Electrical storm (ES) is defined as 3 or more sustained episodes of VT, VF, or appropriate ICD shocks during a 24-hr period.1 Ischemia, infarction, severely compromised LV function, and electrolyte imbalances are important risk factors for the onset of ES. Administration of beta blockers plus an antiarrhythmic will suppress the sympathetic tone and increase the VT/VF threshold. Interventional measures such as ablation, coronary reperfusion, left sympathetic ganglionic block, ECMO, or palliative care may be warranted.
Propranolol Versus Metoprolol for Treatment of Electrical Storm in Patients With Implantable Cardioverter-Defibrillator
The Journal of the American College of Cardiology recently published study by Chatzidou, et al evaluated the efficacy of propranolol compared to metoprolol, in combination with intravenous amiodarone for the management of ES in patients with an ICD.1
- Study included a total of 60 ICD patients (45 men, mean age 65 ± 8.5 years) with ES that developed within 24 hours from admission.
- Study period was between 2011 and 2016.
- Randomly assigned to one of the therapies:
- Group A: propranolol 40 mg by mouth every 6 hrs plus IV amiodarone x 48 hrs
- Group B: metoprolol tartrate 50 mg by mouth every 6 hrs plus IV amiodarone x 48 hrs
- All patients were admitted to the CCU and closely monitored by continuous ECG and BP.
- Primary endpoint: time to the last occurrence of an arrhythmic event (VT or VF) requiring ICD intervention for termination.
- Secondary outcomes: event rate (events per unit time), the proportion of patients that remained free of VT or VF at pre-specified time points, the total number of ICD discharges, and the hospital length of stay.
- No significant differences were found between the 2 groups in terms of age, sex, previous heart disease, type of arrhythmia, NYHA class, LVEF, number of events, and medications before entering the study.
- Patients treated with propranolol presented a 2.67-times reduced incidence rate of ventricular arrhythmic events compared to metoprolol (IRR, 0.375; CI, 0.207–0.678; p=0.001) and a 2.34-times reduced rate of ICD discharges during their CCU admission (IRR, 0.428; 0.227–0.892; p=0.004).
- At 24 hours, 27 of 30 (90%) patients treated with propranolol were free of arrhythmic events compared to 16 of 30 (53.3%) patients treated with metoprolol (p= 0.03).
- Metoprolol was 77.5% less likely to terminate arrhythmic events compared to propranolol (hazard ratio, 0.225; 0.112–0.453; p<0.001).
- Propranolol-treated patients had a significantly shorter time to arrhythmia termination and length of hospital stay (p<0.05).
The authors of this study combination of oral propranolol and IV amiodarone is effective for management of ES in patients with an ICD. Propranolol is associated with shorter time to arrhythmia termination, lower frequency of ICD discharge, and reduced length of hospital stay compared to the combination of oral metoprolol tartrate and IV amiodarone.
Pharmacotherapy of Electrical Storm and Propranolol
Electrical storm is a life-threatening clinical condition characterized by repeated episodes of VT and VF in patients with ICDs and likely heart failure.2 Management of ES requires a multimodality approach with initiation of specific drug therapies while determining if an intervention is warranted to treat the underlying cause of the ventricular arrhythmia. Triggering factors for ES may include acute myocardial ischemia, catecholamine surge, electrolyte imbalance, new or worsening heart failure, QT prolongation, susceptible genetic substrates, or inherited arrhythmia syndromes. Timely administration of beta blockers, amiodarone, and sedatives will suppress sympathetic tone, increase VT/VF threshold, and alleviate patient anxiety. If pharmacologic sympathetic blockade is not effective, interventional treatments (i.e. cardiac cath, ablation, ECMO, LVAD) may be required during the acute event of ES to treat the underlying problem.2
In the early 1980s propranolol received massive attention from the Beta-blocker Heart Attack Trial (BHAT).3 Propranolol's protection against catecholamine toxicity resulted in improved survival by decreasing reinfarction and VT/VF occurrence in patients with an acute MI. Patients with LV dysfunction had an immediate survival benefit observed with propranolol. The steering committee stopped the trial early because of the overwhelming survival benefit in the control arm. Propranolol paved the way for more beta blockers to reach the market. The use of propranolol has decreased with the availability of newer beta blockers.
Overall the unique pharmacokinetic profile of propranolol likely contributes to the clinically meaningful outcomes in ES compared to metoprolol. Chatzidou, et al demonstrated intriguing results in their well-executed study design. Propranolol established superiority over metoprolol for the primary and secondary endpoints. By blocking both beta-1 and beta-2 receptors, propranolol may provide more complete protection against adrenergic surge in addition to its under appreciated antiarrhythmic mechanisms. It remains unclear whether patients would beneﬁt from long-term propranolol after the acute episode of ES.