Sustained Monomorphic Ventricular Tachycardia

Now let’s turn our attention to a very, very dangerous rhythm: sustained monomorphic VTach. Electrocardiographically, sustained monomorphic VTach has all of the characteristics of NSVT. The difference lies in the length and severity of the rhythm. Sustained monomorphic VTach can either (1) last longer than 30 seconds or (2) last shorter than 30 seconds, but requires electrical or pharmacologic intervention to terminate it because of life-threatening or severe clinical manifestations (Figure 32-19).

Figure 32-19 A PVC triggers a run of sustained monomorphic VTach.

© Jones & Bartlett Learning.

Runs of sustained VTach are also triggered by PVCs and are caused by reentry in over 90% of cases. The rhythm may be slightly irregular at the onset, but it quickly stabilizes into a very regular rhythm. Slight morphologic changes can be present due to fusion with the beats around it, or due to capture beats and fusion beats with simultaneous supraventricular complexes. AV dissociation is very common in this rhythm abnormality and needs to be actively sought out if it is not obvious.

As you can imagine, clinical manifestations are much more serious in sustained VTach. They occur from alterations in the cardiac output produced by the rhythm due to either the length of the run, lack of ventricular filling, or lack of coordinated mechanical contraction that commonly occurs with ventricular complexes. The clinical manifestations include near-syncope or lightheadedness, syncope, hypotension, altered mental status, chest pain, diaphoresis, shortness of breath, MI, stroke, pulmonary edema, cardiogenic shock, and sudden death, to name a few. Persistent stable VTach may lead to a cardiomyopathy if left untreated for an extended period of time.

In addition to the factors mentioned previously, symptoms also vary with the duration of the run. The longer the run, the greater and more dangerous the clinical spectrum. Even if the patient appears to be clinically stable during a run, he or she can deteriorate quickly and unexpectedly.

A clinical word of wisdom: Never turn your back on a patient in VTach! Stable patients can turn unstable very, very quickly and you may not have enough time to get all of the equipment you need at that time. Always have the right drugs and a defibrillator by the patient’s side, and make sure the patient is constantly monitored. A transcutaneous pacer is also a good idea to have on hand, as you do not know how the patient will react to therapy or to the rhythm itself if it persists. It is better to be safe than sorry in these cases, and preparation is critical.

Long-term management of these patients should always include a serious discussion about placing an internal cardiac defibrillator. These could be life-saving in the case of recurrence of the rhythm in the future. Remember, many times the first clinical manifestation of VTach is sudden death!