SCA, or Sudden Cardiac arrest, also known as cardiopulmonary arrest or circulatory arrest, is the cessation of functional circulation of the blood due to failure of the heart to contract effectively. Medical personnel may refer to an unexpected cardiac arrest as a sudden cardiac arrest (SCA).
A cardiac arrest is different from (but may be caused by) a heart attack, where blood flow to the muscle of the heart is impaired. It is different from congestive heart failure, where circulation is substandard, but the heart is still pumping sufficient blood to sustain life. Arrested blood circulation prevents delivery of oxygen and glucose to the body. Lack of oxygen and glucose to the brain causes loss of consciousness, which then results in abnormal or absent breathing. Brain injury is likely to happen 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 that, in certain situations, is potentially reversible if treated early. Unexpected cardiac arrest can lead to death within minutes: this is called sudden cardiac death (SCD). The treatment for cardiac arrest is immediate defibrillation if a "shockable" rhythm is present, while cardiopulmonary resuscitation. CPR, is used to provide circulatory support and/or to induce a "shockable" rhythm.
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.
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
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, the patient will be 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 heart disease is the leading cause of sudden cardiac arrest. Sudden cardiac arrests can happen at any time with little or no warning. Any exertion which raises your heart rate can induce an SCA. The exertion doesn’t even have to be vigorous, it can be moderate or light; even mundane sexual activity can trigger cardiac arrest.
With positive outcomes following cardiac arrest unlikely (The survival rate of people who receive initial emergency care by ambulance is only 2%, with 15% experiencing return of spontaneous circulation. However, with defibrillation within 3–5 minutes, the survival rate increases to 30%, exact responses being directly linked to the cause of arrest), 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.
High Risk Factors for SCA include but are not limited to:
- Leading a sedentary lifestyle (i.e. not exercising vigorously 2-3 times a week)
- Drinking more than 2 drinks a day
- Use of cocaine, pcp, poppers or many other illicit drugs
- CAD or a family history of CAD
- High blood pressure
- High cholesterol
- Venerable Age
Please Note: Activities that produce risk of SCA due to heavy exertion are not specifically linked to greater risk of SCA based on the definitions of the activity, but instead the level of exertion involved and the general health of the individual.