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Posts Tagged ‘valve surgery’

Recently readers have contacted Cartagena Surgery to contribute to our many ongoing discussions on issues in cardiology, and cardiac surgery.

One of the points that readers have brought up has been the massive attention that TAVI/ TAVR has gotten from the media (and admittedly, we here at Cartagena Surgery are guilty of this), to the detriment of other issues in medicine and surgery.

In an attempt to address this very valid comment, we have started a series of posts looking at other issues in cardiac surgery – specifically in the area of valvular disease(s) and valvular replacement – and why it is important to re-focus our attention to these conditions such as infective endocarditis, mitral and tricuspid valve disorders, as well as bicuspid aortic valve disease.

Valve Disease and Dr. Didier  Lapeyre

In a current environment where TAVI/ TAVR dominate the landscape of discussion regarding valvular disease, other serious and persuasive problems in valvular disease treatments remain largely unaddressed.  The domination of conversations and considerations regarding the use of ‘less invasive’ mechanisms to correct aortic stenosis in the extreme elderly is something that could only be considered in the wealthiest of nations.

Burden of disease

Elsewhere in the world, and in the minds of more globally aware citizens, more important consideration is given to the burden of valvular disease across all populations including young adults and children.  In fact, in my limited travels, it is this scenario that encountered with much more frequency than the “frail octogenarian” that TAVI is designed for.

(For information on the burden of valvular disease in emerging countries – read The Need For A Global Perspective On Heart Valve Disease Epidemiology. )

Then why, as so many other cardiac surgeons and other authors have asked – are we expending some many resources on this minority population[1] to the exclusion and detriment of other developments in cardiac surgery?

Does TAVI detract attention from more common problems in cardiac surgery?

Some may argue, that TAVI/ TAVR is adjacent to, not exclusive to, the development of other improvements and advancements in the field but in my opinion that is a naïve view of the world.  Money and resources are not endless, and corporations and institutions expending large sums investing in transcatheter therapies are certainly not devoting similar resources to such mundane causes such as improving existing therapies.

Dr. Didier Lapeyre

But sometimes it takes a leader, and a legend to do these things, and that’s where Dr. Didier Lapeyre comes in.  As one of the original innovators of mechanical valve technology, he is not content to rest on his laurels or in the pages of medical textbooks.  As he and his colleagues note, current mechanical valve technologies continue to leave much to be desired.  As Zilla et. al. noted back in 2007, “Prosthetic heart valves: catering for the few?” this technology has been essentially stagnant for the last several years despite an enormous need, worldwide for a safe, durable mechanical valve.

Current therapies for valvular disease consist of two options; each with significant drawbacks.  The bioprosthetic or tissue valve requires no additional therapies after implantation but durability leaves much to be desired, making it inappropriate for most young candidates.

The trials and limitations of true mechanical valves are well-known.  As a foreign, metallic material, these valves are prone to cause platelet breakage, and hypercoagulability.  This leads to the dreaded thromboembolic complications of valve thrombosis and cerebral vascular accident.

If the heightened risk of post-TAVI stroke gives us pause in our frail elderly population, consider the elevated risks inherent with mechanical valves and their target population; children and young adults.

At present, the current solution of lifetime anticoagulation for patients with mechanical valves is a stopgap solution at best.  Problematic, potentially dangerous, and unpredictable are excellent descriptions of anti-coagulation with warfarin.  Unavailable and unrealistic are often as accurate; particularly when describing potential use in third-world populations.

After a recent post, talking about controversies and discussions in cardiac surgery in regards to TAVI, Dr. Lapeyre contacted Cartagena Surgery to add his thoughts on the issue.

This has opened a dialogue – and offers a new and interesting opportunity for my readers to hear about Dr. Lapeyre, his work, and (hopefully), the future of mechanical valves in addition to talking about related valvular conditions and treatments.


[1]  As we have argued several times, at Cartagena Surgery, many of the people who have been deemed ‘frail elderly ‘by their cardiologists can be successfully treated with conventional surgery.

References

Current Anti-coagulation recommendations:

Whitlock RP, Sun JC, Fremes SE, Rubens FD, Teoh KH; American College of Chest Physicians.  2012. Antithrombotic and thrombolytic therapy for valvular disease: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012 Feb;141(2 Suppl):e576S-600S.

Akhtar RP, Abid AR, Zafar H, Khan JS. (2009).  Anticoagulation in patients following prosthetic heart valve replacement.  Ann Thorac Cardiovasc Surg. 2009 Feb;15(1):10-7. Study from Pakistan, where rheumatic heart disease remains common.  Also looks at genetic and racial differences in response to anti-coagulation. Readers will also notice that this study demonstrates the wide disparities in global medicine as discussed above.  How many western patients received a ball and cage valve in 2003?

Cannegieter SC, Rosendaal FR, Briët E. (1994).  Thromboembolic and bleeding complications in patients with mechanical heart valve prostheses.   Circulation. 1994 Feb;89(2):635-41.  Review.  [Linked in text above.]  While this article is considerably dated (based on data prior to 1993) it gives an excellent overview of the many problems/ complications in mechanical valve replacement. However, the statistics cited in their work may differ considerably from more recent results. (Presumably, the rate of ‘real world’ complications are much higher than what I see cited here.)

