[Diagnostic value of amplitude variations of the QRS complex during computerized exercise testing].

Two hundred and fifteen patients were examined: 20 athletes, 40 subjects with radiologically normal coronary arteries (NCA) and 155 patients with one or more coronary artery stenoses (82 without, 73 with previous myocardial infarction). Exercise testing was by bicycle ergometry. The ECG recordings obtained by a computerised system had stable base lines and variations in QRS amplitude related to respiration were eliminated. The changes in amplitude of the R wave (delta R) and QRS complex (delta QRS) during exercise are interesting, especially in lead CM5. The amplitude decreases or remains the same in athletes (delta R = -1.3 +/- 3.2 mm; delta QRS = 0.7 +/- 3.4 mm) and in patients with NCA (delta R = -0.2 +/- 2.5 mm; delta QRS = 0.5 +/- 3.1 mm). This contrasted with the coronary group in whom these amplitudes increased significantly (delta R = 1.5 +/- 2.9 mm; delta QRS = 3.1 +/- 3.2 mm, p less than 0,001). These variations did not give indications of ischaemia of another region or of the presence of an aneurysm in patients with previous infarction. The greatest variations in amplitude were observed in patients with signs of previous inferior infarction. Can this method provide diagnostic information in patients without previous myocardial infarction? If positive delta R and delta QRS are defined as increases of at least 1 mm on exercise, the diagnostic value of these changes (sensitivity: delta R = 58.5%, delta QRS = 78%; specificity: delta R = 67.5%, delta QRS = 57.5%) is comparable with the classical signs of: pain (sensitivity: 63%; specificity: 75%) and ST depression of over 1 mm in CM5 (sensitivity: 72%; specificity: 62.5%). In conclusion, in patients without previous myocardial infarction, the reliability of exercise stress testing in diagnosing coronary artery disease can be increased when the following three parameters are taken into consideration: pain, ST segment, delta R or delta QRS or both. When all three signs are negative, the stress test can be considered negative (the 82 coronary patients had at least one positive sign). The positivity of one sign alone corresponds to a normal coronary circulation in the majority of cases. The presence of 2 or 3 positive signs is very much in favour of coronary artery disease.