Sudden cardiac death (SCD) is one of the leading causes of mortality in Australia. One of the primary causes of SCD is cardiac dysrhythmias, such as, Ventricular Tachycardia (VT). The most effective treatment for life-threatening cardiac dysrhythmias is defibrillation. This essay will examine the relationship between cardiac activity and the Ventricular Tachycardia (VT) waveform, and discuss how defibrillation may terminate this dysrhythmia, allowing the heart to return to a normal rhythm.
The typical healthy adult heart will have a resting heart rate of between 60 and 100 beats per minute (Saladin, 2011). When the heart beats abnormally fast, it pumps less effectively, which decreases the level of perfusion to the tissue of the body, including the heart itself. This rapid heart rate increases the hearts muscle tissues (myocardium) demand for oxygen, and without intervention, can lead to the death of myocardial cells, which is known as a Myocardial Infarction (MI) (Huazers, 20??).
Each year in Australia approximately 55,000 people suffer a heart attack, or an Acute Myocardial Infarction (AMI). This is equal to 150 heart attacks per day or one in every 10 minutes (Heart Foundation). The Australian Bureau of Statistics reported that over 350,000 Australians will suffer an AMI at some point in their lives (ABS, health survey). In Trappes’ 2012 research article, Trappe notes that there is no single factor that causes an AMI, it is a multifactorial problem, however, approximately ninety percent of AMI’s are caused by tachyarrhythmia’s (Trappe, 2012).
Before one can gain a thorough understanding of dysthymias, it is necessary to develop a fundamental grasp of the heart’s electrical conduction system and the associated physiology and pathophysiology. The primary function of the electrical conduction system is to transmit electrical impulses from the sinoatrial node (SA node) (normal site of conception) down to the atria and ventricles, triggering a contraction of heart muscle (myocardium) and controlling the heart rate. In a normal sinus rhythm, originating from the SA node, there are three phases; atrial depolarisation, ventricular depolarisation and atrial and ventricular repolarisation. The SA node is found within the wall of the right atrium proximal to the entrance of the superior vena cava. Similar to all electrical nodes within the heart, the SA node is composed of pacemaker cells which generate automatic and regular electrical impulses.