Hello,
Thank you for your query at DoctorSpring.com.

Your grandmother has mitral and aortic stenosis. She is 90 your old and diabetic. What is her left ventricular function and ejection fraction like ?
The procedural risk of double wall replacement is around 10 %. The risk may be increased if there are additional comorbidities like reduced left ventricular function and ejection fraction or other comorbidities like renal failure stroke. The risk of surgery is lower if other risk factors are absent and left ventricular function us good.
Old aged people may undergo the surgery if other risk factors are not prohibitively very high. Age Is not a contraindication for doing this surgery.

Less invasive Aortic balloon valvuloplasty is not a great option in old age as the valve will get restenosed soon within 6 months. It it is to be done only if the patient is terminally ill and cannot be sent for surgery because of other commodities. Balloon mitral valvuloplasty is a good option if the mitral valve isn't too calcified or thickened and wilkins score on echo is less than 8. The results stand good for 10 year for mitral valve. If you wish to avoid surgery totally then transfemoral aortic valve replacement or TAVI followed later by Balloon mitral valvuloplasty will be a good option.

Both mitral and aortic valve cannot be treated simultaneously if you are preferring less invasive methods. First treat the aortic then mitral stenosis.

But this is just for the sake of completion of information. If the patient is willing and if 2 valves have to be repaired or replaced if the patient is not terminally sick has good left ventricular function and good renal function and overall reasonable health then the long term outcomes will be good and she shall benefit over 5 to 10 years.

Hope this helps, please feel free to discuss further.
Regards
Dr Vivek Mahajan