IJCS | Volume 31, Nº3, May/ June 2018

DOI: 10.5935/2359-4802.20180008 282 REVIEW ARTICLE International Journal of Cardiovascular Sciences. 2018;31(3)282-289 Mailing Address: Lucelia dos Santos Silva Rua Otavio Mangabeira, 2031. Postal Code: 25555-120, Jardim Meriti, São João de Meriti, Rio de Janeiro, RJ - Brazil. E-mail: luceliasantos.ufrj@gmail.com , luceliasantos.cap31@gmail.com Accuracy of Impedance Cardiography in Acute Myocardial Infarction: A Literature Review Lucelia dos Santos Silva, Fernanda Faria Reis, Monyque Evelyn Santos Silva, Dalmo Valerio Machado de Lima Programa de Pós-graduação em Ciências Cardiovasculares da Universidade Federal Fluminense (UFF), Niterói, RJ - Brazil Manuscript received August 29, 2016, revised manuscript October 25, 2017, accepted November 14, 2017. Myocardial Infarction / physiopathology; Data Accuracy; Hemodynamics; Cardiography, Impedance; Electric Impedance. Keywords measures the electrical resistance at high frequencies with low steady current amplitude (1.5 mA, 86 KHZ) generated by external sensors and electrodes (in the thoracic and cervical regions) that capture instantaneous voltage changes. 3 The device behaves according to Ohm’s law: when a steady current is applied to the thorax, the voltage changes are directly proportional to the impedance changes. The total thoracic impedance, named baseline impedance (Z), is the sumof the impedance of all thoracic components (adipose tissue, heart, lung, skeletal muscle, vascular tissue, bones and air). 4 The electrodes sense the Z change resulting from the pulsatile blood flow through the descending aorta during systole and diastole. Over time, this alteration has a direct impact on the left ventricular contractility. The alteration of Z is converted to stroke volume and cardiac output values using mathematical algorithms. The other hemodynamic variables are measured or calculated from the ICG data and provided on a continuous and real-time basis. 3,4 Major studies demonstrate the efficacy of this method, making possible an early evaluation of heart failure, treatment guidelines in hypertension and monitoring of hemodynamic performance in acute myocardial infarction and in the postoperative of cardiac surgery. Normally, these hemodynamic measurements would be obtained for only the most critically-ill patients, such as Swan-Ganz catheter monitoring. However, due to the risk, discomfort, and cost of invasive procedures, bioimpedance is considered safer andmore economical. 4 Impedance cardiography has been an attractive alternative for determining body composition, since Introduction Hemodynamic monitoring of individuals with acute myocardial infarction, for evaluation of progression and prognosis of the patient’s clinical picture, has been studied for years. The Swan-Ganz catheter is an invasive hemodynamic monitoring measurement, indicated for clinical situations, such as acute heart failure (e.g. acute myocardial infarction, complicated by progressive hypotension or cardiogenic shock); mechanical complications of acute myocardial infarction; right ventricular infarction; refractory congestive heart failure; pulmonary hypertension. 1 Although there are indications, there is no consensus among them, since there is an enormous amount of work published on the clinical use of the Swan-Ganz catheter, but with doubtful methodology, allowing controversies regarding its true indications. Moreover, some authors have even published test results correlating the use of the Swan-Ganz catheter with increased mortality. 1,2 Electrical impedance cardiography (ICG) or thoracic bioimpedance, among other forms of monitoring, is a noninvasive method for the estimation of hemodynamic variables. The method assumes that the thorax is a homogeneous fluid cylinder, composed of blood tissue, air and organs, with a specific resistance, and thus