Digital supine bicycle stress echocardiography: a new technique for evaluating coronary artery disease

Typical angina during exercise stress testing improves the prediction of future acute coronary syndrome

INTRODUCTION

The prognostic value of angina during exercise stress testing is controversial, possibly due to previous studies not differentiating typical from non-typical angina. We aimed to assess the prognostic value of typical angina alone, or in combination with ST depression, during exercise stress testing for predicting cardiovascular events.

METHODS

We conducted a prospective observational cohort study including all patients who performed a clinical exercise stress test at the department of Clinical Physiology, Kalmar County Hospital between 2005 and 2012. The association between typical angina/ST depression and incident acute coronary syndrome (ACS) and cardiovascular mortality were analysed using Cox regression for long-term and 1-year follow-up.

RESULTS

Out of 11605 patients (median follow-up 6.7 years), 623 (5.4%) developed ACS and 319 (2.7%) died from cardiovascular causes. Compared to patients with no angina and no ST depression, typical angina and ST depression were associated with increased risk of future ACS; hazard ratio (HR) 3.5 ([95%CI] 2.6-4.7). This association was even stronger for ACS within one year (typical angina with and without concomitant ST depression; HR 20.8 (13.9-31.3) and 9.7 (6.1-15.4), respectively). Concordance statistics for ST depression in predicting ACS during long-term follow-up was 0.58 (0.56-0.60) and 0.69 (0.65-0.73) for ACS within one year, and 0.64 (0.62-0.66) and 0.77 (0.73-0.81), respectively, when typical angina was added to the model.

CONCLUSIONS

Typical angina during exercise stress testing is predictive of future ACS, especially in combination with ST depression, and during the first year after the test.

Early Diagnosis of Cardiovascular Diseases in Workers: Role of Standard and Advanced Echocardiography

Cardiovascular disease (CVD) still remains the main cause of morbidity and mortality and consequently early diagnosis is of paramount importance. Working conditions can be regarded as an additional risk factor for CVD. Since different aspects of the job may affect vascular health differently, it is important to consider occupation from multiple perspectives to better assess occupational impacts on health. Standard echocardiography has several targets in the cardiac population, as the assessment of myocardial performance, valvular and/or congenital heart disease, and hemodynamics. Three-dimensional echocardiography gained attention recently as a viable clinical tool in assessing left ventricular (LV) and right ventricular (RV) function, volume, and shape. Two-dimensional (2DSTE) and, more recently, three-dimensional speckle tracking echocardiography (3DSTE) have also emerged as methods for detection of global and regional myocardial dysfunction in various cardiovascular diseases and applied to the diagnosis of subtle LV and RV dysfunction. Although these novel echocardiographic imaging modalities have advanced our understanding of LV and RV mechanics, overlapping patterns often show challenges that limit their clinical utility. This review will describe the current state of standard and advanced echocardiography in early detection (secondary prevention) of CVD and address future directions for this potentially important diagnostic strategy.

Stress echocardiography from 1979 to present

Stress echocardiography was initially developed in 1979 and has seen substantial success in the evaluation of patients with known or suspected coronary artery disease. It has proven applicable to clinical questions of diagnosis, prognosis and follow-up. It has been heavily dependent on technologic advancements, initially digital capturing for side-by-side visualization and, more recently, developments in detailed methods of evaluating myocardial mechanics and contrast echocardiography for perfusion.

Potential clinical perspectives of Doppler myocardial imaging and strain rate imaging during stress echocardiography

Stress echocardiography has become a common non-invasive test in patients with chest pain and known or suspected coronary artery disease, but, as with exercise electrocardiography, it shows several major limitations. Analysis of gray-scale images based on subjective visual interpretation of wall motion and thickening has considerable variability even among experts. Doppler myocardial imaging and strain rate imaging echocardiography provides additional information in comparison with conventional echocardiography. These techniques provide quantification of regional wall motion at rest and during stress. Quantification of both systolic and diastolic myocardial function by either Doppler myocardial imaging or strain rate imaging mapping during dobutamine stress test has been shown to be a feasible, accurate, non-invasive tool that should be considered to be a sensitive alternative to the present echocardiographic and scintigraphic imaging techniques for stress tests. Time consuming off-line analysis of color images is required in the present state of technology. However, these non-invasive techniques are rapidly evolving and expanding. Further refinements in signal processing and quantitative analysis are likely in the near future.

A meta-analytic comparison of echocardiographic stressors

BACKGROUND

The relative performance of alternative stressors for stress echocardiography for the diagnosis of coronary artery disease (CAD) is not well established.

METHODS

All studies published between 1981 to December 2001 who met inclusion criteria were included in this analysis. We performed a summary receiver operator characteristic (SROC) analysis and calculated weighted mean of the likelihood ratio and sensitivity/specificity. A covariate analysis using meta-regression methods was also performed.

RESULTS

Forty-four studies presented data on Exercise, 11 on Adenosine, 80 on Dobutamine, 40 on Dipyridamole, 16 on transatrial pacing transesophageal echocardiography (Tap-TEE), and 7 on transatrial pacing transthorasic echocardiography (Tap-TTE). SROC analysis showed that the following order of most discriminatory to least: Tap-TEE, Exercise, Dipyridamole, Dobutamine and Adenosine. Weighted means sensitivity/specificity were Exercise: 82.6/84.4%, Adenosine: 68.4/80.9%, Dobutamine: 79.6/85.1%, Dipyridamole: 71.0/92.2%, Tap-TTE: 90.7/86.1%, and Tap-TEE: 86.2/91.3%. Covariate analysis showed that the discriminatory power of Exercise decreased with increasing mean age.

