Figure 31-1 A ventricular escape complex.
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When the primary supraventricular pacemakers fail for a short time, the ventricles will quickly take over and fire a ventricular escape complex. This is to make sure that a ventricular mechanical contraction occurs. As we mentioned before, it is the ventricular rate that maintains control over the cardiac output in the vast majority of cases. In other words, the loss of the atrial kick does not compare with the loss of the ventricular “kick.” The bottom line is that we need our ventricles to work if we want to stay alive.
The ventricular escape complexes have all of the characteristics of ventricular complexes, as we have seen and covered in Chapter 29, Introduction to Ventricular Rhythms. They arrive late during the cadence of the rhythm, after a supraventricular pacer fails to fire. The R-R interval, therefore, is longer than expected (Figure 31-1).
Figure 31-1 A ventricular escape complex.
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NOTE
It is our opinion that when you are faced with a slow ventricular escape rhythm, you should try to speed it up by using either a transvenous or transthoracic electric pacemaker, as long as you can place one quickly. We make this suggestion because an external temporary cardiac pacer will let you achieve a controlled rate of increase, one that you can manually adjust to maximum benefit.
Pharmaceutical agents can also be used to speed up the heart and are usually faster to deliver. But, be aware that you cannot control the patient’s physiologic response to them as well as you can control a cardiac pacer. Giving a drug like atropine will typically speed up the heart, but how fast it will go is anyone’s guess. In some cases, too fast a rate can be just as dangerous as too slow a rate. Pharmaceutical agents can be a great asset if you cannot get external pacemaker control quickly or if your pacer fails to capture. Please be aware that this reflects our own individual clinical practice, and there is a lot of controversy as to the best approach. For a more thorough and complete discussion, a review of the current literature is suggested.
Ventricular escape complexes can occur singly or they can appear in pairs (Figure 31-2). If there are more than three sequential ventricular escape complexes, it then becomes known as an idioventricular escape rhythm.
Figure 31-2 Two ventricular escape complexes.
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If a P wave is present in a ventricular escape complex, it is because the supraventricular P wave failed to conduct to the ventricles or it is retrograde from the ventricular escape complex itself. Multiple ventricular escape complexes are usually associated with atrioventricular (AV) dissociation (Figure 31-3).
Figure 31-3 Two ventricular escape complexes with associated AV dissociation.
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