Comparison of ST segment/heart rate index to standard ST criteria for analysis of exercise electrocardiogram

Spectrum of clinical applications of interlead ECG heterogeneity assessment: From myocardial ischemia detection to sudden cardiac death risk stratification

Heterogeneity in depolarization and repolarization among regions of cardiac cells has long been recognized as a major factor in cardiac arrhythmogenesis. This fundamental principle has motivated development of noninvasive techniques for quantification of heterogeneity using the surface electrocardiogram (ECG). The initial approaches focused on interval analysis such as interlead QT dispersion and T_peak -T_end difference. However, because of inherent difficulties in measuring the termination point of the T wave and commonly encountered irregularities in the apex of the T wave, additional techniques have been pursued. The newer methods incorporate assessment of the entire morphology of the T wave and in some cases of the R wave as well. This goal has been accomplished using a number of promising vectorial approaches with the resting 12-lead ECG. An important limitation of vectorcardiographic analyses is that they require exquisite stability of the recordings and are not inherently suitable for use in exercise tolerance testing (ETT) and/or ambulatory ECG monitoring for provocative stress testing or evaluation of the influence of daily activities on cardiac electrical instability. The objectives of the present review are to describe a technique that has been under clinical evaluation for nearly a decade, termed "interlead ECG heterogeneity." Preclinical testing data will be briefly reviewed. We will discuss the main clinical findings with regard to sudden cardiac death risk stratification, heart failure evaluation, and myocardial ischemia detection using standard recording platforms including resting 12-lead ECG, ambulatory ECG monitoring, ETT, and pharmacologic stress testing in conjunction with single-photon emission computed tomography myocardial perfusion imaging.

Exercise and pharmacologic stress-induced interlead T-wave heterogeneity analysis to detect clinically significant coronary artery stenosis

BACKGROUND

Despite widespread use of ETT and vasodilator-stress with myocardial perfusion imaging (MPI) for noninvasive detection of flow-limiting coronary artery disease, there is continued need to improve diagnostic accuracy. We examined whether measurement of interlead T-wave heterogeneity (TWH) during exercise tolerance testing (ETT) or pharmacologic stress testing improves detection of stenoses in large epicardial coronary arteries.

METHODS

All 137 patients at our institution who underwent diagnostic coronary angiography within 0 to 5 days after ETT (N = 81) or dipyridamole IV infusion (N = 58) in 2016 were studied, including 2 patients with both tests. Cases (N = 93) had angiographically significant stenosis (≥50% of left main or ≥ 70% of an epicardial coronary artery ≥2 mm in diameter); controls (N = 44) did not. TWH, i.e., interlead splay of T waves, was determined by second central moment analysis from precordial leads by an investigator blinded to angiographic results.

RESULTS

At rest, TWH levels were similar for cases and controls. ETT and dipyridamole stress testing increased TWH by 69% (p < 0.0001) and 27% (p < 0.0001), respectively, in cases. In controls, TWH did not change. Areas under the ROC curves for TWH increase for any flow-limiting coronary artery stenosis were 0.737 (p < 0.0001) for ETT and 0.818 (p < 0.0001) for dipyridamole stress testing. By contrast, neither ST-segment changes during ETT (p = 0.12) nor MPI during dipyridamole stress testing (p = 0.60) discriminated cases from controls.

CONCLUSIONS

TWH measurement is a novel method that improves detection of angiographically confirmed flow-limiting stenoses in large epicardial coronary arteries during both ETT and MPI during pharmacologic stress testing with dipyridamole.

Application of exercise ECG stress test in the current high cost modern-era healthcare system

Exercise electrocardiogram (ECG) tests boasts of being more widely available, less resource intensive, lower cost and absence of radiation. In the presence of a normal baseline ECG, an exercise ECG test is able to generate a reliable and reproducible result almost comparable to Technitium–99 m sestamibi perfusion imaging. Exercise ECG changes when combined with other clinical parameters obtained during the test has the potential to allow effective redistribution of scarce resources by excluding low risk patients with significant accuracy. As we look towards a future of rising healthcare costs, increased prevalence of cardiovascular disease and the need for proper allocation of limited resources; exercise ECG test offers low cost, vital and reliable disease interpretation.

This article highlights the physiology of the exercise ECG test, patient selection, effective interpretation, describe previously reported scores and their clinical application in today’s clinical practice.

An update on exercise stress testing

Exercise stress testing is the most commonly used noninvasive method to evaluate for coronary artery disease in men and women. Although emphasis has been placed on the diagnostic value of ST-segment depression, the exercise stress test provides other valuable diagnostic and prognostic data, beyond ST-segment depression. The value of these variables, which include exercise capacity, chronotropic response, heart rate recovery, blood pressure response, and the Duke Treadmill Score, are reviewed in this article. In addition, the gender differences seen with these exercise testing variables are reviewed. In this modern era of exercise stress testing, making use of all the information from a stress test and creating a comprehensive stress testing report are recommended in the evaluation of patients with suspected coronary artery disease who undergo exercise stress testing.

Is computer interpretation of the exercise electrocardiogram a reasonable surrogate for visual reading? Veterans Affairs ACME Investigators

BACKGROUND

Interpretation of exercise tests as positive or negative is primarily based upon exercise-induced ST segment changes. Consistently accurate measurements are difficult to obtain during exercise.

HYPOTHESIS

This study compared on-line computer-generated electrocardiographic (ECG) analysis with visual interpretation. The goals were to document the extent of agreement, establish reasons for disagreements, characterize ST-segment depression (extent, onset, duration), and determine the sensitivity and ability to localize coronary artery disease for each method.

METHODS

Comparisons were made in 120 patients at eight Veterans Affairs Medical Centers. An exercise test was considered positive if > 1.0 mm horizontal or downsloping ST-segment depression was detected 0.08 s after the J point during exercise or recovery. The ST-segment depression had to be present on at least two successive ECG recordings 15 s apart. Computer interpretation was based on median averaged beats.

RESULTS

There was an 88% agreement of visual and computer interpretations [106/120 (both positive, n = 62; both negative, n = 44)]. The disagreements involved visual negative, computer positive in 10 cases and visual positive, computer negative in 4 cases. Correlation was excellent between methods for characterization of ST-segment depression (p < 0.0001). Sensitivity for detecting and the ability to localize coronary artery disease (> or = 70% stenosis) were similar for both methods.

CONCLUSION

This computer algorithm using median averaged beats is a reasonable surrogate for visual interpretation of the exercise ECG, making it a valuable source of confirmation of physician readings in large research trials and in clinical settings.

[Comparative study of exercise-induced ischaemia in coronaropathy and aortic stenosis]

OBJECTIVE

To compare exercise and recovery data between a population of patients with proven CAD and patients with pure aortic stenosis (AS).