CONCLUSIONS

Tap-TEE is a very accurate test for both ruling in and ruling out CAD although its invasiveness may limit its clinical acceptability. Exercise is a well-balanced satisfactory test for both ruling in and ruling out but performance might be lower for the elderly. Dobutamine offers a reasonable compromise for Exercise. Dipyridamole might be good for ruling in but not for ruling out CAD. The incapability in ruling-out CAD was a major problem in clinical application of the stress. Adenosine was the least useful stressor in diagnosing CAD.

Stress Echocardiography

Stress echocardiography is commonly employed for the clinical management of known or suspected coronary artery disease. This review discusses the accuracy of the technique, which is equivalent to that of competing imaging techniques, as well as its overall role in patient management. The utilization of stress echocardiographic modalities in clinical presentations, such as chest pain, congestive heart failure, and valvular heart disease, and preoperative risk assessment, as well as determining myocardial viability, are discussed.

Relationship between the ischemic threshold at the onset of wall-motion abnormality on semisupine exercise echocardiography and the extent of coronary artery disease

Semisupine exercise echocardiography (SSEE) provides the unique opportunity of continuous monitoring of segmental wall motion during physiologic stress. We evaluated the relationship between the ischemic threshold at the onset of wall-motion abnormality on SSEE and the extent of coronary artery disease (CAD) in a consecutive series of 224 patients who underwent coronary angiography. Ischemic threshold was significantly lower for patients with multivessel disease compared with single-vessel disease: maximal workload was 102 versus 135 W (P = 1.3.10(-6)); percentage of maximal predicted heart rate achieved was 64 versus 70% (P =.004); and double product was 21,335 versus 23,389 (P =.03), respectively. Sensitivity, specificity, and positive and negative predictive values of SSEE for the detection of significant CAD (> or =60% diameter stenosis) were 81%, 74%, 90%, and 56%, respectively. SSEE is an accurate tool to diagnose CAD and the ischemic threshold at the onset of wall-motion abnormality is inversely related to the extent of CAD.

Prognostic value of contrast stress echocardiography in patients with image quality too limited for traditional noncontrast harmonic echocardiography

Clinical data and contrast stress echocardiography (CSE) results were analyzed in 283 patients to establish the prognostic value of CSE for patients with limited echocardiogram image quality at baseline. The mean follow-up period was 736 +/- 337 days. Only 7 patients (2.5%) had nondiagnostic image quality with contrast enhancement. During follow-up, 24 cardiac events (8.5%) occurred (5 cardiac-related deaths, 2 nonfatal myocardial infarction, 17 coronary revascularizations). Overall sensitivity, specificity, and positive and negative predictive values were 60.9%, 76.8%, 19.7%, and 95.5%, respectively. Kaplan-Meier event-free survival was higher for patients with a negative CSE result as compared with those with a positive CSE finding (P <.0001). In a multivariate Cox proportional hazards model, positive CSE was the strongest predictor of cardiac events (risk ratio 3.7; 95% confidence interval 1.6-8.7). CSE can successfully predict cardiac events for patients with limited noncontrast echocardiographic image quality. A negative CSE result conferred a good prognosis.

Diagnosis of ischemic heart disease with exercise echocardiography: Comparison of images obtained at peak- and post-exercise

Peak-and post-exercise stress echocardiography were compared with respect to ability to detect coronary artery disease in 138 consecutive patients undergoing supine bicycle stress echocardiography. Sixty of these patients had single-vessel disease; 37, double-vessel disease; and 19, triple-vessel disease. Exercise was performed in the 20- to 30-degree left decubitus position on an echo-bed with an ergometer. Exercise started at 50 watts and was increased in 25-watt every 3 minutes and to a maximum of 150 watts. Two-dimensional echocardiographic images were digitized and assigned in a quad-screen format for nonbiased interpretation. Total wall motion score (TWMS) was the sum of the wall motion score, from normokinesis (0) to dyskinesis (4), of 16 segments. Image quality score index (IQSI) was the mean of the image quality scores in all views. All of the patients underwent coronary arteriography. Significant coronary stenosis was defined as≧75% stenosis of the large coronary arteries. Two-dimensional echocardiographic studies were adequate for analysis in 133 patients during the peak-exercise stage (peak-exercise) and in 137 patients 30 to 60 seconds after the end of exercise (post-exercise). TWMS at peak-exercise was higher than at post-exercise, while IQSI at peak-exercise was lower than at post-exercise. Sensitivity at peak-exercise versus that at post-exercise was 91% versus 79% (p<0.05); specificity, 76% versus 85%; and diagnostic accuracy, 88% versus 80% (p<0.05), respectively. We conclude that despite poor image quality on exercise echocardiography, better diagnostic accuracy was attained by assessing wall motion changes at peak-exercise than at post-exercise.

Contribution of stress echocardiography to clinical decision making in unselected ambulatory patients with known or suspected coronary artery disease

BACKGROUND

Due to its higher diagnostic accuracy stress echocardiography (SE) has been advocated as a substitute for stress ECG to detect coronary heart disease (CAD). However, its contribution to clinical decision-making in unselected patients presenting to the ambulatory care centre for known or suspected coronary artery disease is unclear.

