Stress echocardiography. Part I. Exercise echocardiography: techniques, implementation, clinical applications, and correlations

Ischemia With Nonobstructive Coronary Arteries: Insights From the ISCHEMIA Trial

BACKGROUND

Ischemia with nonobstructive coronary arteries (INOCA) is common clinically, particularly among women, but its prevalence among patients with at least moderate ischemia and the relationship between ischemia severity and non-obstructive atherosclerosis severity are unknown.

OBJECTIVES

The authors investigated predictors of INOCA in enrolled, nonrandomized participants in ISCHEMIA (International Study of Comparative Health Effectiveness with Medical and Invasive Approaches), sex differences, and the relationship between ischemia and atherosclerosis in patients with INOCA.

METHODS

Core laboratories independently reviewed screening noninvasive stress test results (nuclear imaging, echocardiography, magnetic resonance imaging or nonimaging exercise tolerance testing), and coronary computed tomography angiography (CCTA), blinded to results of the screening test. INOCA was defined as all stenoses <50% on CCTA in a patient with moderate or severe ischemia on stress testing. INOCA patients, who were excluded from randomization, were compared with randomized participants with ≥50% stenosis in ≥1 vessel and moderate or severe ischemia.

RESULTS

Among 3,612 participants with core laboratory-confirmed moderate or severe ischemia and interpretable CCTA, 476 (13%) had INOCA. Patients with INOCA were younger, were predominantly female, and had fewer atherosclerosis risk factors. For each stress testing modality, the extent of ischemia tended to be less among patients with INOCA, particularly with nuclear imaging. There was no significant relationship between severity of ischemia and extent or severity of nonobstructive atherosclerosis on CCTA. On multivariable analysis, female sex was independently associated with INOCA (odds ratio: 4.2 [95% CI: 3.4-5.2]).

CONCLUSIONS

Among participants enrolled in ISCHEMIA with core laboratory-confirmed moderate or severe ischemia, the prevalence of INOCA was 13%. Severity of ischemia was not associated with severity of nonobstructive atherosclerosis. (International Study of Comparative Health Effectiveness With Medical and Invasive Approaches [ISCHEMIA]; NCT01471522).

Doppler mitral inflow variables time course after treadmill stress echo with and without ischemic response

This study evaluated Doppler mitral inflow variables changes from rest to post-exercise among 104 subjects with and without echocardiographic evidence of ischemic response (IR) to exercise (63.9 ± 11 years, 54% male, 32% with IR) who underwent a clinically indicated treadmill stress echo (TSE) test. The time from exercise cessation to imaging (TIME) was recorded. The changes (after TSE minus baseline values) in the peak E-wave velocity (∆E) [34.2 vs. 24.2, p = 0.024] and E-wave deceleration rate (∆DR) [348.0 vs. 225.7, p = 0.010] were bigger in ischemic than in nonischemic subjects, while the changes in the peak A-wave velocity (∆A) did not differ [7.9 vs. 15.0, p = 0.082]. The correlations between Doppler variables and IR, TIME, and TIME × IR interaction were analyzed. We observed a significant interaction between TIME and IR regarding ∆E and ∆DR. The differences in the regression line slopes of time courses for ∆E and ∆DR based on IR were significant: ∆E (- 0.09 vs. - 8.17, p = 0.037) and ∆DR (11.23 vs. - 82.60, p = 0.022). Main findings: (1) Time courses after exercise of ∆E and ∆DR in subjects with and without IR were different. (2) ∆E and ∆DR did not differ between subjects with and without IR at exercise cessation (TIME = 0). (3) The simple main effect of ischemia on ∆E and ∆DR was significant at TIME of ≥ 3 min. Divergent time courses of ∆E and ∆DR after exercise might be promising for detecting diastolic dysfunction caused by ischemia. After the cessation of exercise, ΔE and ΔDR in nonischemic but not in ischemic subjects quickly tend to zero. The differences in ΔE and ΔDR between the two groups only became significant for TIME of ≥ 3 min. At the time of exercise cessation, the values of ΔE and ΔDR (taken from the regression lines) were not significantly different between the patients with and without IR. This divergent response is promising for detecting diastolic dysfunction caused by ischemia.

