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At least 19 recordsLinked to original sources

PubMed1990

Noninvasive diagnosis of ventricular arrhythmias by means of ambulatory-ECG monitoring.

Ambulatory ECG monitoring has enabled documentation of the type and frequency of ventricular arrhythmias and their relation to symptoms as well as prognosis. On 24-hour ambulatory ECG monitoring, ventricular premature beats (VPB) can be found in healthy subjects with a prevalence of 40 to 80% which is directly related to age. Complex ventricular arrhythmias are uncommon. The prevalence of VPB is higher in patients who have underlying structural heart disease; in those resuscitated from out of hospital sudden cardiac death, it is reported to be 100%. One of the most important concerns with regard to ventricular arrhythmias is the problem of spontaneous variability. There is, however, a higher degree of reproducibility on two consecutive days in patients with more than 300 VPB/hour and in patients who have experienced sustained ventricular tachycardia than in those with infrequent VPB. When ambulatory monitoring is repeated months up to one year after the initial investigation, reproducibility of arrhythmias is poor. The mechanism of sudden cardiac death has been shown to be ventricular tachycardia or ventricular fibrillation, both of which are associated with an antecedent increase in VPB. In patients with chronic coronary artery disease, idiopathic or hypertrophic cardiomyopathy, a relationship between the presence of ventricular arrhythmias and sudden cardiac death has been described but VPB are considered to be of independent prognostic value only in those with myocardial infarction. Ambulatory ECG monitoring is the preferred noninvasive method for drug evaluation in patients with frequent ventricular arrhythmias. In general, the available antiarrhythmic drugs are effective for suppression of ventricular arrhythmias in 45 to 80% of patients. As a side-effect dependent on the underlying condition, the incidence of proarrhythmic effects varies from 6 to 19%. Medical treatment may be effective in prolonging life in resuscitated patients. Limitations of ambulatory monitoring include low reliability in the presence of infrequent ventricular arrhythmias or marked spontaneous variability, low specificity with respect to prognosis, lack of standardized definition for treatment efficacy and problems of recognizing complex forms of ventricular arrhythmias.

Anti-Arrhythmia Agents↗

PubMed1999

Using simulated noise to define optimal QT intervals for computer analysis of ambulatory ECG.

The ambulatory electrocardiogram (ECG) is an important medical tool, not only for diagnosis of adverse cardiac events, but also to predict the risk of such events occurring. The 24-hour ambulatory ECG has certain problems and drawbacks because the signal is corrupted by noise from various sources and also several other conditions which may alter the ECG morphology. We have developed a Windows based program for the computer analysis of ambulatory ECG which attempts to address these problems. The software includes options for importing ECG data, different methods of waveform analysis, data-viewing, and exporting the extracted time series. In addition, the modular structure allows for flexible maintenance and expansion of the software. The ECG was recorded using a Holter device and oversampled to enhance the fidelity of the low sampling rate of the ambulatory ECG. The influence of different sampling rates on the interval variability were studied. The noise sensitivity of the implemented algorithm was tested with several types of simulated noise and the precision of the interval measurement was reported with SD values. Our simulations showed that, in most of the cases, defining the end of QT interval at the maximum of the T wave gave the most precise measurement. The definition of the onset of the ventricular repolarization duration is most precisely made on the maximum or descending maximal slope of the R wave. We also analyzed some examples of time series from patients using power spectrum estimates in order to validate the low level QT interval variability.

Algorithms↗

PubMed1989

[Comparative study of the ECG exercise test and ambulatory ECG monitoring after recovery from acute myocardial infarction].

