Figure 38-9 Asystole.
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Asystole refers to the complete absence of any electrical cardiac activity (Figure 38-9). Electrocardiographically, it is represented as a straight or almost straight line on the strip. The straight line is due to the complete lack of any depolarization waves or vectors. There is a complete absence of any P, QRS, or T waves anywhere along the strip. A good way to think of it is like this: If it looks like a straight line drawn across the ECG paper by 4-year-old, it is probably asystole.
Figure 38-9 Asystole.
© Jones & Bartlett Learning.
As you can imagine, the patient is clinically dead at this point. There is no electrical or mechanical activity whatsoever. However, that doesn’t mean that the patient has to stay that way. If clinically indicated, you should begin to follow the ACLS protocol for asystolic arrest. The decision about when to call or terminate a code is subjective, and there are no set rules for this decision. For completeness, you should always switch monitor leads to make sure that the patient is not in fine VFib or that you are looking at a completely isoelectric lead (very rare occurrence). If you see a straight line in three or more leads, the diagnosis of asystole can be made.
Here is a clinical pearl. Cardioversion or defibrillation does not kick-start the heart but rather stops it cold. We are saying this so that you remember that defibrillating or cardioverting a truly asystolic patient is contraindicated. Normally, the reason you cardiovert or defibrillate someone is to apply an electrical current to the heart in order to stop all electrical activity and allow a normal cardiac pacemaker to resume its normal role. However, in true asystole, you do not have any electrical activity in the first place. Applying the external current will not be effective and may actually cause damage to the myocardial tissue, further complicating your management if a spontaneous rhythm does eventually return. Use of a transvenous or transthoracic external pacing device in an asystolic arrest, on the other hand, would be an excellent idea.
Agonal rhythm, is a variant term for asystole that is sometimes used by clinicians during daily practice (Figure 38-10). An agonal rhythm is basically asystole with an occasional P wave or QRS complex. The QRS complexes, when they occur, are very wide and very bizarre in morphologic appearance. They are even bizarre by ectopic ventricular complex standards.
Figure 38-10 Agonal rhythm.
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An agonal rhythm is a terminal event and should be treated clinically as asystole. The occasional complexes are the last efforts made by a dying heart. Remember, a ventricular rate below 20 beats per minute (BPM) is not typically seen in an idioventricular escape rhythm.