Pacemaker Implantation

First-Degree Heart Block: In this the PR segment on the ECG is more than 200ms and all P waves are followed by QRS complexes. The PR interval is similar across the cycles.

Second-Degree Heart Block: This is of 2 types -

Type I (Mobitz I or Wenckebach)

In this the PR segment duration progressively increases with each successive cycle and subsequently the P wave is not followed by a QRS complex.

Type II (Mobitz II)

In this the PR segment duration is prolonged and fixed and after a few cycles the P wave is not followed by the QRS complex.

Third-Degree: (Complete) Heart Block

In this the P wave and QRS complexes are asynchronous i.e. the P waves and QRS complexes occur without any relation to each other. In simpler words the atria and ventricles do not function synchronously.

Usually the Type II second degree AV blocks and the third degree AV blocks usually require permanent pacemaker insertion.

Pacemaker has mainly 2 components

Pocket sized generator which has a battery and the software to detect heart rhythms and subsequently start pacing if there is no intrinsic heart rhythm. This is basically kept under the skin below the patient's collar bone. Leads which are connected at one end to the battery and traverse in the veins of the body to reach the heart chambers. Depending on the different types, there may be single or two leads in the pacemaker.

Different Types of Pacemakers

Single Chamber Pacemaker - In this the pacemaker lead is placed usually in the right lower chamber of the heart (right ventricle). It is usually inserted in patients with atrial fibrillation i.e. abnormal rhythm which does not cause effective contraction and functioning of the upper chambers of the heart, thus no benefit in inserting lead in that position.

Dual Chamber Pacemaker - In this the two pacemaker leads are placed in the right upper and lower chamber (right atria and ventricles). Dual chamber pacemakers are most commonly placed pacemakers.

Rate Responsive Pacemaker - This can be a single or dual chamber pacemaker. Rate responsive means that the pacemaker inherently detects movement of the body and increases the rate of its firing, thus increasing the heart rate to enable the heart to pump more effectively during physical exertion.

Leadless Pacemaker - This is recently introduced in which the pacemaker battery is not implanted under the collar bone. In this a pacemaker which is usually bullet shaped is placed directly in the right ventricle. There are no leads on this device. The battery is directly placed in the heart chambers.

MRI Compatible Pacemaker - Most of the pacemakers presently available in the market have the option of being compatible with MRI, i.e. when the patient needs to undergo MRI at a later date post pacemaker insertion, he can still undergo the same and his treatment may not be hampered.

The basic difference with these 3 devices Pacemaker, CRT & ICD is as follows

Pacemaker functions just to pace the heart chambers if the inherent heart rate is low. ICD in addition to providing pacing options, mainly helps to detect abnormal life threatening heart events and by generating electric shock to correct these rhythms. CRT device, in addition to pacing function, has the main function of enabling synchronised contraction of both the lower chambers of the heart and in this way helps to improve the pumping capacity of the heart.

Two main conditions which require pacemaker implantation are

• Bradyarrhythmias or low heart rate especially Mobitz type II block and complete heart block.
• Tachy brady syndrome (Sick Sinus Syndrome) - i.e. the patient has both slow and fast heart rate, thus will need a permanent pacemaker as a backup for slow heart rate so that medications can be given with ease to treat the fast heart rate.

Diagnostic Tests to Determine Need for a Pacemaker

ECG or electrocardiogram is an important tool to detect slow heart rates. Sometimes if an ECG cannot pick up the slow heart rates, i.e. the heart rate is slow at times but not all the times, then prolonged monitoring of the heart rhythm is done in the form of holter monitoring. This now comes in the form of a small patch attached to your chest which continuously monitors your heart rhythm. This test can be done for a day to a month or more.

Patients need not stay in the hospital for the same, as it can be easily done at your home. If a more prolonged heart rhythm monitoring is needed, then a loop recorder can be used. This is a small pill sized device inserted under the skiing near the breastbone on the chest, which continuously reads the heart rhythm for months, and can at a later date, can be taken out and discarded.

Importance of Consultation with Cardiologists

As explained above, the nuances of detecting heart rhythms, it is imperative to consult your cardiologist if you have a need for a permanent pacemaker, and if yes, which type will be best suited for you and when should you have one.

Pre-procedural Evaluation and Preparation

Usually patients are admitted a day prior or on the day of the procedure. Fasting for around 6 hours is recommended prior to the procedure. Routine blood checks are necessary prior to the procedure.

Pacemaker Implantation Procedure

• Patients are usually awake during the procedure.
• Local anaesthetic is given under the collar bone, usually the left side where a pocket is created to place the battery.
• Through the same place the vein under the collar bone is cannulated to insert the leads which are placed in the heart chambers under fluoroscopy.
• Thereafter the skin is closed with sutures or staplers and the patient is shifted to the ICU.

Recovery and Post Procedural Care

In the ICU patients are observed overnight for abnormal heart rhythms and to look for signs of shortness of breath to rule out any injury to the heart or lungs secondary to the procedure. Once stable, patients are usually discharged in one to two days.

Lifestyle Considerations Post Procedure

Arm care on the side of pacemaker insertion is needed to prevent displacement of the leads. Usually it is recommended to avoid lifting heavy weights and also to lift the arm over the shoulders. Various countries have different rules in terms of driving post pacemaker insertion. It depends on the inherent heart condition as well. Thus it is imperative to ask the cardiologist implanting your device as to when it would be possible to get back to routine activities, including driving your car.

Monitoring and Maintenance of the Pacemaker

Lifelong vigilance of the pacemaker device is necessary. It may need modifying the setting in the pacemaker by the cardiologist or the electrophysiologist implanting the device as per the readings on regular checks.

Early Complications

• Infection at the pocket site or on the leads inserted. To treat this usually a course of prolonged antibiotics is needed.
• Heart injury due to lead insertion is occasionally observed in the form of fluid around the heart (pericardial effusion). This may be life threatening and may need removal of this fluid or a surgeon may be needed to repair the damage made in the heart due to the lead implantation.
• Lung injury due to a puncture site below the collar bone in the form of pneumothorax (air under the lungs). This may need draining of air from the lung space, if causing difficulty in breathing.
• Subcutaneous emphysema (air under the skin) is sometimes also seen. It is usually managed conservatively and only surgeons are called in occasionally to relieve the same.
• Lead displacement can happen in the early weeks of the procedure. To prevent or minimise the chances of it, we ask the patient not to elevate the arm above the shoulders for a month or so.

Late Complications

Infection on the leads due to some secondary infection in the blood leading to infective endocarditis. This may need lead extraction to take the infective source out of the body along with a prolonged course of antibiotics.

Battery depletion - this is not a complication, but once the battery runs out, it needs a redo procedure to replace the battery. The leads are not changed and just the old battery is taken out and replaced with a new one. Thorough knowledge of the disease and its treatment options is essential to make a proper call for deciding what could be the best option for them.