To validate electrical cardiometry (EC) in pregnant patients using transthoracic echocardiography (TTE) as the reference standard. To improve EC accuracy via a one-time, measurement of left ventricular outflow tract (LVOT) diameter. 44 non-laboring, resting women with singleton, viable pregnancies underwent simultaneous EC and TTE measurements. Data were analyzed using Bland-Altman analysis. Entry multiple regression with stepwise elimination was used to develop a model for improved prediction of stroke volume by TTE (SVTTE) using EC. Bootstrapping and an 11-fold cross validation were used to test the model. Heart rate by TTE and EC had a mean bias of 3.3 beats/min and mean percentage error of 10.7 %. Envelope time and left ventricular ejection time had a mean bias of -4.9 ms and mean percentage error 12.7 %. Stroke volumes by the two techniques had a mean bias of 15.6 mL and mean percentage error of 43.7 %. A model, SVEC_Modified, predicting SVTTE was developed using LVOT area, stroke volume by electrical cardiometry and weight. SVTTE and SVEC_Modified had a mean bias of -0.83 mL and mean percentage error of 22 %. EC accurately measures heart rate and duration of systole when compared with TTE. Stroke volume measurements correlate but have a high bias and percentage error. Knowledge of LVOT area, by a one-time, measurement with TTE, could improve prediction of stroke volume by EC.
Keywords: Cardiac output; Electrical cardiometry; Impedance cardiography.