Exercise stress echocardiography: Where are we now?

Exercise stress echocardiography (ESE) is a widely used diagnostic test in cardiology departments. ESE is mainly used to study patients with coronary artery disease; however, it has increasingly been used in other clinical scenarios including valve pathology, congenital heart disease, hypertrophic and dilated cardiomyopathies, athlete evaluations, diastolic function evaluation, and pulmonary circulation study. In our laboratories, we use an established methodology in which cardiac function is evaluated while exercising on a treadmill. After completing the exercise regimen, patients remain in a standing position or lie down on the left lateral decubitus, depending on the clinical questions to be answered for further evaluation. This method increases the quality and quantity of information obtained. Here, we present the various methods of exercise stress echocardiography and our experience in many clinical arenas in detail. We also present alternatives to ESE that may be used and their advantages and disadvantages. We review recent advances in ESE and future directions for this established method in the study of cardiac patients and underline the advantage of using a diagnostic tool that is radiation-free.

Cannabis and Athletic Performance

Cannabis is widely used for both recreational and medicinal purposes on a global scale. There is accumulating interest in the use of cannabis and its constituents for athletic recovery, and in some instances, performance. Amidst speculation of potential beneficial applications, the effects of cannabis and its two most abundant constituents, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), remain largely un-investigated. The purpose of this review is to critically evaluate the literature describing the effects of whole cannabis, THC, and CBD, on athletic performance and recovery. While investigations of whole cannabis and THC have generally shown either null or detrimental effects on exercise performance in strength and aerobic-type activities, studies of sufficient rigor and validity to conclusively declare ergogenic or ergolytic potential in athletes are lacking. The ability of cannabis and THC to perturb cardiovascular homeostasis warrants further investigation regarding mechanisms by which performance may be affected across different exercise modalities and energetic demands. In contrast to cannabis and THC, CBD has largely been scrutinized for its potential to aid in recovery. The beneficial effects of CBD on sleep quality, pain, and mild traumatic brain injury may be of particular interest to certain athletes. However, research in each of these respective areas has yet to be thoroughly investigated in athletic populations. Elucidating the effects of whole cannabis, THC, and CBD is pertinent for both researchers and practitioners given the widespread use of these products, and their potential to interact with athletes' performance and recovery.

Immediate Stress Echocardiography for Low-Risk Chest Pain Patients in the Emergency Department: A Prospective Observational Cohort Study

BACKGROUND

Evaluation and disposition of low-risk chest pain (CP) patients in the emergency department (ED) is time consuming and expensive. Low-risk CP often results in hospital admission to rule out myocardial infarction, which leads to additional costs and delays.

OBJECTIVE

Our aim was to assess whether an immediate exercise stress echocardiogram (IESE) in the ED will allow safe, efficient, and cost-effective evaluation and discharge of patients with low-risk CP.

METHODS

Low-risk CP patients (TIMI [Thrombolysis in Myocardial Infarction] score 0-1) presenting to the ED with normal electrocardiogram, no history of coronary artery disease, and negative troponin T received IESE. We followed these patients for major adverse cardiac events and compared them to a control cohort of similar-risk patients admitted with traditional care at 1 and 6 months.

RESULTS

We enrolled 216 patients, 117 IESE and 109 control. We obtained follow-up at 1 and 6 months in 94% of the IESE group and 88% in the control group. There was no difference in diagnostic catheterization or percutaneous coronary intervention between the 2 groups (6.0% and 1.7% vs. 6.4% and 1.8%; p = 0.89). Median time from triage to discharge was significantly shorter with IESE (572.6 min vs. 1466.0 min), resulting in significantly lower cost ($4380.50 vs. $6191.70). There were no adverse events related to IESE or early discharge.

CONCLUSIONS

In our study, IESE for low-risk CP patients presenting to the ED has the potential to be equally safe, more expeditious, and more cost effective than admission to an observation unit.

