Pacemaker implantation

The heart and its blood flow

The heart has its own electrical system that controls the speed and the rhythm of every heartbeat. With each heartbeat, an electrical signal spreads from the top of the heart to the bottom. As it travels, the electrical signal causes the heart to contract in an organized manner and pump blood. 

Electrical signals normally begin in a group of cells called the sinus-atrial (SA) node. As these signals spread from the top to the bottom of the heart, they coordinate the timing of heart cell activity. First, the two upper chambers of the heart, called atria contract. This contraction squeezes blood into the lower chambers of the heart, which are called ventricles. The ventricles then contract and send blood to the rest of the body. The combined contraction of the atria and ventricles is a heartbeat.

An example showing heart block

Sometimes the heart beats too slowly (Bradycardia). During Bradycardia, enough blood is not supplied to the body, due to failure of the hearts chambers to contract properly.This could happen due to SA node not functioning properly, or by a condition called heart block. In this condition, a problem exists with the electrical pathway between the atria and ventricles. Electrical signal sent out by the SA node may not reach the ventricles or is delayed.

Faulty electrical signaling in the heart causes arrhythmias. A pacemaker uses low-energy electrical pulses to correct faulty electrical signaling. Pacemakers can speed up a slow heartbeat.

Pacemakers can also coordinate the electrical signaling between the upper and lower chambers of the heart. The device will make sure the ventricles contract normally if the atria are quivering instead of beating in a normal rhythm (a condition called atrial fibrillation). 

A pacemaker system monitors and treats the abnormal heart rhythm.

Pacemakers can be temporary or permanent.

• Temporary pacemakers are used in emergency settings, or when the underlying cause of the abnormal heart beat is expected to resolve itself.
• They are also used to re-establish a normal heart rhythm until a permanent pacemaker is installed.
• Temporary pacing may be required among heart attack patients, severely symptomatic patients with Bradycardia, patients with Tachycardia, after open-heart surgery and other settings.

A person with a temporary pacemaker will stay in the hospital as long as the pacemaker is in place. Your procedure at Intra refers to a permanent devices, unless your doctor specifically tells you otherwise.

A permanent pacemaker is used when a slow heart rate becomes chronic. A permanent system consists of a pulse generator (also called a device), which is implanted on your chest and one or more leads which is implanted in the chambers of your heart (Atrial or ventricle) and are connected to the device.

Placement of Pacemaker Leads

The Generator

• The generator is a small computer which runs on a battery, safely concealed in the devices case.
• The device continuously monitors your heart functions and delivers electrical energy (charge) to pace your heart when it senses a slow rhythm.
• Together with monitoring your heart rhythm a device can also store information about your heart. Your doctor can then review this information via a computer programme. This helps the doctor better assess the heart rhythm and determined whether the programmed treatment is appropriate. If necessary the device's setting can be changed with the programme.

Pacemaker Device

The Leads

• A pacemaker lead is an insulated wire connected to the pulse generator and implanted in your heart.
• Heart signal is carried via a lead to the pulse generator which then carries energy from the pulse generator back to the heart to coordinate your heart rhythm as the need arises.

Pacemaker Leads

There are two types of pacemakers available: Single chamber and Dual chamber. Your cardiologist will discuss with you which kind of pacemaker is appropriate for you.

Single-chamber Pacemakers
A single chamber pacemaker typically uses one lead placed either in the right atrium or right ventricle to pace the heart. This type of pacemaker is often selected for a person whose SA node sends out signals too slowly.

Dual-chamber Pacemakers
Dual chamber pacemakers typically use two leads, one placed in the right atrium and the second one placed in the right ventricle. The electrical pulses delivered to the heart are timed so that the atria are stimulated to contract just before the ventricles. The timing ensures the atria and the ventricles are beating "in sync" with one another.

A dual chamber pacemaker can be selected for many different reasons. For some, SA node signals are too slow and electrical pathway to the ventricles gets partially or completely blocked. And for others, the timing of the Atria and Ventricle contractions are uncoordinated (asynchronous).