A change of pace
FEATURE - 25TH SEPTEMBER 2017
Dr Oliver Segal, consultant cardiologist and electrophysiologist at The Harley Street Clinic on the leadless pacemaker
The main reason someone would need a pacemaker fitted is that their heart has developed a condition that causes it to beat too slowly. This can cause profound dizziness and significant tiredness after even light exercise, as the heart isn’t able to respond correctly by increasing the heart rate. A pacemaker helps the heart to beat at an appropriate speed. Once we fit one, it is usually there for life, as the condition we are treating is unlikely to improve.
The traditional pacemaker consists of a battery fitted just under the skin below the collarbone, linked up to ‘pacing leads’, which are fed through blood vessels to the heart. At the end of each lead is an electrode, which is attached to the heart muscle and allows precise voltages to be applied.
Pacemakers work by recording the heartbeat and, if it falls below a certain rate, sends an electrical pulse down the leads and into the heart muscle. This pulse spreads through the heart, causing it to contract.
Risk of infection
But while the traditional pacemaker has saved millions of lives, its combination of battery and leads poses several risks, the biggest of which is infection. When you change the battery or leads, you are opening the device up to the air, and bugs can get in. Once an infection has taken hold, the patient may need major surgery to replace the pacemaker and require a long stay in a hospital to treat the infection.
Also, removing old pacing leads can be a difficult process. It is possible while removing or inserting the leads to inadvertently damage the lining of the lung, puncture the artery you are passing the pacing lead through, or damage or puncture the heart wall. This can require emergency surgery or lead to death in rare cases.
The leadless pacemaker has been around for about two years and uses similar pacemaker technology, but everything has been miniaturised. The battery, the electrodes and the mechanism that fixes the device to the heart wall are all built into one small housing. It is so small, it can live entirely within a chamber of the heart, eliminating the need for leads.
Tiny standalone device
These new pacemakers are put in place using a catheter. This is inserted at the top of the leg and fed through the veins to the heart, removing the need for chest surgery. When the catheter is withdrawn, you are left with this tiny, standalone device in the heart.
Leadless pacemakers have radically reduced the risk of infection. In more than 2,000 cases using leadless pacemakers so far, there has only been one case of infection. Almost eradicating this complication reflects a huge step forward. No procedure is completely risk-free, but complications caused by leadless pacemakers can generally be fixed very quickly, and have not been the kind to cause long-term problems.
Leadless pacemakers are fairly new technology, so there is still work to be done. Currently, they are only suitable for people who need stimulation in one chamber of the heart—traditional pacemakers can stimulate up to three chambers. Hopefully, we will soon develop the technology for individual pacemakers to be placed in separate chambers, but for this to work, the communication between them has to be incredibly robust, so that they work with and not against each other. A lot is being done in this area at the moment.
In many ways, the management of the pacemaker remains the same. We wirelessly download the information that the pacemaker collects and it can all be stored in the cloud, which the consultant has access to at all times. If either the heart or the device moves outside set parameters, a warning is sent to us, which means the consultant will often know that action is required even before the patient does.
The big winners are the patients. As well as the reduction in potential complications, another advantage is that the battery life is about 13 years—longer than the traditional pacemaker—which means fewer visits to people like me. And when the battery does run out, we can add a replacement pacemaker without having to remove the old one—the old unit has no negative impact on either the heart or the new pacemaker. This is a major advantage, as it can be very difficult to remove pacing leads that have been in situ for many years.
Finally, patients will soon be able to access information about how their device is operating, via an app on their phone. This will bring real reassurance if they are feeling unwell, as the natural inclination is to worry that the pacemaker has malfunctioned. The app will offer the assurance that it is operating properly, and that what they are feeling is simply one of the usual illnesses that happen to us all.