METHODS

To evaluate the clinical value of SE in unselected patients, we prospectively obtained SE and stress ECG in 221 consecutive patients (142 males; mean age 58+/-12 years) presenting to the ambulatory care centre with known or suspected CAD. Patients with acute coronary syndrome were not included.

RESULTS

Results of stress ECG and SE were concordant in 181 (82%) and discordant in 40 patients (18%). The clinical decision to recommend or to currently withhold coronary angiography was possible solely on the basis of clinical criteria and stress ECG findings in 191 (86.4%) patients but was guided by the results of SE in 30 patients (13.6%). Left heart catheterization and coronary angiography were conducted in 61 patients. In this population SE was more accurate (82.6%) than stress ECG (65.6%) in indicating significant coronary artery stenosis.

CONCLUSION

Despite its higher accuracy, SE adds little to the information derived from dynamic stress ECG and symptom evaluation in unselected outpatients with known or suspected CAD. Thus, SE should not in general replace stress ECG as a screening method for detecting significant coronary artery disease, for both clinical and economic reasons.

The clinical use of imaging techniques with exercise testing

The addition of nuclear imaging techniques to basic exercise electrocardiography (ECG) has provided significant diagnostic and prognostic information in the evaluation of patients with suspected coronary artery disease. During the last decade, new classes of isotopes (technetium-and rubidium-based perfusion agents) and refinements in single-photon emission computed tomography (SPECT) and positron emission tomography (PET) have become better accepted. These new studies have added to the diagnostic armamentarium available to physicians, but at considerable costs with an estimated 4.8 million procedures performed this year. Nuclear imaging techniques can assess myocardial blood flow (perfusion imaging) or function (ventriculography). Another imaging modality, stress echocardiography, has also achieved widespread acceptance with clinical guidelines for its use published in 1997. This review addresses these imaging techniques in diagnostic evaluation of the patient with suspected coronary artery disease.

Cost-effectiveness and accuracy of exercise stress echocardiography in the non-invasive diagnosis of coronary heart disease

BACKGROUND

Exercise stress echocardiography (ESE) is a more recent form of totally non-invasive stress testing which like exercise thallium SPECT scintigraphy (ETS) was developed to overcome the known limitations of ECG stress testing, namely the limited diagnostic accuracy and the inability of ECG stress testing to site the region of coronary artery disease (CAD) induced ischaemia.

AIMS

To determine the sensitivity and specificity (and overall accuracy) of ESE in a group of patients referred for ETS imaging and compare the relative costs of each technique.

METHODS

One hundred and fifteen patients referred for ETS consented to a simultaneous ESE. Of this group, 59 patients underwent coronary angiography which was utilised as the gold standard.

RESULTS

The feasibility of ESE was 97% (112 of 115 patients of the total study population and 57 of the 59 patients who underwent coronary angiography). Of the 59 patients undergoing coronary angiography, the sensitivity of ESE and ETS were not significantly different (84.1% versus 91.3% respectively). However, despite the apparent marked difference in specificity (92.3% versus 61.5% respectively), p = NS (Fisher's exact test) as there were only 13 normals in the group who underwent coronary angiography. Overall accuracy was also closely similar (86.0% versus 84.7% respectively) and therefore also not significantly different. By contrast, agreement with coronary angiography as measured by the kappa statistic (kappa +/- SEk) was good for ESE (0.66 +/- 0.11) but only moderate for ETS (0.54 +/- 0.13). Moreover, there was a cost saving of at least $594.00 per patient in favour of ESE.

CONCLUSION

ESE is a totally non-invasive, sensitive, specific and cost-effective imaging modality for the detection and localisation of CAD.

Pacing stress echocardiography: an alternative to pharmacologic stress testing

OBJECTIVES

We sought to evaluate the diagnostic accuracy and feasibility of bedside pacing stress echocardiography (PASE) as a potential substitute for pharmacologic stress echocardiography in patients admitted to the hospital with new-onset chest pain or worsening angina pectoris.

BACKGROUND

Accurate and rapid noninvasive identification and evaluation of the extent of coronary artery disease (CAD) is essential for optimal management of these patients.

METHODS

Bedside transthoracic stress echocardiography was performed in 54 consecutive patients admitted to a community hospital with new-onset chest pain, after acute myocardial infarction had been excluded. We used 10F transesophageal pacing catheters and a rapid and modified pacing protocol. The PASE results were validated in all patients by coronary angiography performed within 24 h of the test. Significant CAD was defined as > or =75% stenosis in at least one major epicardial coronary artery.

RESULTS

The sensitivity of PASE for identifying patients with significant CAD was 95%, specificity was 87% and accuracy was 92%. The extent of significant CAD (single- or multivessel disease) was highly concordant with coronary angiography (kappa = 0.73, p<0.001). Pacing stress echocardiography was well tolerated, and only 4% of the patients had minor adverse events. The mean rate-pressure product at peak pacing was 22,313+/-5,357 beats/min per mm Hg, and heart rate >85% of the age-predicted target was achieved in 94% of patients. The average duration of the bedside PASE test, including image interpretation, was 38+/-6 min.

CONCLUSIONS

Bedside PASE is rapid, tolerable and accurate for identification of significant CAD in patients admitted to the hospital with new-onset chest pain or worsening angina pectoris.

