Standardized Invasive Hemodynamics for Monitoring Acute and Long Term Valve Performance in Patients With Elevated Gradients Post Transcatheter Aortic Valve Replacement

Since the introduction of Doppler echocardiography, non-invasive estimation of aortic valve gradients through modification and simplification of the Bernoulli equation and derivation of the AVA, via the continuity equation, have become the primary method to assess the severity of AS.

The utility of echocardiography to successfully determine aortic valve gradients and AVA has been established in the presence of AS, and such observations have been extrapolated to prosthetic valves. However, several reports following SAVR and TAVR for both native and valve-in-valve have demonstrated significant discordance between echocardiography-derived and direct invasive measurements of aortic valve mean gradients.

The indexed AVA (iAVA) is derived from the stroke volume indexed to the BSA. The stroke volume index (SVI) divided by the Doppler velocity time integral of the continuous wave aortic valve spectral profile, is used to determine the presence of severe PPM. As such, a low iAVA may occur due to a low flow state defined by a reduced SVI (<35 ml/m2) or a reduced stroke flow rate (< 200 ml/second) and calculated by dividing the SV by the ejection time spuriously increasing the incidence of severe PPM. A low indexed effective orifice area due to a low SVI, in the absence of intrinsic PPM, has been referred to as "pseudo-severe PPM", but the impact of flow state on PPM has not been described.

Nonetheless, echocardiographic thresholds for the evaluation of prosthetic valve performance after TAVR have been widely adopted: mean-gradient > 20mmHg, severe PPM as defined by an iAVA < 0.65 cm2/m2, and AR, including paravalvular and transvalvular AR of moderate or greater severity. These criteria are suggested to indicate procedural success and predict long-term clinical outcomes (12). Practically many centers utilize an echocardiography-derived mean gradient for the follow-up of transcatheter heart valves. While the association of at least moderate paravalvular AR with mortality has been consistently demonstrated, there remains uncertainty regarding the clinical impact of severe PPM as determined by index echocardiography. Furthermore, the magnitude of discordance between echocardiography-derived and invasive aortic valve mean-gradients post TAVR is unknown and it remains unclear how to reconcile measurement discordances in clinical practice. These potential differences may have an important impact on patient management post TAVR.

The DISCORDANCE TAVR study will determine the discordance between echocardiography-derived and invasive transaortic gradients, as determined by a consistent and reproducible technique (Standardized Invasive Hemodynamics) post-TAVR.