Translation:The blood vessel is very long.
In order to understand that someone was saying "it is a heart long" -- it's a little odd to understand even in English--I think they'd have to say juvlu'DI' tIq 'aD but even then I'd probably read it as It was measured to be the vena cava (i.e. the vein of the heart), and ask for clarification. juvmeH tIq lo'lu'chugh wa' tIq 'aD.
Cool observation. I wonder if Marc knew/noticed/intended it.