Comparison of a quantitative treadmill exercise score with standard electrocardiographic criteria in screening asymptomatic young men for coronary artery disease

Screening for Cardiovascular Disease Risk With Resting or Exercise Electrocardiography: Evidence Report and Systematic Review for the US Preventive Services Task Force

IMPORTANCE

Cardiovascular disease (CVD) is the leading cause of death in the United States.

OBJECTIVE

To review the evidence on screening asymptomatic adults for CVD risk using electrocardiography (ECG) to inform the US Preventive Services Task Force.

DATA SOURCES

MEDLINE, Cochrane Library, and trial registries through May 2017; references; experts; literature surveillance through April 4, 2018.

STUDY SELECTION

English-language randomized clinical trials (RCTs); prospective cohort studies reporting reclassification, calibration, or discrimination that compared risk assessment using ECG plus traditional risk factors vs traditional risk factors alone. For harms, additional study designs were eligible. Studies of persons with symptoms or a CVD diagnosis were excluded.

DATA EXTRACTION AND SYNTHESIS

Dual review of abstracts, full-text articles, and study quality; qualitative synthesis of findings.

MAIN OUTCOMES AND MEASURES

Mortality, cardiovascular events, reclassification, calibration, discrimination, and harms.

RESULTS

Sixteen studies were included (N = 77 140). Two RCTs (n = 1151) found no significant improvement for screening with exercise ECG (vs no screening) in adults aged 50 to 75 years with diabetes for the primary cardiovascular composite outcomes (hazard ratios, 1.00 [95% CI, 0.59-1.71] and 0.85 [95% CI, 0.39-1.84] for each study). No RCTs evaluated screening with resting ECG. Evidence from 5 cohort studies (n = 9582) showed that adding exercise ECG to traditional risk factors such as age, sex, current smoking, diabetes, total cholesterol level, and high-density lipoprotein cholesterol level produced small improvements in discrimination (absolute improvements in area under the curve [AUC] or C statistics, 0.02-0.03, reported by 3 studies); whether calibration or appropriate risk classification improves is uncertain. Evidence from 9 cohort studies (n = 66 407) showed that adding resting ECG to traditional risk factors produced small improvements in discrimination (absolute improvement in AUC or C statistics, 0.001-0.05) and appropriate risk classification for prediction of multiple cardiovascular outcomes, although evidence was limited by imprecision, quality, considerable heterogeneity, and inconsistent use of risk thresholds used for clinical decision making. Total net reclassification improvements ranged from 3.6% (2.7% event; 0.6% nonevent) to 30% (17% event; 19% nonevent) for studies using the Framingham Risk Score or Pooled Cohort Equations base models. Evidence on potential harms (eg, from subsequent angiography or revascularization) in asymptomatic persons was limited.

CONCLUSIONS AND RELEVANCE

RCTs of screening with exercise ECG found no improvement in health outcomes, despite focusing on higher-risk populations with diabetes. The addition of resting ECG to traditional risk factors accurately reclassified persons, but evidence for this finding had many limitations. The frequency of harms from screening is uncertain.

Athens QRS Score as a Predictor of Coronary Artery Disease in Patients With Chest Pain and Normal Exercise Stress Test

Background

The diagnostic value of the Athens QRS score to detect obstructive coronary artery disease CAD in patients with otherwise normal exercise stress test remains unclear.

Methods and Results

We analyzed 458 patients who underwent exercise stress test with or without myocardial perfusion imaging within 2 months of coronary angiography from 2008 to 2011. Patients (n=173) with abnormal stress test based on ST segment criteria were excluded. The Athens QRS score ≤5 was defined as abnormal. In our study cohort, 285 patients met the inclusion criteria and were divided into 2 groups: low Athens QRS score (LQRS, n=56), with QRS score ≤5 and normal Athens QRS score normal Athens QRS score, n=229), with QRS score >5. The presence of single‐vessel and multivessel obstructive CAD was higher in LQRS than in normal Athens QRS score patients (47% versus 7.5% and 30% versus 3.8%, respectively, all P<0.001). Logistic regression analysis showed that the likelihood of CAD was strongly and independently associated with LQRS (odds ratio=36.81, 95% CI: 10.77–120.47), diabetes (odds ratio=6.49, 95% CI: 2.41–17.49), lower maximum heart rate (odds ratio=0.92, 95% CI: 0.88–0.95, all P<0.001), and older age (odds ratio=1.93, CI: 1.88–1.97, P=0.002).

Conclusions

In a clinical cohort of patients with chest pain and normal exercise stress test, LQRS score is a strong independent predictor of presence of CAD. LQRS patients have a 6‐fold higher prevalence of CAD and may warrant further evaluation even with reassuring exercise stress test.

Cardiac screening with electrocardiography, stress echocardiography, or myocardial perfusion imaging: advice for high-value care from the American College of Physicians

BACKGROUND

Cardiac screening in adults with resting or stress electrocardiography, stress echocardiography, or myocardial perfusion imaging can reveal findings associated with increased risk for coronary heart disease events, but inappropriate cardiac testing of low-risk adults has been identified as an important area of overuse by several professional societies.

METHODS

Narrative review based on published systematic reviews; guidelines; and articles on the yield, benefits, and harms of cardiac screening in low-risk adults.

RESULTS

Cardiac screening has not been shown to improve patient outcomes. It is also associated with potential harms due to false-positive results because they can lead to subsequent, potentially unnecessary tests and procedures. Cardiac screening is likely to be particularly inefficient in adults at low risk for coronary heart disease given the low prevalence and predictive values of testing in this population and the low likelihood that positive findings will affect treatment decisions. In this patient population, clinicians should focus on strategies for mitigating cardiovascular risk by treating modifiable risk factors (such as smoking, diabetes, hypertension, hyperlipidemia, and overweight) and encouraging healthy levels of exercise.

