Biomedical subjects

H P Calhoun

Publications and source records attributed to H P Calhoun.

7 recordsLinked to original sources

PubMed1994

Ethnic differences in ECG amplitudes in North American white, black, and Hispanic men and women. Effect of obesity and age.

General trends were investigated in the age-evolution of electrocardiogram (ECG) patterns using ECG data of North American white, black, and Hispanic men and women aged 25-74 years, derived from the Second National Health and Nutrition Examination Survey and the Hispanic Health and Nutrition Examination Survey. The data were stratified by race, sex, age, and obesity. There were substantial racial differences in ECG amplitudes. In general, ECG amplitudes and amplitude combinations used in left ventricular hypertrophy (LVH) criteria were larger in blacks than in whites. RV5 was smaller in all age groups of Hispanic women and in younger men, and RaVL was larger in Hispanics than in whites. There was, however, no significant difference in RaVL + SV3 amplitude between Hispanics and whites except in the youngest age group. The QRS frontal plane axis increased in men and women in all three racial groups by about 8 degrees per decade of age. Overweight was associated with 14 degrees more horizontal axis. RaVL and RaVL + SV3 amplitudes increased systematically with age and overweight, but there was an opposite tendency in RV5 amplitude. Multivariate logistic regression analyses indicated that age and the QRS axis had a relatively minor influence on LVH likelihood. Being black was associated with a more than fourfold excess of LVH by the Minnesota code criteria and a nearly threefold excess of LVH by the Cornell voltage criteria. Being overweight did not influence the odds ratio for LVH by the Cornell voltage criteria except in Hispanics, but the odds ratio for LVH was reduced by about 25% according to the Minnesota code criteria. The odds ratio of having LVH differed substantially for men and women by the Minnesota code and Cornell voltage criteria. Whereas there was a more than twofold excess likelihood of LVH in men by the Minnesota code criteria, there was a more than threefold excess of LVH likelihood in women by the Cornell voltage criteria when age, obesity, QRS axis, and race were simultaneously included as covariates in the logistic regression model.

Adult↗

PubMed1992

Should the JT rather than the QT interval be used to detect prolongation of ventricular repolarization? An assessment in normal conduction and in ventricular conduction defects.

It has been suggested that the JT rather than QT interval properly reflects repolarization duration in ventricular conduction defects (VCD). The authors examined the influence of QRS duration on the JT and QT intervals in 20,687 normal adult subjects and 2,865 subjects with various categories of VCD. Estimates for coefficients for multiple regression of QRS duration on QT and JT intervals combined with a correction term for heart rate (HR) were determined for each VCD category. QRS duration accounted for about 16% of total QT variation, but had a practically negligible effect on JT interval in complete bundle branch blocks. A single-parameter formula was derived for the JT prolongation index of the form JTI = JT(HR + 100)/518, with a JTI > or = 112 identifying repolarization prolongation in all VCD categories. It is concluded that it is preferable to predict JT rather than QT as a more appropriate index of duration of repolarization in VCD.

Adult↗

PubMed1992

NOVACODE serial ECG classification system for clinical trials and epidemiologic studies.

Traditional serial electrocardiogram (ECG) change classification schemes used in clinical trials such as the Minnesota Code rely on independent classification of the baseline and each follow-up or acute event ECG, whereby graded changes in the hierarchic severity level of the code signify new events such as myocardial infarction (MI). This approach suffers from classification errors caused by repeated instability at decision boundaries at each step when the baseline and each acute event ECG is classified, and various "verification rules" must be used at the end of the coding process to prevent trivial serial changes from causing large transitions in coded events. The NOVACODE algorithms for visual and computer coding of serial ECGs were designed to alleviate some of these instability problems by quantifying changes in critical waveform patterns on a continuous scale. This is achieved by determining, for each ECG coded, a Q-QS Score, ST Depression Score, ST Elevation Score and T-Wave Score, each ranging from 0 to 50. In the next step, a score is derived for ST-T evolution and this ST-T Evolution Score together with changes in Q-QS Score define criteria for a hierarchic mutually exclusive serial ECG change classification scheme that includes coding categories for Q-wave and non-Q wave MIs, equivocal Q wave evolution, evolving ischemic ST-T abnormalities, and various combinations of nonevolving Q-QS wave, and ST-T abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗

PubMed1992

Sex differences in the evolution of the electrocardiographic QT interval with age.

OBJECTIVE: To investigate sex differences in the evolution of the QT interval with age. SUBJECTS AND METHODS: A community-based representative North American population sample of 14,379 children and adults aged from birth to 75 years. The measured QT intervals (QTm) were determined by a computer algorithm and QTm, corrected for heart rate (HR), was expressed as QT index: QTI = (QTm/Tp) x 100, where QTp is the predicted QT from the formula QTp (ms) = 656/(1 + HR/100). MAIN RESULTS: The QTI values of females were significantly longer than of males in all age groups from 15 to 50 years tested at yearly intervals. This difference was due to a 20 ms drop in rate-corrected QT values in adolescent males after puberty, whereas QT values of females remained unchanged throughout the growth, maturation and reproductive years. The new QT prediction formula explained 83% of total QT variance in females and 82% in males after adjustment for heart rate and for the observed significant influence of ventricular excitation time (QRS duration) on QT interval in both sexes and a correction for QT age trend in males. CONCLUSIONS: The sex difference in the QT interval is due to QT shortening in males after puberty rather than QT prolongation in women during reproductive years. The fact that QRS duration is a significant determinant of the QT interval has important theoretical implications for attempts to model the ventricular repolarization process and it indicates that the traditional concept of reverse sequence of ventricular repolarization is not universally valid in all myocardial regions.