PATIENTS AND METHODS

Exercise testing results (bicycle ergometry) of 45 patients with AS (34 men, 66+/-12 years, 56+/-20 mmHg peak-to-peak gradient and valve area 0.78+/-0.48cm2) were compared to exercise testing results of 50 patients with CAD (41 men, 65+/-9 years, greater or equal to 70% stenosis on one vessel in 62%, two vessels in 30%, three vessels in 8%).

RESULTS

During exercise, 38% patients with AS and 82% patients with CAD had clinical symptoms. In the AS group, exercise duration was longer, heart rate (HR) was higher, maximal systolic and diastolic blood pressure were lower than in CAD group. The increase of systolic blood pressure was lower in the AS group (34+/-21 mmHg versus 47+/-27 mmHg, p<0.02). Maximal load achieved was not significantly different. Exercise ST depression appeared in 76% of AS group and 88% of CAD group (NS). No difference was found in ST depression, Detrano index and ST segment/HR slope. During recovery, no difference was found in HR variations. Clockwise rotation of the ST/HR recovery loop was more frequent in CAD group (35 patients versus 19 patients, p<0.001).

CONCLUSION

Most of the exercise and recovery data are similar in patients with AS and CAD. Significant discriminating criteria were the increase of systolic blood pressure during exercise and ST/HR recovery loop.

Contributions of myocardial ischemia and heart rate to ST segment changes in patients with or without coronary artery disease

BACKGROUND

ST changes related to ischemia at different heart rates (HRs) have not been well described. We aimed to analyze ST dynamic changes by vectorcardiography (VCG) during pacing-induced HR changes for subjects with proven coronary artery disease (CAD) and without (non-CAD).

METHODS

Symptomatic CAD patients scheduled for elective surgery were enrolled along with a non-CAD group. During anesthesia, both groups were placed at multiple ascending levels. VCG ST data, and in particular in ST change vector magnitude (STC-VM) from baseline, along with arterial and great coronary artery vein (GCV) blood samples were collected to determine regional myocardial lactate production.

RESULTS

A total of 35 CAD and 10 non-CAD patients were studied over six incremental 10 beat/min HR increases. STC-VM mean levels increased in the CAD group from 9+/-5 to 131+/-37 microV (standard deviation) compared with non-CAD subjects with 8+/-3-76+/-34 microV. Myocardial ischemia (lactate production) was noted at higher HRs and the positive predictive value for STC-VM to detect ischemia was 58% with the negative predictive value being 88%. STC-VM at 54 microV showed a sensitivity of 88% and a specificity of 75% for identification of ischemia.

CONCLUSIONS

Both HR and ischemia at higher HRs contribute to VCG ST elevation. Established ST ischemia detection concerning HR levels is suboptimal, and further attention to the effects of HR on ST segments is needed to improve electrocardiographic ischemia criteria.

Central haemodynamics and peripheral muscle function during exercise in patients with chronic heart failure

In this narrative review of the current literature, we examine the central and peripheral mechanisms responsible for the exercise intolerance of chronic heart failure and highlight briefly the benefits of exercise training in the treatment of this debilitating disorder. Specifically, we identify the common finding of reduced cardiac output reserve during exercise conditions leading to decreased exercise tolerance. We also reveal that the stroke volume response to exercise varies depending on the individual patient, the presence of mitral regurgitation, and the aetiology of heart failure. Chronic heart failure patients with left ventricular systolic dysfunction appear able to use the Frank-Starling mechanism to compensate (in part) for their decreased contractile reserve. Patients with left ventricular diastolic dysfunction have normal contractile function; however, they are unable to make use of the Frank-Starling mechanism during exercise conditions. We also reveal that pericardial constraint may limit diastolic filling and exercise capacity in patients with chronic heart failure. It appears that interventions that reduce pericardial constraint and mitral regurgitation enhance diastolic filling and increase exercise tolerance. A series of peripheral muscle changes also occur, including changes in muscle mass, cellular structure, energy metabolism, and blood flow. Each of these factors is associated with decreased exercise capacity and the symptoms of chronic heart failure. Exercise training has been shown to improve both central haemodynamics and peripheral muscle function leading to improvements in exercise capacity, functional status, and overall quality of life in patients with chronic heart failure.

Pathophysiologie der chronischen Herzinsuffizienz

Heart failure is a progressive and often fatal disease process. In general, the pathophysiologic mechanisms responsible for progressive myocyte dysfunction and cell loss, cardiac remodeling and arrhythmias involve signaling mechanisms that alter myocardial gene expression. These changes in gene expression are complex and involve contractile proteins, ion channels, Ca(++) handling, apoptosis, cell metabolism, the extracellular matrix, signal transduction pathways and growth factors. In the failing heart, several changes occur in cardiac adrenergic receptor-signal transduction pathways. The most striking of these changes occur in beta-adrenergic receptors, and of the changes in beta-adrenergic receptors beta1-receptor down-regulation is the most prominent. Other changes include uncoupling of beta2-adrenergic receptors and increased activity of the inhibitory G-protein. Most of these changes appear to be related to increased activity of the adrenergic nervous system, i.e. increased exposure to norepinephrine. Antagonists of the adrenergic nervous system may improve left ventricular function and outcome in patients with heart failure. This fact supports the notion that activation of these neurohormonal systems exerts a net long-term detrimental effect on the natural history of chronic heart failure and that myocardial adrenergic desensitization phenomena are at least partially maladaptive in the setting of left ventricular dysfunction. In addition to functional alterations structural remodeling plays a major role in the progression of various heart diseases to congestive heart failure. Major contributors to this remodeling process in the heart include alterations in myocyte shape, myocyte number and extracellular matrix. However, it is unclear as to which of these changes is most critical in the development of congestive heart failure, and this may vary by etiology.

ST-segment deviations during pacing-induced increased heart rate in patients without coronary artery disease

INTRODUCTION

In order to interpret ST-segment changes as an indicator of ischemia in patients with higher heart rates (HRs), the relation between ST-segment levels and HR needs to be well defined in subjects without coronary artery disease.

METHODS

Eighteen patients with normal ECGs in the catheterization laboratory, after radiofrequency ablation of AV nodal re-entry tachycardia or an accessory pathway were included. Computerized online vectorcardiography (VCG) was performed during step-wise atrial pacing-induced increases in HR up to 150 beats min(-1) (bpm). The ST-vector magnitude (ST-VM) and the relative ST change vector magnitude (STC-VM) were analysed at the J point, J + 20 and J + 60 ms.

