POCUS can accurately diagnose cardiac arrest in hospital settings, overcoming some of the shortcomings of diagnosis through checking the central pulse (carotid arteries or subclavian arteries), as well as detecting movement and contractions of the heart.Using POCUS, clinicians can have limited, two-dimensional views of different parts of the heart during arrest. These images can help clinicians determine whether electrical activity within the heart is pulseless or pseudo-pulseless, as well as help them diagnose the potentially reversible causes of an arrest. Published guidelines from the American Society of Echocardiography, American College of Emergency Physicians, European Resuscitation Council, and the American Heart Association, as well as the 2018 preoperative Advanced Cardiac Life Support guidelines, have recognized the potential benefits of using POCUS in diagnosing and managing cardiac arrest.Owing to the inaccuracy in this method of diagnosis, some bodies such as the European Resuscitation Council (ERC) have de-emphasised its importance. Instead, the current guidelines prompt  individuals to begin CPR on any unconscious person who has absent or abnormal breathing. The Resuscitation Council in the United Kingdom stand in line with the ERCs recommendations and those of the American Heart Association. They have suggested that the technique to check carotid pulses 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, and therefore diagnosing cardiac arrest 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, a similar protocol that of which the European Resuscitation Council has adopted. In a non-acute setting where the patient is expired, diagnosis of cardiac arrest can be done via molecular autopsy or postmortem molecular testing which uses a set of molecular techniques to find the ion channels that are cardiac defective. This could help elucidate the cause of death in the patient. Other physical signs or symptoms can help determine the potential cause of the cardiac arrest. Below is a chart of the clinical findings and signs/symptoms a person may have and a potential cause associated with it. Classifications
Clinicians classify cardiac arrest into "shockable" versus "non-shockable", as determined by the EKG 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. Prevention
With the lack of positive outcomes following cardiac arrest, efforts have been spent finding effective strategies to prevent cardiac arrest.