Cardiac arrest
Overview
 
Cardiac arrest, is the cessation of normal circulation
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...

 of the blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

 due to failure of the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

 to contract effectively. Medical personnel can refer to an unexpected cardiac arrest as a sudden cardiac arrest or SCA.

A cardiac arrest is different from (but may be caused by) a heart attack
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...

, where blood flow to the muscle of the heart is impaired.

Arrested blood circulation
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...

 prevents delivery of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 to the body.
Encyclopedia
Cardiac arrest, is the cessation of normal circulation
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...

 of the blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

 due to failure of the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

 to contract effectively. Medical personnel can refer to an unexpected cardiac arrest as a sudden cardiac arrest or SCA.

A cardiac arrest is different from (but may be caused by) a heart attack
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...

, where blood flow to the muscle of the heart is impaired.

Arrested blood circulation
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...

 prevents delivery of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 to the body. Lack of oxygen to the brain causes loss of consciousness
Unconsciousness
Unconsciousness is the condition of being not conscious—in a mental state that involves complete or near-complete lack of responsiveness to people and other environmental stimuli. Being in a comatose state or coma is a type of unconsciousness. Fainting due to a drop in blood pressure and a...

, which then results in abnormal or absent breathing
Respiratory arrest
Respiratory arrest is the cessation of breathing. It is a medical emergency and it usually is related to or coincides with a cardiac arrest. Causes include opiate overdose, head injury, anaesthesia, tetanus, or drowning...

. Brain injury is likely if cardiac arrest goes untreated for more than five minutes. For the best chance of survival and neurological recovery, immediate and decisive treatment is imperative.

Cardiac arrest is a medical emergency
Medical emergency
A medical emergency is an injury or illness that is acute and poses an immediate risk to a person's life or long term health. These emergencies may require assistance from another person, who should ideally be suitably qualified to do so, although some of these emergencies can be dealt with by the...

 that, in certain situations, is potentially reversible if treated early. When unexpected cardiac arrest leads to death this is called sudden cardiac death
Sudden Cardiac Death
Sudden cardiac death is natural death from cardiac causes, heralded by abrupt loss of consciousness within one hour of the onset of acute symptoms. Other forms of sudden death may be noncardiac in origin...

 (SCD). The treatment for cardiac arrest is cardiopulmonary resuscitation
Cardiopulmonary resuscitation
Cardiopulmonary resuscitation is an emergency procedure which is performed in an effort to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person in cardiac arrest. It is indicated in those who are unresponsive...

 (CPR) to provide circulatory support, followed by defibrillation
Defibrillation
Defibrillation is a common treatment for life-threatening cardiac arrhythmias, ventricular fibrillation and pulseless ventricular tachycardia. Defibrillation consists of delivering a therapeutic dose of electrical energy to the affected heart with a device called a defibrillator...

 if a shockable rhythm is present. If a shockable rhythm is not present after CPR and other interventions, clinical death is inevitable.

Classification

Cardiac arrest is classified into "shockable" versus "non–shockable", based upon the ECG
Electrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...

 rhythm. The two shockable rhythms are ventricular fibrillation
Ventricular fibrillation
Ventricular fibrillation is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them quiver rather than contract properly. Ventricular fibrillation is a medical emergency and most commonly identified arrythmia in cardiac arrest...

 and pulseless ventricular tachycardia while the two non–shockable rhythms are asystole
Asystole
In medicine, asystole is a state of no cardiac electrical activity, hence no contractions of the myocardium and no cardiac output or blood flow...

 and pulseless electrical activity
Pulseless electrical activity
Pulseless electrical activity or PEA refers a cardiac arrest situation in which a heart rhythm is observed on the electrocardiogram that should be producing a pulse, but is not...

. This refers to whether a particular class of disrhythmia is treatable using defibrillation
Defibrillation
Defibrillation is a common treatment for life-threatening cardiac arrhythmias, ventricular fibrillation and pulseless ventricular tachycardia. Defibrillation consists of delivering a therapeutic dose of electrical energy to the affected heart with a device called a defibrillator...

.

Signs and symptoms

Cardiac arrest is an abrupt cessation of pump function in the heart (as evidenced by the absence of a palpable pulse). Prompt intervention can usually reverse a cardiac arrest, but without such intervention it will almost always lead to death. In certain cases, it is an expected outcome to a serious illness.

