Dr. Gammie and group at the University of Maryland have a good paper summarizing the current state of the art.

Dr.  Kerut and his colleagues in Louisiana have a good paper analyzing flow post implantation using TTE and TEE.

Dr. Speziali and group from Pittsburgh have a good paper showing the current “On Pump” technique in detail

and..

Dr.   Nishimura and his group from Japan have a great picture of an implanted graft.

Even though these papers, and many others from around the world, report on the success of the basic procedure, we at Cardious think the current clinical use is only the “tip of the iceberg”.  What is needed is a specifically engineered implant device and insertion tool to allow a surgeon to repeatedly and confidently perform the procedure, using a valve of choice, on a beating heart.

Our goal is to deliver exactly that.

In an earlier post, I mentioned that a few years back my design consulting firm was involved in the development of a transcatheter valve device.  Like my cartoon friend to the left, when I started the project I  asked my client what were the design guidelines.  Basically, the answer I received, which I think would apply to most all the transcatheter start-ups firms back then, can be summarized as follows:

• Eliminate the use of the heart lung machine
• Perform the procedure thru a small hole.

Given these two parameters, I would agree that a transcatheter valve is a logical design output.

But it wasn’t long into the development program that I soon realized that to be truly successful against the gold standard put forth by traditional valve replacement surgery, these two design parameters were critical, but alone not sufficient for long term success.  I now realize four more guidelines should have been given to me  to meet real market expectations.

• The valve must be as good as current valves on the market
• The procedure should be applicable to a broad range of patients, doctors, and hospitals.
• In this risk adverse marketplace, the new product should present a reasonable risk/reward ratio to investors
• And, the new valve should meet a rule I know all doctors follow – do no harm.

Of course, I believe our AvA device meets this full palate of design guidelines and transcatheter designs fall a bit short.  I hypothesize that transcatheter valve designers were not directly asked to meet all of these additional design requirements so, if they didn’t meet them, that would neither be surprising nor a criticism of their design skills.

Let me quickly go through and review  these design guidelines in more detail.  You can then be the judge as to their validity and importance in the marketplace.  Email me your opinion.

Eliminate use of the heart lung machine

A major drawback of a conventional aortic valve replacement procedure is that the patient must be placed on a heart-lung bypass machine wherein the heart and lungs are stopped.  The risks and complications associated with this highly invasive procedure are well known. These include:

• Increased risk of blood clots / debilitating stroke
• Organ failures post surgery
• Excessive bleeding
• Inability to restart the heart / death

The AvA procedure (and a transcatheter procedure) is performed on a beating heart, thereby eliminating all of the above risks.

Perform the procedure thru a small hole

The AvA procedure does not require a large sternal chest incision like that required to install a traditional heart valve. Similar to an apically place transcatheter valve, our procedure can be performed through a small incision made between the ribs.   Performing the AvA procedure provides the following benefits compared to traditional surgery.

• Shorter hospital stay
• Less pain and scarring
• Less risk of infection
• Less blood loss and fewer transfusions
• Faster recovery
• Quicker return to normal activities

I think we can all agree, when compared to traditional valve surgery, both the AvA Valve Bypass Graft and transcatheter designs currently in development meet these two fundamental guidelines.   Now let’s move on to the remaining four guidelines that I think are equally important to clinical success leading ultimately to business success in the marketplace.

The valve must be as good as current valves on the market

At the operating table, our AvA device is combined with a conventional, FDA approved heart valve selected by the surgeon.  The valve selected  will no doubt already have a long history of excellent performance and be expected to last a minimum of 15 years.

Transcatheter valve products must rely on radically new designs that are unproven in long term clinical trials.  In practice, these designs will need 5+ years of human implant data before even preliminary valve durability and performance can be clinically assessed.   Risk of failure is not insignificant – an implanted heart valve needs to open and close 40,000,000 cycles per year (over 100,000 times per day!).  A valve failure can mean sudden death.

Be applicable to a broad range of patients, doctors, and hospitals

Except for patients presenting with moderate to severe aortic insufficiency, the Cardious device is agnostic to the annulus size, calcific structure, or leaflet configuration of the native aortic valve.

Transcatheter valves, on the other hand, are restricted to implantation into only tricuspid shaped valves.  Patients with bicuspid valves are excluded from the Edward’s FDA human trial and are also excluded in guidelines jointly established by the European Association of Cardio-Thoracic Surgery and the European Society of Cardiology.  The reason is that the elliptically shaped opening of a stenotic bicuspid valve is not conducive to maintaining the necessary blood tight seal around the cylindrically shaped transcatheter valve.   This anatomical restriction is not insignificant with regard to market opportunity.  Published studies suggest up to 40 % of patients over the age of 70 that have valve replacement surgery have a bicuspid shaped aortic valve.

Also, guide catheter access to the coronary ostia will most likely be blocked by the implanted transcatheter valve, thereby preventing future coronary stent interventions.  This is important since a majority of patients presenting with a calcific tricuspid shaped aortic valve also have coronary artery disease.   This “coronary jail” side effect seems likely to be a serious inhibitor of broad clinical use, especially in younger patients (less than 80), but as yet I have not seen it discussed in the literature with one exception.  Upon careful reading of the Edwards PARTNER trial protocol, patients with significant untreated coronary artery disease are excluded from participating in the study.  Is that why – because future coronary intervention may not be possible?

Unlike transcatheter valve products, extensive training, additional personnel, and a hybrid surgical suite are not required to use our device.  The AvA procedure can be easily adopting by all cardiac surgeons working in standard operating rooms anywhere in the world.

In this risk adverse marketplace, develop a product with a a reasonable risk/reward ratio to investors

Our device does not require the large capital investment required to development of a new class of heart valve.  We do not need to design, test, redesign, retest, redesign … our valve stent or tissue selection until we meet the significant performance requirements promulgated by both European and perhaps, as evidenced by Corevale’s no show in the US,  more onerous  FDA regulators.  Our device is a hybrid textile graft with no moving parts.  Although we will need to demonstrate implant quality design and compatibility within a blood flow environment, the risk and related time and money to market is substantially less than that of our transcatheter brethren.

Also, once design and regulatory hurdles are met, customer clinical adoption of our device could be rapid based on surgeon confidence in the procedure (based on prior experience) and limited competition from transcatheter devices in the large cohort of patients presenting with a bicuspid valve or severe CAD.  Also, since our product does not obsolete current valves on the market, we believe current valve companies will be supportive of our device.   These factors should all contribute to reduced investment risk.

Do no harm.

An AVBG procedure is fundamentally a safe procedure.  Throughout the procedure, the surgeon has line of sight control.  If an inevitable “situation” occurs, the surgeon has multiple bail out options not afforded cardiologists performing a percutaneous transcatheter procedure.  Also, because the AVBG graft is connected to the descending aorta, most blood flow will be away from the brain.  Based on prior published papers, embolic stroke events attributed to either the procedure or the implanted valve are not likely.  On the other hand, transcatheter procedures have the following inherent concerns already demonstrated in initial human trials:

• Aortic root disturbance due to valvuloplasty and stent implanatation can lead  to emboli generation leading to stroke.
• Significant infection and/or vessel damage can occur at the catheter insertion site.
• Permanent pacemaker implantation has been necessary in a significant numer of patients.  (This seems more prevelent in nitinol designs compared to stainless)

Of course, you all realize that my critique of the design requirements might be biased.  What do you think?  Which approach – transcatheter or valve bypass – do you think best meets the design requirments, and why?