John M. Chapman

Effects of various factors on systolic and diastolic blood pressure in the Los Angeles heart study

Abstract Higher systolic blood pressures were found among similar age groups measured in 1962 compared to those found in 1950 in the Los Angeles Heart Study. Analyses were performed to insure that these differences were real and not due to measurement differences or to self selection. Covariance analyses indicated that higher blood pressures occurred among subjects who reported that they had not eaten for 2 hr or more or for 5 hr or more prior to examination as well as among non-smokers, alcohol users, and non-salt adders. The magnitude of the differences associated with these factors is probably not of clinical significance. None of these factors explain the existing differences in blood pressures between these two examination periods. Thus, the differences observed are consistent with the hypothesis of a healthier population, age for age, entering the study in 1950 compared to the survivors examined in 1962.

The differential effect of serum cholesterol, blood pressure and weight on the incidence of myocardial infarction and angina pectoris

Abstract The results of 15 yr of follow-up of white males at risk in the Los Angeles Heart Study are reported. The total number of new cases of coronary heart disease is divided into 2 groups: (i) persons who were diagnosed myocardial infarction, or sudden death (MI), and (ii) persons who were diagnosed as angina pectoris (AP). The risk factors studied were age, serum cholesterol level, blood pressure and wt. index. Two techniques of analysis, the classical method and discriminant function analysis, are used and compared. In both methods of data analysis high serum cholesterol is clearly associated with the development of MI. None of the 3 factors studied had an appreciable influence on AP.

The relation between hemoglobin level and the risk for ischemic heart disease: A prospective study

Abstract An attempt has been made to test hemoglobin level for the possibility of being a risk factor in the genesis of ischemic heart disease (IHD). This was necessary since some case-control studies and a few observations made on the distribution of the disease, as well as the analysis of cross-sectional data from the Los Angeles Heart Study (LAHS), suggested that such risk may exist. This report shows the analysis of the 16-yr follow-up data from the LAHS, which includes comparison of the incidence of IHD according to the initial level of hemoglobin in a sample of 1859 men, and carrying out the stepwise discriminant analysis between subjects who developed the disease and those who remained free. Eleven variables measured at entry were included in the discriminant analysis: age, race, cholesterol, systolic blood pressure, diastolic blood pressure, hemoglobin, hematocrit, RBC count, socioeconomic level, Sheldon weight index, and job activity. The results show that none of the three related variables—hemoglobin, hematocrit, and RBC count—contributes significantly to the development of IHD. Only age, race and cholesterol level can discriminate independently between subjects who developed the disease and subjects who remained free. In addition, three other variables—systolic BP, Sheldon weight index, and job exercise—can discriminate between the two groups only when considered individually without accounting for the effect of other variables. The earlier findings in case-control studies and in our cross-sectional data may, therefore, be interpreted as that hemoglobin possibly rises after the occurrence of IHD, or secondary to changes in the levels of the other risk factors. Thus it may be a consequence of, rather than a risk for, the disease, and its associations with some of the risk factors revealed previously are of no causal significance in the genesis of this disease.

Electrocardiographic data recorded with Frank leads in subjects without cardiac disease and those with left ventricular overload.

Abstract Amplitudes and durations of scalar deflections were measured in Frank lead electrocardiograms from 505 men without clinical evidence of cardiac disease. Amplitudes of the major QRS deflections and of T waves were significantly correlated with age; they were also correlated to a lesser degree with chest diameter and relative body weight. The results indicate that normal limits for some Frank lead electrocardiographic variables should be stratified by age. Discrimination between normal subjects and cases with left ventricular overload was not so good with selected Frank lead variables as with standard lead electrocardiographic criteria.

Computer analysis of Frank lead electrocardiographic data recorded in an epidemiologic study

Abstract This report describes results of computer analysis of Frank lead electrocardiographic data recorded during a population study. Computer and visual measurements were compared in records from the same subjects. The prevalence of several Frank lead findings and standard lead electrocardiographic criteria were compared in subjects without clinical evidence of cardiac disease, in subjects with a clinical history of myocardial infarction or other evidence of cardiovascular abnormality, and in an unclassified group. A multivariate statistical method was used to evaluate the capability of several sets of Frank lead variables to identify records from subjects with standard lead electrocardiographic abnormalities and to discriminate between normal subjects and those with cardiovascular abnormalities. Most, but not all, records from subjects with standard lead electrocardiographic abnormalities were identified with the use of Frank lead variables. A multivariate statistic using four points during the ST-T wave may be more effective than some standard lead ST-T findings in discriminating between normal subjects and those with cardiovascular abnormalities. Other Frank lead variables did not give better discrimination between these two groups than standard lead criteria. More subjects in the unclassified group had Frank lead findings outside normal limits than had abnormalities in the standard leads; further study will be necessary to determine whether this indicates that these Frank lead variables have higher sensitivity or lower specificity for cardiac disease.

Validity of 70 mm. photofluorograms of the chest in screening a population for heart disease

Abstract Minifilms of the chest taken routinely during the course of cardiovascular examinations of the Los Angeles Heart Study population were reread independently by two observers to assess the validity of the 70 mm. photofluorogram as a screening device for diseases of the heart. Roentgenographic cardiovascular abnormalities were recorded by the observers in 32.5 and 16.6 per cent of the study population. At the higher of the two levels of reading, 71.2 per cent of the persons with heart disease and 28.8 per cent of those who had normal hearts had “positive” films according to the criteria used. At the lower level of reading approximately half (49.4 per cent) of the clinically diagnosed cases of heart disease in the study population were “identified” by the minifilm, while 13.8 per cent in the clinically normal group had positive roentgenograms. A relatively small increase occurred in the proportion who were minifilm positive among diagnosed cases in the older (55 to 70 years) age group as compared to those in the 30 to 54 year group, this was in contrast to the sharp increase with age in the proportion with positive minifilms in the clinically “normal” group. The validity of the roentgenographic screening was based primarily on the finding of heart enlargement and, of the etiological types, hypertensive heart disease was identified with the greatest relative frequency. Abnormalities of the aorta (without heart enlargement), when used as a criterion for “positive” film, had little or no validity in screening, for approximately the same proportion were positive in the clinically diseased as in the nondiseased segments of the study population. The relationship of the findings to group screening is discussed.

Hemoglobin level and ischemic heart disease: relationship to known risk factors.

Abstract The data collected on 1,859 male participants of the Los Angeles Heart Study were analyzed to examine the relationship between hemoglobin level and several ischemic heart disease risk factors. Significant associations between hemoglobin and systolic blood pressure, diastolic blood pressure, cholesterol, body weight, and smoking in white males of this sample were revealed; hemoglobin increased with the increase of each of these variables. In addition, a trend of increasing hemoglobin with less physical activity was observed. No relationship was found between hemoglobin, stress, and electrocardiographic abnormalities. These findings imply that further investigations through prospective studies of the possible association of hemoglobin and the incidence of ischemic heart disease, either independently or jointly with other factors, are indicated.