Cardiac arrest is when the heart suddenly and unexpectedly stops beating. It is a medical emergency that without immediate medical intervention will result within minutes in sudden cardiac death. Cardiopulmonary resuscitation (CPR), and possibly defibrillation are needed until further treatment can be provided. Cardiac arrest results in a rapid loss of consciousness, and breathing may be abnormal or absent.While cardiac arrest may be caused by heart attack or heart failure, these are not the same, and in 15 to 25% of cases there is a non-cardiac cause. Some individuals may experience chest pain, shortness of breath, nausea, an elevated heart rate and feeling light-headed immediately before entering cardiac arrest.The most common cause of cardiac arrest is an underlying heart problem like coronary artery disease which decreases the amount of oxygenated blood supplying the heart muscle. This, in turn, damages the structure of the muscle, which can alter its function. These changes can over time cause ventricular fibrillation (V-fib) which most commonly precedes cardiac arrest. Less common causes include major blood loss, lack of oxygen, very low potassium, electrical injury, heart failure, inherited heart arrhythmias and intense physical exercise. Cardiac arrest is diagnosed by the inability to find a pulse.CPR and defibrillation can reverse a cardiac arrest, leading to return of spontaneous circulation, but without such intervention it will prove fatal. In some cases, cardiac arrest is an anticipated outcome of serious illnesses where death is expected. Treatment for cardiac arrest includes immediate CPR and, if a shockable rhythm is present, defibrillation.
: 833  Additionally, individuals with LQTS should avoid certain medications that carry the risk of increasing the severity of this conduction abnormality such as certain anti-arrhythmic, anti-depressant, and quinolone or macrolide antibiotics. Non-cardiac causes
Non-cardiac causes accounts for 15 to 25% of cardiac arrests. The most common non-cardiac causes are trauma, major bleeding (gastrointestinal bleeding, aortic rupture, or intracranial hemorrhage), hypovolemic shock, overdose, drowning, and pulmonary embolism. Cardiac arrest can also be caused by poisoning like the stings of certain jellyfish, or through electrocution, like lightning. Reversible causes
Other non-cardiac causes of cardiac arrest may result from temporary disturbances in the bodies homeostasis. This may be the result from changes in electrolyte ratios, oxygen saturation, or alterations of other ions influencing the bodys pH. Mnemonic for reversible causes
"Hs and Ts" is the name for a mnemonic used to remember the treatable or reversible causes of cardiac arrest. Note: This mnemonic includes causes of cardiac and non-cardiac origin, but all are reversible with appropriate and time-sensitive treatment.