It's part of a new system being tested at Einstein Medical Center.
Doctor Sumeet Mainigi says the sensor is implanted in the wall of the upper heart.
A wire connects it to a small transmitter in the chest.
It's designed to give doctors and patients early warning that fluid is building up in the heart.
"As the pressure starts to rise, the patient uses a handheld communicator, gets an alert that the pressure is starting to rise," says Dr. Mainigi.
"There's our pressure," says the doctor as the device beeps.
"They actually, at that moment, get a message of what medication change they should make," he continues.
The doctor also gets a record of the heart pressure.
He says it's a lot like how people with diabetes monitor their blood sugar.
And the hope is that small adjustments will prevent bigger problems.
For more information on the trial, go got www.einstein.edu.