Screening for asymptomatic coronary heart disease in the young 'at risk' population: Who and how?

Deaths due to coronary heart disease (CHD) remain high worldwide, despite recent achievements. An effective screening strategy may improve outcomes further if implemented in a high or ‘at risk’ cohort. Asymptomatic CHD in the young maybe underappreciated and applying an effective screening strategy to a young cohort may lead to improved outcomes due to significant socioeconomic impact from the consequences of CHD in this sub-group. A positive family history of CHD, which is known to be associated with an increased risk of future myocardial events, could aid in identifying the ‘at risk’ young cohort.

Traditional cardiovascular risk scoring systems are in wide use but lack the sensitivity or specificity required to estimate risk in an individual. Rather their use is limited to predicting population attributable risk. Functional studies such as exercise stress tests are readily available and cost effective but do not have the required sensitivity required to suggest their use as part of a screening protocol. Coronary CT angiography has been demonstrated to have high sensitivity for the detection of CHD and therefore may be suitable for screening purposes but there are concerns regarding radiation exposure.

Here we review the evidence for the use of potential screening strategies and the suitability of using such strategies to estimate risk of CHD in a young ‘at risk’ population.

Characteristics and outcomes of patients who achieve high workload (≥10 metabolic equivalents) during treadmill exercise echocardiography

OBJECTIVE

To determine the frequency and prognostic significance of abnormal exercise echocardiographic results for patients achieving a workload of 10 or more metabolic equivalents during treadmill exercise echocardiography.

PATIENTS AND METHODS

Patients who underwent treadmill exercise echocardiography from November 1, 2003, through December 31, 2008, and exercised for 9 or more minutes using the Bruce protocol (N=7236) were included. Clinical and exercise echocardiographic characteristics and outcomes were evaluated. Variables associated with abnormal exercise echocardiographic results and mortality were identified.

RESULTS

Exercise echocardiographic results were positive for ischemia in 862 patients (12%). Extensive ischemia developed in 265 patients (4%). For patients with normal exercise echocardiographic results, all-cause and cardiovascular mortality rates were 0.30% and 0.05% per person-year of follow-up, respectively. For patients who had extensive ischemia, all-cause and cardiovascular mortality rates were 0.84% and 0.25% per person-year of follow-up, respectively. Patients at highest risk were those who had extensive and severe regional wall motion abnormalities at rest (n=58), and their all-cause and cardiovascular mortality rates were 2.65% and 0.76% per person-year of follow-up. Exercise echocardiographic variables did not identify sizable patient subgroups at risk for death and did not provide incremental prognostic information (C statistic was 0.74 compared with 0.73 for the clinical plus exercise electrocardiography model).

CONCLUSION

Patients achieving a workload of 10 or more metabolic equivalents during treadmill exercise testing do not often have extensive ischemic abnormalities on exercise echocardiography. Although exercise echocardiographic results provide some prognostic information, it is not of incremental value for these patients, whose short-term and medium-term prognosis is excellent.

Clinical applications of exercise stress echocardiography in the treadmill with upright evaluation during and after exercise

Exercise stress echocardiography is the most frequently used stress test in our laboratory. Exercise echocardiography is used mainly in the study of patients with coronary artery disease. However, the technique is increasingly being used to study other diseases. In our centre, we use an original methodology, published by us in 2000, in which we evaluate heart function during exercise in the treadmill. After the exercise, patients are maintained in orthostatic position when appropriate or lying down in left lateral decubitus for further evaluation. Since this method seems to increase the quality and the quantity of information obtained in so many clinical arenas, we now present a detailed review of this methodology and its applications.

