how many by-passes needed

[ellisgareth]

does a 50% blockage in 3 and one of 70% require one or more by-passes

[ed34]

It depends on how your cardiologists views it. The 50% blockages would under normal circumstances be left alone, but it may be decided to bypass them 'in case' they get worse. One bypass is one grafted vessel. So if three vessels are grafted onto the native coronary arteries, this is a triple bypass. For three blockages, this depends where they are, and possible where you are. For example, if there is a blockage in the LAD, the UK tends to have a standard rule which states 2 vessels should be grafted. One to the area below the blockage and another further down the vessel. This is to lower the risk with grafted vessels closing down affecting the LAD. Other arteries will normally have one vessel grafted below a blockage.
With the case you state, wih 3 50% blockages, I would be surprised if they are not stented unless in small vessels.
So, 3x50% + 1X70% would require 4 bypass vessels = quadruple bypass.
If one is the LAD, then add another one to that.