Harman Patil (Editor)

Cardiac arrest

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Cardiac arrest

cardiopulmonary arrest, circulatory arrest, sudden cardiac arrest (SCA), sudden cardiac death (SCD)

Cardiac arrest is a sudden stop in effective blood flow due to the failure of the heart to contract effectively. Symptoms include loss of consciousness and abnormal or absent breathing. Some people may have chest pain, shortness of breath, or nausea before this occurs. If not treated within minutes, death usually occurs.


The most common cause of cardiac arrest is coronary artery disease. Less common causes include major blood loss, lack of oxygen, very low potassium, heart failure, and intense physical exercise. A number of inherited disorders may also increase the risk including long QT syndrome. The initial heart rhythm is most often ventricular fibrillation. The diagnosis is confirmed by finding no pulse. While a cardiac arrest may be caused by heart attack or heart failure these are not the same.

Prevention includes not smoking, physical activity, and maintaining a healthy weight. Treatment for cardiac arrest is immediate cardiopulmonary resuscitation (CPR) and, if a shockable rhythm is present, defibrillation. Among those who survive targeted temperature management may improve outcomes. An implantable cardiac defibrillator may be placed to reduce the chance of death from recurrence.

In the United States, cardiac arrest outside of hospital occurs in about 13 per 10,000 people per year (326,000 cases). In hospital cardiac arrest occurs in an additional 209,000 Cardiac arrest becomes more common with age. It affects males more often than females. The percentage of people who survive with treatment is about 8%. Many who survive have significant disability. Many U.S. television shows, however, have portrayed unrealistically high survival rates of 67%.

Signs and symptoms

Cardiac arrest is sometimes preceded by certain symptoms such as fainting, fatigue, blackouts, dizziness, chest pain, shortness of breath, weakness, and vomiting. The arrest may also occur with no warning.

When the arrest occurs, the most obvious sign of its occurrence will be the lack of a palpable pulse in the person experiencing it (since the heart has ceased to contract, the usual indications of its contraction such as a pulse will no longer be detectable). Certain types of prompt intervention can often reverse a cardiac arrest, but without such intervention the event will almost always lead to death. In certain cases, it is an expected outcome of a serious illness where death is expected.

Also, as a result of inadequate cerebral perfusion, the patient will quickly become unconscious and will have stopped breathing. The main diagnostic criterion to diagnose a cardiac arrest (as opposed to respiratory arrest which shares many of the same features) is lack of circulation; however, there are a number of ways of determining this. Near-death experiences are reported by 10–20% of people who survived cardiac arrest.


Coronary artery disease is the leading cause of sudden cardiac arrest. Many other cardiac and non-cardiac conditions also increase one's risk.

Coronary artery disease often results in coronary ischemia and ventricular fibrillation (v-fib). Cases have shown that the most common finding at postmortem examination of SCD is chronic high-grade stenosis of at least one segment of a major coronary artery, the arteries that supply the heart muscle with its blood supply. Left ventricular hypertrophy is thought to be the leading cause of sudden cardiac death in the adult population. This is most commonly the result of longstanding high blood pressure which has caused secondary damage to the wall of the main pumping chamber of the heart, the left ventricle.

Although the most frequent cause of sudden cardiac death is ventricular fibrillation, other causes include the following:

  • Coronary heart disease
  • Physical stress
  • low levels of magnesium
  • low levels of potassium
  • major blood loss
  • lack of oxygen
  • severe physical activity which triggers adrenaline
  • Inherited disorders
  • Hypertrophic cardiomyopathy
  • Enlarged heart due to increased blood pressure
  • Commotio cordis
  • Coronary artery disease

    Approximately 60–70% of SCD is related to coronary artery disease, also known as ischemic heart disease. Among adults, it is the predominant cause of arrest, with 30% of people at autopsy showing signs of recent myocardial infarction.

    Non-ischemic heart disease

    A number of non-ischemic cardiac abnormalities can increase the risk of SCD, including cardiomyopathy, cardiac rhythm disturbances, myocarditis, hypertensive heart disease, and congestive heart failure.

