Academic Emergency Medicine has a free article on sonographic detection of submassive pumonary embolism, with three video clips.
One of the videos shows a nice demonstration of the McConnell sign (RV mid-segment dilation with apical sparing), which has been reported to be specific for (sub)massive PE. According to this article however, it has been reported that the McConnell sign is present in two thirds of patients with RV infarction and is only 33% specific for PE. Continuous wave Doppler helps differentiate RV infarction from submassive PE by demonstrating an increased tricuspid regurgitation RA-RV pressure gradient in submassive PE and a normal or low gradient in RV infarction.
The full article is available here