Diagnostic and prognostic use of stress echocardiography in stable patients

Stress echocardiography is an effective diagnostic and prognostic technique in stable patients with known or suspected coronary artery disease (CAD), myocardial infarction, or chronic left ventricular dysfunction and those undergoing noncardiac surgery. Stress echocardiography is sensitive and specific for the detection and extent of CAD. Negative tests confer a high negative predictive value for cardiac events regardless of the clinical risk. Positive studies confer a high positive predictive value for ischemic events in patients with intermediate to high clinical risk. Stress echocardiography provides incremental prognostic information relative to clinical, resting echocardiographic, and angiographic data. Meta-analysis studies have shown that the diagnostic and prognostic information provided by stress echocardiography is comparable to that from radionuclide scintigraphic stress tests. Stress echocardiography may be more specific for the detection and extent of CAD, whereas radionuclide scintigraphy may be more sensitive for one-vessel disease. Sensitivities are similar for the detection and extent of disease in patients with multivessel CAD.

Accuracy of exercise echocardiography to detect coronary artery disease in left bundle branch block unassociated with either acute or healed myocardial infarction

To search for the value of treadmill exercise echocardiography in the detection of coronary artery disease in noninfarcted patients with left bundle branch block, we studied 35 patients (17 with coronary artery disease). We found high sensitivity, specificity, and accuracy (76%, 83%, and 80%, respectively).

A perspective on standardizing the predictive power of noninvasive cardiovascular tests by likelihood ratio computation: 2. Clinical applications

Likelihood ratio measures may be used as a standard for expressing the predictive power of noninvasive cardiovascular tests, calculated from sensitivity and specificity measures or as ratios of the predictive value odds to pretest odds for positive and negative test results. The positive likelihood ratio, (+)LR, expresses the power of a positive test result to augment an estimate of disease probability independent of the pretest prevalence of disease in a given population; the negative likelihood ratio, (-)LR, expresses the power of a negative test result to augment an estimate of the probability of no disease independent of the pretest prevalence of no disease in the same population. The likelihood ratio principle is applicable to the evaluation of the predictive power of single or combined test results reported for either dichotomous or continuous end points. This part of the perspective exemplifies application of the likelihood ratio principle in a wide variety of testing conditions for coronary artery disease followed by a discussion of the limitations of likelihood ratio computation in test power evaluation. Likelihood ratios provide a more concise and unambiguous standard for calibrating the predictive power of single and combined noninvasive cardiovascular test results than are provided by measures of sensitivity, specificity, and predictive value.

Diagnostic and Prognostic Use of Stress Echocardiography and Radionuclide Scintigraphy

Stress echocardiography and radionuclide scintigraphy are effective diagnostic and prognostic techniques in patients with known or suspected coronary artery disease (CAD), myocardial infarction (MI), chronic left ventricular dysfunction (LVD), and those undergoing noncardiac surgery. Both are sensitive and specific for the detection and extent of CAD. Negative tests confer a high negative predictive value for cardiac events irrespective of clinical risk. Positive studies confer a high positive predictive value for ischemic events in patients with intermediate to high clinical risk. Both provide incremental diagnostic and prognostic information relative to clinical, resting echocardiographic, and angiographic data. Meta-analysis studies have shown that the diagnostic and prognostic information provided by stress echocardiography is comparable with radionuclide scintigraphic stress tests. Stress echocardiography may be more specific for the detection and extent of CAD, whereas radionuclide scintigraphy may be more sensitive for single-vessel disease. Sensitivities are similar for the detection and extent of disease in patients with multivessel CAD.

Advances in Exercise Echocardiography Can This Technique Still Thrive in the Era of Pharmacologic Stress Testing?

In the current literature, pharmacologic stress techniques are the focus of interest and excitement regarding new technologies and new indications such as the diagnosis of viable myocardium. In contrast, exercise echocardiography has evolved less and is less amenable to the introduction of new technologies. This article reviews the indications for exercise echocardiography (especially in contrast to pharmacologic stress), its accuracy relative to other testing, and application to clinical decision making. Exercise echocardiography remains to be well accepted as a diagnostic and risk-assessment technique, and in some clinical situations it provides valuable data that are not available during pharmacologic stress testing.

Objective evaluation of regional left ventricular wall motion during dobutamine stress echocardiographic studies using segmental analysis of color kinesis images

OBJECTIVES

To test the feasibility of objective and automated evaluation of echocardiographic stress tests, we studied the ability of segmental analysis of color kinesis (CK) images to detect dobutamine-induced wall motion abnormalities and compared this technique with inexperienced reviewers of conventional gray-scale images.

BACKGROUND

Conventional interpretation of stress echocardiographic studies is subjective and experience dependent.

METHODS

CK images were obtained in 89 of 104 consecutive patients undergoing clinical dobutamine stress studies and were analyzed using custom software to calculate regional fractional area change in 22 segments in four standard views. Each patient's data obtained at rest was used as a control for automated detection of dobutamine-induced wall motion abnormalities. Independently, studies were reviewed without CK overlays by two inexperienced readers who classified each segment's response to dobutamine. A consensus reading of two experienced reviewers was used as the gold standard for comparisons. In a subgroup of 16 patients, these consensus readings and CK detection of wall motion abnormalities were compared with coronary angiography.

