Precordial thump for cardiac arrest is effective for asystole but not for ventricular fibrillation.
Madias C, Maron BJ, Alsheikh-Ali AA, Rajab M, Estes NA, Link MS. Precordial thump for cardiac arrest is effective for asystole but not for ventricular fibrillation. Heart Rhythm. 2009 Oct; 6(10):1495-500.