Discordant Gradients after TAVR: Balloon vs Self Expanding Valves

Background
In patients undergoing transcatheter aortic valve replacement (TAVR), prosthesis gradients are employed for surveillance of valve function and durability. The reliability of these gradients is important as they often drive clinical decision making. Although theoretical limitations of doppler and invasively derived gradients have been established, a direct comparison of these gradients in the post-TAVR population has not previously been reported.

Methods
We retrospectively reviewed patients that underwent TAVR between January 2017 and March 2018. We compared the invasive gradients acquired after valve deployment with those obtained by transthoracic Doppler echocardiography within 24 hours of the procedure. Invasive gradients were obtained via simultaneous recording of left ventricular and ascending aortic pressures. Doppler derived gradients were obtained from the echocardiographic window with the highest velocity. All TAVR procedures were performed with conscious sedation.

Results
The cohort included 86 patients that received Sapien and 118 that received Corevalve prostheses. Mean gradients obtained invasively (Sapien 3.9 mm Hg, CoreValve 3.6 mm Hg) were significantly lower than Doppler derived gradients (Sapien 12.3 mm Hg, CoreValve 9.1 mm Hg) irrespective of valve type (p < 0.01). The difference between invasive and Doppler derived gradients was greater with Sapien valves, although this did not reach statistical significance (p = 0.10).

Conclusions
Doppler-derived gradients acquired after TAVR are higher than those obtained invasively post-procedure. This difference is greater with Sapien valves. These differences may reflect changes in cardiac output or systemic vascular resistance between the two procedures, or to technique related issues such as in stent flow acceleration or pressure recovery with Doppler-derived gradients. Whether or not the discordance is related to prosthesis type or size is the subject of ongoing analysis.