Incidence of No Culpirt Lesions and Other Key NACMI Findings Early in the COVID pandemic last spring, cardiologists on social media shared a large number of PCI cases where a COVID-positive patient going to the cath lab with STEMI showed no culprit lesion blockages in their coronary arteries, which is usually the main cause of STEMI. There was speculation as to what the actual percentage of these presentations were, with estimates at 50 percent or more. The NACMI registry found it is lower than originally expected, but still high, at about 20 percent. Dehghani said in pre-pandemic times, this would have been classified as a "false STEMI activation" which occurred in 3-5 percent of STEMI cases.