Effect of pre-infarction angina on ventricular late potentials in patients with acute myocardial infarction and successful thrombolysis

Objective - Pre-infarction angina is considered as a good clinical model of ischaemic preconditioning which facilitates myocardial protection. Late potentials (LP) have prognostic significance following acute myocardial infarction (AMI). It is also well established that thrombolytic therapy reduces the incidence of LP. Our aim was to evaluate the relationship between pre-infarction angina and LP in patients receiving successful thrombolytic therapy. Methods and results - We prospectively studied 55 patients presenting with AMI (<6 hours). All patients received thrombolytic therapy and were evaluated with coronary angiography at predischarge. Signal-averaged recordings (SAECG) were obtained serially prior to thrombolysis, 48 hours after and 10 days later. Pre-infarction angina was present in 14 (25%) patients. There were no significant differences between the clinical characteristics and angiographic findings of the groups. Baseline SAECG parameters of the groups were also similar. After thrombolysis, the 48(th) hour values of LAS (the duration of the terminal low amplitude signals), and both the loth day values of LAS and RMS (root mean square voltage of the last 40 ms of the QRS) were. significantly better in the pre-infarction angina group. The mean filtered QRS duration and RMS 40 values changed significantly at the 10(th) day recordings of patients with pre-infarction angina [QRS duration, 110 +/- 34 ms before to 91 +/- 11 ms after (p = 0.039); RMS 40,40 +/- 17 muV before to 50 +/- 14 muV after (p = 0.02)]. The incidence of LP significantly decreased after thrombolytic therapy in the pre-infarction angina group, however, this change was not observed in patients without angina. Conclusion - Presence of pre-infarction angina reduces the incidence of LP following thrombolysis in AMI. This might be explained by the possible beneficial effect of ischaemic preconditioning on the arrhythmogenic substrate.