1. Accounting for Pressure Recovery in Severe Aortic Stenosis:
Worth the Effort?
Sameer Tatavarty MBBS,, Hemalatha Raghuraman M.Phil, Stefan Buchholz FRACP
Department of Cardiology, Mackay Base Hospital, Mackay, Central Queensland
Introduction
Pressure Recovery Equation3
Results (continued)
Pressure recovery (PR) has been shown to occur distal to a stenotic aortic valve, and its magnitude is primarily influenced by the ratio of the effective valve area to the area of the aortic root. It has only recently been appreciated that PR may be clinically important in correctly classifying aortic stenosis (AS) severity. Formula based approximations of catheter-based transvalvular gradients by Doppler echocardiography using PR have previously been validated by Barker et al.,1 and its numerical impact studied by Bahlmann et al.2 We sought to investigate the implications on real world clinical grading of AS from severe to non-severe based on instantaneous peak systolic pressure gradient (PSG), taking into account body surface area (BSA) and indexed aortic valve area (AVAI). In addition, we sought to identify clinical and echocardiographic parameters that might identify those patients who would benefit most from PR correction.
Table 2. Re-classification from severe to non-severe AS based on PSG.
v = Peak aortic velocity (m/s)
AVA = Effective aortic valve area derived from continuity equation
AoA = Aortic cross sectional area derived from aortic root diameter at the level of the sinus of Valsalva
Results
The mean pressure recovery gradient was 14 +/- 5 mmHg (range 6 – 25 mmHg). The percentage of patients reclassified from severe to non-severe AS using pressure recovery adjusted AVAI was 15% and when using the PSG was 43.5%. A significantly higher proportion of patients were re-classified if BSA >=2 (61%; P < 0.02) and if AVA/AoA ratio was > 0.1 (70%; P = 0.007).
Table 2 – Differential classification of aortic stenosis in our patient population set based on body surface area (BSA) and the ratio of aortic valve area (AVA) to the aortic root area (AoA). 61% of patients with a BSA >=2 (n= 20) were reclassified from severe to non-severe AS when pressure recovery was taken into account, while only 30% of them were reclassified if BSA < 2 (n= 23). In addition, by using echocardiographic data to obtain the AoA and the AVA, we found that 70% of patients with an AVA/AoA > 0.1 were reclassified when pressure recovery was taken into account by peak systolic gradient (PSG) criteria (PSG > 64 mmHg), while only 26% if AVA/AoA < 0.1. By identifying these patients with high BSA values and AVA/AoA ratios, we can predict those patients who will benefit most from pressure recovery adjustments.
Conclusions
Depending on criteria used (AVAI or PSG), accounting for pressure recovery is an important determinant to accurately classify AS.
PR is a function of the ratio of Valve Area to Aortic Area (AVA/AoA) with a theoretical maximum of PR at a ratio of 0.5.
We suggest to routinely account and adjust for pressure recovery in the echo lab. It is easy to perform and appears especially useful in patients with AVA/AoA ratio > 0.1 and/or BSA >= 2.
Methods
Retrospective database interrogation between 2007 and 2012 detected 82 consecutive patients diagnosed with severe native valve AS using current criteria (PSG  64 mmHg, peak transaortic velocity  4 m/s, or AVAI  0.6 cm/m2). Of this, 30 patients were excluded due to left ventricular dysfunction (LVEF  50%), atrial fibrillation, or other severe valvular lesions, and another 6 due to suboptimal image quality, leaving 46 patients for analysis. The aortic root diameter was measured at the level of the sinus of Valsalva and incorporated into a previously published formula. Statistical analysis was performed using Fisher’s exact test.
Table 1 – Demographics of the 46 Patients analyzed in this study.
References
Fig. 1 – Influence of aortic valve area (AVA) to aortic root area (AoA) on absolute pressure recovery. Although pressure recovery is influenced by peak transvalvular velocities, the AVA/AoA ratio appears to be the most important determinant to predict clinically significant pressure recovery gradients. According to the equation described, PR is maximal at an AVA/AoA ratio of 0.5 for any given peak velocity.
Barker PCA, Ensing G, Ludomirsky A. Comparison of simultaneous invasive and noninvasive measurements of pressure gradients in congenital aortic valve stenosis. JASE 2002;15: 1496–1502
Bahlmann E, Cramariuc D, Gerdts E, et al. Impact of Pressure Recovery on Echocardiographic Assessment of Asymptomatic Aortic Stenosis: A SEAS Substudy. JCMG 2010;3(6):555–562
Baumgartner H, Stefanelli T, Niederberger J, et al. “Overestimation” of catheter gradients by Doppler ultrasound in patients with aortic stenosis: a predictable manifestation of pressure recovery. J Am Coll Cardiol 1999; 33:1655– 61.
Contact details
Dr. Sameer Tatavarty MBBS
A/Prof Stefan Buchholz MBBS, MD, MRCP(UK), FRACP
Department of Cardiology, Mackay Base Hospital
Mackay, QLD 4740, Australia