An Implantable Monitoring Device for Congenital Heart Disease Patients

Curtis J. Daniels, MD
Curt Daniels, MD, director of the Adolescent and Adult Congenital Heart Disease Program at The Heart Center at Nationwide Children’s and senior author of this recent study. 

In a collaboration between Ohio State University and Nationwide Children’s Hospital, physician-researchers have demonstrated the feasibility of an implantable hemodynamic monitoring device in adults with a specific type of congenital heart disease. In a small population of patients with single ventricle physiology, the device proved technically successful and had no adverse effects. The results are reported in the International Journal of Cardiology.

Patients with congenital heart disease who have only one functioning ventricle had poor survival outcomes until about 40 years ago when the Fontan procedure was introduced. The Fontan procedure diverts the blood away from one side of the heart directly into the lung. Although the procedure helps these patients survive into adulthood, they still experience issues related to heart failure that will necessitate a transplant for many.

The life-saving Fontan procedure also ends up increasing pressures in the vein system of the body, putting stress on organs such as the liver. Nearly all Fontan patients develop liver disease and it is thought that there is a relation between pressure in the veins (also called Fontan pressures) and extent of organ damage.

“As these patients progress, we want to know how aggressive to be with their therapies to improve their Fontan pressures,” says Curt Daniels, MD, director of the Adolescent and Adult Congenital Heart Disease Program at The Heart Center at Nationwide Children’s and senior author of the recent study. “But the only way to obtain Fontan pressures is via repeat heart catheterizations.”

Now there may be a less invasive option. The CardioMEMS™ system is an implantable hemodynamic monitor, originally developed for use in patients with acquired heart disease. The technology, a small wire device shaped like a figure eight with a microchip in the middle, is implanted in a lung blood vessel. From outside the body, a detector is used to transmit pressures in real time.

In this study, the safety and feasibility of the CardioMEMS™ system was evaluated in six adult Fontan patients. In addition to reporting no device-related complications, Dr. Daniels and his colleagues show that higher Fontan pressures are associated with symptoms of heart failure. Among the Nationwide Children’s faculty members who also participated in the study were Elisa Bradley, MD, and adult congenital heart disease specialist in The Heart Center, and Darren Berman, MD, co-director of Cardiac Catheterization and Interventional Therapy in The Heart Center.  

“When we saw pressures going up, this allowed us to treat the patients medically to improve their symptoms and keep them out of the hospital,” says Dr. Daniels, who is also professor of Clinical Cardiology at The Ohio State University College of Medicine.

There are some limitations to the device. For instance, it requires patients to acquire and send their own data, so they must be willing partners with their doctors.

Dr. Daniels and his colleagues have now placed the device in about 15 patients with various forms of congenital heart disease. In each case, the purpose is to improve symptoms at home and decrease hospitalizations.

“Our next steps are to apply more unique medical therapies, treatments we use in other forms of heart disease, to this population and really lower those Fontan pressures,” says Dr. Daniels. “We are starting to do more medicine trials, exercise trials, and eventually have this technology at other institutions so we can perform multicenter trials, as well.”

Reference:

Bradley EA, Jassal A, Moore-Clingenpeel M, Abraham WT, Berman D, Daniels CJ. Ambulatory Fontan pressure monitoring: Results from the implantable hemodynamic monitor Fontan feasibility cohort (IHM-FFC). International Journal of Cardiology. 2018 Oct 28. [Epub ahead of print]