What causes spontaneous dissection

Thank you for this forum.  My background: age 66, 6' 2", 199 pounds, try to exercise daily, either swimming, walking or light weight training.  I've had two heart attacks affecting the bottom area of the heart on both the LAD and RDA side, I'm told.  I have six stents, two in the LAD, four in the RDA.
My last stent was in May.  In September I started experiencing SOB symptoms plus chest discomfort when exercising and reported it to my doctor's office at once.  Quickly I was brought in for a stress test, but it was stopped after 45 seconds in the second stage.  I was sent to the hospital for a Cath, and it revealed a Spontaneous dissection of the right coronary artery, very close to where the stent was placed in May.  Fortunately, the artery wasn't completely split, but I had a long fracture of the interior of the artery, and a 25 mm non-coated stent was installed.  My question: what would cause this dissection?  I'm told it is a rare event, but I wonder if it happened once, am I prone to have this problem again?  The operative report mentioned 'Distal spasms' during the procedure.
I'm working out again aerobically at a hospital rehab setting and seem to be doing OK.  I take Altace, Coreg, Vitorin, 81mg aspirin and Plavix.  My cholesterol level is now perfect, and my diabetes is well controlled.  However, I'm used to worrying about blockages, not ruptures and hope that this was a lightening strike, so to speak.  Thanks again for this forum.

[Douglas Bogart, MD]

Spontaneous coronary artery dissection is a relatively rare event.  It can occur during pregnancy and is  a cause for heart attack in this group.  It can also occur with very vigorous exercise.  It has been reported in patients with collagen vascular disease like lupus.
In your case I would wonder if the stent which had been previously placed had a tethering effect on the right coronary and produced the dissection.. I hope this is of help.

[ireneo]

Good morning Flycaster - I'm interested to see what the doctor's answer may be. I suppose he can't give you specific odds but if you knew what caused such a strange thing, then you could try to avoid a repeat.  I've heard of of arteries splitting but never just a "fracture" as you called it. I'm glad it didn't break all the way through (I'm sure you are too).

[celebrie]

A related discussion, spontaneous coronary dissection was started.