ST segment analysis by Holter monitoring: Methodological considerations

Background: There has been a renewed interest in ST segment analysis by Holter Monitoring, especially in multicenter clinical trials, but consensus on how to define an ischemic event is missing. We conducted a survey of European and U.S. publications involving ST segment analysis by Holter monitoring from 1975 to 2002 and found no notation of any correction for baseline ST segment depression in 52% of them. In 45% J-point depression was required in addition to ST segment depression measured either 60 ms (24%) or 80 ms (76%) after the J point. In 28% ST segment elevations were included. Method: Four different criteria for an ischemic event found in our survey were applied to Holter recordings from 66 patients with acute ischemic syndrome enrolled in the Esmolol Myocardial ischemia Trial (EMIT). Only lead CM5 was used and the analyzer was a Reynolds Medical Pathfinder 600. Results: By the most sensitive method (J + 80), there were 16 (24%) patients who had ischemic events in their Holter recording compared to only 10 (15%) patients if J-point depression was also required. If corrections were made for baseline ST segment depression, only 3 (4.5%) recordings were positive for ischemia. Conclusion: The outcome of Holter analysis for ischemic events is greatly dependent upon how an ischemic event is defined. Consensus on how to define an ischemic event is urgently needed.