Quality control procedures for the resting electrocardiogram in the Multiple Risk Factor Intervention Trial.
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Clinical Trials as Topic↗
Biomedical subjects
W J Eifler
Publications and source records attributed to W J Eifler.
Prognostic value of exercise electrocardiogram in men at high risk of future coronary heart disease: Multiple Risk Factor Intervention Trial experience.
The prognostic value of the exercise electrocardiogram was examined in the 6,438 usual care men of the Multiple Risk Factor Intervention Trial in relation to fatal and nonfatal coronary heart disease events, rest electrocardiographic abnormalities and coronary heart disease risk factors. An abnormal response to exercise, defined as an ST depression integral of 16 microV-s or more, was observed in 12.2% of the men. There was a nearly fourfold increase in 7 year coronary mortality among men with an abnormal response to exercise compared with men with a normal ST segment in exercise (risk ratio 3.8, 95% confidence limits 2.5 to 5.5). The risk ratio for coronary death, adjusted for age, diastolic blood pressure, serum cholesterol and smoking status at baseline was 3.5, and the corresponding adjusted risk ratio for death from all causes was 1.6. A similar trend toward excess coronary events was seen for angina pectoris (risk ratio of 1.6). The trend was not significant for nonfatal myocardial infarction. Multivariate analyses indicated that the ST depression integral was a strong independent predictor of future coronary death (p less than 0.001). Men with an abnormal electrocardiogram at rest (mainly high amplitude R waves) and with an abnormal ST response to exercise had an over sixfold relative risk for coronary death compared with men with an abnormal electrocardiogram at rest and a normal ST response to exercise. These results suggest that exercise testing may be indicated for improved risk assessment and the assessment of the significance of minor rest electrocardiographic abnormalities in middle-aged men with elevated levels of coronary heart disease risk factors.
Adult↗
Mechanism of generation of body surface electrocardiographic P-waves in normal, middle, and lower sinus rhythms.
We used comprehensive electrophysiological/anatomical digital computer models of atrial excitation and the human torso to study the mechanisms of generation of body surface P-waves in normal sinus rhythm, and in middle and lower sinus rhythm. Simulated atrial surface isochrone maps for normal sinus rhythm support the validity of the atrial excitation model. The results suggest that the presence of specialized internodal tracts containing fast-conducting fibers is not essential to account for propagation of excitation in apparent preferential directions from the sinoatrial (SA) node to the atrioventricular node. However, in the absence of fast conducting fibers, a slowly conducting segment in the intercaval region is necessary to achieve proper excitation of the interatrial septum. P-wave notches occur in the absence of specialized fast conducting atrial tracts and anisotropies due to fiber orientation. These notches are due to the atrial geometry and the separate contributions of the right atrium, left atrium, and interatrial septum to the P-waves, and become more pronounced as the pacemaker site shifts downward in the SA node. Thus, slight changes in the origin of excitation, which result in subtle changes in the atrial excitation isochrones, produce significant and complex changes in the simulated body surface P-waves.
Adult↗
A simple procedure for positioning precordial ECG and VCG electrodes using an electrode locator.
Methodological differences in the placement of precordial ECG electrodes are a major problem in multicenter clinical trials and epidemiological studies. Trend analysis and realization of the full potential of computer programs for serial comparison demands reduction of technical sources of variation in the electrocardiogram (ECG) and vectorcardiogram (VCG) and particularly errors in locating ECG electrodes. The ECG electrodes locator described here reduces a major precordial uncertainty in the identification of the midclavicular and the anterior axillary lines. It simplifies positioning and provides a numeric record of the key precordial electrode positions, facilitating control of electrode placement errors in serial recordings.
Adult↗
A cellular model for the simulation of activation in the ventricular myocardium.
A digital computer model of cardiac activation was used to investigate the relationship between cellular orientation and conduction and propagation of the ventricular activation wave front. The results of the simulation for a single cycle initiated in fully recovered tissue under normal and simplified pathological conditions (ischemia and infaraction) indicate (a) that the conduction velocity of the cellular action potential in ventricular cardiac tissue may be several (3-5) times greater than is normally considered to be the case, (b) that the ventricular activation wave front propagates transmurally from endocardium to epicardium despite fiber orientation parallel to these surfaces, without the need for assuming the existence of either lateral contacts between adjacent cells or fibers with a transmural orientation, (c) the wave front of activation propagates through ventricular cardiac tissue with an anisotropic phase velocity, (d) the presence of ischemia and infarction gives rise to tangential spread of activation, and (e) small subendocardial infarcts should not be considered to be electrically silent.
Action Potentials↗