This chapter describes cardiac dysrhythmias and conduction defects. Heart has its own intrinsic system. So, the normal heart produces the electrical impulse in a synchronized and rhythmic manner. When electrical impulse produces, cardiac muscle contract and eject blood into vascular system. Dysrhythmias also called arrhythmias. Cardiac dysrhythmia is a disturbance or irregularity in the conduction function of the heart. It is a problem with rate or rhythm of heartbeat. Dysrhythmias can cause changes in cardiac output, which may leads to hypotension, heart failure and even shock. During arrhythmias the heart can beat too fast, too slow or with an irregular rhythm. The common etiologies of arrhythmias are cardiac disease, sympathetic stimulation, vagal stimulation, electrolyte imbalance and hypoxia.