The following is information from St. Judes website. The old valve is not even used in comparison with their current models.

1992 Antiquated Value: 37% blood flow, more clot-prone
1992 Market introduction. Installed in CJ Spence August, 2003.

"Also available with the HP Series cuff is a rotatable valve, the SJM® Masters Series mechanical heart valve, a design that significantly increases ease of implantation."

Note: The center bar (above) is not present in Master and Regent upgrades (below):
1. Deceased blood flow: restricts efficiency that limits endurance or increases heart rate--lifespan limited from greater heart stress.
2. Increase surface area of HP valve also increases stroke-inducing clots.
3. Possible cause of Cathy's arrhythmia, higher blood pressure and heartrate which constantly drew comments and concern.
4. Problems with documentation, the wallet card gets different answers from St. Judes.
5. Fortunately, Cathy did not receive a Silzone coated valve which was developed after her HP model (#505 verus 601, 602,  605,701, 706). This numeric recall indicates, from another perspective, the outdatedness of Cathy's valve.
6. Requires more drugs and thinner blood which causes other problems.

1996: 56% blood flow
1996 Approved for U.S. Distribution:   "In the aortic position, the pivot guards can be rotated toward subannular obstructions to push them away from the leaflets"
If this later generation valve had been used, the septal tissue could have been easily and quickly kept away from the valve leaflets. She would nor have needed a pacemaker, not suffered the hole in her heart, the Ventricular Septal Defect
2002: 100% Standard blood flow
2002 Approved for U.S. Distribution: Year before Spence Heart Surgery
Because of the efficiency of this valve in orifice to annulus ratio and ease of place, St. Jude doesn't make 17mm version, to wit, "a two-size increment" (next box text). The smallest available size is 19mm. The below graph compares the efficiency of the two recent upgrades. The efficiency of Cathy's old HP valve with a center bar is much lower.

The energy loss results show an approximate one-size increment improvement of the SJM Regent valve over the St. Jude Medical HP Series valve, which is equivalent to a two-size increment over the standard valve. (Walker et al., 1999)

1The SJM Regent valve offers up to an 84% orifice to annulus ratio--the largest in a mechanical heart valve.

The antiquated 1992 HP model implanted in CJ Spence is not even listed on St. Judes website for comparison.
It's efficiency is only 37% of the latest model which is why she is tired and facing future replacement.