Dyspnea and Intermittent Chest Pain in a 64-year-old Woman

Video: Patient's ADLs were unaffected by symptoms until 2 days ago. She arrives at ED directly from PCP's office, after echo. Dx?

 

A 64-y/o woman is referred to ED immediately after office echocardiogram. Complains of ~5 weeks occasional shortness of breath, intermittent mild pain radiating from L shoulder to chest. ECG 3 wks ago, normal. HR: 99 bpm, RR: 23, BP: 139/66, SpO₂: 90% RA.

 

What is the most likely diagnosis?