Methods and apparatuses, including devices and systems, for remote and detection and/or diagnosis of acute myocardial infarction (AMI). In particular, described herein are handheld devices having an electrode configuration capable of recording three orthogonal ECG lead signals in an orientation-specific manner, and transmitting these signals to a processor. The processor may be remote or local, and it may automatically or semi-automatically detect AMI, atrial fibrillation or other heart disorders based on the analyses of the deviation of the recorded 3 cardiac signals with respect to previously stored baseline recordings.