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M5Here is a simulation of a heart monitor showing normal sinus rhythm suddenly decline into monomorphic ventricular tachycardia then subsequently coarse ventricular fibrillation and finally asystole. Of course many factors precede cardiac arrest however this is the typical rhythm progression if untreated. Sudden cardiac arrest (SCA) and sudden cardiac death (SCD) occur when the heart abruptly begins to beat in an abnormal or irregular rhythm (arrhythmia). Without organized electrical activity in the heart muscle, there is no consistent contraction of the ventricles, which results in the heart's inability to generate an adequate cardiac output (forward pumping of blood from heart to rest of the body). There are many different types of arrhythmias, but the ones most frequently recorded in SCA and SCD are ventricular tachycardia (VT) or ventricular fibrillation (VF). Less common causes of dysrhythmias in cardiac arrest include pulseless electrical activity (PEA) or asystole. Such rhythms are seen when there is prolonged cardiac arrest, progression of ventricular fibrillation, or due to efforts such as defibrillation to resuscitate the person. Ventricular tachycardia can occur due to coronary heart disease, aortic stenosis, cardiomyopathy, electrolyte problems, or a heart attack. Diagnosis is by an electrocardiogram (ECG) showing a rate of greater than 120 beats per minute and at least three wide QRS complexes in a row. V-Fib has an appearance on electrocardiography of irregular electrical activity with no discernable pattern. It may be described as 'coarse' or 'fine' depending on its amplitude, or as progressing from coarse to fine V-fib. Coarse V-fib may be more responsive to defibrillation, while fine V-fib can mimic the appearance of asystole on a defibrillator or cardiac monitor set to a low gain. Some clinicians may attempt to defibrillate fine V-fib in the hope that it can be reverted to a cardiac rhythm compatible with life, whereas others will deliver CPR and sometimes drugs as described in the advanced cardiac life support protocols in an attempt to increase its amplitude and the odds of successful defibrillation.
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