Typification of atrial organization in electrogram recordings

Chapter 1 Introduction 1.0.1 Normal function of the heart The heart is a well-protected muscle found in the thorax and it has four chambers: the upper two chambers are the atria, and the lower two cham- bers are the ventricles. Blood returns to the heart from the body in the superior and inferior ve- nae cavae and flows into the right atrium and then into the adjacent right ventricle. After the ventricle fills, it contracts and pumps the blood to the pulmonary circle; the blood then flows to the left atrium and into the left ventricle that pumps the blood to the rest of the body. The ventricles must deliver enough blood to the body for the body to function normally: an important model describing the heart function was developed by Guyton [1]. According to such a model the total amount of blood that is pumped depends on several factors: • the heart rate; • the average pressure in the right atrium; • the total volume of blood; • vasal compliances and resistances. In order for the heart to pump, it must first receive some sort of electrical stimulation that will cause the muscle to contract. During a normal heart beat, an electrical impulse originates in the right atrium in the sinoatrial (SA) node and travels simultaneously to the left atrium and down the interatrial septum to the atrioventricular (AV) node. The impulse slows down at the AV node and then continues to travel down the His bundle splitting off into the left and right bundle branches, located in both ventricles. The amount 3