Low ejection fraction, on the other hand, is an ejection fraction that is lower than the normal percentage. This is mainly due to abnormal enlargement of the ventricles and reduced ventricular function. Patients presenting with cardiac insufficiency often have a reduced ejection fraction. The chance of sudden death from malignant arrhythmias increases significantly when the ejection fraction drops below 35%. So how is a low ejection fraction diagnosed? A normal rhythm originates in the sinus node with a relatively regular frequency of 60 to 100 beats/min (in adults). The sinus node impulses excite the atria and ventricles sequentially through the normal atrioventricular conduction system with a constant conduction time (0.12 to 1.21 seconds in adults), and the impulses reach the ventricular muscle through the bundle branches and their branches and Purkinje fibers with a constant conduction time (cardiac arrhythmia) refers to abnormalities in any of the sites of origin of the heart rhythm, the frequency and rhythm of the heartbeat, and the conduction of impulses. The terms “arrhythmia” or “arrhythmia” are used with a preference for rhythm disorders, whereas arrhythmia includes both rhythm and frequency abnormalities, which is more accurate and appropriate. Atrial fibrillation (AF): Ectopic tachycardia in which the pacing point is in the atria. In atrial fibrillation, irregular impulses of 350 to 600 beats/min occur in the atria, causing uncoordinated atrial fibrillation. The atrioventricular conduction system is only partially receptive to atrial excitation. In atrial fibrillation, ventricular beats are fast and irregular, between 120 and 180 beats per minute. Atrial fibrillation is one of the most common arrhythmias in adults and is far more common than atrial flutter, with an incidence ratio of 10-20:1. There are two types of atrial fibrillation, paroxysmal and persistent, with the former occurring sporadically and the latter lasting for months or more. The paroxysmal ones can become persistent after repeated attacks. Atrial flutter (atrial flutter): is an ectopic tachycardia of atrial origin that can transform into atrial fibrillation. Atrial flutter produces regular impulses of about 300 beats/min in the atria, causing fast and coordinated atrial contractions. Most of the ventricular rhythms are regular (atrioventricular conduction ratio is mostly 2-4:1), a few are irregular (uneven atrioventricular conduction ratio), and the ventricular rate is often between 140-160 beats/min. Atrial flutter is also divided into two types, paroxysmal and persistent, and its incidence is less than that of atrial fibrillation. Pre-excitation: It is an abnormal phenomenon of atrioventricular conduction in which the impulse is transmitted down through additional channels and excites part or all of the ventricle early, causing early excitation of part of the ventricular muscle. Pre-excitation is called pre-exciTATionsyndrome or WPW (Wolf-Parkinson-White) syndrome and is often combined with episodes of supraventricular paroxysmal tachycardia. Pre-excitation is a less common arrhythmia and the diagnosis is mainly made by electrocardiography. This leads to the diagnosis of low ejection fraction.