Cardiac & Resuscitation, Patient Care

Strategies for the Prehospital Treatment of Stable Ventricular Tachycardia

Issue 3 and Volume 41.

Patients with stable v tach may experience a constellation of symptoms but generally don’t require cardioversion unless instability develops.

Patients with stable v tach may experience a constellation of symptoms but generally don’t require cardioversion unless instability develops. Photo Matthew Strauss

 

You’re dispatched for an “ill” 55-yearold male. Upon arrival you find him sitting on the sofa in no apparent distress. He states he’s been feeling ill for the past three days. He’s otherwise asymptomatic.

Initial assessment reveals an intact airway, normal breathing and clear lungs, no neurologic deficits, and no gross abnormalities on exposure.

During the circulation exam, you note a regular rhythm with a fast heart rate. Capillary refill is normal, peripheral pulses are strong, and skin color and temperature are normal.

Initial vital signs are: heart rate (HR) 145 bpm, blood pressure (BP) 130/90 mmHg, respiratory rate (RR) 14 and pulse oximetry 97% on room air.

The patient has a past medical history of hypertension controlled with lisinopril, no allergies, no previous surgeries, and denies the use of alcohol, tobacco or other drugs. The remaining physical examination is unremarkable.

Your partner initiates an IV while you place the patient on the cardiac monitor and obtain a 12-lead ECG. You and your partner review it and determine the patient is experiencing ventricular tachycardia (v tach). Despite the patient endorsing mild symptoms, you conclude the patient is hemodynamically stable. What are the pharmacologic treatment strategies for prehospital stable v tach?

BACKGROUND

The clinical manifestations of v tach occur along a spectrum. Patients are typically classified as pulseless, unstable or stable.

Pulseless v tach is typically treated with advanced cardiac life support (ACLS) interventions, including CPR, defibrillation and antidysrhythmics.1 Unstable v tach is most often treated with electrical cardioversion.

Patients with stable v tach may experience a constellation of symptoms, like the patient in the case scenario, but generally don’t require cardioversion unless instability develops.

Antidysrhythmics recommended for the treatment of various subtypes of stable v tach include amiodarone, lidocaine and procainamide.1 However, review of the field care of the patient in stable v tach reveals a tendency among some agencies to administer supportive care only.

We report here the results of a survey of the U.S. Metropolitan Municipalities EMS Medical Directors (“Eagles”) Consortium regarding the treatment of stable v tach in the prehospital arena.

SURVEY RESULTS

The members of the U.S. Metropolitan Municipalities EMS Medical Directors Consortium were surveyed in August 2015 regarding which pharmacologic interventions are used by their EMS agencies for the treatment of stable v tach. A total of 36 medical directors participated in the survey. The results are summarized in Table 1.

Treatment methods of stable v tach

The most commonly utilized antidysrhythmic was amiodarone (67%), followed by lidocaine (22%). Two agencies used more than one pharmacologic agent (e.g., lidocaine and procainamide, or lidocaine and amiodarone). Two agencies reported only supportive treatment of stable v tach presenting in the field.

DISCUSSION

Stable v tach presents as a regular wide-complex rhythm, and the appropriate rhythm diagnosis can be a challenge to EMS providers. The spectrum of the treatment options for stable v tach include “waitful watching” during the prehospital phase, antidysrhythmic therapy at any phase, and elective cardioversion at the appropriate juncture.1

The 2010 American Heart Association (AHA) Guidelines Update recommended procainamide, amiodarone, sotalol or lidocaine for the treatment of stable v tach.Table 2 below provides information on recommended antidysrhythmic dosing and potential side effects of administration.

