Comparison of Systolic Time Ratio from Electrical Cardiometry Versus Echocardiography for Evaluation of Left Ventricular Systolic Function in Patients Undergoing Cardiac Surgery: A Prospective Observational Study

Abstract

To identify the correlation between systolic time ratio(STR) measured with electrical cardiometry (EC) device ICON (Osypka Medical, Berlin, Germany) and echocardiography in patients undergoing cardiac surgery and to find a noninvasive technique for estimating left ventricular systolic function during the perioperative period. Systolic time ratio data were obtained simultaneously from the electrical cardiometry device ICON (Osypka Medical, Berlin, Germany) and transthoracic echocardiography at the following predefined timepoints— before anaesthesia induction (T0 baseline), after induction (T1), at the end of the surgery(T2), and after extubation (T3) in patients undergoing elective cardiac surgery. The agreement between the systolic time ratio measured by electrical cardiometry and transthoracic echocardiography was studied using Bland-Altman plots. Paired t-tests were used to compare systolic time ratio measurements at different time points. Mean STR by EC and Echocardiography at T0 was 0.456 (0.429-0.483) and 0.348 (0.330-.366) at T1 was 0.464 (0.442 -0.486) and 0.372 (0.344-0.401) at T2 was 0.421 (0.402 -0.439) and 0.305 (0.290-0.320) and at T3 was 0.438 (0.419-0.457) and 0.353 (0.336-0.370), P value <0.001. Bland-Altman analysis showed that EC measured STR compared with echocardiography at T0 with a mean bias of 0.108 and (with limits of agreement -0.19 ,0.14) at T1 it was 0.092 (with limits of agreement -0.21,0.40) at T2 it was 0.11 (with limits of agreement -0.04,0.28) and at T3 it was 0.085 (with limits of agreement -0.101 ,0.271). In conclusion, no association between systolic time ratio as measured by electrical cardiometry and echocardiography was found in our study. Our results do not conclusively prohibit using electrical cardiometry in the perioperative period to evaluate LV systolic function. Further work must be done to establish the role of STR as a surrogate marker of LV systolic function.