Correlation between coronary arteriography and the postexercise electrocardiogram

Diagnostic accuracy of exercise stress testing for coronary artery disease: a systematic review and meta-analysis of prospective studies

BACKGROUND

Exercise stress testing offers a non-invasive, less expensive way of risk stratification prior to coronary angiography, and a negative stress test may actually avoid angiography. However, previous meta-analyses have not included all exercise test modalities, or patients without known Coronary artery disease (CAD).

METHODS AND RESULTS

We systematically reviewed the literature to determine the diagnostic accuracy of exercise stress testing for CAD on angiography. MEDLINE (January 1966 to November 2009), MEDION (1966 to July 2009), CENTRAL (1966 to July 2009) and EMBASE (1980-2009) databases were searched for English language articles on diagnostic accuracy of exercise stress testing. We included prospective studies comparing exercise stress testing with a reference standard of coronary angiography in patients without known CAD. From 6,055 records, we included 34 studies with 3,352 participants. Overall, we found published studies regarding five different exercise testing modalities: treadmill ECG, treadmill echo, bicycle ECG, bicycle echo and myocardial perfusion imaging. The prevalence of CAD ranged from 12% to 83%. Positive and negative likelihood ratios of stress testing increased in low prevalence settings. Treadmill echo testing (LR+ = 7.94) performed better than treadmill ECG testing (LR+ = 3.57) for ruling in CAD and ruling out CAD (echo LR- = 0.19 vs. ECG LR- = 0.38). Bicycle echo testing (LR+ = 11.34) performed better than treadmill echo testing (LR+ = 7.94), which outperformed both treadmill ECG and bicycle ECG. A positive exercise test is more helpful in younger patients (LR+ = 4.74) than in older patients (LR+ = 2.8).

CONCLUSIONS

The diagnostic accuracy of exercise testing varies, depending upon the age, gender and clinical characteristics of the patient, prevalence of CAD and modality of test used. Exercise testing, whether by echocardiography or ECG, is more useful at excluding CAD than confirming it. Clinicians have concentrated on individualising the treatment of CAD, but there is great scope for individualising the diagnosis of CAD using exercise testing.

Importance of the great vessels in the genesis of the electrocardiogram

The electrocardiogram is the graphic representation against time of the difference in potential between points of the body caused by the current field of the heart. To examine the origin of this current field, a method of transforming body surface electrocardiographic data to the epicardial surface has been developed. The computed epicardial current density distributions in 219 patients with acute inferior myocardial infarction showed that, in 89% of patients, the current flow out of the heart during the ST segment came from two regions, not only from the infarction region but also from a region over the great vessels. This findings suggests that current flows from the ischemic region, through the low-resistance pathway provided by the intracavity blood, out the great vessels, and back to the epicardium. A similar pathway has been hypothesized when ischemia caused endocardial ST elevation, such as during a stress test or with unstable angina. To test this hypothesis, a group of patients with ST depression on the 12-lead electrocardiogram, not associated with ST elevation, was examined with body surface mapping. Ninety-four percent of patients had epicardial current density distributions that showed a region of current flow out of the heart and over the great vessels that was consistent with this hypothesis. This could explain the poor localization of coronary artery disease by electrocardiographic techniques when there is ST depression on the body surface.

Exercise-induced ST depression in the diagnosis of coronary artery disease. A meta-analysis

To evaluate the variability in the reported diagnostic accuracy of the exercise electrocardiogram, we applied meta-analysis to 147 consecutively published reports comparing exercise-induced ST depression with coronary angiography. These reports involved 24,074 patients who underwent both tests. Population characteristics and technical and methodologic factors, including publication year, number of electrocardiographic leads, exercise protocol, use of hyperventilation, definition of an abnormal ST response, exclusion of certain subgroups, and blinding of test interpretation were analyzed. Wide variability in sensitivity and specificity was found (mean sensitivity, 68%; range, 23-100%; SD, 16%; and mean specificity, 77%; range, 17-100%; SD, 17%). The four study characteristics found to be significantly and independently related to sensitivity were the treatment of equivocal test results, comparison with a "better" test such as thallium scintigraphy, exclusion of patients on digitalis, and publication year. The four variables found to be significantly and independently related to specificity were the treatment of upsloping ST depressions, the exclusion of subjects with prior infarction or left bundle branch block, and the use of preexercise hyperventilation. Stepwise linear regression explained less than 35% of the variance in sensitivities and specificities reported in the 147 publications. There is wide variability in the reported accuracy of the exercise electrocardiogram. This variability is not explained by information reported in the medical literature.

