Instinctively, what makes er and cardiologists suspicious that gerd related symptoms are just that as opposed to cardiac issues?

Let me explain: People who have had a heart attack in the past may not realize they're having another, sudden pressure, tightening, squeezing or crushing pain in the center of the chest that lasts more than a few minutes, shortness of breath, pain or discomfort spreading to the back, neck, jaw, stomach, shoulders or arms — especially the left arm, chest discomfort accompanied by sweating, lightheadedness.