    In a group of military recruits aged 18–35, cardiac anomalies accounted for 51% of cases of SCD, while in 35% of cases the cause remained unknown. Underlying pathology included coronary artery abnormalities (61%), myocarditis (20%), and hypertrophic cardiomyopathy (13%). Congestive heart failure increases the risk of SCD fivefold.

    Many additional conduction abnormalities exist that place one at higher risk for cardiac arrest. For instance, long QT syndrome, a condition often mentioned in young people's deaths, occurs in one of every 5000 to 7000 newborns and is estimated to be responsible for 3000 deaths each year compared to the approximately 300,000 cardiac arrests seen by emergency services. These conditions are a fraction of the overall deaths related to cardiac arrest, but represent conditions which may be detected prior to arrest and may be treatable.

    Non-cardiac causes

    About 35% of SCDs are not caused by a heart condition. The most common non-cardiac causes are trauma, bleeding (such as gastrointestinal bleeding, aortic rupture, or intracranial hemorrhage), overdose, drowning and pulmonary embolism. Cardiac arrest can also be caused by poisoning (for example, by the stings of certain jellyfish).

    Risk factors

    The risk factors for SCD are similar to those of coronary artery disease and include smoking, lack of physical exercise, obesity, and diabetes, as well as family history. A prior episode of sudden cardiac arrest also increases the risk of future episodes.

    Mnemonic for causes

    "Hs and Ts" is the name for a mnemonic used to aid in remembering the possible treatable or reversible causes of cardiac arrest.

  • Hypovolemia - A lack of blood volume
  • Hypoxia - A lack of oxygen
  • Hydrogen ions (Acidosis) - An abnormal pH in the body
  • Hyperkalemia or Hypokalemia - Both excess and inadequate potassium can be life-threatening.
  • Hypothermia - A low core body temperature
  • Hypoglycemia or Hyperglycemia - Low or high blood glucose
  • Ts
  • Tablets or Toxins
  • Cardiac Tamponade - Fluid building around the heart
  • Tension pneumothorax - A collapsed lung
  • Thrombosis (Myocardial infarction) - Heart attack
  • Thromboembolism (Pulmonary embolism) - A blood clot in the lung
  • Traumatic cardiac arrest
  • Mechanism

    The mechanism of death in the majority of people dying of sudden cardiac death is ventricular fibrillation. Structural changes in the diseased heart as a result of inherited factors (mutations in ion-channel coding genes for example) cannot explain the suddenness of SCD. Also, sudden cardiac death could be the consequence of electric-mechanical disjunction and bradyarrhythmias.


    Cardiac arrest is synonymous with clinical death.

    A cardiac arrest is usually diagnosed clinically by the absence of a pulse. In many cases lack of carotid pulse is the gold standard for diagnosing cardiac arrest, but lack of a pulse (particularly in the peripheral pulses) may result from other conditions (e.g. shock), or simply an error on the part of the rescuer. Studies have shown that rescuers often make a mistake when checking the carotid pulse in an emergency, whether they are healthcare professionals or lay persons.

    Owing to the inaccuracy in this method of diagnosis, some bodies such as the European Resuscitation Council (ERC) have de-emphasised its importance. The Resuscitation Council (UK), in line with the ERC's recommendations and those of the American Heart Association, have suggested that the technique should be used only by healthcare professionals with specific training and expertise, and even then that it should be viewed in conjunction with other indicators such as agonal respiration.

    Various other methods for detecting circulation have been proposed. Guidelines following the 2000 International Liaison Committee on Resuscitation (ILCOR) recommendations were for rescuers to look for "signs of circulation", but not specifically the pulse. These signs included coughing, gasping, colour, twitching and movement. However, in face of evidence that these guidelines were ineffective, the current recommendation of ILCOR is that cardiac arrest should be diagnosed in all casualties who are unconscious and not breathing normally.


    Clinicians classify cardiac arrest into "shockable" versus "non–shockable", as determined by the ECG rhythm. This refers to whether a particular class of cardiac dysrhythmia is treatable using defibrillation. The two "shockable" rhythms are ventricular fibrillation and pulseless ventricular tachycardia while the two "non–shockable" rhythms are asystole and pulseless electrical activity.


