Pressure Recovery Phenomenon in Aortic Stenosis. An Inconvenient Truth?

IN THIS issue of the Journal Cardiothoracic and Vascular Anesthesia, Dietrich et al. presented an E-Challenge a patient with progressive dyspnea elevated mean transvalvular gradient one year after aortic valve replacement despite normal leaflet motion.1Dietrich M Mankad R. Elevated prosthetic gradients: What to consider when determining etiology.J Cardiothorac Vasc Anesth. 2021; 35: 2223-2227Abstract Full Text PDF Scopus (1) Google Scholar The readers are asked about etiology gradient. authors posited that pressure recovery (PR) is most likely explanation for difference in pressures between Doppler echocardiography cardiac catheterization. In 1976, Holen first described how measurement gradients across stenotic mitral could be determined noninvasively using continuous-wave ultrasound.2Holen J Aaslid R Landmark K al.Determination stenosis non-invasive ultrasound technique.Acta Med Scand. 1976; 199: 455-460Crossref PubMed (212) Successive studies made by Hatle confirmed these observations stenosis, extended use include patients (AS).3Hatle L Brubakk A Tromsdal al.Noninvasive assessment drop ultrasound.Br Heart J. 1978; 40: 131-140Crossref (378) Scholar,4Hatle Angelsen BA A. Non-invasive 1980; 43: 284-292Crossref (383) Since then, has been used routinely as noninvasive technique measure AS. There close correlation peak catheter peak-to-peak gradients, overestimation relative catheterization.5Agatston AS Chengot Rao al.Doppler diagnosis valvular over 60 years age.Am Cardiol. 1985; 56: 106-109Abstract (26) This due PR phenomenon. order fully understand complexity fluid dynamics through subsequent phenomenon, law conservation energy blood accelerates constriction must described. states can neither created nor destroyed, but rather change form (eg, gravitational potential transformed into kinetic object falls). When applied left ventricle (LV), LV proximal stored static secondary exerted walls contracting LV. As opens gains motion, blood's decreases, converted (energy movement). approaches flow streams converge contract toward orifice. vena contracta point where streamlines maximally constricted, achieved its maximal velocity (maximal energy) least (decreased conversion energy. phenomenon originally was Evangelista Torricelli, pupil Galileo Galilei, 1643. continues ascending aorta, will decrease while increases. Kinetic reconverted aorta defined PR. reconversion unstable. Energy lost from system heat turbulence, vortex formation, friction caused abrupt geometry, receiving chamber size, stagnant sinuses. Garcia proposed coefficient measured estimates severity taking consideration loss occurs stenosis.6Garcia D Pibarot P Dumesnil JG al.Assessment severity: new index based on concept.Circulation. 2000; 101: 765-771Crossref (272) this (ELCO) similar traditional Gorlin equation clinically during catheterization measurement. explains given rate, increases decreasing area (AVA) increasing cross-sectional (Aa), represented following formula6Garcia Scholar:ELCO=(AVA×Aa)/(Aa−AVA). ELCO reconciles discrepancies catheterization, adjusting AVA Furthermore, represents actual workload encounters Scholar,7Garcia Durand LG al.Discrepancies effective orifice predicted phenomenon: Practical implications regard quantification severity.J Am Coll 2003; 41: 435-442Crossref (181) It sinotubular junction level at which occurs.7Garcia last 25 years, broadly studied. Current guidelines echocardiographic recommend only considered diameter less than 30 mm bileaflet mechanical valves.8Baumgartner H Hung Bermejo al.Recommendations stenosis: focused update European Association Cardiovascular Imaging American Society Echocardiography.J Soc Echocardiogr. 2017; 30: 372-392Abstract (536) recommendations native valves study 1999 cohort 23 patients.9Baumgartner Stefenelli T Niederberger al.Overestimation" predictable manifestation recovery.J 1999; 33: 1655-1661Crossref (249) With valves, thought influenced design size.10Bech-Hanssen O Caidahl Wallentin I al.Aortic size: Relation findings recovery- vitro study.J 13: 39-50PubMed recent data have published respect adjustment, reclassify severity. Bahlmann found 48% reclassification severe moderate asymptomatic Simvastatin Ezetimibe Aortic Stenosis (SEAS) trial database taken consideration.11Bahlmann E Cramariuc Gerdts al.Impact SEAS substudy.JACC Cardiovasc Imaging. 2010; 3: 555-562Crossref (95) Heo 24.8% had their reclassified correct 12Heo Jin X Oh JK al.Clinical usefulness adjustment predominantly Asian registry data.J 2020; 33 (332-41.e2)Abstract (7) more 95% reclassifications occurred 35 mm, mmHg, AVAs 0.8 1.0 cm2. Notably, 19.8% who were contrast what previously described.8Baumgartner Scholar,9Baumgartner sentinel finding four-year clinical event-free survival compared those corrected aforementioned formula, accounts (50.9% v 46.2%, respectively). shown important low-gradient Altes 39% rates moderate, two-fold risk reduction events follow-up.13Altes Ringle Bohbot Y significance preserved ejection fraction.Eur 21: 608-615Crossref (9) Similar findings, 45% initially classified AS, having AS.12Heo Multimodal imaging also employed, multidetector computed tomography LVOT, resulting 43% ELCO.14Holy EW Nguyen-Kim TDL Hoffelner al.Multimodality derived outcome transcatheter replacement.Eur 1092-1102Crossref (4) Looking future, computational dynamic (CFD) 3D models root may provide us answers. novel image-based CFD workflow heart allowed computation resistance demonstrate contribution aorta.15Hoeijmakers MJMM Silva Soto DA Waechter-Stehle al.Estimation segmented dynamics.J Biomech. 2019; 94: 49-58Crossref (13) demonstrated showed complement measurements discordant grading, simplified model, estimation valve. aid further understanding hydraulics passes flows aorta. involve modeling account factors impact unique way. multiple modalities, including echocardiography, tomography, perhaps even magnetic resonance imaging, permit patient-specific approach Although valve,1Dietrich existing literature suggests underappreciated, both valves. Incorporating calculations prudent solely care patients. bottom line should done not prosthetics small aortas, regardless size. Having awareness effects it allow clinicians properly time procedures potentially avoid high-risk, unnecessary interventions. None. Prosthetic Valve Gradients: Consider Determining EtiologyJournal AnesthesiaVol. 35Issue 7PreviewDOPPLER useful tool hemodynamics. However, subject limitations implications, especially setting prosthesis. Elevation variety etiologies. One such pressure-recovery consequence stream convergence narrowing, artifact flow. Full-Text