Cardiac arrest is caused by a sudden stop of mechanical function of the heart. Cessation of cardiac function leads to decreased tissue perfusion that can cause fatal outcomes if not reversed. Cardiac arrest is clinically defined by unconsciousness, apnea or agonal breathing, and impalpable central pulse. Early recognition of an ongoing cardiac arrest is crucial since chances for neurologically intact survival decrease substantially as time passes without an appropriate intervention. Resuscitation efforts are directed toward advanced life support and correction of reversible causes of arrest. Advanced life support consists of several steps that are described by the ABC mnemonic. The letter A stands for checking the patency of the airway, B for checking appropriate breathing, and C for circulation. Vulnerability or immediate danger to any of these vital functions should be promptly dealt with, using available methods of airway management in order to provide appropriate ventilation and oxygenation. Tissue perfusion should be maintained by performing high quality chest compressions. Advanced life support also includes availability of a defibrillator, which can be used for rhythm assessment and early defibrillation if indicated. Depending on the recorded rhythm we differentiate between those rhythms that will respond to defibrillation attempts (ventricular fibrillation and pulseless ventricular tachycardia) and those that will not (pulseless electrical activity and asystole). During the cardiopulmonary resuscitation it is extremely important to mentally go through differential diagnoses of possibly reversible causes of arrest since their correction greatly increases reversal of cardiac arrest and survival. Those reversible causes are clinically referred to as 4H and 4T for easier recollection. The 4Hs include hypoxia, hypovolemia, hyperkalemia and hypokalemia, and hypothermia. The 4Ts include thrombosis (coronary thrombosis and pulmonary embolism), tamponade, tension pneumothorax, and toxins.