    With positive outcomes following cardiac arrest unlikely, an effort has been spent in finding effective strategies to prevent cardiac arrest. With the prime causes of cardiac arrest being ischemic heart disease, efforts to promote a healthy diet, exercise, and smoking cessation are important. For people at risk of heart disease, measures such as blood pressure control, cholesterol lowering, and other medico-therapeutic interventions are used.[1] A Cochrane review published in 2016 found moderate-quality evidence to show that blood pressure-lowering drugs do not appear to reduce sudden cardiac death.

    Code teams

    In medical parlance, cardiac arrest is referred to as a "code" or a "crash". This typically refers to "code blue" on the hospital emergency codes. A dramatic drop in vital sign measurements is referred to as "coding" or "crashing", though coding is usually used when it results in cardiac arrest, while crashing might not. Treatment for cardiac arrest is sometimes referred to as "calling a code".

    People in general wards often deteriorate for several hours or even days before a cardiac arrest occurs. This has been attributed to a lack of knowledge and skill amongst ward-based staff, in particular a failure to carry out measurement of the respiratory rate, which is often the major predictor of a deterioration and can often change up to 48 hours prior to a cardiac arrest. In response to this, many hospitals now have increased training for ward-based staff. A number of "early warning" systems also exist which aim to quantify the risk which patients are at of deterioration based on their vital signs and thus provide a guide to staff. In addition, specialist staff are being utilised more effectively in order to augment the work already being done at ward level. These include:

  • Crash teams (or code teams) - These are designated staff members with particular expertise in resuscitation who are called to the scene of all arrests within the hospital. This usually involves a specialized cart of equipment (including defibrillator) and drugs called a "crash cart" or "crash trolley".
  • Medical emergency teams - These teams respond to all emergencies, with the aim of treating the people in the acute phase of their illness in order to prevent a cardiac arrest. These teams have been found to decrease the rates of in hospital cardiac arrest and improve survival.
  • Critical care outreach - As well as providing the services of the other two types of team, these teams are also responsible for educating non-specialist staff. In addition, they help to facilitate transfers between intensive care/high dependency units and the general hospital wards. This is particularly important, as many studies have shown that a significant percentage of patients discharged from critical care environments quickly deteriorate and are re-admitted; the outreach team offers support to ward staff to prevent this from happening.
  • In some medical facilities, the resuscitation team may purposely respond slowly to a person in cardiac arrest, a practice known as "slow code", or may fake the response altogether for the sake of the person's family, a practice known as "show code". This is generally done for people for whom performing CPR will have no medical benefit. Such practices are ethically controversial, and are banned in some jurisdictions.

    Implantable cardioverter defibrillators

    A technologically based intervention to prevent further cardiac arrest episodes is the use of an implantable cardioverter-defibrillator (ICD). This device is implanted in the patient and acts as an instant defibrillator in the event of arrhythmia. Note that standalone ICDs do not have any pacemaker functions, but they can be combined with a pacemaker, and modern versions also have advanced features such as anti-tachycardic pacing as well as synchronized cardioversion. A recent study by Birnie et al. at the University of Ottawa Heart Institute has demonstrated that ICDs are underused in both the United States and Canada. An accompanying editorial by Simpson explores some of the economic, geographic, social and political reasons for this. Patients who are most likely to benefit from the placement of an ICD are those with severe ischemic cardiomyopathy (with systolic ejection fractions less than 30%) as demonstrated by the MADIT-II trial.


    Marine-derived omega-3 polyunsaturated fatty acids (PUFAs) has been promoted for the prevention of sudden cardiac death due to its postulated ability to lower triglyceride levels, prevent arrhythmias, decrease platelet aggregation, and lower blood pressure. However, according to a recent systematic review, omega-3 PUFA supplementation are not been associated with a lower risk of sudden cardiac death.


    Sudden cardiac arrest may be treated via attempts at resuscitation. This is usually carried out based upon basic life support (BLS)/advanced cardiac life support (ACLS), pediatric advanced life support (PALS) or neonatal resuscitation program (NRP) guidelines.