HIGH-VALUE CARE ADVICE

Clinicians should not screen for cardiac disease in asymptomatic, low-risk adults with resting or stress electrocardiography, stress echocardiography, or stress myocardial perfusion imaging.

A risk score for predicting coronary artery disease in women with angina pectoris and abnormal stress test finding

Women with angina pectoris and abnormal stress test findings commonly have no epicardial coronary artery disease (CAD) at catheterization. The aim of the present study was to develop a risk score to predict obstructive CAD in such patients. Data were analyzed from 337 consecutive women with angina pectoris and abnormal stress test findings who underwent cardiac catheterization at our center from 2003 to 2007. Forward selection multivariate logistic regression analysis was used to identify the independent predictors of CAD, defined by ≥50% diameter stenosis in ≥1 epicardial coronary artery. The independent predictors included age ≥55 years (odds ratio 2.3, 95% confidence interval 1.3 to 4.0), body mass index <30 kg/m(2) (odds ratio 1.9, 95% confidence interval 1.1 to 3.1), smoking (odds ratio 2.6, 95% confidence interval 1.4 to 4.8), low high-density lipoprotein cholesterol (odds ratio 2.9, 95% confidence interval 1.5 to 5.5), family history of premature CAD (odds ratio 2.4, 95% confidence interval 1.0 to 5.7), lateral abnormality on stress imaging (odds ratio 2.8, 95% confidence interval 1.5 to 5.5), and exercise capacity <5 metabolic equivalents (odds ratio 2.4, 95% confidence interval 1.1 to 5.6). Assigning each variable 1 point summed to constitute a risk score, a graded association between the score and prevalent CAD (ptrend <0.001). The risk score demonstrated good discrimination with a cross-validated c-statistic of 0.745 (95% confidence interval 0.70 to 0.79), and an optimized cutpoint of a score of ≤2 included 62% of the subjects and had a negative predictive value of 80%. In conclusion, a simple clinical risk score of 7 characteristics can help differentiate those more or less likely to have CAD among women with angina pectoris and abnormal stress test findings. This tool, if validated, could help to guide testing strategies in women with angina pectoris.

A comparison of treadmill scores to diagnose coronary artery disease

BACKGROUND

Recently, several treadmill scores have been proposed as means for improving the diagnostic accuracy of the exercise treadmill test (ETT). Questions remain regarding the diagnostic accuracy of treadmill scores when applied to a different patient population than that from which they were derived; furthermore, many treadmill scores have not been compared with one another in the same population.

HYPOTHESIS

The diagnostic accuracy of treadmill scores may not be the same.

METHODS

A retrospective analysis of data collected prospectively was performed on consecutive patients referred for evaluation of chest pain. All patients underwent a standard ETT followed by coronary angiography. Using angiographic evidence of coronary artery disease (CAD) as a reference, the area under the curve (AUC) of receiver operator characteristic (ROC) plots of the ST response alone, the Duke Treadmill Score (DTS), the Morise score, the Detrano score, the VA score, and a Consensus score consisting of the Morise, Detrano, and VA scores together were calculated and compared. The predictive accuracies of the DTS and the Consensus score to stratify patients for the likelihood of CAD were calculated and compared.

RESULTS

In all, 1,282 patients without a prior myocardial infarction had an ETT and coronary angiography. The AUC (+/- standard error) was 0.67+/-0.01 for the ST response, 0.73+/-0.01 for DTS, 0.76+/-0.01 for Detrano score, 0.77+/-0.01 for Morise score, 0.78+/-0.01 for VA score, and 0.78+/-0.01 for Consensus score. The AUC for each treadmill score was significantly higher (z-score > 1.96) than for the ST response alone. The AUC of DTS was significantly lower than all other treadmill scores (z-score > 1.96). The predictive accuracy (+/-95% confidence interval) of the DTS to risk stratify patients into high and low likelihood for CAD was 71 (65-77)%, versus 80 (74-86)% for the Consensus score (p < 0.0001).

CONCLUSION

In this population, the DTS remains useful for diagnosing CAD and stratifying for the likelihood of CAD, although it is less accurate than other treadmill scores.

Exercise capacity and the risk of death in women: the St James Women Take Heart Project

BACKGROUND

Cardiovascular disease is the leading cause of death among women and accounts for more than half of their deaths. Women have been underrepresented in most studies of cardiovascular disease. Reduced physical fitness has been shown to increase the risk of death in men. Exercise capacity measured by exercise stress test is an objective measure of physical fitness. The hypothesis that reduced exercise capacity is associated with an increased risk of death was investigated in a cohort of 5721 asymptomatic women who underwent baseline examinations in 1992.

METHODS AND RESULTS

Information collected at baseline included medical and family history, demographic characteristics, physical examination, and symptom-limited stress ECG, using the Bruce protocol. Exercise capacity was measured in metabolic equivalents (MET). Nonfasting blood was analyzed at baseline. A National Death Index search was performed to identify all-cause death and date of death up to the end of 2000. The mean age of participants at baseline was 52+/-11 years. Framingham Risk Score-adjusted hazards ratios (with 95% CI) of death associated with MET levels of <5, 5 to 8, and >8 were 3.1 (2.0 to 4.7), 1.9 (1.3 to 2.9), and 1.00, respectively. The Framingham Risk Score-adjusted mortality risk decreased by 17% for every 1-MET increase.