RESULTS

There was no divergence in the course of ST-VM or STC-VM based on J point + 0, 20, or 60 ms during increasing HR. The STC-VM mean values increased progressively during increases in HR above 100 bpm, with an average increase in STC-VM of 15-20 microV per 10 bpm increases in HR. The ST-VM response during HR increases showed a heterogeneous and unpredictable pattern.

CONCLUSION

The STC-VM increases linearly with rising HRs above 100 bpm. The STC-VM can exceed widely recognized ischemic thresholds during higher HRs in the absence of ischemia. The choice of J point time to ST-VM measurements as tested here is not important for the STC-VM relation to HR at these HR levels. Further clinical testing is needed to improve the diagnostic specificity of STC-VM measurements during increased HRs.

Improved capacity of exercise electrocardiography in the detection of coronary artery disease by focusing on diagnostic variables during the early recovery phase

The temporal distribution of the diagnostic information for the detection of coronary artery disease (CAD) provided by exercise-induced electrocardiographic (ECG) ST-segment amplitude changes in different ECG leads in men and women has not been fully investigated. To shed further light in this area, 1877 electrocardiograms selected from 8322 patients undergoing a routine exercise test on a bicycle ergometer were evaluated. ST-segment amplitude and the difference between heart rate-matched recovery and exercise ST-segment amplitudes (ST/HR difference) were measured. Coronary artery disease was verified angiographically in 669 patients and excluded in 1208 patients by angiography (n = 119), by myocardial scintigraphy (n = 250), or on clinical grounds (n = 839). The diagnostic performance of the 2 ECG methods used was assessed by constructing receiver operating characteristic curves for each sampling point every 12 seconds during 10 minutes of recovery as well as the last 4 minutes of exercise for the ST-segment amplitude. ST-segment amplitude performed better after exercise than during exercise and best within the first 2 minutes of recovery. Its diagnostic ability did not differ from the ST-amplitude hysteresis assessed by the difference between recovery ST-segment amplitude and exercise ST-segment amplitude at matched heart rate. Both methods performed better in men and the diagnostic information appeared mainly in leads I, -aVR, II, V 4 , V 5 , and V 6 . The best discrimination of CAD is provided by analysis of ST-segment amplitude changes in 6 specific leads early during the recovery phase. This information should be targeted by exercise ECG diagnostic methods.

PKA-mediated phosphorylation of the beta1-adrenergic receptor promotes Gs/Gi switching

Recently, it has been shown that PKA-mediated phosphorylation of the beta(2)-adrenergic receptor (beta(2)-AR) by the cyclic AMP-dependent protein kinase (PKA) reduces its affinity for G(s) and increases its affinity for G(i). Here we demonstrate that, like the beta(2)-AR, the beta(1)-AR is also capable of "switching" its coupling from G(s) to G(i) in a PKA-dependent manner. The beta(1)-AR is capable of activating adenylate cyclase via G(s), and can also activate the extracellular-regulated kinases, p44 and p42 (ERK1/2). In transfected CHO cells, the observed beta(1)-AR-mediated activation of ERK is both sensitive to pertussis toxin (PTX), indicating involvement of G(i)/G(o), and to the PKA inhibitor, H-89. beta(1)-ARs with PKA phosphorylation sites mutated to alanines are unable to activate ERK. Mutating these same residues to aspartic acid, mimicking PKA phosphorylation, leads to a decrease in G(s)-stimulated cAMP accumulation and an increase in PTX-sensitive ERK activation. These results strongly support the hypothesis that the beta(1)-AR, like the beta(2)-AR, can undergo PKA-dependent "G(s)/G(i) switching".

Better decisions through science: exercise testing scores

Statistical tools can be used to create scores for assisting in the diagnosis of coronary artery disease and assessing prognosis. General practitioners and internists frequently function as gatekeepers, deciding which patients must be referred to the cardiologist. Therefore, they need to use the basic tools they have available (ie, history, physical examination and the exercise test) in an optimal fashion. Scores derived from multivariable statistical techniques considering clinical and exercise data have demonstrated superior discriminating power compared with diagnosis only using the ST segment response. In addition, by stratifying patients as to probability of disease and prognosis, they provide a more practical management strategy than a response of normal or abnormal. Although computers, as part of information management systems, can calculate complicated equations and derive these scores, physicians are reluctant to trust them. However, when represented as nomograms or simple additive discrete pieces of information, scores are more readily accepted. The scores have been compared with physician judgment and have been found to estimate the presence of coronary disease and prognosis as well as expert cardiologists and often better than nonspecialists. However, the discriminating power of specific variables from the medical history and exercise test remains unclear because of inadequate study design and differences in study populations. Should expired gases be substituted for estimated METs? Should ST/heart rate index be used instead of putting ST depression and heart rate separately into the models? Should right-sided chest leads and heart rate in recovery be considered? There is a need for further evaluation of these easily obtained variables to improve the accuracy of prediction algorithms, especially in women. The portability and reliability of scores must be ensured because access to specialized care must be safeguarded. Assessment of the clinical and exercise test data and application of the newer scores can empower the clinician to assure the cardiac patient access to appropriate and cost-effective cardiologic care.

Assessing patients with possible heart disease using scores

Multivariable analysis of clinical and exercise test data has the potential to become a useful tool for assisting in the diagnosis of coronary artery disease, assessing prognosis, and reducing the cost of evaluating patients with suspected coronary disease. Since general practitioners are functioning as gatekeepers and decide which patients must be referred to the cardiologist, they need to use the basic tools they have available (i.e. history, physical examination and the exercise test), in an optimal fashion. Scores derived from multivariable statistical techniques considering clinical and exercise data have demonstrated superior discriminating power compared with simple classification of the ST response. In addition, by stratifying patients as to probability of disease and prognosis, they provide a management strategy. While computers, as part of information management systems, can run complicated equations and derive these scores, physicians are reluctant to trust them. Thus, these scores have been represented as nomograms or simple additive tables so physicians are comfortable with their application. Their results have also been compared with physician judgment and found to estimate the presence of coronary disease and prognosis as well as expert cardiologists and often better than nonspecialists. However, the discriminating power of specific variables from the medical history and exercise test remains unclear because of inadequate study design and differences in study populations. Should expired gases be substituted for estimated metabolic equivalents (METs)? Should ST/heart rate (HR) index be used instead of putting these measurements separately into the models? Should right-sided chest leads and HR in recovery be considered? There is a need for further evaluation of these routinely obtained variables to improve the accuracy of prediction algorithms especially in women. The portability and reliability of these equations must be demonstrated since access to specialised care must be safe-guarded. Hopefully, sequential assessment of the clinical and exercise test data and application of the newer generation of multivariable equations can empower the clinician to assure the cardiac patient access to appropriate and cost-effective cardiological care.

