Exercise electrocardiogram testing: beyond the ST segment.
Explore the source record for details and available documents.
Coronary Disease↗
Biomedical subjects
Paul Kligfield
Publications and source records attributed to Paul Kligfield.
Relation of QT interval measurements to evolving automated algorithms from different manufacturers of electrocardiographs.
QT-interval measurements have clinical importance for the electrocardiographic recognition of congenital and acquired heart disease and as markers of arrhythmogenic risk during drug therapy, but software algorithms for the automated measurement of electrocardiographic durations differ among manufacturers and evolve within manufacturers. To compare automated QT-interval measurements, simultaneous paired electrocardiograms were obtained in 218 subjects using digital recorders from the 2 major manufacturers of electrocardiographs used in the United States and analyzed by 2 currently used versions of each manufacturer's software. The 4 automated QT and QTc durations were examined by repeated-measures analysis of variance with post hoc testing. Significantly larger automated QT-interval measurements were found with the most recent software of each manufacturer (12- to 24-ms mean differences from earlier algorithms). Systematic differences in QT measurements between manufacturers were significant for the earlier algorithms (11-ms mean difference) but not for the most recent software (1.3-ms mean difference). Similar relations were found for the rate-corrected QTc, with large mean differences between earlier and later algorithms (15 to 26 ms). Although there was a <2-ms mean difference between the most recent automated QTc measurements of the 2 manufacturers, the SD of the difference was 12 ms. In conclusion, reference values for automated electrocardiographic intervals and serial QT measurements vary among electrocardiographs and analysis software. Technically based differences in automated QT and QTc measurements must be considered when these intervals are used as markers of heart disease, prognosis, or arrhythmogenic risk.
Algorithms↗
Consideration of pitfalls in and omissions from the current ECG standards for diagnosis of myocardial ischemia/infarction in patients who have acute coronary syndromes.
The ECG is the key clinical test available for the emergency determination of which patients who presenting with acute coronary syndromes indeed have acute myocardial ischemia/infarction. Because typically the etiology is thrombosis, the correct clinical decision regarding reperfusion therapy is crucial. This review follows the efforts of an AHA working group to develop new standards for clinical application of electrocardiology. The pitfalls in the current diagnostic standards regarding ischemia/infarction that have been identified by sufficiently documented studies are corrected in their report. This article focuses on the pitfalls for which new standards will emerge in future years.
Angina, Unstable↗
Ethnic differences in barriers and referral to cardiac rehabilitation among women hospitalized with coronary heart disease.
Important gender differences in cardiac rehabilitation utilization are well established, yet few studies have documented whether reported barriers and referrals vary by ethnicity. This is a cross-sectional study to determine whether barriers and referrals to participation in cardiac rehabilitation differed by race/ethnicity in 304 women (52% ethnic minorities) hospitalized with coronary heart disease. Nearly all subjects (92%) strongly agreed that physician referral was important to participation in rehab, but only 22% of subjects reported physician instruction to attend. Whites were more likely than minorities to report instruction to attend cardiac rehabilitation, and minorities were more likely to report financial barriers when compared with whites. These disparities need to be addressed because minority women have a worse prognosis following hospitalization for coronary heart disease, and cardiac rehabilitation has been shown to improve survival.
Aged↗
Rethinking the exercise electrocardiogram.
Explore the source record for details and available documents.
Coronary Disease↗
Effect of right bundle branch block on electrocardiographic amplitudes, including combined voltage criteria used for the detection of left ventricular hypertrophy.