CONCLUSIONS

This is the largest cohort of asymptomatic women studied in this context over the longest period of follow-up. This study confirms that exercise capacity is an independent predictor of death in asymptomatic women, greater than what has been previously established among men. The implications for clinical practice and health care policy are far reaching.

QRS Score: a composite index of exercise-induced changes in the Q, R, and S waves during exercise stress testing in patients with ischemic heart disease

BACKGROUND

To detect ischemic heart disease, the exercise-induced ST-segment displacement is the most frequently used ECG parameter. However, the value of this marker was proven to be limited with varying sensitivity and specificity. A new parameter, called QRS score, emerged to improve the efficacy of exercise testing.

METHODS

Our study aimed at evaluating the diagnostic value of QRS score in ischemic heart disease, investigating males and females separately, and examining the effects of heart rate and antiischemic medication. QRS score and cumulative ST depression were calculated in 212 patients and correlated to the findings of the stress myocardial perfusion SPECT (197 subjects) or coronary angiography (54 subjects).

RESULTS

An inverse correlation could be found between the QRS score and the results of myocardial SPECT and coronary angiography in the whole population, especially in males; females did not show a significant relationship. In patients with conclusive tests (achieving 85% of the maximal predicted heart rate) QRS score correlated significantly with the results of the stress myocardial perfusion SPECT and coronary angiography. The sensitivity, specificity, and validity of the QRS score surpassed those of the cumulative ST depression in the entire population as well as in patients with conclusive tests. The antiischemic medication did not affect correlation values.

CONCLUSION

QRS score was significantly related to the extent of myocardial ischemia and the severity of coronary heart disease, thus along with the analysis of ST-segment displacement may contribute to the more precise evaluation of exercise testing.

Computer applications in the interpretation of the exercise electrocardiogram

The exercise electrocardiogram remains the noninvasive diagnostic test of first choice in patients with coronary artery disease. While new technology offers novel diagnostic possibilities and the ability to assess patients unsuitable for exercise testing, no other investigation has to this point furnished the quality of functional information and value-for-predictive accuracy of exercise electrocardiography. In this article, we describe how this central position in the work up of the cardiac patient has been secured through the evolution of the microprocessor. Particularly important has been its ability to harness and present large volumes of raw data, to derive and manipulate multivariate equations for diagnostic prediction, and to run 'expert' systems which can pool demographic and exercise test data, calculate risk scores, and prompt the nonexpert with advice on current management. These key features explain the pivotal role of the exercise test in the diagnostic, and increasingly prognostic, armoury of the cardiovascular clinician.

Heart rate adjustment of ST segment depression and performance of the exercise electrocardiogram: a critical evaluation

Analysis of the rate-related change in exercise-induced ST segment depression using the exercise ST segment/heart rate slope and ST segment/heart rate index can improve the accuracy of the exercise electrocardiogram (ECG) for the identification of patients with coronary artery disease, recognition of patients with anatomically or functionally severe coronary obstruction and detection of patients at increased risk for future coronary events. These methods provide a more physiologic approach to analysis of the ST segment response to exercise by adjusting the apparent severity of ischemia for the corresponding increase in myocardial oxygen demand, which in turn can be linearly related to increasing heart rate. Solid-angle theory provides a model for the linear relation of ST segment depression to heart rate during exercise and a framework for understanding the relation of the ST segment/heart rate slope to the presence and extent of coronary artery disease. False positive and false negative test results of the heart rate-adjusted methods are well known in selected populations and require further clarification. Application of these methods is also highly dependent on the type of exercise protocol, number of ECG leads examined, timing of ST segment measurement relative to the J point and accuracy and precision of ST segment measurement. These methodologic details have been an important limitation to test application when traditional protocols and measurement procedures are required. When applied with attention to required details, the heart rate-adjusted methods can improve the usefulness of the exercise ECG in a range of clinically relevant populations.

Abnormal exercise electrocardiogram in an asymptomatic person--what next?

No reasonable guidelines exist for evaluating an asymptomatic individual (without evidence for ischemic heart disease on history or electrocardiography) with a positive exercise ECG. Available data indicate that persons with a strongly positive test should undergo a coronary angiography. In persons with mild to moderately positive results, cinefluoroscopy is indicated and those who show coronary calcification should have a coronary angiogram. Although stress thallium-201 is often done before coronary angiography, its role is limited. Scant data exist in women and suggest that the overall approach may not be markedly different. However, ST changes in women have a low specificity. Recent studies indicate a 95% specificity and sensitivity for positron emission tomography. Despite its high costs it may still be the most cost-effective modality by saving unwanted radionuclide studies and arteriographies.

Improved exercise test accuracy using discriminant function analysis and "recovery ST slope"

The objective of the study was to optimize the accuracy of the exercise test for predicting the presence of significant angiographic coronary artery disease. A retrospective analysis of stored digital exercise electrocardiographic data on 147 men who had undergone exercise testing and cardiac catheterization was performed. With significant coronary artery disease defined as > or = 70% stenosis, 95 patients had one or more vessel(s) diseased. None were receiving digoxin, had a myocardial infarction or previous coronary artery bypass graft, or exhibited left bundle branch block, left ventricular hypertrophy, Q waves, or ST depression on their resting electrocardiogram. Analysis was performed using the authors' averaging and measurement software at rest and at each 30 seconds throughout the exercise and recovery in leads II, V2, and V5. Discriminant function analysis was used to analyze pretest variables, as well as hemodynamic and electrocardiographic changes and symptoms during exercise. A discriminant function score was developed and compared to other treadmill scores. The setting was a 1,000 bed Veterans Affairs Medical Center (Long Beach, CA). Discriminant function analysis chose age, smoking status, presenting chest pain characteristics, and lead V5 ST slope in recovery to have independent power for separating those with and without coronary artery disease. A discriminant function score using these four variables was used to form a receiver operating characteristics curve (and derive receiver operating characteristics curve areas) for comparison to other exercise test methods and scores: (discriminant function score = .81; slope 3.5 minutes into recovery in lead V5 = .73; traditional ST amplitude method = .72; ST60/HR index (amplitude of ST depression 60 ms after the J point/delta heart rate) = .66; traditional ST amplitude/HR index (traditional method/delta heart rate) = .75; Hollenberg score = .68; Hollenberg areas only = .66; and ST integral = .66. Receiver operating characteristics curve analysis revealed a trend for the discriminant function score to be superior to all other measurements and scores. Recovery ST slope in lead V5 performed as well as or better than all other electrocardiographic criteria or treadmill scores except for the authors' discriminant function score.

