A cardiac device and method for detecting QRS signals within a composite heart signal of a body including providing at least two input heart signals via at least two separate input channels, wherein each of the at least two input heart signals is recorded by pairs of sensing electrodes that have one electrode in common and provided coincidental in time. The cardiac device and method include generating estimated signals from the input heart signals, combining the input heart signals and the estimated signals to a combined input stream (SECG), and detecting the QRS signal by comparing the combined input stream (SECG) to an adaptive detection threshold (ATHR) which adapts throughout time.