The effect of validation group bias on screening tests for coronary artery disease

The exercise electrocardiogram (ECG) is frequently used as a screening tool for coronary artery disease (CAD) in epidemiological studies and routine health evaluation. Estimates of the validity of this diagnostic test have usually been obtained by correlating the exercise ECG with the results of coronary angiography. However, coronary angiography is usually performed only on selected individuals with symptomatic CAD. If symptomatic subjects are more likely to respond positively to the exercise ECG than asymptomatic individuals with comparable severity of disease, then biased estimates of the test validity for an unselected population may be obtained. In this paper the validation group bias is shown to be a function both of the proportion of the population with symptomatic CAD and of the relative validity of the test for the symptomatic and asymptomatic subjects. The extent of this bias is examined.

Methodologic problems of exercise testing for coronary artery disease: groups, analysis and bias

To determine why exercise testing remains controversial as a diagnostic test for coronary artery disease, a methodologic review was undertaken of 33 studies comprising 7,501 patients who had undergone both exercise tests and coronary angiography. Of seven methodologic standards for research design, only one received general compliance: the requirement for an adequate variety of anatomic lesions. Less than half of the studies complied with any of the remaining six standards: adequate identification of the groups selected for study; adequate analysis for relevant chest pain syndromes; avoidance of a limited challenge group; and avoidance of work-up bias, diagnostic review bias and test review bias. Only one study met as many as five standards. These methodologic problems may explain the wide range of sensitivity (35 to 88 percent) and specificity (41 to 100 percent) found for exercise testing, because the variations could not be attributed to the usual explanations: definition of anatomic abnormality, stress test technique or definition of an abnormal test. Determining the true value of exercise testing requires methodologic improvements in patient selection, data collection and data analysis.

Relation between the precordial projection of S-T segment changes after exercise and coronary angiographic findings

The recent introduction of electrocardiographic mapping permits measurement of the precordial area and severity of exercise-induced S-T segment changes. This study was designed to compare this technique with a modified 12 lead electrocardiogram in defining the degree and site of coronary artery disease. One hundred patients, who later had diagnostic coronary arteriography, underwent an exercise test using both 16 point precordial mapping and a modified 12 lead electrocardiogram. The sensitivity of electrocardiographic mapping (96 percent) for the diagnosis of coronary artery disease was significantly greater than that of the modified 12 lead electrocardiogram (80 percent). However, the specificity of the two lead systems was similar. Typical precordial projections of S-T segment change were found when the left main stem or proximal left anterior descending coronary artery were narrowed or when there was isolated disease of the left anterior descending or right coronary artery. Widespread precordial changes were found in patients with three vessel disease. Although there was no significant difference in the sensitivity (66 percent) and specificity (100 percent) of electrocardiographic mapping and of the 12 lead system in identifying three vessel disease, there was a significant difference in sensitivity (electrocardiographic mapping 74 percent, 12 lead system 42 percent) in identifying isolated single vessel disease. In addition, information regarding the presence of left main stem or proximal left anterior descending coronary arterial narrowing was obtained only with electrocardiographic mapping. The superiority of electrocardiographic mapping over the modified 12 lead electrocardiogram has been shown, and clinical application of this technique should be useful in the management of patients presenting with chest pain.

Value of treadmill exercise testing in patients with complete bundle branch block

Exercise electrocardiography and selective coronary arteriography was performed in 24 consecutive patients with complete bundle branch block. The criteria for a positive exercise electrocardiogram (E-ECG) were a 1 mm depression or elevation in the J point from the control state, as well as in the ST-segment measured at 0.04 seconds from the J point. Eleven of 12 patients with complete left bundle branch block had a positive E-ECG. Nine of them had normal coronary arteriograms, except one with less than 50% lesions in two arteries. Two patients had severe three-vessel disease. Only one patient had a true negative exercise test. No patient had a false negative test. Nine of 12 patients with complete right bundle branch block had a positive E-ECG. One of these 9 had minimal nonobstructive disease, while the other 8 had severe two- or three-vessel coronary artery disease. Three of the 12 right bundle branch block patients had a negative E-ECG. Two of them had a true negative exercise test, and one a false negative test. Because of a high incidence of probably false positive results, E-ECG appears to be unreliable in detecting coronary artery disease in patients with complete left bundle branch block. But it can provide useful information in the noninvasive evaluation of coronary artery disease in patients with complete right bundle branch block.

