Important new research from the University of Virginia Health System explains why patients with heart failure do or do not respond to a very effective form of treatment, cardiac resynchronization therapy (CRT) . The research successfully identified which patients would benefit and enables doctors to create an unprecedented map of a patient’s heart to guide the installation of the CRT pacemaker-defibrillator for the best outcome.
The work could prove of tremendous importance to both physicians and the millions of people worldwide who suffer heart failure, a condition in which the heart can’t pump sufficient blood. “ We have an epidemic of heart failure in the U.S., with hundreds of thousands of deaths every year and even more new diagnoses,” explained UVA’s Kenneth C. Bilchick, MD, the primary author of a new paper outlining the findings. “If we can find ways to get higher response rates to CRT, we could find ways to help these patients, many of whom represent the most seriously ill.”
Heart failure treatment
Up to half of patients who undergo CRT may not respond to the treatment. Many of these patients may have cardiac dysfunction from a previous heart attack, a major cause of heart failure. Heart attacks leave focal areas of the heart muscle scarred, while other causes of heart failure typically produce damage that is more diffuse. Whatever the cause, the damage prevents the heart from contracting and relaxing in a smooth, well-timed fashion. “The end result is that there is blood sloshing around from one side to the other inside the heart instead of getting pumped out of the aorta efficiently to the rest of the body,” Bilchick explained.
CRT aims to correct this problem by installing a pacemaker-defibrillator with wires at key locations in the heart; however, for optimal results, the wires must be placed strategically, avoid the scar tissue and stimulate the areas that most need stimulation. As such, the UVA researchers were interested in creating an effective model to determine how the wire placement and other factors would influence outcomes after CRT. “The focus of the research is what we can do to improve implementation of CRT to increase the number of patients who respond to this otherwise very effective therapy that can dramatically improve the efficiency of the heart,” Bilchick said.
Assessing heart failure
The UVA researchers built their model to incorporate several factors, including a parameter called CURE that assesses the discoordination of the heart and is determined from advanced MRI imaging methods developed at UVA. One of these innovative imaging techniques, DENSE, was developed at UVA by a team led by Frederick Epstein, PhD. DENSE is based on traditional magnetic resonance imaging but goes beyond that by providing very accurate information regarding regional mechanical function throughout the pumping chambers of the heart. “The unique feature of our approach,” Bilchick explained, “is that we are integrating scar, mechanical information and electrical information at the pacing lead implantation site with the overall function and degree of discoordination of the heart.”
UVA’s model produces a comprehensive assessment of the heart, identifying scarred areas, sluggish areas, and areas with weak electrical impulses – effectively providing doctors with a roadmap for how best to implant the CRT pacemaker-defibrillator, including identification of the best place for the CRT pacing lead. The new study put the model to the test based on medical imaging of patients referred for CRT, and the result was that it successfully predicted outcomes, such as the extent to which heart function would or would not improve after CRT, along with providing important information about strategies to improve outcomes in future patients.
The UVA researchers next plan to test their model in candidates for CRT, using it to chart the best course of treatment.
The findings have been published online by the Journal of the American College of Cardiology and will appear in a forthcoming print edition. The paper was authored by Bilchick, Sujith Kuruvilla, Yasmin Hamirani, Raghav Ramachandran, Samantha Clarke, Katherine M. Parker, George J. Stukenborg, Pamela Mason, John D. Ferguson, J. Randall Moorman, Rohit Malhotra, J. Michael Mangrum, Andrew E. Darby, John DiMarco, Jeffrey W. Holmes, Michael Salerno, Christopher M. Kramer and Epstein.