Prognosis of acute myocardial infarction outcomes using evaluation of cardiac power (product of cardiac output and mean arterial pressure)

Introduction

Insufficient reliability and specificity of cardiac output (CO) as a widely used parameter for prognosis of acute myocardial infarction (AMI) outcomes led to investigations and a search for new methods and parameters. Cardiac power (CP) (a parameter proportional to the product of CO and mean arterial pressure) was introduced after studies mainly performed using the invasive intermittent thermodilution (ITD) technique. The aim of this study was to investigate the reliability and specificity of the new parameter mainly by means of noninvasive techniques such as impedance cardiography (ICG).

Methods

CO and CP were evaluated by both ITD and ICG methods in patients with AMI, admitted within 12 hours from the onset of pain. CP was evaluated using the suggested formula: CP = CO × MAP/451, where MAP = mean arterial pressure. During the period of 2004 to 2008, 289 (196 men and 93 women) patients were investigated. The standard eight-electrode ICG registration was used. The optimal binning method using the minimal description length principle was used to predict outcomes after AMI: inhospital mortality, survival after 6 months and survival after 12 months.

Results

CP evaluated on the first day was found as the only valuable prognostic parameter using the model entropy method in the group of patients where noninvasive evaluation of CO was used. Inhospital mortality was predicted with single cut point 0.65, sensitivity 100% and specificity 92.2%, while survival of 12 months was predicted with single cut point 0.90, sensitivity 88.9% and specificity 73.0%. Only prediction of inhospital mortality was possible in the group of patients where CO was evaluated using the ITD technique. The most significant criteria using minimized entropy model were CP evaluated on the third day (single cut point 0.79, sensitivity 84.6%, specificity 100.0%) and CO evaluated also on the third day (single cut point 4.00, sensitivity 84.6%, specificity 100.0%).

Conclusion

Cardiac power is a reliable predictor for inhospital mortality and survival within the first year after acute myocardial infarction. It could be evaluated using ITD and with sufficient accuracy by means of a noninvasive method – ICG – as well.