Porth's Essentials of Pathophysiology, 4e

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Circulatory Function

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Manifestations of Heart Failure The manifestations of heart failure depend on the extent and type of cardiac dysfunction that is present and the rapidity with which it develops. A person with previ- ously stable compensated heart failure may develop signs of heart failure for the first time when the con- dition has advanced to a critical point, such as with a progressive increase in pulmonary hypertension in a person with mitral valve regurgitation. Heart failure also may be precipitated by conditions such as infec- tion, emotional stress, uncontrolled hypertension, or fluid overload. 28 Many persons with serious underlying heart disease, regardless of whether they have previously experienced heart failure, may be relatively asymptom- atic as long they carefully adhere to their treatment regimen. A dietary excess of sodium may be a cause of sudden cardiac decompensation. The signs and symptoms of heart failure reflect the physiologic effects of the impaired pumping ability of the heart, decreased renal blood flow, and activation of sympathetic compensatory mechanisms. They include fluid retention and edema, shortness of breath and other respiratory manifestations, fatigue and limited exercise tolerance, cachexia and malnutrition, and cyanosis. Fluid Retention and Edema Many of the manifestations of heart failure result from the increased capillary pressures (increased hydrostatic pressures) that develop in the peripheral and pulmonary circulations. The increased capillary pressure reflects an overfilling of the vascular system because of increased sodium and water retention and venous congestion, result- ing from impaired cardiac output. 28 Nocturia is a nightly increase in urine output that occurs relatively early in the course of heart failure. It occurs because of the increased cardiac output, renal blood flow, and glomerular filtration rate that follow the increased blood return to the heart when the person is in a supine position. Oliguria, which is a decrease in urine output, is a late sign related to severely reduced cardiac output and resultant renal failure. Transudation of fluid into the pleural cavity (pleural effusion or hydrothorax) or the peritoneal cavity (asci- tes) may occur in persons with advanced heart failure. Because the pleural veins drain into both the systemic and pulmonary venous beds, hydrothorax is observed more commonly in persons with hypertension involv- ing both venous systems. 28 Pleural effusion occurs as the excess fluid in the lung interstitial spaces crosses the vis- ceral pleura, which in turn overwhelms the capacity of the pulmonary lymphatic system. Ascites can occur in persons with increased pressure in the hepatic and pero- neal veins. It usually reflects right ventricular failure and long-standing elevation of systemic venous pressure. 28 Respiratory Manifestations Dyspnea due to congestion of the pulmonary circula- tion is one of the major manifestations of heart failure. Dyspnea related to activity is called exertional dyspnea;

however, patients with advanced heart failure may experience dyspnea even at rest. Orthopnea is short- ness of breath that occurs when a person is supine. Gravitational forces cause fluid to become sequestered in the lower legs and feet when the person is stand- ing or sitting. When the person assumes the recumbent position, fluid from the legs and dependent parts of the body is mobilized and redistributed to an already dis- tended pulmonary circulation. Paroxysmal nocturnal dyspnea is a sudden attack of dyspnea that occurs dur- ing sleep. It disrupts sleep, and the person awakens with a feeling of extreme suffocation that resolves when he or she sits up. A subtle and often overlooked symptom of heart fail- ure is a chronic dry, nonproductive cough that becomes worse when the person is lying down. Bronchospasm due to congestion of the bronchial mucosa may cause wheezing and difficulty in breathing. This condition is sometimes referred to as cardiac asthma. 28 Sleep-disordered breathing is a common comorbid condition with heart failure and may contribute to wors- ening heart failure. Obstructive sleep apnea is one of the most common forms of sleep-disordered breathing. In persons with obstructive sleep apnea, the upper airway collapses, which leads to the complete cessation of air- flow (apnea) or partial cessation of air flow (hypoap- nea) during sleep. 29 Persons with suspected obstructive sleep apnea should be evaluated by a sleep specialist and undergo a sleep study (polysomnography). Those who meet the diagnostic criteria for obstructive sleep apnea (i.e., exhibit more than five apneas/hypoapneas per hour of sleep caused by airway obstruction) are treated by applying continuous positive airway pressure (usually 5 to 10 cm H 2 O) during sleep. Continuous positive air- way pressure (CPAP) is associated with reduced blood pressure and improved cardiac function in patients with heart disease. 29 Another abnormal respiratory pattern that may occur with heart failure is Cheyne-Stokes respiration , a pattern of periodic breathing characterized by a gradual increase in the depth and sometimes the rate of breath- ing to a maximum, followed by a decrease, resulting in apnea. Although no longer associated solely with heart failure, it is recognized as an independent risk factor for worsening of heart failure. It has been suggested that Cheyne-Stokes respirations may not be just a marker for increasing severity of heart failure, but may also aggra- vate it. 30 During sleep, Cheyne-Stokes breathing causes recurrent awakening and thereby reduces slow-wave and rapid eye movement (REM) sleep. The recurrent cycling of hypoventilation/apnea and hyperventilation may also increase sympathetic activity and predispose to arrhythmias. Fatigue,Weakness, and Cognitive Impairment Fatigue and weakness often accompany diminished output from the left ventricle. Cardiac fatigue is dif- ferent from general fatigue in that it usually is not present in the morning but appears and progresses as activity increases during the day. In acute or severe