Clinical circumstances and the electrocardiogram can provide powerful clues but they are widely ignored. Mistaking PE for ACS or heart failure are well known examples of misdiagnosis. Today's environment of core measures, care pathways and rapid throughput pressures physicians more than ever before to jump to the most superficially apparent cause (troponin positive, thinking stops).
When PE presents with an abnormal ECG and an elevated troponin it is massive or submassive. Nevertheless it tends to be missed. Here is a great post from Dr. Smith which discusses some of the nuances.