Efficacy and tolerability of amlodipine in the general practice treatment of essential hypertension in an asian multinational population.

Objective: To evaluate the efficacy and tolerability of once-daily amlodipine (Pfizer Pharmaceuticals Inc.) alone or in combination with other antihypertensive drugs in an Asian population with essential hypertension.

Patients: An open study was undertaken in 165 male and 158 female patients with uncomplicated hypertension (diastolic blood pressure 95 to 115mm Hg).

Inter- and intraobserver variability in LVH and RVH reporting in pediatric ECGs.

Background: Physicians' diagnoses are often used as the gold standard for evaluating computer electrocardiogram (ECG) interpretation programs. As part of a larger study to evaluate the Glasgow pediatric ECG analysis program, inter- and intraobserver variability in the ECG reporting of two pediatric cardiologists was examined.

Methods: The ECGs of 984 children were sent for reporting independently by two cardiologists with all identifying information except age and sex removed.

Age, sex, and the ST amplitude in health and disease.

Electrocardiograms (ECGs) from 1,338 apparently healthy adults were analyzed to calculate limits of normality of a variety of ECG measurements. A second set of ECGs from 503 healthy Chinese individuals was also available for comparison of selected normal ranges. It was found that the normal limits of the ST amplitude in healthy individuals decrease with increasing age and, in general terms, are lower in women than in men, particularly in the precordial leads.

Reproducibility of a non-invasive real-time measure of cardiac parasympathetic activity.

The NeuroScope is a new device which produces a continuous real-time index of cardiac parasympathetic activity (the CIPA) and accurately measures RR intervals. The reproducibility of the CIPA has not yet been assessed. This study was designed to assess the reproducibility of a 5 minute recording of the CIPA using the NeuroScope and compare it with that of conventional heart rate variability (HRV) measures.

The contribution of ionic currents to changes in refractoriness of human atrial myocytes associated with chronic atrial fibrillation.

Objective: To investigate changes in human atrial single cell functional electrophysiological properties associated with chronic atrial fibrillation (AF), and the contribution to these of accompanying ion current changes.

Methods: The whole cell patch clamp technique was used to record action potentials, the effective refractory period (ERP) and ion currents, in the absence and presence of drugs, in enzymatically isolated myocytes from 11 patients with chronic (>6 months) AF and 39 patients in sinus rhythm.

Results: Stimulation at high rates (up to 600 beats/min) markedly shortened late repolarisation and the ERP in cells from patients in sinus rhythm, and depolarised the maximum diastolic potential (MDP).

Do KATP channels open as a prominent and early feature during ischaemia in the Langendorff-perfused rat heart?

The objective was to investigate whether myocardial adenosine triphosphate-sensitive K+ (KATP) channels open during the first 10 min of regional ischaemia in Langendorff-perfused rat hearts. Changes in monophasic action potentials and arrhythmias were studied during myocardial ischaemia in both the presence and absence of pharmacological KATP modulation. Ligation of the left main coronary artery for 10 min did not shorten the action potential duration (APD).

Techniques for improving overall consistency of serial ECG analysis.

The techniques that improve the overall repeatability of computer interpretation of electrocardiograms (ECGs) that have been recorded several minutes apart from patients in a clinically stable condition are described. Estimates of the normal amounts of variability present in many ECG parameters that are used in the identification of a variety of cardiac abnormalities have been adopted in conjunction with smoothing techniques to form the basis of the new methodology. When applied to the Glasgow ECG analysis program, these new methods improve overall repeatability by about 31% when tested on a set of 263 pairs of ECGs.

Age and body surface area related normal upper and lower limits of M mode echocardiographic measurements and left ventricular volume and mass from infancy to early adulthood.

Background: M Mode echocardiograms can be measured by two different conventions. In addition, normal limits of echocardiographic measurements have customarily been stratified according to age or body surface area. There is therefore a need to develop a more easily managed approach to calculating normal limits of measurements for the two conventions, one of which, the Penn convention, has not previously been used for echocardiographic measurements in children.

Smoothing techniques for improving the repeatability of the automated diagnosis of inferior myocardial infarction.

This study describes the implementation of novel techniques that have been designed with the aim of improving the repeatability of the diagnostic section of the Glasgow electrocardiographic (ECG) analysis program. Specific reference is made to the agreement in consecutive computer-assisted diagnoses of inferior myocardial infarction (IMI). Inherent repeat variation was estimated in ECG parameters of interest and used in conjunction with smoothing methods to produce a continuous Q-wave index ranging from 0 (no IMI) to 1 (IMI).

Detection of electrocardiographic 'left ventricular strain' using neural nets.

The use of artificial neural networks for classification of ST-T abnormalities of the electrocardiogram (ECG) was investigated. A training set of 356 lateral leads selected from 105 ECGs was visually classified as exhibiting one particular ST-T morphology (left ventricular (LV) strain) or not. Selected measurements, together with the classification, were fed as input to a three-layer software-based network during the learning process.

