body mass. Loss of lean body mass may be masked by edema. Exertional dyspnea, orthopnea, and impaired exercise tolerance are cardinal symptoms of heart failure in both younger and older persons with heart failure. However, with increasing age, which is often accompanied by a more sedentary life- style, exertional dyspnea becomes less prominent. Physical signs of heart failure such as elevated jugu- lar venous pressure, hepatic congestion, and pulmonary crackles are less common in the elderly, in part because of the increased incidence of diastolic failure, in which the signs of right ventricular failure are late manifestations and a third heart sound is typically absent. 45 Instead, behavioral changes and altered cognition such as short- term memory loss and impaired problem solving are more common. With exacerbation of heart failure, the elderly may present with acute delirium, dementia, and restlessness. Depression is common in the elderly with heart failure and shares the symptoms of sleep distur- bances, cognitive changes, and fatigue. The elderly also maintain a precarious balance between the managed symptom state and acute symp- tom exacerbation. During the managed symptom state, they are relatively symptom free while adhering to their treatment regimen. Acute symptom exacerba- tion, often requiring emergency medical treatment, can

be precipitated by seemingly minor conditions such as poor adherence to sodium restriction, infection, or stress. Failure to promptly seek medical care is a com- mon cause of progressive acceleration of symptoms. Diagnosis andTreatment The diagnosis of heart failure in the elderly is based on the history, physical examination, chest radiograph, and echocardiographic findings. 1,47 However, the presenting symptoms of heart failure often are difficult to evalu- ate and differentiate from changes associated with aging and other co-morbidities. Symptoms of dyspnea on exer- tion are often interpreted as a sign of “getting older” or attributed to deconditioning from other diseases. Ankle edema is not unusual in the elderly because of decreased skin turgor and the tendency of the elderly to be more sedentary with the legs in a dependent position. Treatment of heart failure in the elderly involves many of the same methods as in younger persons, with medication dose adaptations to reduce age-related adverse and toxic events. ACE inhibitors may be par- ticularly beneficial to preserve cognitive and functional capacities. Activities are restricted to a level that is commensurate with the cardiac reserve. Seldom is bed rest recommended or advised. Bed rest causes rapid deconditioning of skeletal muscles and increases the risk of complications such as orthostatic hypotension and thromboemboli. Instead, carefully prescribed exer- cise programs can help to maintain activity tolerance. Even walking around a room usually is preferable to continuous bed rest. ■■ Heart failure occurs when the heart fails to deliver sufficient blood to meet the metabolic needs of body tissues. ■■ The pathophysiology of heart failure reflects the interplay between a decrease in cardiac output that accompanies heart failure and the compensatory mechanisms that preserve the cardiac reserve. Compensatory mechanisms include the Frank-Starling mechanism, sympathetic nervous system activation, the renin-angiotensin-aldosterone mechanism, natriuretic peptides, endothelins, and myocardial hypertrophy and remodeling. In the failing heart, early decreases in cardiac function may go unnoticed because these compensatory mechanisms maintain the cardiac output. ■■ Heart failure may be described in terms of ejection fraction (reduced vs preserved). Clinical manifestation depends upon which ventricle is dysfunctional. With a reduced ejection fraction, SUMMARY CONCEPTS

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