Underwent PTCA, Stenting Of Vessels, Angiography Revealed Distal End Occluded And ECG Showed T Waves In Lead. Explain Chest Discomfort

In 2008 My Dad underwent PTCA and stenting for 2 vessels and PTCA only for one vessel in an Egyptian hospital. He felt much better afterwards but developed a relapse of symptoms three months later. He was then referred to India where a repeat angiography revealed that the distal end of one of the stented vessels had occluded.  His medical treatment was optimised and he was told to return for coronary artery bypass surgery or a repeat PCTA with stent whenever he observed a symptom relapse.
He did fairly well on the optimised medical therapy until the past few months when he discovered he had occasional chest discomfort. We went to see a Cardiologist and test revealed; Rest ECG showed inverted T waves in lead 1, aVL, V2 and V3. Fasting blood sugar, uric acid, serum electrolytes, urea and creatinine were all within acceptable limits. Echocardiography showed normal sized wall with uniform contraction, good systolic but impaired diastolic function. The serum lipid profile was unremarkable.
He was maintained on the optimised medical treatment as prescribed in India and was advised to visit the Indian hospital again.

MY QUESTION IS THIS; is it safe to undergo a repeat of the stenting or is a bypass now necessary?