BACKGROUND: Although right bundle branch block (RBBB) delays right ventricular depolarization, its effect on cancellation of right and left ventricular forces within the QRS complex has not been quantified during stable temporal and physiological conditions. Systematic changes in QRS amplitude during transient RBBB bear directly on performance of standard ECG criteria for left ventricular hypertrophy (LVH), and these changes require quantification. METHODS: We examined the instantaneous effect of RBBB on QRS amplitudes and LVH voltages in 40 patients who had intermittent complete RBBB during a single 10 sec standard 12-lead ECG recording, comprising 0.1% of approximately 400,000 consecutive ECGs in a university teaching hospital setting. Amplitudes were measured by magnifying graticule to the nearest 25 microvolts, averaged for up to 3 normal and 3 RBBB complexes, and compared by paired t test. RESULTS: RBBB was associated with an increase in initial QRS forces (RV1, RV2, and QV6) but significant decreases in mean mid-QRS amplitudes that reflect left ventricular depolarization (RaVL [-75 microvolts], SV1 [-389 microvolts], SV3 [-617 microvolts], RV5 [-100 microvolts], and RV6 [-123 microvolts]). All late QRS forces were increased with RBBB (R'V1, SV5, SI). As a result, combined voltages used for LVH criteria were significantly reduced by RBBB: Sokolow-Lyon voltage decreased from 1520 +/- 739 to 1014 +/- 512 microvolts (p < 0.001), and Cornell voltage decreased from 1438 +/- 683 to 746 +/- 399 microvolts (p < 0.001). CONCLUSIONS: RBBB is associated with significant reduction in "left ventricular" QRS amplitudes of the standard ECG, consistent with cancellation, rather than unmasking, of left ventricular mid-QRS forces by altered septal and delayed right ventricular depolarization. Because QRS voltages that are routinely combined for the detection of LVH are reduced in RBBB, standard LVH criteria will perform with lower sensitivity in patients with RBBB.
Aged↗
Prognostic impact of systolic hypertension on asymptomatic patients with chronic severe aortic regurgitation and initially normal left ventricular performance at rest.
The influence of systolic hypertension (SH) on the natural history of chronic aortic regurgitation (AR) and the clinical effect of antihypertensive medication on patients who have hypertension and AR are incompletely defined. Therefore, we reviewed the clinical course of 80 unoperated patients who were entered prospectively into an assessment of natural history of AR and its predictors and were asymptomatic with normal left ventricular ejection fraction (LVEF) at rest at study entry; 30 of 80 patients had SH (systolic blood pressure >140 mm Hg); 20 of 80 patients (16 had SH) used antihypertensive drugs for the long term (not mandated by protocol). During an average 7.2-year event-free follow-up, 24 patients developed symptoms alone (n = 14), subnormal LVEF with or without symptoms (n = 8), or died suddenly (n = 2). SH tripled the average annual risk of cardiac events (8.47% vs 2.85%, p = 0.004). The effect of systolic blood pressure was independent of age, gender, diastolic blood pressure, LV diastolic dimension, fractional shortening, and LVEF at rest (p = 0.004 to <0.008). However, positive prognostic interactions existed between systolic blood pressure and pulse pressure (p <0.001), LVEF during exercise (p <0.001), change in LVEF from rest to exercise (p <0.001), and the contractility index (p <0.02). Among patients who had SH, antihypertensive therapy predicted increased event risk (average annual risk 15.46% vs 3.98%, p <0.02) and remained predictive when analysis was adjusted for potentially confounding subgroup variations at study entry (p <0.03, all models). In conclusion, SH portends poor clinical outcome in chronic severe AR. As a group, antihypertensive drugs do not mitigate outcome, although the effect of individual drugs is uncertain and at least some may be deleterious. The theoretically based practice of giving antihypertensive drugs to patients who have AR requires reexamination.
Adult↗
Severe ataxia caused by amiodarone.
Neurologic toxicity is an infrequently reported and under-recognized consequence of amiodarone, symptoms of which may include tremor, peripheral sensorimotor neuropathy, proximal weakness, and ataxia. The investigators report the rapid and complete remission of 4 months of progressively debilitating ataxia with the discontinuation of small-dose amiodarone in an elderly woman with hypertrophic obstructive cardiomyopathy and paroxysmal atrial fibrillation. Despite the long half-life of amiodarone, her symptoms began to reduce after several days, and she was walking without assistance within 1 week. Wider recognition of this syndrome may avoid unnecessary and lengthy diagnostic evaluation and promote earlier neurologic recovery.