Improving prediction of outcomes in African Americans with normal stress echocardiograms using a risk scoring system

Cardiovascular mortality is high in African Americans, and those with normal results on stress echocardiography remain at increased risk. The aim of this study was to develop a risk scoring system to improve the prediction of cardiovascular events in African Americans with normal results on stress echocardiography. Clinical data and rest echocardiographic measurements were obtained in 548 consecutive African Americans with normal results on rest and stress echocardiography and ejection fractions ≥50%. Patients were followed for myocardial infarction and death for 3 years. Predictors of cardiovascular events were determined with Cox regression, and hazard ratios were used to determine the number of points in the risk score attributed to each independent predictor. During follow-up of 3 years, 47 patients (8.6%) had events. Five variables-age (≥45 years in men, ≥55 years in women), history of coronary disease, history of smoking, left ventricular hypertrophy, and exercise intolerance (<7 METs in men, <5 METs in women, or need for dobutamine stress)-were independent predictors of events. A risk score was derived for each patient (ranging from 0 to 8 risk points). The area under the curve for the risk score was 0.82 with the optimum cut-off risk score of 6. Among patients with risk scores ≥6, 30% had events, compared with 3% with risk score <6 (p <0.001). In conclusion, African Americans with normal results on stress echocardiography remain at significant risk for cardiovascular events. A risk score can be derived from clinical and echocardiographic variables, which can accurately distinguish high- and low-risk patients.

Patterns and predictors of stress testing modality after percutaneous coronary stenting: data from the NCDR(®)

OBJECTIVES

We evaluated temporal trends and geographic variation in choice of stress testing modality after percutaneous coronary intervention (PCI), as well as associations between modality and procedure use after testing.

BACKGROUND

Stress testing is frequently performed post-PCI, but the choices among available modalities (electrocardiography only, nuclear, or echocardiography; pharmacological or exercise stress) and consequences of such choices are not well characterized.

METHODS

CathPCI Registry(®) data were linked with identifiable Medicare claims to capture stress testing use between 60 and 365 days post-PCI and procedures within 90 days after testing. Testing rates and modality used were modeled on the basis of patient, procedure, and PCI facility factors, calendar quarter, and Census Divisions using Poisson and logistic regression. Post-test procedure use was assessed using Gray's test.

RESULTS

Among 284,971 patients, the overall stress testing rate after PCI was 53.1 per 100 person-years. Testing rates declined from 59.3 in quarter 1 (2006) to 47.1 in quarter 4 (2008), but the relative use of modalities changed little. Among exercise testing recipients, adjusted proportions receiving electrocardiography-only testing varied from 6.8% to 22.8% across Census Divisions; and among exercise testing recipients having an imaging test, the proportion receiving echocardiography (versus nuclear) varied from 9.4% to 34.1%. Post-test procedure use varied among modalities; exercise electrocardiography-only testing was associated with more subsequent stress testing (13.7% vs. 2.9%; p < 0.001), but less catheterization (7.4% vs. 14.1%; p < 0.001) than imaging-based tests.

CONCLUSIONS

Modest reductions in stress testing after PCI occurring between 2006 and 2008 cannot be ascribed to trends in use of any single modality. Additional research should assess whether this trend represents better patient selection for testing or administrative policies (e.g., restricted access for patients with legitimate testing needs). Geographic variation in utilization of stress modalities and differences in downstream procedure use among modalities suggest a need to identify optimal use of the different test modalities in individual patients.

Detection of prolonged regional myocardial systolic dysfunction after exercise-induced myocardial ischemia by strain echocardiography with high frame rate tissue Doppler echocardiography

BACKGROUND

Strain echocardiography has enabled quantification of regional myocardial systolic function objectively and is less influenced by tethering effects and cardiac translational artifact than Doppler tissue imaging. Although strain echocardiography has been applied for the detection of inducible ischemia during dobutamine stress, it has not been fully applied to exercise stress echocardiography (ESE) because of technical difficulties. Prolonged myocardial systolic dysfunction after exercise-induced ischemia has been shown previously. Thus, we designed this study to evaluate whether the myocardial strain analysis can detect myocardial ischemia by the assessment of prolonged regional left ventricular (LV) dysfunction in ESE.

METHODS

We performed ESE with myocardial strain imaging system in 20 consecutive patients who had exercise Tl-201 single photon emission computed tomography (SPECT). Myocardial strain curves were obtained at six segments in mid LV walls from the apical approach before and 5 min after ESE. We measured the duration from the R wave in the electrocardiogram to the timing of peak systolic strain corrected by the square root of the RR interval (TPSc). We finally calculated the differences of TPSc (ΔTPSc) before ESE and 5 min after ESE. The results were compared with SPECT as a reference standard.

