Guidelines for ambulatory electrocardiography. A report of the American College of Cardiology/American Heart Association Task Force on Assessment of Diagnostic and Therapeutic Cardiovascular Procedures (Subcommittee on Ambulatory Electrocardiography)

Long-term ST database: a reference for the development and evaluation of automated ischaemia detectors and for the study of the dynamics of myocardial ischaemia

The long-term ST database is the result of a multinational research effort. The goal was to develop a challenging and realistic research resource for development and evaluation of automated systems to detect transient ST segment changes in electrocardiograms and for supporting basic research into the mechanisms and dynamics of transient myocardial ischaemia. Twenty-four hour ambulatory ECG records were selected from routine clinical practice settings in the USA and Europe, between 1994 and 2000, on the basis of occurrence of ischaemic and non-ischaemic ST segment changes. Human expert annotators used newly developed annotation protocols and a specially developed interactive graphic editor tool (SEMIA) that supported paperless editing of annotations and facilitated international co-operation via the Internet. The database contains 86 two- and three-channel 24 h annotated ambulatory records from 80 patients and is stored on DVD-ROMs. The database annotation files contain ST segment annotations of transient ischaemic (1155) and heart-rate related ST episodes and annotations of non-ischaemic ST segment events related to postural changes and conduction abnormalities. The database is intended to complement the European Society of Cardiology ST-T database and the MIT-BIH and AHA arrhythmia databases. It provides a comprehensive representation of 'real-world' data, with numerous examples of transient ischaemic and non-ischaemic ST segment changes, arrhythmias, conduction abnormalities, axis shifts, noise and artifacts.

Time course of cardiac structural, functional and electrical changes in asymptomatic patients after myocardial infarction: their inter-relation and prognostic impact

OBJECTIVES

We prospectively studied the relationship between left ventricular (LV) dilation, dysfunction, electrical instability and death in patients after a first myocardial infarction (MI) without symptoms of heart failure and ischemia.

BACKGROUND

Mechanisms linking LV dysfunction and sudden death in patients after MI remained controversial.

METHODS

Left ventricular volumes, hemodynamics, electrocardiogram and 24-h Holter recordings were sequentially obtained between two days and seven years after MI. Left ventricular catheterization and coronary angiography were performed, and revascularization was performed if appropriate.

RESULTS

Death occurred in 16 (12%) of the 134 patients included; it was of cardiac origin in 14 (88%) and sudden in origin in 12 (75%) patients. Of 37 (28%) patients with LV dilation, 12 died (32%); four patients (5.8%) died in the group without dilation. Left ventricular dilation was closely related to signs of electrical instability, as indicated by a significant correlation between end-diastolic LV volume index, Lown score (r = 0.98, p < 0.0001) and QTc prolongation (r = 0.998, p < 0.01), respectively.

CONCLUSIONS

Patients with progressive remodeling are at increased risk of sudden death in chronic MI. Cardiac electrical instability is closely related to progressive LV dilation. Parameters of electrical instability and remodeling are predictors of sudden death. The findings suggest that remodeling might serve as a link between dysfunction, electrical instability of the heart and sudden death after MI.

Clinical assessment of a new method for pacing pulse detection using a hybrid circuit in digital Holter monitoring

Holter monitoring is widely used for the detection of arrhythmia and ischemic episodes. Traditionally, analog amplitude-modulated Holter devices have been used for detecting arrhythmia, but they produce signal distortion due to contour effects and phase distortion caused by the tape recorders. A digital Holter device without these disadvantages has been developed and can reproduce clinically accurate electrocardiographic waveforms useful for assessment of arrhythmia and ST segments. However, their reliability is questionable when detecting pacing pulses in pacemaker patients. Because electrocardiographic signals are digitized based on sampling rate, pacing pulses are occasionally missed. Therefore, the FM-300 was developed, a new device for detecting pacing pulses on digital recordings that has both digital and analog circuits in one system and indicates pacing pulse timing with arrows. This device can automatically detect and recognize pacing pulses from various artifacts and pacing modalities, making it easy to identify pacing pulses on digitally recorded electrocardiograms. The FM-300 is useful in the diagnosis and assessment of pacemaker function and has improved the reliability of pulse detection in digital Holter monitoring.