RESULTS

The consensus reading detected ischemic response to dobutamine in 43 of 1958 segments in 23 of 89 patients. Automated detection of stress-induced wall motion abnormalities correlated more closely with the standard technique than the inexperienced reviewers (sensitivity 0.76 vs. 0.55, specificity 0.98 vs. 0.94 and accuracy 0.97 vs. 0.92). When compared with coronary angiography in a subgroup of patients, analysis of CK images differentiated between normal and abnormal wall motion more accurately than expert readers of gray-scale images (accuracy of 0.93 vs. 0.82).

CONCLUSIONS

Analysis of CK images allows fast, objective and automated evaluation of regional wall motion, sensitive enough for clinical dobutamine stress data and more accurate than inexperienced readers. This method may result in a valuable adjunct to conventional visual interpretation of dobutamine stress echocardiography.

The evolution of stress echocardiography

The feasibility of using echocardiography to identify stress induced wall motion abnormalities was first demonstrated with M-mode recordings. The practical use of such a test had to await the development of 2-dimensional echocardiography whereby more wall segments could be analyzed. From the early days of 2-dimensional echocardiography there have been a succession of technological and clinical advances which have made stress echocardiography a very clinically useful tool in the management of patients with known or suspected coronary artery disease. These developments included the realization that stress-induced wall motion abnormalities produce stunned myocardium permitting immediate posttreadmill echoes to be clinically useful, the use of pharmacologic stress, the introduction of digital recording techniques so that rest and stress images could be viewed side-by-side, and more recently the advent of new imaging technologies, such as harmonic imaging of tissue to provide higher quality of stress echocardiograms.

Assessment of flow mismatch with pharmacologic stress test on myocardial contrast echocardiography in a model of critical stenosis: adenosine triphosphate and dipyridamole

Although adenosine triphosphate (ATP) is a favorable vasodilator because of its short-acting duration, the agent's effectiveness in facilitating the diagnosis of myocardial ischemia with myocardial contrast echocardiography (MCE) is not fully understood. The goal of this study was to examine the efficacy of intravenous ATP administration (0.15 to 0.30 mg/kg/min for 5 minutes) in diagnosing the flow mismatch with MCE. To achieve this, a critical stenosis was produced in the left circumflex artery in 10 anesthetized dogs. The peak intensity ratio of risk area to control area was reduced by ATP from 0.51 +/- 0.19 to 0.31 +/- 0.12 (P <.05). Systolic wall thickening of the risk area did not change significantly (32.8% +/- 9.8% to 27.5% +/- 12.8%). These changes did not differ from those obtained after dipyridamole. We conclude that MCE with intravenous ATP administration is as useful as the dipyridamole method for diagnosing critical coronary stenosis.

Impact of Age on the Safety and the Hemodynamic Response Pattern During High Dose Dobutamine Echocardiography

BACKGROUND: The purpose of the present study was to assess the safety and hemodynamic response of high dose dobutamine echocardiography (DE) in different age groups. DE is frequently used in the diagnosis of coronary artery disease; its safety in very elderly patients is not established, and there are no standards for blood pressure and heart rate response. METHODS AND RESULTS: The test was performed using up to 50 µg/kg/min in 400 patients: 164 middle-aged (age < 65 years), 187 elderly (age, 65-79 years), and 49 very elderly (age >/= 80 years). It was stopped because of side effects in 91 (23%) patients. Serious side effects occurred in 1.5% of the patients. There was a significant (60% +/- 35%) increase in heart rate, and a modest (10% +/- 19%) increase in the blood pressure (P <.001). The change in heart rate was similar in the three age groups, but there was a blunting of the blood pressure response with age. Hypotension was related to ischemia only in the very old. CONCLUSIONS: High-dose dobutamine is safe in all age groups. Dobutamine induces mainly a chronotropic and less a hypertensive response. The chronotropic response of the very old is similar with that of younger patients, but the hypertensive response is blunted in this group.

Risk stratification of patients with medically treated unstable angina using exercise echocardiography

Functional testing is recommended for risk stratification of medically treated patients with unstable angina. Exercise echocardiography is used in this situation, but its safety and prognostic value are not well defined. The objective of this study was to assess the incremental prognostic value of exercise echocardiography in 226 consecutive patients (128 men, age 59+/-13 years) with medically treated unstable angina, who underwent exercise echocardiography from 1991 to 1996. Clinical risk was designated as low in 108 patients, intermediate in 116, and high in 2 patients according to the unstable angina practice guidelines. There were no major complications from the stress tests. The exercise electrocardiogram was nondiagnostic in 57 patients (25%). Ischemia was identified by exercise electrocardiography in 33 patients and exercise echocardiography in 55 patients. Patients were followed for 29+/-18 months. After exclusion of 38 patients who underwent early revascularization, 28 patients had cardiac death, nonfatal infarction, and late (>3 months) revascularization. Ischemia at exercise echocardiography was associated with a 24-month event-free survival of 81%, compared to 95% with negative exercise echocardiography (p=0.02). A positive exercise electrocardiogram was associated with a 24-month event-free survival of 84%, compared to 93% with negative exercise electrocardiograms (p=0.08). In a Cox regression model, event-free survival was predicted by ischemia at exercise echocardiography (relative risk 2.8, confidence interval: 1.3 to 6.3, p=0.05), but not at exercise electrocardiography (relative risk 2.1, confidence interval 0.7 to 5.8, p=0.16).

Clinical application of exercise stress echocardiography: supine bicycle or treadmill?

