The quest for optimal electrocardiography. Task Force III: Computers in diagnostic electrocardiography.
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The quest for optimal electrocardiography. Task Force VI: Future directions in electrocardiography.
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Body Surface Area↗
The impact of computers on electrocardiography.
The development of the electrocardiograph was the culmination of a scientific effort aimed at perfection of a device conceived for the elucidation of a physiologic phenomenon. The development of the digital computer was the culmination of a scientific effort aimed at perfection of warfare. Both of these fairly recent innovations of modern technology have been moderately successful in their initial objectives. Electrocardiography has had a profound influence on the practice of medicine. On the global scene, computers have so far had an insignificant influence on the practice of electrocardiography. In North America, however, computer interpretation of ECGs has already made a modest impact, perhaps more in terms of commercial gains rather than producing a substantial benefits to health care. The introduction of computers into clinical electrocardiography has not resulted in any widespread application of improved diagnostic criteria. The automation of ECG interpretation has not resulted in reduction of the cost of health care, on the contrary, in general it has increased the cost. Perhaps the most dismal failure has been the negligible use of computers in epidemiologic studies and heart disease prevention efforts. Palmistry, astrology, the art of palpation of the pulse, auscultation and acupuncture have had a more profound influence on the practice of medicine than computer analysis of the electrocardiogram. On the positive side, one of the beneficial effects of the use of computers has been the increasing awareness of the limited diagnostic accuracy of currently used ECG criteria, and the recognition of the fact that a substantial improvement is warranted; if such improvement can not be achieved in the foreseeable future, electrocardiography will lose much of its current clinical utility. Computers have had a profound influence on research in electrocardiology, and although a very few tangible concrete results have thus far diffused into clinical electrocardiography, their impact can be expected during the last two decades of this century. Computers will produce at least containment of costs if not actual net cost reduction in clinical electrocardiography. Computer analysis will rapidly antiquate the present primitive visual ECG classification in epidemiologic studies and clinical heart disease intervention trials. Computer analysis will enhance the diagnostic accuracy of the electrocardiogram. However, a radical departure from the current ECG display and interpretation practice will be mandatory before any substantial breakthrough can be materialized. All these anticipated evolutionary and perhaps even revolutionary changes will require a continuing intensive research effort, a change in the professional attitude of practicing electrocardiographers and a considerable effort in professional education. Finally, the elucidation and exploration of the full diagnostic and predictive value of the ECG remains the challenge of first magnitude in electrocardiography...
Adult↗
Preoperative electrocardiography: its cost-effectiveness in detecting abnormalities when a previous tracing exists.
In 812 patients who underwent routine preoperative electrocardiography a mean of 24.6 months after undergoing electrocardiography at the same institution, the frequency of new abnormalities was estimated to evaluate the cost-effectiveness of this procedure prior to an operation. New abnormalities were judged to be either relevant or irrelevant to the assessment of operative risk, depending upon their previously demonstrated correlation with operative and postoperative morbidity and mortality. Since new abnormalities, especially new relevant abnormalities, were found to be relatively infrequent, the cost-effectiveness of routine preoperative electrocardiography was considered to be low. The evidence suggested that when a previous tracing exists preoperative electrocardiography is most clearly indicated for patients who are 60 years of age or older or whose previous tracing exhibited abnormalities. However, further research is required to develop more sensitive and specific protocols, and to evaluate the role of repeat electrocardiography in clinical decision-making.
Cost-Benefit Analysis↗
Exercise electrocardiography and myocardial perfusion imaging in the diagnosis of coronary artery disease: preliminary report.
Exercise electrocardiography and rest/exercise myocardial perfusion imaging with thallium-201 were performed in 43 patients with typical angina or atypical chest pain; the results were correlated with those of coronary arteriography. Exercise electrocardiography sensitivity was 65%, specificity was 78%, predictive value for a positive result was 73% and for a negative result was 93%. The low sensitivity of the exercise electrocardiogram was mainly due to the number (13 of 43, 30%) of inconclusive results (no ST-segment change on the electrocardiogram, but failure to attain the target rate), most of which were in the group with typical angina. The predictive value of exercise electrocardiography for both a positive and negative result was excellent in typical angina. In patients with atypical chest pain, the negative predictive value was high (90%) but the positive predictive value was very low (50%). The sensitivity of myocardial perfusion imaging was 71%, specificity was 59%, positive predictive value was 52% and negative predictive value 89%. The low specificity of this test is related to the number of false-positive results obtained, most of which occurred in the group with atypical pain. When the results of exercise electrocardiography and myocardial perfusion imaging are combined, the sensitivity is increased but specificity is unacceptably low. However, myocardial perfusion imaging in patients with an inconclusive result from exercise electrocardiography (most of them in the group with typical angina) showed a sensitivity of 80%, specificity of 88%, positive predictive value of 80% and negative predictive value of 100%.
