He isn`t lose his heart.是错句子.因为lose是动词 前面只能用didn't,不能用isn't.
简单的说,句子里已经有了动词作谓语,就只能用didn't,因为didn’t不是动词.只用句子中没有了动词作谓语,例如只有名词,形容词等,则用is或isn't作为系动词,使句子完整,例如 He isn't a handsome guy.