Leadless Miniature Pacemaker Revolution
Dr. Philippe Ritter
Technological advances are giving cardiologists better tools and making treatment safer for heart patients. That was the headline news from this June”s Cardiostim conference, where cardiologists from around the world gathered to discuss the latest innovations in their field.
One of the most important cardiological revolutions over the last two years has been the increasing use of leadless miniature pacemakers, says Cardiostim”s chairman, Dr. Philippe Ritter, from the Electrophysiology and Cardiac Pacing department at the University of Bordeaux.
DUE TO THE AVAILABILITY OF THESE SYSTEMS WHICH PROVIDE REALLY PRECISE INFORMATION, ABLATION TECHNIQUES HAVE BECOME MUCH MORE EFFICIENT AND MUCH FASTER AND THE RESULTS ARE QUITE SPECTACULAR.Dr. Philippe Ritter
The old-fashioned pacemaker is composed of a titanium box known as the “can”, and wires. The can, which contains the battery and electronics to pace the heart, is placed by surgeons under the skin at shoulder level, and connected through veins to the heart with up to three wires, the number depending on various criteria including the patient”s condition.
The presence of the box and wires can introduce a number of complications. To access the vein to implant an old-fashioned pacemaker, surgeons sometimes have to puncture the vein beneath the clavicle, and under this vein are the lungs – if the lungs are punctured it can cause pneumothorax. Other risks include bleeding, vascular perforations, displacement of the wires within the first couple of days after surgery, infections, and thrombosis – occlusion of the veins because of the presence of an artificial material in them.
“For years we were looking for the absence of the can and the wires,” says Dr. Ritter. “Engineers tried to conceive leadless systems which would contain everything in a single capsule: the battery, the electronics, the electrodes to pace the heart, and for this to be directly implanted into the heart without any wires. The fact is that if you”re able to implant such capsules you get rid of [many of] the complications.”
This kind of leadless, miniature device was pioneered in 2013 and are becoming increasingly mainstream. The new devices are 80-90% smaller in mass than conventional pacemakers and are, says Dr. Ritter, much less invasive, right down to the procedure for implantation. “Instead of finding a vein at the shoulder level, where there is also a big artery, lungs and nerves, you just have to puncture the femoral vein at the groin level that leads up to the heart - which is very simple to do and not that dangerous because there”s no critical structure in this area.”
At Cardiostim, the latest findings were shared: there have now been more than 2500 patients treated worldwide with the Micra, one of these modern pacemakers. And, says Dr. Ritter, “what”s spectacular is the major complication rate, which was 4%, is decreasing all the time, while the number of doctors using the device is expanding. The first implanters transferred their experience to the new implanters and nowadays, major complications have gone down to 2.4%. This is much less than with the conventional system.”
The only restriction stopping hospitals using these devices more is the fact they currently cost around three times as much as the old style of pacemaker. But this should come down in future.
How is the technology evolving? “We do need more technology to have more complex devices,” says Dr. Ritter. So far, he explains, the new pacemakers are “single chamber” devices where the pacemaker controls the right ventricle. The next step will be “dual-chamber” devices to control the atria, the upper chambers of the heart, at the same time – which would make sense, because in a normal heart, the impulse of each heart beat starts in the atria. Dr. Ritter says: “Medtronic engineers are working on a system which would be able, with a single capsule implanted in the right ventricle, to detect the activity of the atria, which are at another floor in the house, as it were. It”s like being able to detect what your neighbour is doing in another flat.”
Another major area of cardiological advance that took centre stage at Cardiostim was the use of subcutaneous Implantable Cardioverter-Defibrillators (ICDs). These are not brand new, but, says Dr. Ritter, “it looks like the use of those devices is quite widespread now and the goal, again, is to reduce complications due to the endovenous leads [so that] the wire does not run within the veins and heart cavity.”
What is coming, he adds, is the hybrid combination of leadless pacemakers and subcutaneous ICDs, which will further reduce complications. “The two systems have to communicate and this is the major difficulty to be solved in the future,” says Dr. Ritter – but he adds: “That will come very quickly. In vivo experiments in sheep already have shown it is feasible.”
One other highlight for Dr. Ritter from this year”s Cardiostim is the improving treatment of cardiac arrhythmias, caused by faulty electrical circuits in the heart. He says: “What is spectacular today is the usefulness of the navigation systems we have to perform ablations of arrhythmias, not only at the atrial level but also at the ventricular level.”
Ventricular tachycardia ablations can now be treated as a matter of routine, according to the latest research shared at Cardiostim. Malfunctioning groups of cardiac cells can trigger electrical impulses which disturb the normal functioning of the heart, inducing tachycardia – abrupt accelerations of the heart rate which are abnormal and have nothing to do with exercise. Tachycardia can also be caused by heart disease inducing fibrotic growth in the myocardium (heart muscle), interfering with normal cardiac electrical activity.
Surgeons can use a technique called ablation to treat tachycardia. They temporarily implant catheters into veins or arteries to the heart and select the different locations where the abnormal cells are and cauterize them, destroying the faulty circuit. To do this, they need a system which shows where those groups of cells are, and sophisticated electrophysiological mapping systems are now available which help localize the precise cells responsible.
Dr. Ritter says: “Due to the availability of these systems which provide really precise information, ablation techniques have become much more efficient and much faster and the results are quite spectacular.”