However, due to inadequate cerebral perfusion
Cerebral circulation
Cerebral circulation refers to the movement of blood through the network of blood vessels supplying the brain. The arteries deliver oxygenated blood, glucose and other nutrients to the brain and the veins carry deoxygenated blood back to the heart, removing carbon dioxide, lactic acid, and other...

, the patient will be unconscious
Unconsciousness
Unconsciousness is the condition of being not conscious—in a mental state that involves complete or near-complete lack of responsiveness to people and other environmental stimuli. Being in a comatose state or coma is a type of unconsciousness. Fainting due to a drop in blood pressure and a...

 and will have stopped breathing. The main diagnostic criterion to diagnose a cardiac arrest, (as opposed to respiratory arrest
Respiratory arrest
Respiratory arrest is the cessation of breathing. It is a medical emergency and it usually is related to or coincides with a cardiac arrest. Causes include opiate overdose, head injury, anaesthesia, tetanus, or drowning...

 which shares many of the same features), is lack of circulation
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...

, however there are a number of ways of determining this. Near death experiences are reported by 10-20% of people who survived cardiac arrest.

Causes

Coronary heart disease is the leading cause of sudden cardiac arrest. Many other cardiac and non–cardiac conditions also increase ones risk.

Coronary heart disease

Approximately 60–70% of SCD is related to coronary heart disease
Coronary heart disease
Coronary artery disease is the end result of the accumulation of atheromatous plaques within the walls of the coronary arteries that supply the myocardium with oxygen and nutrients. It is sometimes also called coronary heart disease...

. Among adults, ischemic heart disease is the predominant cause of arrest with 30% of people at autopsy
Autopsy
An autopsy—also known as a post-mortem examination, necropsy , autopsia cadaverum, or obduction—is a highly specialized surgical procedure that consists of a thorough examination of a corpse to determine the cause and manner of death and to evaluate any disease or injury that may be present...

 showing signs of recent myocardial infarction
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...

.

Non ischemic heart disease

A number of other cardiac abnormalities can increase the risk of SCD including: cardiomyopathy
Cardiomyopathy
Cardiomyopathy, which literally means "heart muscle disease," is the deterioration of the function of the myocardium for any reason. People with cardiomyopathy are often at risk of arrhythmia or sudden cardiac death or both. Cardiomyopathy can often go undetected, making it especially dangerous to...

, cardiac rhythm disturbances
Cardiac dysrhythmia
Cardiac dysrhythmia is any of a large and heterogeneous group of conditions in which there is abnormal electrical activity in the heart. The heart beat may be too fast or too slow, and may be regular or irregular.Some arrhythmias are life-threatening medical emergencies that can result in cardiac...

, hypertensive heart disease
Hypertensive heart disease
Hypertensive heart disease is any of a number of complications of arterial hypertension that affects the heart.-Symptoms:* Fatigue* Cardiomegaly* Irregular pulse* Swelling of feet* Weight gain* Nausea* Shortness of breath...

, congestive heart failure
Congestive heart failure
Heart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...

.

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
Coronary artery anomaly
Coronary artery anomalies are congenital abnormalities in the coronary anatomy of the heart. By definition, these abnormalities are variants of anatomy occurring in less than 1% of the general population. They are often found in combination with other congenital heart defects...

 (61%), myocarditis
Myocarditis
Myocarditis is inflammation of heart muscle . It resembles a heart attack but coronary arteries are not blocked.Myocarditis is most often due to infection by common viruses, such as parvovirus B19, less commonly non-viral pathogens such as Borrelia burgdorferi or Trypanosoma cruzi, or as a...

 (20%), and hypertrophic cardiomyopathy
Hypertrophic cardiomyopathy
Hypertrophic cardiomyopathy is a disease of the myocardium in which a portion of the myocardium is hypertrophied without any obvious cause...

 (13%). Congestive heart failure increases the risk of SCD by 5 fold.

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 1/5000-1/7000 newborns and is estimated to be responsible 3000 deaths each year compared to the approximately 300000 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, which maybe treatable.

Non–cardiac

SCDs is unrelated to heart problems in 35% of cases. The most common non–cardiac causes: trauma
Physical trauma
Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...