Matsuyama K, Matsumoto M, Sugita T, Nishizawa J, Yoshida K, Tokuda Y, Matsuo T. (2002).  Anticoagulant therapy in Japanese patients with mechanical mitral valves.  Circ J. 2002 Jul;66(7):668-70. A smaller scale Japanese study.

Not available as free text: Links to abstracts, when available

Taniguchi S, Hashizume K, Ariyoshi T, Hisata Y, Tanigawa K, Miura T, Odate T, Matsukuma S, Nakaji S, Eishi K. (2012).  Twelve years of experience with the ATS mechanical heart valve prostheses.  Gen Thorac Cardiovasc Surg. 2012 Jul 6.

Van Nooten GJ, Caes F, François K, Van Bellleghem Y, Bové T, Vandenplas G, Taeymans Y.  (2012).  Twenty years’ single-center experience with mechanical heart valves: a critical review of anticoagulation policy.  J Heart Valve Dis. 2012 Jan;21(1):88-98

Brown JW, Fiore AC, Ruzmetov M, Eltayeb O, Rodefeld MD, Turrentine MW. (2012).  Evolution of mitral valve replacement in children: a 40-year experience.  Ann Thorac Surg. 2012 Feb;93(2):626-33; discussion 633. Epub 2011 Dec 7. This article talks about why we still need to improve and innovate new valve technology – high mortality in this population.

Suri V, Keepanasseril A, Aggarwal N, Chopra S, Bagga R, Sikka P, Vijayvergiya R. (2011).  Mechanical valve prosthesis and anticoagulation regimens in pregnancy: a tertiary centre experience.  Eur J Obstet Gynecol Reprod Biol. 2011 Dec;159(2):320-3. Epub 2011 Oct 1.  Another important issue that affects our decisions to use mechanical or tissue valves.

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“Aortic Stenosis as Heinz 57”

I apologize, but the best analogy I can use – is a squeeze ketchup bottle.

okay, it's not heinz.. but you get the picture..

In normal valve functioning, the three valve leaflets open and close fully to permit and control the flood of blood from the left ventricle to the aorta, where it is then circulated throughout the body.

normal valve diameter

During diastole (the filling phase) the leaflets are shut to prevent blood from leaking backwards from the aorta into the heart.  (When leaflets don’t close properly this is called aortic regurgitation.)

During systole, the ventricle contracts like a big fist,  squeezing the ketchup bottle to shoot blood out of the heart into the aorta.  (The force of this is measured in millimeters of mercury, and is the top number on your blood pressure cuff).  When the valve is working normally, it opens fully and the blood is ejected out to the aorta, and the whole cycle begins again.

In Aortic Stenosis – the valve leaflets have become fused together, either from age or disease.
(Some people are born with only two valve leaflets and this means that they are more likely to develop aortic stenosis as they age.)  As aortic stenosis progresses, the opening for blood to pass thru becomes smaller and smaller since the leaflets can not longer open fully,  In many people – at the time of surgery – this opening is about the size of the pinhole in the ketchup bottle that squirts ketchup.      (The normal sized opening is 2 to 3 centimeters).

average valve opening in severe aortic stenosis

Now, think about how hard a person has to squeeze that ketchup bottle to get some ketchup for hamburgers, fries (and all the other foods I usually scold about in other posts).
In the heart – this pressure is magnified (and can be measured in the cath lab during cardiac catheterization).

As this pressure gets higher and higher to compensate for the narrowed opening, the delicate structures of the heart become damaged, with the heart muscle becoming thicker and less flexible (just like any other muscle with exercise.)  Except unlike biceps, a big thick heart muscle is not a good thing, and can lead to heart failure, arrhythmias and sudden cardiac death.

Eventually, as the heart pushes against the increased pressure, over and over (at least sixty times per minute) the heart gets tired from working so hard.  As the heart fatigues, it is unable to keep up with demand and patients will begin to develop symptoms.

These symptoms include:

Syncope/ near syncope (fainting or near fainting) as not enough blood is pushed into central circulation and to the brain.

Chest pain – because not enough blood is pushed out to the coronary arteries during diastole.  (In a person with aortic stenosis, nitroglycerin can cause problems – as it lowers blood pressure  (and force of contraction even further in someone who needs the extra force.)

Heart failure – the weakened and thickened heart can no
longer keep up and blood begins to back up in the left ventricle.

What these symptoms predict:

Once these symptoms develop, doctors can readily estimate the approximate longevity for patients who do not subsequently have surgery.

From the natural history of aortic stenosis (from before we had surgery to treat it) we know that 50% of people with Syncope will die within 5 years.

Fifty percent of people with chest pain die within three years.

And ultimately, fifty percent of people with heart failure die within two years.

These numbers are important, and I want you to remember them for our subsequent discussions on aortic valve replacement because they need to be factored into a patient’s decision whether or not to pursue surgery.

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