Some patients could be supported until the heart heals itself.
A new generation of cardiac devices scheduled for human trials in Europe and the United States next year has heart surgeons talking about a possible sea change in the treatment of patients suffering from the most severe level of heart failure, which affects 150,000 to 200,000 Americans a year and kills thousands.
Traditionally, many of these patients received mechanical heart pumps, which kept them alive until they could receive transplants. But with an aging population and a limited supply of donor hearts, a growing number of cardiologists in Minnesota and around the country are discussing novel strategies: whether some older patients should just expect to live with the pumps, for example, and whether the newest models can be used as “bridges” for some patients while new treatments help their hearts recover.
Consider Susan Tretter.
When the 61-year-old resident of Montrose, Minn., met Dr. Benjamin Sun the day after Thanksgiving last year, she had already been read her last rites and was making funeral plans with family members gathered at her hospital bedside.
Her heart had ruptured, and only a thin sack of tissue surrounding it kept her alive. A simple cough could have killed her.
Alerted by Tretter’s physician, Sun operated on her heart, redirected the blood flow and implanted a small, propeller-driven pump.
But instead of sending her home to wait for a heart donor, Sun and a team of doctors treated her as if she might recover.
Exactly six months later, Tretter’s heart had healed enough to pump on its own, and Sun removed the device.
“I just love the little man,” Tretter said last week. “I believe I have been given a second chance at life.”
Sun is a cardiac and thoracic surgeon for the Minneapolis Heart Institute at Abbott Northwestern Hospital and a research physician for the Minneapolis Heart Institute Foundation with a background in molecular biophysics and biochemistry. He describes himself as an “old man” in the realm of heart pumps.
The first generation of pumps moved blood from the body to a chamber and then back again, much like a human heart does. Sun said these bulky pumps were nicknamed “thumpers” by hospital staff because of the noise they made. Patients moving around the hospital knew the location of every power outlet, he said, because the batteries lasted just 30 minutes.
The next generation of pumps, now in use, are much smaller and more efficient because they rely on high-speed rotors to move the blood. But they lack the ability to create a pulse and may not empty the heart chamber completely, an action that allows the heart to rest and perhaps heal.
A third generation of even smaller pumps coming on line next year also relies on rotors, but these pumps will be programmable to create a pulse. Sun and several other researchers hope that by adjusting the pulse rate therapeutically, they’ll be able to help restore heart strength and wean patients from the pumps.
Sun, a consultant to a California company that manufactures a widely used pump called the HeartMate II, helped direct large-animal studies for the HeartMate III. The device will go into clinical trials in Europe and the United States next year.
Relax and recover
In theory, the flow rate on new pumps can be turned up high to let the heart rest and then turned down to stress the muscle and test whether the pump can be removed, said Dr. Emma Birks of the University of Louisville.
Birks is one of the world’s leading researchers in the field and was part of a famous study at Harefield Hospital in London that led to the removal of the pumps in 11 of 15 patients.