Development and validation of a logistic regression-derived algorithm for estimating the incremental probability of coronary artery disease before and after exercise testing

OBJECTIVES

Our goals were to develop and validate a multivariate algorithm for estimating the incremental probability of the presence of coronary artery disease.

BACKGROUND

Multivariate methods, including logistic regression analysis, have been extensively applied to diagnostic exercise testing. However, few previous studies have included both an incremental design and external validation.

METHODS

A retrospective collection of clinical, exercise test and catheterization data was performed involving four U.S. referral medical centers. All patients had no prior history of coronary disease and had undergone coronary angiography < or = 3 months after exercise stress testing. An algorithm was developed in one center (590 patients with a 41% prevalence of coronary artery disease) with the use of logistic regression analysis and was validated in the other three centers (1,234 patients, 70% prevalence). The algorithm incorporated pretest variables (age, gender, symptoms, diabetes, cholesterol), exercise electrocardiographic (ECG) variables (mm of ST segment depression, ST slope, peak heart rate, metabolic equivalents [METs], exercise angina) and one thallium variable. Discrimination was measured with receiver operating characteristic curve analysis. Calibration (that is, reliability) was assessed from a comparison of probability estimates and the actual prevalence of disease.

RESULTS

The overall incremental receiver operating characteristic curve areas for the validation group were pretest, -0.738 +/- 0.016; postexercise ECG, 0.78 (SE 0.017); and postthallium, 0.82 (SE 0.016); p < 0.01 for both increments. Within the three validation institutions, the institution with a disease prevalence closest to that of the derivation institution had the best incremental receiver operating characteristic curve areas. There was a stepwise incremental improvement in calibration especially from exercise ECG to thallium testing.

CONCLUSIONS

An incremental multivariate algorithm derived in one center reliably estimated disease probability in patients from three other centers. The incremental value of testing was best demonstrated when the derivation and validation groups had a similar disease prevalence. This algorithm may be useful in decision making that relates to the diagnosis of coronary disease.

The importance of assessing time-course behaviour of abnormal ST/T changes after exercise

Routine stress electrocardiography has been criticised for yielding too many so-called 'false-positive' results because ST/T changes that develop during and after exercise are prevalent. Recent studies in our institution indicate, however, that the time-course behaviour patterns of these ST/T configurational 'abnormalities' after exercise are different from those reflecting myocardial ischaemia due to epicardial coronary artery disease (CAD). Time-course analysis increases the predictive value of exercise testing and has dramatically decreased the number of asymptomatic subjects or symptomatic patients at low risk of having CAD being subjected to coronary arteriography in our institution. Our method of assessing post-exercise time course patterns of abnormal ST/T are described in detail. Ischaemic ST/T abnormalities have late onset, early offset or early onset, late offset whereas those ST/T changes associated with normal epicardial coronary arteries have late onset, late offset or early onset, early offset post-exercise time course patterns.

Transient ST segment depression during Holter monitoring: how to avoid false positive findings

To increase the specificity of 24-hour Holter monitoring in detecting transient myocardial ischemia, we separated genuine ST deviations from those dependent on artifacts by adding a detailed shape analysis of real-time printouts to the usual criteria of significant ST segment depression. We screened 116 apparently healthy subjects; 31 had to be excluded, because of pathologic findings in preliminary examinations. The remaining 85 (49 women and 36 men; mean age, 43.1 years) underwent Holter monitoring for assessment of the extent, frequency, and duration of episodes of horizontal and descending ST segment depression of at least 0.1 mV that persisted for at least 60 msec after the J point and that were at least 1 minute apart. On the basis of these criteria, six subjects (7.1%) showed 24 episodes of horizontal or descending ST segment depression with a mean of 0.2 mV (range, 0.15 to 0.25 mV), a frequency of four episodes per 24 hours (one to nine), and a duration of 12.2 minutes (range 3-range 41 minutes). Supplementary criteria--e.g., sudden onset of ST segment depression, identical orientation of PQ and ST segments, or simultaneous increase in R and P wave amplitude--made it possible to identify ST changes caused by artifacts in four volunteers. In only two subjects (2.4%) could true silent ischemia not be differentiated from false positive results. Thus consideration of only the extent, frequency, and duration of episodes does not permit a differentiation between true silent ischemia and false positive results. A supplementary shape analysis increases the specificity of ST segment analysis in detecting transient myocardial ischemia during 24-hour Holter monitoring.

To Combat Hypertension, Increase Activity

In brief Controversy persists over the effects of aerobic exercise on persons with essential hypertension, but most evidence indicates that exercise is beneficial. The higher the blood pressure and less active the patient, the greater the likelihood of blood pressure reduction with exercise. For sedentary patients, moderate activity is usually more beneficial than a strenuous exercise regimen. Exercise usually can be tried before medication, unless the hypertension is severe.

