The Challenge of Treatment of Patients with Aortic Stenosis in the NHS

This paper from the United States is extraordinary because it deals with mortality on waiting lights in patients with aortic stenosis.

Is this a Wonder Prosthesis?

Reduced anticoagulation after mechanical aortic valve replacement: Interim results from the Prospective Randomized On-X Valve Anticoagulation Clinical Trial randomized Food and Drug Administration investigational device exemption trial

Cardiac surgeons, industry and increasingly patients with heart valve disease, are always on the lookout for the perfect  heart valve prosthesis.
There are 2 main types of prostheses that are used to replace diseased valves, mechanical and biological.

Porcelain, Risk Aversion and Inappropriate Treatment

Cardiac surgery in patients with a porcelain aorta in the era of transcatheter valve implantation
A healthy ascending aorta is necessary for the safe completion of a heart operation.

The Perfect Human Valve Substitute ?

The quest for the perfect heart valve substitute goes on. This article in recent edition of the Circulation journal shows how little has changed in the 50 years we have been implanting prostheses to replace diseased human aortic valves. Patients who have mechanical heart valves still require anticoagulants and are at greater risk of strokes or anticoagulant related haemorrhages. The new anticoagulants have not and will not change that reality. Patients who receive biological valves are at higher risk of requiring reoperations due to degeneration of the prosthesis. The cut off age for the use of mechanical prosthesis used to be 70 years. (Below 70 mechanical, above biological). Over the past decade, it has drifted downwards first to 65 then to 60. Although the rate of bioprosthetic degeneration does slow with age (possibly related to calcium turnover) the main determinant of whether degenerative changes become clinically significant is years of life with the prosthesis in situ I.e. longevity or prognosis. As life span of both women and men has increased rapidly over the past 20 years, the cut off age should in my opinion, be going up and not down. This downward drift in cut off age has not occurred because of new evidence or because of dramatic new developments in the design or manufacture of biological valve prosthesis. What has driven this change is marketing and the advent of TAVI (Transcutaneous Aortic Valve Implantation) or valve on a catheter. This device ( which is essentially a biological prosthesis that is collapsed around a catheter ) can be used to treat a stenosed native aortic valve or a degenerating surgically implanted prosthesis without the need for open surgery. A TAVI device inside a degenerating biological prosthesis is a very imperfect solution for many people who might still have 10 or more years of like ahead of them. What is needed and what has not yet been invented is a biological valve that does not degenerate over time or a mechanical valve that is completely non-thrombogenic. The advent of stem cell technology and the emerging concept of using acellular valves that get seeded by autologous cells suggest that the former I.e. a perfect biological valve is more likely to be invented than the latter. I won't however be holding my breath.

 

Posted with Blogsy

A Cardiothoracic Holy Grail and the future of Medicine.

This article on genetic polymorphisms in patients with thoracic aortic aneurysms interests me for a couple of   

reasons.

Technology Dispersal and which Patients should receive treatment.

The traditional way of replacing a diseased aortic valve is through a stenotomy incision and open heart surgery. When patients are turned down for surgery, they have, until recently, been treated conservatively. Prognosis for this group of patients is very poor with most of them dying within 2 years of presenting. Over the past 2 years, a new therapeutic option has become avaialble  - TAVI or transcutaneous aortic valve implantation. A randomised controlled study (the Partner study) has confirmed survival advantage of this device when implanted into patients with aortic valve stenosis who have been turned down for surgery when compared to those treated conservatively. Both NICE and the FDA have approved the use of this device for patients turned for surgery. This article published recently in JAMA outlines how dispersal of the technology is being achieved in North America - with the cooperation of regulatory authorities and cardiology and cardiothoracic professional bodies. NICE consults professional bodies but its provisional guidance regarding suitability of use in patients who have been turned for surgery does not translate into actual dispersal of the technology. Decisions as to who receives the treatment are left to unaccountable commissioners. Patients in many areas of England and in the whole of Scotland do not have access to this form of treatment and are dying prematurely. Although FDA approval in the USA came late, it is likely now that the technology will be disseminated in an orderly logical fashion.  Not sure of when TAVI became TAVR - as the native valve is left insitu, it's not quite a replacement.

Real World Data for Biological Valve Patients

Reoperation of Left Heart Valve Bioprostheses According to Age at Implantation
This retrospective study, published recently in Circulation of a large number of patients undergoing aortic or mitral valve replacement with biological valves is interesting. I do not agree with their opening gambit that evidence for implantation of biological valves in younger patients is growing - -it isn't. It does however provides real world data on the chances of reoperation after implantation of a biological valve in the aortic or mitral positions. What I also found interesting is the fact that having concomitant coronary artery grafts seemed to 'protect' against the need for reoperation. There are 3 possible reasons for this - 2 nihilistic and the third hopeful. Patients are not surviving long enough for reoperation to take place. We know having coronary disease is associated with shortened survival when compared to a valve surgery patient without coronary disease. Surgeons are just not operating on patients with a deteriorating valve in the presence of patient coronary grafts - such procedures are technically hazardous. Statins, that all patients with coronary disease take, protects the biological valve against late deterioration. Many people do believe this and there may be mechanistic reasons why it may be so. There is however no strong evidence for this, so far.

THE PROSTHETIC VALVE PENDULUM THAT IGNORES THE EVIDENCE

There are 2 types of prostheses that are used to replace diseased heart valves - mechanical and biological. Randomised studies have shown 2 differences between the 2 - biological prostheses are more likely to degenerate over time, especially if the age of the patient at implantation is under 65-70,   & patients receiving mechanical valves and who are therefore anticoagulated, are more likely to suffer an anticoagulant related haemorrhage. That's it.

STUDY SHOWS THAT OLD FRAIL PEOPLE DIE SOONER !!

Publication of this paper is good in one sense  - it is I hope the first of many studies examining and highlighting  the effect of frailty on outcomes after cardiac surgery.

PERMANENT PACEMAKERS AFTER AORTIC VALVE SURGERY

Although the findings from this paper are hardly new, their publication is timely. The need for a permanent pacemaker after catheter implantation (TAVI) of one of the aortic valve models on the market (Core Valve) is more than 30% in some series. The need for PPM implantation is associated with increased costs and is therefore not negligible especially when common. 

BIOLOGICAL OR MECHANICAL , WHO KNOWS ?

Aortic Valve Replacement: A Prospective Randomized Evaluation of Mechanical Versus Biological Valves in Patients Ages 55 to 70 Years -- Stassano et al. 54 (20): 1862 -- Journal of the American College of Cardiology

A surgical randomized controlled study is always welcome and worth commenting on - they are difficult to organise and expensive and consequently they are rare.

THE DOWNSIDE OF OUTCOME REPORTING

I have posted this paper because it is written by authors who I know and who I hold in high esteem and it highlights an issue that I have written about previously. I also have very personal experiences with this particular example - i.e young adults with aortic valve disease being denied the Ross operation . Every cardiac surgeon knows that public reporting of outcomes has this very serious downside to it. Patients will get offered a treatment that may offer better early outcomes for them and the surgeon whose performance is being reported, even if late outcomes are not as good as they could be with alternative treatments. They are being offered treatments that suit the surgeon and are not in the patients best long term interests - as Des Spence would say in the BMJ - Bad Medicine indeed!