, non-trauma related bleeding (such as gastrointestinal bleeding
Gastrointestinal bleeding
Gastrointestinal bleeding or gastrointestinal hemorrhage describes every form of hemorrhage in the gastrointestinal tract, from the pharynx to the rectum. It has diverse causes, and a medical history, as well as physical examination, generally distinguishes between the main forms...

, aortic rupture, and intracranial hemorrhage
Intracranial hemorrhage
An intracranial hemorrhage is a hemorrhage, or bleeding, within the skull.-Causes:Intracranial bleeding occurs when a blood vessel within the skull is ruptured or leaks. It can result from physical trauma or nontraumatic causes such as a ruptured aneurysm...

), overdose, drowning
Drowning
Drowning is death from asphyxia due to suffocation caused by water entering the lungs and preventing the absorption of oxygen leading to cerebral hypoxia....

 and pulmonary embolism
Pulmonary embolism
Pulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...

.

Risk factors

The risk factors for SCD are similar to those seen with coronary heart disease including: smoking
Smoking
Smoking is a practice in which a substance, most commonly tobacco or cannabis, is burned and the smoke is tasted or inhaled. This is primarily practised as a route of administration for recreational drug use, as combustion releases the active substances in drugs such as nicotine and makes them...

, lack of physical exercise
Physical exercise
Physical exercise is any bodily activity that enhances or maintains physical fitness and overall health and wellness. It is performed for various reasons including strengthening muscles and the cardiovascular system, honing athletic skills, weight loss or maintenance, as well as for the purpose of...

, obesity
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...

, diabetes, and family history
Family history
Family history is the systematic narrative and research of past events relating to a specific family, or specific families.- Introduction :...

.

Hs and Ts

"Hs and Ts" is the name for a mnemonic used to aid in remembering the possible treatable or reversible causes of cardiac arrest.
Hs
  • Hypovolemia
    Hypovolemia
    In physiology and medicine, hypovolemia is a state of decreased blood volume; more specifically, decrease in volume of blood plasma...

     - A lack of blood volume
  • Hypoxia
    Hypoxia (medical)
    Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...

     - A lack of oxygen
    Oxygen
    Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

  • Hydrogen
    Hydrogen
    Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

     ions (Acidosis
    Acidosis
    Acidosis is an increased acidity in the blood and other body tissue . If not further qualified, it usually refers to acidity of the blood plasma....

    ) - An abnormal pH in the body
  • Hyperkalemia
    Hyperkalemia
    Hyperkalemia refers to the condition in which the concentration of the electrolyte potassium in the blood is elevated...

     or Hypokalemia
    Hypokalemia
    Hypokalemia or hypokalaemia , also hypopotassemia or hypopotassaemia , refers to the condition in which the concentration of potassium in the blood is low...

     - Both excess and inadequate potassium can be life-threatening.
  • Hypothermia
    Hypothermia
    Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...

     - A low core body temperature
  • Hypoglycemia
    Hypoglycemia
    Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...

     or Hyperglycemia
    Hyperglycemia
    Hyperglycemia or Hyperglycæmia, or high blood sugar, is a condition in which an excessive amount of glucose circulates in the blood plasma. This is generally a glucose level higher than 13.5mmol/l , but symptoms may not start to become noticeable until even higher values such as 15-20 mmol/l...

     - Low or high blood glucose


Ts
  • Tablets or Toxins
  • Cardiac Tamponade
    Cardiac tamponade
    Cardiac tamponade, also known as pericardial tamponade, is an emergency condition in which fluid accumulates in the pericardium ....

     - Fluid building around the heart
  • Tension pneumothorax - A collapsed lung
  • Thrombosis
    Thrombosis
    Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...

     (Myocardial infarction
    Myocardial infarction
    Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...

    ) - Heart attack
  • Thromboembolism
    Thrombosis
    Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...

     (Pulmonary embolism
    Pulmonary embolism
    Pulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...

    ) - A blood clot in the lung
  • Trauma
    Physical trauma
    Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...


Diagnosis

Cardiac arrest is synonymous with clinical death
Clinical death
Clinical death is the medical term for cessation of blood circulation and breathing, the two necessary criteria to sustain life. It occurs when the heart stops beating in a regular rhythm, a condition called cardiac arrest. The term is also sometimes used in resuscitation research.Stopped blood...

