Wednesday, December 1, 2010
Replacing the Aortic Valve Without Open Surgery!
A new approach is called transcatheter aortic value implantation (TAVI.) In this procedure, a catheter is inserted into the large 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 value made from bovine pericardium affixed to a stainless steel support frame is deployed into place via another balloon catheter and secured to patient’s own aortic valve base.
A randomized study of 358 patients with aortic stenosis not considered surgical candidates was completed comparing TAVI to standard therapy at 21 medical centers and reported in the New England Journal of Medicine on October 21, 2010. The results were clearly favorable. Standard 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 there is never a “free lunch” and TAVI was associated with a 5% risk of serious stroke (compared to 1% in the control group) and multiple vascular complications, the latter apparently related to the requirement for a large catheter placed into the femoral artery. Further MRI studies of patients suggest that many have 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 death rate (it took only 5 patients treated with TAVI to avoid one death by 1 year) 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.
The big question – will this become the approach of choice for those who otherwise are candidates for standard surgery for aortic valve replacement?
Praise for Dr Schimpff
The craft of science writing requires skills that are arguably the most underestimated and misunderstood in the media world. Dumbing down all too often gets mistaken for clarity. Showmanship frequently masks a poor presentation of scientific issues. Factoids are paraded in lieu of ideas. Answers are marketed at the expense of searching questions. By contrast, Steve Schimpff provides a fine combination of enlightenment and reading satisfaction. As a medical scientist he brings his readers encyclopedic knowledge of his subject. As a teacher and as a medical ambassador to other disciplines he's learned how to explain medical breakthroughs without unnecessary jargon. As an advisor to policymakers he's acquired the knack of cutting directly to the practical effects, showing how advances in medical science affect the big lifestyle and economic questions that concern us all. But Schimpff's greatest strength as a writer is that he's a physician through and through, caring above all for the person. His engaging conversational style, insights and fascinating treasury of cutting-edge information leave both lay readers and medical professionals turning his pages. In his hands the impact of new medical technologies and discoveries becomes an engrossing story about what lies ahead for us in the 21st century: as healthy people, as patients of all ages, as children, as parents, as taxpayers, as both consumers and providers of health services. There can be few greater stories than the adventure of what awaits our minds, bodies, budgets, lifespans and societies as new technologies change our world. Schimpff tells it with passion, vision, sweep, intelligence and an urgency that none of us can ignore.
-- N.J. Slabbert, science writer, co-author of Innovation, The Key to Prosperity: Technology & America's Role in the 21st Century Global Economy (with Aris Melissaratos, director of technology enterprise at the John Hopkins University).