ACLS Megacode 9: Ventricular Tachycardia

This patient is stable and most likely has supraventricular tachycardia, a common form of tachycardia typically caused by a reentry circuit in the conduction system. This condition most commonly presents with a narrow QRS, however the QRS interval can be >120 ms in cases associated with aberrant conduction or a fixed bundle branch block. Vagal maneuvers such as Valsalva or carotid sinus massage block conduction at the AV node, disrupting the reentry system, making them an appropriate initial intervention in these patients. Studies have shown an SVT conversion rate to sinus rhythm up to 25%, particularly with Valsalva followed by supine positioning and passively raising their legs as shown by the REVERT trial.

SVT that is refractive to vagal maneuvers should be treated with adenosine. Adenosine has an extremely short half-life of less than 10 seconds. It should be administered via rapid injection into a large proximal vein, followed by a normal saline flush of 20 mL and extremity elevation. Patients should be on continuous EKG monitoring during administration.

As seen here, it’s essential that patients are warned of the significant albeit transient side effects prior to adenosine injection, which include flushing , chest pain and difficulty breathing. If the initial 6 mg dose is ineffective, it is appropriate to give a 2nd and even 3rd dose of adenosine at 12 mg. If adenosine continues to fail in converting SVT after the 2nd and 3rd attempt, you should consider other etiologies such as A-Flutter or non-reentrant SVT. It’s important to remember that larger doses (18 mg) may be needed in patients who consume very large amounts of caffeine or take theophylline, as these decrease the effectiveness of adenosine. Conversely, those receiving the injection into the central vein, a history of heart transplant, or taking the anti-epileptic carbamazepine or the vasodilator dipyridamole may need smaller doses (3 mg).

This patient has become acutely unstable, with conversion of his rhythm to a ventricular tachycardia (VT). Patients with regular, wide complex monomorphic VT and a palpable pulse should be immediately treated with 100 J synchronized cardioversion.

The patient has continued to deteriorate, now exhibiting a pulseless VT. The best initial treatment for a witnessed cardiac arrest is delivery of an unsynchronized shock, also known as defibrillation. This should be performed as soon as possible, as decreased time to defibrillation has been shown to improve the odds for return of perfusion and survival.

In adult victims, ideal delivery of CPR should be at 100-120 compressions per minute at a minimum depth of 2 inches. Compressions >2.4 have been associated with higher rate of iatrogenic injury. It is very important to note that CPR should be performed immediately following defibrillation without a pulse recheck. Guidelines recommend CPR be continued without interruption, with assessment of pulse no more than every 2 minutes.

If after two minutes of CPR, rhythm analysis reveals ongoing pulseless VT, a second shock should be delivered at the same (maximum) biphasic dose.

After a second shock is delivered, the ACLS algorithm allows for initiation of 1 mg Epinephrine given intravenously every 3-5 minutes. It is very important to note that Vasopressin was removed entirely from this algorithm with the last guideline revisions.

After delivery of a third shock, the ACLS algorithm recommends initiation of Amiodarone at 300 mg in patients without return of spontaneous circulation (ROSC). A repeat dose of 150 mg may be considered if necessary. If amiodarone is unavailable, Lidocaine can be considered at a dose of 1-1.5 mg/kg for the first dose, followed a second dose that is half of the first (0.5-0.75 mg/kg).

Neurologic injury is the most common cause of mortality in out of hospital cardiac arrest, but contributes significantly to in-patient mortality as well. Studies have shown that lowering the core body temperature to 32-36 °C in the hours immediately following cardiac arrest improves neurologic outcomes.

In the absence of an advanced directive specifically refusing this intervention, all patients who are unable to follow commands or show purposeful movement after ROSC should undergo management of their core temperature.