.

A cardiac arrest is usually diagnosed clinically by the absence of a pulse. In many cases lack of carotid pulse
Pulse
In medicine, one's pulse represents the tactile arterial palpation of the heartbeat by trained fingertips. The pulse may be palpated in any place that allows an artery to be compressed against a bone, such as at the neck , at the wrist , behind the knee , on the inside of the elbow , and near the...

 is the gold standard
Gold standard (test)
In medicine and statistics, gold standard test refers to a diagnostic test or benchmark that is the best available under reasonable conditions. It does not have to be necessarily the best possible test for the condition in absolute terms...

 for diagnosing cardiac arrest, but lack of a pulse (particularly in the peripheral pulses) may be a result of 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
Agonal respiration
Agonal respiration is an abnormal pattern of breathing characterized by gasping, labored breathing, accompanied by strange vocalizations and myoclonus. Possible causes include cerebral ischemia, extreme hypoxia or even anoxia...

.

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.

Prevention

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
Healthy diet
A healthy diet is one that helps maintain or improve general health. It is important for lowering many chronic health risks, such as obesity, heart disease, diabetes, hypertension and cancer. A healthy diet involves consuming appropriate amounts of all essential nutrients and an adequate amount of...

, exercise, and smoking cessation
Smoking cessation
Smoking cessation is the process of discontinuing the practice of inhaling a smoked substance. This article focuses exclusively on cessation of tobacco smoking; however, the methods described may apply to cessation of smoking other substances that can be difficult to stop using due to the...

 are important. For people at risk of heart disease, measures such as blood pressure
Blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...

 control, cholesterol
Cholesterol
Cholesterol is a complex isoprenoid. Specifically, it is a waxy steroid of fat that is produced in the liver or intestines. It is used to produce hormones and cell membranes and is transported in the blood plasma of all mammals. It is an essential structural component of mammalian cell membranes...

 lowering, and other medico-therapeutic interventions are used.

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
Hospital emergency codes
Hospital Emergency Codes are used in hospitals worldwide to alert staff to various emergency situations. The use of codes is intended to convey essential information quickly and with a minimum of misunderstanding to staff, while preventing stress or panic among visitors to the hospital...

. 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".

Extensive research has shown that patients 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
Respiratory rate
Respiratory rate is also known by respiration rate, pulmonary ventilation rate, ventilation rate, or breathing frequency is the number of breaths taken within a set amount of time, typically 60 seconds....

, 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
Vital signs
Vital signs are measures of various physiological statistics, often taken by health professionals, in order to assess the most basic body functions. Vital signs are an essential part of a case presentation. The act of taking vital signs normally entails recording body temperature, pulse rate ,...

 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 who have 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
    Defibrillation
    Defibrillation is a common treatment for life-threatening cardiac arrhythmias, ventricular fibrillation and pulseless ventricular tachycardia. Defibrillation consists of delivering a therapeutic dose of electrical energy to the affected heart with a device called a defibrillator...

    ) and drugs called a "crash cart".
  • Medical emergency teams - These teams respond to all emergencies, with the aim of treating the patient in the acute phase of their illness in order to prevent a cardiac arrest.
  • 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
    Intensive Care Unit
    thumb|220px|ICU roomAn intensive-care unit , critical-care unit , intensive-therapy unit/intensive-treatment unit is a specialized department in a hospital that provides intensive-care medicine...

     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.

Implantable cardioverter defibrillators

A technologically based intervention to prevent further cardiac arrest episodes is the use of an implantable cardioverter-defibrillator
Implantable cardioverter-defibrillator
An implantable cardioverter-defibrillator is a small battery-powered electrical impulse generator which is implanted in patients who are at risk of sudden cardiac death due to ventricular fibrillation and ventricular tachycardia. The device is programmed to detect cardiac arrhythmia and correct it...

 (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
Pacemaker
An artificial pacemaker is a medical device that uses electrical impulses to regulate the beating of the heart.Pacemaker may also refer to:-Medicine:...

