Table Of ContentJack Bokros
Hear t
of Carbon
The Story Behind
the Pursuit of the Perfect
Mechanical Heart Valve
Heart of Carbon
Jack Bokros
Heart of Carbon
The Story Behind the Pursuit of the Perfect
Mechanical Heart Valve
Jack Bokros
Georgetown, TX, USA
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v
Heart of Carbon is dedicated to Roberta
Bokros, my ever-loving and cherished
partner for more than six decades, mother of
our three daughters and supporter of our five
grandchildren and seven great
grandchildren.
Disclaimer
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Artivion, Inc. or its affiliates does not
constitute or imply agreement with or
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which are the author’s own.
Foreword by John D. Puskas, MD
I was first introduced to the On-X mechanical valve by my colleague, Dr. Omar
Lattouf, shortly after it was approved for use in the aortic position by the FDA in
2001. Omar had previously used it while operating in his native Jordan and explained
to me its obvious design advantages. I immediately tried it, was impressed by the
very low gradients obtained, and adopted it as my routine choice for mechanical
aortic valve replacement. Since FDA approval of the On-X mitral valve in 2002, I
have never implanted a mechanical valve that was not an On-X valve.
John Ely, VP for Regulatory Affairs at Medical Carbon Research Institute (man-
ufacturers of the On-X valve), invited me to have breakfast with him during a
national cardiothoracic surgical meeting in 2005. At that breakfast, he explained the
data from Europe and South Africa that made him believe that the On-X valve might
be safely used with lower levels of warfarin anticoagulation than were mandated by
contemporary guidelines. When asked whether I would consider leading such a
trial, I agreed. At that breakfast, literally on a napkin, the design of the PROACT
trial was first drafted. I asked that two important features be included in the trial
design: first, that all patients should receive standard warfarin anticoagulation plus
low-dose aspirin for three postoperative months to allow endothelialization of the
sewing cuff prior to randomization; and second, that we include a group of low-risk
AVR patients who would then be randomized to receive dual antiplatelet therapy
alone, without warfarin. As is well known, the PROACT trial resulted in FDA
approval of an Indication For Use (IFU) for a lower INR target range (INR 1.5–2.0
plus low-dose aspirin) than the traditional INR target of 2.0–3.0 plus low-dose aspi-
rin for patients implanted with an On-X AVR, after 3 postoperative months of tradi-
tional anticoagulation. While the dual antiplatelet therapy arm failed to demonstrate
non-inferiority, results of reduced INR in patients with the On-X mechanical aortic
valve showed a striking reduction in bleeding events without an increase in
xi
xii Foreword by John D. Puskas, MD
thromboembolic events and led to the first and only FDA IFU approval for lower
INR for a mechanical heart valve prosthesis. Importantly, at the time of this writing,
analysis of the results of lower INR (INR 2.0–2.5) for patients with an On-X valve
in the mitral position is underway and preliminary results seem favorable for an
upcoming FDA submission.
The historic ruling by FDA to allow a lower INR with (only) the On-X mechani-
cal heart valve is an affirmation of the natural laminar blood flow through the On-X
valve due to its flared orifice design as well as the thromboresistant polished sur-
faces of its pure carbon. There are other design features that bear mention, namely
the supra-annular sewing cuff, the cylindrical housing in which the valve leaflets
close with remarkably small regurgitant volumes and low leaflet impact velocities,
and the actuated pivots with large purge volumes that eliminate blood stasis, reduc-
ing the overall thrombogenicity of the valve prosthesis. All of these design features
are the work of Jack Bokros, PhD, a remarkable materials scientist and engineer
who also played a key role in the design of the St. Jude mechanical heart valve pros-
thesis decades earlier.
In this book, Dr. Bokros provides a personal account of his own pioneering work
as his career evolved over four decades from engineering nuclear reactors and car-
bon materials in the aftermath of the Manhattan Project to his invention of the On-X
mechanical heart valve. This saga included multiple twists and turns worthy of a
television drama series, replete with corporate espionage, international intrigue dur-
ing the Cold War, wrongdoing and litigation, groundbreaking scientific achieve-
ment, and relentless determination to finally create a pure carbon heart valve through
which blood flow is near-normal. This chronicle reminds one of the statement by
Thomas Edison that genius is 1% inspiration and 99% perspiration. It is also another
example in which progress in one field (engineered carbon for nuclear reactors) led
to a breakthrough in an unrelated field (surgical treatment of valvular heart disease).
Taken together, these dual lessons should teach aspiring cardiovascular innovators
to leverage advances in allied fields and to be prepared for a long, arduous pathway
to success.
Several of the early giants of cardiac surgery served important supporting roles
for the inventor-protagonist. But such a story could only be told by the architect of
the adventure himself. In this very personal book, Dr. Bokros demonstrates that he
is not just a pioneering scientist but also a captivating storyteller.
