This patient has major depressive disorder: loss of interest/anhedonia (need to have this or depressed mood),sleep problems, weight changes, decreased energy, thoughts of death. Meets criteria because > 2 weeks timeframe. SSRIs are first-line; paroxetine is in this category. SSRIs also help with weight gain - might be an added benefit if the patient is underweight.
The cardiac stuff might have just been a distractor, except that you probably wouldn't want to give tricyclics (i.e. amitriptyline) since they have pro-arrhythmic side effects. Patient probably has prolonged PR interval due to beta blockers.