LEADLESS PACEMAKERS DR. ANIRBAN KUNDU

WHAT IS A PACEMAKER?
A pacemaker is a device inserted into your heart, most commonly in case of abnormally slow heart rates
(a condition called “BRADYARRHYTHMIA” ( brady, meaning slow and arrhythmia meaning
disturbance of heart normal rhythm). However there are other conditions that may necessitate
implantation of the device. These are:
1. slow heart rate as mentioned above (the commonest indication)
2. too fast heart rate, that is not able to be controlled by medication, that could be potentially fatal, and
3. heart failure, when increasing the heart rate could improve its pumping action.
TYPES OF PACEMAKERS
Traditionally, there are 3 types of pacemaker:
1. one lead pacemaker (single chamber pacemaker)
2. two lead pacemaker (dual chamber pacemaker)
3. three lead pacemaker (biventricular pacemaker)
This classification is based on the number of leads connecting the pacemaker to the chamber of the heart.
What type of pacemaker is implanted depends on the condition for which it is being implanted.
Some people need a special pacemaker called a cardiac resynchronisation therapy (CRT) pacemaker. It’s
used when the left and right ventricles of the heart beat out of time with each other, causing a drop in
cardiac output, or the volume of blood pumped to the body. By ensuring that both ventricles pump in
unison, CRT increases the output of the heart, thereby improving symptoms of heart failure.
The function of the leads is to transmit the impulses from the pacemaker to the heart muscle and cause it
to contract at the rate set during the implantation. Normally the leads are threaded through the upper limb
veins to the heart chamber, while the pacemaker itself is implanted usually in the chest wall just below the
collar bone, beneath the skin via a small incision, under local anesthesia.
Sometimes, leads may get displaced, lose contact with the heart muscle, or the pacemaker may get
infected and protrude through the skin, or may simply cause discomfort to the patient. These factors,
along with the general trend towards miniaturization, have lead to the evolution of leadless pacemakers. A leadless pacemaker is a small, single-piece device that a cardiologist inserts into the heart chamber. This
is done by passing it through a tube threaded through the thigh vein and deposting it in the muscle of the
right ventricular chamber (see diagram). Unlike traditional pacemakers as described above, all the parts of
a leadless pacemaker are inside one device. There’s no separate battery. And it doesn’t need leads (wires)
because the whole device sits in your heart’s right ventricle.
Leadless pacemakers are about 1 to 1.5 inches (3 to 4 centimeters) long. The device looks like a small
metal cylinder. It’s smaller than an AAA battery. Newer such pacemakers are even smaller, just about the
size of a grain of rice.

How does a leadless pacemaker work?
A healthcare provider programs and customizes your device to send small electrical impulses to your heart
muscle when it needs it. Just like leaded pacemakers, a leadless pacemaker can sense your heart’s own electrical signals. It can provide additional electrical
impulses when your natural ones aren’t frequent enough.

Advantages of a leadless pacemaker
Benefits of a leadless pacemaker include:
No need for connecting leads (wires), a separate power
source or the creation of a surgical pocket on the chest to
hold the power source. These are the most common causes of traditional pacemaker complications
(infections or broken leads).
No lump under the skin on the chest or leads anchored to the muscle, which can cause minor
discomfort.
No chest incision or scar from generator placement and replacements.
A shorter procedure time than a traditional pacemaker implant procedure.
With no wires or generator, there’s no need to limit upper body activity after the implant.
It’s one piece, which is 90% smaller than a traditional pacemaker.
It’s safe to use in an MRI (magnetic resonance imaging) machine.
It’s appropriate for some people who aren’t candidates for a traditional pacemaker.

Disadvantages of a leadless pacemaker
Disadvantages of a leadless pacemaker include:
It can only pace one ventricle (heart chamber). (as opposed to the dual chamber type mentioned
above)
It can’t treat abnormal fast heart rhythms.
Swelling and bleeding at the incision site (the most common possible problems after a leadless
pacemaker implant). Typically, these aren’t life-threatening but may lead to a longer hospital stay
or slower recovery.
Risk of heart puncture during implantation.
Higher cost than traditional pacemakers.

Studies have found an implant success rate of 95% to 99%, with complication rates below 2%. The
battery in a leadless pacemaker lasts about 5 to 15 years. When the battery gets too low, a provider can
turn off your old pacemaker and put in a new leadless pacemaker. The pacemaker itself may last 10 years.
There’s enough room in your right ventricle for more than one pacemaker if they need to leave the old one
there. However if, for any reason the previous device needs to be removed, this can be done.
To conclude, leadless pacemakers are the new thing in pacemaker technology, but are yet to completely
replace traditional pacemakers. For those patients requiring a single chamber device , these appear to be
set to be the gold standard, provided cost is not an issue. However, with the pace of medical research, it
won’t be too long, when dual chamber and CRT pacemakers will also evolve to leadless models.