, and modern versions also have advanced features such as anti-tachycardic pacing as well as synchronized cardioversion
Cardioversion
Cardioversion is a medical procedure by which an abnormally fast heart rate or cardiac arrhythmia is converted to a normal rhythm, using electricity or drugs. Synchronized electrical cardioversion uses a therapeutic dose of electric current to the heart, at a specific moment in the cardiac cycle...

. 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.

Management

Sudden cardiac arrest may be treated via attempts at resuscitation. This is usually carried out based upon basic life support
Basic life support
Basic life support is the level of medical care which is used for patients with life-threatening illnesses or injuries until the patient can be given full medical care at a hospital. It can be provided by trained medical personnel, including emergency medical technicians, paramedics, and by...

 (BLS) / advanced cardiac life support
Advanced cardiac life support
Advanced cardiac life support or Advanced Cardiovascular Life Support refers to a set of clinical interventions for the urgent treatment of cardiac arrest and other life threatening medical emergencies, as well as the knowledge and skills to deploy those interventions.Extensive medical knowledge...

 (ACLS), pediatric advanced life support
Pediatric Advanced Life Support
Pediatric Advanced Life Support is a 2 day American Heart Association training program. The goal of the course is to aid the pediatric healthcare provider in developing the knowledge and skills necessary to efficiently and effectively manage critically ill infants and children, resulting in...

 (PALS) or neonatal resuscitation program
Neonatal Resuscitation Program
The Neonatal Resuscitation Program was developed and is currently maintained by the American Academy of Pediatrics. This program focuses on the teaching and maintaining basic skills for the resuscitation of neonates. NRP's didactic portion includes nine lessons modules along with 5 skills...

 (NRP) guidelines.
Several organisations promote the idea of a "chain of survival
Chain of survival
The chain of survival refers to a series of actions that, when put into motion, reduce the mortality associated with cardiac arrest. Like any chain, the chain of survival is only as strong as its weakest link...

". 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
    Ventricular fibrillation
    Ventricular fibrillation is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them quiver rather than contract properly. Ventricular fibrillation is a medical emergency and most commonly identified arrythmia in cardiac arrest...

     and pulseless ventricular tachycardia
    Ventricular tachycardia
    Ventricular tachycardia is a tachycardia, or fast heart rhythm, that originates in one of the ventricles of the heart...

      If defibrillation is delayed the rhythm is likely to degenerate into asystole
    Asystole
    In medicine, asystole is a state of no cardiac electrical activity, hence no contractions of the myocardium and no cardiac output or blood flow...

     for which outcomes are worse.
  • Early advanced care - Early Advanced Cardiac Life Support
    Advanced cardiac life support
    Advanced cardiac life support or Advanced Cardiovascular Life Support refers to a set of clinical interventions for the urgent treatment of cardiac arrest and other life threatening medical emergencies, as well as the knowledge and skills to deploy those interventions.Extensive medical knowledge...

     is the final link in the chain of survival.


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
Respiratory failure
The term respiratory failure, in medicine, is used to describe inadequate gas exchange by the respiratory system, with the result that arterial oxygen and/or carbon dioxide levels cannot be maintained within their normal ranges. A drop in blood oxygenation is known as hypoxemia; a rise in arterial...

, although in practice, Code Blue is often called in less life-threatening situations that require immediate attention from a physician.

Cardiopulmonary resuscitation

CPR is a critical part of the management of cardiac arrest. It should be started as soon as possible and interrupted as little as possible. The component of CPR which seems to make the greatest difference is the chest compressions. Tracheal intubation
Tracheal intubation
Tracheal intubation, usually simply referred to as intubation, is the placement of a flexible plastic or rubber tube into the trachea to maintain an open airway or to serve as a conduit through which to administer certain drugs...

 has not been found to improve survival rates in cardiac arrest cases. A 2009 study has found that assisted ventilation may worsen outcomes over placement of an oral airway with passive oxygen delivery. Intubation in the prehospital environment has been found to decrease survival. Correctly performed bystander CPR has been shown to increase survival; it is performed in less than 30% of out of hospital arrests.

Defibrillation

Shockable and non–shockable causes of cardiac arrest is based on the presence or absence of ventricular fibrillation
Ventricular fibrillation
Ventricular fibrillation is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them quiver rather than contract properly. Ventricular fibrillation is a medical emergency and most commonly identified arrythmia in cardiac arrest...

 or pulseless ventricular tachycardia. The shockable rhythms are treated with CPR and defibrillation.

