"Heaving a sigh of relief" is a common phrase used to convey a sense of relief or contentment after a difficult situation has been resolved. However, there are many similar phrases that can be used in its place, such as "breathing a sigh of relief", "letting out a sigh of relief", "exhaling a sigh of relief", or "sighing with relief". Each of these phrases can be used interchangeably to convey the same emotion and sentiment. Choosing the right synonym depends on the context in which the phrase is being used and the overall tone of the message being conveyed.