Total coronary artery occlusion is a common finding in CAD especially in chronic stable angina. Normal coronary blood flow is 5 % of cardiac output that amounts to 250-300ml/mt.At an average heart rate of 70/mt , each beat injects about 5cc blood into the coronary circulation.This is shared between two coronary arteries. This means , only few CC (2-3cc) of blood enters each coronary artery with each cardiac cycle .
When one of coronary artery is totally occluded what happens to the coronary
blood flow ?
A.Total coronary blood flow can be be maintained normal at rest as it forms only about 5% of cardiac output (or it is only slightly reduced )
B. It is believed , the unobstructed coronary artery could receive the blood meant for the contralateral coronary artery. This possibly explains the increased coronary artery diameter in the non obstructed artery.
C. It’s nature’s wish , that the contralateral coronary artery shall share 50% of it’s blood through collaterals if available.
D.If collaterals are not formed it , the unobstructed coronary artery may be over perfused with double the amount of blood flow.
E. Some times , the collaterals steal much more than what the obstructed coronary artery deserves and make the feeding coronary artery ischemic. This is many times observed in total RCA occlusion with well formed collaterals from LAD/LCX.
F.The collateral flow in CTO also depend on whether flow is directed from LAD system to RCA or from RCA -LAD system. The LAD is better placed to assist RCA than vice versa.This is for two reasons.1.LAD blood flow is higher than RCA so it can share it.2.The driving pressure is more from LAD -RCA , as RCA can receive blood flow even during diastole .
F.During exertion , the coronary hemodynamics become further complex.The collateral’s are traditionally thought to be less than adequate during times of exercise.But it is more of a perception than solid scientific data.This rule may be applicable in only certain group of patients. We know CTO patients with very good exercise tolerance who have documented collateral’s.
G.Collaterals can be either visible or invisible by CAG. The strength of collateral circulation is not in it’s visibility but it’s capacity to dilate and respond to neuro humoral mediators at times of demand. Currently , there is lot to be desired regarding our knowledge about the physiology of visible collaterals , no need to mention about invisible collaterals !
Final message
The above statements are based on logics and observations .
Is it not a irony in cardiac literature , where thousands of articles are coming out every month to tackle totally occluded coronary artery(CTOs) , there is very little data regarding the coronary hemodynamics in chronic total occlusion . How does a patient with CTO can manage a active life with only one functioning coronary artery ?
Dr.S.Venkatesan MD 
I am laying in a hosptal bed in henderson nv I have a 100% occlusion in the LAD. I am awaiting CABG and wanting to know why?
I am active,teach scuba diving, work a 40 hour a week job,travel and have a normal life with out any typmtoms aside from high cholesterol,trygycerides and a bad family history of heart disease…..I’m 57 HELP!!!!!!!!!!!!!!!
Hi
Your case is the typical example for anatomy-physiology dissociation.In spite of 100 % occlusion you are able to do strenuous activity that includes scuba diving !
So according to me there is not much to improve upon your exercise capacity.
This also implies you may have lot of invisible collateral circulation.
But , your cardiologist is the right person to decide what you need.
There is something called open artery hypothesis
which says open artery is always better than closed one even if one is asymptomatic .
But the opposite can also be true , only open artery has a potential to get closed again and produce symptom. A closed artery , if good collaterals are present sans the risk of further occlusion.( Most will ridicule this reasoning , but it remains a fact !)
thank you so very much for the personal response. I of coarse need to decide with 100% on the LAD and 70% on the right and no symptoms I have a diificult dission to make. my boss a very well known neurologist advised me not to take the risk of a CABG. I wish there was a method to measure how much collateral I have.
Jon
Dear Dr Svenkatesan,
Do you see,treat,examine,test patients like myself?
I would come to you in a Heart Beat.
Jon
On Nov 11, I went to Fresno, Ca for a Bypass Surgery with the da Vinci Robot. 6 hour surgery, 2 bypass’s using my own artery’s . 3 day hospital stay, back home in one week,returned to work part time 1and a half weeks after 2 way bypass. 10 weeks later AMAZING!!!! Dr Bolton was my surgeon. Saint Agnes Hospital in Fresno.
Jon Dembo
joncht@gmail.com
Dear Mr. Jon Dembo
You are asymptomatic because of good collaterals to occluded LAD from RCA. However RCA has 70% occlusion. You do not have symptoms at present, because LAD after occlusion receives blood from RCA. So LAD depends on RCA, but RCA has disease. If disease in RCA progresses or gets occluded, a major portion of heart muscle will be at stake which is supplied by both RCA and LAD. It is risky to leave the lesions as such. CABG is the best option in this situation. Accept the decision for CABG. In good hands the risk of surgery is negligible.
Wish you all the best.
Dr. G. Gnanavelu
Thanks a lot Doctor S Venkatesan, and Dr G Gnanavelu, I am now clear about a lot of medical stuff regarding my 90% restenosis (near the mouth of earlier stent) of proximal LAD.
I had PCI for the three vessel disease after an MI four years ago.
I am asymptomatic, and following my Yoga, walking and mild exercise routine. I also take all medicines religiously. My cholesterol levels are very good, and I am avoiding fats in food.
My MD told me one year ago that PCI is required but would be a difficult one, using a rotablator. I am avoiding this procedure and wonder about any additional benefits of revascularisation by PCI.
It has been one year since the last angiogram and advise of a PCI. Do you suggest a CT angiogram now, or any other intervention, or to continue a status quo. Is it a big risk I am carrying of an MI or arrythmia or sudden cardiac arrest?
Many thanks and warm regards
How to track performance of collaterals in CTO case ? Can we say St depression point above 5min is a reliable measure ?