Coronary Circulation↗
Myocardial perfusion imaging with thallium-201: correlation with coronary arteriography and electrocardiography.
Myocardial perfusion imaging with thallium-201 and electrocardiography with the subject at rest and undergoing submaximal treadmill exercise were performed in 19 men and 3 women. Selective coronary arteriography and left ventriculography showed that 7 had normal coronary arteries and 15 had coronary artery disease.The 11 persons with electrocardiographic evidence of an old myocardial infarct (q waves) had a perfusion defect at rest in the area of the infarct and a segmental abnormality of wall motion apparent on the left ventriculogram corresponding to the perfusion defect.MYOCARDIAL PERFUSION IMAGING AND ELECTROCARDIOGRAPHY WERE EQUALLY SENSITIVE IN DETECTING CORONARY ARTERY DISEASE IN EXERCISING INDIVIDUALS: perfusion defects were noted in 7 of the 15 persons with coronary artery disease, and diagnostic ST-segment depression was present in 8 of the 15. Combination of the results of the two tests with exercise permitted the identification of 11 of the 15 persons and improved the sensitivity. Combination of the results of rest and exercise imaging and electrocardiography permitted the identification of 94% of the patients with coronary artery disease.Myocardial perfusion imaging with (201)TI in the subject at rest is a sensitive indicator of previous myocardial infarction. Imaging after the subject has exercised is a useful adjunct to conventional exercise electrocardiography, especially in those whose exercise electrocardiogram is non-interpretable.
Adult↗
Single injection thallium-201 stress and redistribution myocardial perfusion imaging: comparison with stress electrocardiography and coronary arteriography.
The efficacy of single injection thallium-201 exercise stress and rest redistribution imaging in the evaluation of myocardiacl ischemia was compared with stress electrocardiography and coronary arteriography. Thallium-201 imaging was interpreted at two levels of sensitivity in order to define the circumstances under which it best serves as a screening modality for coronary arteriography. With the prevalence of coronary disease usually found in patients referred for coronary arteriography (75%), unprocessed thallium-201 imaging is as good as stress electrocardiography in identifying patients apt to show coronary artery abnormalities, but not much better than stress electrocardiography in delineating those patients unlikely to show coronary artery disease. In contrast, processed lesion enhanced images showing normal results virtually eliminate the possibility of significant arteriographic findings. With this screening technique, many patients may be spared unnecessary coronary arteriography.
Adult↗
[Comparison of 24 hours ambulatory electrocardiography and endocavitary recording in the diagnosis of heart rate disorders].
Ninety symptomatic patients aged between 16 and 90 years were investigated by ambulatory continuous 24 hour electrocardiography. 75 of these patients underwent endocavitary exploration of atrioventricular conduction and sinus node function within 48 hour of ambulatory electrocardiography. Symptoms occurred during the recording in 30% patients, enabling the mechanism of the malaise to be determined. Every time that abnormalities in the zone surrounding the Tawara node were demonstrated by endocavitary recordings, the 24 hour electrocardiogramme showed the symptoms to be due to other causes than complete heart block. In 70% patients no symptoms were experienced but 58% of them had cardiac arrhythmias and particularly sinus node dysfunction (24 out of 37 patients) on the 24 hour electrocardiogramme. Comparing the results of these two methods of investigation, continuous electrocardiography appears to be a better technique for the diagnosis of sinus node dysfunction but endocavitary study of sinus node function would seem more suited to determine its severity. Endocavitary recordings seem more reliable in the investigation of paroxysmal atrioventricular blocks. These results demonstrate the complementary nature of these two methods in determining the causes of syncope and dizziness.
Adolescent↗
Development of Electrocardiography Standards for Evaluating Myocardial Infarction and Ischemia-Reperfusion Injury in Mice.
