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ELECTRICAL STORM

Electrical storm or ventricular tachycardia (VT) storm refers to the occurrence of three or more episodes of VT or ventricular fibrillation (VF) within 24 h. This severity of electrical instability is associated with a high mortality and requires prompt therapeutic intervention. Electrical storms occur in 4% of patients with a primary prevention implantable cardioverter defibrillator (ICD) but in as many as 20% of patients with a history of known VT or resuscitated sudden death.

MANAGEMENT OF THE PATIENT WITH ELECTRICAL STORM

Patients should be adequately sedated to allay anxiety. Recurrent VT/VF is treated using standard advanced cardiac life support guidelines and include the use of medications such as beta blockers, amiodarone, lidocaine with correction of any metabolic abnormalities. Recordings from ECG monitoring or an implanted ICD are important to assess whether VT is monomorphic or polymorphic that suggest possible precipitating or aggravating factors. Ischemia should be considered especially if polymorphic VT or VF is identified as the primary arrhythmia. If QT prolongation causing torsades des pointes is possible intravenous magnesium should be administered and bradycardia treated. If the QT interval is not prolonged and Brugada syndrome is possible, administration of quinidine and/or isoproterenol may abolish recurrent polymorphic VT/VF episodes. If the above measures fail, general anesthesia should be considered for suppression of recurrent hemodynamically unstable ventricular arrhythmia. Left stellate ganglion block and upper thoracic epidural anesthesia may reduce cardiac sympathetic outflow and have been used to restore stability in some patients. Catheter ablation of PVCs that are observed to repeatedly initiate the arrhythmia can be effective. Rarely, mechanical ventricular support or transplantation may have to be considered.

Once the acute episode is controlled, strategies to prevent recurrent VT or VF should be considered (see below).

INCESSANT VT

VT is designated incessant when VT continues to recur shortly after electrical, pharmacologic, or spontaneous conversion to sinus rhythm (Fig. 251-1). Typically, VT is monomorphic. Rarely, a slow incessant monomorphic VT will fail detection by the ICD because it falls outside of the programmed detection parameters. If the arrhythmia is hemodynamically stable acutely, patients can present with symptoms of gradual cardiac decompensation. VT may become incessant due to the pro-arrhythmic effect of an antiarrhythmic drugs such as amiodarone or a sodium channel blocker such as flecainide. Hemodynamic support may be required until the precipitating factors can be corrected. Urgent catheter ablation is often warranted.

FIGURE 251-1

Example of incessant monomorphic VT. In the initial portion of this ECG tracing, monomorphic VT is present. A train of antitachycardia pacing (area bracketed by arrows) that is initiated at the 4th VT complex results in ventricular capture with fusion by the 8th beat and termination of VT at cessation of pacing. The patient has underlying atrial fibrillation. Multifocal PVCs are present. VT similar in morphology to the initial VT restarts spontaneously toward the ...

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