Case Study: Incessant VFib

A forty-nine year old woman is brought to the Emergency Department by her friends. She is complaining of a sudden onset of malaise and pressure in her neck, and she says she “just doesn’t feel OK.” Her BP is 146/90, P = 100/regular, and her Sa02 on room air is 96%. While having ECG monitoring leads placed on her, she develops course VF and quickly loses both consciousness and a pulse.

She is immediately defibrillated with a biphasic defibrillator (actual delivered energy is 120 joules). The counter-shock immediately terminates the VF and a sinus rhythm is observed. She begins gasping and her color rapidly improves. The ECG monitor shows significant ST segment elevation in leads II, III, and aVF.

As the team is drawing blood and establishing IV access, she develops VF again. An immediate and identical counter-shock is delivered returning the patient to a perfusing sinus rhythm.

POST CASE-STUDY TEST

1. Epinephrine should always be administered to any patient who has developed ventricular fibrillation (VF). True or False?

2. Lidocaine is effective at terminating ventricular fibrillation. True or False?

3. If a patient is successfully defibrillated, but reverts to VF repeatedly, they have:

1. Refractory VF
2. Incessant reinduction of VF
3. A possible indication for the use of an anti-arrhythmic agent
4. Both b and c

ANSWERS:

1. Answer: False

Rationale:  Pharmacologic therapy should only be considered when ventricular fibrillation cannot be terminated using electrical counter-shock.

2. Answer: False

Rationale: Lidocaine has never been shown to “defibrillate.” Lidocaine may increase the induction threshold for VF, but data shows lidocaine may also increase the defibrillation threshold. This could potentially make electrical defibrillation more difficult. Thus, careful clinical decision-making is required when considering the risk versus the benefit when using anti-arrhythmic drugs.

3. Answer: D

Rationale: Refractory VF does not respond (convert) to defibrillation. Incessant VP, on the other hand, does convert when shocked, but it keeps returning.

DISCUSSION:

It is important to understand the difference between refractory VF (shocks that fail to convert) and incessant re-induction of VF. Although the electrical therapy is effective, the patient persists in redeveloping the arrhythmia.

There are two urgent considerations:

1. The cause of the VF
2. Whether or not an anyarrhythmic agent should be consider to prevent reinducation

Considering the clinical picture of this patient on admission, it seems likely that she is having a STEMI (ST elevation MI). Myocardial ischemia is a likely cause of her low VF induction threshold.

The clinical question is this: Can the ischemia be treated promptly enough (possibly ending the arrhythmia problem), or should an antiarrhythmic agent be used to hopefully prevent VF re-induction while fibrinolytics or PCI are ongoing?

This answer is dependent on clinical judgment and specific circumstances.

If the answer is yes to antiarrhythmic drugs, lidocaine is probably a good option. It is most effective in ischemic settings, so it would be a sound option. If the coronary vessel was opened and the ischemia reversed, lidocaine, with its short half-life, could be immediately discontinued. Procainamide would also be effective, but it is more difficult and time-consuming to administer. Amiodarone would be a poor choice due to its slow onset of action and its very long elimination time.

Clinically speaking, the course of action is clear: Find the cause and treat it aggressively. Treating symptoms (arrhythmias) with antiarrhythmic agents when the cause is ischemia is not the best medicine.