Author + information
- Michael F. O’Rourke, MD, DSc∗ ( and )
- Wilmer W. Nichols, MS, PhD
- ↵∗St. Vincent’s Hospital and Clinic, University of New South Wales, Suite 810, St. Vincent’s Clinic, 438 Victoria Street, Darlinghurst, Sydney, New South Wales 2010, Australia
On the basis of hemodynamic studies before and after transcatheter aortic valve replacement (TAVR), Yotti et al. (1) report that the aorta in calcific aortic stenosis is abnormally stiffened, with such stiffening inapparent before valve replacement but exposed after TAVR. The authors base their conclusions on comprehensive measures of aortic elasticity, compliance (using a Windkessel model), wave intensity analysis (with or without Windkessel model), and aortic input impedance utilizing a transmission line model.
This study is very important because it bears on the difficulty in managing such patients during and after TAVR, despite successful ability to normalize the gradient across the aortic valve.
There is, however, another issue, and a precedent (2,3) (Figure 1) where a high velocity jet in an artery causes relative reduction in lateral pressure, resulting in the interpretation (with flow volume similar during ejection), that any change in systolic and pulse pressure must be due to altered compliance/distensibility of the artery beyond the source of the jet. In the precedent case (2), low pulse pressure in the distal pulmonary artery beyond an encircling flow meter cuff was reported to reduce compliance of the pulmonary circulation, but can be explained as a Venturi effect, when flow velocity approached or exceeded 90 cm/s (4,5). In the present case (1) flow velocity in the aorta beyond the stenotic valve approached or exceeded 200 cm/s and focus was on distensibility alone, with this considered to be normal before and abnormally high after TAVR. It is not surprising that multiple indices of distensibility were low pre-TAVR, because all were calculated from the same aortic pressure waveform, which had been reduced and distorted when pressure was measured side-on to the direction of flow, by a Venturi effect at peak flow velocity.
The authors appear not to have considered this issue (which was illustrated in the previous paper ) (Figure 1); it does explain different features of waveforms, including the slow rising (<400 mm Hg/s) anacrotic pressure pulse, the grossly abnormal values of peripheral resistance, and central impedance prior to TAVR (the authors’ Figure 1 and Central Illustration).
Please note: Dr. O’Rourke is a founding director of AtCor Medical P/L, manufacturer of pulse wave analysis system, SphygmoCor, and of Aortic Wrap P/L, developer of methods to reduce aortic stiffness. Dr. Nichols has reported that he has no relationships relevant to the contents of this paper to disclose.
- American College of Cardiology Foundation
- Yotti R.,
- Bermejo J.,
- Gutierrez-Ibanes E.,
- et al.
- Hopkins R.A.,
- Hammon J.W.,
- McHale P.A.,
- Smith P.K.,
- Anderson R.W.
- O’Rourke M.F.
- O’Rourke M.F.
- Nichols W.W.,
- O’Rourke M.F.,
- Vlachopoulos C.