Aged, 80 and over↗
Anatomic distribution of myocardial ischemia as a determinant of exercise-induced ST-segment depression.
Cardiac single-photon emission computed tomographic correlates of ST depression were examined in 129 subjects who had inducible ST depression of > or =0.1 mV and reversible perfusion defects. Patients were separated on the basis of single-photon emission computed tomographic defect distribution into a group with anatomically contiguous ischemia (anterior or posterior/inferior defects, n = 68) and a group with anatomically opposed ischemia (anterior and posterior/inferior defects, n = 61). ST depression in the contiguous ischemia group correlated with defect size (r = 0.40, p = 0.001) and severity (r = 0.38, p = 0.002); multivariate regression demonstrated each to be independent determinants of ST-depression magnitude (r = 0.51, p <0.001). In the opposed ischemia group, ST depression did not significantly correlate with defect extent or severity. After adjusting for differences in perfusion indexes, ST depression was paradoxically greater in the contiguous than in the opposed group (2.82 +/- 1.15 vs 2.44 +/- 1.15 mm, p <0.001). In conclusion, these findings demonstrate that the anatomic distribution of ischemia can alter the relation between ST depression and functional indexes of ischemia and may confound the accuracy of assessments of coronary artery disease based on ST-depression magnitude alone.
Aged↗
Exercise testing in asymptomatic adults: a statement for professionals from the American Heart Association Council on Clinical Cardiology, Subcommittee on Exercise, Cardiac Rehabilitation, and Prevention.
Along with coronary artery calcium scanning, ankle-brachial index measurement, and carotid artery ultrasound, exercise electrocardiography has been proposed as a screening tool for asymptomatic subjects thought to be at intermediate risk for developing clinical coronary disease. A wealth of data indicate that exercise testing can be used to assess and refine prognosis, particularly when emphasis is placed on nonelectrocardiographic measures such as exercise capacity, chronotropic response, heart rate recovery, and ventricular ectopy. Nevertheless, randomized trial data on the clinical value of screening exercise testing are absent; that is, it is not known whether a strategy of routine screening exercise testing in selected subjects reduces the risk for premature mortality or major cardiac morbidity. The writing group believes that a large-scale randomized trial of such a strategy should be performed.
Adult↗
Harold Ensign Bennet Pardee.
Explore the source record for details and available documents.
Cardiology↗
The effects of enhanced external counterpulsation on myocardial perfusion in patients with stable angina: a multicenter radionuclide study.
BACKGROUND: Enhanced external counterpulsation (EECP) reduces angina and extends time to exercise-induced ischemia in patients with symptomatic coronary disease. One- and two-center studies and a retrospective case series reported that EECP improves myocardial perfusion in stable angina pectoris. We sought to critically evaluate and quantify the effect of EECP on myocardial perfusion. METHODS: In 6 US university hospitals, EECP was performed for 35 hours in patients with class II to IV angina who had exercise-induced myocardial ischemia. Symptom-limited quantitative gated technetium Tc 99m sestamibi single photon emission computed tomography exercise perfusion imaging was performed at baseline and 1 month post-EECP. Sestamibi was injected at the same heart rate in both stress tests. Single photon emission computed tomography images were read at a blinded core laboratory. RESULTS: Thirty-seven patients were enrolled, 34 of whom completed pre- and post-EECP stress testing. The mean age was 61 +/- 10 years, 81% were male, 78% had prior revascularization, and 68% had 3-vessel disease. The mean angina class decreased from 2.7 +/- 0.7 at baseline to 1.7 +/- 0.7 after EECP (P < .001). Exercise duration increased from 9.1 +/- 3.7 minutes at baseline to 10.2 +/- 3.6 minutes post-EECP (P = .03). The average percentage of tracer uptake, magnitude of reversibility, average thickening fraction, and the left ventricular ejection fraction remained unchanged after EECP. CONCLUSIONS: We confirm previous report that EECP reduces angina and improves exercise capacity. There were no significant changes in mean defect magnitude, amount of reversibility, thickening fraction, and ejection fraction measured using myocardial quantitative single photon emission computed tomography imaging when compared at identical pre- and post-EECP heart rates.