Although exercise stress echocardiography is currently used to evaluate coronary artery disease (CAD) patients, the best exercise methodology is still undefined. The objectives of the study were: (1) to compare supine bicycle stress echocardiography (SBSE) and treadmill in the evaluation of CAD; and (2) to define, in normal subjects, the different behavior of factors determining MVO2 with treadmill and SBSE. We selected 10 male patients with CAD (group A), and 10 male control subjects (group B). Each patient underwent SBSE and treadmill testing in random order. We studied heart rate, systolic blood pressure, heart rate x systolic blood pressure, and end-diastolic and end-systolic volume indexes. In group A, we also studied wall motion score index (according to the American Society of Echocardiography) and in group B, systolic blood pressure/end-systolic volume index. The results were as follows: Group A: SBSE resulted in significantly lower work load, heart rate, and significantly higher systolic blood pressure, heart rate x systolic blood pressure, end-diastolic volume index, end-systolic volume index, and wall motion score index. SBSE showed wall motion abnormalities in each patient, whereas treadmill did not detect wall motion abnormalities in 4 patients (3 single-vessel; 1 multivessel); of the other 6 patients, 2 showed a lower wall motion score index and 4 did not show any difference in left ventricle kinetics with the 2 methodologies of exercise. Mean acquisition time for postexercise images was 72 +/- 6 seconds. Group B: SBSE resulted in lower work load, heart rate, heart rate x systolic blood pressure, systolic blood pressure/end-systolic volume index, and higher end-diastolic volume index and end-systolic volume index. Systolic blood pressure was similar with SBSE and treadmill testing. In conclusion, our experience suggests SBSE is a highly accurate diagnostic tool for evaluating CAD compared with treadmill testing; the maximum cardiovascular performance can be achieved with lower values of heart rate, suggesting the echo test is more feasible. Treadmill testing could lose important information about the existence, extension, and location of CAD; in contrast, SBSE detects even small, quickly reversible wall motion abnormalities.

Stress echocardiography: recommendations for performance and interpretation of stress echocardiography. Stress Echocardiography Task Force of the Nomenclature and Standards Committee of the American Society of Echocardiography

Cardiovascular stress testing remains the mainstay of provocative evaluation for patients with known or suspected coronary artery disease. Stress echocardiography has become a valuable means of cardiovascular stress testing. It plays a crucial role in the initial detection of coronary disease, in determining prognosis, and in therapeutic decision making. The purpose of this document is to outline the recommended methodology for stress echocardiography with respect to personnel and equipment as well as the clinical use of this recently developed technique. Specific limitations will also be discussed.

Reproducibility of stress echocardiography using intravenous injection of ultrasound contrast agent (BY 963)

Despite the widespread use of stress echocardiography, its reproducibility is still limited by high interobserver variability. Therefore, the purpose of the present study was to improve the reproducibility of a stress (exercise) echocardiography using a new transpulmonary ultrasound agent (BY 963). Stress echocardiography was performed in 12 healthy volunteers with suboptimal endocardial border delineation during exercise echocardiography. A special 45 degrees lateral tilted bike stress echocardiography table was used for exercise testing. Echocardiographic images were recorded on-line at rest and during exercise on a video tape and additionally digitized on-line on a stress echo computer. End-diastolic (EDVml), end-systolic (ESVml) volume and ejection fraction (EF%) were estimated in the 4-chamber view. The measurements were performed before and after injection of 2.5 ml and 5 ml BY963 at rest and in maximal exercise. A new contrast agent (BY 963) leads to a sufficient contrast effect for the left ventricular cavity after intravenous administration and permits a good delineation of left the endocardial border. The interobserver variability was determined using blinded investigation by two observers. The correlation of EDV and ESV determination at rest was r = 0.68/0.33, after 2.5 ml BY 963 r = 0.97/0.93 and after 5 ml BY 963 r = 0.90/0.93. The correlation for EDV and ESV during exercise was r = 0.52/0.33, after 2.5 ml BY 963 r = 0.88/0.80 and after 5 ml BY 963 r = 0.95/0.92. At rest mean EF without contrast was 61 +/- 6%/67 +/- 7% (r = 0. 130), after 2.5 ml BY 963 i.v. 69 +/- 8%/72 +/- 7% (r = 0.82) and after 5 ml BY 963 i.v. 73 +/- 8%/73 +/- 8% (r = 0.98%) respectively. In exercise, mean EF without contrast was 68 +/- 8%/70 +/- 6 (r = 0.013), after 2.5 ml BY 963 83 +/- 6%/81 +/- 5 and after 5 ml 83 +/- 4%/82 +/- 3 (r = 0.86).

SUMMARY

The estimation of the end-systolic volume in exercise will be improved significantly and the estimated EF values will be higher compared to EF values obtained without contrast application. Transpulmonary contrast echocardiography for analysis of left ventricular volumes and ejection fraction can be routinely used in stress echocardiography. Intravenous administration of BY 963 improves the reproducibility of quantitative analysis of left ventricular function in healthy volunteers. Further studies in patients with cardiac diseases are required to corroborate this observation.

