The relevance of platelet and fibrin thromboembolism of the coronary microcirculation, with special reference to sudden cardiac death.

The coronary microcirculation was examined for platelet and fibrin thrombi in hearts from 21 normal subjects and 244 cardiac patients, including 168 with ischemic heart disease (IHD) and 76 with other types of heart disease. Seventy-seven cases were sudden cardiac death (SCD). No microthrombi were present in any of the normal hearts, whereas platelet and fibrin thrombin were present in the coronary microcirculation in 32 of 244 cardiac cases (13.1%), including 19 with IHD and 13 with other types of heart disease and after cardiac surgery. The microthrombi were either embolic or represented in situ thrombosis, depending upon the underlying pathologic process. There was no significant difference in the incidence of microthrombi in SCD patients, with IHD (10 of 50, 20%) compared with patients who survived longer (nine of 93, 10%). In SCD patients, however, platelet microthrombin were more frequent in patients less than 45 years of age compared with those older than 45 years of age (p = 0.0002). We concluded that coronary microcirculatory thrombi are not uncommon in heart disease. A subgroup of SCD in young patients with IHD has been identified in whom microcirculatory platelet thrombosis is the main cardiac pathologic process. The significance of this process is emphasized by the associated myocardial damage.