Exercise testing in the new millennium

In the changing economic times, internists and family physicians are becoming the main performers of the standard exercise test. The education of those noncardiologists who wish to perform exercise testing is quite important. In the new millennium, the American College of Cardiology/American Heart Association evidence-based guidelines on exercise testing continue to have a large impact. Used for diagnosis or prognosis, exercise scores such as the Duke exercise score will be applied to each test. Increased computerization and the internet will bring inexpensive web-enabled devices for sophisticated exercise testing into the doctor's office and allow remote over-reading services.

A new coronary artery disease index of treadmill exercise electrocardiograms based on the step-up diagnostic method

Treadmill exercise electrocardiography (ECG) is one of the most common noninvasive methods for detecting ischemic heart disease. However, this method has problems due to false-positive and false-negative results in a significant number of patients. The aim of this study was to determine whether the diagnostic accuracy of treadmill exercise ECG for detecting significant coronary stenosis can be improved by employing a step-up diagnostic method using multiple diagnostic indicators. We studied 273 consecutive patients (mean age, 56 +/- 9 years; 190 men and 83 women) without a history of myocardial infarction who underwent treadmill exercise ECG and coronary angiography for ischemic chest pain. Of these, 146 patients had no significant coronary stenosis, 61 had single-vessel disease, 56 had multivessel disease, and 10 patients had left main truncus disease. A multivariate logistic regression analysis was used to select 3 treadmill exercise electrocardiographic parameters that were independent predictors of the presence or absence of significant coronary stenosis: exercise-induced maximum ST-segment depression, QT dispersion immediately after exercise, and Athens QRS score. Significant coronary stenosis was diagnosed with a sensitivity of 84% and a specificity of 90% when a step-up diagnostic method using these 3 indicators was employed. These results were better than those obtained for each indicator alone (exercise-induced maximum ST-segment depression: sensitivity, 66%, and specificity, 73%; QT dispersion immediately after exercise [> or =60 ms positive]: sensitivity, 76%, and specificity, 86%; and Athens QRS score [< or =5 mm positive]: sensitivity, 72%, and specificity, 72%). We conclude that this step-up diagnostic method, using multiple diagnostic indicators, is a clinically useful predictor of the presence or absence of significant coronary stenosis.

A knowledge-based technique for automated detection of ischaemic episodes in long duration electrocardiograms

A novel method for the detection of ischaemic episodes in long duration ECGs is proposed. It includes noise handling, feature extraction, rule-based beat classification, sliding window classification and ischaemic episode identification, all integrated in a four-stage procedure. It can be executed in real time and is able to provide explanations for the diagnostic decisions obtained. The method was tested on the ESC ST-T database and high scores were obtained for both sensitivity and positive predictive accuracy (93.8% and 78.5% respectively using aggregate gross statistics, and 90.7% and 80.7% using aggregate average statistics).

Usefulness of QT dispersion immediately after exercise as an indicator of coronary stenosis independent of gender or exercise-induced ST-segment depression

Several recent studies suggest that QT dispersion on a standard 12-lead electrocardiogram is a clinically useful indicator of significant coronary stenosis. In this study, we compared the diagnostic accuracy of QT dispersion immediately after exercise as an indicator of coronary stenosis in men and women, and in the presence or absence of exercise-induced significant ST-segment depression. The subjects were 273 consecutive patients (mean age 56 +/- 9 years; 190 men and 83 women) without a history of myocardial infarction who underwent treadmill exercise electrocardiography and coronary angiography for evaluation of angina. Of these, 146 patients had no significant coronary stenosis, 61 had single-vessel disease, 56 had multivessel disease, and 10 had left main coronary artery disease. QT dispersion immediately after exercise was significantly greater in patients with significant coronary stenosis than in those without (64 +/- 14 vs 39 +/- 14 ms, p <0.01). QT dispersion immediately after exercise was significantly more sensitive in men (sensitivity 75%; specificity 85%) and significantly more specific in women (sensitivity 77%, specificity 88%) than exercise-induced significant ST-segment depression (men: sensitivity 62%, specificity 74%; women: sensitivity 81%, specificity 68%) as an indicator of significant coronary stenosis. The addition of factors such as gender and the presence or absence of exercise-induced significant ST-segment depression did not significantly alter the sensitivity and specificity of QT dispersion immediately after exercise for detecting significant coronary stenosis (patients with significant ST-segment depression: sensitivity 77%, specificity 88%; patients without significant ST-segment depression: sensitivity 72%, specificity 86%). In conclusion, QT dispersion immediately after exercise is a clinically useful indicator of significant coronary stenosis independent of gender or the presence or absence of exercise-induced significant ST-segment depression.

Value of QT dispersion in the interpretation of treadmill exercise electrocardiograms of patients without exercise-induced chest pain or ST-segment depression

It has recently been reported that increased QT dispersion seen on standard 12-lead electrocardiograms (ECGs) reflects transient myocardial ischemia. The present study investigates whether increased QT dispersion induced by exercise is a useful indicator for detecting significant coronary stenosis in patients who do not have chest pain or significant ST-segment depression in response to exercise. We studied 135 consecutive patients (mean age +/- SD, 55 +/- 9 years; 97 men and 38 women) who complained of anginal chest pain and who did not have exercise-induced chest pain or significant ST-segment depression during treadmill exercise electrocardiography. Coronary angiography was performed in all of patients. Of the 135 patients, 97 had no significant coronary stenosis, 25 had 1-vessel coronary artery disease (CAD), and 13 had multivessel CAD. QT dispersion immediately after exercise was significantly greater in the group with significant coronary stenosis than without significant coronary stenosis (62 +/- 13 vs 40 +/- 14 ms, p <0.0001). When QT dispersion >/=60 ms immediately after exercise was considered a positive result, this indicator had a sensitivity of 74%, a specificity of 85%, and an accuracy of 81% for the diagnosis of significant coronary stenosis. In conclusion, we have shown that QT dispersion immediately after exercise is useful for detecting significant CAD in patients who do not have exercise-induced chest pain or significant ST-segment depression.

Can computerization of the exercise test replace the cardiologist?

BACKGROUND

The type of practitioners who use the standard exercise test is changing. Once a tool of the cardiologist, the standard exercise test is now being performed by internists and other noncardiologists. Because this change could be facilitated by computerization similar to the computerized interpretation programs available for the resting electrocardiograph (ECG), we performed this analysis. A secondary aim was to demonstrate the effects of medication status and resting ECG abnormalities on test diagnostic characteristics because these factors affect utility of the exercise test by the generalist.

