Increasing collateral flow

I am a 70 year old male.   17 years ago had angiogram/plasty  which went badly resulting in emergency  bypass .  8 years ago had heart attack, treated with 3 days on heparin.   4 years ago had partial colectomy  and  6 months chemo.  Have  peripheral neuropathy in legs and hands from FOLFOX.
For the last 6 months I have been very fatigued  after little exercise.  Mostly sedentary and 30 lbs overweight.  Blood pressure good but slow pulse and can't take beta blockers. Ongoing meds: Lipitor 20mg (cholesterol levels pretty good), Xanax 0.25mg, Aspirin 81mg, Melatonin 3mg, Zolpidem 5mg
Recent Tests:  Stress echo:  during static test the technician said my heart looked better than it did 2 years ago.  During the treadmill looked good but heart started acting up when I got back on the table.
Bilateral Lower Extremity Arterial Duplex:  distal abdominal aortic aneurysm 6cm x 3.5 cm AP.   ABI's right 0.9 left 1.2.  Moderate plaque in aorta.  Apparently nothing serious per family GP.
Angiogram:  Cardiologist said bypass was blocked and the original block still there but  I had significant collateral growth keeping my right side going  except under load which probably accounts for my fatigue.  Two approaches; medication or an angioplasty to try to open the 17 year old blockage.
He has put me on Diltiazem ER 120mg LM.  I have only been on it for a week, my blood pressure is averaging about 100/60 pulse 50bpm.  Haven't noticed any  change in my fatigue .
Questions:  Does this treatment seem reasonable and how soon would you expect noticeable changes if they occurred?   Any other meds that might be tried or other advice?  Does continued dilation of the blood vessels eventually stretch them or do they relax back when medication stopped?
Is angioplasty on the old artery reasonable and does it have significant chance of success?
Have you seen this done/work?  Is there significantly more danger than the usual angioplasty?
Thank You

[Cleveland Clinic]

You forgot to mention what you heart systolic function is: is it decreased or normal. This is important because with a normal ejection fraction and no significant ischemia there may not be much to be gained by the risky angioplasty. We have several cardiologists who perform this sort of difficult intervention at the cleveland clinic: Dr. Whitlow,Dr. Franco and Dr. Kapadia being among the best known and most successful, and if you want their opinion feel free to schedule an appointment.
In addition to your medical therapy a long acting nitrate such as imdur or isordil, as well as increasing the aspirin to 325 daily.
Your fatigue may be related to your slow heart rate. Has anyone thought of placing a holter monitor to see if you suffer from chronotropic incompetence, and perhaps could benefit from a dual chamber pacemaker?

[sammacel]

From memory my blood pressure readings have been in the range of 120-130/70-85 for years.  Nurses usually say it looks good when they measure it.  The 100/60 average has been since I started taking Diltiazem although today (3 measurements) it is averaging 112/65 and pulse of 48.  The stress echo operator estimated my ejection fraction at 50%.  My GP doesn't think I am a candidate for a pacemaker but perhaps I'll talk to him again.  Why would angioplasty be risky?
Thanks

[gman2009]

Have you talked to your cardiologist about EECP therapy?  Also, you may be a candidate for a study (not sure if they are still enrolling or will be enrolling) at the Texas Heart Institute where vessel growth factor is used to increase collateral growth.

[sammacel]

I will talk to my cardiologist about EECP although I have a feeling my insurance wouldn't cover it.  I'm in Calif so the Texas trial may not be for me but I'll look for it.
Thanks