PROLONG Study ICD Monitoring Algorithm

PROLONG Study ICD Monitoring Algorithm: Explanation and Clinical Context The PROLONG study examined patients with newly diagnosed heart failure and an initial left ventricular ejection fraction (LVEF) ≤35% who were protected temporarily by a wearable cardioverter-defibrillator (WCD) while guideline-directed medical therapy was initiated and optimized. The study defined criteria under which prolongation of the WCD wearing period — rather than immediate implantable cardioverter-defibrillator (ICD) implantation at 3 months — could be considered: (1) an LVEF of 30–35% at the 3-month re-evaluation, (2) an increase in LVEF of ≥5% compared with the previous visit (indicating a trend toward recovery), or (3) heart failure medication that was not yet optimized. Applying these criteria permits continued protected observation and intensified therapy to allow late left ventricular reverse remodeling and may reduce unnecessary ICD implantations in patients who recover LVEF beyond the 3-month mark.

Clinical judgment is required: patients with persistent LVEF ≤35% without the PROLONG indications should proceed to guideline-directed consideration of an ICD, whereas patients showing improvement or incomplete optimization may benefit from prolongation of the WCD and repeat reassessment.