![]() The absence of mechanical contractions and palpable pulse are due to either the absence of synchronous myocyte depolarisation, vascular failure or alterations of cardiac function. Pulseless electrical activity (PEA) cardiac arrests present with residual organised electrical activity on the electrocardiogram that would normally be associated with a palpable pulse. PEMS: prehospital emergency medical service Introduction These conditions are potentially accessible to simple diagnostic procedures (computed tomography or echocardiography). Nonischaemic cardiac disorders and intracranial haemorrhage occurred in 8.3% and 6.9%, respectively.ĬONCLUSIONS: Intracranial haemorrhage and nonischaemic cardiac disorders represent significant causes of PEA, with a prevalence equalling or exceeding the frequency of classical 4H&4T aetiologies. Pulmonary embolism, hypovolaemia, intoxication and hypo/hyperkalaemia occurred in fewer than 10% of the cases. We were unable to identify a specific cause in 17.4%. Hypoxia (23.6%), acute coronary syndrome (12.5%) and trauma (12.5%) were the most frequent causes. The mean age was 63.8 ± 20.0 years, 58.3% were men. PEA was the first recorded rhythm in 232 adult patients (12.4%) and 144 of these were admitted to the ED. RESULTS: A total of 1,866 out-of-hospital cardiac arrests were included. All adult patients with PEA as the first recorded rhythm and admitted between 20 to the emergency department (ED) after return of spontaneous circulation or under resuscitation were included. METHODS: This was a retrospective study based on data routinely and prospectively collected. The aim of this study was to analyse the aetiologies of PEA out-of-hospital cardiac arrests and to evaluate their relative frequencies. Other potential aetiologies have been identified, but their respective probability and frequencies are unclear. The mnemonic “4H&4T” was proposed as a reminder to assess for Hypoxia, Hypovolaemia, Hypo/Hyperkalaemia, Hypothermia, Thrombosis, cardiac Tamponade, Toxins, and Tension pneumothorax. ![]() PEA is frequently induced by reversible conditions. If the patient is in asystole, CPR is the appropriate treatment and the presence of asystole is likely to be recognised by its persistence.BACKGROUND:Pulseless electrical activity (PEA) cardiac arrest is characterised by a residual organised electrical activity. If the patient was in fine VF then good CPR may increase the amplitude and frequency of VF, making it easier to identify and more likely to respond to defibrillation. The best treatment in this situation is immediate high quality CPR. Sometimes during cardiac arrest it is not certain whether the ECG shows asystole or very fine VF. Atrial contraction alone will not maintain cardiac output, so cardiac arrest will be present, but patients with ventricular standstill and continued P wave activity may have a better chance of survival as cardiac pacing may restore ventricular contraction. Occasionally ventricular asystole (sometimes called ventricular standstill) occurs in the presence of continued P wave activity in the atria. The absence of any electrical activity indicates asystole in atria as well as ventricles. If the patient is pulseless and there is no electrical activity on the ECG, this is asystole. If pre-excited AF causes cardiac arrest and is mistaken for VF or pulseless VT, immediate defibrillation will be likely to correct the rhythm, although synchronised cardioversion would have been preferable. If pre-excited AF causes adverse features without cardiac arrest, the correct treatment is synchronised cardioversion, so mistaking the rhythm for VT will not lead to inappropriate treatment. Pre-excited atrial fibrillation (AF) produces an irregular broad complex tachycardia that is sometimes mistaken for VT and could in theory be mistaken for VF. If this rhythm is present and the patient is in clinical cardiac arrest the appropriate treatment is defibrillation, so mistaking the rhythm for VF will not result in inappropriate treatment. ![]() Patients may be pulseless and lose consciousness during this rhythm it may terminate spontaneously, or may degenerate into VF. The rhythm abnormality that is most likely to be mistaken for VF is polymorphic VT (Torsades de Pointes VT). If the patient has a pulse then the rhythm is not VF. If a patient is in VF they need immediate defibrillation. VF is usually easy to recognise from the ECG rhythm strip.
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