[Mean high-amplification electrocardiogram during a submaximal exercise test following acute myocardial infarction]. / Enregistrement de l'électrocardiogramme à haute amplification moyenne lors d'une épreuve d'effort sous-maximale post-infarctus myocardique aigu.

The mean high-amplification ECG (MECG) used to detect delayed potentials (DPs) has so far been used only at rest and after exertion. In this article, the results are reported of recording the MECG at rest and during exercise (ER) obtained in 19 patients, the ER having been carried out at the subacute stage of myocardial infarction. Despite a significant increase in the background noise during exercise from 0.9 microV to 2.2 microV, it was possible to analyse the MECG recorded during exercise to detect DPs in all cases. In this small group of patients, no significant changes occurred with regard to the appearance or delayed potentials during exercise, although there was a reduction in the duration of HFQRS and an increase in the amplitude of RMS40 during exercise which was, however, much less marked in patients presenting DP.

Detection of late potentials on the averaged QRS signal recorded at rest and during a standardized stress test after acute myocardial infarction.

The high-amplification signal-averaged ECG (SAECG) allows the detection and analysis of late potentials (LP), which are related to a higher risk of severe ventricular arrhythmias in patients with myocardial disease and coronary artery disease. Because of excessive noise, this technique is usually performed at rest and occasionally immediately after interruption of exercise. Until now, however, it has not been used during exercise. The authors relate in this paper the method and results of the SAECG recorded at rest and during a standard stress test on 30 patients with a recent first myocardial infarction (day 10-14), in good condition, without ECG evidence of significant residual ischemia or bundle branch block. The SAECG was recorded during the steady state of a standardized stress test when a heart rate (HR) corresponding to 80% of the maximal HR was reached during a first test. Three patients had three criteria for LP, three others had two criteria, and two had only one. It has been impossible to analyze the SAECG during exercise because of excessive noise. One patient out of 30 in our study, 21 subjects had normal SAECG at rest and during exercise. None of the 6 patients with more than 1 abnormal criterion at rest became normal during the stress test despite a decrease of the duration criteria in all and an increase of the amplitude (root mean square) the terminal 40 ms (RMS40), as opposed to the 2 patients with just one positive criterion at rest (RMS 40 less than 25 muV) who became normal during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)