Arrhythmia Associates LLP

About Arrhythmias - Overview

About Arrhythmias

The Heart as a Pump

The heart has four chambers. On its right side are the right atrium and right ventricle. Venous blood travels through the body's veins to the right atrium and into the right ventricle. When the right ventricle contracts, it sends this venous blood into the lungs where it gives up carbon dioxide and picks up oxygen. The blood then returns from the lungs through vessels to the left atrium, into the left ventricle and from there it is pumped to the body where it delivers its oxygen and nutrients. The top two chambers the atria) contract together, followed by contraction of the bottom two chambers (the ventricles). The left ventricle is the chamber most affected by heart attack and high blood pressure (hypertension), and it is responsible for the generation of the blood pressure your doctor checks with a blood pressure cuff.

The Electrical System of the Heart

The heart's beating is determined by electrical currents which are conducted along nerves imbedded in the walls of the heart. These nerves pass the electrical currents to the heart muscle and stimulate it to contract.

Sinus Node. This is really a collection of special electrical cells located at the top of the right atrium forming the heart's pacemaker. The sinus node governs the rhythmic beating of the heart and the heart rate. Special nerves growing from the sinus node spread its electrical current to the atria which then contract. Finally, electricity spreads not only to the left atrium but also to the only electrical connection between the atria on top and the ventricles on the bottom of the heart, the atrio-ventricular node.

Atrio-Ventricular Node. This is the nerve, which electrically connects the atria with the ventricles. It ordinarily is the only means to spread electricity from the atrium to the lower chambers (the ventricles).

Left and Right Bundle Branches. The atrio-ventricular (AV) node unites the atria with the ventricles by communicating with the right and left bundle branches. These are specialized nerve fibers capable of conducting electricity at a rapid rate and their activity causes the muscle of the ventricles to contract.

Arrhythmia Mechanisms

Cardiac arrhythmias are either the result of an increase in the automatic pacemaker activity (increased automaticity) of any of the nerve fibers or cells in the heart or the result of a short circuit and redirection of electrical conduction (reentry).

An example of an increase in automatic activity is the normal increase in heart rate originating from the sinus node when we perform exercise. This is not strictly speaking an arrhythmia but occasionally there exists a similar behavior of abnormal cells acting like the sinus node taking over the sinus node and all other cells at a faster rate at times when rapid rates are not appropriate or needed, e.g., at rest. Reentry occurs when there are two nerves in parallel within the area so that instead of passing through the area, electricity passes repetitively down one nerve and back up the other within the same area.

What is Arrhythmia?

An arrhythmia is an abnormal heart rhythm. These arrhythmias may describe when the heart beats too slowly, too rapidly, or in an irregular pattern. The different types of arrhythmias can occur in different areas of the heart (atria or ventricles) and by what happen to the heart's rhythm when they occur. Arrhythmias arising in the atria are described as atrial or supraventricular (above the ventricles). Arrhythmias originating in the ventricles are generally the most serious type of abnormal heart rhythm.

Arrhythmias are classified based on the presence or absence of heart disease. Arrhythmias can indicate the presence of heart disease also symptoms from arrhythmia can be disabling and affect the quality of one's life.