My patient has to under go CABG and surgery for abdominal aneurysm simultaneously.is it life threatning?

He is 70 years old and has been diagnosed with a triple artery block. He also has abdominal Aneurysm which is 6cm in diameter. Artery blokage is 90% , 85% and 65%. He was brought to the hospital after suffering a heart attack.
He also has a history of nephrotic syndrome

If he's your patient, you should know if it's life threatening.

I recomment Off-pump CABG to the patient.
Abdominal aortic aneurysm has reached dangerous level ie., above 5cm. It is generally indicated in older, high-risk patients or patients unfit for open repair. However, endovascular repair is feasible for only a proportion of AAA's, depending on the morphology of the aneurysm. The main advantage over open repair is that the peri-operative period has less impact on the patient (less time in intensive care, less time in hospital overall, earlier return to normal activity). Disadvantages of endovascular repair include a requirement for more frequent ongoing hospital reviews, and a higher chance of further procedures being required. According to the latest studies, the EVAR procedure doesn't offer any overall survival benefit.
The case may be decided considering other risk factors such as Smoking, hypertension, older age (peak incidence at age 70 to 80), family history (in 15 to 25%), Caucasian race, and male sex.
Please note that I am not a medical professional.
Please see the web pages for more details on Off-pump CABG and Abdominal aortic aneurysm.

ANY surgery is potentially life threatening because of the anesthesia; adding to that the fact that he already had injury to his heart due to the MI, has significant coronary arterial blockage AND has nephrotic syndrome (and is 70), adds to challenge to survive the surgery.

Surviving surgery is no guarantee he'll recover well either. He faces a number of challenges to overcome but the human body is a rather miraculous thing in my estimation. Some people who appear to face a hopeless situation, can and do recover surprisingly well.

Make sure he has lots of emotional and physical support and to know that those around him love and support him. Hold his hand, read to him, and care for him and that will help no matter what his outcome is.

All the best!

I'd be very surprised (from the little you related) if they do the two together. We would normally have the patient undergo CABG, then shortly later, the AAA.

While 6cm is in the "fix it" range, it's not in the "oh @@#" range.
The risk of a short delay in fixing the AAA is outweighed by the benefit of having the CABG done.