METHODS AND RESULTS

A retrospective analysis was performed of consecutive patients referred at 2 university-affiliated Veteran's Affairs Medical Centers and a Hungarian Hospital for evaluation of chest pain and possible ischemic heart disease. There were 1384 consecutive male patients without a prior myocardial infarction with complete data who had exercise tests and coronary angiography between 1987 and 1997. Measurements included clinical, exercise test data, and visual interpretation of the ECG recordings as well as more than 100 computed measurements from the digitized ECG recordings and compilation of angiographic data from clinical reports. The computer measurements had similar diagnostic power compared with visual interpretation. Computerized measurements from maximal exercise or recovery were equivalent or superior to all other measurements. Prediction equations applied by computer were superior to single ECG measurements. Beta-blockers had no effect on test characteristics, whereas resting ST depression was associated with decreased specificity and increased sensitivity.

CONCLUSIONS

Computerized exercise ST measurements are comparable to visual ST measurements by a cardiologist; computerized scores that included clinical and exercise test results exhibited the greatest diagnostic power. Applying scores with a computer allows the practicing physician to improve the diagnostic characteristics of the standard exercise test. This approach is successful even when there is resting ST depression, thus lessening the need for more expensive nuclear or imaging studies.

Effect of ST segment measurement point on performance of exercise ECG analysis

To evaluate the effect of ST-segment measurement point on diagnostic performance of the ST-segment/heart rate (ST/HR) hysteresis, the ST/HR index, and the end-exercise ST-segment depression in the detection of coronary artery disease, we analysed the exercise electrocardiograms of 347 patients using ST-segment depression measured at 0, 20, 40, 60 and 80 ms after the J-point. Of these patients, 127 had and 13 had no significant coronary artery disease according to angiography, 18 had no myocardial perfusion defect according to technetium-99m sestamibi single-photon emission computed tomography, and 189 were clinically 'normal' having low likelihood of coronary artery disease. Comparison of areas under the receiver operating characteristic curves showed that the discriminative capacity of the above diagnostic variables improved systematically up to the ST-segment measurement point of 60 ms after the J-point. As compared to analysis at the J-point (0 ms), the areas based on the 60-ms point were 89 vs. 84% (p=0.0001) for the ST/HR hysteresis, 83 vs. 76% (p<0.0001) for the ST/HR index, and 76 vs. 61% (p<0.0001) for the end-exercise ST depression. These findings suggest that the ST-segment measurement at 60 ms after the J-point is the most reasonable point of choice in terms of discriminative capacity of both the simple and the heart rate-adjusted indices of ST depression. Moreover, the ST/HR hysteresis had the best discriminative capacity independently of the ST-segment measurement point, the observation thus giving further support to clinical utility of this new method in the detection of coronary artery disease.

Usefulness of a quantitative analysis of the recovery phase patterns of the ST-segment depression in the diagnosis of coronary artery disease

PURPOSE

To assess the diagnostic value of the recovery phase patterns of the ST-segment depression in patients referred for chest pain.

PATIENTS AND METHODS

Continuous plots of ST-segment depression against heart rate during exercise and recovery were constructed within a population of 160 consecutive symptomatic patients who all had undergone catheterization (80 with > or = 1 stenosis > or = 50%). We used a new quantitative method of measurement allowing all kinds of rate recovery loops (even the so-called "intermediate" loops) to be considered for analysis. The measurements of the heart rate (HR)-adjusted ST-segment depression were performed at 20 and 60 ms from the J point, providing two different values of a quantified recovery loop index (RLI): RLI 20 and RLI 60.

RESULTS

Both RLI showed a higher specificity (0.81 +/- 0.04 and 0.74 +/- 0.05, respectively) than did the standard criterion (0.65 +/- 0.10), but the difference was significant regarding RLI 20 only (P = 0.011). As to the sensitivity, no significant differences were found among all of the criteria (0.74 +/- 0.05, 0.80 +/- 0.04, 0.76 +/- 0.05, respectively). The timing of measurements of the RLI within the repolarization phase did not affect their overall accuracy (0.77 +/- 0.03 for both RLI). The values of the receiver-operating characteristic (ROC) curve areas were significantly greater for both RLI (0.83 +/- 0.06 and 0.84 +/- 0.06 respectively) than for the standard criterion (0.75 +/- 0.07; P < 0.02). Finally, both RLI allowed to differentiate accurately the study subjects according to the number of diseased vessels, whereas the standard criterion could only distinguish between CAD patients and subjects with normal angiograms.

CONCLUSION

The quantitative analysis of the rate recovery phase patterns appears to be useful for the diagnosis of coronary heart disease and the assessment of its severity in symptomatic patients.

Diagnosis of silent myocardial ischemia using ambulatory electrocardiographic monitoring with pedometer, analysis of heart rate, and ST loop in ambulatory electrocardiogram

BACKGROUND

It has been suggested that episodes of silent myocardial ischemia (SMI) might influence the prognosis of patients with ischemic heart disease, as its consequences are similar to those of myocardial ischemia accompanied by pain. Ambulatory electrocardiogram (ECG) is generally employed in diagnosis as well as in evaluation of clinical efficacy in patients with SMI, but problems related to its application remain because of the difficulty in differentiating between nonischemic and ischemic ST-segment depressions and because of the absence of data concerning body movement.

METHODS AND RESULTS

We developed a method for simultaneously recording onto magnetic tape both the ECG chart and pedometer count, as well as a program which enables semi-automatic analysis of the heart rate (HR)-ST relationship. This new method was employed to record ambulatory ECG along with pedometer count for a total of 70 patients, consisting of 53 with coronary heart disease who were shown to have ischemic heart disease, and 17 with various heart diseases in whom coronary angiography revealed no coronary stenosis. The HR-ST relationship was assessed for periods during which steps were recorded by the pedometer, that is, when patients were confirmed to have been under exertion effort. Patients demonstrating the following findings were diagnosed as true positive for SMI: the ST segment level did not decline until HR increased to a certain threshold, and the rate of change in the ST-segment level noted thereafter was -0.025 mm/beats/min or lower; or the ST-segment depression induced by effort continued even after discontinuation of exercise, after which time HR began to decrease, and the HR-ST loop consequently described a counterclockwise rotation. Evaluation of the HR-ST relationship based on these criteria revealed excellent results, as demonstrated by values of 79.2% for sensitivity and 94% for specificity.

CONCLUSION

Our newly developed method of assessment of the HR-ST relationship via analysis of simultaneous data from an ambulatory ECG and a pedometer appears to be time saving, highly objective, and useful with regard to the diagnosis of SMI and evaluation of the therapeutic effect of drugs in patients with ischemic heart disease.

