Our heart has specialised tissue known as "Conductive (or electrical) system of the heart" which is responsible for the generation of electrical impulse, its propagation and maintenance of heart rhythm. This system includes sinoatrial (SA) node, atrioventricular (AV) node, bundle of His, right and left buddle branches and Purkinje fibers. Electrical impulse is generated from the SA node, known as natural pacemaker of the heart, at a rate of 60 to 100 beats per minutes. From there the impulse propagates to AV node, then through bundle of His it goes to Purkinje and finally excite the ventricular muscle to contract.

The disease of rhythm are collectively called arrhythmias or dysrhythmias. Diseases of the conductive system involving the SA node, AV node, bundle of His and both its branches give rise to abnormal heart rhythm. Arrhythmias can primarily be divided into two broad groups:

1. Bradyarrhythmias: Disorders with slow heart rhythm

2. Tachyarrhythmias: Disorders with fast heart rhythm

There are many conditions which cause bradyarrhythmias. Among them, complete heart block (failure of electrical impulse propagation from SA node to bundle of His via AV node) and SA nodal dysfunction (including sick sinus syndrome) are the commonest and most important causes of bradyarrhythmia those cause symptoms.

All types of bradyarrhythmias cause almost similar pattern of symptoms such as vertigo, dizziness, feeling of imbalance and fall down (presyncope), sudden unconsciousness (syncope) etc. These symptoms usually occur during exertion. During the episode of presyncope or syncope there are pallor of the face, hands and feet, sweating, coldness of the skin, slow pulse rate and fall of blood pressure.

Bradyarrhythmias are diagnosed by symptoms and signs as mentioned above and by laboratory investigations. Among them, electrocardiography (ECG) and Holter monitoring are most important. In addition, chest X-ray and echocardiography are done to detect associated cardiac diseases. Those patients who develop symptoms during exertion, exercise tolerance test (ETT) is an important tools for diagnosis.

There are some bradyarrhythmias which usually do not cause any symptom. These are detected during routine medical check-up. If the patient does not have any symptoms and is diagnosed incidentally, he or she usually does not require any treatment but one must be alert. The person must consult a cardiologist immediately if he or she develops any symptom. Any type of bradyarrhythmia that causes presyncope or syncope generally requires permanent pacemaker implantation.

A pacemaker is a small electronic device that contains a battery and electronic circuits. It is implanted by a minor surgery under local anesthesia in the upper part of the front of the chest below the collar bone beneath the skin either on either side. If a patient is a right handed person, then it is preferable to put the pacemaker on the left side and vice-versa.

There are several types of pacemakers. Following are commonly used pacemaker types:

1. Single chamber

2. Dual chamber

The pacemaker is connected to the heart chamber(s) by special wires known as lead system. Depending on the type of pacemaker, one or two leads are needed. The type of pacemaker is chosen according to the type of bradyarrhythmia.

After implantation of the pacemaker the patients have to follow the following instructions:

1. The arm on the side where the pacemaker was implanted should not be raised above the head for one month.

2. Should not lift or carry heavy weight by the arm of that side for six months.

3. Should avoid using mobile phone on that side.

4. Should not go close to television or microwave woven.

5. The patient can not undergo MRI examination.

6. One should always tell his or her physician that he or she has pacemaker implanted.

One should come for regular follow-up one month, three months and six months after discharged initially and then continue yearly monitoring of the pacemaker.

The writer is an Assistant Professor of Cardiology at Bangabandh Sheikh Mujib Medical University (BSMMU), Shahbag, Dhaka.