Use of ambulatory electrocardiography for the detection of paroxysmal atrial fibrillation in patients with stroke. Canadian Task Force on Preventive Health Care

BACKGROUND

Patients with stroke commonly undergo investigations to determine the underlying cause of stroke. These investigations often include ambulatory electrocardiography to detect paroxysmal atrial fibrillation. There is conflicting evidence in the literature regarding whether routine ambulatory electrocardiography should be performed in all or selected stroke patients. This paper reviews the available evidence on (1) the yield of ambulatory electrocardiography in detecting paroxysmal atrial fibrillation in patients with stroke or transient ischemic attack and (2) the effectiveness of anticoagulation in preventing recurrent stroke in patients with paroxysmal atrial fibrillation.

METHODS

A MEDLINE search for primary articles was performed, and the references were reviewed manually. In addition, citations were obtained from experts. The evidence was systematically reviewed using the evidence-based methodology of the Canadian Task Force on Preventive Health Care.

RESULTS

Ambulatory electrocardiography can detect atrial fibrillation not found on initial electrocardiogram in between 1% and 5% of people with stroke. Ambulatory electrocardiography is generally safe. The risk of recurrent stroke in the setting of paroxysmal atrial fibrillation is uncertain, but appears to be similar to that seen with chronic atrial fibrillation (about 12% per year). Therapy with warfarin may reduce this risk by about two-thirds as compared to placebo. The annual risk of major bleeding with warfarin therapy is between 1% and 3% but rates for individual patients depend on various specific risk factors.

INTERPRETATION

There is insufficient evidence to recommend for or against the use of ambulatory electrocardiography for the detection of paroxysmal atrial fibrillation in either selected or unselected patients with stroke (C Recommendation). There is fair evidence to recommend therapy with warfarin for patients with stroke and paroxysmal atrial fibrillation (B Recommendation).

[Spanish Society of Cardiology practice guidelines on ambulatory monitoring of electrocardiogram and blood pressure]

In the present paper, a historical review and a clinical up-date are done on two procedures of great medical interest: Holter electrocardiography and ambulatory blood pressure monitoring. Technical and methodological characteristics of each procedure are carefully exposed, emphasizing each the lack of an international agreement in order to establish regulations that make all the equipment homogeneous and reliable in order to increase both accuracy and reliability in diagnosis. Based on published international scientific documents and the personal experience of the authors, guidelines for clinical applications, indications and limitations of each technique are analyzed in relation to capacities of the Spanish political and social public health system profile. New concepts and dynamics of developments such as; dynamic QT, RR variability or pulse wave velocity are exposed, in the frame of the present time and future for improving efficiency and clinical application.

The M cell: its contribution to the ECG and to normal and abnormal electrical function of the heart

The discovery and characterization of the M cell, a unique cell type residing in the deep layers of the ventricular myocardium, has opened a new door in our understanding of the electrophysiology and pharmacology of the heart in both health and disease. The hallmark of the M cell is the ability of its action potential to prolong much more than that of other ventricular myocardial cells in response to a slowing of rate and/or in response to agents that act to prolong action potential duration. Our goal in this review is to provide a comprehensive characterization of the M cell, its contribution to transmural heterogeneity, and its role in the normal electrical function of the heart, in the inscription of the ECG (particularly the T wave), and in the development of QT dispersion, T wave alternans, long QT intervals, and cardiac arrhythmias, such as torsades de pointes. Our secondary goal is to address the controversy that has arisen relative to the functional importance of the M cell in the normal heart. The controversy derives largely from the failure of some investigators to demonstrate transmural heterogeneity of repolarization in the dog in vivo under control conditions and after administration of quinidine. The inability to demonstrate transmural heterogeneity under these conditions may be due to the use of bipolar recording techniques that, in our experience, seriously underestimate transmural dispersion of repolarization (TDR). The use of sodium pentobarbital and alpha-chloralose as anesthesia also is problematic, because these agents reduce or eliminate TDR by affecting a variety of ion channel currents. Finally, attempts to amplify transmural dispersion of repolarization with an agent such as quinidine must take into account that relatively high concentrations can result in effects opposite to those desired due to drug inhibition of multiple ion channels. These observations may explain the inability of earlier studies to detect the M cell.

