IJCS | Volume 31, Nº4, July / August 2018

438 Borges et al. Oncocardiology and the symptom fatigue Int J Cardiovasc Sci. 2018;31(4)433-442 Review Article Table 2 - Differences between oncologic fatigue and fatigue related to heart failure Fatigue associated with cancer Fatigue related to heart failure Generalized muscle weakness Weakness of the peripheral and respiratory muscles No improvement with rest or sleep Improves with rest and sleep Worsens with chemotherapy and radiotherapy Worsens with corticosteroids and anti-inflammatory drugs There is no association direct with dyspnea Associated with dyspnea on exertion Dysfunction of the central and peripheral nervous system Dysfunction of the peripheral nervous system Disuse of muscle fibers and contractile alteration Atrophy of Type I aerobic muscle fibers Triggered by low levels of hemoglobin, cortisol, TSH, and free T4 Triggered by an increase in inflammatory mediators Related with worsening nutritional status Associated with cardiac cachexia with disease progression Associated with mild, moderate, or severe pain Source: Author, 2017 of muscle mass, anemia, increased inflammatory activity, changes in coagulation, and adverse events from chemotherapy and/or radiotherapy. All these changes consequently lead to worse quality of life among cancer patients. 39 Cardiotoxicity induced by chemotherapy has been a major concern among oncologists and cardiologists in search of early identification of cardiac dysfunction and monitoring of cardiovascular function during treatment. Cardiac toxicity is one of themost important complications of cancer therapy and is responsible for considerable morbidity and mortality. 40 Several drugs used in cancer treatment have been associated with left ventricular dysfunction, in particular, drugs in the anthracyclines group, like doxorubicin. Anthracycline-induced cardiotoxicity manifests early (< 3 months after treatment) or late (3 to 12 months after treatment), but can also occur 1 year after treatment. According to Suter & Ewer, 41 medications can be classified according to the injury that they cause to the myocardium as leading to reversible (type 1) and irreversible (type 2) injury. One of the effects of cardiac toxicity by anthracyclines involves oxidative stress and lipid peroxidation of the cardiomyocytes. Swain et al. 42 identified 149 cardiac events and reduced left ventricular ejection fraction (LVEF) in 50% of 630 cancer patients treated with doxorubicin. 43 A noninvasive hemodynamic evaluation of patients with HF showed an increase of the following variables: cardiac output, stroke volume, heart rate, and blood pressure. 43 The harmful events of chemotherapeutic agents/ drugs on the cardiovascular system include HF, hypertension, thromboembolic disease, and myocardial diseases (table 3). The main risk factors for cardiotoxicity associated with chemotherapeutic agents are hypertension, age above 60 years, prior left ventricular dysfunction, and prior thoracic irradiation. According to its clinical presentation, cardiotoxicity may have an acute, subacute, or late presentation. 1 The diagnosis of cardiotoxicity is established using biomarkers (including brain natriuretic peptide [BNP] and troponins) and echocardiographic resources. Approximately one-third of the patients have elevated levels of troponins, which are sensitive and specific markers of myocardial injury with the ability to signal the development of ventricular dysfunction in patients receiving elevated doses of chemotherapeutics. 44 The European Society of Cardiology currently proposes a discussion about the relevance of the biomarkers and serial evaluations of LVEF in clinical practice and research. The simultaneous use of blood samples for measurement of biomarkers levels and characterization of genetic and epigenetic factors may be useful in identifying patients with cancer susceptible or resistant to cardiotoxicity. With this approach, it is possible to compare the clinically relevant results before and during cancer treatment, allowing the planning of strategies based on evidence through oncocardiology. 44 Evaluation of oncological fatigue Standardized questionnaires have been incorporated into the assessment of fatigue. Several instruments for assessment of fatigue are available, seven of which have been validated in Brazil for the evaluation of the impact of fatigue on quality of life of oncological patients. 52