<s>[INST] I had an angiogram yesterday and was diagnosed with chronic blockage of the right coronary artery . The interventional cardiologist stated approx. 64 cm. of the bottom of the artery was completely blocked. He stated that a by-pass was to risky and he would not consider a by-pass as an option. Can you explain to me the seriousness of this type of blockage? [/INST] What you describe is chronic total occlusion of mid to distal RCA, two important branches PDA (posterior descending artery) and Pl (poster lateral) arises from it.  They supply Inferior and posterior wall of heart and some part of the septum.  The best part of such lesions are that good collateral s From the left side of the heart provides enough blood to these areas to prevent any kind of damage to heart muscle. Now why bypass in not a good option?  The distal vessels and small caliber vessels so putting a graft there in more probability the grafts will get closed in small while, and we are to square one. Options : get a thallium, if the area is well perfused, only medical management to optimize the heart condition and prevent further damage. If their Id ischemia in the region of supply, try opening it up by angioplasty, the results of which can only be told after opening up the block and seeing the condition of distal vessel However as I said there are good collateral in such cases and medical treatment is optimum for most cases Regards Chat Doctor.  </s>