Transcatheter Pacing System: The world’s smallest cardiac pacemaker

In the case of cardiac arrhythmia, the normal heart rate gets out of balance due to various reasons. Treatment with medication is oftentimes sufficient to remedy the condition. In other cases, it is necessary to implant a cardiac pacemaker. Just like with any intervention, this type of surgery also involves risks. In the worst-case scenario, this can lead to abnormal wound healing or obliteration of the vascular system.


Photo: Cardiac pacemaker next to transcatheter pacemaker

The Transcatheter Pacing System is only one-tenth of the size of a normal cardiac pacemaker; © Universitätsklinikum Düsseldorf, Unternehmenskommunikation

For the first time ever, a transcatheter pacemaker was implanted at the Clinic for Cardiology Pneumology and Angiology at the University Hospital Düsseldorf (German: Klinik für Kardiologie, Pneumologie und Angiologie des Universitätsklinikums Düsseldorf), which is directly inserted into the heart as a fully self-contained system using minimally invasive surgery. It signifies substantial progress in the medical treatment of patients with cardiac pacemakers.

Miniaturized cardiac pacemaker

The fundamental difference between the Micra (Medtronic GmbH) transcatheter pacemaker and traditional cardiac pacemakers is that this tiny device is able to do without an electrode and is inserted into the heart via the femoral vein. By comparison, it is only one-tenth of the size, merely weighs 1.75 grams, is 26 millimeters long and 6.7 millimeters in diameter. This equates to roughly the size of a large vitamin capsule. "This is the actual engineering masterpiece," says PD Dr. Dong-In Shin, Director of the Rhythmology Department. "The device exhibits all functions and scope of a unicameral pacemaker. The capsule-sized pacemaker is even safe to use in MRI scanners up to 3 Tesla."

With the help of a catheter, the transcatheter pacemaker is first inserted via the femoral vein – the vena femoralis –into the superior vena cava that flows directly into the heart and is then positioned inside the right ventricle of the heart. It is subsequently being tested and programmed with an external device. "The transcatheter pacing system has a passive fixation mechanism," explains Shin. "This means that the moment the capsule is being detached from the catheter, nitinol anchors expand. They are made of very soft metal. The internal wall of the right ventricle is interspersed with tiny trabeculae, tiny fibers or rather muscle fibers, and the transcatheter pacing system attaches itself to it." The mini cardiac pacemaker then delivers the necessary electrical impulses to the heart wall.
Photo: Dr. Shin during the minimally invasive interventio

PD Dr. Shin during the minimally invasive intervention: The transcatheter pacemaker is inserted via the femoral vein of the patient;& copy; Universitätsklinikum Düsseldorf, Unternehmenskommunikation

Easy use thanks to minimally invasive intervention

The transcatheter pacing system is especially suited for patients where an implantation via the subclavian vein under the collarbone is barely or not an option due to pre-existing conditions. In addition, risks like infections can be curtailed. "There is no need for an incision under the collarbone. Potential problems such as abnormal wound healing, vascular obliteration or inflammation around the electrode can be avoided with this novel device. The concept of an interventional transcatheter pacemaker was created to avoid all of these risks," Shin continues.

Battery capacity is depleted after ten years. The capsule-sized device remains in the heart even when it is no longer working. "If the concept of the capsule-sized device is meant to be maintained, another capsule-sized device based on the same principle is placed next to the old device. However, the process cannot be continued indefinitely. This is why the capsule-sized device is primarily intended for older persons past the age of 75."
Photo: Radiograph with transcatheter pacemaker in the middle

Radiograph of a heart: The transcatheter pacemaker is clearly to identify. Tiny nitinol anchors ensure that the pacemaker remains at its predetermined place;© Universitätsklinikum Düsseldorf, Unternehmenskommunikation

Preclinical study confirms capability

The device is already CE approved. According to Shin, the certification is based on the findings of a preclinical study in which 140 patients already underwent an implantation. The data evaluation and presentation was just recently performed during the annual session of the Heart Rhythm Society. Shin continues, "The data analysis was very positive. There were no fatalities, no displacements, that is to say, the capsule-sized device was not swept away and there were no significant incidents. The electrical data was excellent and stable. Now, of course, we need to await the long-term progress."

Shin also assumes that the implantation will increase due to the CE certification. In his view, the potential of the capsule-sized device is already undisputed. To replace the traditional cardiac pacemaker in clinical practice, however, the current version is not yet technically mature enough. "I believe the capsule-sized device represents a potential future key technology. If there are further technical modifications, for instance, rechargeable devices, the chance to stimulate multiple heart ventricles or if there could be a defibrillator function, it could potentially entirely replace the previous therapy. I estimate we are technically still five to ten years away from this."
Photo: Melanie Günther; Copyright: B. Frommann

©B. Frommann

The article was conducted by Melanie Günther and translated from German by Elena O'Meara.