Logistic discriminant analysis improves diagnostic accuracy of exercise testing for coronary artery disease in women

BACKGROUND

Diagnostic accuracy of the exercise electrocardiogram in women has been shown to be limited for the detection of coronary artery disease. New diagnostic methods based on computer analysis of the exercise electrocardiogram and multivariate analysis have improved the diagnostic value of exercise testing in male subjects. The aim of the present study was to assess whether the diagnostic value of exercise testing can be enhanced in women by using multivariate analysis of exercise data.

METHODS AND RESULTS

Between 1978 and 1984, 135 infarct-free women underwent exercise testing and coronary angiography. Significant coronary artery disease was present in 41% of the patients. In this first group, maximal exercise variables were submitted to a stepwise logistic analysis. Work load, heart rate, and ST60X were selected to build a diagnostic model. The model was tested in a second group of 115 catheterized women (significant coronary artery disease in 47%) and of 76 volunteers. We compared the present model with conventional analysis of the exercise electrocardiogram, with ST changes adjusted for heart rate, and with a previously described analysis. In both groups, sensitivity was better with the present model (66% and 70%) than by conventional (68% and 59%) and by the previously described analysis (57% and 44%) without a loss of specificity (85% and 93%). Receiver-operator characteristic curves showed also a better diagnostic accuracy with the present model.

CONCLUSIONS

In women, logistic analysis of exercise variables improves the diagnostic value of exercise testing. It yields a significantly better sensitivity without a loss of specificity.

Perioperative myocardial ischemia in patients undergoing noncardiac surgery--I: Incidence and severity during the 4 day perioperative period. The Study of Perioperative Ischemia (SPI) Research Group

To determine the incidence and characteristics of perioperative myocardial ischemia, the electrocardiographic (ECG) changes consistent with ischemia during the 4 day perioperative period were documented and characterized in 100 patients with or at risk for coronary artery disease undergoing noncardiac surgery. Using continuous two channel ECG monitoring (leads CC5 and CM5), the frequency and severity of ECG ischemic episodes defined by ST segment depression greater than or equal to 1 mm or elevation greater than or equal to 2 mm during the preoperative (up to 2 days), intraoperative and early postoperative (first 2 days) periods were compared. Preoperatively, 28 patients (28%) exhibited 105 episodes of ischemia; intraoperatively, 27 patients exhibited 39 episodes and postoperatively, 42 patients exhibited 187 episodes. There was no difference between the pre- and intraoperative episode characteristics. However, postoperative ischemic episodes were the most severe. The mean ST change was 1.5, 2 and 2.6 mm for pre-, intra- and postoperative episodes, respectively (p less than 0.0001 postoperative versus pre- or intraoperative); duration of ischemic episodes was 69, 45 and 207 min, respectively (p less than 0.005 postoperative versus preoperative, p less than 0.001 versus intraoperative) and area under the ST curve was 88, 74 and 383 mm.min (p less than 0.009 postoperative versus preoperative, p less than 0.005 versus intraoperative). Ninety-four percent of all postoperative ischemic episodes were silent; 80% of all episodes occurred without acute change (+/- 20% of control) in heart rate and 77% of intraoperative episodes occurred without acute change in blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Heart rate adjustment of exercise-induced ST segment depression. Improved risk stratification in the Framingham Offspring Study

BACKGROUND

Simple heart rate adjustment of ST segment depression during exercise (delta ST/HR index) and the pattern of ST depression as a function of heart rate during exercise and recovery (the rate-recovery loop) have been shown to improve the ability of the exercise electrocardiogram to detect the presence of coronary heart disease (CHD), but the performance of these methods for the prediction of future coronary events remains to be examined.

METHODS AND RESULTS

We compared the delta ST/HR index and the rate-recovery loop with standard electrocardiographic criteria for prediction of CHD events in 3,168 asymptomatic men and women in the Framingham Offspring Study who underwent treadmill exercise electrocardiography and who, at entry, were free of clinical and electrocardiographic evidence of CHD. After a mean follow-up of 4.3 years, there were 65 new CHD events: four sudden deaths, 24 new myocardial infarctions, and 37 incident cases of angina pectoris. When a Cox proportional hazards model with adjustment for age and sex was used, a positive exercise electrocardiogram by standard criteria (greater than or equal to 0.1 mV horizontal or downsloping ST segment depression) was not predictive of new CHD events (chi 2 = 0.40, p = 0.52). In contrast, stratification according to the presence or absence of a positive delta ST/HR index (greater than or equal to 1.6 microV/beat/min) and a positive (counterclockwise) rate-recovery loop was associated with CHD event risk (chi 2 = 9.45, p less than 0.01) and separated subjects into three groups with varying risks of coronary events: high risk, when both tests were positive (relative risk 3.6; 95% confidence interval, 2.4-5.4); intermediate risk, when either the delta ST/HR index or the rate-recovery loop was positive (relative risk, 1.9; 95% confidence interval, 1.3-2.8); and low risk, when both tests were negative. After multivariate adjustment for age, sex, smoking, total cholesterol level, fasting glucose level, diastolic blood pressure, and electrocardiographic evidence of left ventricular hypertrophy, the combined delta ST/HR index and rate-recovery loop criteria remained predictive of coronary events (chi 2 = 5.45, p = 0.02).

CONCLUSIONS

Heart rate adjustment of ST segment depression by the delta ST/HR index and the rate-recovery loop during exercise electrocardiography can improve prediction of future coronary events in asymptomatic men and women.

Variability in the accuracy of the exercise ST-segment in predicting the coronary angiogram: how good can we be?

