Thank you for your query. A D-dimer level of 570 ng/mL is generally considered elevated, as the normal cutoff is typically below 500 ng/mL.
Given your symptoms of breathing issues and chest pain/tightness, an elevated D-dimer is a finding that needs to be taken seriously, as it can sometimes indicate the presence of a blood clot, such as a pulmonary embolism (a clot in the lungs). While your ECG and Echo were normal, these tests do not definitively rule out a pulmonary embolism.
Next Steps
I advise you to seek medical evaluation, they will likely recommend further test as its important to rule out this condition.