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PubMed2001

[Adaptation of Einthoven's string galvanometer for electrocardiography in the Netherlands].

After the Dutch physiologist Willem Einthoven (1860-1927) published the construction of his string galvanometer in 1901, the development of electrocardiography in the Netherlands was slow. During the next twenty years only a few string galvanometers were in use in the Netherlands, mostly in physiology laboratories. Publications concerning electrocardiographic tests on patients were scarce. In 1924, Einthoven was awarded the Nobel Prize for Physiology and Medicine for discovering the mechanism of the electrocardiogram. From that moment onwards, electrocardiography developed rapidly in the Netherlands and during the following 30 years particular use was made of the French string galvanometer designed by Boulitte.

Electrocardiography↗

PubMed2002

P wave signal averaged electrocardiography in patients undergoing the Fontan operation.

OBJECTIVES: Supraventricular arrhythmias are one of the most common and fatal sequelae of the Fontan operation. P wave triggered signal averaged electrocardiography was performed in patients undergoing the Fontan operation to evaluate the presence of atrial degeneration, and to clarify which factors affected the development of atrial arrhythmias. METHODS: P wave triggered signal averaged electrocardiography was recorded in 14 patients after the Fontan-type operation (conventional atriopulmonary connection in 5 and total cavopulmonary connection in 9) and 15 healthy controls. The duration and area of the filtered P wave, and the signal magnitudes (M20, M30) at 20 Hz and 30 Hz obtained from the frequency domain analysis of the P wave (M20, M30) were evaluated and compared with the hemodynamic data. RESULTS: The duration and area of the filtered P wave, M20 and M30 in patients after atriopulmonary connection were significantly greater than in those after total cavopulmonary connection and the control subjects (p < 0.05). M20 was significantly greater in patients after total cavopulmonary connection than in the control subjects. Right atrial volume in patients after atriopulmonary connection was significantly (p < 0.001) larger than in patients after total cavopulmonary connection (p < 0.05). There were no significant differences in other indices including atrial pressure between the two groups. CONCLUSIONS: Our results suggest that the substrate for atrial arrhythmias such as atrial myocardial degeneration and fibrosis is frequently present in patients after the Fontan operation, especially after atriopulmonary connection. Thus, the enlarged right atrium may be involved in the presence of a substrate for atrial arrhythmias. The developmental risk for late atrial arrhythmias seems to be present even in patients after total cavopulmonary connection.

Adolescent↗

PubMed2002

The role of limited echocardiography and electrocardiography in screening physicals for amateur athletes.

Sudden cardiac death in seemingly healthy young people during exertion has led to preparticipation assessment of athletes. Typically, cardiac evaluation is limited to auscultation by a primary care provider. Screening electrocardiography is controversial. The value of limited echocardiography is unknown. High school athletes undergoing preparticipation evaluation for organized athletics completed a medical history questionnaire and were examined with standardized history and physical, 12-lead electrocardiogram, and a limited two-dimensional echocardiogram. The studies were interpreted by cardiologists. Of 95 subjects recruited, there were 55 females and 40 males. There were 10 abnormalities detected requiring further evaluation, two by electrocardiogram and eight by echocardiography. Only one abnormality was found with screening physical examination. Abnormalities occurred with similar frequency (13% vs. 9%) in those with and without cardiovascular symptoms. Screening echocardiography and electrocardiography are of benefit in identification of cardiac anomalies not appreciated on routine physical examinations. Further study of these screening modalities is warranted.

Adolescent↗

PubMed2002

[Comparative analysis of parameters of corrected and uncorrected QT-interval dispersion of magneto-, electrocardiography and isomagnetic maps in patients with ischemic heart disease].

AIM: To compare possibilities of magnetocardiography (MCG) and electrocardiography for assessment of regional dispersion of ventricular recovery time using parameters of corrected and uncorrected QT-interval dispersion (DQTs and DQT). MATERIAL: Twenty three patients with class II angina pectoris including 11 patients with history of myocardial infarction (MI) and 13 practically healthy subjects. RESULTS: Mean DQT and DQTc were significantly higher (p<0.005) in patients than in healthy subjects according to both techniques. Values of DQT and DQTc obtained by MCG were higher in patients with history of MI compared with those without MI (p=0.006 and 0.02, respectively). There was a significant positive correlation between age and DQT and DQTc determined by electrocardiography. Mean number of T-wave dipoles was significantly higher in patients than in healthy subjects. Substantial positive correlation was found between number of T-wave dipoles on isomagnetic maps and age in both patients and healthy people. CONCLUSION: The method of MCG gave supplementary information on the state of ventricular depolarization in patients with ischemic heart disease.

