Porth's Essentials of Pathophysiology, 4e

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Disorders of Cardiac Function

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Clinical Manifestations. The signs and symptoms of myocarditis vary from person to person. 53 Some persons may present with fever, chills, nausea, vomiting, arthral- gia, and myalgia, occurring up to 6 weeks before the diag- nosis of myocarditis. Other persons may present with heart failure without antecedent symptoms. The onset of heart failure may be gradual or abrupt and fulminant. Emboli may occur because of the procoagulant effect of inflammatory cytokines combined with decreased myocardial contractility. At times, the presentation may mimic ACS, with ST-segment and T-wave changes, posi- tive serum cardiac biomarkers, and regional wall motion abnormalities despite normal coronary arteries. Viral myocarditis in children or young adults is often nonspe- cific, with symptoms such as fever and poor eating. Diagnosis andTreatment. The diagnosis of myocardi- tis can be suggested by clinical manifestations. Methods used in confirming the diagnosis include the ECG, chest radiography, serum cardiac biomarkers (i.e., creatinine phosphokinase, troponin I), and echocardiography. Endomyocardial biopsy findings, obtained through car- diac catheterization, remain the gold standard for estab- lishing the diagnosis of acute myocarditis, despite limited accuracy. 52–54 Many cases of myocarditis are mild and self-limiting, so first-line treatment remains largely supportive. 52–54 Initial treatments include supplemental oxygen, bed rest, and antibiotics, if needed. In persons with more severe myocarditis, arrhythmia suppression and hemo- dynamic support with vasopressors and positive inotro- pic agents may be needed. Persons with severe fulminant myocarditis may require aggressive short-term support with an intra-aortic balloon pump or left ventricular assist devices. 52 Immunosuppressive therapy continues to be investigated. Although treatment of myocarditis is successful in many persons, some progress to heart failure. For these patients, cardiac transplantation is an important intervention.  Peripartum Cardiomyopathy Peripartum cardiomyopathy is a dilated cardiomyopa- thy that occurs in the last month of pregnancy or within 5 months after delivery. 55 It is manifested by signs of sys- tolic dysfunction and heart failure for which there is no identifiable cause or evidence prior to the last month of pregnancy. 55–57 The incidence is greater in black, multip- arous, or older women, and in women with twin fetuses, preeclampsia, or using tocolytic therapy to prevent pre- mature labor and delivery. 56,57 Although the etiology of peripartum cardiomyopathy is unknown, several causes have been proposed, including infectious, immunologic, nutritional, drug-induced, and genetic factors. Some women exhibit inflammatory cells in heart biopsies taken during the symptomatic phase of the disorder, suggesting a disordered immune response. Management of peripartum cardiomyopathy includes standard therapy for heart failure. However, potential teratogenic effects and the excretion of drugs during

breast-feeding need to be considered. Prognosis depends on resolution of the heart failure. About half of women with peripartum cardiomyopathy spontaneously recover normal cardiac function; the other half are left with persistent left ventricular dysfunction or progress to develop heart failure. 57 Stress or “Takotsubo” Cardiomyopathy First described in Japan in 1991, takotsubo-like left ven- tricular dysfunction is named after the fishing pot used to trap octopus that has a narrow neck and wide base, a shape similar to that of the affected ventricle. 58,59 The term transient left ventricular apical ballooning has also been used to describe this syndrome. An acquired disorder, stress cardiomyopathy has been identified in the clinical setting as a transient, reversible left ventricular dysfunction in response to profound psychological or emotional stress. The syn- drome occurs primarily in middle-aged women who present with acute STEMI but who, on cardiac catheter- ization, have no evidence of CAD. There is, however, impaired myocardial contractility characterized by left ventricular apical ballooning with hypercontractility of the basal left ventricle. The mechanism for myocardial stunning in stress car- diomyopathy is unclear, although some theories suggest ischemia from coronary artery spasm, microvascular spasm, or direct myocyte injury. When catecholamine levels return to normal, the interventricular gradient resolves and left ventricular function recovers. 60 Treatment of stress cardiomyopathy is the same as that for heart failure, and most patients with takotsubo cardiomyopathy demonstrate rapid improvement and an excellent prognosis. Secondary Cardiomyopathies Secondary cardiomyopathy is a heart muscle disease in the presence of a multisystem disorder. The conditions most commonly associated with secondary cardiomy- opathies are identified in Chart 19-2. Some of these dis- orders produce accumulation of abnormal substances between myocytes (extracellular), whereas others pro- duce accumulation of abnormal substances within myo- cytes (intracellular). Almost 100 distinct myocardial diseases can result in the clinical features of DCM. They include cardiomyop- athies associated with drugs, diabetes mellitus, muscular dystrophy, autoimmune disorders, and cancer treatment agents (radiation and cancer drugs). 59 Alcoholic cardio- myopathy is the single most common identifiable cause of DCM in the United States and Europe. Doxorubicin (Adriamycin) and other anthracycline drugs used in the treatment of cancer, are potent agents whose usefulness is limited by cumulative dose-dependent cardiac toxic- ity. Another cancer chemotherapeutic agent with cardio- toxic potential is cyclophosphamide (Cytoxan). Unlike the primary myocyte injury that occurs with doxorubi- cin, the principal insult with cyclophosphamide appears to be vascular, leading to myocardial hemorrhage.