Automatic data processing in the cardiac catheterization laboratory

A review of automatic data processing in the cardiac catherization lab is presented. The emphasis placed on on-line manometry, indicator dilution and off-line quantitative ventriculography. The system organization is described and several specific examples given to illustrate the level of detail necessary to specify such a system. The clinical use of the system is described together with an evaluation of the original design goals in terms of the actual performance of the system. A few unexpected benefits have emerged with respect to quality control and reliability, but one of the original design goals, speeding up the catheterization procedure, has proven to be unrealistic. The next logical steps in the software and hardware evolution are described with the emphasis placed on making the system a more effective tool for the clinician.

Submaximal treadmill exercise testing of patients with coronary artery disease

The submaximal treadmill exercise test is a valuable noninvasive tool for the diagnosis of overt or latent coronary artery disease (CAD). When submaximal heart rates of 80% to 90% of the predicted maximal rates are attained and when ST-segment depression of at least 1 mm is taken as a criterion of ischemia, testing by any of the various exercise protocols with continuous ECG monitoring affords reasonable specificity and sensitivity. The objectives of testing are to (1) diagnose and determine the severity of CAD, (2) assess functional capacity, (3) observe the natural history of disease, (4) evaluate the effects of medical and surgical treatment, and (5) evaluate responses to physical conditioning or to programs directed toward prevention of CAD. Proper precautions and safety standards minimize the risk of exercise testing.

Comparison between regional myocardial blood flow measurements and results of exercise tests

The relationship between regional myocardial blood flow and the results of exercise tests were evaluated in 54 patients, 40 of whom had angiographically demonstrated coronary artery disease (CAD) and 14 had normal angiograms. After 20 patients had 2-step tests, 20 had bicycle ergometry, and 14 had treadmill tests, regional myocardial specific blood flow (RMBF) at rest was determined by selective injections of xenon-133 into the left coronary artery and quadrantic washout measured with an Anger camera. RMBF (ml/min/100 gm, mean +/- SE) was significantly lower in patients with coronary artery disease (72 +/- 3) than in normals (91 +/- 7, p less than .05) but RMBF in 12 CAD patients with negative exercise tests (75 +/- 6) was similar to regional myocardial blood flow in 28 coronary artery disease patients with positive exercise tests (71 +/- 4). Degree of ST depression did not influence results. Although measurement of RMBF and exercise testing are both useful procedures in the evaluation of patients with CAD, the data in the present study indicate the RMBF measurements at rest cannot predict the result of the postexercise ECG and vice versa.

Reappraisal of the functional significance of the coronary collateral circulation

A review of data in 465 patients with complete obstruction of either the left anterior descending or right coronary artery was undertaken to evaluate the functional role of the collateral circulation. Complete obstruction of a dominant right coronary artery was observed in 288 patients, 83 percent with distal filling and visualization of the posterior descending artery by way of collateral vessels. Complete obstruction of the left anterior descending artery was noted in 177 patients, 71 percent with filling and visualization distal to the obstruction by way of collateral vessels. Among patients with obstruction of the left anterior descending artery, there was a significantly greater frequency of congestive heart failure and cardiomegaly in those without collateral vessels than in those with collateral vessels. The former also had a significantly greater frequency of both electrocardiographic evidence of an anterior wall myocardial infarction and angiographic findings of anterior wall asynergy. The frequency of inferior myocardial infarction and inferior wall asynergy was not influenced by the presence of collateral vessels. These observations indicate that the collateral circulation plays a significant protective role in the presence of obstruction of the left anterior descending artery, which is not apparent with obstruction of the right coronary artery.

Hemodynamic changes associated with angina pectoris induced by maximal treadmill exercise: effect of sublingual isosorbide dinitrate on systolic time intervals