RESULTS

A receiver operating characteristic curve demonstrated that a ΔTPSc cutoff value of 70 ms had a sensitivity of 80% and a specificity of 84% for the detection of myocardial ischemia.

CONCLUSIONS

Prolonged regional LV systolic dysfunction assessed by ESE with strain analysis was useful for the detection of myocardial ischemia.

Lack of correlation between noninvasive stress tests and invasive coronary vasomotor dysfunction in patients with nonobstructive coronary artery disease

BACKGROUND

Despite a nonobstructive coronary angiogram, many patients may still have an abnormal coronary vasomotor response to provocation and to myocardial demand during stress. The ability of noninvasive stress tests to predict coronary vasomotor dysfunction in patients with nonobstructive coronary artery disease is unknown.

METHODS AND RESULTS

All patients with nonobstructive coronary artery disease who had invasive coronary vasomotor assessment and a noninvasive stress test (exercise ECG, stress echocardiography, or stress nuclear imaging) within 6 months of the cardiac catheterization with provocation at our institution were identified (n=376). Coronary vasomotor dysfunction was defined as a percentage increase in coronary blood flow of <or=50% to intracoronary acetylcholine (endothelium-dependent dysfunction) and/or a coronary flow reserve ratio of <or=2.5 to intracoronary adenosine (endothelium-independent dysfunction). We determined the sensitivity and specificity of various noninvasive stress tests to predict coronary vasomotor dysfunction in these patients. On invasive testing, 233 patients (63%) had coronary vasomotor dysfunction, of which 187 patients (51%) had endothelium-dependent dysfunction, 109 patients (29%) had endothelium-independent dysfunction, and 63 patients (17%) had both. On noninvasive stress testing, 157 (42%) had a positive imaging study and 56 (15%) a positive ECG stress test. The noninvasive stress tests had limited diagnostic accuracy for predicting coronary vasomotor dysfunction (41% sensitivity [95% CI, 34 to 47] and 57% specificity [95% CI, 49 to 66]), endothelium-dependent dysfunction (41% sensitivity [95% CI, 34 to 49] and 58% specificity [95% CI, 50 to 65]), or endothelium-independent dysfunction (46% sensitivity [95% CI, 37 to 56] and 61% specificity [95% CI, 54 to 67]). The exercise ECG test was more specific but less sensitive than the imaging tests.

CONCLUSIONS

This study suggests that a negative noninvasive stress test does not rule out coronary vasomotor dysfunction in symptomatic patients with nonobstructive coronary artery disease. This underscores the need for invasive assessment or novel more sensitive noninvasive imaging for these patients.

Safety of Stress Echocardiography Supervised by Registered Nurses: Results of a 2-Year Audit of 15,404 Patients

BACKGROUND

Stress echocardiography has traditionally been performed under the supervision of physicians. In the last decade, at some institutions, specially trained registered nurses have taken on the task of directly supervising and conducting these stress tests with appropriate physician involvement and assistance.

METHODS

The safety of 15,404 stress echocardiograms that were performed under the direct supervision of registered nurses during a recent 2-year period was evaluated.

RESULTS

The stress modality was treadmill exercise in 8592 (56%), dobutamine in 6755 (44%), and transesophageal atrial pacing in 57 (0.04%) patients. The mean age was 65 +/- 13 years, and 54% were male. A total of 55 patients (0.36%) had complications related to stress echocardiography, including 26 patients (0.18%) who were subsequently transferred to hospital. Complications included atrial fibrillation (n = 28, 0.18%), other supraventricular tachycardias (n = 9, 0.06%), sustained ventricular tachycardia (n = 4, 0.03%), and ventricular fibrillation (n = 2, 0.01%). Eight patients (0.05%) were hospitalized for markedly positive tests or prolonged chest pain and 4 patients (0.03%) for symptomatic hypotension. No patient had cardiac rupture or died. Complications were more common with dobutamine stress echocardiography (DSE) (47/6755; 0.7%) compared with exercise echocardiography (8/8592; 0.09%) or transesophageal atrial pacing stress echocardiography (0/57) (P < .0001). Arrhythmias were more commonly associated with DSE (39/6755, 0.58%) than exercise echocardiography (4/8592, 0.05%). Potentially life-threatening ventricular arrhythmias occurred in 6 of 6755 patients who underwent DSE (0.09%) and in none of the patients who underwent exercise echocardiography. Patients who underwent DSE were, on average, older, and had more comorbidities compared with those who underwent exercise echocardiography.