    Cardiopulmonary resuscitation

    Cardiopulmonary resuscitation (CPR) is an important part of the management of cardiac arrest. It is recommended that it be started as soon as possible and interrupted as little as possible. The component of CPR that seems to make the greatest difference in most cases is the chest compressions. Correctly performed bystander CPR has been shown to increase survival; however, it is performed in less than 30% of out of hospital arrests as of 2007. If high-quality CPR has not resulted in return of spontaneous circulation and the person's heart rhythm is in asystole, discontinuing CPR and pronouncing the person's death is reasonable after 20 minutes. Exceptions to this include those with hypothermia or who have drowned. Longer durations of CPR may be reasonable in those who have cardiac arrest while in hospital. Bystander CPR, by the lay public, before the arrival of EMS also improves outcomes.

    Either a bag valve mask or an advanced airway may be used to help with breathing. High levels of oxygen are generally given during CPR. Tracheal intubation has not been found to improve survival rates in cardiac arrest and in the prehospital environment may worsen it.

    CPR which involves only chest compressions results in the same outcomes as standard CPR for those who have gone into cardiac arrest due to heart issues. Mechanical chest compressions (as performed by a machine) are no better than chest compressions performed by hand. It is unclear if a few minutes of CPR before defibrillation results in different outcomes than immediate defibrillation. If cardiac arrest occurs after 20 weeks of pregnancy someone should pull or push the uterus to the left during CPR. If a pulse has not returned by four minutes emergency Cesarean section is recommended.


    Defibrillation is indicated if a shockable rhythm is present. The two shockable rhythms are ventricular fibrillation and pulseless ventricular tachycardia. In children 2 to 4 J/Kg is recommended.

    In addition, there is increasing use of public access defibrillation. This involves placing automated external defibrillators in public places, and training staff in these areas how to use them. This allows defibrillation to take place prior to the arrival of emergency services, and has been shown to lead to increased chances of survival. Some defibrillators even provide feedback on the quality of CPR compressions, encouraging the lay rescuer to press the patient's chest hard enough to circulate blood. In addition, it has been shown that those who have arrests in remote locations have worse outcomes following cardiac arrest.


    Medications, while included in guidelines, have not been shown to improve survival to hospital discharge following out-of-hospital cardiac arrest. This includes the use of epinephrine, atropine, lidocaine, and amiodarone. Epinephrine is generally recommended every five minutes. Vasopressin overall does not improve or worsen outcomes compared to epinephrine.

    Epinephrine does appear to improve short-term outcomes such as return of spontaneous circulation. Some of the lack of long-term benefit may be related to delays in epinephrine use. While evidence does not support its use in children guidelines state its use is reasonable. Lidocaine and amiodarone are also deemed reasonable in children with cardiac arrest who have a shockable rhythm. The general use of sodium bicarbonate or calcium is not recommended.

    The 2010 guidelines from the American Heart Association no longer contain the recommendation for using atropine in pulseless electrical activity and asystole due to the lack of evidence for its use. Neither lidocaine nor amiodarone, in those who continue in ventricular tachycardia or ventricular fibrillation despite defibrillation, improves survival to hospital discharge but both equally improve survival to hospital admission.

    Thrombolytics when used generally may cause harm but may be of benefit in those with a confirmed pulmonary embolism as the cause of arrest. Evidence for use of naloxone in those with cardiac arrest due to opioids is unclear but it may still be used. In those with cardiac arrest due to local anesthetic lipid emulsion may be used.

    Targeted temperature management

    Cooling adults after cardiac arrest who have a return of spontaneous circulation (ROSC) but no return of consciousness improves outcomes. This procedure is called targeted temperature management (previously known as therapeutic hypothermia). People are typically cooled for a 24-hour period, with a target temperature of 32–36 °C (90–97 °F). Death rates in the hypothermia group are 35% lower than in those with no temperature management. Complications are generally no greater in those who receive this therapy.

    Earlier versus later cooling may result in better outcomes. A trial that cooled in the ambulance, however, found no difference compared to starting cooling in-hospital. A registry database found poor neurological outcome increased by 8% with each five-minute delay in initiating TH and by 17% for every 30-minute delay in time to target temperature. In children it is unclear if cooling is beneficial however fever should be prevented.

    Do not resuscitate

    Some people choose to avoid aggressive measures at the end of life. A do not resuscitate order (DNR) in the form of an advance health care directive makes it clear that in the event of cardiac arrest, the person does not wish to receive cardiopulmonary resuscitation. Other directives may be made to stipulate the desire for intubation in the event of respiratory failure or, if comfort measures are all that are desired, by stipulating that healthcare providers should "allow natural death".

