Doctors at the Cleveland Clinic began to suspect in 2012 that something might be wrong with a high-tech implant used to treat patients with advanced heart failure like former Vice President Dick Cheney.
The number of patients developing potentially fatal blood clots soon after getting the implant seemed to be rising. Then early this year, researchers completed a check of hospital records and their concern turned to alarm.
The data showed that the incidence of blood clots among patients who got the device, called the HeartMate II, after March 2011 was nearly four times that of patients who had gotten the same device in previous years. Patients who developed pump-related clots died or needed emergency steps like heart transplants or device replacements to save them.
“When we got the data, we said, ‘Wow,’ ” said Dr. Randall C. Starling, a cardiologist at Cleveland Clinic.
On Wednesday, The New England Journal of Medicine posted a study  on its website detailing the findings from the Cleveland Clinic and two other hospitals about the device. The HeartMate II belongs to a category of products known as a left ventricular assist device and it contains a pump that continuously pushes blood through the heart.