Adult↗

PubMed2003

Non-invasive fetal electrocardiography in singleton and multiple pregnancies.

OBJECTIVES: To document the duration of fetal cardiac time intervals in uncomplicated singleton pregnancies using a novel non-invasive fetal electrocardiography (fECG) system and to demonstrate this technique's ability to acquire recordings in twin and triplet pregnancies. DESIGN: Prospective cross sectional observational study. SETTING: Antenatal wards and clinics, day assessment unit and centre for fetal care at a tertiary referral hospital, London, UK. POPULATION OR SAMPLE: Three hundred and four singleton and multiple pregnancies, 15-41 weeks of gestation. METHODS: Using electrodes sited on the maternal abdomen, a fetal electrocardiography (fECG) system was developed and tested on 304 pregnant women from 15 to 41 weeks of gestation, of whom 241 were uncomplicated singletons, 58 had twin and 5 had triplet pregnancies. The composite abdominal signals were stored on a laptop computer and the fECG derived off-line using a digital signal processing technique. For singletons, linear regression was used to analyse PR, QRS, QT and QTc intervals, and construct time-specific reference ranges. MAIN OUTCOME MEASURE: Duration of fECG time intervals as a function of gestational age. Success of signal separation in singleton, twin and triplet pregnancies. RESULTS: For singletons, a total of 250 recordings was obtained from 241 individuals with a signal separation success rate of 85% (213/250). Success rates were significantly poorer between 27 and 36 weeks of gestation (2 x k chi(2), P < 0.0001), with 84% (31/37) of separation failures occurring during this period. P, Q, R and S waves were seen in all cases where fetal signals were separated and were used to generate fECG time interval reference ranges. In 22% (43/199) of analysed cases, no T waves were identified, 63% (27/43) of whom were < or =24 weeks of gestation. In twins and triplets, separate fetal signals were obtained in 78% (91/116) and 93% (14/15), respectively; P, Q, R and S waves were evident in all averaged fECGs, while T waves were identified in 59% (54/91) and 57% (8/14). CONCLUSIONS: This study provides reference ranges with gestation for fECG intervals derived non-invasively from normal singleton pregnancies and demonstrates the feasibility of obtaining complete fECG recordings non-invasively across a wide gestational range in pregnancies of all pluralities. The fECG time intervals described will enable the identification of pathological fECG recordings from high risk pregnancies where fECG abnormalities are suspected.

Cardiotocography↗

PubMed1992

Noninvasive identification of patients at high risk for sudden cardiac death. Signal-averaged electrocardiography.

Signal-averaged electrocardiography allows the detection of late potentials, which have been associated with delayed and disorganized ventricular activation. This article reviews the technique, describes the findings recorded from patients with ventricular tachyarrhythmias, and assesses the prognostic value of late potentials for ventricular tachyarrhythmias and sudden cardiac death in patients after an acute myocardial infarction. The role of signal-averaged electrocardiography in the evaluation of patients with syncope and cardiomyopathies is also briefly discussed.

Cardiomyopathies↗

PubMed1991

Post-exercise time-course analysis of ST segment and T wave changes: an important contribution to the role of stress electrocardiography in aircrew.

Flight surgeons recognize that ongoing vigilance is necessary to detect coronary artery disease (CAD) in aircrew. Regular physical examinations with only a resting electrocardiogram, albeit having a very low predictive value for detection of CAD in asymptomatic subjects, are now widely practised. Routine stress electrocardiography has been criticized for yielding too many so-called "false positive" results because ST/T changes that develop during and after exercise are prevalent. Recent studies in our institution indicate, however, that the time-course behavior patterns of these ST/T configurational "abnormalities" after exercise are different from those reflecting myocardial ischemia due to epicardial CAD. Time-course analysis increases the predictive value of exercise testing and has dramatically decreased the number of asymptomatic aircrew being subjected to coronary arteriography in our institution. Routine exercise electrocardiography provides a reliable, cost-effective means of detecting aircrew with CAD and a baseline for comparison at subsequent examination, and we strongly recommend that it be universally reinstated.

