Why do I need a pacemaker?
Pacemakers are implanted in the body when its heart beat becomes very slow or unreliable. The medical term to describe this condition is a bradyarrhythmia. Brady- means slow, and arrthytmia is any rhythm that the heart gets into that is different than the normal one. To understand why this can happen, we need to look at the heart’s electrical conduction system.
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The conduction system of the heart
The heart is an electrical organ. Electricity in the heart starts in the sinus node, known as the heart’s pacemaker. This structure produces an electrical pulse that travels through tissues to distribute the electricity throughout the heart’s structure, all the way down to the ventricles. The electrical pulse first contracts both top chambers of the heart, then travels to the center of the heart where it slows down to allow for blood flow to catch up. After that, it moves into the ventricles, making them contract and push the blood out into the body and lungs. Problems with the heart’s conduction system can appear along any of its parts and for different reasons. Doctors can have an idea of the location and severity of the problem by looking at the ECG. Conduction abnormalities are named depending on the location where they happen.
The beating of the heart is produced by the heart’s very own pacemaker, located in the right atrium. Think of the pacemaker as both the spark plug that starts the heart’s engine and the conductor of the heart’s rhythm.
The pacemaker is a structure within the heart known as the “sinus node.” It is located in the upper right corner of the heart, which is the cardiac chamber where blood first enters. The sinus node produces a regular electrical pulse that travels down the heart and makes its muscle contract in the rhythmic fashion we all know. The sinus node is controlled by the body’s nervous system, and its pulse can be speeded up or slowed down depending on what the body is doing. You can say the body “drives the heart” through the pacemaker, pushing down on gas pedals and brakes to accelerate it or slow it down. Blood pressure in the body is maintained in part by the heartbeat our pacemaker produces, because without this regular beat, the heart cannot pump blood. If the heart beats very slowly or if the beating becomes unsteady, it can cause an unstable blood pressure situation the body may have trouble adapting to. People who develop severely slow or unsteady heartbeats can feel lightheaded, dizzy, very tired and out of breath, and the condition can also be fatal.
Types of electrical blocks the heart can experience
First degree heart block
Electrical problems that originate at the upper parts of the electrical conduction system create a pattern known as a “first degree block.” The upper parts of the conduction system are made up of the atrium, the atrioventricular node (AV node) and the His-Purkinje system. First degree blocks can be caused by abnormalities in the structure of the atria that prolong the amount of time it takes for the electricity to reach other parts of the heart—for example, if the atrium enlarges in size. Most of the time, this type of pattern is caused by a delay in conduction across the atrioventricular node.
This type of block does not need a pacemaker.
Second degree heart block
Second degree blocks appear at or near the AV node. The AV node is another important part of the heart’s conduction system. It is responsible for slowing down the electrical impulse so the heart can contract in a rhythm. The AV node is called this because it is located at the junction between the atria and the ventricle. Second degree heart blocks cause breaks in the communication between the top and the bottom parts of the conduction system. Different things can cause second degree blocks, including the body’s own nervous system’s effect on the heart and different types of drugs.
An expert is needed to decide if a pacemaker will help with this block
Third degree blocks
This type of block is the most dangerous. Third degree blocks are permanent breaks between the top and the bottom parts of the conduction system. These breaks can happen at the AV node or in the “wires” below it. Without a signal from the top, the bottom parts of the heart usually beat on their own with unpredictable rhythms that originate within the lower parts of the heart. These backup rhythms are known as ventricular or junctional escape rhythms, and are very unreliable. In fact, some patients who develop third degree heart blocks will fail to generate these backup rhythms and die as a result.
This type of block always needs a pacemaker
Sinus node dysfunction
The sinus node itself, known as the main pacemaker of the heart, can fail as a result of a variety of conditions. Its ability to generate an impulse can be either diminished or suppressed. Also, the tissue surrounding the SA node can degenerate resulting in a loss of the signal this pacemaker generates
An expert is needed to decide if a pacemaker will help with this block
What causes cardiac conduction disease?
Many different things cause abnormalities of the conduction system of the heart. Some conduction problems are temporary or treatable, while others are permanent. Let’s review some of the most common causes:
How are conduction problems in the heart treated?
If a specific cause of the conduction problem, like drugs or an infection, is present, removing or treating these can often result in a cure. For permanent conduction problems or those that cause severe symptoms, doctors often recommend an artificial pacemaker.
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