    Chain of survival

    Several organizations promote the idea of a chain of survival. The chain consists of the following "links":

  • Early recognition - If possible, recognition of illness before the patient develops a cardiac arrest will allow the rescuer to prevent its occurrence. Early recognition that a cardiac arrest has occurred is key to survival - for every minute a patient stays in cardiac arrest, their chances of survival drop by roughly 10%.
  • Early CPR - improves the flow of blood and of oxygen to vital organs, an essential component of treating a cardiac arrest. In particular, by keeping the brain supplied with oxygenated blood, chances of neurological damage are decreased.
  • Early defibrillation - is effective for the management of ventricular fibrillation and pulseless ventricular tachycardia
  • Early advanced care
  • Early post-resuscitation care which may include percutaneous coronary intervention
  • If one or more links in the chain are missing or delayed, then the chances of survival drop significantly.

    These protocols are often initiated by a code blue, which usually denotes impending or acute onset of cardiac arrest or respiratory failure, although in practice, code blue is often called in less life-threatening situations that require immediate attention from a physician.


    Resuscitation with extracorporeal membrane oxygenation devices has been attempted with better results for in-hospital cardiac arrest (29% survival) than out-of-hospital cardiac arrest (4% survival) in populations selected to benefit most. Cardiac catheterization in those who have survived an out-of-hospital cardiac arrest appears to improve outcomes although high quality evidence is lacking. It is recommended that it is done as soon as possible in those who have had a cardiac arrest with ST elevation due to underlying heart problems.

    The precordial thump may be considered in those with witnessed, monitored, unstable ventricular tachycardia (including pulseless VT) if a defibrillator is not immediately ready for use, but it should not delay CPR and shock delivery or be used in those with unwitnessed out of hospital arrest.


    The overall chance of survival among those who have cardiac arrest outside of a hospital is 7.6%. Among children rates of survival is 3 to 16% in North America. For in hospital cardiac arrest survival to discharge is around 22% with many having a good neurological outcome.

    Prognosis is typically assessed 72 hours or more after cardiac arrest. Rates of survival are better in those who someone saw collapse, got bystander CPR, or had either ventricular tachycardia or ventricular fibrillation when assessed. Survival among those with Vfib or Vtach is 15 to 23%. Women are more likely to survive cardiac arrest and leave hospital than men.

    A 1997 review into outcomes following in-hospital cardiac arrest found a survival to discharge of 14% although the range between different studies was 0-28%. In those over the age of 70 who have a cardiac arrest while in hospital, survival to hospital discharge is less than 20%. How well these individuals are able to manage after leaving hospital is not clear.

    A study of survival rates from out-of-hospital cardiac arrest found that 14.6% of those who had received resuscitation by ambulance staff survived as far as admission to hospital. Of these, 59% died during admission, half of these within the first 24 hours, while 46% survived until discharge from hospital. This reflects an overall survival following cardiac arrest of 6.8%. Of these 89% had normal brain function or mild neurological disability, 8.5% had moderate impairment, and 2% had major neurological disability. Of those who were discharged from hospital, 70% were still alive four years later.


    Based on death certificates, sudden cardiac death accounts for about 15% of all death in Western countries. In the United States 326,000 cases of out of hospital and 209,000 cases of in hospital cardiac arrest occur among adults a year. The lifetime risk is three times greater in men (12.3%) than women (4.2%) based on analysis of the Framingham Heart Study. However this gender difference disappeared beyond 85 years of age.

    In the United States during pregnancy cardiac arrest occurs in about one in twelve thousand deliveries or 1.8 per 10,000 live births. Rates are lower in Canada.


    In many publications the stated or implicit meaning of "sudden cardiac death" is sudden death from cardiac causes. However, sometimes physicians call cardiac arrest "sudden cardiac death" even if the person survives. Thus one can hear mentions of "prior episodes of sudden cardiac death" in a living person, which sounds odd as judged by the sense of the term that involves death but is understood as invoking the other sense.


    Cardiac arrest Wikipedia