IDENTIFICATION OF A SECONDARY PEAK IN MYOCARDIAL-INFARCTION ONSET 11 TO 12 HOURS AFTER AWAKENING - THE CARDIAC-ARRHYTHMIA SUPPRESSION TRIAL(CAST) EXPERIENCE

Objectives. The purpose of this study was to assess the relation betwe en the time of awakening and the time of onset of acute myocardial inf arction. Background. Previous investigation has shown the onset of sym ptoms of acute myocardial infarction to have a primary peak 1 to 2 h a fter awakening. In studies not corrected for time of awakening, there appears to be a late afternoon/early evening peak, but data correlatin g the onset of symptoms with awakening have been limited by small numb ers of patients, perhaps precluding identification of a secondary peak . Methods. In the Cardiac Arrhythmia Suppression Trial (CAST), 3,549 p atients had a documented myocardial infarction and entered antiarrhyth mic drug titration. Of these, 3,309 had data on the onset of symptoms relative to the time of awakening and form the basis of this report. R esults. A total of 870 patients (26.3%) were awakened by symptoms. Of the remaining 2,439 patients who were not awakened by symptoms, 798 (3 2.7%) experienced the onset of symptoms in the lst 4 h after awakening (with the highest number in the 1st h), after which the incidence of symptom onset decreased in a linear fashion, with a secondary peak 11 to 12 h after awakening. Both peaks are statistically significant. A s imilar pattern was seen in most of the subgroups examined (based on ag e, gender and various other demographic characteristics). Conclusions. Analysis of the very large CAST data base confirms the relation betwe en awakening and onset of symptoms of myocardial infarction, suggestin g involvement of the morning catecholamine surge. A secondary peak in symptom onset, occurring 11 to 12 h after awakening, is a new observat ion and may relate to ingestion of the evening meal or other trigger f actors concentrated in those hours.