Another Good Reason to Consider Early Ablation for Ventricular Tachycardia
April 1, 2017 4 minutes read
By Joshua D. Moss, MD
Associate Professor of Clinical Medicine, Cardiac Electrophysiology, Division of Cardiology, University of California, San Francisco
Dr. Moss reports no financial relationships relevant to this field of study.
SYNOPSIS: In a retrospective cohort of patients with structural heart disease and ventricular tachycardia, amiodarone often could be safely reduced or discontinued after ablation.
SOURCE: Liang JJ, Yang W, Santangeli P, et al. Amiodarone discontinuation or dose reduction following catheter ablation for ventricular tachycardia in structural heart disease. J Am Coll Cardiol 2017. Published online while in press.
Ventricular tachycardia (VT) is common in patients with left ventricular (LV) dysfunction and often is treated with antiarrhythmic drugs, in part to prevent the discomfort and morbidity associated with ICD shocks. Amiodarone is the most effective and widely used medication but is associated with significant toxicities.
Cardiologists at the University of Pennsylvania sought to determine whether VT ablation could facilitate safe reduction or discontinuation of amiodarone. In a cohort of 231 patients with structural heart disease referred between 2008 and 2011, VT ablation was performed using standard techniques. Many patients (55%) were on amiodarone shortly before the ablation procedure; of the rest, 33% had amiodarone discontinued remotely for toxicity. Ablation success was judged in part by attempts to induce VT at the end of the procedure with programmed stimulation (if the patient was believed to be medically stable). Many patients also were subject to repeated testing for inducible VT performed via their implanted ICD several days later (non-invasive programmed stimulation, or NIPS). Treating clinicians made decisions about post-procedure antiarrhythmic drug therapy, including amiodarone, based on these results and other factors.
The authors divided patients into three groups retrospectively: those who had pre-procedure amiodarone dosing reduced or discontinued after ablation (n = 99), those who had pre-procedure amiodarone dosing maintained or increased after ablation (n = 29), and those who were not on amiodarone immediately pre-procedure (n = 103). Patients who had pre-procedure amiodarone dosing maintained or increased after ablation tended to be both older and sicker, with lower ejection fraction (EF), more heart failure medications, more biventricular ICDs, and more inducible VT — even after ablation. There was no significant difference in one-year VT-free survival among the three groups despite the differences in post-procedure amiodarone use. A multivariate analysis was performed, incorporating a wide variety of clinical factors, including EF, severity of heart failure symptoms, common comorbidities, medications, arrhythmia characteristics, and procedural findings. The only independent, significant predictor of shorter time to VT recurrence post-ablation was whether a clinically important VT could be induced during post-procedure NIPS. Mortality was 80% in the group with maintained or increased amiodarone dosing over a mean of 1.8 years, significantly higher than in the other groups. The authors concluded that after successful VT ablation, as confirmed by noninducibility at the end of ablation and NIPS, amiodarone may be safely reduced or discontinued without an unacceptable increase in VT recurrence.
COMMENTARY
The risks of long-term amiodarone use are well-known and dose-dependent. There also is evidence that it may be independently associated with higher mortality in some groups, though it can be difficult to prove it is not simply a marker of more advanced disease. Nevertheless, it can be effective for suppression of ventricular arrhythmias, and once a patient starts a course of medication for VT, it can be difficult for his or her clinicians to consider reducing or discontinuing it. Although it seems inherently logical that VT ablation should facilitate decreased amiodarone use, this hypothesis had not been formally studied. If a patient undergoes complex VT ablation at a tertiary care center and is referred to their primary cardiologist for post-ablation management, the appropriateness and timing of amiodarone dose reduction may be ambiguous. Fear of recurrent arrhythmia and ICD therapy undoubtedly leads both providers and patients to err on the side of caution.
This study adds valuable evidence to support a more aggressive approach to reducing the use of this potentially toxic medication after ablation at an experienced VT treatment center. Patients were not at higher risk for recurrent VT or, importantly, appropriate ICD shocks in the year after their ablation procedure, regardless of whether amiodarone was maintained, reduced, or discontinued. Patients who were maintained on a stable or higher dose of amiodarone experienced significantly higher mortality.
There are important limitations that must be considered when drawing conclusions from the data. Despite careful efforts to perform multivariate analysis, in a retrospective, observational study such as this, there are almost certainly other unmeasured confounders that influenced post-procedure amiodarone dosing and mortality. Only a prospective, randomized trial of amiodarone dosing after an ablation procedure with strict pre-defined endpoints for success will help clinicians answer the question.
For now, cardiologists should carefully consider with their patients the potential risks and benefits of ablative therapy (including the potential for reducing amiodarone exposure) for any episode of VT. It has been demonstrated that patients referred for ablation later in their arrhythmia course tend to take higher doses of amiodarone than those referred earlier, and even a single arrhythmia episode should prompt a discussion of VT ablation. Also, electrophysiologists performing these often-complex procedures should maintain an open dialogue with the cardiologists charged with the patients’ long-term care, so that procedural success and medication strategies post-procedure are understood and agreed upon. Efforts to stop amiodarone or transition to another antiarrhythmic drug with less toxicity such as sotalol may pay significant dividends in the long term.
In a retrospective cohort of patients with structural heart disease and ventricular tachycardia, amiodarone often could be safely reduced or discontinued after ablation.
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