Question

HOW CAN WE DISTINGUISH A LEFT ATRIAL ECTOPIC PACEMAKER FROM A SUPERIOR AV JUNCTIONAL
PACEMAKER?

Answer 1

Every normal heartbeat starts with an electrical impulse generated by the heart’s natural pacemaker, the sinus node. and the resultant rhythm is a sinus rhythm.

Normally, electrical impulses generated in your heart stimulate the heart to contract. This moves blood through the heart, to the lungs, allowing oxygenated blood back in, and then forcefully pumps it out to your body and brain.

If the electrical impulses are interrupted for any reason, the heart rate can go too slowly and that may make a pacemaker necessary. Pacemakers are implantable devices that consist of:

· A battery-operated control unit (pulse generator) usually implanted under the skin in the chest area.

· Lead wire(s)that are threaded to the chambers of your heart and attached to the heart muscle that detect the heart rate and deliver small pulses of energy from the pulse generator to the heart.

Pacemakers can help:

· Prevent heart rhythms from going too slowly.

· Coordinate the heart beats so that the top and bottom and left and right chambers beat synchronously. This may help some people with advanced heart failure.

types of pacemakers

There are three basic kinds of pacemakers:

Single chamber. One lead attaches to the upper or lower heart chamber. Used in specific rhythm disorders. A leadless pacemaker is a new technology that is being researched to treat slow heart rhythms without a lead.

Dual chamber. Two leads are used, one for the upper and one for the lower chamber.

Biventricular pacemakers (used in cardiac resynchronization therapy). These use leads attached to three places – the top chamber, and both lower chambers (right and left ventricles).

Pacemakers are designed to keep your heart from going too slowly and this helps your heart to pump more blood to your body

An ectopic pacemaker is an excitable group of cells that causes a premature heart beat outside the normally functioning SA node of the heart. It is thus a cardiac pacemaker that is ectopic, producing an ectopic beat.

Sometimes an ectopic pacemaker sets the pace, if the SA node is damaged or if the electrical conduction system of the heart has problems.

An ectopic pacemaker can reside within a part of the electrical conduction system of the heart, or within the muscle cells of the atria or ventricles. When an ectopic pacemaker initiates a beat, premature contraction occurs. A premature contraction will not follow the normal signal transduction pathway, and can render the heart refractory or incapable of transmitting the normal signal from the SA node. Location of the pacemaker can also change its effect on the SA node and its rhythm.

An ectopic pacemaker located in the atria is known as an atrial pacemaker and can cause the atrial contraction to be faster.

An ectopic pacemaker situated near the AV node and the septum is known as a junctional pacemaker. The pacemaker that is operating in the ventricles is known as the ventricular.

1. left atrial actopic pacemaker:

It is located in atria.

The pacemaker cells are connected to neighboring contractile cells via gap junctions, which enable them to locally depolarize adjacent cells. Gap junctions allow the passage of positive cations from the depolarization of the pacemaker cell to adjacent contractile cells. This starts the depolarization and eventual action potential in contractile cells. Having cardiomyocytes connected via gap junctions allow all contractile cells of the heart to act in a coordinated fashion and contract as a unit. All the while being in sync with the pacemaker cells; this is the property that allows the pacemaker cells to control contraction in all other cardiomyocytes.

Cells in the SA node spontaneously depolarize, ultimately resulting in contraction, approximately 100 times per minute. This native rate is constantly modified by the activity of sympathetic and parasympathetic nerve fibers via the autonomic nervous system, so that the average resting cardiac rate in adult humans is about 70 beats per minute. Because the sinoatrial node is responsible for the rest of the heart's electrical activity, it is sometimes called the primary pacemaker.

2.superior AV junctional pacemaker ( secondary)

It is located in AV node.

If the SA node does not function properly and is unable to control the heart rate, a group of cells further down the heart will become the ectopic pacemaker of the heart. These cells form the Atrioventricular node (or AV node), which is an area between the left atrium and the right ventricle within the atrial septum, will take over the pacemaker responsibility.

The cells of the AV node normally discharge at about 40-60 beats per minute, and are called the secondary pacemaker.