8pm one ecg sinus arrhythmia long qt interval next morning 10am sinus rhythm probable left atrial enlargement symptoms include shortness of breath, dizziness, chest pain, sometimes nausea and palpitations, thyroid hypertension normal w medication?

You need to see your MD or a Cardiologist for proper diagnosis and treatment

Question confusing. QT interval varies with rate and your question does not mention whether the QT was prolonged in both ECGs. Same question applies to "left atrial enlargement" which should be seen in both ECGs if real. Symptoms also confusing. You need a full discussion with your doctor as to the significance of your symptoms and the variability in the ECG findings if any. Good luck.