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4.3.3.3 Ventricular flutter and fibrillation
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4.3.3.3 Ventricular flutter and fibrillation

Ventricular flutter results from the rapid (more than 300 per minute), repetitive, regular beating of the ventricles and produced by a single ventricular focus firing at a definite rate. The important sign of this arrhythmia is appearance of smooth waves.

In ventricular fibrillation, the ventricular muscle fibers contract in a totally irregular and ineffective way because of the very rapid discharge of multiple ventricular ectopic foci or a circus movement.

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Figure 35 — Ventricular flutter

ECG signs of ventricular flutter:

Smooth waves appearance.

Regular and relatively equal waves.

The fibrillating ventricles can be produced by an electric shock or an extrasystole during a critical interval, the vulnerable period. The vulnerable period coincides in time with the T wave, it occurs at a time when some of the ventricular myocardium is depolarized, some is incompletely repolarized, and some is completely repolarized. These are excellent conditions in which to establish reentry and a circus movement.

 

Figure 36 — Re-entry mechanism of fibrillation

The fibrillating ventricles cannot pump blood effectively, and circulation of the blood stops. Therefore, in the absence of emergency treatment, ventricular fibrillation that lasts more than a few minutes is fatal. The most frequent cause of sudden death in patients with myocardial infarcts is ventricular fibrillation.

Although ventricular fibrillation may be produced by electrocution, it can often be stopped and converted to normal sinus rhythm by means of electrical shocks. Electronic defibrillators are now available not only in hospitals but also in emergency vehicles and should be used as rapidly as possible. In addition, defibrillators are implanted surgically in patients who are at high risk for attacks of ventricular fibrillation.

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Ventricular Fibrillation

 

Figure 37 — Ventricular fibrillation

ECG signs of ventricular flutter:

Rhythm is irregular.

Disorganized electrical activity of the heart.

Life-threatening arrhythmias can often be managed effectively with exogenously delivered currents of electricity. The use of defibrillation delivers an electrical current (shock) of preset voltage to the heart through paddles placed on the chest wall (closed chest procedure). This current causes the entire myocardium to depolarize completely at the moment of shock, thus producing transient asystole and allowing the heart’s intrinsic pacemakers to regain control. Defibrillators can be used to perform either synchronized cardioversion or unsynchronized cardioversion (commonly called defibrillation). Defibrillation is always indicated in ventricular fibrillation and is also used in ventricular tachycardia when the client is unconscious and pulseless.

An automated external defibrillator delivers electrical shocks to a client, after it identifies VT, through adhesive sternal-apex pads on flexible cables, which allows «hands-free» defibrillation, a feature available with conventional defibrillation as well. The automatic implantable cardioverter-defibrillator consists of a pulse generator and a sensor that continuously monitors heart rhythm. When the device detects an arrhythmia, it automatically delivers a countershock. The automatic implantable cardioverter-defibrillator is usually implanted surgically into a pouch below the left clavicle or into the abdominal cavity for the following conditions: survival of one or more episodes of sudden cardiac death resulting from ventricular tachycardia or fibrillation; recurrent, refractory, life-threatening ventricular arrhythmias that can develop into ventricular tachycardia or fibrillation, or both, despite antiarrhythmic therapy.



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