The new 2015 AHA guidelines recommend procainamide, amiodarone or sotalol for the treatment of stable v tach. However, a higher class of recommendation is given to procainamide compared to amiodarone and sotalol. Procainamide and sotalol should be avoided in patients with a prolonged QT interval. In stable polymorphic v tach, magnesium and amiodarone may be helpful.2

Deciding which antidysrhythmic agent to use for stable v tach treatment can be a complex decision with several considerations. The first consideration is determining which agent is most effective. Research has suggested superiority of procainamide and sotalol over lidocaine for termination of stable v tach.2,3

Amiodarone is recommended in ACLS guidelines for the treatment of v tach, but the effectiveness of amiodarone has also been questioned. In a retrospective case series, authors concluded amiodarone is safe but ineffective for termination of v tach.4 Another study concluded from a retrospective case series that amiodarone is also ineffective for treatment of stable monomorphic v tach.5

Antidysrhythmic therapies for v tach

The second consideration is the risk-benefit ratio of antidysrhythmic agents, which are associated with serious side effects that can worsen patient outcome. (See Table 2.) For example, patients with pre-existing QT interval prolongation may experience polymorphic v tach (“torsades de pointes”) if administered procainamide or sotalol.

Amiodarone administration can be complicated by patient characteristics (e.g., pregnancy), wrong rhythm classification (e.g., irregular, wide-complex tachycardia suggesting atrial fibrillation with aberrant conduction; polymorphic v tach), and clinical side effects (e.g., hypotension).

Often, predisposing risk factors can be difficult to identify in the emergent scenario involving the undifferentiated critically ill patient who can provide limited past medical history.

The third consideration is whether antidysrhythmic therapy is actually necessary to safely manage clinically stable v tach in the prehospital setting.

Given the conflicting evidence for clinical efficacy, the presence of multiple side effects, and difficulties in recognizing potential contraindications, the medical directors of some EMS agencies have chosen not to include antidysrhythmic agents as a part of standard operating protocol for this condition. Indeed, non-treatment (i.e., “waitful watching”) of stable v tach is an option in some EMS systems, with more aggressive care being initiated should the patient’s condition declines.

If supportive care is insufficient and instability develops, further measures including synchronized cardioversion may be employed.

The fourth consideration is whether the antidysrhythmic agent used for stable v tach should be the same one used for either unstable v tach or v tach without a pulse.

An important consideration for EMS systems is that utilizing the same agent for various conditions eases stocking, training and other logistical concerns. However, although amiodarone is the antidysrhythmic agent recommended by the AHA for pulseless v tach, this recommendation is not based on high levels of evidence but rather only on expert opinion.6

It may be useful to repeat this survey following the publication of the 2015 AHA Guidelines to determine if any significant change occurs from the current field management of stable v tach.

Moreover, the authors of the present study believe that the clinical outcomes from EMS management of these patients should be measured according to rigorous criteria.

A research study highlighting drug intervention vs. supportive care would help validate the guidelines via clinical data, likely giving rise to recommendations that provide a unified approach to the clinical management of these patients.

CONCLUSION

Providing a review of various approaches used by larger EMS systems, this discussion highlights variations in the management of the treatment of prehospital patients with stable v tach.

EMS systems must consider clinical efficacy, safety of use, need for prehospital administration, potential contraindications, and operational issues when selecting the method of managing these cases.

REFERENCES

1. Neumar RW, Otto CW, Link MS, et al. Part 8: Adult advanced cardiovascular life support. 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care science. Circulation. 2010;122(18 Suppl 3):S729–S767.

2. Link MS, Berkow LC, Kudenchuk PJ, et al. Part 7: Adult advanced cardiovascular life support. 2015 American Heart Association guidelines update for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2015;132(18 Suppl 2):S444–S464.

3. Gorgels AP, van den Dool A, Hots A, et al. Comparison of procainamide and lidocaine in terminating sustained monomorphic ventricular tachycardia. Am J Cardiol. 1996;78(1):43–46.

4. Ho DS, Zecchin RP, Richards DA, et al. Double-blind trial of lidocaine versus sotalol for acute termination of spontaneous sustained ventricular tachycardia. Lancet. 1994;344(8914):18–23.

5. Marill KA, deSouza IS, Nishijima DK, et al. Amiodarone is poorly effective for the acute termination of ventricular tachycardia. Ann Emerg Med.2006;47(3):217–224.

6. Tomlinson DR, Cherian P, Betts TR, et al. Intravenous amiodarone for the pharmacological termination of hemodynamically tolerated sustained ventricular tachycardia: Is bolus amiodarone an appropriate first line treatment? Emerg Med J. 2008;25(1):15–18.