Adult↗

PubMed1990

Common standards for quantitative electrocardiography: goals and main results. CSE Working Party.

Computer processing of electrocardiograms (ECGs) has over the last 15 years increased rapidly. Still, there are at present no standards for computer ECG interpretation. Different techniques are used not only for measurement and interpretation, but also for transmission and storage of data. In order to fill these gaps, a large international project, sponsored by the European Commission, was launched in 1980 to develop "Common Standards for Quantitative Electrocardiography (CSE)". The main objective of the first CSE study was to reduce the wide variation in wave measurements currently obtained by ECG computer programs. The second study was started in 1985 and aimed at the assessment and improvement of diagnostic classification of ECG interpretation programs. To this end reference libraries of well documented ECGs have been developed and comprehensive reviewing schemes devised for the visual and computer analysis of ECGs. This task was performed by a board of cardiologists in a Delphi review process, and by 9 VCG and 10 standard 12-lead programs developed by university research groups and by industry. A third action was started in June 1989 to harmonize acquisition, encoding, interchange and storing of digital ECG data. The action thus performed have become internationally recognized milestones for the standardization of quantitative electrocardiography.

Algorithms↗

PubMed1990

The role of computer modeling in electrocardiography.

This paper introduces some levels at which the computer has been incorporated in the research into the basis of electrocardiography. The emphasis lies on the modeling of the heart as an electrical current generator and of the properties of the body as a volume conductor, both playing a major role in the shaping of the electrocardiographic waveforms recorded at the body surface. It is claimed that the Forward-Problem of electrocardiography is no longer a problem. Several source models of cardiac electrical activity are considered, one of which can be directly interpreted in terms of the underlying electrophysiology (the depolarization sequence of the ventricles). The importance of using tailored rather than textbook geometry in inverse procedures is stressed.

Computer Simulation↗

PubMed1985

[Long-term electrocardiography: value and reliability of various systems].

25 years after the introduction of ambulatory electrocardiography four concepts are available: the conventional Holter-ECG, computer-based systems, entire ECG recording in miniaturized form and the event recorder. In contrast to visual analysis with the aid of an arrhythmia computer a more precise and quantitative evaluation of long-term ECG is possible. The reliability of a computer-based system is indicated by its sensitivity, positive predictive accuracy and reproducibility of automatic analysis. Only few of the computerized systems have been repeatedly tested on a company independent basis using these criteria in a representative number of patients, with frequent arrhythmias, and with a separate documentation of false negative, false positive and true positive events. Data available so far show that a reasonable reliability is possible, but 100% remains the exception to the rule. Thus, there is no complete automatic analysis of cardiac arrhythmias, and corrections by the physician are mandatory. This is further emphasized by the fact that only a part of all possible arrhythmias may be identified by computer whereas the other part has to be evaluated by visual control. In this context entire ECG recording is helpful, as an isolated method, however, it cannot be recommended, since the miniaturized ECG prevents analysis of subtle details and provides no quantitative data. Event recorders rely exclusively on the accuracy of the portable arrhythmia detector. Due to the concept of discontinuous ECG recording evaluation of this accuracy is pronounced problematic. Only by changing to the continuous recording mode does validation of the event recorder become possible. The first data demonstrate that the reliability of real-time analysis by the portable arrhythmia detector is not superior to highspeed analysis by the arrhythmia computer. Thus, quality control is necessary when using the event recorder as it is with continuous long-term ECG. However, there are significant limitations: with discontinuous ECG recording false negative events are not documented, separation of false positive from correct positive findings is restricted to the limited recording capacity (12-120 min real time) and the short ECG samples (6-12s) do not allow verification of sustained arrhythmias. Furthermore, questions regarding arrhythmias, ST-segment changes and pacemaker dysfunctions unidentifiable by computer remain unanswered with the use of the event recorder. For these reasons, continuous ambulatory electrocardiography providing complete data for every kind of analysis is still the standard method.(ABSTRACT TRUNCATED AT 400 WORDS)

Ambulatory Care↗

PubMed1988

Transesophageal pacing and electrocardiography in the neonate: diagnostic and therapeutic uses.

