- The New Machinery of Medicine: How Gene Sequencing and High-Performance Computing Are Revolutionizing Care
- Minimizing blood vessel blockage
All cardiac procedures carry a risk of stroke because plaque or calcium buildup can break off in small pieces, float up into the brain, and block narrow blood vessels. A highly specialized tool called an embolic protection device is currently used to prevent some of the released debris from reaching the brain.
When Alexandra Lansky, MD, professor of medicine, finished her first fellowship in 1996, patients who needed swift intervention to clear plaque that threatened to block blood vessels supplying their hearts had limited options. Doctors used a catheter with an inflatable balloon to squeeze the plaque buildup against the vessel wall. Later came metallic stents that could be inserted over the plaque to widen the vessel. Open-heart surgery was the only option for correcting valve-related problems. “Interventional cardiology was in its infancy,” Lansky said. The British-born, French-raised cardiologist felt drawn to the field by the opportunity to refine devices that could save lives and even permanently address heart disease.
Since she arrived at Yale eight years ago, Lansky has built a vast infrastructure of clinical studies—with countless moving parts, such as active patient recruitment, compliance, and research approval—within the section of cardiovascular medicine at Yale School of Medicine. Nearly 100 clinical trials are ongoing under her leadership as director of the Yale Heart and Vascular Clinical Research Program. She also directs the Yale Cardiovascular Research Group, which designs, plans, and executes multicenter studies that test medical devices in clinical trials.
Within these roles, Lansky started one of the earliest clinical research programs to offer transcatheter aortic valve implantation (TAVI also known as transcatheter aortic valve replacement, or TAVR). Performed in patients with a narrowed aortic valve, this procedure allows cardiologists to thread a catheter through a blood vessel in the leg up to the heart to implant a new aortic valve—thus avoiding open-heart surgery.
While cardiac interventional technologies have drastically improved over the past two decades, a stubborn risk remains: strokes. During any cardiac procedures, plaque or calcium buildup can break off in small pieces, float up into the brain, and block a narrow blood vessel there, causing a stroke. A highly specialized tool called an embolic protection device is currently used during TAVI to prevent some of the released debris from reaching the brain. However, the devices are not foolproof. After years of experience, Lansky decided she could do better.
During TAVI, when the new valve replaces the old valve, some debris can come loose. Stroke rates hover around 3% in patients who have this procedure. Stroke risk is lower with TAVI than with surgery. However, our studies with brain imaging show that virtually all patients have some degree of neurologic injury—they just may not show any symptoms. None of the current deflection technologies fully seals off the cerebral vessels. The device our team invented addresses this weak spot.
It completely seals off blood flow to the brain using a mesh netting with pore sizes of less than 120 microns. We are in the early phases of development and hope to be able to bring this to our patients soon.
Our Yale research program has established a partnership with the Barts Heart Centre and Queen Mary University of London focused on cardiovascular-device innovation and evaluation. Minimally invasive and device-based approaches to ischemic and structural heart disease have taken center stage in our field. Procedures like TAVI are proving to be safe and effective, as well as reducing hospital-stay times. This has added up to lower health care costs, better outcomes, and happier patients. This has been a major initiative of the United Kingdom’s National Health Service and is increasingly important in the United States as we try to contain health care costs. We’ve found that TAVI patients in the hospital stay two to three days compared to five to seven days following open-heart surgery. In general, TAVI patients do not need to go to a skilled nursing facility for recuperation. They just go home. It has completely changed the equation in terms of recovery and health care costs.
TAVI has been a revolution for our patients, who generally want to avoid a visit to the surgical operating room if at all possible. After 15 years of rigorous clinical testing of patients with aortic stenosis, it has completely changed how these patients are being treated. At this year’s American College of Cardiology (ACC) annual meeting, we heard Eugene Braunwald, MD, considered to be the father of modern cardiology, comment on the latest results of the use of TAVI in younger and low-risk patients with aortic stenosis. He said, “This is a historic moment. We will be telling our children and grandchildren about these remarkable results.”
We are finding better ways to identify which patients need interventional treatment and how to evaluate them in less invasive ways. For coronary artery disease, the angiogram has been the gold standard. A wire-based assessment of the coronary blockage currently allows us to measure the pressure drop from before and after the blockage. If the pressure drop is below 80% of normal flow, then treatment with a stent is justified. This approach, though beneficial, is invasive and requires threading a wire through the blood vessel. Right now we are testing and validating a method that relies on the images produced by an angiogram to determine pressure changes. Using computational modeling based on the X-ray images, we can reliably simulate the pressure drop without having to rely on a wire or create potential complications and patient discomfort. This is expanding the diagnostic value of the angiogram and allows us to more broadly find out which patients should be treated. We are also working on integrating artificial intelligence into diagnostics and on better patient selection for treatment. I predict we will have much more to report on this area in the near future.