The Five View Technique for Stress Echocardiography: A Description and Evaluation of Segmental Imaging and Reported Angiographic Data

Stress echocardiography is an accurate means of evaluating ischemic heart disease with sensitivities and specificities equivalent to alternate modalities. The sensitivities to disease of vessels with posterior wall distribution are, however, significantly lower. Studies establishing these figures have used a 4 view digital imaging technique as standard. This study aimed to determine if the use of a 5 view template (4 views plus an apical 3 chamber (3ch) view) significantly improved stress echo results. One hundred consecutive stress echocardiograms using a 5 view format were analyzed by two independent observers. Nine thousand regional wall segments were graded quantitatively and qualitatively and comparisons were made between the 4 and 5 view techniques. Reported angiographic sensitivities of the two techniques were analyzed and compared to the segmental imaging data. The 5 view template was found to increase overall segmental imaging by 30% and imaging of lateral and posterior walls was increased by 50% while the additional poststress cycle was acquired in under 13 seconds. Five view studies reported increased mean sensitivities to left anterior descending coronary artery (LAD) disease of 29.7%, right coronary artery (RCA) disease of 25.7%, and circumflex coronary artery (Cx) disease of 51.6%. This study found that the 5 view technique significantly increased left ventricular segmental imaging, particularly of the posterior and lateral walls, and is associated with increased angiographically determined sensitivity, particularly for vessels with posterior wall distribution when compared to the 4 view technique.

Comparison of arbutamine and exercise echocardiography in diagnosing myocardial ischemia

Arbutamine is a new catecholamine designed for use as a pharmacologic stress agent. This study compared the sensitivity of arbutamine with symptom-limited exercise to induce echocardiographic signs of ischemia. Arbutamine was administered by a computerized closed-loop delivery system that controls the infusion rate of arbutamine toward a predefined rate of heart rate increase and maximum heart rate limit. Beta blockers were stopped > or = 48 hours before both tests. Stress was stopped for intolerable symptoms, or clinical, electrocardiographic or echocardiographic signs of ischemia (new or worsening wall motion abnormality), target heart rate (> or = 85% age predicted maximum heart rate), or plateau of heart rate response. Thirty-seven patients were entered into the study (35 arbutamine and exercise, 1 arbutamine only, 1 exercise only), of which 30 had angiographic evidence of coronary artery disease (> or = 50% lumen diameter narrowing). Rate-pressure product increased significantly in response to both stress modalities (p < 0.001) and was significantly greater with exercise (11,308 +/- 2,443) than with arbutamine (9,486 +/- 2,479, p < 0.001). The time to maximum heart rate was longer during arbutamine stress echocardiography than during exercise testing (17.3 +/- 9.4 versus 9.3 +/- 4.2 minutes, respectively, p < 0.001). There were more patients with interpretable echo data for arbutamine (82%) than for exercise (67%). Sensitivity for recognition of myocardial ischemia was 94% (95% confidence interval 70% to 100%) and 88% (95% confidence interval 62% to 98%), respectively. The most frequent adverse events during arbutamine (n = 36) were dyspnea (5.6%) and tremor (5.6%). Two arbutamine stress tests were discontinued due to arrhythmias: 1 patient had premature atrial and ventricular beats, and the other had premature atrial contractions and atrial fibrillation. Arrhythmias were well tolerated and resolved without sequelae. In conclusion, the sensitivity of arbutamine to induce echocardiographic signs of ischemia was similar to that of exercise despite a lower rate-pressure product. Arbutamine was well tolerated and provides a reliable alternative to exercise echocardiography.

Technical Issues Related to Digital Stress Echocardiography Analysis and Acquisition Stations

Digital acquisition and display of echocardiographic images has facilitated the development of stress echocardiography. This review will outline technical issues involved with digital capture and manipulation of echocardiographic data, referring to currently available commercial equipment. Among the acquisition items to be discussed are the source of the digitized data (direct digital transfer from the echo machine vs video capture); image resolution (spatial and temporal spacing of the digitized data); and EKG triggering options (direct triggering of the QRS complex vs detecting the QRS on the video transfer). During playback, rest and stress images may be displayed at different frame rates, so that systole will occupy approximately the same time interval. Currently available commercial systems are compared with regard to these features, as well as hardware architecture and operating system.

Supine Bicycle Exercise Echocardiography: A Potent Immediately Available Tool for Detection and Localization of Myocardial Ischemia for the Initial Cardiologist

BACKGROUND: Exercise echocardiography (EE) is being used increasingly as an investigative technique now that dynamic images can be captured digitally. Its equivalent reliability with scintigraphic methods has been demonstrated in a hospital setting. This study analyzes its impact on daily practice. MATERIALS AND METHODS: Standardized progressive stress was produced by supine bicycle ergometry. Echocardiographic images of complete cardiac cycles were obtained in standard apical and parasternal short-axis views before, during, and after maximum effort, and digitized for simultaneous analysis of synchronized images at rest and during exercise. Two hundred sixteen patients (175 men and 41 women; mean age 58 +/- 10 years) were studied. RESULTS: Image quality was suboptimal in 4 cases. In the remaining 212 cases, ischemia was detected in 91 cases, and the test was negative in 114 cases and doubtful in 7 cases. Control by selective coronary angiography, as indicated by the clinical situation, was performed in 52 cases. In this particular group, EE showed 87% sensitivity, which is significantly higher than the 59% recorded for conventional exercise testing (P < 0.0001). CONCLUSIONS: EE by bicycle ergometer in the supine position is a valid, noninvasive investigative technique that can be used in an outpatient situation (feasibility 95%) since it is readily available. Its value appears to be greatest in cases in which exercise ECG is not conclusive. A negative result enables the initial cardiologist to reassure the patient immediately, which has been demonstrated in the literature to have favorable prognostic value. (ECHOCARDIOGRAPHY, Volume 13, May 1996)

Cardiovascular stress testing: a description of the various types of stress tests and indications for their use

OBJECTIVE

To describe the various types of stress tests and to provide guidelines for selecting a specific test for an individual patient.