Sympathetic activity in children undergoing balloon valvuloplasty of pulmonary stenosis

We studied the influence of balloon valvuloplasty on alpha- and beta-adrenoceptor densities, plasma catecholamine, and cAMP levels in children and infants with pulmonary stenosis before and 10 min after balloon dilatation, employing as controls children undergoing transcatheter occlusion of patent ductus arteriosus (PDA) with Qp/Qs ratio < 1.5. In the PDA group, the alpha-adrenoceptor density (Bmax) was 3.75 +/- 0.72 fmol/10(7) cells (n = 15) before occlusion and remained unchanged at 3.35 +/- 0.47 fmol 10 min thereafter. In the pulmonary stenosis patients (n = 31), the receptor density was 59% higher (p < 0.05) before, and decreased to PDA levels 10 min after, the procedure. The control beta-adrenoceptor density was 64.8 +/- 11.0 fmol/10(6) cells before, and 71.2 +/- 13.2 fmol 10 min after, occlusion. In the study group, the density was 23% lower (p < 0.07) and increased to the PDA levels 10 min after the dilatation. Compared with the PDA, pre- and postdilatation plasma norepinephrine levels were not significantly changed; epinephrine was slightly elevated before, but increased by 73% after, dilatation; dopamine was 80% (p < 0.05); and cAMP was 37% higher before, and remained elevated at 70 and 23% above the PDA values after, the procedure. Accordingly, alpha-adrenoceptor density is significantly elevated in children with pulmonary stenosis and decreases significantly immediately after balloon valvuloplasty. On the other hand, beta-adrenoceptor density is attenuated and increases toward normal levels after the procedure. The immediate reversal of the receptor levels after balloon valvuloplasty suggests that this procedure exerts acute effects on the sympathetic functional level in this disease.

Asymptomatic coronary artery disease detection: update 1996. A screening protocol using 16-lead high-resolution ECG, ultrafast CT, exercise testing, and radionuclear imaging

The authors have proposed a new four-step screening algorithm to detect asymptomatic coronary artery disease (CAD) in flight school candidates, cadets, and rated flyers of the Unites States Air Force (USAF). In step 1, the USAF Armstrong Laboratory (USAF/AL) risk profile and improved 16-lead high-resolution electrocardiogram/vectorcardiogram will be recorded at baseline. On routine follow-up evaluations, quantitative serial comparisons will be performed by the method of Kornreich. In step 2, beginning with flight school candidates and cadets, all three groups will be studied by the ultrafast computed tomograph (CT) protocol. Those candidates positive for coronary calcium will be studied by coronary angiography and ventriculography, and their eligibility for continued rated flight status will be determined by present criteria. In step 3, those candidates negative for coronary calcium by ultrafast CT will then be screened by the newly defined and improved high-sensitivity treadmill exercise test criteria. In step 4, candidates with a positive treadmill exercise test result, or who are also found in the upper quintile of the USAF/AL risk profile, wild also have exercise nuclear wall motion studies and perfusion scans. If these are abnormal and suggestive of myocardial ischemia, this subset will also be studied by heart catheterization and coronary angiography, and their eligibility for continued rated flight status will be determined by present criteria. The incidence of coronary calcium/no calcium for each degree of stenosis in the 6,000 flyers in each quintile was used to develop the following projections: (1) that more than 3 of 4 rated flyers with unsuspected CAD, and (2) more than 9 of 10 with severe flow-limiting CAD can be identified by these upgraded screening procedures. Evidence is herein presented that these enhancements will result in a major (5-8-fold) increase in case finding of this disease. Based on the estimate of four lost high-performance aircrafts per year from sudden incapacitation of the pilot due to CAD, when this four-step screen is fully operational, it can be expected to reduce the $80 million annual losses to the United States government from CAD by 85%, a savings of $68 million per year.

Comparison of the diagnostic accuracy of different methods of measurement of heart rate-adjusted ST-segment depression during exercise testing for identification of coronary artery disease

Within a population of 160 consecutive symptomatic patients who all had undergone catheterization (80 with > or = 1 stenosis > or = 50%), we compared the accuracy of different computerized measurements of the exercise-induced changes in ST-segment: (1) the standard criterion (> or = 0.1 mV flat/downsloping ST depression or > or = 0.15 mV upsloping depression, both 60 ms after the J point); (2) heart rate (HR)-adjusted ST-segment depression (ST/HR index measured at 0, 20, 40, 60, and 80 ms from the J point); (3) the HR-adjusted ST integral (ST/HR integral measured from 0 to 40 ms and from 40 to 80 ms after the J point). None of the ST/HR indexes or integrals were found to have a significantly greater sensitivity than the standard criterion. On the contrary, all ST/HR indexes and integrals showed a higher specificity (0.78 to 0.89) than did the standard criterion (0.65); moreover, the earlier the measurement within the repolarization phase, the better the overall accuracy: 0.71 for the standard criterion, 0.83 (p < 0.001), 0.80 (p < 0.01), 0.78 (p < 0.02), 0.78 (p < 0.02), 0.74 (p = NS) for the ST/HR indexes at 0, 20, 40, 60, and 80 ms, respectively; 0.81 (p < 0.001) and 0.78 (p < 0.02) for the ST/HR integrals calculated from 0 to 40 and from 40 to 80 ms, respectively. Consistently, the receiver-operating characteristic curve areas of ST/HR at 0, 20, and 40 ms were greater than those of ST/HR at both 60 and 80 ms. These findings are divergent from some other results given in published reports. We conclude that the accuracy of all exercise criteria is influenced by the population analyzed: our patients were representative of those currently seen by clinicians.

Comparison of ST-segment/heart rate slope analysis with standard ST-segment measurement criteria to outcome of exercise thallium-201 imaging

We compared standard ST-segment analysis and ST/HR slope analysis of exercise ECG studies with reference to outcome of exercise thallium-201 studies in 341 patients. Sensitivity was significantly better using ST/HR slope compared with standard ST analysis. Specificity was not significantly different.

Impact of echocardiographic left ventricular mass on mechanistic implications of exercise testing parameters

Electrocardiographic left ventricular (LV) hypertrophy has long been known to be associated with an abnormal ST-segment response to exercise; this association has been considered to represent a false-positive finding. There is a paucity of data relating echocardiographic LV mass to exercise ST-segment responses and other exercise parameters. As part of a routine evaluation, 1,408 men and 1,618 women from the Framingham Heart Study who were free of clinical cardiac disease underwent echocardiography and exercise treadmill testing according to the Bruce protocol at the same clinic visit. Abnormal ST-segment responses were defined both by standard criteria and the delta ST/heart rate index. LV mass was calculated from M-mode echocardiography. Echocardiographic LV hypertrophy was associated with an abnormal delta ST/heart rate index (in men, odds ratio [OR] 1.78, 95% confidence interval [CI] 1.05 to 3.01, p = 0.03; in women, OR 2.13, 95% CI 1.31 to 3.44, p = 0.002) but not with an abnormal response according to standard criteria. Echocardiographic LV hypertrophy was also associated with a lower likelihood of achieving an age-predicted target heart rate (in men, OR 0.45, 95% CI 0.31 to 0.65, p < 0.001; in women, OR 0.53, 95% CI 0.37 to 0.76, p < 0.001) and with a lower exercise capacity. Despite these associations, echocardiographic LV hypertrophy was associated with a higher peak heart rate-systolic blood pressure double product. In conclusion, echocardiographic LV hypertrophy is associated with an abnormal ST-segment response, a lower likelihood of achieving target heart rate, decreased exercise capacity, and an increased double product, which is a reflection of myocardial oxygen demand.

