Search PubMed⌕ Search

Biomedical subjects

S H Zhou

Publications and source records attributed to S H Zhou.

31 records · Page 2Linked to original sources
PubMed1997

Using automated analysis of the resting twelve-lead ECG to identify patients at risk of developing transient myocardial ischaemia--an application of an adaptive logic network.

The aim of this study was to introduce an adaptive logic network computing method for detecting patients who were likely to show transient ischaemic episodes during ambulatory Holter monitoring, using parameters from a previously recorded standard twelve-lead resting electrocardiogram (ECG). In the present study, the adaptive logic network computing method is compared with other commonly used classification methods, such as backpropagation network and discriminant analysis techniques. Of 1367 study subjects aged 65 and above, 733 were women and 634 were men. Ambulatory Holter recordings were made to detect episodic ischaemia in study patients. Those subjects showing ischaemic episodes were classified as 'ischaemic' patients, and the remaining subjects were 'non-ischaemic'. Accuracy was 67% using the adaptive logic network computing method, 56% using the backpropagation network computing method, and 65% using statistical discriminant analysis. We concluded that the adaptive logic network technique offers a slightly higher accuracy and shows several potential advantages for automated detection of ischaemia in resting electrocardiograms.

Adult↗
PubMed1996

Improved ECG models for left ventricular mass adjusted for body size, with specific algorithms for normal conduction, bundle branch blocks, and old myocardial infarction.

Considerable efforts have been invested recently to improve electrocardiographic (ECG) classification accuracy for left ventricular hypertrophy (LVH). This study examines how LVH classification accuracy is influenced by (1) the selection of an echocardiographic standard for LVH, (2) LVH severity level in the test groups, and (3) the adjustment of LVH criteria for obesity and age. Using data obtained from large, community-based populations, this study explores prospects for improving ECG models for LVH classification and examines some of the general characteristics of newer ECG models for estimating left ventricular mass (LVM) on a continuous scale. The results indicate that the apparent ECG classification accuracy for LVH is substantially influenced by echocardiographic standards and criteria for LVH, LVH severity level, and selection criteria for test populations, and these differences explain some of the often substantial differences in test results from clinical versus community-based evaluation studies. The low reproducibility of echocardiographic LVM as the standard is a limiting factor in attempts to improve ECG criteria for LVH and LVM prediction models. Adjustment of ECG amplitudes to anthropometric factors that simultaneously influence LVM may result in confounding effects and may lead to the development of inappropriate models. The performance of ECG models for LVM prediction improved substantially by the inclusion of body weight as a covariate with ECG variables. The addition of standing height and various covariates reflecting obesity did not improve LVM prediction accuracy. Compared to the older LVM prediction models of the Novacode ECG program, the correlation between echocardiographic and ECG estimates of LVM increased sufficiently (from 0.33 to 0.54 in women and from 0.46 to 0.62 in men) to suggest that these improved ECG models are suitable for monitoring LVH progression/ regression in study groups participating in hypertension intervention trials.

Adult↗
PubMed1996

Methodology of serial ECG classification using an adaptation of the NOVACODE for Q wave myocardial infarction in the Bypass Angioplasty Revascularization Investigation (BARI).

Serial electrocardiographic (ECG) changes are a critical component of the diagnostic algorithm for classification of myocardial ischemic events in large-scale clinical trials. This study describes a computerized serial ECG classification program developed at the St. Louis University Core ECG Laboratory for use in the Bypass Angioplasty Revascularization Investigation (BARI) trial, in which patients with multivessel coronary artery disease were randomized to receive either coronary artery bypass grafting or percutaneous transluminal coronary angioplasty. The St. Louis University program detects and codes serial changes in Q, ST, and T wave items according to Minnesota code (MC) criteria using a modified NOVACODE hierarchical classification system. Measurements using a seven-power calibrated coding loupe are used to generate the MC from a customized software program. Significant minor or major changes are detected by the serial comparison program and referred to a physician coder for verification. Serial comparison coding rules are used to adjust for weaknesses in the standard MC classification system resulting from instability at decision boundaries. Of 4,244 BARI randomized and registry study participants with follow-up ECGs received at the Core ECG Laboratory as of March 1995, a grade 2 MC Q wave progression was noted in 568 participants (13.4%) using MC criteria alone, as compared with 367 (8.6%) after the St. Louis University coding rules were applied. The incidence of grade 1 MC Q wave progressions was 16.4% (697/4,244) versus 6.1% (259/4,244) when the St. Louis University program was applied. Intraobserver variability for grade 2 Q wave progression codes determined from a sample of 812 serial.