MATERIAL AND METHODS

Myocardial perfusion imaging, radionuclide angiography, stress echocardiography, and cardiopulmonary exercise testing are described. The advantages and limitations of these techniques are reviewed and compared with those of standard treadmill exercise testing. The agents used for pharmacologic stress testing are discussed.

RESULTS

Standard treadmill exercise testing is widely available and is less expensive than the imaging techniques. It is most accurate in patients with normal findings on a resting electrocardiogram who are not taking digoxin. In these patients, standard exercise electrocardiography is almost as accurate as the exercise imaging modalities for identifying those with left main or three-vessel coronary artery disease. Advantages of the stress imaging modalities in comparison with standard exercise electrocardiography include greater accuracy when the resting electrocardiogram shows abnormal findings, higher sensitivity, ability to localize and characterize the extent of myocardial ischemia, and direct measurement of other variables such as left ventricular function. These techniques must be performed carefully in experienced laboratories in order to provide accurate information. Published data are scant that directly compare one technique with another in the same set of patients. The nuclear cardiology techniques have been well validated for detecting left main and three-vessel coronary artery disease and for assessing prognosis. Myocardial perfusion imaging has been well validated for detecting ischemia in patients with abnormal left ventricular function at rest. In comparison with the nuclear cardiology techniques, stress echocardiography is less expensive and provides more ancillary information but has not been as well validated for assessment of severe coronary artery disease or prognosis. Cardiopulmonary exercise testing can be useful in selecting patients for cardiac transplantation and in assessing exertional dyspnea in selected patients. The most common application of pharmacologic stress testing is preoperative risk assessment of patients undergoing noncardiac operations. Pharmacologic stress testing should usually be reversed for patients who are unable to exercise adequately.

CONCLUSION

Most patients with normal findings on a resting electrocardiogram who are not taking digoxin should undergo standard treadmill exercise testing for diagnostic and prognostic purposes. Most patients with abnormal findings on a resting electrocardiogram should undergo one of the stress imaging techniques. Selecting a specific stress imaging techniques. should depend primarily on local expertise with the various techniques and secondarily on the strengths and limitations of the techniques as they relate to the individual patient.

Arbutamine echocardiography: efficacy and safety of a new pharmacologic stress agent to induce myocardial ischemia and detect coronary artery disease. The International Arbutamine Study Group

OBJECTIVES

This study sought to determine the efficacy and safety of arbutamine echocardiography in inducing myocardial ischemia and detecting coronary artery disease.

BACKGROUND

Exercise and pharmacologic stress echocardiography are clinically accepted techniques for detecting coronary artery disease. Arbutamine is a new synthetic beta-adrenoceptor agonist developed specifically as a stress agent. Arbutamine is delivered by a new computerized drug delivery device that adjusts the rate of drug infusion according to the patient's heart rate response during stress testing.

METHODS

The sensitivity of arbutamine echocardiography was determined in 143 patients who had coronary artery disease documented by coronary angiography. A subset of these patients (n = 114) also underwent exercise echocardiography. The specificity, or normalcy, of arbutamine echocardiography was determined in 54 patients considered to have a low likelihood of coronary artery disease.

RESULTS

Among those patients who had both stress test results, the incidence of inducing myocardial ischemia (new or worsening wall motion abnormalities) was 79% (95% confidence interval [CI] 69% to 86%, n = 98) for arbutamine and 77% (95% CI 67% to 85%, n = 98) for exercise echocardiography. The sensitivity of detecting coronary artery disease (ischemia or rest wall motion abnormality) was 87% (95% CI 79% to 93%, n = 101) for arbutamine and 83% (95% CI 74% to 90%, n = 101) for exercise echocardiography. The specificity (normalcy) of arbutamine echocardiogrpahy was 96% (95% CI 87% to 100%, n = 52). Arbutamine was well tolerated, and there were no serious adverse events.

CONCLUSIONS

Arbutamine echocardiography is an effective and safe pharmacologic stress test technique for diagnosing or excluding the presence of coronary artery disease. The ability of arbutamine stress to induce myocardial ischemia, detectable by echocardiography, was comparable to that for exercise.

Safety and efficacy of computerized closed-loop delivery of arbutamine: a new pharmacologic myocardial stress modality for the assessment of coronary artery disease. The European Arbutamine Study Group

This study evaluated the efficacy of computer-controlled closed-loop delivery of a new synthetic catecholamine, arbutamine, when given to induce myocardial ischemia detected by electrocardiography and echocardiography with a high (10 beats/min/min) and low (6 beats/min/min) rate of increase in heart rate (heart rate slope) in 70 patients with coronary artery disease. The electrocardiographic sensitivity for the detection of myocardial ischemia was 52% for the low slope and 51% for the high slope. The corresponding figures for echocardiographic sensitivity were 83% and 79% for the low and high slopes, respectively. There were no significant differences in changes from baseline to maximum in pharmacodynamic variables, although the mean times to reach maximum heart rate and systolic blood pressure were 1.4 minutes shorter (p = 0.001) and 3.7 minutes shorter (p < 0.05), respectively, for the high-slope regimen. The duration of the infusion was shorter (p < 0.001) for the high slope. In this study, closed-loop arbutamine administration was effective and safe in the detection of coronary artery disease for both heart rate slope regimens.