Tricuspid Regurgitation with L-atrium dilation

My research = tricuspid regurgitation results in RIGHT atrium enlargement/dilation; however, my ecg = tricuspid regurg w/ LEFT atrium dilation and I cannot find any presentation of this combination.  I understand L-atrium dilation is often misdiagnosed due to limitations of ecg and axis/angles.  SX=chest discomfort, tightness, shortness of breath.  Hist=asthma, asthmatic bronchitis - few episodes of pneumonia & pleurisy, celiac disease w/dermatitis herpetiformis.  I'm 48/female/no previous heart issues.  Fam His = father/stroke (aneurysm), high BP; mother A-Fib, high-BP.  Went to ER 2 wks ago for severe shoulder pain - felt like pleurisy episode, but I never had pleurisy pain in shoulder before.  ER MD suspected pulmonary embolism (D-Dimer = 4x normal elevation), but none indicated in chest CT Scan (which did indicate "no pericardial effusion noted. . . ateletatic change in lungs . . . plate like densities at lung bases & left lobe with possible scarring."  The CT also suggested possible pericardium thickening which is why primary care MD ordered ECG.  Interestingly, my BP is normal, but keeps getting lower.  Usually I'm 119 over something, but since ER visit BP was 95 over something at my GI-guy MD and then 80 over something at pri-care MD.  I would appreciate input!  Thanks, Kathie