Patients with heart failure take a variety of medications to help their heart do its job.
Keeping these medications in balance with the body’s changing needs is an ongoing challenge. Physicians generally rely on clinical symptoms to make treatment decisions, but by the time patients complain of shortness of breath or swelling in the legs, their heart failure may have significantly worsened. Sometimes, hospitalization is necessary to bring their symptoms under control.
Enter CardioMEMS, a tiny, implantable device that measures pressures in the pulmonary arteries (PA). High PA pressures can force fluid to leak into lung tissue, causing shortness of breath. High PA pressures indicate worsening heart failure and can be associated with fluid retention. CardioMEMS alerts physicians to rising PA pressures, giving them time to adjust the patient’s medications before symptomsappear.
“By the time a patient experiences symptoms, there is evidence that PA pressures may have been rising for a week or more. It’s very helpful to have concrete evidence of what is happening and not have to make decisions based solely on symptoms,” says Cleveland Clinic heart failure specialist Miriam Jacob, MD.
The first early warning device to successfully impact outcomes, CardioMEMS helps heart-failure patients feel better and been shown to reduce hospitalizations for the condition by as much as two-thirds.
How the Device Works
CardioMEMS is a tiny rectangle about the length and thickness of a dime folded in half. It houses a microchip-sized pressure sensor, but has no battery.
In a 60- to 90-minute outpatient procedure, a heart-failure specialist or interventional cardiologist slips the device into a branch of the pulmonary arteries through a vein in the leg. Wire loops on the ends of the device prevent it from slipping out ofplace.
To take a pressure reading, the patient simply lies on a special pillow that transmits their PA pressures wirelessly to a secure website. “I like the fact that it’s not necessary for the patient to take any action besides leaning on a pillow,” says Dr. Jacob.
Members of the medical team review the numbers, looking for indications the patient’s pressures might be rising. “There is no standard PA pressure, so it’s not necessarily an individual reading that alerts us to a problem. We look for a trend over time,” Dr. Jacob explains.
When rising PA pressures are spotted, a decision is made to increase one of the patient’s medications to drop their blood pressure or relieve some fluid that has built up.
“A few days later, we may notice their pressures are too low, meaning we need to back off the medications. Maintaining this balance is what heart-failure management is all about,” says Dr. Jacob.
Who Benefits from CardioMEMS?
CardioMEMS is considered appropriate for patients with moderate (New York Heart Association [NYHA] Class III) heart failure, who have been hospitalized at least once for symptoms in the past 12 months. Patients with this class of heart failure are hampered by symptoms such as breathlessness, fatigue, palpitations or chest pain while performing less-than-ordinary activities.
“These patients are sick, but not too sick,” says Dr. Jacob. “If you don’t have symptoms, or if your heart failure has advanced to the point we are discussing a left-ventricular assist device (LVAD) or heart transplant, this device isn’t for you,” she says.
CardioMEMS can be used for monitoring patients with either systolic or diastolic heart failure. Having an option for patients with diastolic heart failure delights Dr. Jacob, as few medications for this form of heart disease exist. “Personally, I think this is super helpful, because these patients primarily suffer from congestion and feel terrible,” shesays.
Because heart failure can be slowed but not stopped, the device is never removed. Over time, endothelial cells grow over the wire loops, incorporating the device into the artery. CardioMEMS appears to be safe, as no significant infections have ever been reported. Having the device does not prevent the patient from having future procedures, such as cardiac catheterization, LVAD implantation or a heart transplant.
“The patients’ biggest fear is what the implantation procedure is like. Once I tell them how simple it is, and they see how small the device is, most become very excited and want to pursue it,” says Dr. Jacob.