In addition, there is increasing use of public access defibrillation. This involves placing automated external defibrillator
Automated external defibrillator
An automated external defibrillator or AED is a portable electronic device that automatically diagnoses the potentially life threatening cardiac arrhythmias of ventricular fibrillation and ventricular tachycardia in a patient, and is able to treat them through defibrillation, the application of...

s 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 suffer arrests in remote locations have worse outcomes following cardiac arrest: these areas often have first responders, whereby members of the community receive training in resuscitation and are given a defibrillator, and called by the emergency medical services in the case of a collapse in their local area.

Medications

Medications, while included in guidelines, have been shown not to improve survival to hospital discharge post out of hospital cardiac arrest. This includes the use of epinephrine
Epinephrine
Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...

, atropine
Atropine
Atropine is a naturally occurring tropane alkaloid extracted from deadly nightshade , Jimson weed , mandrake and other plants of the family Solanaceae. It is a secondary metabolite of these plants and serves as a drug with a wide variety of effects...

, and amiodarone
Amiodarone
Amiodarone is an antiarrhythmic agent used for various types of tachyarrhythmias , both ventricular and supraventricular arrhythmias. Discovered in 1961, it was not approved for use in the United States until 1985...

. Epinephrine does however increase return of spontaneous circulation
Return of spontaneous circulation
Return of spontaneous circulation is resumption of sustained perfusing cardiac activity associated with significant respiratory effort after cardiac arrest. Signs of ROSC include breathing, coughing, or movement and a palpable pulse or a measurable blood pressure...

 and there is a none significant trend towards improvement in long term survival. The 2010 guidelines, from the American Heart Association
American Heart Association
The American Heart Association is a non-profit organization in the United States that fosters appropriate cardiac care in an effort to reduce disability and deaths caused by cardiovascular disease and stroke. It is headquartered in Dallas, Texas...

 has removed its recommendation for using atropine in pulseless electrical activity
Pulseless electrical activity
Pulseless electrical activity or PEA refers a cardiac arrest situation in which a heart rhythm is observed on the electrocardiogram that should be producing a pulse, but is not...

 and asystole
Asystole
In medicine, asystole is a state of no cardiac electrical activity, hence no contractions of the myocardium and no cardiac output or blood flow...

.

Therapeutic hypothermia

Cooling a person after cardiac arrest with return of spontaneous circulation (ROSC) but without return of consciousness improves outcomes. This procedure is called therapeutic hypothermia
Therapeutic hypothermia
Therapeutic hypothermia, also known as protective hypothermia, is a medical treatment that lowers a patient's body temperature in order to help reduce the risk of the ischemic injury to tissue following a period of insufficient blood flow. Periods of insufficient blood flow may be due to cardiac...

. The first study conducted in Europe focused on people who were resuscitated 5–15 minutes after collapse. Patients participating in this study experienced spontaneous return of circulation (ROSC) after an average of 105 minutes. Subjects were then cooled over a 24 hour period, with a target temperature of 32–34 °C (89.6–93.2 F). 55% of the 137 patients in the hypothermia group experienced favorable outcomes, compared with only 39% in the group that received standard care following resuscitation. Death rates in the hypothermia group were 14% lower, meaning that for every 7 patients treated one life was saved. Notably, complications between the two groups did not differ substantially. This data was supported by another similarly run study that took place simultaneously in Australia. In this study 49% of the patients treated with hypothermia following cardiac arrest experienced good outcomes, compared to only 26% of those who received standard care.

Other

The precordial thump
Precordial thump
The precordial thump is a medical procedure that may used by healthcare professionals, to respond to ventricular fibrillation or ventricular tachycardia under certain conditions. The procedure is outside the scope of first-aid treatment and requires, at minimum, training in advanced cardiac life...

 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.

Sporadic reports of resuscitation with extracorporeal membrane oxygenation
Extracorporeal membrane oxygenation
In intensive care medicine, extracorporeal membrane oxygenation is an extracorporeal technique of providing both cardiac and respiratory support oxygen to patients whose heart and lungs are so severely diseased or damaged that they can no longer serve their function...

 devices have appeared in recent years.