Early ECG exercise tests (EET) and ambulatory ECG monitoring (AEM) were performed in 42 patients surviving AMI in order to determine the sensitivity of the two methods for detecting ST-segment deviation and arrhythmias. 23 patients had ST changes during EET and AEM. Of them, 21 patients had ST changes induced by EET and 10 were recorded by AEM. The more the ECG leads used for monitoring during and after EET, the higher the percentage of patients with ST changes will be. There were 2 cases with ST changes found in AEM only. All the 6 patients who had ST elevations during EET had an anterior infarction and echocardiograms did show that they had left ventricular aneurysms or abnormal ventricular wall movement. AEM recorded ventricular premature beats (VPBs) in 37 cases (88.0%), while EET induced VPBs in 8 patients. The 42 patients were followed up for an average time of 6 +/- 1.7 m. (3.4 to 9.3 m.) Cardiac death occurred in 2 cases. One of them had horizontal ST depression of 3 mm during EET, the other had a negative EET but multifocal VPBs during AEM. It is concluded that for detecting ST changes EET is more sensitive than AEM, while VPBs are more frequently found in AEM than in EET. The authors are of the opinion that for better, prediction of the prognosis of patients after AMI, it is preferable to have early EET in combination with AEM.

Aged↗

PubMed1987

Asymptomatic telephone ECG transmissions as an outpatient surveillance system of ventricular arrhythmias: relationship to quantitative ambulatory ECG recordings.

Although ambulatory ECG recordings provide quantitative information in the follow-up of patients with ventricular arrhythmias, they are performed infrequently, potentially missing serious arrhythmias in the unmonitored periods. Telephone ECG systems offer "real-time" ECG information, theoretically functioning as an arrhythmia surveillance system. Thus we incorporated frequent telephone ECG transmissions in two antiarrhythmic drug protocols. The first investigation was designed to show the relationship of telephone and ambulatory ECGs in patients with frequent ventricular tachycardia (VT). The second protocol selected patients with "nonlife-threatening" frequent premature ventricular complexes (PVCs) in whom a second placebo period was instituted to simulate the clinical situation of asymptomatic arrhythmia increase. In both drug trials there was a strong linear relationship between the log-transformed PVC counts of telephone ECG and concomitant PVC, couplet, and VT frequencies on ambulatory ECG. In the VT population, greater than or equal to 1 PVC on telephone ECG reflected the presence of VT on ambulatory ECG (sensitivity 87%; specificity 77%). In the second study, telephone ECG transmissions with PVCs on three consecutive transmissions reflected the change from less than or equal to 10 PVCs/hour to greater than or equal to 40 PVCs/hour on ambulatory ECG within 48 hours. These data support the concept that daily surveillance by means of telephone ECG provides arrhythmia information of qualitative clinical relevance.

Ambulatory Care↗

PubMed1984

Detection of transient ischemic episodes by ambulatory ECG recordings.

In summary, ambulatory ECG monitoring detects episodes of S-T segment shifts with and without chest pain in patients with coronary heart disease. These most likely represent ischemic episodes. There is limited information available as yet for use of ambulatory monitoring as a screening test applied to totally asymptomatic individuals, particularly from populations in which the frequency of coronary artery disease is low. Equipment used for ambulatory ECG monitoring and methods of quantifying the ischemic episode require further evaluation. At present, ambulatory ECG monitoring can be used to objectively detect silent and symptomatic ischemic episodes and monitor effectiveness of therapy designed to prevent ischemia in individuals with ischemic heart disease.

Ambulatory Care↗

PubMed1987

Cardiac arrhythmias in healthy children revealed by 24-hour ambulatory ECG monitoring.

Ambulatory electrocardiographic monitoring was performed on 360 healthy children, from newborn infants to junior high school students. They were divided into five groups by age: group A, 63 newborn infants on the first day of life; group B, 50 infants aged 1-11 months; group C, 53 kindergarten pupils aged 4-6 years; group D, 97 primary school pupils aged 9-12 years; and group E, 97 junior high school students aged 13-15 years. The maximal and minimal heart rates were significantly greater in infants than in older children. Sinus arrhythmia was recorded in every child. One boy in group E had an episode of sinus arrest for three seconds without any symptoms. First-degree and Wenckebach type second-degree atrioventricular blocks were not detected in group A and group B, but were most frequent in group E, especially during sleep. Supraventricular premature contractions (SVPCs) were the most common type of arrhythmia detected in this study. More than half of the children had at least one SVPC per 24-h monitoring period, and there were many children with frequent SVPCs in group E. The incidence of ventricular premature contractions (VPCs) in children of groups A and E was rather higher than in the other groups. Ventricular tachycardia was not recorded in any child except one newborn infant who had a couplet of VPCs without symptoms. Each group had different types and incidences of arrhythmias. There was a rising incidence of arrhythmias with advancing age, except in the neonatal period.

