Stable Ventricular Tachycardia of Ischemic Origin Case Study

8/20/2012 | AMRI faculty

A 49-year-old 80 kg. male is admitted to your emergency department complaining of “a tight chest” beginning approximately 15 minutes ago. You place him on the ECG monitor, which shows a sinus rhythm with what appears to be ST segment elevation in leads II and III. Oxygen is administered via a nasal cannula. Suddenly the patient calls out “my chest is pounding.” When you look at the ECG monitoring, you note that the previous sinus mechanism has changed to a broad QRS regular tachycardia (rate = 158).

The patient’s level of consciousness is unchanged - stable. An IV line is inserted, and an 80 mg. bolus of lidocaine is administered. The patient remains stable and the rhythm unchanged for 8 minutes. At the time a second bolus of lidocaine (40 mg.) is administered. Within several minutes, the ECG shows conversion back to sinus rhythm. The patient remains stable. It is determined that the patient is having an ST segment elevation myocardial infarction (STEMI) and will be transported to the cardiac special procedures laboratory for angiography and possible angioplasty. Just before leaving for the lab, the patient developed the broad QRS tachycardia again. His hemodynamic status remains stable. A third bolus of lidocaine is administered. (40 mg.), which causes conversion back to sinus with several minutes. A 3.0 mg./min. continuous lidocaine infusion was initiated and the patient was transported.

Important Considerations

The presenting clinical picture looks possibly ischemic in character

Based on the history, it seems highly likely the patient has developed ischemic ventricular tachycardia (VT)

Initially, the most important priority is to determine whether the VT is causing adverse changes in the patient’s perfusion status

Because of the high likelihood of the arrhythmia being ischemically induced VT, lidocaine (sodium channel blocker) was selected.

The 80 mg. initial bolus (1.0 – 1.5 mg./kg. was ineffective, so the second dose (0.5 – 1.0 mg./kg. resulted in conversion back to a sinus rhythm

It is rather unsurprising that with the cause (ischemia) not addressed, the patient had a reinduction of the arrhythmia requiring another bolus of lidocaine to convert

Because lidocaine has a relatively short alpha half-life, (approx. 8 minutes) a continuous infusion of lidocaine was required to maintain the therapeutic blood level

Other antiarrythmic agents that could be considered: procainamide and amiodarone

Because both take much longer to administer, and in the case of amiodarone, has an extremely long tissue half-life, the use of lidocaine in this case seemed best. If this was not ischemically related, the procainamide or amiodarone would have been better options

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