Transesophageal pacing and electrocardiography have important diagnostic and therapeutic uses in the neonate. Electrode placement is simple, and transesophageal ECG recording may be accomplished using available ECG recorders. Transesophageal pacing requires a special stimulator to administer stimulus pulses of 10 msec duration. Transesophageal ECG aids in establishing specific electrophysiologic Transesophageal ECG aids in establishing specific electrophysiologic diagnosis in neonates with rhythm disturbances. Transesophageal pacing is useful for treatment of atrial bradycardia as well as for cardioversion of a variety of tachycardias. There have been no serious long-term complications reported from use of transesophageal pacing and electrocardiography.

Cardiac Pacing, Artificial↗

PubMed1988

A hundred years of progress in electrocardiography. 2: The rise and decline of vectorcardiography.

Throughout the 20th century electrocardiography has been almost exclusively preoccupied by the single dipole concept as a model to account for body surface manifestations of cardiac electrical activity. Vectorcardiography, based on the single dipole approximation as an equivalent cardiac generator, has prevailed for over one half of this century as one of the most prominent components of electrocardiographic research. In retrospect, vectorcardiography has had conceptually an important impact on the progress in electrocardiography although it never became widely used in clinical practice. Recent comparative studies have confirmed that the diagnostic information contents of the standard 12-lead electrocardiogram and the vectorcardiogram are practically identical if adequately powerful, identical diagnostic classification procedures are used in extracting diagnostic information. After serving a useful role as a conceptual model, vectorcardiography is gradually fading away, being replaced by more realistic cardiac source models and by body surface leads supplementing in a better way the information content of the standard ECG leads.

Animals↗

PubMedDate not supplied

A hundred years of progress in electrocardiography. 1: Early contributions from Waller to Wilson.

The 1887 introduction of electrocardiography as a noninvasive investigative technique on man by Augustus Waller, and Wilhelm Einthoven's electrocardiograph from 1901 remain the two major landmarks in the 100-year history of electrocardiography. The progress in our knowledge of the mechanism and interpretation of the ECG has evolved throughout these 100 years in a succession of relatively small steps contributed by many unsung heroes, although often even relatively minor contributions by a few dominant "stars", notably Thomas Lewis and Frank Wilson, are perceived as giant leaps. The gradual evolution of our concepts of the ECG are reviewed against the historical background of the events involved from the time of Waller's discovery to the end of the second world war.

Electrocardiography↗

PubMed1987

[Quantitative evaluation of regional myocardial blood flow by digital subtraction angiography: correlations with exercise electrocardiography and Tl-201 myocardial scintigraphy].

We previously reported that the contrast disappearance half-life (T1/2) derived by the computerized washout analysis of digital subtraction coronary arteriograms provides a useful index for quantitatively evaluating regional myocardial blood flow. In the present study, we further evaluated the clinical usefulness of T1/2, comparing it with exercise electrocardiography and exercise thallium-201 myocardial scintigraphy. The study subjects consisted of 25 patients with angina pectoris and 14 patients with normal coronary arteries. Following the manual injection of contrast media into the left anterior descending coronary artery (LAD), a time-density curve was generated in the sectors of the myocardium which were perfused by the LAD and the T1/2 was calculated. T1/2 values correlated closely with double product (r = -0.73). They were significantly greater in patients with exercise-induced ST depression (8.3 +/- 1.0 vs 5.8 +/- 0.7, p less than 0.005). In addition, there was a good correlation between T1/2 values and washout ratio as determined by exercise thallium-201 myocardial scintigraphy, with r = -0.83. Although T1/2 values were within the normal range (mean +/- 2SD of control subjects) in all patients with LAD stenosis of 50 percent or less, these values were abnormally increased, exceeding the normal range, in 11 of the 12 patients with stenosis of 90 percent or more. Compared with exercise electrocardiography, T1/2 values were abnormally prolonged in 11 of the 13 patients with exercise-induced ST depression. Compared with exercise thallium-201 myocardial scintigraphy, T1/2 values were abnormally prolonged in seven of the nine patients with transient perfusion defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗

PubMed1987

[Two-dimensional exercise echocardiography. Comparison with electrocardiography, myocardial scintigraphy with thallium 201 and coronary angiography].