A technique for the study of patients with angina pectoris has been described, in which systolic time interval (STI) measurements are obtained at intervals after the onset of stress-induced angina. The technique is uniquely suited to the evaluation of anti-anginal drugs. Sublingual isosorbide dinitrate (SISD) was randomly alternated with a placebo (P) tablet in a double-blind study of 20 patients with stable angina pectoris. After SISD, compared to placebo, a highly significant shortening of Q-S2 and LVET occurred (p less than 0.001) which lasted throughout the entire 120 minute study period. The hemodynamic basis for these differences was felt to be improved myocardial contractility secondary to a reduction in systemic vascular resistance and reduced venous return induced by the SISD. A significant prolongation of PEP occurred at 60 minutes post-SISD (p less than 0.01). This was attributed to an increase in the gradient between LVEDP and aortic diastolic pressure resulting from reduced venous return after SISD. The PEP/LVET ratio was significantly increased up to 60 minutes after SISD (P less than 0.05). Heart rate was uniformly higher post-SISD, compared to post-placebo values; the differences were highly significant up to 60 minutes (P less than 0.001) and remained significant at 120 minutes (p less than 0.05). The time to angina was significantly longer (immediately post SISD, p less than 0.05; 30 min, p less than 0.001; 60 mins, p less than 0.05; 120 mins, p less than 0.05); and the work load greater, for 120 minutes following SISD: the increase in the latter was highly significant for 30 minutes after SISD (p less than 0.001) and remained significant up to 120 minutes (60 mins, p less than 0.05; 120 mins, p less than 0.05). These observations were attributed to an improvement in myocardial function due to the sublingual isosorbide dinitrate. A high degree of correlation was found to exist between heart rate and the STI. This correlation was negative for the QS2 interval (-0.996) and LVET (-0.993) and positive for PEP (+0.817) and the PEP/LVET ratio (+0.950).

ST-segment isolation and quantification as a means of improving diagnostic accuracy in treadmill stress testing

A new method of ST-segment analysis utilizing computer-analytic techniques has been employed in treadmill exercise testing, with the aim of enhancing diagnostic sensitivity and specificity. One hundred thirty-three individuals were studied, including 62 normal subjects (Group I), 29 patients with coronary disease and clear, "ischemic" ST-segment responses to exercise testing (Group II), and 42 patients with coronary disease but normal or nondiagnostic exercise tests (Group III). The techniques used included: computer averaging, to minimize motion artifact and baseline drift; a means of isolating the ST-segment from the T-wave and quantifying ST-amplitude and slope (the isolated ST integral, IST); and the relating of the IST to a given heart rate, thus taking cognizance of the dependency of ST-depression on heart rate and level of exercise. These methods resulted in a test specificity exceeding 90 per cent and a sensitivity of over 85 per cent. Further evidence of the improved sensitivity achieved using these techniques included a 79 per cent (33 of 42) recognition of abnormalities in Group III, patients having normal or nondiagnostic visually interpreted treadmill stress tests (i.e., no flat or downsloping ST-segments of 1 mm. or greater). Moreover, 15 of 29 patients in Group II (52 per cent) manifested abnormal IST's before development of a typical "ischemic" ST, and in 17 patients (59 per cent), the IST continued to remain positive after disappearance of the characteristic flat or downsloping ST-segment. It is concluded that this type of computation analysis adds appreciable diagnostic sensitivity and specificity to treadmill stress testing.

Significant sex differences in the correlation of electrocardiographic exercise testing and coronary arteriograms

Two hundred fifty-one patients (195 male and 56 females) referred for evaluation of chest pain were studied by multistage submaximal stress testing and selective coronary arteriography. In men with positive exercise tests the incidence rate of true positive exercise test results--that is, positive tests associated with 75 percent of greater coronary stenosis--was 89 percent in contrast to a 33 percent incidence rate of true positive exercise test results in women. The incidence rate of false positive excercise test results--that is, positive tests associated with no coronary stenosis or less than 50 percent stenosis--was 8 percent in men in contrast to 67 percent in women. Conversely, the incidence rate of false negative exercise test results (that is, negative exercise tests associated with 75 percent or greater coronary stenosis) was higher in men (37 percent) than in women (12 percent). It is concluded that in men a positive multistage stress test is useful in predicting the presence of significant coronary artery disease although a negative stress test cannot be relied upon to rule out the presence of significant disease. In women, a positive exercise test is of little value in predicting the presence of significant coronary artery disease, whereas a negative test is quite useful in ruling out the presence of significant disease. New criteria should be developed for stress testing of women.

Maximum treadmill exercise test in patients with abnormal control electrocardiograms

To determine the validity and safety of exercise induced ST changes (1 mm ischemic depression or further depression in ECG lead V 5 ) as an indication of coronary artery disease (CAD) in patients with abnormal control electrocardiograms (ECG), 121 such patients were compared to 57 patients with a normal control ECG. All underwent a maximum graded treadmill exercise test and coronary arteriography. Among those patients with normal control ECGs, there were no false positives and five false negatives (sensitivity-85%, specificity-100%). In 61 patients with abnormal ECG (no drug therapy except nitrates) there were four false positives and nine false negatives (sensitivity-76%, specificity-79%). In this group of patients T waves reverted from negative to positive in four patients with CAD and 10 patients with no CAD, but T inversion during exercise only occurred in those with CAD (6 patients). Three of 12 patients (25%) with ECG evidence of old infarction and four of eight with single vessel disease had false negative tests. In 60 patients with abnormal ECG on drug therapy there were 10 false positives (17%) and 15 false negatives (sensitivity-55%, specificity-63%). Not helpful in differentiation were resting T vs ST changes, induction of arrhythmias or exercise induced chest pain.