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.

Antibodies to beta-adrenergic receptors disclosing agonist-like properties in idiopathic dilated cardiomyopathy and Chagas' heart disease

Recent studies confirm the existence of antibodies (Abs) to beta-adrenoceptors in patients with idiopathic dilated cardiomyopathy and Chagas' heart disease. These Abs can be shown to exert both stimulatory and inhibitory effects, which may play a role in the development of the cardiac abnormalities known to occur in these diseases, including advanced heart failure. The hypothesis is advanced that Chagas' heart disease and some forms of idiopathic dilated cardiomyopathy may represent, at least partially, a form of "adrenergic cardiomyopathy."

Solid-angle theory and heart rate adjustment of ST-segment depression for the identification and quantification of coronary artery disease

Determinants of the ST-segment response to exercise can be mathematically modeled by solid-angle theory, and heart rate adjustment of the magnitude of exercise-induced ST-segment depression can remodel the solid-angle relationship to provide a theoretic and practical basis for application of heart rate-adjusted indexes of ST depression in exercise electrocardiography. Solid-angle theory indicates that the magnitude of ST depression recorded at a surface electrode (epsilon) can be described as the product of spatial and nonspatial determinants: epsilon = (omega/4 pi).(delta Vm).K (equation 1), where omega is the solid angle subtending the boundary of the ischemic territory, delta Vm is the difference in transmembrane voltage between the ischemic and adjacent nonischemic regions, and K is a term correcting for differences in intracellular and extracellular conductivity and changes in end-plate conductance. As a consequence, the magnitude of ST depression recorded by a surface electrode will be proportional both to the area of ischemic territory subtended by the recording electrode, which reflects the solid angle, and to the local transmembrane potential difference, which in turn reflects the electric consequences of the metabolic severity of ischemia at the level of the myocardial cell. It follows from equation 1 that the amplitude of ST depression can accurately reflect the area of ischemic boundary only when the severity of ischemia is constant or otherwise controlled, and differences in ST depression will only reflect varying areas of underlying ischemia when similar severity of ischemia is present. During exercise the severity of ischemia is directly proportional to changes in myocardial oxygen demand and coronary blood flow, which in turn are directly related to increasing heart rate (delta HR). Because the change in transmembrane voltage across the ischemic boundary is linearly proportional to delta HR, delta Vm/delta HR remains constant as ischemia develops. Dividing the solid-angle relationship in equation 1 by delta HR and making the appropriate substitution for a constant delta Vm/delta HR then indicates that epsilon/delta HR = (omega/4 pi).(c . K) [equation 2], where c is the new constant. Under conditions where changes in conductance are proportional or small, this simplified relationship reduces to delta ST/delta HR = c'.omega [equation 3], where delta ST reflects the magnitude of ST depression recorded by the surface electrode, delta HR the change in heart rate during developing ischemia, and c' the resulting empiric constant.

Population selection and performance of the exercise ECG for the identification of coronary artery disease

To quantify the effect of population selection on the performance of exercise ECG criteria for the detection of coronary artery disease, the exercise ECGs of 212 clinically normal nonvolunteer subjects, 31 patients with no significant coronary disease at angiography, 153 patients with clinically stable angina, and 184 patients with catheterization-proved coronary disease were examined. Test specificity was examined separately in clinically normal subjects and in patients with angiographically normal coronary arteries, and test sensitivity was determined separately in patients with stable angina and those with catheterization-proved disease. Definition and selection of normal and abnormal study populations had marked effects on test performance. Standard ECG criteria, a simple ST depression magnitude partition of 150 microV, an ST segment/heart rate (ST/HR) index partition of 1.60 microV/beat/min, and an ST/HR slope partition of 2.40 microV/beat/min, identified coronary disease with comparably high specificities (94% to 97%) in clinically normal subjects, but with significantly lower specificities (68% to 77%, p = 0.002 to 0.0001) in patients with angiographically normal coronary arteries. Although sensitivity was significantly lower in patients with stable angina than in patients with catheterization-proved coronary disease for standard criteria (54% vs 70%, p = 0.004) and for the ST/HR index (88% vs 95%, p = 0.04), there was no significant difference in the poor sensitivity of the simple ST depression magnitude criteria (51% vs 58%) or in the high sensitivity of the ST/HR slope (93% vs 96%) in these abnormal patient groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of exercise-induced QRS amplitude changes (Athens score) and their clinical value

The index of exercises-induced amplitude changes in a combination of Q, R and S waves, named Athens score, was tested in 213 patients, who underwent coronary angiography within 3 days of a maximal exercise test. Of the 155 cases with conclusive exercise test results, according to the coronary angiography document, 23 (14.8%) were diagnosed as having no significant coronary artery disease (CAD); 27 (17.4%) as 1-vessel disease; 28 (18.1%) as 2-vessel disease and 77 (49.7%) as 3-vessel disease. The Athens score for them was 4.87 +/- 2.89, 0.02 +/- 3.35, -1.70 +/- 3.68, -1.75 +/- 3.98 respectively, F = 19.65, P < 0.01. An Athens score of 2 mm predicted CAD with sensitivity of 84.9% and specificity of 78.3% both being higher than those of ST segment depression (75.0% and 60.9%). It was concluded that the Athens score was a promising index for improving the efficiency of exercise test to predict CAD.

Measurement variables for optimal performance of the ST integral

OBJECTIVES

This study examined the effect of varied onset and offset of ST measurement on performance of the ST integral for the detection of coronary artery disease.

BACKGROUND

The J point and other early ST segment measurements may significantly reduce the accuracy of ST segment depression criteria.

METHODS

The exercise electrocardiograms (ECGs) from 112 normal subjects and 163 patients with known or likely coronary disease were analyzed, using the J point or 20 ms after the J point onset and 60 or 80 ms after the J point offset of ST integral calculation.