Detection of myocardial ischemia with a computer-assisted 12-lead 24-hour ECG monitoring system (EAGLE) in patients with suspected unstable angina

This study was undertaken to evaluate the diagnostic value of a new device, the 'EAGLE' computer-assisted multiple-lead long-term electrocardiography (ECG) monitoring and analyzing system, in patients with suspected unstable angina, and to compare the results with the Holter monitor. A total of 101 patients with a history of suspected unstable angina underwent a simultaneous 24-h examination with the EAGLE and 2-channel Holter monitors. The diagnosis of unstable angina was established in 70 patients: 41 had significant organic stenosis, and 29 had coronary spasm. Ischemic ST deviations were detected 229 times in 44 patients (62.9%) with the EAGLE system and 101 times in 20 patients (28.6%) with the Holter monitor. The sensitivity of myocardial ischemia in unstable angina with the EAGLE system was significantly higher than that with Holter monitor (62.9 vs 28.6%, p<0.05). The difference of sensitivity was due mainly to the low detection rate of the Holter monitor for asymptomatic myocardial ischemia (EAGLE vs Holter; 187 times vs 72 times) and myocardial ischemia in the infero-posterior area in patients with organic stenosis (30 times vs none). It is concluded that the EAGLE system is a sensitive tool for the diagnosis of unstable angina in patients without significant ECG changes, and an excellent tool for evaluating silent myocardial ischemia or myocardial ischemia of the infero-posterior area.

[I. Usefulness of the exertion test and other methods based on the electrocardiogram in chronic ischemic disease]

Exercise testing still plays an important role in the management of patients with chronic ischemic heart disease, not only in the diagnosis but also in their prognostic and functional evaluation, and in the assessment of effects of the therapy. Moreover, ambulatory electrocardiography, signal averaged electrocardiography and heart rate variability provide useful information for certain groups of patients. This paper reviews the rationale, methodology and indications of the above mentioned procedures applied to chronic ischemic heart disease, with special reference to exercise testing. Recommendations for their use in clinical practice are also made.

Assessment and significance of ST-segment changes detected by ambulatory electrocardiography after acute myocardial infarction

This study assessed the prognostic value of ST-segment changes detected by ambulatory electrocardiographic monitoring during the early in-hospital period after acute myocardial infarction. New methods for defining the ST-segment reference level and for measuring ST-segment elevation were used. ST-segment depression was defined as a change in ST level by > or = 0.1 mV 80 ms after the J point, elapsing > or = 1 minute. ST-segment elevation was defined as a deviation by > or = 0.15 mV, elapsing > or = 1 minute, and measured at the J point. An interval of > or = 2 minutes was required before another discrete episode was counted. Four ST-segment reference levels were automatically calculated: (1) "isoelectric," (2) "nearest to normal," (3) "24-hour median," and (4) "first-hour median." During a mean follow-up period of 3 years (mean 36 +/- 15 months), 47 cardiac events occurred in 38 patients: 18 deaths, 9 nonfatal reinfarctions, and 20 revascularization procedures. More deaths occurred in patients with than without ST elevation-24-hour median (22% vs 5%, p = 0.03), and in patients with than without ST depression-isoelectric (61% vs 32%, p = 0.02), and in patients with than without ST-depression-24-hour median (61% vs 23%, p = 0.003). "All cardiac events" (deaths, infarctions, or revascularization procedures) occurred more often in patients with than without ST depression-isoelectric (55% vs 22%, p = 0.003), and in patients with than without ST-depression-24-hour median (47% vs 17%, p = 0.004). Sensitivity, specificity, and accuracy of ST depression/elevation-24-hour median to assess mortality were 78%, 71%, and 73%, respectively.

