At least 26 patients in advanced heart failure have died after replacing the controller for an Abbott Laboratories blood pump while out of the hospital.

Abbott has issued an alert for 28,882 HeartMate II controllers that includes new software and alarm guides, after reports of 70 incidents in which the life-preserving device malfunctioned after a patient changed out the controller at home. Those incidents included 26 deaths and 19 injuries.

"Patients may sometimes need to change to their backup back-up system controller during the course of ventricular assist therapy. The change should be done quickly and in the hospital, because it can present a significant challenge to patients that are elderly and/or untrained. For these patients, a slow or improper … changeover places them at risk of serious injury or death," according to the Food and Drug Administration.

Abbott — which acquired Minnesota-based St. Jude Medical and its HeartMate II Left Ventricular Assist Device (LVAD) in January — sent out its product alert to doctors across the country on March 29. On Tuesday, after stock markets closed, the FDA issued a recall notice classifying the prior Abbott communication as a Class I recall, the most serious category reserved for potential life-threatening situations.

It's not clear when the patients died or were injured, but the FDA recall notice says the devices were distributed between July 2012 and December 2016. Distribution of the affected controllers was halted in March 2017, the recall notice says. The recalled Model/Item numbers are 105109, 106015, 106762 and 107801.

An LVAD is an implantable device with a six-figure price tag that essentially pumps a person's blood when the heart is too weak to do it on its own. The device was originally intended to keep a person alive just long enough for them to get a heart transplant, but in 2010 the FDA approved the HeartMate II as a permanent therapy for people who will never qualify for heart transplantation due to age or other factors.

The implanted device includes a Pocket System Controller, which is a power supply outside the body that needs to be swapped out periodically. Abbott recommends patients have these controller exchanges done in the hospital or clinic, not at home.

"Despite past efforts to improve training and education, we are aware of patients experiencing a very low level of adverse events as a result of unnecessary patient controller exchanges," Abbott spokesman Justin Paquette said via e-mail. "We are updating its alert guides, conducting a software upgrade and adding controller alignment markings for the HeartMate II System Controller as part of a continued effort to ensure patients are successfully able to exchange their pocket controller in emergency situations."

Patients and their families are often sent home from the hospital with multiple sets of the battery units, with the expectation that the patient can do a swap-out in an emergency situation after the training, but nonemergency changes should still be done in clinic, said Dr. Vibhu Kshettry, a cardiovascular surgeon at Abbott Northwestern Hospital's Minneapolis Heart Institute who has implanted many LVADs.

Kshettry said the end-stage heart failure patients who need an LVAD are typically in fragile health, which means that problems with the devices can quickly lead to severe consequences, especially for patients who are 100 percent dependent on the devices.

HeartMate II controllers have been subject to other product advisories linked to deaths, including one in 2015 that reminded hospitals to carefully monitor the expiration dates of the lithium-ion backup batteries in the controllers. If an older battery was left in the controller, the patient might see a noncritical alarm that could cause them to change out batteries when they didn't need to, the 2015 notice warned.

Two people died after trying to change out their batteries in response to those warnings, the 2015 notice said. Other safety notices were published about various aspects of the controllers in 2008, 2010, and 2014.

This week Abbott didn't explicitly link the latest alert to the issues outlined in past notices, but the latest advisory says a new software update should eliminate noncritical alarms from appearing on patients' controllers. Those alerts will still show up on the physician's system monitor during routine office visits.

Paquette noted that while the company is working to spread the word about the issue, it is not asking for any LVADs to be removed from patients.

"This has been classified by the FDA as a Class I recall, however this is not about recalling products; rather the focus is on communication to physicians so they can ensure their patients have their controller exchange completed in a clinical setting," he said.

The HeartMate II was first commercialized by California-based Thoratec Corp. in 2008 as a slimmer, safer and more durable version of earlier left-ventricular heart pumps. The device takes blood out of the left ventricle and runs it through an enclosed axial propeller before pumping it back into the aorta, creating the pressure needed to pump blood through the body's main artery for delivering fresh blood to organs.

At least 28,000 of the devices are on the worldwide market, including commercial sales and clinical trials. A new device called the HeartMate 3 is still in clinical trials for potential U.S. approval.

In October 2015, Thoratec was acquired by St. Jude Medical for roughly $3.3 billion. It was St. Jude's largest-ever acquisition, and also, it turned out, the last major deal that St. Jude completed before being acquired by Abbott 14 months later.

The other major ventricular assist device on the market is sold by Medtronic, which acquired its maker, HeartWare International, in a $1.1 billion deal in June 2016. The HeartWare LVAD has also been hit with recalls, including a Class I recall several months after the deal closed that said 8,800 device controllers were subject to an issue in which moisture could get inside the controller and damage it.

Joe Carlson • 612-673-4779