Ventricular Fibrillation Cardiac Arrest

A 58-year-old man with hypertension, hyperlipidemia, and active smoking presents with 45 minutes of substernal crushing chest pain radiating to the left arm with diaphoresis. ECG shows 3 mm ST elevation in leads II, III, and aVF consistent with acute inferior STEMI. While being transferred to the catheterization laboratory, he suddenly becomes unresponsive with absent central pulses. The rhythm strip shown demonstrates the pattern marked **C**: a coarse, chaotic, irregular baseline with no discernible P waves, no organized QRS complexes, and no T waves. High-quality chest compressions are initiated immediately at 100–120 compressions per minute with 5–6 cm depth and full recoil. According to AHA 2020 ACLS guidelines, what is the FIRST definitive intervention for the rhythm shown at **C**?