IJCS | Volume 32, Nº1, January/ February 2019

65 Figure 3 - Hemodynamic components of blood pressure. BP: blood pressure; CO: cardiac output; SVR: systemic vascular resistance; SV: stroke volume; HR: heart rate. Leão and Silva Impedance cardiography and hypertension Int J Cardiovasc Sci. 2019;32(1)61-69 Review Article Arterial hypertension and impedance cardiography Classically defined as an increase in BP, this parameter alone is an incomplete indicator of the cardiovascular system status, particularly in patients with resistance to drug therapy or hypervolemic ones. 7 The mean BP consists of the product of two hemodynamic parameters (CO and SVR), and arterial hypertension is the result of a disorder in one or both hemodynamic variables. 40 These findings, associated with the fact that the results obtained with empirical therapy based on current guidelines are suboptimal, have led some specialists to propose new approach pathways for the hypertensive patient, particularly a therapeutic approach guided by the patient’s hemodynamic profile. 41-45 Historically, the use of BP as an indicator of cardiovascular status in hypertensive patients comes from the fact that hemodynamic parameters are assessed using invasive techniques. 46 More recently, echocardiography has been used to accurately estimate CO, but when comparedwith ICG, the latter was considered more time-consuming and technically demanding. 19 Thus, ICG emerges as a non-invasive, simple, accurate and inexpensive method to evaluate patients hemodynamically, characterizing the profile and guiding the therapeutic optimization in hypertensive patients. 44,45,47 The use of ICG can improve our knowledge about arterial hypertension, especially regarding its hemodynamic characteristics and consequences. Hypertensive cardiopathy is a continuum, involving structural changes (myocardial fibrosis) and left ventricular geometry (hypertrophy and concentric remodeling), which progressively develop into systolic and/or diastolic function disorder. 48 Close to its end, the IMPEDDANS study (ClinicalTrials.gov; Identifier: NCT03209141) intends to verify the ability to screen for left ventricular diastolic dysfunction in its asymptomatic phase in hypertensive patients, whichmay allow an early diagnosis, as well as the study of the disease evolution and therapeutics. The growing interest in hemodynamic changes in arterial hypertension and orthostatic and emotional stress responses, led researchers to use ICG to study autonomic dysfunction in hypertension. The technological evolution of the ICG, with the development of monitors for the assessment of outpatients, is a new area of ​research in arterial hypertension. With this technique, one can assess cardiac performance for 24 to 48 hours, as well as the hemodynamic changes that occur during Daily Life Activities, and the hemodynamic responses to changes in body position and blood pressure control, for instance. 49-53 Antihypertensive therapy guided by impedance cardiography Hypertensionmanagement includes lifestylemeasures such as sodium restriction and weight loss, and, in most cases, the use of one or more antihypertensive drugs. Considering this approach to arterial hypertension as a hemodynamic pathology, drugs are proposed according to the pathophysiological mechanism responsible for BP increase (Figure 3). Drugs a r e s e l ec t ed ac cord i ng t o e l eva t ed hemodynamic parameters. Therefore, it is first