Abstract 1662: Arrhythmic Events During the 40/90 days “Cooling Off” Period: Clinical Utility of the Wearable Defibrillator
Background: A “cooling off” period (COP) of 40 days after MI and 90 days after coronary revascularization or non-ischemic CM (NICM) diagnosis is customary to allow clinical improvement prior to assessing the need for ICD implantation. The COP creates a clinical dilemma that requires balancing ongoing sudden death (SD) risk and the cost of potentially unnecessary ICD implants. We reviewed our wearable defibrillator (WD) experience to assess its clinical utility during this period of uncertainty.
Methods: Medical records from 27 patients with EF≤35% requiring a COP who were offered WD (LifeVest, ZOLL Lifecor) were reviewed for clinical indication, EF before and after WD use, sudden cardiac arrest (SCA) or treated VT/VF, and subsequent outcome.
Results: Wearable defibrillator indications were: recent MI (n=7), ischemic CM (ICM) with recent revascularization (n=10), untreated NICM (n=9), and tachycardia-CM (n=1). Twenty-five of 27 patients agreed to WD and 23 complied. Two patients had 3 clinical events: 1 (not wearing WD) was resuscitated from SCA; 1 (treated by WD) survived sustained syncopal VT/VF but later died suddenly not wearing the WD. One patient was shocked for AF. After the COP (n=24), 6/24 (25%) patients had EF>35% (3 ICM and 3 NICM) and no ICD was implanted. Eighteen of 24 (75%) had an EF ≤ 35% and received an ICD. Three of 24 (12.5%) patients that received an ICD ultimately had an EF ≥35% over continued follow-up.
Conclusions: During the COP, patients with EF ≤ 35% had a 12% clinical event rate (3 events in 25 patients). WD protected patients during this high-risk period but non-adherence was associated with death/cardiac arrest. While ICD implantation was safely avoided in 25%, unnecessary ICD implantation still occurred. Prolonged WD therapy beyond the COP may be more prudent in some to observe for delayed recovery (12%). In patients with newly diagnosed LV systolic dysfunction or after revascularization, risk and recovery are in flux. We suggest that this continuum is not confined to the COP. In patients with low EF, prolonged application of WD may provide additional SD prevention beyond the initial high-risk period and may prevent unnecessary ICD implantation.