402 a simplified echocardiographic formula to estimate cardiac index in the intensive care unit

Abstract Background and aim Measurement of cardiac index (CI) is crucial in the hemodynamic assessment of critically ill patients in the intensive care unit (ICU). The most reliable trans-thoracic echocardiography (TTE) technique for CI estimation is the left ventricular outflow tract (LVOT) Doppler method that requires, among other parameters, the LVOT cross-sectional area (CSA) measurement. However, geometrical assumptions inherent limitations and practical disadvantages related to the ICU setting, hamper LVOT-CSA assessment. In this study, we aimed to validate a simplified formula, leveraging only on LVOT-velocity time integral (VTI) and heart rate (HR) variables, for the non-invasive estimation of CI in ICU patients. Methods and Results We prospectively enrolled 50 consecutive patients admitted to our ICU requiring PAC over a one-year period. For each patient we measured the CI by PAC (CIPAC) and TTE. The latter was obtained both with the “traditional formula” (traditional CITTE), requiring LVOT-CSA assessment, and our new “simplified formula” (simplified CITTE). The correlation between the simplified CITTE and CIPAC was strong (r = 0.81) and resulted significantly greater than the traditional CITTE and CIPAC correlation (r = 0.70; p < 0.05 for Pearson r coefficients comparison). Both TTE-based CI showed an acceptable agreement (+0.19±0.48 L/min/m2 for simplified CITTE and -0.18±0.58 L/min/m2 for traditional CITTE) with the reference CIPAC. Conclusion In this study, we propose an easy-to-use and practical approach, leveraging on TTE LVOT-VTI and HR only, for non-invasive estimation of CI in ICU patients.