In time with the breath
A pacemaker that adapts to breathing helped sheep hearts pump more blood
Anastasia Kuznetsova-Fantoni, N+1
New Zealand researchers tested an electrocardiostimulator on sheep that modulates the heart rate in accordance with breathing. In experiments on sheep, it increased cardiac output by 20 percent compared to a standard pacemaker. In addition, the experimental device slowed down the hypertrophy of the heart, which progressed in sheep due to heart failure. The scientists told about their invention in Basic Research in Cardiology (Shanks et al., Reverse re-modeling chronic heart failure by reinstating heart rate variability).
The human heart does not always beat with a constant rhythm. Moreover, its variability is one of the characteristics of a healthy heart. The heart rate increases during inhalation and decreases during exhalation. This phenomenon is called respiratory arrhythmia, it is characteristic of a healthy heart and disappears with cardiac diseases.
For people with impaired heart function, for example, with severe arrhythmias or heart failure, an electrocardiostimulator is installed, but such devices make the rhythm monotonous, which means that the contractions of the heart are no longer synchronized with breathing.
Researchers from the UK and New Zealand led by Julian Paton (J. F. R. Paton) from The University of Auckland tested whether there are advantages of a pacemaker that adjusts to the respiratory rhythm. Scientists have been working on such an electrocardiostimulator for more than ten years. The device they created reads the electrical activity of the diaphragm during breathing, and then sends impulses to the heart in accordance with the breathing phase — the rhythm slows down, then accelerates.
The device was tested on sheep: six animals were given a standard pacemaker, six more were experimental, and five sheep became control animals for which the device was not installed. All sheep were induced heart failure, and their hearts began to pump less blood. During the experiment, blood pressure, cardiac output and heart rate were recorded in all animals.
The installation of an electrocardiostimulator that adjusts to the respiratory rhythm increased cardiac output by an average of 1.4 liters per minute, which is 20 percent more than that of a standard pacemaker and the control group.
After the end of the experiment, a biopsy of the heart muscle was taken from the animals, and it turned out that the sheep, which had an electrocardiostimulator adjusted to breathing, had less pronounced cardiomyocyte hypertrophy than in the other two groups. This property is very important for patients with heart failure, in which the heart is usually enlarged to compensate for the decrease in function. This year, the researchers plan to start clinical trials of the device, for which they are already recruiting the first patients.
Pacemakers are constantly being improved. We talked about the absorbable device that is planned to be used in patients after surgery, as well as about an autonomous pacemaker that is powered by contractions of the heart muscle.
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