Not sure about that article - first sentence: There are scarce data comparing different mechanical valves in the aortic position - gad, they've been publishing data on this stuff for decades. Then if you look at the chart (a .jpg), the 18/19 hovers around a average of 18mmHg or so and all the other sizes come in at 14mmHg or so, all with a large std. dev. so really two groups (small and a little bigger).Regarding the mean gradient values of aortic mechanical valves (MPG), there is a fairly recent and suggestive study for brands ATS, BICARBON and ON-X. The measured values for valves between 18 mm and 25 mm at 6 months after surgery were 17.04±8.4 mmHg for ATS, 21.5±12.9 mmHg for BICARBON and 17.3±7.6 mmHg for ON-X.
For example, for ON-X: small valves (18-19 mm), MPG was most in the range 18-27 mmHg, for medium valves (22-23 mm) MPG was most in the range 9-18.5 mmHg and for the larger valves (24-25 mm) MPG was most between 7.5-8.5 mmHg. So, a value considered by some to be high (for example, 18 mmHg for a 19 mm valve) is actually a satisfactory value for that valve. Also, a MPG value of 24 mmHG is found in practice in small and even medium valves, although in the literature a value of 20 mmHG is considered high. More important are the functioning and dimensions of the heart.
Early Hemodynamic Profile after Aortic Valve Replacement - A Comparison between Three Mechanical Valves - PubMedThe three bileaflet mechanical aortic prostheses (On-X, Bicarbon, and ATS) provide satisfactory early hemodynamics, which are comparable between the three valve types and among different valve sizes.pubmed.ncbi.nlm.nih.gov
As I age I get more skeptical .