Compared with the 16 % overall 90-day AF detection rate , the probability of AF increased from < 9 % among patients with < 100 APBs/24 h to 9 % to 24 % in those with 100 to 499 APBs/24 h , 25 % to 37 % with 500 to 999 APBs/24 h , 37 % to 40 % with 1000 to 1499 APBs/24 h , and 40 % beyond 1500 APBs/24 h.