What is the phenomenon of pressure recovery in aortic stenosis?

What is the phenomenon of pressure recovery in aortic stenosis?

Phenomenon of pressure recovery in aortic stenosis: Systolic pressure in the aorta will be lower immediately distal to the valve, while it ‘recovers’ to a higher value more distally in the aorta. Hence the pressure gradient measured by cardiac catheterization will be lower than what is measured by Doppler echocardiography, even after accounting for the difference between peak to peak gradient and peak instantaneous pressure gradient. It may be noted that Doppler measures peak instantaneous gradient while cath measures peak to peak gradient which is lower. The lower pressure near the valve is due to the effect of the jet which causes a reduction in the lateral pressure. To get the recovered pressure (settled pressure), catheter has to be pulled back about 2 to 3 cm beyond the sino-tubular junction.

It has been suggested that there may be an overestimation of severity of aortic stenosis due to pressure recovery in a subgroup of patients with an apparently severe aortic stenosis, but not having significant left ventricular hypertrophy [1].

Another in vitro study suggested that differences between catheter and Doppler gradients can reach clinical relevance especially when the stenosis is moderate and the aorta small [2].

Analysis of Asian Valve Registry of 697 patients with aortic stenosis was done by Heo R et al [3]. After adjustment for pressure recovery, 24.8% of the patients with severe aortic stenosis were reclassified as moderate aortic stenosis. Adjustment for pressure recovery also decreased the frequency of low gradient severe aortic stenosis from 22.4% to 10.2%. Most of the reclassifications occurred in those with aortic dimension less than 3.5 cm, mean gradient less than 60 mm Hg or aortic valve area between 0.8 to 1.0 sq. cm. Those reclassified had a higher four year clinical event free survival rate.

Bahlmann E et al have also shown that a small aortic root was associated with a higher pressure recovery [4].

Non invasive determination of pressure recovery by cardiac magnetic resonance imaging (CMR) and echocardiography has been described by Sagmeister F et al [5]. In their study of 25 patients, reclassification occurred in 12-20% of patients with aortic stenosis using CMR.

References

1. Ayumu Abe, Taisei Mikami, Sanae Kaga, Kanako Tsuji, Kazunori Okada, Shinobu Yokoyama, Hisao Nishino, Masahiro Nakabachi, Mutsumi Nishida, Chikara Shimizu, Hiroyuki Iwano, Satoshi Yamada, Hiroyuki Tsutsui. Coexisting Cardiac Diseases and Pressure Recovery Phenomenon Contribute to Discrepancy Between the Echocardiographic Severity of Aortic Stenosis and Left Ventricular Hypertrophy. J Echocardiogr. 2013 Jun;11(2):41-9.
2. J Niederberger, H Schima, G Maurer, H Baumgartner. Importance of Pressure Recovery for the Assessment of Aortic Stenosis by Doppler Ultrasound. Role of Aortic Size, Aortic Valve Area, and Direction of the Stenotic Jet in Vitro. Circulation. 1996 Oct 15;94(8):1934-40.
3. Heo R, Jin X, Oh JK, Kim YJ, Park SJ, Park SW, Ling LH, Fukuda S, Otsuji Y, Sohn DW, Song JK. Clinical Usefulness of Pressure Recovery Adjustment in Patients with Predominantly Severe Aortic Stenosis: Asian Valve Registry Data. J Am Soc Echocardiogr. 2020 Mar;33(3):332-341.e2.
4. Bahlmann E, Cramariuc D, Minners J, Lønnebakken MT, Ray S, Gohlke-Baerwolf C, Nienaber CA, Jander N, Seifert R, Chambers JB, Kuck KH, Gerdts E. Small aortic root in aortic valve stenosis: clinical characteristics and prognostic implications. Eur Heart J Cardiovasc Imaging. 2017 Apr 1;18(4):404-412.
5. Sagmeister F, Herrmann S, Gassenmaier T, Bernhardt P, Rasche V, Liebold A, Weidemann F, Brunner H, Beer M. Non-invasive determination of pressure recovery by cardiac MRI and echocardiography in patients with severe aortic stenosis: short and long-term outcome prediction. J Int Med Res. 2020 Oct;48(10):300060520954708.