Adolescent↗

PubMed1990

Estimation of QT prolongation. A persistent, avoidable error in computer electrocardiography.

A pooled community-based population sample of 17,139 North American children, adolescents, and adults aged from birth to 75 years was used to evaluate a variety of one-, two-, and three-parameter formulas for correction of the QT interval for heart rate throughout a wide range of heart rates in sinus rhythm. QT measurements were made by a computer program from simultaneously sampled standard 12-lead or orthogonal XYZ leads, and all QT measurements were visually verified using a high-resolution display terminal. A random subsample of 1,920 was drawn 3 times by allocating 20 subjects to each heart rate subinterval of 1 beat/min, and the performance of a set of 13 QT prediction formulas was compared by ranking them according to the Akaike Information Criterion. The traditional Bazett's square root formula failed at low heart rates and the cube root formula of Fridericia at high rates. None of the linear two-parameter functions of R-R interval or heart rate performed with adequate accuracy. The best one-parameter formula for predicted QT(QTp) was obtained by regressing the inverse of QT on heart rate, with the expression QTp(ms) = 656/(1 + 0.01 H R), and by adding the term 0.4 x Age - 25 for age-related trend correction in males 15-50 years old. Percentile population distributions for the QT index (QTI = (QT/QTp) x 100) produced a convenient and stable 98 percentile normal QT range spanning 10% above and below the population median QTI = 100 in all major subgroups by age, sex, and race.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1990

Methodology of ECG interpretation in the Dalhousie program; NOVACODE ECG classification procedures for clinical trials and population health surveys.

The Dalhousie ECG Program was designed specifically for the needs of epidemiologic studies, health surveys, and clinical trials. The program logic is dynamic in that it can accommodate any combination of ECG leads, record length and sampling rate. The NOVACODE module of the program classifies ECGs according to the Minnesota Code, supplemented with new sets of logic criteria for conduction defects, acute myocardial infarction, and serial ECG changes. Improved statistical models are incorporated for enhanced detection of myocardial infarction using the Cardiac Infarction Injury Score, and for quantification of left ventricular mass estimation. It is anticipated that these program improvements will enhance its utility particularly in monitoring progression and regression of cardiac involvement in hypertensive and ischemic heart disease, and in the assessment of the effectiveness of intervention on cardiovascular disease risk factors.

Adolescent↗

PubMedDate not supplied

Contemporary medical management of left ventricular dysfunction and congestive heart failure.

OBJECTIVE: The primary purpose of this review was to address the following question: based on the best available evidence, what should be the current medical management of congestive heart failure (CHF)? DATA SOURCES: The major sources for this review were from searches of the English language literature, including computer and bibliography reviews, of all randomized, controlled clinical trials and overview analyses of positive inotropic agents, preload/afterload reduction agents and beta-blocker medications in CHF. STUDY SELECTION: The number of studies reviewed was approximately 40. The major criterion for selection was that the studies be of CHF patients in randomized controlled clinical trials, particularly with a mortality/survival endpoint. Additional clinical trials of nonmortality endpoints in CHF patients and mortality trials in non-CHF patients were also selected to support possible pathophysiological insights for future CHF trials. DATA EXTRACTION: The data, particularly for the accompanying tables, were initially extracted by a single reviewer using common qualitative guidelines as far as was possible within the different temporal, etiological and geographic frameworks of the original component studies. Conclusions are drawn from this data synthesis and from published overviews. DATA SYNTHESIS: Angiotensin converting enzyme (ACE) inhibition therapy is effective in reducing mortality and morbidity in severe left ventricular dysfunction and CHF. Other systemic vasodilators may also be beneficial. The effects of digitalis on survival and morbidity in CHF are presently uncertain, but should be resolved in the near future. Other inotropic agents, at least in the long term, are clinically detrimental. Diuretics decrease morbidity, but their effect on mortality in CHF remains unknown. Beta-blocker and magnesium therapy offer promise in CHF, but await definitive clinical trials evaluation. CONCLUSIONS: The current medical therapy of CHF should definitely include ACE inhibitors, probably diuretics and possibly other vasodilators. Further viable trials of promising new, and older heretofore under-evaluated, CHF therapies are needed. Additionally, innovative strategies are needed to deal with this disease which has an increasing prevalence. Two strategies, primary prevention of CHF and a 'Heart Function Clinic', are discussed.

Adrenergic beta-Antagonists↗