BACKGROUND: Acute and chronic heart failure secondary to myocardial infarction (MI) and cardiac ischemia-reperfusion injury (IRI) are leading causes of death in ischemic heart disease. A mouse model is indispensable for investigating MI and IRI, and the development of reliable mouse MI and IRI models is essential for advancing research in this field. The clear early diagnostic criteria for confirming successful induction of MI and IRI in mice remain lacking. METHODS: Adult C57BL/6J background mice underwent left anterior descending coronary artery ligation to induce acute MI, or ligation followed by reperfusion to induce IRI. The success of the MI and IRI model establishment was confirmed by 2,3,5-triphenyltetrazolium chloride staining and echocardiography. Electrocardiography was used to monitor the electric activity in the mice. CONCLUSIONS: Electrocardiography demonstrated that ST-segment elevation in ECG lead II and corrected QTc interval prolongation at 30 minutes following left anterior descending ligation as 2 key early indicators of successful MI. Echocardiography analysis revealed that the magnitude of ST-segment elevation strongly correlated with the left anterior descending ligation site, where a more proximal ligation produced a greater ST-segment elevation amplitude and more severe ischemia. In IRI models, ST-segment elevation typically resolved and returned to baseline within 20 minutes of reperfusion. This study developed quantifiable early diagnostic criteria for successful MI and IRI induction based on characteristic ECG changes. These quantifiable ECG parameters provide early diagnostic standards that can significantly streamline and optimize modeling procedures.
Animals↗
Extent and severity of coronary heart disease. Determinations by thallous chloride Tl 201 myocardial perfusion scanning and comparison with stress electrocardiography.
Rest and exercise ECGs are the most widely used "noninvasive" tests for detecting coronary heart disease, but their sensitivity and specificity are suboptimal. Therefore, the diagnostic value of myocardial perfusion scanning using thallous chloride Tl 201 during rest and stress electrocardiography was examined in 95 patients with a chest discomfort syndrome. Overall, thallous chloride Tl 201 perfusion scanning had a sensitivity of 75% and a specificity of 91% for coronary heart disease compared with 56% sensitivity and 86% specificity with exercise-induced ST segment depression on the ECG. Combining rest and stress ECGs resulted in a sensitivity of 71%. In patients with coronary heart disease, perfusion scanning had a sensitivity of 93% for asynergy compared with 58% for exercise-induced ECG ST depression. Rest and stress myocardial perfusion scanning with thallous chloride Tl 201 provides improved sensitivity with good specificity in the diagnosis of coronary heart disease compared with exercise electrocardiography alone.
Arrhythmias, Cardiac↗
Myocardial stress perfusion scintigraphy with rubidium-81 versus stress electrocardiography.
Fifty-six patients who subsequently underwent selective coronary angiography were studied noninvasively with relative myocardial perfusion scintigraphy with rubidium-81 and graded stress electrocardiography in an attempt to evaluate the ability of these tests to identify the presence of significant ischemia and, indirectly, coronary stenosis. Both the sensitivity (0.91) and specificity (0.91) of perfusion scintigraphy were impressive and better than the sensitivity (0.79) and specificity (0.64) of stress electrocardiography, the specificity of scintigraphy significantly so (P less than 0.05). Additionally, perfusion scintigraphy yielded excellent localizing information and was reliable even in the presence of drug effect, conduction abnormalities and nonspecific electrocardiographic abnormalities. Rare cases of triple vessel disease, prior myocardial infarction or single vessel disease with widespread collateral vessels were causes of scintigraphic misdiagnosis. Although ribidium-81 perfusion scintigraphy with the scintillation camera requires special collimation and significant quality control, it provides well resolved images and may prove particularly useful in facilitating quick successive multiple scintigraphic cardiac studies.
Angina Pectoris↗
Ambulatory electrocardiography. A clinical perspective.
Advances in modern technology have made it possible to record and analyze the electrocardiographic data of ambulatory persons for as many as 24 h or more. This capability and an increasing awareness of cardiac dysrhythmias and myocardial ischemia as a cause of morbidity and mortality have led to the more widespread use of ambulatory electrocardiography in the examination of patients for various clinical conditions. From a clinical viewpoint, we review and summarize the present state-of-the-art of ambulatory electrocardiography and discuss when such studies are indicated, frequently warranted, or may be useful.
Aged↗
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↗
Exercise electrocardiography of health black children.