CONCLUSIONS

Stress echocardiography, when supervised directly by specially trained registered nurses, can be performed safely; complications are uncommon (1/280 stress tests) and these complication rates are comparable with previously reported studies evaluating the safety of stress echocardiography supervised by physicians.

Influence of left ventricular filling pattern on exercise-induced changes of natriuretic peptides in patients with suspected coronary artery disease

BACKGROUND

Exertional change in brain natriuretic peptide (BNP) has recently been proposed as a biomarker of myocardial ischemia. However, in patients with abnormal left ventricular (LV) filling, BNP is frequently increased. Therefore, we studied the relationship of exertional changes in atrial and brain natriuretic peptides (ANP and BNP) with resting and exercise-induced changes of LV systolic function and filling pattern.

METHODS

LV function at rest and peak exercise was assessed in 140 patients (mean age 65 years, 78 men) during symptom-limited exercise echocardiography for evaluation of suspected coronary artery disease. ANP and BNP were measured at rest and 5 min after exercise.

RESULTS

ANP and BNP increased with exercise. The increase in BNP was significantly greater in the 65 patients with than in the 76 patients without ischemia [14.7 pg/ml (5.7-19.6) vs. 4.9 pg/ml (2.1-9.2), p<0.0001]; there was no difference in increase of ANP [340 pg/ml (176-729) vs. 424 pg/ml (249-648), p=0.54]. The exertional rise in BNP was also greater in patients with abnormal LV filling at rest [10.5 pg/ml (4.9-19.6) vs. 4.1 pg/ml (2.0-6.7), p<0.0001]. By multivariate linear regression, exertional change in wall motion score index (beta=0.23, p<0.001), baseline BNP (beta=0.71, p<0.001), abnormal LV filling pattern (beta=0.24, p<0.001) and age (beta=-0.15, p=0.02) were predictors of change in BNP.

CONCLUSIONS

In patients with suspected coronary artery disease, exertional changes of BNP are related not only to ischemia, but also to the LV filling pattern at rest.

Three-Dimensional Stress Testing: Volumetric Acquisitions

Two-dimensional stress echocardiography is an established technique for detecting the presence and severity of coronary artery disease. It also provides myocardial viability data, prognostic information, and risk stratification before major cardiovascular and noncardiac surgery. The current limitation of two-dimensional stress echocardiography includes the difficulty in obtaining the same imaging plane at rest and during stress, which may result in over- or underestimation of wall motion assessment, particularly in patients who have resting wall motion abnormalities. The accurate assessment of the extent and severity of stress-induced wall motion abnormalities is often difficult, and wall motion abnormalities may be missed by visual inspection of wall motion from the standard two-dimensional views. Recent technological development and engineering refinements have allowed the application of real-time three-dimensional (RT3D) echocardiography in the routine clinical setting. Because full-volume datasets obtained with RT3D echocardiography incorporate information on the entire left ventricle in four volumetric datasets, RT3D stress echocardiography has the potential to overcome many of the limitations encountered with two-dimensional stress echocardiography. Two different types of imaging modes, full-volume and multiplane mode, can be used to acquire and analyze stress echocardiography. Both modes have their particular benefits and limitations. This article reviews the literature describing the clinical utility of RT3D stress echocardiography, with particular emphasis on full-volume datasets.