Prognosis

Out-of-hospital cardiac arrest (OHCA) has a worse survival rate (2-8% for discharge and 8-22% for admission), than an in-hospital cardiac arrest (15% for discharge). The principal determining factor is the initially documented rhythm. People with ventricular fibrillation
Ventricular fibrillation
Ventricular fibrillation is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them quiver rather than contract properly. Ventricular fibrillation is a medical emergency and most commonly identified arrythmia in cardiac arrest...

 or pulseless ventricular tachycardia have 10-15 times greater chance of surviving than those suffering from pulseless electrical activity
Pulseless electrical activity
Pulseless electrical activity or PEA refers a cardiac arrest situation in which a heart rhythm is observed on the electrocardiogram that should be producing a pulse, but is not...

 or asystole
Asystole
In medicine, asystole is a state of no cardiac electrical activity, hence no contractions of the myocardium and no cardiac output or blood flow...

.

Since mortality in case of OHCA is high, programs were developed to improve survival rate. Although mortality in case of ventricular fibrillation is high, rapid intervention with a defibrillator increases survival rate.

Survival is mostly related to the cause of the arrest (see above). In particular, patients who have suffered hypothermia
Hypothermia
Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...

 have an increased survival rate, possibly because the cold protects the vital organs from the effects of tissue hypoxia. Survival rates following an arrest induced by toxins is very much dependent on identifying the toxin and administering an appropriate antidote. A patient who has suffered a myocardial infarction
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...

 due to a blood clot in the left coronary artery
Left coronary artery
The left coronary artery, abbreviated LCA and also known as the left main coronary artery , arises from the aorta above the left cusp of the aortic valve.-Branching:...

 has a lower chance of survival.

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 gives us 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% suffered major neurological disability. Of those who were discharged from hospital, 70% were still alive 4 years later.

A specific pattern of the brain damage in cardiac arrest survivors revealed by MRI study has been known as a delayed T1-hyperintensity localized in the striatum, cerebral cortex, thalamus, and/or substantia nigra (Fujioka, M. et al. Stroke. 1994;25:2091-2095.; Fujioka, M. et al. Neuroradiology. 1994;36:605-607.). The MRI volumetric study demonstrated that the human hippocampus showed its selective atrophy in a delayed fashion after cardiopulmonary resuscitation (Fujioka, M. et al. Cerebrovasc Dis. 2000;10:2-7.).

A review into prognosis following in-hospital cardiac arrest found a survival to discharge of 14% although the range between different studies was 0-28%.

Epidemiology

Based on death certificates sudden cardiac death accounts for about 15% of all death in Western countries (330,000 per year in the United States). The lifetime risk is three times greater in men (12.3%) than women (4.2%) based on analysis of the Framingham Heart Study
Framingham Heart Study
The Framingham Heart Study is a long-term, ongoing cardiovascular study on residents of the town of Framingham, Massachusetts. The study began in 1948 with 5,209 adult subjects from Framingham, and is now on its third generation of participants...

. However this gender difference disappeared beyond 85 years of age.

Ethical issues

Some people choose to avoid aggressive measure at the end of life. A do not resuscitate
Do not resuscitate
In medicine, a "do not resuscitate" or "DNR" is a legal order written either in the hospital or on a legal form to respect the wishes of a patient to not undergo CPR or advanced cardiac life support if their heart were to stop or they were to stop breathing...

 (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 cardiopulmonary resuscitation
Cardiopulmonary resuscitation
Cardiopulmonary resuscitation is an emergency procedure which is performed in an effort to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person in cardiac arrest. It is indicated in those who are unresponsive...

. Other directive may be made to stipulate the desire for intubation
Intubation
Tracheal intubation, usually simply referred to as intubation, is the placement of a flexible plastic or rubber tube into the trachea to maintain an open airway or to serve as a conduit through which to administer certain drugs...

 in the event of respiratory failure
Respiratory failure
The term respiratory failure, in medicine, is used to describe inadequate gas exchange by the respiratory system, with the result that arterial oxygen and/or carbon dioxide levels cannot be maintained within their normal ranges. A drop in blood oxygenation is known as hypoxemia; a rise in arterial...

or if confort measures are all that are desired by stipulating "allow natural death".

External links

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