Adolescent↗

PubMed1984

Chronic paroxysmal hemicrania: heart rate changes and ECG rhythm disturbances. A computerized analysis of 24 h ambulatory ECG recordings.

Ambulatory ECG recordings have been carried out in five patients suffering from CPH. During the study a total of 105 attacks occurred. Contrary to findings in cluster headache, no typical pattern of heart rate change was found in association with attacks of CPH. A striking finding in all patients, however, was that there were often large and rapid variations in heart rate which could be observed "before", "during" or "after" the attacks. One patient developed bradycardia and sino-atrial block and another bundle branch block together with episodes of atrial fibrillation in association with attacks.

Adult↗

PubMed1993

Prevalence and functional significance of transient ST-segment depression during daily life activity: comparisons of ambulatory ECG with stress redistribution thallium 201 single-photon emission computed tomographic imaging.

To assess the prevalence and functional significance of ischemic ambulatory ECG responses, we prospectively performed ambulatory ECG monitoring in 244 patients (mean age 61 +/- 10 years) referred for stress redistribution thallium 201 myocardial perfusion scintigraphy. The prevalence of ST-segment depression during ambulatory ECG was 33% among patients with a positive exercise ECG, but prevalence varied in selected patient subgroups. Among three groups with coronary artery disease (CAD), the group with ambulatory ECG ischemia (group 1) had a greater frequency of ischemic thallium responses (p = 0.07), a greater median number of reversible thallium defects (p < 0.05), and a greater summed thallium "reversibility" score (p < 0.05) than did the group with a positive exercise ECG but negative ambulatory ECG response (group 2) or that with negative exercise and ambulatory ECG responses (group 3). Exercise ST depression in group 1 versus group 2 was significantly greater (p = 0.002), occurred at a lower heart rate threshold (p = 0.002), and lasted longer after exercise (p = 0.001). Notably, one third of group 1 patients also manifested evidence of transient ischemic dilation of the left ventricle after exercise (p < 0.01 vs groups 2 and 3), a sign of severe ischemia. However, although functionally less "sick" than group 1 patients, 66% of group 2 patients and 50% of group 3 patients still had an ischemic thallium response, which was sometimes severe. Thus transient ischemia during ambulatory ECG monitoring identifies a functionally sicker cohort of patients with CAD and occurs in approximately one third of CAD patients with positive results of exercise tests. A negative ambulatory ECG response, however, does not exclude functionally significant disease among CAD patients. These results imply that caution should be applied in the interpretation of a negative ambulatory ECG response for the purpose of patient risk stratification.

Activities of Daily Living↗

PubMed1984

[The ambulatory ECG in the evaluation of coronary insufficiency].

To assess the diagnostic value of continuous ambulatory ECG in exercise angina pectoris, 49 males (mean age 52, 1 years), with exercise ischemic ECG changes and positive coronary angiography were evaluated. Ischemic ST-changes were detected by ambulatory ECG in 47% of those patients; most of these ST segment displacements were asymptomatic and a lot of them occurred at rest. In order to assess the specificity of ambulatory ECG, 90 healthy subjects (47 males and 43 females, mean age 43,6 years), were also evaluated 8.9% of these subjects developed ischemia like episodes of ST segment deviation. We conclude that in exercise angina pectoris the ambulatory ECG allows to recording silent ST segment changes, in spite of a poor diagnostic sensitivity. The low specificity of ST segment depression recorded by ambulatory ECG must be also emphasized.

