As mentioned in another recent post, I'm a BAVR candidate (surgery to be had by June 2011), with moderate to severe stenosis, severe insufficiency, and no symptoms.
My default position, as I consider valves, has been to get a 3rd gen tissue valve, like the Edwards pericardial. However, my recent statistical findings about tissue vs. mechanical, my discomfort with reop, and my recent discovery of On-x has caused me to revisit this position.
I thought I would share my recent findings as I look through the literature that assesses and compares On-x. My approach has been to try to demonstrate to myself that On-X is not a good option. So far, that has been difficult. I welcome any feedback, push-back, or additional evidence that supports or not the use of On-X, particularly as it relates to my findings.
Summary of findings:
In general, On-x has been around for at least 13 years. I've read abstracts from longitudinal studies that look at some patients as far out as 10 years after surgery.
In contrast to some of the other newer valves, it seems to be free of "amateur issues", such as leaflet escape. So the literature seems to support, as far as I can tell, that this is a serious contender along with the mainstay of SJM (St Jude).
Hemodynamics seems to be on par with St. Jude.
In one short-term (12 month) study comparing OnX with SJM (20 patients in each group), there were the following results (bear in mind that 40 patients is a small study, and results from such a study should be regarded cautiously):
1) 2 OnX patients had ongoing paravalvular leakage
2) 5 SJM patients had myocardial revascularization (I don't know what this means-??)
3) Mean transvascular flow and pressure gradients were the same postoperatively but dropped more for OnX patients than for SJM patients at 12 months. However neither results was statistically signficant
4) A relatively pronounced transvalvular reflux (regurgitation across the valve?) was diagnosed for On-X valves
My analysis:
For #1) apparently sizing OnX valves is different than sizing a st. jude valve; i think the paravalvular leakage is due to a surgeon who is experienced with other valves but inexperienced with sizing an OnX valve using a similar sizing strategy when it doesn't apply. Just my conjecture here, but i think the paper suggests something similar.
For #2) I don't know what this means or if it matters - does anyone else?
For #3) The mean differences were small compared to the patient-to-patient variability, but I wonder if it's suggestive of a trend that would be seen in longer-term follow-ups. No longitudinal studies that I've seen have supported that concern however.
For #4) It is unclear whether the reflux finding applies to one On-X patient or all - I am still trying to get the full text on this paper. If it applies to all, I would wonder why (is the valve not closing properly) and whether it is suggestive of a long-term problem.
In another study of 27 On-X patients, two reported TIA (transient ischemic attacks - minor strokes that don't do long-term damage, but may be a warning sign; at the least they represent embolic events) at the 12-month follow-up. The study was otherwise positive and concluded that On-X was excellent in terms of low thrombo-embolic events. I'm not sure if 2 TIAs out of 27 patients should be categorized as "low", but on the other hand, the patients were otherwise fine and no long-term studies seem to suggest high thromboembolic results compared with other mech valves.
Conclusions: In general, it has been difficult to fault the On-X valve, as hard as I've tried. However, I will keep digging and watch carefully for evidence of increased incidence of the following relative to SJM and other mech valve options:
* paravalvular regurgitation and sizing considerations
* transvalvular regurgitation (valvular insufficiency)
* thromboembolism
Hope this is useful and welcome feedback!
Thanks
My default position, as I consider valves, has been to get a 3rd gen tissue valve, like the Edwards pericardial. However, my recent statistical findings about tissue vs. mechanical, my discomfort with reop, and my recent discovery of On-x has caused me to revisit this position.
I thought I would share my recent findings as I look through the literature that assesses and compares On-x. My approach has been to try to demonstrate to myself that On-X is not a good option. So far, that has been difficult. I welcome any feedback, push-back, or additional evidence that supports or not the use of On-X, particularly as it relates to my findings.
Summary of findings:
In general, On-x has been around for at least 13 years. I've read abstracts from longitudinal studies that look at some patients as far out as 10 years after surgery.
In contrast to some of the other newer valves, it seems to be free of "amateur issues", such as leaflet escape. So the literature seems to support, as far as I can tell, that this is a serious contender along with the mainstay of SJM (St Jude).
Hemodynamics seems to be on par with St. Jude.
In one short-term (12 month) study comparing OnX with SJM (20 patients in each group), there were the following results (bear in mind that 40 patients is a small study, and results from such a study should be regarded cautiously):
1) 2 OnX patients had ongoing paravalvular leakage
2) 5 SJM patients had myocardial revascularization (I don't know what this means-??)
3) Mean transvascular flow and pressure gradients were the same postoperatively but dropped more for OnX patients than for SJM patients at 12 months. However neither results was statistically signficant
4) A relatively pronounced transvalvular reflux (regurgitation across the valve?) was diagnosed for On-X valves
My analysis:
For #1) apparently sizing OnX valves is different than sizing a st. jude valve; i think the paravalvular leakage is due to a surgeon who is experienced with other valves but inexperienced with sizing an OnX valve using a similar sizing strategy when it doesn't apply. Just my conjecture here, but i think the paper suggests something similar.
For #2) I don't know what this means or if it matters - does anyone else?
For #3) The mean differences were small compared to the patient-to-patient variability, but I wonder if it's suggestive of a trend that would be seen in longer-term follow-ups. No longitudinal studies that I've seen have supported that concern however.
For #4) It is unclear whether the reflux finding applies to one On-X patient or all - I am still trying to get the full text on this paper. If it applies to all, I would wonder why (is the valve not closing properly) and whether it is suggestive of a long-term problem.
In another study of 27 On-X patients, two reported TIA (transient ischemic attacks - minor strokes that don't do long-term damage, but may be a warning sign; at the least they represent embolic events) at the 12-month follow-up. The study was otherwise positive and concluded that On-X was excellent in terms of low thrombo-embolic events. I'm not sure if 2 TIAs out of 27 patients should be categorized as "low", but on the other hand, the patients were otherwise fine and no long-term studies seem to suggest high thromboembolic results compared with other mech valves.
Conclusions: In general, it has been difficult to fault the On-X valve, as hard as I've tried. However, I will keep digging and watch carefully for evidence of increased incidence of the following relative to SJM and other mech valve options:
* paravalvular regurgitation and sizing considerations
* transvalvular regurgitation (valvular insufficiency)
* thromboembolism
Hope this is useful and welcome feedback!
Thanks
I definitely see the wisdom in both of your replies and really appreciate it. It is indeed hard to tell who is conducting (not to mention funding) the studies and requires and extra layer of effort.
