University researcher unlocks underlying factors to success of popular heart failure therapy
Mechanical, electrical characteristics couple with scar tissue presence to determine patient responsiveness
Assoc. Cardiovascular Medicine Prof. Dr. Kenneth Bilchick is helping to pave the way toward higher patient response rates to cardiac resynchronization therapy — a method to improve the heart rhythm in a patient with heart failure.
Using MRI scans and tracking patients for several years, Bilchick found that the wiring used during the procedure could be optimally placed to help increase a patient’s responsiveness to CRT.
“There are roughly 5 million Americans who have heart failure,” Bilchick said. “About 500,000 are diagnosed with heart failure every year. The annual mortality rate is about 300,000 each year. CRT has the ability to take patients with heart failure and make them much better by improving symptoms, preventing arrhythmias and causing less frequent hospitalizations.”
Heart failure is a condition in which the heart pumps blood inefficiently, causing the accumulation of fluid throughout the body and symptoms such as fatigue and shortness of breath. Heart failure is associated with having a prior heart attack and can make a person more likely to be hospitalized.
Heart failure may be accompanied by poorly coordinated contractions of the heart (called dyssynchrony), in which blood is not efficiently pumped throughout the body.
For patients who undergo CRT, a small device is implanted in their hearts which stimulates the left and right ventricles of the heart to contract evenly so that the heart functions at its optimal level. But roughly half of patients receiving the treatment typically do not respond to this method of treatment. This is where Bilchick’s research team came in.
Bilchick found that to the critical pacing wire used in CRT is most effective when placed so as to avoid any scar tissue. He also found that there are certain mechanical and electrical characteristics which determine whether the tissue is a good candidate for these wires.
Bilchick’s team followed patients for several years. Using MRI scans before CRT, they determined the responsiveness of patients could be prediction based on four characteristics: the overall mechanical dysfunction of the heart, the extent and distribution of scar in the heart, areas of the heart that were abnormally stretched, and regional electrical timing of contraction in different areas the heart. He could also gauge where on the heart was best to place the critical pacing wire.
“The next step in this line of research is to use the information about why patients do or do not respond well to help them respond better,” Bilchick said. “We hope to prove in a subsequent clinical study that we can use this technology to improve response rates. Once we do that, then I think our methods could be adopted widely.”