Z- score classification of coronary aneurysms in Kawasaki disease

Z- score classification of coronary aneurysms in Kawasaki disease

Z-score is the standard deviation from coronary artery internal lumen diameter normalized for body surface area. AHA classification of coronary artery aneurysms based on Z-score is as follows [1]: 1. No involvement with Z score less than 2 always. 2. Dilatation only with Z scores from 2 to less than 2.5 or a decrease in Z score of 1 or more during follow up if it was less than 2 initially. 3. Small aneurysm with Z score of more than 2.5, but less than 5. 4. Medium aneurysm with Z score 5 or more, but less than 5 and absolute dimension less than 8 mm. 5. Large or giant aneurysm with Z score 10 or more or absolute dimension 8 mm or more. The decrease in dimension in Class 2 over time means that though the diameter was in normal range initially, it was actually dilated for that person and decreases in size over time.

A previous Japanese guideline classified coronary aneurysms in acute phase of Kawasaki disease based on absolute or relative internal lumen diameter [2]. In that classification, small aneurysm or dilatation was a localized dilatation with internal diameter 4 mm or less. In children of 5 years or more, internal diameter of a segment measures less than 1.5 times the adjacent segment. Medium aneurysm was with internal diameter above 4 mm, up to 8 mm. In children of 5 years or more, internal diameter of a segment measures 1.5 to 4 times that of an adjacent segment. Giant aneurysm was with internal diameter above 8 mm. In children 5 years or more, internal diameter of a segment measures more than 4 times that of an adjacent segment. This classification is easier to follow as you need not check the nomogram for Z scores each time you do an echocardiographic measurement of the coronary arteries. Disadvantage of course is that the variation in coronary size with age is not fully accounted for.

References

1. McCrindle BW, Rowley AH, Newburger JW, Burns JC, Bolger AF, Gewitz M, Baker AL, Jackson MA, Takahashi M, Shah PB, Kobayashi T, Wu MH, Saji TT, Pahl E; American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee of the Council on Cardiovascular Disease in the Young; Council on Cardiovascular and Stroke Nursing; Council on Cardiovascular Surgery and Anesthesia; and Council on Epidemiology and Prevention. Diagnosis, Treatment, and Long-Term Management of Kawasaki Disease: A Scientific Statement for Health Professionals From the American Heart Association. Circulation. 2017 Apr 25;135(17):e927-e999.
2. JCS Joint Working Group. Guidelines for diagnosis and management of cardiovascular sequelae in Kawasaki disease (JCS 2008)–digest version. Circ J. 2010 Sep;74(9):1989-2020.