Integration of absolute ventricular fibrillation voltage correlates with successful defibrillation

Previous work has suggested that at higher absolute ventricular fibrillation voltages (AVFV), the heart is more amenable to defibrillation. This study investigated in a canine model whether voltage integration of the AVFV is associated with the defibrillation success rate. The moving-average filter was used to process the ventricular fibrillation (VF) waveform recorded from Lead II of the electrocardiogram (ECG). In seven animals, defibrillation trials were analyzed using a dc shock (DCS) successful approximately 50% of the time when delivered randomly. For each of a total of 84 DCS (40% successes, 60% failures), the fibrillation waveform just prior to DCS was analyzed. The integration of the AVFV waveform was performed over various sample sizes including 1, 4, 8, 16, 64, and 128 ms, as well as the time equal to the mean VF cycle length. The results suggest that dc shocks delivered at instants of higher values of integrated AVFV over the various window sizes are associated with successful defibrillation. Window sizes less than 16 ms appeared to offer the best discrimination. The integration of AVFV over the entire VF cycle length was significantly higher for successful rather than unsuccessful DCS. This interesting observation is consistent with the clinical observation that "coarse" VF (high AVFV) is easier to defibrillate than "fine" VF (low AVFV). The use of voltage integration of AVFV may have potential implications in the improvement of defibrillation success in implantable devices.

An audit of utilisation of Holter tape facilities at Glasgow Royal Infirmary

Holter tape analysis is widely used to both confirm and exclude the presence of significant arrhythmias. We have studied the utilisation of the Holter service at Glasgow Royal Infirmary over a period of 6 months. During this period 305 x 24 hour Holter tapes were recorded. Out patient referrals generated 95% of these requests with only 5% of requests for in patient recordings. The median delay from request date to dispatch to the referring doctor was 14 days. No arrhythmia was detected in 77% and only 3% had a detectable symptomatic significant arrhythmia. The recording was felt to demonstrate the presence of a relevant arrhythmia in 17% of cases and to help exclude a possible arrhythmia in 61%. The capital cost per tape was 20.82 Pounds. In conclusion Holter monitoring is an inexpensive way of analysing the heart rhythm over an extended period which is probably underused.

Ventricular arrhythmias in Takayasu arteritis

We studied the prevalence, severity and clinical significance of ventricular arrhythmias in 78 female patients with Takayasu arteritis by 24-h ambulatory electrocardiography monitoring. Fifty (64%) of 78 patients had no or less than 30 beats/h premature ventricular contractions (Group A). The remaining 28 (36%) patients exhibited frequent or complex premature ventricular contractions (Group B). The frequency of HLA Bw52 which is closely associated with this morbid condition, echocardiographic and thallium-201 stress myocardial scintigraphic findings were then compared between these two groups. The frequency of positive HLA Bw52 was not significantly different between these two groups. Echocardiographically determined left ventricular mass (309 +/- 94 vs. 166 +/- 64 g; P < 0.01), frequency of complicated aortic regurgitation (77% vs. 24%; P < 0.01) and abnormal thallium-201 scintigraphic findings (76% vs. 38%; P < 0.05) were found higher in Group B as compared with those in Group A. These data indicate that frequent or complex ventricular arrhythmias in patients with Takayasu arteritis were associated with the presence of left ventricular hypertrophy, aortic regurgitation and decreased coronary reserve.

Morphologic characteristics of nonsustained ventricular tachycardia detected during Holter monitoring associated with atherosclerotic coronary artery disease

Nonsustained ventricular tachycardia (VT) is an important prognostic indicator of outcome in patients with organic heart disease. The morphologic features of nonsustained VT were examined by obtaining a derived 12-lead electrocardiogram (ECGD) from a 24-hour Holter recording in 22 patients with nonsustained VT associated with coronary artery disease. A total of 60 nonsustained VT episodes were recorded. Of these, 20 were uniform and 40 were multiform. The mean rate of uniform episodes was faster (140 +/- 32 vs 124 +/- 16 beats/min; p < 0.01) and the duration longer (5.3 +/- 2.0 vs 4.0 +/- 1.0 beats; p < 0.02) than the multiform episodes. The majority (87%) of multiform episodes had only 2 different QRS configurations on the ECGD. Four distinct patterns of QRS configurations were seen within individual multiform nonsustained VT runs: type I--the initial QRS complex has 1 morphology and all subsequent complexes have another configuration; type II--the initial and terminal QRS complex has similar configuration; type III--the first 2 QRS complexes have similar configuration and all subsequent complexes have another morphology; and type IV--the QRS complexes have alternating morphologic features. These 4 different patterns may be related to the mechanism of nonsustained VT (reentry versus automaticity). Patients with multiple episodes of nonsustained VT frequently had differing patterns and morphologic features between episodes. Further studies are needed to evaluate the clinical importance of these findings.

