OUR EXPERIENCE WITH THE USE OF IMPEDANCE CARDIOGRAPHY TO MONITOR HAEMODYNAMICS IN PATIENTS WITH ACUTE HEART FAILURE – COMPARISON WITH TERMODILUTION

Objectives:The method of impedance cardiography (ICG) is based on Ohm's law:the ICG electrodes apply an alternating electrical current to the thorax and measure the corresponding voltage to detect changes in thoracic impedance which is dependant on blood volum in the thorax.Variables such as cardiac output/index (CO,CI),stroke volum/index (SV,SI),systemic vascular resistence/index (SVR,SVRI) etc. can be derived.Several studies have proved its validity,safety and considerable cost and risk when compared to invasive technicques.Correlations of CO and CI calculations to bolus termodilution (BT) and direct Fick methods vary from 0,73 to 0,93.
Aim:To compare BT and ICG results in patients with acute heart failure on mechanical ventilation and unconscious by whom such data is missing.
Method:We used ICG with beat-to-beat blood pressure monitoring as a part of Task Force Monitor® device to check haemodynamic state in patients admitted to coronary unit with acute heart failure,all mechanically ventilated,unconscious.We recorded 10-minute ICG digital strips right after having measured CO,CI,SV and SVRI using bolus termodilution. We used average values of ICG and mean values of 5 BT measurements.
Results:We included 8 paired measurements (BT vs ICG) performed on 4 patients in different clinical states.Mean CO was 5,26 vs 4,61l/min, CI 2,51 vs 2,26l/min/m2,Spearman corr. index 0,90 and 0,97 (p<0,01).Mean SV was 49,6 vs 42,6ml,SVRI 2244 vs 2920dynescm5/m2,Spearman corr. index 0,10 and 0,64 (both NS).
Conclusion:We confirmed that measuring of CO and CI in heart failure patients in critical state using modern ICG monitoring systems is highly comparable to bolus termodilution method.It is a non-invasive,safe and easy-to-read device providing a beat-to-beat analysis. Other variables like SVRI and SV were useful in monitoring trends rather then providing absolute values.