In order to evaluate the variability in the diagnostic accuracy of the exercise electrocardiogram, a meta-analytic database derived from a review of 147 publications and a multicenter database derived from 2,826 angiographic referrals were analyzed. Wide variability in sensitivity and specificity were found from the meta-analytic review (standard deviations of 16% and 15%, respectively). No improvement in reported sensitivities and specificities has been seen over the past 22 years. The sensitivities and specifities derived from the multicenter database also showed wide variability (standard deviation 13% and 5%). These results suggest that despite obvious technologic strides in acquiring, processing, and interpreting exercise ECG signals, the accuracy of the exercise induced ST depression has not increased greatly and is difficult to ascertain a priori in a given laboratory. Individual anatomic and physiologic differences are postulated as limiting factors in the accuracy that can be obtained from this noninvasive test.

Characteristics of electrocardiographic ischemia in high-risk patients undergoing surgery. Study of Perioperative Ischemia (SPI) Research Group

Perioperative cardiac morbidity remains a significant problem in both cardiac and noncardiac surgical patients. The role of perioperative myocardial ischemia appears to be important and is under active investigation. In a series of studies in 200 high-risk patients undergoing noncardiac surgery or coronary artery bypass graft (CABG) surgery, we measured the pre-, intra-, and post-operative electrocardiographic (ECG) ischemic patterns using either continuous 2-lead ambulatory (Holter) monitoring or continuous 12-lead (modified treadmill) monitoring. Electrocardiographic ischemic episodes were defined as reversible ST-segment changes lasting at least 1 min and involving a shift from baseline (adjusted for positional changes) of greater than or equal to 0.1 mV of ST depression (with slope less than or equal to 0) at J + 60 ms or 0.2 mV of ST elevation at the J-point. During the 2-day period preceding surgery, ECG ischemic changes were common, clinically silent, and usually independent of changes in myocardial oxygen demand. Intraoperatively, using continuous 12-lead ECG, we found a 25% incidence of ischemia, for which modified leads V5, V4, and II were the most sensitive. Most ECG ischemic episodes were supply-dependent, not demand-dependent. Comparing the pattern of intraoperative ischemia with the chronic ambulatory preoperative pattern, we found that, under conditions of strict hemodynamic control, intraoperative ischemia apparently recapitulated the preoperative pattern, and that the stresses of anesthesia and surgery contributed less than previously thought. The highest incidence of ischemia occurred postoperatively, ranging between 30% and 60%, in both cardiac and noncardiac surgical patients.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of methods of analysing exercise tests for diagnosis of coronary artery disease

The diagnostic accuracy of the following methods of analysing exercise tests were evaluated: (a) the cumulative area of ST segment depression during exercise normalised for workload and heart rate (exercise score); (b) discriminant analysis of electrocardiographic exercise variables, workload, and symptoms; and (c) ST segment amplitude changes during exercise adjusted for heart rate. Three hundred and forty five men without a history of myocardial infarction were studied. One hundred and twenty three were apparently healthy. Less than half (170) had coronary artery disease. All had a normal electrocardiogram at rest. A Frank lead electrocardiogram was computer processed during symptom limited bicycle ergometry. The accuracy of the exercise score (a) was low (sensitivity 67%, specificity 90%). Discriminant analysis (b) and ST segment amplitude changes adjusted for heart rate (c) had excellent diagnostic characteristics (sensitivity 80%, specificity 90%), which were little affected by concomitant use of beta blockers. Both methods seem well suited for diagnostic application in clinical practice.

Recovery-phase patterns of ST segment depression in the heart rate domain. Identification of coronary artery disease by the rate-recovery loop

Although the time course of ST segment depression after exercise has been related to the presence and severity of coronary artery disease, recovery-phase patterns of ST segment depression with reference to changing heart rate have not been quantified. We have found distinct recovery loop patterns of ST segment depression that distinguish subjects without coronary disease from patients with coronary artery disease when ST segment depression is examined in the heart rate domain. Continuous plots of ST segment depression and heart rate were constructed throughout treadmill exercise and recovery in 100 clinically normal subjects, in 124 patients with coronary artery disease proven by catheterization, and in 17 patients with no significant coronary disease at catheterization. Among clinically normal subjects, 95% (95 of 100) had normal (clockwise) rate-recovery loops, and 5% (five of 100) had abnormal (counterclockwise) rate-recovery loops. In these normal subjects, the resulting 95% specificity of a normal rate-recovery loop was similar to the 93% (93 of 100) specificity of standard end-exercise ST segment depression criteria. Among patients with coronary disease proven by angiography, 93% (115 of 124) had abnormal (counterclockwise) rate-recovery loops, and 7% (nine of 124) had normal rate-recovery loops. In contrast was the significantly lower 74% (92 of 124) sensitivity of standard ST segment criteria (p less than 0.001 vs. the rate-recovery loop). Specificity of a normal rate-recovery loop (71%, 12 of 17) and standard ST segment depression criteria (71%, 12 of 17) were similar in the patients with normal coronary arteries at angiography.(ABSTRACT TRUNCATED AT 250 WORDS)

An algorithm for the quantification of ST-T segment variability

A template boundary algorithm which quantitatively determines repolarization (ST-T segment) variability in a normal population has been developed. The algorithm defines an initial ST-T template for comparison with successive beats. Variability is quantified using boundary limits around the template which are widened, when necessary, to included incoming ST-T segments. The boundaries at the end of each hour are stored and the collection of boundaries over a set of normal subjects quantifies the normal variation over the entire ST-T segment. The algorithm can be used to determine prospectively normal ST-T variability based on a regression analysis of R-wave or T-wave amplitude, and QT interval. Application of these boundary predictions should be useful in distinguishing repolarization changes secondary to ischemia from normal variability.

