Accuracy, Precision, and Trending Ability of Uncalibrated Arterial Pressure Waveform Analysis of Cardiac Output in Patients With Impaired Left Ventricular Function: A Prospective, Observational Study

Objectives: Uncalibrated arterial waveform analysis provides minimally invasive and continuous measurement of cardiac output (CO). This technique could be of great value in patients with impaired left ventricular function, but the validity in these patients is not well established. The aim of this study was to investigate the accuracy, precision, and trending ability of uncalibrated arterial waveform analysis of cardiac output in patients with impaired left ventricular function. Design: Prospective, observational, method-comparison study. Setting: Nonuniversity teaching hospital, single center. Participants: The study included 22 patients with a left ventricular ejection fraction of 40% or less undergoing elective coronary artery bypass grafting. Interventions: In the period between induction of anesthesia and sternotomy, CO was measured using the FloTrac/Vigileo system (third-generation software) and intermittent pulmonary artery thermodilution before and after volume loading. Measurements and Main Results: Accuracy and precision as determined using Bland-Altman analysis revealed a bias of -0.7 L/min, limits of agreement of -2.9 to 1.5 L/min, and a mean error of 55% for pooled data. Proportional bias and spread were present, indicating that bias and limits of agreement were underestimated for high CO values. Trending ability was assessed using 4-quadrant analysis, which revealed a concordance of 86%. Concordance from a clinical perspective was 36%. Polar plot analysis showed an angular bias of 13 degrees, with radial limits of agreement of -55 degrees to 51 degrees. Polar concordance at +/- 30 degrees was 50%. Conclusions: Arterial waveform analysis of cardiac output and pulmonary artery thermodilution cardiac output were not interchangeable in patients with impaired left ventricular function.