ABC | Volume 110, Nº2, February 2018

Original Article Ferreira et al Alternative method to calculate simplified EOA proj Arq Bras Cardiol. 2018; 110(2):132-139 Figure 1 – Scatter plot showing the classic simplified projected aortic valve area values against the alternative simplified projected aortic valve area values with a superimposed regression line (solid line) with 95% confidence bands (dashed lines). 0.0 0.0 0.5 0.5 1.0 1.0 1.5 1.5 2.0 2.0 EOA proj Alternative Method EOA proj Classic Method Figure 2 – Bland-Altman plot, in which the difference of the two paired EOA proj measurements is plotted against their mean. The solid line parallel to the x axis represents the bias and the dashed lines parallel to the x axis represent the limits of agreement. 0.15 0.10 0.05 0.5 1.0 2.0 1.5 0.00 –0.05 –0.10 Average Difference (by estimating the mean of the differences for individuals – the systematic bias) and how well the measurements agree for individuals (by examining the variability of the differences and the calculation of the limits of agreement which quantify the range of values that can be expected to cover agreement for most of the subjects). 10 Using the Bland-Altman method, we found a systematic bias of 0.037 cm 2 (95% CI 0.004 – 0.066), meaning that on average the alternative method overestimates the EOA proj in 0,037 cm 2 compared to the classic method. Despite being statistically significant, this bias is not clinically significant as it is less than 0.1 cm 2 . Also, the 95% limits of agreement are quite narrow (from -0,04 cm 2 to 0,12 cm 2 ), meaning that for 95% of individuals, EOA proj calculated by the alternative method would be between 0,04 cm 2 less to 0,12 cm 2 more than the EOA proj calculated by the classic equation. Such narrow range is the largest likely differences between the two methods, and do not compromise the clinical agreement between the two methods. Therefore, it is reasonable to acknowledge the potential interchangeability of the two methods of EOA proj calculation in clinical practice. Conclusion This study presented a new method to calculate the simplified EOA of the aortic valve at normal flow rate using a less cumbersome equation to estimate flow rate and tested the agreement of this new method with the previous reported by Blais et al. 4 The bias and 95% limits of agreement of the new method are narrow and not clinically relevant, supporting the potential interchangeable use of 137