Evaluation of diuretic therapy by impedance cardiography in acute myocardial infarction

Abstract

Summary:Changes in transthoracic electrical impedance (TEI) were recorded in 20 patients with acute myocardial infarction before, during, and 60 min after intravenous administration of furosemide (Impuganm). The major change was an increase in TEI (ZO) (6.2%, p<O.OOl). The mean impedance stroke volume (n = 10) decreased by 7.8% (p<0.05) while the mean impedance cardiac output (n = 10) decreased by 6.3% (p>0.05). Heart rate and blood pressure remained unchanged. It was possible to differentiate between two types of TEI changes after furosemide. In 10 patients there was an early and rapid increase in ZO (type A), while the rest of the patients showed a decreased or unchanged ZO followed by a slow increase (type-B). The line describing the mean ZO change in type A was significantly higher than that of type B and fell outside f 2 SEM of the line describing the mean ZO change found in five normal subjects (type C). The ZO change in type B was similar to that in type C. It is assumed that Z , change in type A may represent patients with an increased amount of extravascular fluid (heart failure), while the change in type B represents patients without heart failure. This assumption is based on the difference in dependency of TEI on extravascular volume versus intravascular volume changes. It is suggested that the impedance method may be used as a simple noninvasive method to assess the effect of diuretic therapy and may have the value of detecting extravascular thoracic fluids in acute myocardial infarction.

Effects of furosemide and slow‐release furosemide on thoracic fluid volumes

“…After half an hour's rest in the supine position the impedance was measured, in the postexpiratory resting phase, during normal breathing, before, then 15,30,45, and 60 minutes after an intravenous injection of 40 mg furosemide. The values measured after the injection were expressed as percent change of the initial value (Gabriel et al, 1980). The urine production was also measured during the 60 min of impedance measurement.…”

“…A major pathophysiological factor behind the clinical signs and symptoms of congestive heart failure is the amount of blood and water (edema) in the thoracic cavity. It has been shown (Gabriel et al, 1980), that these volumes may be measured by the method of transthoracic electrical impedance (TEI). The aim of the present study was to evaluate if 60 mg FR has the same effectiveness as 40 mg F in reducing the fluid content in the thoracic cavity.…”