Clinical implications of early ST-segment variability. A report from the ASSENT 2 ST-monitoring sub-study

OBJECTIVES: Evolution of the ST-segment during acute myocardial infarction has been shown to yield more information on prognosis than invasive measurements. By continuous ST-monitoring even very occasional dynamic changes can be analysed. We have recently suggested these variations to be of prognostic importance and possibly reflect individual abilities to deal with a vascular event. We wanted to confirm these findings. METHODS: Four hundred and forty-eight patients were included in the vectorcardiographic sub-study of the second Assessment of Safety and Efficacy of a New Thrombolytic (ASSENT 2) trial. Patients underwent 24 h of ST-monitoring. ST-trend curves were blindly analysed by two independent observers. RESULTS: ST-variability, defined as an increase of the ST-segment shift of > or = 25 microV for 2 min or more, was found to predict death, reinfarction at 30 days or urgent revascularization. By combining variability with resolution of the ST-segment elevation we could identify a high-risk group with 9.9%, and a low-risk group with only 0.8% 30-day mortality. Hypertensive patients, suggested to have an impaired secretion of endogenous t-PA, expressed significantly more ST-variability, possibly a non-invasive marker of impaired capability of dissolving and preventing thrombi. CONCLUSION: Small variations in ST-segment shift during the first 4 h of acute myocardial infarction predict worse outcome.