Miniaturized pump may support hospital discharge for children awaiting heart transplant

A novel miniaturized implantable continuous flow left ventricular assist device (LVAD), the Jarvik 2015, has the potential to allow small children with heart failure to go home while awaiting heart transplant and shorten hospital stays.

In a first-in-human feasibility trial, the Jarvik 2015 LVAD met the primary endpoint of survival to 30 days without severe stroke or nonoperational device failure. All seven paediatric patients (median age 2.2 years, median weight 10 kg) who received the device implant survived for a median of 149 days (range, 5–188 days). [J Heart Lung Transplant 2024;43:889-900]

The pump operated at a median speed of 1,600 RPM while using between 1 and 4 watts of power. Median levels of free haemoglobin in the blood showed fluctuations across the study period: 19 mg/dL at day 7, 30 mg/dL at day 30, 19 mg/dL at day 90, then 30 mg/dL at day 180 or time of explant.

Of the patients, five received heart transplants, one recovered without needing a transplant, and one transitioned to a different type of heart pump. The patient with myocardial recovery had an ischaemic stroke on day 53 of device support, when the heart was strong enough to compete with the pump. Following pump removal, the patient continued to recover and remained alive 1 year on. Another patient experienced intractable ventricular arrhythmias requiring extracorporeal membrane oxygenation support and eventually was switched to a biventricular assist device.

The complications were manageable and similar to those seen with existing devices, the investigators noted. Responses to quality-of-life questionnaire indicated that the device was not a burden, did not cause pain, and allowed the patients to participate freely in most play activities.

The seven patients who participated in the feasibility trial had severe systolic heart failure and inadequate response to optimal medical therapy. Six children had dilated cardiomyopathy, and two had INTERMACS profile 1.

While the Jarvik 2015 was designed to allow children to await heart transplants at home, all patients in the trial remained hospitalized for monitoring. This allowed the investigators to closely track the patients’ blood pressure and haemoglobin levels, as well as monitor them for other complications.

Going tiny from bulky

Developed in response to the lack of FDA-approved LVAD for smaller children permitting routine hospital discharge, the Jarvik 2015 is slightly larger than an AA battery, small enough to be implanted in patients weighing as little as 18 pounds.

In comparison, the only ventricular assist device available to support small children with heart failure, a pump called the Berlin Heart, is not implantable. The device is about the size of a large suitcase, can weigh between 60 and 200 lbs depending on the model, and requires connection to the patient through two cannulas with the width of garden hoses.

“While we are extremely grateful to have the Berlin Heart, a life-saving device, ventricular assist devices for adults have been improving every decade, but in paediatrics we’re using technology from the 1960s,” stated lead study author Dr Christopher Almond, a paediatric cardiologist and professor of paediatrics at Stanford Medicine in California, US, in a news release.

Almond pointed to a significant gap between paediatric and adult heart failure treatment, saying that while adults have had access to implantable devices for over 40 years, allowing them to live relatively normal lives, children are still limited to external pumps like the Berlin Heart.

“There’s a huge difference in the medical technology available to kids and adults, which is an important public health problem that markets have struggled to fix because conditions like heart failure are rare in children,” he said.

In turn, the lack of child-sized heart pumps puts a strain on the medical system. Children with the Berlin Heart can occupy hospital beds in specialized cardiovascular care units for several months, accruing large medical bills, and potentially reducing the availability of these beds for other patients, according to Almond.

If the early findings are confirmed in larger trials, the Jarvik 2015 could transform the experience of waiting for a heart transplant for small children and their families, he said. Annually, an estimated 200‒400 children globally would be eligible for the device.