What is best explanation for new lqts (age 70s), no medications involved, previous normal ecgs, no family history of sudden death -- only new event severe abdominal distension?

Try not to use abbreviations in medicine. LQTS can mean many things.

What was the QT interval and how was it measured. QT intervals are sometimes difficult to measure accurately since the landmarks on the ECG may not be clear. Also QT intervals are are affected electrolyte levels ( low plasma calcium, potassium etc) and medications. Your doctor may be able to answer these questions and I would urge you to seek his help.