Adult↗

PubMed1980

Use of the ambulatory ECG to diagnose coronary artery disease.

Forty-nine patients undergoing cardiac catheterization for suspected coronary artery disease (CAD) were monitored with a two-channel ambulatory ECG and were given maximal treadmill exercise tests when these were not contraindicated. The ambulatory ECG recordings were evaluated for the number of ST segment deviations after correction for positional changes, and the results were then compared with those of the exercise test and coronary angiography. Sensitivity and specificity of ambulatory ECG monitoring for ST segment deviations to detect CAD were 76% and 75% respectively while those of exercise testing were 78% and 63% respectively. Sixteen patients (33% of this series) had equivocal or contraindicated exercise tests and twelve of these patients were correctly classified as to the presence or absence of CAD by ambulatory ECG. ST segment deviations on ambulatory ECG were found in 93% of patients with three vessel, two vessel, or one vessel LAD disease, while exercise testing detected 74% of these patients. Ambulatory ECG is an effective non-invasive method to diagnose CAD and is complementary to excercise testing. It is of special value when the exercise test is equivocal or contraindicated.

Adult↗

PubMed1990

Improvement of the frequency responses in an ambulatory ECG system by the natural observation method.

The ambulatory ECG system has been used not only in detecting arrhythmia but also in the diagnosis of myocardial ischemia. Therefore, it is necessary to reproduce ECG waveforms as accurately as possible. However, ambulatory ECG waveforms which are in clinical use are apt to be distorted because the frequency responses do not satisfy the AHA (American Heart Association) recommendation which is well accepted as the standard of the conventional ECG system. An improvement of frequency response is reported here using a compensation circuit, whose theory is based on the natural observation method. Since our system is adjusted with square waveforms and composed of a simple analog circuit, it can be compensated easily in real time. In this paper, our newly developed system and various improved ECG signals are presented and compared with conventional ECG signals. As a result, we could obtain less distorted waveforms than from commercially available devices. This new approach enables us to obtain diagnostic information of the distortion-free ST segment in ECG waveforms.

Arrhythmias, Cardiac↗

PubMed1996

Holter triage ambulatory ECG analysis. Accuracy and time efficiency.

Triage ambulatory electrocardiographic (ECG) analysis permits relatively unskilled office workers to submit 24-hour ambulatory ECG Holter tapes to an automatic instrument (model 563, Del Mar Avionics, Irvine, CA) for interpretation. The instrument system "triages" what it is capable of automatically interpreting and rejects those tapes (with high ventricular arrhythmia density) requiring thorough analysis. Nevertheless, a trained cardiovascular technician ultimately edits what is accepted for analysis. This study examined the clinical validity of one manufacturer's triage instrumentation with regard to accuracy and time efficiency for interpreting ventricular arrhythmia. A database of 50 Holter tapes stratified for frequency of ventricular ectopic beats (VEBs) was examined by triage, conventional, and full-disclosure hand-count Holter analysis. Half of the tapes were found to be automatically analyzable by the triage method. Comparison of the VEB accuracy of triage versus conventional analysis using the full-disclosure hand count as the standard showed that triage analysis overall appeared as accurate as conventional Holter analysis but had limitations in detecting ventricular tachycardia (VT) runs. Overall sensitivity, positive predictive accuracy, and false positive rate for the triage ambulatory ECG analysis were 96, 99, and 0.9%, respectively, for isolated VEBs, 92, 93, and 7%, respectively, for ventricular couplets, and 48, 93, and 7%, respectively, for VT. Error in VT detection by triage analysis occurred on a single tape. Of the remaining 11 tapes containing VT runs, accuracy was significantly increased, with a sensitivity of 86%, positive predictive accuracy of 90%, and false positive rate of 10%. Stopwatch-recorded time efficiency was carefully logged during both triage and conventional ambulatory ECG analysis and divided into five time phases: secretarial, machine, analysis, editing, and total time. Triage analysis was significantly (P < .05) more time efficient for the machine, analysis, and total time phases and required significantly more time in the editing phases. The triage analysis was limited by the inability of the automatic methodology to detect a specific VT waveform contained on one tape. This result which caused substantial loss of sensitivity for VT, emphasizes the necessity for careful quality control and editing of all automatic Holter analysis methods.