Biapical two-dimensional echocardiograms were obtained immediately before and after a bicycle exercise test in 54 patients referred for coronary angiography. Images of adequate quality were recorded in 47 cases (87%), 39 of whom had significant coronary artery disease. All patients also underwent a stress electrocardiogram. In 22 subjects echocardiography and bicycle stress test in the supine position were combined. 23 patients underwent scintigraphy with thallium-201. The sensitivity of rest and exercise echocardiography for the diagnosis of coronary artery disease was 90% and the specificity 63%, compared to 82% and 75% respectively for the electrocardiogram. The sensitivity for the detection of jeopardized myocardium, defined by angiographic criteria, was 75% for the exercise echocardiogram and 65% for the exercise electrocardiogram in the 28 patients without myocardial infarction. In 19 patients with infarction echocardiography detected jeopardized myocardium with a sensitivity of 73%, compared to 53% for the electrocardiogram. In the subgroup of 23 patients studied by thallium-201 scintigraphy, sensitivity for identification of multivessel disease (8 patients) was comparable for both rest and exercise scintigraphy (6/8) and echocardiography (7/8). The specificities were 88% and 94% respectively. Jeopardized myocardium was detected in this subgroup with a sensitivity of 82% by echocardiography, 76% by thallium scintigraphy and 65% by electrocardiography. In conclusion, this study demonstrates that two-dimensional echocardiography can be combined with exercise electrocardiography in one stress test. This improves the diagnosis of coronary artery disease, detection of jeopardized myocardium and identification of patients with multivessel disease.

Adult↗

PubMed1985

The prognostic significance of clinical history, exercise testing and ambulatory electrocardiography in patients with uncomplicated myocardial infarction.

The prognostic value of early clinical history, exercise testing and ambulatory electrocardiography was assessed in 263 men (mean age 50 years) recovering from an uncomplicated myocardial infarction (MI). During a mean follow-up period of 31 months, 11 patients died of cardiac causes, 22 developed a non fatal recurrent MI, 16 unstable angina (UA) and 16 underwent coronary artery bypass surgery. The appearance at the exercise stress test of an ischemic S-T segment depression of 0.2 mV or greater (P less than 0.001) as well as the achievement of a work load of 360 Kg-m/m' or less (P less than 0.01) and of a rate-pressure product of 200 Units or less (P less than 0.01), were found to be predictive of the future development of UA, but neither of cardiac death nor of non fatal recurrent MI. The ischemic response was also seen to be predictive of cardiac death (P less than 0.05). S-T segment depression of 0.1 mV or greater, angina and ventricular ectopic activity during the stress test and clinical history were not of predictive value. Complex ventricular ectopic activity (multiform extrasystoles, couplets and ventricular tachycardia) recorded during 24 hour ambulatory electrocardiogram was seen to be predictive of death and non fatal MI. Whereas some parameters such as the ejection fraction and the extension of coronary artery disease are generally accepted as good predictors for cardiac events, others, such as those derived from exercise testing, history and ambulatory electrocardiography may change their predictive value from one survey to another. These discrepancies are due to differences in patient characteristics, in methodology and in medical management.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina, Unstable↗

PubMed1984

Bipolar oesophageal electrocardiography and pacing in a coronary care unit.

This paper describes our experience with bipolar oesophageal electrocardiography in a coronary care unit. Twenty-two patients with tachycardia were studied to clarify the nature of their tachycardia. The treatment of supraventricular tachycardia by rapid atrial pacing via the same electrode was assessed in eight patients. The equipment required and diagnostic and therapeutic applications of oesophageal electrocardiography in this setting are discussed.

Acute Disease↗

PubMed1978

Detection of pericardial effusion by chest roentgenography and electrocardiography versus echocardiography.

To determine the sensitivity and specificity of chest roentgenography and electrocardiography in the detection of pericardial effusion, echocardiography was used as the diagnostic standard. Chest roentgenograms and electrocardiograms of 124 patients, 57 of whom had pericardial effusion, were read without knowledge of the echocardiographic interpretation. The sensitivity of roentgenographic diagnosis was low (20%), as was that of diagnosis from decreased voltage on the electrocardiogram (26%). The specificity of the chest roentgenogram was 89% and that of the low-voltage electrocardiogram 97%. The high specificity of the low-voltage electrocardiogram may have been due in part to the exclusion of obese and emphysematous subjects from the study. When cardiomegaly detected roentgenographically or a low-voltage electrocardiogram or both were considered as evidence of pericardial effusion, sensitivity improved to 82% but specificity declined to 29%. It is concluded the chest roentgenography and electrocardiography are unsatisfactory as screening investigations for the detection of pericardial effusion.

Echocardiography↗