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Cardiac arrest occurs when the heart stops contracting effectively and ceases to pump blood.
Sudden cardiac arrest is not a single disease per se but a complex syndrome having several electrocardiogram (ECG) manifestations and multiple causes. Furthermore, sudden cardiac arrest is not synonymous with acute myocardial infarction (MI; “heart attack”). However, MI—acute, recent, or previous—constitutes an important cause of sudden cardiac arrest.
The closely related term sudden cardiac death applies more generally to characterize either of the following two scenarios:
An individual (with or without premonitory symptoms) sustains an unexpected cardiac arrest, is not resuscitated, and dies within minutes.
An individual dies within an hour or so of the development of acute symptoms, especially chest discomfort, shortness of breath, lightheadedness, or actual syncope.
Thus, all subjects with sudden cardiac death have sustained a cardiac arrest. However, not all subjects with cardiac arrest succumb to sudden cardiac death thanks to timely resuscitative efforts.
The patient in cardiac arrest loses consciousness within seconds. Irreversible brain damage usually occurs within 4 minutes, sometimes sooner. Furthermore, shortly after the heart stops pumping, spontaneous breathing also ceases ( cardiopulmonary arrest ). In some cases, respirations stop first (primary respiratory arrest) and cardiac activity stops shortly thereafter.
Unresponsiveness, gasping or absent respirations, and the lack of a central (e.g., carotid or femoral) palpable pulse are the major diagnostic signs of cardiac arrest.
During cardiac arrest, heart sounds cannot be auscultated and the blood pressure is unobtainable. The patient becomes cyanotic (bluish gray) from lack of circulating oxygenated blood, and the arms and legs become cool. If the brain becomes severely hypoxic, the pupils are fixed and dilated and brain death may ensue. Seizure activity may occur.
When cardiac arrest is recognized, cardiopulmonary resuscitation (CPR) efforts must be started immediately ( Box 21.1 ).
Call 911 [emergency services].
Begin manual chest compressions at the sternum, at 100 to 120 compressions per minute.
Perform manual compressions at a depth of at least 2 in. (5 cm) for an average adult.
All lay rescuers should initiate CPR until trained professionals arrive or the victim becomes responsive.
Trained rescuers may consider ventilation in addition to chest compressions: 10 breaths per minute (1 breath every 6 seconds).
The specific details of CPR and advanced cardiac life support including intubation, drug dosages, the use of automatic external defibrillators (AEDs) and standard defibrillators, and other matters related to definitive diagnosis and treatment are outside the scope of this book. These detailed aspects of CPR are discussed at the websites of major professional societies, including the American Heart Association (AHA) and the American College of Cardiology (ACC).
The three basic ECG patterns seen during cardiac arrest were mentioned in earlier chapters ( Chapters 13 and Chapter 16 ; Box 21.2 ). These patterns are briefly reviewed in the following sections, with emphasis placed on their clinical implications ( Figs. 21.1–21.6 ).
Ventricular tachyarrhythmia, including ventricular fibrillation (VF) or a sustained type of pulseless ventricular tachycardia (VT)
Brady-asystolic rhythm (asystole or bradycardia with an extremely slow rate)
Pulseless electrical activity (PEA)
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