Angina Pectoris↗
Diagnostic performance of a computer-based ECG rhythm algorithm.
We examined the accuracy of computer-based rhythm interpretation from one electrocardiograph manufacturer (GE Healthcare Technologies MUSE software 005C) in 4297 consecutive recordings in a university hospital setting. Overreading was performed by either of 2 experienced cardiologists, and all disagreements with the initial computer rhythm statement were reviewed by the second cardiologist to achieve physician consensus used as the "gold standard" for rhythm diagnosis. Overall, 13.2% (565/4297) of computer-based rhythm statements required revision, but excluding tracings with pacemakers, the revision rate was 7.8% (307/3954), including 3.8% involving the primary rhythm diagnosis and 3.9% involving definition of ectopic complexes. The false-negative rate for sinus rhythm was only 1.3%, but a computer diagnosis of sinus rhythm was incorrect in 9.9% of other rhythms. The false-negative rate for atrial fibrillation was 9.2%, whereas a computer diagnosis of atrial fibrillation was incorrect in 1.1% of other rhythms, including sinus. Computer diagnosis of paced rhythms remains problematic, and physician overreading to correct computer-based electrocardiogram rhythm diagnoses remains mandatory.
Algorithms↗
The ISCE ECG genome pilot challenge: a 2004 progress report.
The International Society for Computerized Electrocardiography (ISCE) "genome project" began in 2000 as an open-ended discussion of ECG database needs and opportunities. Cooperation within ISCE led to a "pilot challenge" of the database concept, which called for establishment of methodology for transmission, storage, and integrated re-analysis of digitized waveforms of three different ECG manufacturers. The present report documents the early implementation of that goal.
Database Management Systems↗
Effect of age and gender on heart rate recovery after submaximal exercise during cardiac rehabilitation in patients with angina pectoris, recent acute myocardial infarction, or coronary bypass surgery.
The effect of exercise training on the heart rate recovery (HRR) response to submaximal effort was examined in 81 patients during 12 weeks of phase II cardiac rehabilitation. Although HRR after submaximal effort was relatively reduced in older patients with heart disease and in women, its increase during exercise training in men and women of all ages was consistent with enhancement of parasympathetic tone during activities of daily living.
Activities of Daily Living↗
Significance of QT dispersion.
Explore the source record for details and available documents.
Artifacts↗
Overview of the ISCE ECG "genome project".
The International Society for Computerized Electrocardiography (ISCE) "genome" project was begun at the end of 2000 to explore mechanisms for development of a cross-platform electrocardiogram (ECG) database. Ultimate feasibility of this project is based on established interactive cooperation of clinical investigators, engineers, and industry within the ISCE framework. The US Food and Drug Administration (FDA) mandate for centralized access to digitized ECG waveforms used in clinical trials provides a complementary stimulus to technologies that facilitate ECG database development. The constituency of ISCE is interested in acquisition and analysis of data from both standard 12-lead (resting) ECG and ambulatory (monitoring) ECG. Support for project goals from industry, at the Trustee as well as at the engineering level, has led to initial focus on the resting ECG. A one-year pilot project has been proposed to establish and implement software methodology for transmission, storage, and integrated reanalysis of digitized ECG waveforms provided by several major manufacturers. Beyond data acquisition, storage, and analysis, a number of critical issues are associated with database development. These include definition of clinically relevant "gold" standards, acquisition and validation of non-ECG data, protection of patient privacy, control and ownership of data, and accessibility and use of the database. However, implementation of the pilot project is a necessary first step, since all issues become moot without technical cooperation for shared formatting and analysis.
Databases as Topic↗