Continuous ST segment recording during thrombolysis in acute myocardial infarction: a report on orthogonal ECG monitoring.

Background: A noninvasive, real time method is needed to identify failures of thrombolysis and evaluate new treatments in acute myocardial infarction (MI).

Objective: To study XYZ monitored ST segment evolution during thrombolysis in acute MI and to examine the correlation of ST parameters to outcome.

Design: Thirty-five patients receiving tissue plasminogen activator (tPA) (n = 18) or streptokinase (SK) (n = 17) for acute MI were monitored by vector-cardiography during the first 12 h of thrombolytic therapy. Computer constructed ST vector magnitude (ST-VM) trends were analyzed for 0.5 or greater decline from the initial ST amplitude (IA) lasting for 10 mins or longer (ST response) and for ST re-elevation 0.75 IA or more following ST decline. The degree of ST response, time from treatment onset and ST-VM re-elevation were correlated to peak creatine phosphokinase (CPK), left ventricular ejection fraction (EF) and final ST-VM.

Results: The presence of an ST response correlated with a lower peak CPK (2691 +/- 1625 versus 4057 +/- 1622 U/L, P = 0.043) and tended to higher EF (0.48 +/- 0.11 versus 0.36 +/- 0.09, P = 0.057). The ST responder group had fewer patients with ST re-elevation than the group of nonresponders (13 of 30 versus five of five patients, P = 0.041). Moreover, ST response before 120 mins was associated with lower peak CPK (2089 +/- 1299 versus 3367 +/- 177 U/L, P = 0.02) and better EF (0.54 +/- 0.06 versus 0.41 +/- 0.12, P = 0.02) compared with later or no ST response. The degree of ST response correlated significantly with a lower ST-VM during the last hour (r = -0.744, P = 0.001). ST trends showed no significant differences between treatment groups (tPA versus SK). The tPA group, however, tended to an overall earlier ST response (117 +/- 75 versus 163 +/- 64 mins, P = 0.13).

Conclusions: Early ST-VM trends are closely associated with electrocardiographic and clinical outcome and may provide a basis for clinical management, therapeutic comparisons and better insight into thrombolysis in MI.