‘Natural’ Pacemaker Successfully Tried In Humans

A pacemaker that mimics the heart’s naturally variable rhythm is being trialled in humans for the first time with no adverse effects reported and the promise of improved outcomes.

The first-in-human trials started in the Waikato, New Zealand just before Christmas and are now being conducted in Adelaide and Melbourne, Australia, and Bristol and Cardiff in the UK.

Usual pacemakers support a regular, monotonic beat in the patient’s heart, but our hearts naturally beat irregularly depending on our breathing.

The new pacemaker would vary according to respiration and has shown improvements in the health animal models so far, with a new study offering further evidence. See below.

The first patient was in Waikato hospital just before Christmas. The pacemaker is being tested in patients coming out of a heart operation in which temporary pacing wires are fitted that allows doctors to connect the new pacemaker to them for a few days.

Professor Martin Stiles, a cardiologist at Waikato Hospital, is overseeing the trial there and is hopeful about the novel pacemaker.

“This new technology is moving toward replicating the way nature has evolved pulse variability to make the most efficient use of the heart’s function,” Stiles says.

“Remarkably, researchers have found in sheep that our pacemaker allows the ability to exercise again despite heart failure, which usually prohibits any exertional activity, says study lead Professor Julian Paton, director of Manaaki Manawa, Centre for Heart Research in the Faculty of Medical and Health Sciences at Waipapa Taumata Rau, University of Auckland.

“We believe that, if patients have the choice of a pacemaker, then one that improves exercise performance without the need to undergo training will be a preferred option,” Paton says.

The new study led by colleague Associate Professor Rohit Ramchandra tested whether sheep’s ability to exercise was improved by a variable heart pacemaker. Sheep's heart functions are similar to human's.

“This is important since the ability to exercise can dramatically improve quality of life in patients with heart failure,” Ramchandra says.

“Our findings indicated that respiratory heart rate variability pacing improves baseline levels of heart function but also dramatically improves the capacity of the heart to pump blood during exercise. This translates to more blood being delivered to muscles during exercise.

“Remarkably, respiratory heart rate variability pacing also improved the recovery time of the heart post-exercise, which is an established marker of physical fitness.”

The researchers also tested whether the variable pacing improved heart function when the sheep remained on heart medications.

“We found variable pacing continues to improve heart function against a background of current medication. None of these changes happened in the group which underwent conventional monotonic pacing.”

• Read the study in Basic Research in Cardiology
• Find out about animal-based research at the University of Auckland.

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