Electrocardiography, Ambulatory↗

PubMed1975

Comparison of 24 versus 12 hours of ambulatory ECG monitoring.

In order to assess the additional information obtained from 24 hours compared to 12 hours of ambulatory ECG (electrocardiogram) recording, we analyzed 72 ambulatory ECG monitoring tapes in which arrhythmias were present. In all cases the second 12 hours included the entire period of sleep. Only 38 of 233 (16 percent) episodes of arrhythmias, frequent premature ventricular contractions (PVC's), two or more PVC's in a row, multiform PVC's, ventricular bigeminy, trigeminy, premature atrial contractions (PAC's), and supraventricular tachyarrhythmias occurred for the first time in the second 12-hour period. New ventricular arrhythmias were detected during the second 12-hour period in 13 percent of the arrhythmic episodes. Although sleep resulted in a marked decrease in PVC frequency in 63 percent of 30 recordings, with frequent PVC's while awake, 8 percent had a significant increase during sleep. In contrast, short runs of supraventricular tachyarrhythmias occurred during the second 12 hours in 48 percent of cases, 66 percent of these while asleep. These data suggest that a 24-hour ambulatory ECG tape recording be utilized initially to characterize the occurrence and frquency of the patients' ambulatory arrhythmias during awake and sleep periods. Thereafter, additional ECG recordings for monitoring antiarrhythmic drug therapy can be accomplished with a 12-hour recording in more than 80 percent of patients

Adolescent↗

PubMed1975

Pacemaker implantation based on ambulatory ECG monitoring in patients with cerebral symptoms.

Continuous ambulatory ECG monitoring was performed in 110 patients because of a history of dizziness, alleged syncope of vague cerebral manifestations. The resting ECG failed to provide an explanation for symptoms in any of the patients. In 12 patients the monitoring revealed a variety of arrhythmic mechanisms which required pacemaker implantation. Five of these patients had sick sinus syndrome with episodes of prolonged sinus arrest, while in the others various degrees of A-V block were detected. Implantation of a pacemaker relieved the symptoms in all. It is concluded that ambulatory ECG monitoring is essential in evaluating cases of unexplained cerebral symptoms.

Aged↗

PubMed2005

[Development of a portable ambulatory ECG monitor based on embedded microprocessor unit].

OBJECTIVE: To develop a new kind of portable ambulatory ECG monitor. METHOD: The hardware and software were designed based on RCA-CDP1802. New methods of ECG data compression and feature extraction of QRS complexes were applied to software design. A model for automatic arrhythmia analysis was established for real-time ambulatory ECG Data analysis. Compact, low power consumption and low cost were emphasized in the hardware design. RESULT: This compact and light-weight monitor with low power consumption and high intelligence was capable of real-time monitoring arrhythmia for more than 48 h. More than ten types of arrhythmia could be detected, only the compressed abnormal ECG data was recorded and could be transmitted to the host if required. CONCLUSION: The monitor meets the design requirements and can be used for ambulatory ECG monitoring.

Arrhythmias, Cardiac↗

PubMed1988

Ambulatory ECG (Holter) monitoring in management of acute myocardial ischemia.