Algorithms↗
PubMed1996

Utility of new electrocardiographic models for left ventricular mass in older adults. The Cardiovascular Health Study Collaborative Research Group.

Several multivariate statistical models have recently been introduced for estimation of left ventricular mass from standard 12-lead electrocardiographic measurements. The validity of these algorithms has not been adequately evaluated. The objective of this investigation was to compare the associations between echocardiographic and electrocardiographic left ventricular mass values with clinical and subclinical indexes of coronary heart disease. The evaluation was performed with participants of the Cardiovascular Health Study, a population-based sample of 5201 men and women aged 65 years and older. Echocardiographic M-mode measurements of left ventricular mass were performed from videotape recordings with the use of a strictly standardized protocol. Electrocardiographic algorithms of the Novacode program and new algorithms derived from the Cardiovascular Health Study population were used for left ventricular mass prediction. Echocardiographic and electrocardiographic determinations of left ventricular mass were technically successful in 3410 (65.6%) and 5013 (96.4%) participants, respectively. The Novacode model overestimated echocardiographic left ventricular mass. Compared with the Novacode model, the new Cardiovascular Health Study electrocardiographic model, which includes adjustment for body weight, eliminated left ventricular mass prediction bias and improved the correlation between echocardiographic and electrocardiographic left ventricular mass from .33 to .54 in women and from .46 to .51 in men. Echocardiographic and electrocardiographic models both demonstrated similar and about equally strong associations with overt and subclinical disease and with risk factors for left ventricular hypertrophy. These observations demonstrate the potential utility of electrocardiographic models for left ventricular mass estimation.

Age Factors↗
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↗
PubMed1994

[Discovery of the first intermediate host of Paragonimus heterotremus].

Second generation rediae and cercariae of Paragonimus heterotremus were discovered from Tricula sp. collected from Paragonimus heterotremus endemic area, Napo County, Guangxi Zhuan Autonomous Region. The infection rate of the snails was 0.11% (4/3 530). The experimental infection of Tricula sp. collected from Wuming non-endemic area was done with P. heterotremus miracidia. The second generation rediae and cercariae of P. heterotemus developed later in the experimentally infected snails were similar to those in naturally infected snails. Thus far Tricula sp. from Napo County was confirmed to be the first intermediate host of P. heterotemus in nature (Figs. 1-6).

Animals↗
PubMed1993

Functional characteristics of QT prediction formulas. The concepts of QTmax and QT rate sensitivity.

A community-based population sample of 14,379 North American children and adults aged from birth to 75 years with normal ECG was used to investigate functional properties of 13 QT prediction formulas over a wide range of heart rates (HR) in normal 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. New concepts of QT rate sensitivity (dQT/dHR) and maximum predicted QT after a long pause (QTmax) are introduced. Drastically diverging functional behavior is documented for different QT prediction formulas regarding QT rate sensitivity and QTmax. The simplest formula for predicted QT (QTp) meeting reasonable physiological constraints regarding QTmax and functional behavior of QT rate sensitivity while producing the best QT prediction accuracy was a function with only one independently adjusted parameter (QTmax) of the form: QTp = QTmax/(1 + 0.01HR), with QTmax = 656 ms. This formula also suggests that QT rate sensitivity is inversely proportional to the square of HR and that individual values of QTmax can be predicted from ambulatory or exercise ECGs using the formula QTmax = 2 x QT100, where QT100 is QT at HR = 100/min.

Adolescent↗
PubMed1993

Improved ECG models for estimation of left ventricular hypertrophy progression and regression incidence by redefinition of the criteria for a significant change in left ventricular hypertrophy status. The MRFIT Research Group. Multiple Risk Factor Intervention Trial.

Three sets of left ventricular hypertrophy (LVH) criteria were evaluated in terms of their utility for LVH progression and regression incidence estimation. Incidence comparisons were performed with and without taking short-term variability into consideration using electrocardiographic records taken at the baseline and the first annual follow-up examination of 11,969 men, aged 37 to 55 years, at the baseline of the Multiple Risk Factor Intervention Trial. Short-term total technical and biologic variability (95% range) was determined from the records of 104 men invited for a repeat electrocardiographic recording at 2-week or shorter intervals from the first recording. The results indicated that after elimination of the false fraction due to normal variability, the residual incidence estimates are so low that their utility and statistical power in monitoring changes in LVH status is very limited. It is concluded that a redefinition of LVH progression and regression criteria is needed to enhance their utility in clinical trials.

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

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↗