RESULTS

At a matched specificity of 97%, incorporation of J point measurements into the ST integral significantly reduced test performance. The ST integrals measured from the J point to 80 and to 60 ms after the J point were significantly less sensitive (31% and 25%, respectively) than those measured from 20 to 80 ms and 20 to 60 ms after the J point (39% and 31%, p < 0.001 and p < 0.01, respectively). For either J point or 20 ms after the J point onset of the ST integral measurement, the sensitivity was higher using 80 ms than 60 ms after the J point offset (31% vs. 25%, p < 0.01 and 39% vs. 31%, respectively, p < 0.001). Comparison of areas under receiver operating characteristic curves confirmed the superior performance of the ST integral measured from 20 to 80 ms after the J point relative to the other measurement intervals.

CONCLUSIONS

These findings demonstrate that J point and early repolarization phase time-voltage measurements reduce performance of the ST integral for the identification of coronary artery disease and provide further evidence that optimal signal to noise content of repolarization for the identification of ischemia can be localized to later phases of the ST segment.

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.

Value and limitations of heart rate-adjusted ST segment depression criteria for the identification of anatomically severe coronary obstruction: test performance in relation to method of rate correction, definition of extent of disease, and beta-blockade

Performance of the linear regression-based ST/HR (heart rate) slope, the simple ST/HR index, and ST segment depression alone for the identification of anatomically severe coronary obstruction was examined in relation to the definition of the extent of disease and the presence or absence of beta-blockade during treadmill exercise using the Cornell protocol in 172 catheterized patients. Whether severe disease was defined by three-vessel obstruction, by Gensini scores partitioned at 35 or at 48, or by Duke jeopardy scores exceeding 6, the 83% to 100% sensitivities of an ST/HR slope criterion of 6.0 microV/beat/min were each significantly higher than the corresponding 65% to 80% sensitivities of 150 microV of ST segment depression closely matched specificities. The ST/HR slope was significantly more sensitive than a simple ST/HR index criterion of 3.4 microV/beat/min for detection of high Gensini scores, but despite consistently intermediate performance trends, in no case did sensitivity of the simple ST/HR index criterion significantly exceed that of ST depression alone. Each method performed better and with comparable sensitivity in patients not receiving beta-blockers. In contrast, the 82% to 100% sensitivities of the ST/HR slope for identification of severe disease were significantly higher than the 63% to 77% sensitivities of ST depression in patients taking beta-blocking drugs; however, simple heart rate adjustment using the ST/HR index had intermediate performance that in no case was significantly more sensitive than ST segment depression alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnostic accuracy of seismocardiography compared with electrocardiography for the anatomic and physiologic diagnosis of coronary artery disease during exercise testing

A multicenter study was performed to compare the diagnostic accuracy of a new technique, seismocardiography, with that of electrocardiography for physiologically and anatomically significant ischemic coronary artery disease (CAD) during exercise stress testing. Five participating centers enrolled 129 patients who had simultaneous seismocardiograms and 12-lead electrocardiograms at the time of their exercise treadmill stress tests. Two different definitions of CAD were used: anatomic and physiologically significant disease. The presence of anatomically significant CAD (> or = 50% diameter stenosis) was documented by coronary angiography. Physiologically significant CAD was defined as present in the same 129 patients when coronary arteriography (> or = 50% diameter stenosis) and thallium-201 scintigraphy (defect on initial postexercise images) were both abnormal. Seismocardiography had a significantly better sensitivity for detecting anatomic CAD than did electrocardiography (73 vs 48%; p < 0.001), without loss of specificity (78 vs 80%; p = NS). Exercise seismocardiography added significant incremental diagnostic information beyond that provided by exercise electrocardiography. Seismocardiography was more sensitive (without less specificity) in women and in patients who did not achieve maximal predicted heart rate. In patients with physiologically significant CAD, the seismocardiogram was also significantly more sensitive (78%) than was the electrocardiogram (55%) (p < 0.02), without loss of specificity (84 vs 74%). Seismocardiography significantly improved sensitivity for the detection of anatomic and physiologic CAD. It is easy to perform and may be a clinically useful adjunct in exercise stress testing.

Accuracy of ST/heart rate index in the diagnosis of coronary artery disease

The accuracy of ST/heart rate (ST HR) index was evaluated in patients presenting for exercise electrocardiography with suspected coronary disease. In all, 420 patients (235 men and 185 women) with normal electrocardiograms at rest underwent exercise testing, followed within 3 months by coronary angiography. The sensitivity and specificity for standard ST criteria (greater than or equal to 1 mm horizontal or downsloping depression) were 48% (78 of 162) and 81% (208 of 258), respectively. An ST HR-index threshold of 1.86 microV/beta/min had the exact same specificity with a sensitivity of 44% (71 of 162; p = not significant). Consideration of greater than or equal to 1.5 mm upsloping depression had no significant impact on the aforementioned results. Using multivariate logistic regression analysis, age, sex, symptoms, cigarette smoking, diabetes mellitus, qualitative ST slope, rate-pressure product, METs achieved and exercise angina were evaluated with and without ST HR index and ST depression. According to this analysis, age, sex, symptoms and ST slope were good predictors of presence or absence of disease. Neither ST HR index nor ST depression had significance in the multivariate analysis. However, when a separate analysis was performed in men and women, the 2 quantitative ST variables showed significance in men, but not in women. Comparisons of discriminative accuracy using receiver-operating characteristic curves demonstrated differences between men and women, but no difference between ST HR index and ST depression. Therefore, concerning questions of coronary disease diagnosis, consideration of ST HR index was not better than standard ST criteria, and added nothing to multivariate analysis of other available variables.

Exercise-induced ST depression and ST/heart rate index to predict triple-vessel or left main coronary disease: a multicenter analysis

The aim of this investigation was to determine the difference in accuracy between two frequently published noninvasive indicators of severity of coronary artery disease (exercise-induced ST segment depression and heart rate-adjusted ST depression [ST/HR index]). The study was designed as a survey of consecutive patients undergoing exercise electrocardiography and coronary angiography. There were a total of 2,270 patients without prior myocardial infarction or cardiac valvular disease referred for angiography from eight institutions in three countries; 401 of these patients had triple-vessel or left main coronary artery disease. The sensitivities of ST depression and ST/HR index in detecting triple-vessel or left main coronary artery disease were, respectively, 75% and 78% (p = 0.08) at cut point values where their specificities were equal (64%). This small increase in the accuracy of the ST/HR index was evident only at peak exercise heart rates below the median value of 132 beats/min, where the sensitivities of ST depression and ST/HR index were 73% and 76% (p = 0.03), respectively, at cut point values corresponding to a specificity of 60%. These results were consistent at all eight participating institutions. The increase in accuracy achieved by dividing exercise-induced ST depression by heart rate is small and confined exclusively to a low exercise heart rate. This lack of superiority cannot be generalized to all methods of heart rate adjustment.