PracticeUpdate Cardiology June 2019

EDITOR’S PICKS 9

Improved Survival With Catheter Ablation of Refractory Ventricular Fibrillation Storm After Myocardial Infarction Circulation

COMMENT By Sana M. Al-Khatib MD, MHS T his multicenter, retrospective, observational study reports on the outcomes of 110 patients with post-MI refractory VF storm not preceded by monomorphic VT who underwent catheter ablation of Purkinje- related ventricular extrasystoles triggering VF. Between the ablation and hospital discharge, VF storm subsided in the vast majority of patients; however, 30 patients (27%) died before discharge. After hospital discharge, although the rate of VF storm recurrence was very low (only 1 patient), 29 additional patients (36%) died within a median follow-up of 2.2 years. Although it is important to keep in mind the retrospective design of this study and acknowledge that a randomized clinical trial is the best study design to address the questions at hand, this study has some important implications for clinical practice. First, the success rate of VF storm ablation is notable. Sec- ond, the high rate of in-hospital mortality after ablation for VF storm should be shared with patients (if conscious), their families, and the primary teams taking care of them to ensure that everyone has realistic expectations regarding the impact of VF ablation on in-hospital mortality. Third, the decision regarding whether or not to proceed with ablation has to be made quickly, as this study suggests that a 1-day delay in ablation may be associated with a 10% increase in mortality. Fourth, the rate of mortality within 2.2 years of follow-up is high, with heart failure being a major cause. This underscores the importance of optimiz- ing heart failure management in these patients.

Take-home message • This multicenter, retrospective observational study examined the use of catheter ablation to treat patients who experienced a ventricular fibrillation (VF) storm after myocardial infarction (MI). In the 110 included patients, VF storm occurred close to MI onset in 39% of patients, over 1 week after MI in 44% of patients, and over 6 weeks after MI in 17% of patients. In 80% of patients, the focal triggers originated from the zone bordering the scar. Although the VF storm subsided in 84% of patients during their hospital stay following ablation, 27% died in the hospital. There was an association between greater delay between VF occurrence and catheter ablation and greater in-hospital mortality. Although only 1 patient developed recurrent VF storm after discharge, 36% of patients died during follow-up. • This study suggests that catheter ablation of culprit triggers improves outcomes and is associated with low recurrence in patients who experience VF storm after MI. Abstract

BACKGROUND Ventricular fibrillation (VF) storm after myocardial infarction (MI) is a life-threat- ening condition that necessitates multiple defibrillations. Catheter ablation is a potentially effective treatment strategy for VF storm refrac- tory to optimal medical treatment. However, its impact on patient survival has not been verified in a large population. METHODS We conducted amulticenter, retrospec- tive observational study involving consecutive patients who underwent catheter ablation of post-MI refractory VF storm without preceding monomorphic ventricular tachycardia. The target of ablation was the Purkinje-related ventricular extrasystoles triggering VF. The primary out- come was in-hospital and long-term mortalities. Univariate logistic regression and Cox propor- tional-hazards analysis were used to evaluate clinical characteristics associated with in-hospi- tal and long-term mortalities, respectively. RESULTS One-hundred ten patients were enrolled (65±11years; 92 men; left ventricu- lar ejection fraction [LVEF] 31±10%). VF storm occurred at acute phase of MI (4.5±2.5 days after the MI onset during index hospitaliza- tion for MI) in 43 (39%) patients, subacute (>1 week) in 48 (44%), and remote (>6 months) in 19 (17%). The focal triggers were found to orig- inate from the scar border zone in 88 (80%) patients. During in-hospital stay after ablation, VF storm subsided in 92 (84%) patients. Over- all, 30 (27%) in-hospital deaths occurred. The duration from the VF occurrence to the ablation procedure was associated with in-hospital mor- tality (odds ratio for each one-day increase: 1.11; 95% confidence interval [CI]: 1.03-1.20; p=0.008). During follow-up after discharge from hospital, only one patient developed recurrent VF storm. However, 29 (36%) patients died with a median survival time of 2.2 years (interquartile range: 1.2- 5.5 years). Long-term mortality was associated with LVEF<30% (hazard ratio [HR]: 2.54; 95%CI:

1.21-5.32; p=0.014), New York Heart Association class ≥III (HR: 2.68; 95%CI: 1.16-6.19; p=0.021), a history of atrial fibrillation (HR: 3.89; 95%CI: 1.42- 10.67; p=0.008), and chronic kidney disease (HR: 2.74; 95%CI: 1.15-6.49; p=0.023). CONCLUSIONS In patients with MI presenting with focally-triggered VF storm, catheter ablation of culprit triggers is life-saving and appears to be associated with short- and long-term freedom from recurrent VF storm. Mortality over long- term follow-up is associated with the severity of underlying cardiovascular disease and comor- bidities in this specific patient population. Catheter Ablation of Refractory Ventricular Fibrillation Storm After Myocardial Infarction: A Multicenter Study. Circulation 2019 Apr 01;[EPub Ahead of Print], Y Komatsu, M Hocini, A Nogami, et al. www.practiceupdate.com/c/82025

Dr. Al-Khatib is Professor of Medicine at Duke University Medical Center in Durham, North Carolina.

VOL. 4 • NO. 2 • 2019