Usefulness of thallium-201 scintigraphy in predicting the development of angina pectoris in hypertensive patients with left ventricular hypertrophy

Hypertension and left ventricular (LV) hypertrophy are independent risk factors for the development of coronary artery disease. To determine whether patients at higher risk for coronary artery disease can be identified, 40 asymptomatic hypertensive men with LV hypertrophy were prospectively studied using exercise thallium-201 scintigraphy and exercise radionuclide angiography. Endpoints indicative of coronary artery disease were defined as the subsequent development of typical angina pectoris, which occurred in 8 patients during a median follow-up of 38 months, or myocardial infarction, which did not occur. The exercise electrocardiogram was interpreted by standard ST-segment criteria and by a computerized treadmill exercise score. Abnormal ST-segment responses were present in 16 of the 40 hypertensives (40%), whereas the treadmill score was positive in 8 of those same 40 patients (20%). Scintigraphic perfusion defects assessed both visually and semiquantitatively were observed in 8 of 40 (20%) patients. An abnormal ejection fraction response to exercise was present in 40% (16 of 40) of patients, and 3 of 40 (7.5%) developed new wall motion abnormalities during exercise. Six of 8 patients with either perfusion defects or abnormal treadmill score developed typical angina during follow-up. All 5 patients with concordant positive exercise scintigrams and treadmill score developed chest pain during follow-up and had coronary artery disease confirmed by coronary angiography. However, only 7 of 16 (44%) patients with positive ST changes or abnormal ejection fraction responses during exercise developed chest pain during follow-up. In contrast, of 32 patients with negative scintigrams only 2 developed atypical chest pain syndromes, and significant coronary artery disease was excluded by angiography in 1 patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Random exercise stress test in diagnosing effort angina

To improve the performance of exercise stress testing in the diagnosis of effort angina while minimizing risks of serious complications, we evaluated an impulse response of ST changes, which is a transient ST response resulting from a hypothetical, strenuous-impulselike exercise, without actually imposing the strenuous load. To obtain the impulse response, subjects walked intermittently according to a computer-generated random binary sequence on a treadmill for 20 minutes (with a constant speed of 1.7 mph and a slope of 10%). We used Fourier transform for beat-to-beat changes in ST level and the binary sequence of exercise. We then determined the transfer function by taking the ratio of Fourier transformed ST level to exercise over the frequency range of 0.5 through 5.0 cycles/min. Converting the transfer function to the time domain yielded the impulse response of ST change. The subjects consisted of 49 patients (60 +/- 9 years) with effort angina, 13 patients with atypical chest pain (56 +/- 9 years), and 30 healthy, male volunteers (23 +/- 7 years). In 82 subjects (89%), the ST impulse response showed an initial depression followed by a smooth, gradual restoration toward the preexercise ST level (type I response). The average duration of the initial depression was 8 +/- 3 seconds in the healthy volunteers, whereas it was significantly prolonged to 23 +/- 14 seconds in effort angina (p less than 0.05). The depression in patients with atypical chest pain was not significantly different from that in the healthy volunteers.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative grading of exercise stress test for patients with coronary artery disease using multivariate discriminant analysis

A group of 111 male patients who had undergone maximal or symptom-limited maximal exercise stress testing for evaluation of coronary artery disease (CAD) were subjected to coronary angiography. Group I comprised 33 patients with normal or single-vessel disease (SVD), while 78 patients with double-vessel disease (DVD) or triple-vessel disease (TVD) formed Group II. On univariate analysis of the exercise test, the following variables were found to be of significance in discriminating between the two groups: age, exercise duration, double product (heart rate X systolic blood pressure) at peak exercise, duration of ST-segment depression, number of leads showing ST depression, ST depression of 1 mm or more, configuration of the depressed ST segment, and diastolic blood pressure response to exercise. Multivariate analysis however revealed that only the following five variables had significant discriminant power: number of leads showing ST depression, exercise duration, double product, diastolic pressure response, and ST-segment configuration. On the basis of their relative importance, a regression equation was developed to give a quantitative score to individual patients. A score of less than zero detected multivessel disease (MVD) with high specificity (94%) and sensitivity (70%), while a score of 15 or more almost excluded MVD (sensitivity 87%). The scoring system as reported here improved the exercise stress test interpretation when compared with the conventional reporting system.

Systemic hypertension, left ventricular hypertrophy and coronary artery disease

The potential mechanisms for the development of myocardial ischemia in hypertensive left ventricular (LV) hypertrophy involve changes in the coronary circulation characterized by a reduction of coronary vascular reserve and an acceleration of the atherosclerotic process. This combination of factors is probably reflected in the epidemiologic findings of increased coronary morbidity and mortality in hypertension, particularly when it is associated with LV hypertrophy. The failure of several antihypertensive trials to reduce coronary morbidity and mortality emphasizes the importance of early detection of significant coronary artery disease (CAD) among hypertensive patients with LV hypertrophy. A strategy to detect asymptomatic CAD based on combined probability of 2 noninvasive tests is discussed. Results obtained in hypertensive LV hypertrophy showed a 20% to 30% incidence of abnormal exercise test results, and these positive findings were predictive for the development of typical angina during a 3-year follow-up. Based on these results and reported data, it is extrapolated that patients with silent ischemia may contribute up to 40% of the coronary mortality observed in previous antihypertensive trials. These findings suggest the need for an early detection and separate follow-up of these patients with silent CAD, to better assess the influence of antihypertensive treatment on coronary morbidity and mortality.