Anginal symptoms without ischemic electrocardiographic changes during ambulatory monitoring in men with coronary artery disease

Episodes of angina pectoris without electrocardiographic (ECG) signs of myocardial ischemia during 24-hour ambulatory monitoring were studied in 128 patients with a history of stable angina, angiographically proven coronary artery disease and positive exercise test results. In all, 341 episodes of ischemic ECG changes (ST-segment depression greater than 1 mm for greater than 1 minute) and 190 episodes of angina pectoris were observed: 86 episodes consisted of both ECG changes and angina pectoris, 255 episodes consisted only of ECG changes, and 104 episodes only of angina pectoris. Duration and magnitude of ST-segment deviation and heart rate at the onset of ischemia were similar in the 86 symptomatic and the 255 asymptomatic episodes with ECG changes. The 104 episodes of angina pectoris without ECG changes were detected in 44 patients (34%) (group A); 29 of them had only episodes with angina pectoris and 15 patients had both--episodes of angina pectoris with and without ECG changes. In 84 patients (66%) (group B) angina pectoris without ECG changes was not observed; all episodes were accompanied by ischemic ECG changes in these patients. No differences in the angiographic extent of coronary artery disease and in exercise test data were seen in both groups A and B; however, maximal ST-segment depression during exercise testing was significantly greater in group B than in group A patients (2.4 +/- 0.8 mm vs 1.9 +/- 0.9 mm; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Practice guidelines to reduce testing in the hospital

OBJECTIVE

To reduce testing among hospitalized patients using practice guidelines for any of 14 medical problems.

DESIGN

Comparison of test use before and after implementation of guidelines. The guidelines were developed by consensus panels of self-selected participating physicians. Non-participating physicians were monitored during the same periods. In addition, the two groups of physicians were evaluated similarly for their management of three medical problems for which guidelines were not developed.

SETTING

Acute care hospital.

PATIENTS/PARTICIPANTS

1,638 hospitalized patients and their 79 physicians.

INTERVENTION

Implementation of practice guidelines for the care of hospitalized patients.

MEASUREMENT AND MAIN RESULTS

Geometric mean charges expressed in inflation-adjusted dollars were used as measures of test use. For the intervention group, laboratory tests decreased by 20.6%, x-rays by 42.3%, and EKGs by 34.2%. All the decreases were significant (p = 0.001). The non-participating physicians who were higher test users during both years of the study also achieved significant (p less than 0.05) but smaller reductions during the intervention year: 13.9% for laboratory tests, 30.3% for x-rays, and 21.8% for EKGs, perhaps because the same residents were involved in the care of both groups of patients. For the non-guideline diagnoses, the participating physicians achieved reductions of 11.1% for laboratory tests and 19.2% for x-rays, and a 3.5% increase in EKGs. Two-way analyses of variance that took into account the reductions in testing achieved by non-participants, or by participants with non-guideline diagnoses, revealed no significant reduction in testing attributable directly to the guidelines except for EKGs. Follow up of the participating physicians during the six months after the end of the intervention revealed that testing remained at the lower level achieved while the guidelines were in use. Outcome of care, as measured by deaths in the hospital, deaths within 90 days of discharge, and readmissions within 90 days of discharge, was not affected by the use of the guidelines.

CONCLUSIONS

1) A large group of physicians could be recruited in a hospital to establish practice guidelines by group consensus. 2) These self-selected physicians were willing to use the guidelines (or allow the housestaff to use them) while caring for their patients. 3) Participating physicians were able to achieve substantial and significant reductions in testing without any demonstrable adverse effect on quality of care as measured by deaths and readmissions, and without any demonstrable shifting of resources from the inpatient to the outpatient setting of care. 4) The reductions in testing, whether caused by the guidelines or not, persisted for at least six months beyond the end of the period of implementation.