The 69-year-old former vice president is back in action, albeit a little thinner.
"He really doesn't have a pulse, but he has blood pressure because blood is being pumped out from his ventricle into the aorta at a constant pressure," explains Dr. Kirk Garratt, clinical director of interventional cardiovascular research at Lenox Hill Hospital.
But what exactly is beating in Cheney's chest?
Called an implantable left ventricular assist device, it "works like a little centrifugal pump," Garratt said. "It is like a spinning motor that acts like a fan to draw blood out of the pumping chamber, or left ventricle, and it propels the blood into the aorta."
Cheney's device, which is almost like a partial artificial heart, is battery-powered.
Implanted in the patient's chest, the device is connected to a cable that comes out of the body and connects to a mini computer that plugs into a battery pack. The patient wears a vest that holds these in place, and spare batteries must be carried as well.
"With a normal heart, the left ventricle fills with blood and the muscles of the heart all squeeze at once to push the blood out in one quick wave," Garratt said. "The pressure of that blood being pushed out into the arteries is what you feel as a pulse when you put your fingers to your wrist. But the pump works continuously, always drawing blood out of the left ventricle and propelling it into the aorta at a constant rate. So you don’t generate a pulse."
Typically, the pump's batteries last for around six hours, and then they must be changed.
But why does Cheney no longer have a pulse?
The mechanical heart works continuously to push the blood, rather than mimicking a heartbeat.
But don't think that just anyone can get this heart pump. Getting a pump like Cheney’s is major surgery and can require a lengthy hospital stay and recovery time.
"It’s a big surgery that carries with it very real risks," Dr. Mathew Williams, surgical director of cardiovascular transcatheter therapies at NewYork-Presbyterian Hospital Columbia told the Daily News. "We tend to put them into people who are going to die without them."
Cheney will likely have this device in place for the rest of his life.
Some patients are given this mechanical heart until they are healthy enough for a transplant. But in older patients like Cheney -- who has had five heart attacks -- a heart transplant is not always an option.
“Hearts are an exceedingly rare commodity,” Garratt says. “It’s hard to make the decision to give a heart to a man who is [close to] 70 when you know that means a 30-year-old may not be able to get it.”