Computer-assisted versus unassisted analysis of the exercise electrocardiogram in patients without myocardial infarction

Computer-assisted interpretation of the exercise electrocardiogram has been advocated to improve the accuracy of diagnosing coronary artery disease. Its accuracy was compared with a blinded visual interpretation of exercise-induced ST depression in 271 consecutive subjects without prior myocardial infarction who were referred for coronary angiography. The sensitivity of the visual and computer readings was 0.51 and 0.51, respectively, at a specificity of 0.87. Receiver operating characteristic curves were generated for the visual and computer ST depression in lead V5. Analysis of the areas under these curves showed no significant difference between them, indicating that computer-assisted analysis was not superior to unmodified visual analysis. A similar analysis was applied to two other computer indexes reported to be superior to visual assessments (treadmill exercise score and ST index). These computer indexes were not superior to a conventional visual analysis of leads I, II, V2, V4 and V5 in predicting severe disease (greater than 50% luminal narrowing). These results suggest that computer-assisted interpretation does not improve the accuracy of exercise electrocardiography in diagnosing coronary artery disease in subjects without prior myocardial infarction.

Merits and limitations of quantitative treadmill exercise score

This study examined the ability of the treadmill exercise score (TES) in determining the presence and extent of coronary artery disease (CAD). The score was derived from the integrated area of ST segment depression and ST slope in two leads (V5 and a VF), corrected for R wave amplitude, exercise time, and percent of maximum predicted heart rate. The ST segment depression was measured at 80 msec after the J point. There were 34 patients with no significant CAD, 38 patients with one-vessel CAD (greater than or equal to 50% diameter stenosis), and 58 patients with multivessel CAD. The TES showed a considerable scatter in patients with and without CAD. A receiver operating characteristic curve showed different levels of sensitivity and specificity, depending on the cut-point. The TES was similar to ST segment depression in detecting CAD (predictive accuracy, 77% vs 78%, p = NS). A markedly abnormal score (less than -1.0) was seen in 41 patients, of whom 32 (78%) had multivessel CAD. On the other hand, a score greater than 0 was seen in 49 patients, of whom 40 (82%) had no or one-vessel CAD. In 40 patients with TES between -1.0 and 0, 17 (43%) had multivessel CAD and 23 (57%) had no or one-vessel CAD. In 51 patients with nondiagnostic ST changes, the TES correctly classified the extent of CAD in 20 patients (40%). Thus, the TES has a similar accuracy to the ST segment depression criteria in detecting CAD. The extent of CAD can, however, be ascertained in 80% of the patients with very high or very low TES.

Reliability of walking endurance with an incremental treadmill test

Treadmill walking endurance is the major outcome measure for intervention studies on patients with intermittent claudication. The measurement properties of this test have not, however, been well documented. We assessed the test-retest reliability of treadmill walking endurance in 10 normal subjects with a mean (+/- 1SD) age of 27.5 (+/- 3.3) years. On four occasions, at intervals of at least one week, each subject walked on a motorized treadmill to the limits of his or her capabilities. With the standard protocol, subjects began at a very low exercise intensity (0.25 m/sec, 0% grade), which increased in either speed or grade at ninety-second intervals through a maximum of fifteen stages to 2.75 m/sec and 20% grade. On the final occasion, 5 of the subjects were tested twice with a fifteen-minute interval, using a truncated protocol starting at stage five (1.25 m/sec, 0% grade). Within-subject standard deviations were low, averaging twenty-three seconds (2.1%). Reliability was very high for the first three tests with the standard protocol (r greater than or equal to 0.98, p less than 0.0001) and for the 5 subjects tested and retested with the short interval and truncated protocol (r = 0.99, p less than 0.0002), while the correlation between the standard protocol and the truncated protocol was somewhat lower (r greater than 0.81, p less than 0.01). For young normal subjects the measurement of walking endurance with an incremental treadmill test is highly reliable, but the limits of reliability need to be considered when conclusions are drawn from such measures.

Current review of exercise testing: application and interpretation

Exercise testing has changed dramatically in scope over the past 50 years. While initially used to assess functional capacity, it is now also utilized to detect the presence and severity of coronary artery disease (CAD), to evaluate postmyocardial infarction patients at risk for future cardiac events, to screen certain asymptomatic populations for CAD, and to evaluate dysrhythmias, peripheral vascular disease, and lung disease. Dynamic exercise in continuous multistage protocols is most popularly employed because of the more easily measured workload. The safety of exercise testing, its contraindications and termination end points are summarized. The sensitivity of exercise testing ranges between 60 and 70% while specificity has been reported between 85 and 90%. Both sensitivity and specificity are enhanced through use of radionuclide exercise thallium imaging and ventricular angiography.

The changing role of the exercise electrocardiogram as a diagnostic and prognostic test for chronic ischemic heart disease

The exercise electrocardiogram has been the subject of intense research over the last 50 years, as both a diagnostic and prognostic method to assess patients with chronic ischemic heart disease. In 1986, the strengths and limitations of the technique to predict coronary and multivessel disease in clinical patient subsets are understood. The diagnostic accuracy of the test is improved by consideration of Bayesian theory, multivariate models and new non-ST segment criteria. Post-test coronary disease risk estimates are best reported in terms of a conditional probability, rather than statements of "positive" or "negative." The value of exercise testing in prognostic risk stratification is considerably enhanced by recent reports of long-term follow-up data in asymptomatic and symptomatic patients. Powerful prognostic information can be obtained when the clinical, electrocardiographic and physiologic data from the exercise test are used to formulate the post-test risk of a cardiac event, even in patients whose coronary anatomy is known. The changing role of the exercise electrocardiogram as a diagnostic and prognostic test is reviewed, with emphasis on the strengths and limitations of the procedure.