"Heart Attack" is the group's most successful song to date. It was the 19th biggest-selling song of 2015 in South Korea, with 1,187,652 downloads. The song has been downloaded over 1,680,000 times as of February 2017.
The title track was also recorded in Japanese and Chinese versions, released in July 2015 respectively as the group's third single in Japan and as a digital single in Chinese-speaking countries.
Two other songs of the album have been released in Japanese versions: "Luv Me", available on Ace of Angels; and "Really Really", featured on "Good Luck".
