ABC | Volume 110, Nº2, February 2018

Original Article An Alternative Method to Calculate Simplified Projected Aortic Valve Area at Normal Flow Rate Joana Sofia Silva Moura Ferreira, Nádia Moreira, Rita Ferreira, Sofia Mendes, Rui Martins, Maria João Ferreira, Mariano Pego Centro Hospitalar e Universitário de Coimbra, Serviço de Cardiologia, Coimbra - Portugal Mailing Address: Joana Sofia Silva Moura Ferreira • Rua do Padrão, 479. Vila Maior, Coimbra - Portugal E-mail: joanasofia.moura@gmail.com , joanasofia_moura@hotmail.com Manuscript received November 08, 2016, revised manuscript June 29, 2017, accepted July 21, 2017 DOI: 10.5935/abc.20180018 Abstract Background: Simplified projected aortic valve area (EOA proj ) is a valuable echocardiographic parameter in the evaluation of low flow low gradient aortic stenosis (LFLG AS). Its widespread use in clinical practice is hampered by the laborious process of flow rate (Q) calculation. Objetive: This study proposes a less burdensome, alternative method of Q calculation to be incorporated in the original formula of EOA proj and measures the agreement between the new proposed method of EOA proj calculation and the original one. Methods: Retrospective observational single-institution study that included all consecutive patients with classic LFLG AS that showed a Q variation with dobutamine infusion ≥ |15|% by both calculation methods. Results: Twenty-two consecutive patients with classical LFLG AS who underwent dobutamine stress echocardiography were included. Nine patients showed a Q variation with dobutamine infusion calculated by both classical and alternative methods ≥ |15|% and were selected for further statistical analysis. Using the Bland-Altman method to assess agreement we found a systematic bias of 0,037 cm 2 (95% CI 0,004 – 0,066), meaning that on average the new method overestimates the EOA proj in 0,037 cm 2 compared to the original method. The 95% limits of agreement are narrow (from -0,04 cm 2 to 0,12 cm 2 ), meaning that for 95% of individuals, EOA proj calculated by the new method would be between 0,04 cm 2 less to 0,12 cm 2 more than the EOA proj calculated by the original equation. Conclusion: The bias and 95% limits of agreement of the new method are narrow and not clinically relevant, supporting the potential interchangeability of the twomethods of EOA proj calculation. As the newmethod requires less additional measurements, it would be easier to implement in clinical practice, promoting an increase in the use of EOA proj . (Arq Bras Cardiol. 2018; 110(2):132-139) Keywords: Aortic Valve Stenosis / diagnosis; Aortic Valve Stenosis / diagnostic imaging; Echocardiography, Stress; Heart Valves / physiopathology. Introduction Classical low-flow, low-gradient (LFLG) aortic stenosis (AS) is characterized by the combination of a calcified aortic valve with an effective orifice area (EOA) compatible with severe stenosis, a low transvalvular velocity or pressure gradient suggestive of moderate stenosis and a low left ventricular ejection fraction (LVEF). 1 Dobutamine stress echocardiography (DSE) may aid in the distinction between patients with true severe AS and those with pseudo-severe AS by promoting a potential increase in flow. Hence, traditional hemodynamic indices of stenosis severity could be evaluated at normal flow rates and easily interpreted. 2 The main limitation of this exam is the unpredictability of flow augmentation, leading to ambiguous changes of mean pressure gradient and EOA. 3 Projected aortic valve area at normal transvalvular flow rate (250 mL/min) – EOA proj - is an echocardiographic parameter that was developed in order to overcome this limitation. It consists of the effective orifice aortic area that would have occurred at a standardized flow rate of 250 mL/min, enabling the comparison of AS severity between patients with different flow rate profiles with dobutamine infusion. 4 The determination of this new parameter requires the calculation of at least the basal and peak flow rate in each patient. The original formula of EOA proj published by Blais et al . proposed the calculation of flow rate as the quotient between stroke volume and the ejection time (ET), which requires 3 different measurements: 1) left ventricular outflow tract (LVOT) diameter; 2) LVOT velocity-time integral and 3) ET measured at the aortic velocity spectrum. 4 Flow rate can also be determined by the product of LVOT area and LVOT mean velocity, which requires only 2 measurements: 1) LVOT diameter and 2) LVOT mean velocity. 5 This alternative method to calculate flow rate is less cumbersome and less susceptible to inter-observer and intra-observer variability as it requires less measurements. 132