Coronary Artery Involvement in Children With Kawasaki Disease, just published in this month's Circulation, contains a Z-Score gem: updated prediction equations for coronary arteries. These new prediction equations provide one major advantage over the equations of de Zorzi et al.: they account for the tendency towards non-constant variance, i.e. heteroscedasticity. It is interesting to note that, based on prior work in 2005, one might have expected the prediction equations to be linear regressions based upon the square root of body surface area (BSA raised to the 0.5 power). Instead, the prediction equations are nonlinear and relate to the BSA raised to the 0.3xxx power...
Perhaps the coronary artery system is different enough in structure and function that it does not obey the same rules for parent/daughter vessels in the remainder of the arterial tree. On a more practical note, the authors excluded the left main coronary artery from their analysis, noting:
normal anatomic variations make its interpretation less reliable
The normal variation of the coronary arteries includes such arrangements as left-dominant and right-dominant systems, long and short main coronary artery segments, and even separate origins of the circumflex and anterior descending coronary arteries, to the exclusion of the left main altogether. I doubt that this point gives us a hall pass to abandon measuring the left main coronary artery in our Kawasaki patients, but it is certainly an important observation.
Check out the new and improved Kawasaki Disease Coronary Artery Z-Score calculator here: