In ALS version 5.4, the medical cardiac arrest directive talks about DSD or VCD for refractory VF or pulseless VT. It defines refractory as persistent VF or pulseless VT after 3 consecutive shocks. Does each of those 3 shockable rhythms have to be only VF or only pulseless VT or could those 3 consecutive shocks have been from a mixture of VF and pulseless VT? Essentially is any sequence of 3 consecutive shockable rhythms grounds to perform DSD or VCD?