If the patient presents in stable ventricular tachycardia, confirm the rhythm with a 12-lead EKG, keeping in mind that the following rhythms can mimic ventricular tachycardia:
- SVT and atrial fibrillation with aberrancy
- Accelerated idioventricular rhythms
- Pre-excited tachycardias with accessory pathways
- Torsade de pointes.4
Remember, if there is no AV disassociation, the rhythm is not ventricular tachycardia. AV disassociation is signaled by the presence of P waves not correlated to any QRS complexes.
After confirming ventricular tachycardia, and the patient is stable, ALS providers may administer antiarrhythmic medications. Antiarrhythmics work to decrease irritability of the heart, which may allow the heart's inherent pacemaker to take over contraction stimulation. The ideal antiarrhythmic treatment includes a drug bolus followed by a maintenance infusion.
Amiodarone is the American Heart Association's antiarrhythmic of choice for VT;4 however, this was not based on evidence but rather on expert opinion. Several recent drug reviews found amiodarone less effective at rhythm conversion than procainamide and just as effective as lidocaine.5,6 After confirming ventricular tachycardia, administer 150 milligrams of amiodarone IV over 10 minutes. This generally can be repeated once in the prehospital setting, although a maintenance IV is often established in the ED at a rate of 1 mg/min. If allowed, establish an amiodarone drip following rhythm conversion.3
Ventricular tachycardia can be managed with procainamide, which eliminates the dysrhythmia more effectively than amiodarone.5 Procainamide decreases ventricular automaticity and slows conduction through the myocardium. Since only two studies have ever demonstrated its effectiveness, it remains a second-line medication. Administer procainamide 20–30 mg/min through an IV drip. Procainamide has been shown to cause hypotension, especially in situations when left ventricle function has been impaired. This drug has also been known to induce atrioventricular conduction disturbances, including heart block, and must be used with extreme caution in patients who have previously received amiodarone.1
Discontinue procainamide administration as soon as one of the following conditions is met:
- The dysrhythmia is converted
- The patient becomes hypotensive—a systolic blood pressure less than 90
- The QRS complex widens by 50%
- The patient is given a total of 17 mg/kg.
Lidocaine, formerly the drug of choice for v-tach termination, has been linked to an increase in asystole following defibrillation; however, there are few other side effects, and it is considered safer than some antiarrhythmics. Lidocaine suppresses premature ventricular contractions by raising the irritability threshold of ventricular tissues.7 The recommended dose is 1–1.5 mg/kg given as an IV bolus. This dose can be repeated at 5- to 10-minute intervals to a maximum dose of 3 mg/kg. If necessary, lidocaine can be administered through an endotracheal tube; amiodarone cannot.4 Following rhythm conversion, begin a lidocaine drip between 1–4 mg/min.3
When a patient presents in torsade de pointes with pulse, administer 1–2 grams of magnesium sulfate over 5 to 60 minutes as an IV drip diluted in 50–100 ml of D5W.4
Unstable ventricular tachycardia is treated by ALS providers with immediate synchronized cardioversion. Begin preparation for cardioversion by placing the cardiac monitor pads on the patient. The American Heart Association recommends the use of hands-free pads over hand-held paddles.4 Hands-free pads provide better skin contact, are safer and provide more consistent electricity delivery.
When considering sedatives and analgesics for cardioversion, remember that synchronized cardioversion is a very invasive emergency procedure performed on unstable patients. If your patient is stable enough to delay cardioversion for sedatives, he or she is likely also stable enough to have antiarrhythmics administered before cardioversion. Sedation is generally administered to patients to help prevent the memory of cardioversion. Midazolam is more frequently used, but may worsen or cause hypotension. Amidate does not have as profound an effect on blood pressure and may be more appropriate for patients who are already hypotensive.