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Electrical Storm and Incessant Ventricular Tachycardia


Ventricular tachycardia (VT) accounts for 5% to 10% of admissions to cardiac intensive care units (CICUs). With the successes of modern reperfusion therapy to reduce mortality in ST elevation myocardial infarction (STEMI), of pharmacotherapy and implantable cardioverter defibrillators (ICDs) to prolong survival in heart failure, and of implantable left ventricular assist devices (LVADs) to sustain life in end-stage cardiomyopathy, the number of patients with the substrate for ventricular arrhythmias continues to increase. In addition, an increasing number of genetic arrhythmia syndromes and proarrhythmic medications are being identified. This chapter will focus on patients who present with the life-threatening syndromes of electrical (or VT) storm and incessant VT.

Definition

Although there are multiple definitions, electrical storm is commonly defined by three or more episodes of VT, ventricular fibrillation (VF) or appropriate ICD shocks in a 24-hour period. This definition does not capture ICD patients with VT that is slower than the programmed detection rate of the device or VT that is terminated by antitachycardia pacing. Incessant VT is defined as hemodynamically stable VT that lasts for more than 1 hour. These events may develop during acute coronary syndromes (ACS), including acute myocardial infarction (MI), in patients with pre-existing structural heart disease or in patients with structurally normal hearts, such as those with Brugada or long QT syndromes (LQTS). Causes of electrical storm are presented in Box 24.1 .

Box 24.1
From Maruyama M. Management of electrical storm: the mechanism matters. J Arrhythmia . 2014;30:242–249.
Causes of Electrical Storm

  • Structural heart disease

  • Ischemic heart disease

    • Acute or recent myocardial infarction/acute coronary syndrome

    • Prior myocardial infarction

  • Nonischemic heart disease

    • Dilated cardiomyopathy

    • Hypertrophic cardiomyopathy

    • Arrhythmogenic right ventricular dysplasia/cardiomyopathy

    • Valvular heart disease

    • Corrected congenital heart disease

    • Myocarditis

    • Cardiac sarcoidosis

    • Chagas disease

    • Metastatic cardiac tumor

  • Structurally normal hearts (abnormal electrical substrate)

    • Primary causes

      • Idiopathic

      • Brugada syndrome

      • Early repolarization syndrome

      • Long QT syndrome

      • Short QT syndrome

      • Catecholaminergic polymorphic ventricular tachycardia

    • Secondary causes

      • Electrolyte abnormalities

      • Toxic/drug related

      • Endocrinologic

      • Perioperative

      • Iatrogenic (T wave pacing)

Incidence

The incidence of electrical storm is a function of the population described and the definition used. In patients with ICDs, when electrical storm is defined by more than two VT/VF episodes requiring device therapy within a 24-hour period, the incidence is 2% to 10% per year of follow-up. Patients with ICDs placed for primary prevention develop electrical storm less frequently than those in whom they were placed for secondary prevention. The incidence of electrical storm when ICDs are placed for primary prevention in the setting of ischemic cardiomyopathy is about 4% over 20.6 months. In contrast, the incidence of electrical storm is approximately 28% in dilated cardiomyopathy patients with ICDs implanted for secondary prevention during a mean follow-up of 33 ± 23 months.

Triggers

Although it has been estimated that only 10% to 25% of patients have reversible factors triggering the electrical storm episode, correctable triggers should be considered in all patients presenting with electrical storm or incessant VT. Potential triggers are listed in Box 24.2 . If an apparently responsible trigger can be found, it should be treated aggressively.

Box 24.2
Reversible Triggers of Electrical Storm

  • Acute myocardial ischemia

  • Electrolyte abnormalities (hypokalemia and hypomagnesemia)

  • Decompensated heart failure

  • Hyperthyroidism

  • Infections, fever

  • QT prolongation

  • Drug toxicity

  • Electrolyte imbalance

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