Ambulatory ECG monitoring for detection of transient myocardial ischemia is useful because most ischemic episodes that occur outside the exercise laboratory are not accompanied by symptoms. Special considerations, not required for AEM when used for arrhythmia analysis, must be employed. Although many commercially available recorders provide excellent ST-segment reproduction, some playback systems may have a nonlinear phase response resulting in signal distortion, making ST-segment analysis difficult. Conventional Holter-type AEM devices do not allow for patient or physician intervention during acute myocardial ischemia. Considerable cost and time are required to analyze ST-segment data of prolonged monitoring periods from these tape-recorded signals, and human error and fatigue play an important role in diminishing accuracy of ST-segment interpretation. Automated analysis is done with computer and technician interaction but the accuracy and validation of the various systems for ST-segment analysis from tape recordings requires further detailed study. Newer, real-time ambulatory ECG analyzers are designed for prolonged monitoring periods and directed toward ST-segment analysis. Some devices also alert the patient to an acute ischemic or arrhythmic event allowing for intervention immediately. Some real-time systems have undergone some very encouraging validation studies. These recent studies suggest excellent sensitivity and specificity for detection of ischemic-type ST-segment depression. However, more work is needed before the accuracy of other such devices is known with certainty. As the central goal of therapy for patients with coronary artery disease evolves from simply controlling angina to reduction or elimination of ischemic episodes and their consequences, use of AEM devices will play an increasingly important role in management of these patients.

Ambulatory Care↗

PubMed1984

Clinical experience with a new dynamic display system for ambulatory ECG recordings.

The authors present the results of clinical experience with a new display for ECG signal presentation in ambulatory ECG monitoring. The new method has been devised by adding to contourography the dynamic effect produced by image movement and the perspective effect produced by pseudo-tridimensional presentation. The system has been developed using a microprocessor, a dynamic memory and an arithmetic unit which sends the signal on a CRT screen. Clinical experience, based upon 150 analyses, demonstrates the new method's marked efficiency in presenting rhythm disturbances and particularly ST-T segment alterations. Clinical validation has been performed comparing the results of 50 tapes analysed both with the new method and with different commercial systems. The new method provides useful information as to ST-T segment in 98% of cases and as to rhythm disturbances in 90%, while commercial systems reveal ST-T alterations in 84% and arrhythmias in 70% This method, being devoid of automaticity, does not yield false positives; dynamic and pseudo-tridimensional visualization of ECG signal allow the operator to perceive with high sensitivity alterations of the observed tracing.

Ambulatory Care↗

PubMedDate not supplied

Association of silent ST-segment depression on one-hour ambulatory ECGs with exposure to industrial noise among blue-collar workers in Israel examined at different levels of ambient temperature--the CORDIS Study.

BACKGROUND: Epidemiologic studies on the effects of ambient temperature or industrial noise on the cardiovascular system have usually focused on blood pressure. However, the ambulatory ECG may be a sensitive instrument for evaluating transient changes in the myocardium associated with exposure to such environmental stressors. In particular, the presence of silent ST-segment depression would strongly suggest transient myocardial ischemia. AIM: To evaluate a possible association between exposure to ambient noise and temperature in the workplace and silent ST-segment depression on short-term ambulatory ECGs. METHODS: Between 1985 and 1987, approximately 6,000 factory workers in Israel were examined in the framework of the CORDIS study. Each worker underwent ambulatory ECG monitoring for one hour. Measurements were taken of the average exposure to noise and the ambient temperature. Complete data including analysis of the ST-segment on the ambulatory ECG were available for 3,747 blue-collar workers. RESULTS: After excluding subjects with a history of heart disease, among men, silent ST-segment depression was found to be most prevalent in those workers exposed to more than 80 dBA compared with those exposed to less than 70 dBA. (RR = 2,4, p = .1 for men and RR = 1.3, p = .37 for women. Silent ST-segment depression was more prevalent at ambient temperatures up to 20 degrees C than over 25 degrees C (RR = 1.4, p = .22 for men and RR = 2.0, p = .005 for women). These trends persisted after controlling for possible confounding variables, such as age, type of work, smoking, and relative weight; however, only the temperature effects in women remained statistically significant. CONCLUSIONS: These findings suggest that silent ST-segment depression on ambulatory monitoring may be a sensitive measure of the cardiovascular response to exposure to physical stressors in the workplace. Exposures to noise and varying ambient temperature appear to have different effects on men and women.

Adult↗