The normal heart has a natural pacemaker. This is situated in the right sided upper chamber which is known as the right auricle. The impulse from the natural pacemaker travels along specialized conduction tissue to both the upper chambers, and then to both the lower chambers. This causes contraction of the upper chambers, followed by that of the lower chambers. Contraction is followed by relaxation.
In certain people with heart disease (for example, sick sinus syndrome), the natural pacemaker becomes weak and slow. As a result, the heart rate may become dangerously low.
In other people, the natural pacemaker may be healthy, but the specialized conduction tissue that connects the upper to the lower chambers is blocked. In these patients, the electrical impulses from the natural pacemaker cannot travel to their destination in the lower chambers, and the heart rate becomes dangerously low.
Artificial pacemakers are commonly implanted in subjects who have an insufficient heart rate.
These patients may have dizzy spells, and quite a few of them faint. Many of them become fatigued upon walking a few steps because of insufficient pumping of blood by the heart.
There are two different types of block in the heart.
Blood flows to the muscles of the heart through hollow pipes which can become choked by lumps of cholesterol. These blocks can be dilated by means of a balloon-and-stent to restore the blood flow.
The electrical impulse of the heart travels through solid wires that are known as the specialized conduction tissue. These have no hollow lumen, and therefore, cannot be dilated by balloon-and-stent. Medical science does not yet have the technical knowhow regarding the repair or replacement of the diseased conduction tissue. Therefore, we put in a pacemaker to generate the right type of electrical signals. We put in metallic wires to transmit these signals to their proper destination in the heart.
Single chamber pacemakers stimulate the lower chambers, but not the upper chambers. Now, good cardiac function requires the coordinated action of the upper and lower chambers.
This means that in a patient who has a single chamber pacemaker, the upper chamber remains inactive and does not contribute to pumping. The cardiac output in these patients is low. Many of these patients become so crippled that they are unable to walk beyond a few steps without taking rest.
This is the reason why we prefer to use dual chamber pacemakers.
There is a type of heart disease known as persistent atrial fibrillation in which the pumping function of the upper chambers is completely lost. These patients do not benefit from the use of dual chamber pacemakers. So, we put in a single chamber pacemaker when they develop high grade heart block.
Take the example of normal human beings. Their heart rate is low when they are at rest, but it becomes higher when they exercise.
Ordinary pacemakers, no matter whether they are single or double chamber varieties, are unable to accelerate when the subject walks or runs to catch a bus. Such persons suffer from fatigue during ordinary physical activity.
Rate responsive pacemakers have a small microchip which tells the pacemaker that the subject has become physically active. The pacemaker now fires at an increased rate, and the heart rate rises. This type of pacemaker gives the wearer a much better quality of life.
MRI (= Magnetic Resonance Imaging) is a form of scanning that is used to study different parts of the human body such as the brain, heart, abdomen, joints, and so on. Since it involves very strong magnetic fields, the patients should not have any implants in the body that contain magnetic materials such as steel.
MRI compliant pacemakers are an important improvement in pacemaker technology. Patients having these devices can safely undergo an MRI scan.
An AICD (A= Automatic, I= Implantable, C= Cardioverter, D= Defibrillator) looks like a pacemaker, but is a more bulky device. It has some additional functions.
Sometimes we come across patients whose hearts are enlarged and contract poorly. They are susceptible to have certain types of irregularity of the cardiac rhythm that are harmful. The AICD is expected to give a short-lasting electrical impulse which resets the heart and restores normal rhythm. However, it does not improve the pumping capacity of the heart.
In certain types of heart disease, the pumping function of the heart becomes weak and the two lower chambers (= ventricles) do not contract in a coordinated manner. The CRT (C= Cardiac, R= Resynchronization, T= Therapy) device looks very much like the pacemaker, but again, is more bulky. It makes the two ventricles contract in a synchronous manner, and increases the cardiac output in most patients.
There are guidelines for implantation of each of these two devices. Some people will require one device, but not the other. There are still others who require both. We implant a combo device for the latter group of patients. This is known as the CRT-D (C= Cardiac, R= Resynchronization, T= Therapy, D=Defibrillator).
Leadless pacemakers are an important breakthrough. The entire pacemaker is just as big as a vitamin capsule. The doctor has to make a tiny nick below the collar bone and put in a small plastic pipe through which the capsule is delivered to the right ventricle. The capsule attaches itself to the wall of the right ventricle with the help of fine tentacles. The narrow pipe is finally taken out.
One glaring drawback is the fact that the leadless pacemaker paces the lower chamber but not the upper chamber.
General anesthesia is rarely, if ever, employed. We usually administer local anesthesia. We sometimes give an injection to induce light sleep if the patient is unduly apprehensive.
This is a small operation. We employ local anesthesia to make the skin numb before we operate. We make a little cut of
about 4 cm below and parallel to the right or left collar bone and make a pocket between the skin and the underlying muscle.
Most modern pacemakers are cute; they are hardly bigger than a gentleman’s wristwatch. We attach a cable to the right auricle,
and another to the right ventricle. We attach these cables to the pacemaker. The pacemaker is put in the pocket that we have
created, and the skin is stitched up.
I tell them that I have prescribed mild pain killers to alleviate the pain that may have resulted from the operation.
I instruct them to lie flat on their back for 24 hours. They should not turn from side to side or sit up during this period lest their pacing leads get dislodged.
I discharge them approximately 36 hours after the operation. At the time of discharge, I instruct the family members to keep the
surgical site clean and dry for the next two weeks. The patient should avoid excessive shoulder movement such as holding an overhead
rod in a bus or a railway carriage for 30 days. They should perform gentle shoulder exercises after 30 days to avoid developing a frozen
shoulder because of inactivity.
The patient should come to the outpatients’ department after one week for a change of the surgical dressings.
One week after this visit to the outpatients’ department, they should remove the dressings by themselves and take bath with soap and water.
They should avoid bringing a mobile phone or a magnet within 6 inches of the device. For example, if the pacemaker has been
implanted below the left collar bone, they should hold the mobile phone close to their right ear. They should keep about 3 feet apart
from a microwave oven when it is switched on.
There are metal detectors in public places such as airports and metro railway stations. The patients should initially show their pacemaker
warranty card to the security personnel, and request that a physical search be done instead. However if the security staff are adamant, they
can quickly walk through the metal detectors, instead of standing close to them for a long time.
All human beings are killed instantly if they are struck by lightning, whether or not they have pacemakers.
There are no special instructions for pacemaker patients during thunder and lightning.
Patients should follow up with their cardiologist once in every 6 months, or as advised by their doctor.
An ECG should be done during each of these visits. Patients having MRI compatible pacemakers, CRT, CRT-D, and AICD should not undergo the ECG
with magnet. All the rest should do an ECG both with, and without magnet.
Pacemaker interrogation by the technician (= programming) should be done once in every year, or as advised by the cardiologist.
The two important issues that are addressed during the follow up are: is the pacemaker circuit functioning properly, and
is there sufficient battery life left?
The information given in this article is for the general knowledge of the members of the public. This is not intended to be a guideline for treatment by the patients or their doctors. No responsibility will be taken for acts of commission or omission caused by treatment using the information provided here.