The validity of exercise induced ST changes in differentiating CAD is excellent when the control ECG is normal and is only slightly reduced with control ST-T wave abnormalities. When the latter occur in association with cardiovascular drug therapy, other than nitrates, the exercise ECG is of no use in differential diagnosis although still valid and safe for the determination of exercise tolerance.

Potassium-43 myocardial perfusion scanning for the noninvasive evaluation of patients with false-positive exercise tests

Twelve patients with false-positive ECG exercise tests presented with ischemic ECG responses (greater than one mm ST segment depression) during graded maximal treadmill exercise testing in the absence of exercise-induced chest pain or clinical coronary heart disease. Coronary arteriography, left ventriculography and hemodynamic evaluation revealed no significant abnormality in these patients. Transmyocardial lactate analysis during atrial pacing revealed a normal extraction (mean 21%) during pacing stress in five patients.

Nine of 12 patients were evaluated with exercise potassium-43 myocardial perfusion imaging whereby the radioactive tracer was administered intravenously during exercise at a time when abnormal ECG changes were present. Myocardial images in these nine patients all showed a normal homogeneous pattern of radioisotope distribution. These results are in direct contrast to findings in patients with coronary heart disease in whom reproducibly demonstrable abnormal regions of decreased potassium-43 accumulation have been noted in myocardial images obtained following injection of the radioactive tracer during exercise. Potassium-43 exercise myocardial perfusion scanning thus appears to be an accurate noninvasive method of assessing patients with suspected false-positive exercise tests and provides a means of increasing the specificity of exercise testing.

Inability of the submaximal treadmill stress test to predict the location of coronary disease

Two hundred patients had submaximal treadmill stress tests (STSTs) and selective coronary arteriography performed within 2 months of each other. An attempt was made to assess the predictability of disease isolated to any given coronary vessel by performance on the treadmill. This was not possible for disease isolated to the right coronary, the left anterior descending, the circumflex branch of the left coronary, or a combination of right coronary and circumflex arteries. Eleven patients had disease in the left main coronary artery; all had associated disease of some other branch as well. One of these patients had a negative submaximal treadmill stress test but was unable to reach 90% of his maximum predicted heart rate. The remaining 10 patients had positive STSTs. Patients with 26-50% narrowing of any branch had treadmill results similar to those with 51-75% narrowing. There was a large number of patients with single-vessel disease in the study and most of the negative STSTs occurred in this group. Nevertheless, within this group no one vessel gave a higher incidence of positive STSTs than any other. It is concluded that (1) a positive STST is more likely to be associated with increased severity and extent of coronary artery disease; (2) a negative STST is more likely to be found in disease limited to a single vessel; and (3) within the latter group, the STST is of no value in predicting the specific coronary artery involved.

Uses and limitations of stress testing in the evaluation of ischemic heart disease

The results of stress testing in patients being assessed for coronary artery disease have led to conflicting claims and conclusions. It seems reasonably clear that stress testing is of considerable predictive value in epidemiologic studies; i.e., patients manifesting or developing a positive exercise test have a much higher probability of subsequently experiencing coronary events (angina pectoris, myocardial infarction, or coronary death) than those individuals with normal stress tests. Moreover, the risk seems to be related to the degree of S-T segment depression. In contrast, despite earlier claims regarding the diagnostic accuracy with which single-load stress tests could predict the presence or absence of ischemic heart disease in individual patients, studies correlating the results of testing with the degree and extent of angiographically demonstrated coronary artery disease have not consistently shown either acceptable sensitivity or specificity. Although on theoretic grounds it would be anticipated that multistage stress tests would be superior to single-stage protocols, this has not been borne out in the few published studies in which the results are correlated with angiography. Thus, the available evidence suggests that there remain appreciable numbers of patients with documented coronary artery disease in whom no ECG abnormalities are detected despite relatively intense levels of exercise, and an appreciable number of patients with abnormal ECG responses but normal coronary arteries. Stresses other than exercise have been and are being utilized in the evaluation of patients with chest pain; however, no single test as yet offers the desired specificity and sensitivity.

