Volume 4 Supplement 1
Evaluation of thoracic fluid contents in patients with acute myocardial infarction
© Current Science Ltd 2000
Published: 21 March 2000
It is common to evaluate patients with acute myocardial infarction (AMI) according to the Forrester classification. A high PCWP value is a good predictor of pulmonary congestion although there is no documented correlation between PCWP and the degree of pulmonary congestion in patients with normal PCWP. In this study, we sought to investigate the correlation between (1) PCWP and thoracic fluid contents (TFC) as an indicator of pulmonary congestion, (2) PCWP and cardiac index (CI) and (3) CI and TFC in patients with AMI with PCWP values <18 mmHg. The thoracic electrical bioimpedance (TEB) method was used to measure TFC and CI. CI was also measured by the thermodilution (TD) method.
Thirty-six patients with a diagnosis of AMI were included. Patients were monitored with the TEB device (BioZ System, CardioDynamics International Co, USA) and the pulmonary artery (PA) catheter, in addition to conventional monitoring. We measured CI by means of TEB and thermodilution (TD) methods (CI-TEB and CI-TD, respectively) and compared values obtained from each patient with those two methods. We also measured PCWP with the PA catheter, and TFC values as an indicator of pulmonary congestion with the TEB device. The correlation between PCWP and CI, PCWP and TFC, CI and TFC were also examined.
Patients were 29 males and 7 females and age was 65 ± 11 years (mean ± SD). All the patients had AMI in the left ventricle. CI-TEB and CI-TD were positively correlated(r2=0.75). CI-TD was inversely correlated with PCWP(r2=0.22). TFC was weakly correlated with PCWP(r2=0.26). Neither CI-TEB nor CI-TD had significant correlation with TFC (r2=0.01 and 0.02, respectively).
In this study, we confirmed that TEB method might be clinically useful for CI measurement in patients with AMI. PCWP was negatively correlated with CI-TD indicating that decreased CI in our patient group was not due to systemic dehydration but to decreased cardiac contractility. The weak correlation between PCWP and TFC means that the tendency of pulmonary water retention exists with an increasing PCWP even in patients with normal PCWP. The clinical importance of this increase in TFC is not clear. TFC values had no significant correlation with CI values. This means that the degree of pulmonary congestion is unpredictable from CI provided that PCWP remains normal. This is consistent with the Forrester classification.