Continuing last week’s discussion of new devices for treating heart diseases, a major innovation are the recent reports of success in replacing or repairing diseased or damaged aortic or mitral valves via catheter-based techniques instead of open surgery.
Continuing last week’s discussion of new devices for treating heart diseases, a major innovation are the recent reports of success in replacing or repairing diseased or damaged aortic or mitral valves via catheter-based techniques instead of open surgery.
Mitral regurgitation is when the valve becomes unable to close tightly. Once the regurgitation becomes sufficiently severe to cause heart failure, the death rate reaches about 5% per year. Most such individuals are referred for cardiac surgery to either try to repair the valve, replace the valve or do a procedure that in effect lessens the amount of regurgitation without actually replacing the valve. The latter procedure, although not curative, can be quite successful and alleviate the heart failure and the symptoms thereby leading to a longer and better quality life.
A new procedure that does not use open surgery to repair the mitral valve leak was recently reported in the New England Journal of Medicine. The process is to pass a catheter via the groin to the heart and position it at the opening of the mitral valve. This mechanical device, manufactured by Abbott Vascular, is able to grasp the two sides of the mitral valve and clip the two leaflets together. It does not create a tight seal but in most cases can markedly reduce the amount of regurgitant flow back into the atrium.
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279 patients with grade 3+ or 4+ (i.e., serious) mitral valve dysfunction were randomized 2:1 to have a percutaneous repair done with the new device or the customary open repair or replacement (the specific procedure at the surgeon’s discretion based on the valve status). 21 patients withdrew consent before the procedure was done, leaving 258 treated patients.
By the 12 month end of study time, the composite of freedom from death, from surgery or from grade 3+ or 4+ valve dysfunction for all randomized patients were 55% (catheter-based) vs. 73% (open surgery). Of those treated per the protocol (i.e., did not exclude themselves, etc) then the rates were 72% vs. 88%. The rates of major adverse events (most often the need for transfusion) as of 30 days were 15% vs. 48%. Quality of life improved in both groups of patients over the 12 months although there was a decrease at 30 days for the open surgery patients.
What these results suggest is that open surgery is more likely to greatly relieve the mitral regurgitation than will the percutaneous catheter procedure. However, the percutaneous procedure is safer, requires less time in the hospital, and is associated with improved quality of life and improved ventricular function from baseline. Many patients might therefore decide to choose the percutaneous catheter-based procedure on the grounds that it greatly relieves the problem in almost three quarters of the patients, is less invasive and is safer than surgery. Then if that individual patient was not among the success stories, he or she can choose to have the follow-up open surgery.
Further, although not mentioned in this article, there are patients who simply cannot tolerate open surgery for any number of reasons who might still be able to undergo the catheter-based procedure. This might then create an option for repair not otherwise available today with open surgery. Not discussed in the article was cost. This might become a deciding factor as well.
Aortic stenosis is not uncommon in older individuals and they are rapidly increasing in numbers. Once the first symptoms develop, about 50% of patients with aortic stenosis will die within 2 years. Surgical replacement of the aortic valve will improve both heart function and survival. Unfortunately, about 30% of symptomatic individuals cannot undergo surgery because of older age, other heart problems or other medical conditions that render surgery too risky.
The new approach is called transcatheter aortic value implantation (TAVI.) In this procedure, a catheter is inserted into the femoral artery in the groin and run up to the heart. From the catheter, the patient’s valve is opened wide with an inflatable balloon. Then a bioprosthetic valve (Edwards Lifesciences) made from bovine pericardium affixed to a stainless steel support frame is deployed into place via another balloon catheter and secured to the patient’s own aortic valve base.
A randomized study of 358 patients with aortic stenosis not considered surgical candidates comparing TAVI to standard therapy was reported in the New England Journal of Medicine on October 21, 2010. The results were clearly favorable. Standard medical therapy was noted to not alter the natural history of aortic stenosis with 51% dead in one year. TAVI was superior with improved cardiac symptoms and good hemodynamic performance of the new valve which persisted for at least the first year of follow-up and with 31% dying during that year, a substantial decline in mortality.
But – and it is a significant “but” – TAVI was associated with a 5% risk of serious stroke (compared to 1% in the control group.) Further, MRI studies of patients suggest that many had new perfusion defects of the brain after TAVI suggesting that emboli from the new valve may be rather common.
But all things considered the improvement in symptoms and the reduced deaths argue that TAVI is now the appropriate therapeutic approach for those with aortic stenosis who cannot otherwise undergo surgery. Hopefully, coming improvements in the device will lead to fewer complications.
About six months later, the same investigators reported on 699 high risk but nevertheless surgical candidate patients who where randomized to either TAVI or open valve replacement. At one year about 25% of patients in both groups had died suggesting that the TAVI approach was not inferior to open replacement. The rates of major stroke at one year were 5.1% (TAVI) and 2.4% (open surgery). Adverse events were about twice as common in the surgical patients as was new onset atrial fibrillation (8.6% vs. 18%).
These two new approaches to valve repair or replacement without open surgery creates a new venue for cardiac care – one that will undoubtedly develop and improve in the years to come. It is a testament to innovators skills and determination.
Stephen C Schimpff, MD is an internist, professor of medicine and public policy, former CEO of the University of Maryland Medical Center and consults for the US Army, medical startups and Fortune 500 companies. He is the author of The Future of Medicine – Megatrends in Healthcare and his new book, the Future of Health Care Delivery, out Feb, 2012. Updates are available at http://medicalmegatrends.blogspot.com
