Cardiac Conduction Paper

The cardiac conduction system of the heart consists of specialized muscle cells that generate and send rhythmic electrical impulses to the myocardium in order for the heart to contract (Cardiac Conduction System, 2016). When there is the normal rhythm of the heart it is called sinus rhythm and any deviation from sinus rhythm is called an arrhythmia (Saladin, 2012). Electrocardiograms (ECG) record the electrical impulses and help determine when there are any abnormalities in the way the heart functions (Saladin, 2012). If there is any type of arrhythmia detected there are treatments available to help maintain or correct normal functioning of the heart.
The heart uses methods of contraction (systole) and relaxation (diastole) in order for the
Depolarization of the atria on an ECG can be seen as the P wave (Figure 1). During atrial systole, the blood is pushed through the atrioventricular (AV) valves into the ventricles and the impulse will reach the AV node just shortly after. This slight delay from the SA node to the AV node allows the ventricles to completely fill with blood (Saladin, 2012). The atria will repolarize and remain in diastole until the next impulse is generated. Once the impulse reaches the AV node the impulse will travel down through the AV bundle, located in the interventricular septum, and to the Purkinje fibers to help the ventricles contract. The impulse depolarizes the ventricles and ventricular systole begins (Saladin, 2012). Depolarization of the ventricles can be seen as the QRS complex on an ECG (Figure 1). The pressure in the ventricles increases during ventricular systole causing the blood to push back on the AV valves which causes them to close; this prevents backflow of blood into the atria. When the AV valves close this is when the first heart sound “lubb” can be heard (Saladin, 2012). The increase in ventricular pressure
Ventricular fibrillation is a type of arrhythmia that has no distinguished PQRST waves (Figure 2). During ventricular fibrillation, there are no coordinated contractions produced by the ventricular muscles which mean that the ventricles contract randomly and rapidly (Saladin, 2012). The lack of coordinated contractions causes the ventricles to pump less blood out of the heart causing there to be less blood getting to the lungs and body. Because there is a lack of blood getting to the brain there is a lack of oxygen which can cause a person to become dizzy and eventually lose consciousness. When the heart is deprived of oxygen the heart muscle can begin to die causing angina or chest pain (Staff, 2014). When a person enters ventricular fibrillation treatment must be provided within 1-3 minutes or death can occur. Cardiopulmonary Resuscitation (CPR) is performed to get the blood moving throughout the body so the brain and other organs can receive oxygen (Saladin, 2012). Defibrillation sends several thousand volts of electrical shock to the heart to try and depolarize the myocardium and stop the heart. When using defibrillation all electrical impulses will stop for three to five seconds so a normal sinus rhythm can hopefully begin and ventricular fibrillation will stop (Saladin, 2012). Once a person has suffered from ventricular fibrillation a doctor may recommend an implantable