High-Bandpass Filters in Electrocardiography: Source of Error in the Interpretation of the ST Segment.

Introduction. Artifactual variations in the ST segment may lead to confusion with acute coronary syndromes. Objective. To evaluate how the technical characteristics of the recording mode may distort the ST segment. Material and Method. We made a series of electrocardiograms using different filter configurations in 45 asymptomatic patients. A spectral analysis of the electrocardiograms was made by discrete Fourier transforms, and an accurate recomposition of the ECG signal was obtained from the addition of successive harmonics. Digital high-pass filters of 0.05 and 0.5 Hz were used, and the resulting shapes were compared with the originals. Results. In 42 patients (93%) clinically significant alterations in ST segment level were detected. These changes were only seen in "real time mode" with high-pass filter of 0.5 Hz. Conclusions. Interpretation of the ST segment in "real time mode" should only be carried out using high-pass filters of 0.05 Hz.

[Treatment of chronic stable angina: follow-up study with nifedipine gastrointestinal therapeutic system. SENIOR Study Group]. / Tratamiento de la angina de pecho crónica estable: estudio de seguimiento con nifedipino OROS (estudio SENIOR). Grupo de Trabajo del estudio SENIOR.

OBJECTIVE: To gather information about efficacy and tolerability of nifedipine GITS in patients with stable angina, and its impact on the patient quality of life. PATIENTS AND METHODS: 1076 patients of both sexes (63.5 +/- 12.8 year old) with stable angina (classes I to III of the CCVS) and evidence of coronary disease (43.3% previous myocardial infarction) were included. The treatment with nifedipine GITS 30-60 mg/day (monotherapy or combination) lasted for 6 months. The study variables were: weekly rate of anginal attacks, short-acting nitrate consumption, changes in the antianginal drug treatment, tolerability, and changes in the questionnaire score concerning the quality of life. RESULTS: A decrease in the number of the anginal attacks and in the short-acting nitrates consumption by 80.7% and 83.3%, respectively (both, p = 0.001), was found. Furthermore, the proportion of patients experiencing anginal attacks the week before the assessment visit fell from 71.7% to 10.9% (p < 0.001). At the end of the study, a remarkable decrease in the use of other antianginal medications was seen. Side effects were reported by 10.9% of the patients, 2.7% of which were withdrawn from the study for this reason. A favourable change in the patient quality of life was also noted. CONCLUSION: In patients with stable angina, nifedipine GITS is an effective, safe and well tolerated drug that remarkably enhances the patient quality of life.