When does 2% equal 55%?

In my last post, I said that 40% of patients over age 70 presenting for stenotic

Bicuspids Do Not Qualify

Bicuspids Do Not Qualify

AVR (Aortic Valve Replacement) have a bicuspid shaped valve and that a bicuspid shaped aortic valve is a major contraindication to transcatheter valve implantation (reference PARTNER Trial and European Guidelines).  Rationale for this contraindication can be found in a paper by Dr. Zegdi.

Actually, when you take into account all age catagories, over 55 percent of current surgical patients have a bicuspid (or unicuspid) valve.  These findings are based on a detailed review of 932 consecutive AVR patients performed at Bayor University Medical Center by Dr. William Roberts, a veteran cardiac pathologist.  Dr. Roberts’ paper clearly defines the morphology of unicuspid, bicuspid, and tricuspid aortic valves and in table form presents the breakdown of valve type by age (in decades) and by sex.  Unfortunately, Dr. Roberts did not present his data in graphical form.  I took the liberty to graph his data and it is shown below.

Roberts Bicuspid Data

The literature states about 98% of the population is born with a normal tricuspid aortic valve and that unfortunately, about 2% of the population is born with either a bicuspid or a unicuspid aortic valve.  Obviously (at least to biomedical engineers) a bicuspid valve is prone to early and severe calcification due to the unnaturally high stress levels required in a two leaflet design.  That is how only 2% of the population can deliver over 50% of  the stenotic AVR surgeries and why younger stenotic patients predominantly present with a bicuspid valve.

With this data in hand, it is clear that transcatheter valves, contraindicated for bicuspid valves, will not be applicable to a large percentage of patients  If Roberts’ data published in 2005 is representative, 55% of all stenotic aortic valve patients and more specifically  40% of patients over age 70 that need a less invasive “off pump” procedure will present with a bicuspid valve and will necessarily look to AVBG as their best “off pump” solution.

If 98% of us who have a tricuspid valve  acquire a calcified stenotic valve, it will most likely be due to the typical atherosclerotic aging process similar to that seen in CAD (coronary artery disease).  My next post will talk about the correlation between stenotic aortic valves, transcatheter implants, and concomitant CAD in more detail.

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