Classification of electrocardiographic ST-T segments--human expert vs artificial neural network.

Artificial neural networks, which can be used for pattern recognition, have recently become more readily available for application in different research fields. In the present study, the use of neural networks was assessed for a selected aspect of electrocardiographic (ECG) waveform classification. Two experienced electrocardiographers classified 1000 ECG complexes singly on the basis of the configuration of the ST-T segments into eight different classes.

Acceleration of ventricular response to atrial flutter after intravenous adenosine.

Adenosine may be of therapeutic and diagnostic value in the emergency management of arrhythmias. It causes transient atrioventricular nodal block and thus ends paroxysmal supraventricular tachycardias that involve the atrioventricular node. Also, it may uncover underlying atrial arrhythmias by slowing the ventricular response.

Improved repeatability of 12-lead ECG analysis using continuous scoring techniques.

This study describes a method for improving the day-to-day and minute-to-minute repeatability of the deterministic computer-assisted diagnosis of left ventricular hypertrophy. Conventional upper limits of normal for many age-dependent electrocardiographic parameters have been replaced by continuous equations, thereby, eliminating points of discontinuity that can contribute to lack of repeatability. Estimates of the normal amounts of variability present in many electrocardiographic parameters that are used in the diagnosis of left ventricular hypertrophy are calculated.

A new classification of left ventricular geometry in patients with cardiac disease based on M-mode echocardiography.

M-mode echocardiograms of 202 cardiac patients were studied with respect to the pattern of left ventricular (LV) geometry. Patients with normal LV mass and volume were separated from those who had LV hypertrophy or enlargement on the basis of LV mass and volume indexed to body surface area. The relative wall thickness that is currently used to classify LV hypertrophy/enlargement was found to be inadequate for differentiating between concentric and eccentric types of LV hypertrophy.

Thallium scans in syndrome X.

Objective: To review thallium scans in patients with angina and normal coronary arteriograms.

Design: Retrospective review of data.

Setting: Regional cardiac centre in Glasgow.

Symptomatic and silent myocardial ischaemia in hypertensive patients with left ventricular hypertrophy.

Objective: To assess the prevalence of symptomatic and silent myocardial ischaemia in patients with hypertensive left ventricular hypertrophy.

Design: Cross sectional study.

Setting: University department of medical cardiology.

Variable patterns of ST-T abnormalities in patients with left ventricular hypertrophy and normal coronary arteries.

Background: Classically, the ST-T configuration in the electrocardiogram of patients with left ventricular hypertrophy is said to have a typical pattern of ST depression together with asymmetrical T wave inversion (the so-called left ventricular strain pattern). However, many patients with left ventricular hypertrophy may also have ischaemic heart disease. To revise the electrocardiographic criteria for left ventricular hypertrophy the ST-T configuration in patients with left ventricular hypertrophy documented by echocardiography and with normal coronary arteries was assessed.

12-lead vectorcardiography in ischemic heart disease.

The conventional approach to recording the vectorcardiogram is to use a specially designed set of electrodes that derive 3-orthogonal leads, ideally corrected with respect to lead strength and direction. This has disadvantages in that it entails a separate recording as opposed to the use of the 12-lead ECG that is universally used. On the other hand, recently developed equations allow the vectorcardiogram to be derived from the 12-lead ECG, and although there is not a one-to-one correspondence with the vectorcardiogram derived using a corrected orthogonal lead system, it has been shown that there is a high degree of similarity between the two derivations.

A comparison of left ventricular mass and volume using different echocardiographic conventions.

Left ventricular dimensions were measured on M-mode echocardiograms, both by the Penn Convention and the Recommendations of the American Society of Echocardiographers in a sample cardiac population. The measurements of interventricular septum and the posterior wall of the left ventricle were significantly larger (P less than 0.001) using American Society Recommendations compared to using the Penn Convention.

Antagonism by adenosine and ATP of an isoprenaline-induced background current in guinea-pig ventricular myocytes.

A background current induced by isoprenaline, and its modulation by adenosine and ATP, have been studied using the whole cell patch clamp technique in guinea-pig ventricular myocytes. Isoprenaline (1-2000 nM) caused an inward shift of the holding current, in addition to increasing the inward calcium current (ICa). The effect on the background current was maximal earlier than the increase in ICa, but was of shorter duration.

Methodology of ECG interpretation in the Glasgow program.

This paper describes the methods currently used in Glasgow Royal Infirmary for computer analysis of electrocardiograms. The software is designed to analyse from 3 to 15 simultaneously recorded leads, with facilities for analysis of rhythm and serial changes. Options for Minnesota Code (with serial comparison) and XYZ lead interpretation are available.

A brief history of computer-assisted electrocardiography.

This paper reviews the history of the development of computer methods for ECG interpretation. Selected highlights are presented which indicate how technological advances have paralleled the growth of the application of the technique to a point where globally over 100 million ECGs per annum are now interpreted by computer.