A new pressure-sensing technology is helping doctors to read some of the innermost secrets of the heart. This cardiac monitor uses electromechanical dynamics to detect crucial pressure levels in a patient's pulmonary artery and relay those readings to physicians wirelessly, obviating the need for clunky moving parts or external power sources.
For the some 5.8 million people in the U.S. faced with chronic heart failure, trips back to the hospital can be frequent, costly and dangerous. Medications and dosages are usually prescribed based on most recent clinical checkups, and health is monitored more or less via patient symptoms and weight fluctuations, which can indicate rapid fluid buildup in the heart—a condition that often precipitates heart failure.
But the new implantable wireless device might provide better early warning, research suggests. The information helps physicians track the patients' heart health and adjust medication accordingly, reducing the number of heart-related hospital visits. Results of the recent clinical trial, published February 10 in The Lancet, show that chronic heart-failure patients who were having their ticker tracked daily had 30 percent fewer hospital readmissions over six months (39 percent over the full 15-months of the study). The research was backed by CardioMEMS, the company that makes the device.
"This study represents a major advance in the management of patients with heart failure," says Gregg Fonarow, who is associate chief of the cardiology division of the University of California, Los Angeles, and was not involved in the research. "This trial opens the door to a new era where remote monitoring of hemodynamics can be employed to enhance outcomes of patients with heart failure."
Weak hearts, weaker measures
As more people survive heart attacks, the proportion of the population living with weakened hearts has grown over the past few decades, making chronic heart failure an increasingly common condition.
Patients with heart failure often wind up in the hospital when they start to feel short of breath, which occurs as excess fluids put pressure on the arteries and lungs. At that point, assessment and treatment is often expensive and invasive—for instance, pressure readings are taken with an inserted catheter.
"We're always fixing stuff that's already broken," says Jay Yadav, a cardiologist and CEO of CardioMEMS. Treating heart failure could be cheaper and easier if a doctor could detect a patient's deterioration before serious symptoms set in, he notes.
"Traditional methods of monitoring the symptoms and signs of heart failure are not very sensitive," Fonarow says. These measures, such as daily weight fluctuation or shortness of breath, are often noted too late to avoid a hospital stay or an invasive procedure. A 2010 telemonitoring study of more than 1,600 patients with heart failure who reported weight changes to their doctors found that this reading did not cut down on the number of deaths.
Instead the new monitors, Fonarow notes, "allows for proactive management to address fluid accumulation early and to potentially prevent hospitalization for worsening heart failure."
Its daily reports promise a much more specific and exacting opportunity to practice personalized medicine, tailoring treatment to individuals as their condition changes, notes William Abraham, a cardiologist at The Ohio State University Medical Center who is a consultant for CardioMEMS and co-author of the new study.
Sensing the pressure
Older implantable cardiac devices have a solid track record of keeping heart patients alive longer. But these devices need power sources, such as internal batteries (which require changing) or electrical leads (which can break).
The new device has no internal power source and no major moving parts so, as Abraham points out, "there's not much to wear out." It uses microelectromechanical systems (MEMS) technology to measure subtle changes in the surrounding artery's pressure.