We conclude that, in patients with typical angina pectoris or with chest pain which clearly does not resemble angina pectoris, stress testing appears to be superfluous since it provides little additional information beyond that which may be obtained from the patient's history. It is in those patients presenting with atypical anginal syndromes that a reliable noninvasive test would be of great value. Currently available technics are neither sufficiently sensitive nor specific to satisfactorily aid in solving this problem.

Correlation of electrocardiographic studies and arteriographic findings with angina pectoris

The relationships among angina pectoris, stress tests, and arteriography are complex. The majority of patients with angina pectoris can be adequately diagnosed by a careful history. Considerable attention to detail and repeated questioning is often necessary before the pain syndrome can be accurately classified. The resting electrocardiogram is of limited value in the diagnosis despite the fact that there is a high positive correlation between abnormal ST-T changes on the electrogram and significant obstructive lesions on coronary arteriograms. The value of the electrocardiogram is enhanced, and its specifiicity and sensitivity increased, when used in combination with exercise stress. The lowest error percentage is achieved by utilizing rate-standardized exercise tests and multiple leads with loads that produce heart rate responses of 80-90% of the expected maximum. Coronary arteriography gives the most specific anatomic information in patients with ischemic cardiac pain but will not directly disclose the cause of the pain. This fact assumes considerable importance when the pain has atypical features or when the patient is in the age group that has a high prevalence of coronary atherosclerosis. Similarly, the presence of past myocardial infarction is likely to be associated with obstructive disease, regardless of the cause of the patient's current symptoms. The exact role of lipid and other metabolic abnormalities in producing coronary arteriographic changes in the absence of symptoms needs further clarification, although the available data suggest that marked elevations in lipid fractions are frequently associated with atherosclerotic change, regardless of symptoms. Finally, the data imply that the anatomic abnormalities and functional consequences of the coronary atherosclerotic process are more important predictors of the patient's course than any specific symptomatic expression such as angina pectoris.

Use of exercise testing for diagnostic and functional evaluation of patients with arteriosclerotic heart disease

Myocardial oxygen demand generally increases with increasing levels of energy expenditure, but several factors which modify this relation must be considered, both in the design of the test methods and in interpretation of results of exercise tests in patients with arteriosclerotic heart disease (ASHD).

A wide variety of exercise test methods are currently used. Master's test is simple to perform and requires no elaborate equipment. It has been more widely employed than any other test and much clinicopathologic and correlative data are available. However, Master's test provides little information on the patient's physical work capacity. Multistage tests, carried to a symptom-limited or maximal/near-maximal workload level, provide quantitative data on physical performance capacity and also result in fewer false-negative ECG responses among patients with ASHD.

Follow-up studies of asymptomatic subjects have demonstrated that a horizontal S-T depression during or after exercise is associated with a high risk of developing clinical ASHD. The prognostic significance of the exercise test appears to be independent of other known risk factors.

Studies correlating the ECG response to exercise with findings at coronary angiography have demonstrated an abnormal ECG response in 0-30% of patients with no demonstrable arterial disease. The number of patients with significant coronary artery disease and negative ECG response tends to be higher.

Evaluation of physical performance capacity is the primary indication for exercise testing in patients with known ASHD. The results of the test form a basis for recommendations on occupational and recreational physical activity. Serial tests may be used to evaluate objectively the effect of medical and surgical therapy.

Vectorcardiographic T loop analysis in ischaemic heart disease

Images

Postexercise electrocardiogram in patients with abnormal resting electrocardiograms

One hundred and ten patients with chest pain syndromes and resting electrocardiograms demonstrating ST-T abnormalities and/or prior transmural myocardial infarctions were studied by means of the Master's two-step exercise test and selective coronary cine arteriography. Criteria for negativity were modified so that subjects with postexercise heart rates less than 110 beats/min, who did not develop significant ST-segment changes, were excluded from evaluation. Eighty-six per cent of the coronary artery disease group and 27% of the normal coronary artery group had positive postexercise electrocardiograms. Conversely, of the patients with positive results, 88% had anatomic coronary artery disease. With this degree of stress, positive responses ≧2 mm were invariably associated with multi-vessel disease. The type of pre-existing ECG abnormality did not influence either the frequency or severity of positive responses. False-negative subjects had no distinctive features relating to type of abnormal electrocardiogram, or location of vessel involvement, although most of these patients had significant disease of only one major coronary artery.