With CHF or R sided heart failure, you'll have bil extremity edema due to back up from the heart into the venous system. Here, only one leg is edematous, and that's due to a DVT. A mild PE could show diffuse EKG changes potentially, while CHF or cor pulmonale could show more MI-like EKG changes if cardiogenic in nature. Also, + Homan's is pain in the calf with dorsiflexion while the knee is extend, which increases suspicion for DVT. Cor Pulmonale and CHF are usually slower onset as a result of other heart problems, which this case is acute in nature. If the CHF is due to an MI damaging the heart, for example, you'd have EKG changes showing an old MI and he would probably have a history of MI's on record. This pt has no prior health problems or medications to speak of. And the most common cause of right sided heart failure, is left sided heart failure, so he would have experienced symptoms of left sided heart failure prior to this episode; again, more chronic heart problems vs acute. The pleural effusion is also unilateral, increasing suspicion for a source at the lung itself. CHF would likely result in diffuse pleural effusions.