<prompt> Patient is having normal CK CKMB after 2 days of chest pain which of the following is true-Excludes diagnosis of MIReperfusion after MIExtracardiac source of painCardiac surgery  <response>: A significant concentration of CK-MB isoenzyme is found almost exclusively in the myocardium, and the appearance of elevated CK-MB levels in serum is highly specific and sensitive for myocardial cell wall injury. Normal reference values for serum CK-MB range from 3 to 5 percentage of total CK or 5 to 25 IUL.if theses are normal then the MI diagnosis can be excluded Ref Davidson edition23rd pg 440 