Only - blockers significantly increased the irregularity of the RR series ( as an example , ApEn : baseline 1.86 0.13 , carvedilol 1.92 0.09 ; P < 0.05 vs. baseline , metoprolol 1.93 0.08 ; P < 0.05 vs. baseline , verapamil 1.86 0.22 ns , diltiazem 1.88 0.16 ns ) .