Exercise electrocardiography was performed on 170 healthy black children 7 to 14 years of age in order to determine the normal childhood electrocardiographic response to exercise. R-wave amplitude decreased from 27 +/- 8 (SD) to 22 +/- 8 mm (P less than .01) and the S-wave amplitude increased from 6.9 +/- 4.4 to 7.8 +/- 5 mm (P less than .01), indicating a shift of the mean QRS vector to the right at maximum exercise. J-point depression of 1.0 mm or greater was observed in 2.3% of children at maximum exercise, using the PR isoelectric line. ST-segment slope increased from 1.5 +/- 0.7 to 4.3 +/- 1.5 mV/sec at maximum. T-wave duration decreased with exercise and T-wave amplitude initially decreased with mild exercise but exceeded resting values at maximum exercise. No dysrhythmias were observed during or after the exercise study.
Adolescent↗
The significance of fetal electrocardiography in the diagnosis of intrauterine bradyarrhythmia.
From 11 cases of fetal bradycardia diagnosed by monitoring of 130 fetal electrocardiograms (ECG's) in high-risk pregnancies we have presented our experience in three selected cases of fetal bradyarrthythmia. Case 1 revealed on ECG blocked atrial premature beats simulating an extreme sinus bradycardia sequentially followed by conducted atrial premature beats. In case 2 we diagnosed ventricular premature beats in the form of persistent bigeminy which was controlled by intravenous propranolol. The last case illustrated the phenomenon of aberrant ventricular conduction known to occur in adult cardiology. The electrophysiologic basis of the variable arrhythmias was discussed. Detailed analysis of repeated direct fetal ECG's provided us with the diagnosis and understanding of the electrophysiologic mechanisms underlying the rhythm disturbances. This consequently determined the pharmacologic therapy and the obstetric approach relevant to each case. We have shown that by direct fetal electrocardiography it is possible to analyze accurately the rhythm disturbances. Persistent fetal bradycardia does not always signify fetal distress. We hope that this will lead to closer teamwork between the obstetrician and the cardiologist which will give an impetus to the future development of "fetal cardiology," thereby enhancing our understanding of the electrophysiology of the fetal heart.
Adult↗
Quantification of fetal heart rate variability by magnetocardiography and direct electrocardiography.
A computer method for quantification of fetal heart rate (FHR) variability from fetal magnetocardiography during pregnancy and from direct fetal electrocardiography during labor is presented. It is based on statistical analysis of the QRS interval sequences. Beat-to-beat variation is characterized by a differential index (DI) and long-term variation by an interval index (II). The effect of the sample time on the DI is minimal, and hence the DI can be calculated from rather short samples. The II is more sensitive to FHR trends and should be calculated from longer samples, but between the periodic changes, accelerations, and decelerations. Variable amounts of detection pulses are lost in both methods. The DI is sensitive to the missing intervals; no analysis result should be accepted if the number of lost intervals exceeds 10 per cent. The II is less sensitive to the number of missing intervals. The means and standard deviations of the variability indices for eight fetuses during pregnancy and for five fetuses during labor are presented.
Computers↗
His bundle electrocardiography in manifest and concealed right bundle branch extrasystoles.
His bundle electrocardiography was helpful in the diagnosis of impulse formation in the right bundle branch. Ten patients with narrow QRS complexes had ectopic beats with an "incomplete" left bundle branch pattern and almost simultaneous activation of His bundle and ventricles. Both QRS morphology and H- - V intervals depended on the more proximal or distal location of the ectopic focus. In four patients with "complete" right bundle branch block the morphology of ectopic ventricular complexes and H- - V intervals also depeneded on the presence or absence of retrograde block and differential degrees of forward and/or retrograde conduction delays. Nine patients with "complete" right bundle branch block and four with "complete" left bundle branch block had premature beats which could have originated in the proximal right bundle branch, proximal left bundle branch, or distal His bundle. In one patient with "complete" left bundle branch block, "concealed" His bundle depolarizations (probably originating in an ectopic focus located in the right bundle branch) produced pseudo Type II (Mobitz) A-V block. Although lidocaine appeared to have been more effective in patients with bundle branch block than in those with narrow QRS complexes, further studies are necessary to corroborate this impression.
Adult↗
Torso mounted electrocardiographic electrodes for routine clinical electrocardiography.
An easily applicable lead system similar to that proposed by Mason and Likar in 1966 for stress electrocardiography provides quantitative and qualitative electrocardiographic information and diagnoses similar to those derived from the "standard" lead system using only torso placement of ten electrodes.
Arrhythmias, Cardiac↗