New technologies applied to stress echocardiography: myocardial contrast echocardiography

The development of new echocardiographic contrast agents that can be injected intravenously and can opacify left-sided cardiac chambers has offered a contribution in the field of stress-echocardiography for two main reasons: (1) the improvement of visualization of the endocardial border and thus facilitating recognition of wall motion abnormalities during pharmacological stress or physical exercise; and (2) the obtaining of information on myocardial perfusion during stress examinations. This review will consider: (1) the improvement of diagnostic accuracy during pharmacological stress or physical exercise obtained with the administration of echo-contrast agents; (2) the results of major studies for comparison of the myocardial contrast echocardiography technique versus single-photon emission computed tomography (SPECT) and coronary angiography; (3) the added value for studying perfusion other than wall motion analysis during stress echo; and (4) the advantages and limitations of different stress modalities. New multicenter studies should now definitively clarify the choice of the best contrast agents and create protocols for myocardial contrast echocardiography using different methods of image acquisition in order to unify the diagnostic process before a 'label approved' for perfusion of contrast echocardiographic agents. Finally, caution should be considered when contrast agents are used in the acute phase of myocardial infarction or ischemia.

Safety of exercise stress testing in patients with abnormal concentrations of serum potassium

The objective of this study was to determine the safety of performing exercise stress testing in patients with abnormal serum potassium concentrations. Data were reviewed from 9,084 patients (mean age 63 +/- 12 years) referred for exercise echocardiography who had serum potassium measured <48 hours before the test were reviewed, and the occurrence of arrhythmias during stress testing was determined. Of 10,272 studies, 9,067 (88%) were in patients with normokalemia and 1,205 (12%) were in patients with abnormal serum potassium concentrations: 309 (26%) with hypokalemia (mean 3.4 +/- 0.16 mmol/L) and 896 (74%) with hyperkalemia (mean 5.1 +/- 0.19 mmol/L). Ventricular and supraventricular ectopy were common during exercise. Only 1 patient (potassium 4.9 mmol/L) had sustained ventricular tachycardia; all other episodes were nonsustained. Although ventricular and supraventricular ectopy are common during exercise testing, life-threatening arrhythmias are not. Exercise testing is generally safe despite mild to moderate hypokalemia or hyperkalemia.

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.

Left atrial systolic reserve in idiopathic vs. ischaemic-dilated cardiomyopathy

PURPOSE

There are studies indicating more pronounced left atrial (LA) systolic dysfunction at rest in idiopathic (IDDC) than in ischaemic-dilated cardiomyopathy (ISDC). It was hypothesized that the findings would be similar with regards LA systolic reserve.

METHODS

Twenty-six patients with IDDC, 28 with ISDC and 25 normal controls underwent low-dose dobutamine stress echocardiography (5-10 microg kg(-1) min(-1) IV). Left atrial volumes were echocardiographically determined at rest and during stress at the mitral valve opening (maximal, Vmax), electrocardiographic P wave (onset of atrial systole, Vp) and mitral valve closure (minimal, Vmin) from the apical 4- and 2-chamber views (biplane area-length method). Left atrial systolic function was assessed with the LA-active emptying volume (ACTEV) = Vp-Vmin and fraction (ACTEF) = ACTEV/Vp.

RESULTS

Vmax at rest was similar in IDDC and ISDC and greater than in the controls (54.2 +/- 12 vs. 48.5 +/- 18 vs. 27.1 +/- 6.3 cm(3) m(-2), respectively, P < 0.001) and did not change with stress (53.9 +/- 13.8 vs. 46.9 +/- 16.2 vs. 25.8 +/- 5.9 cm(3) m(-2), P < 0.001). The ACTEV at rest was similar in IDDC and ISDC and greater than in the controls (8.6 +/- 3.5 vs. 9.7 +/- 2.9 vs. 6.1 +/- 2.2 cm(3) m(-2) P < 0.01), whereas during the dobutamine infusion it remained unaltered in IDDC (10.8 +/- 4.6 cm(3) m(-2), P = NS vs. rest) and increased in ISDC (11.8 +/- 3.3 cm(3) m(-2), P < 0.05) and the controls (13.1 +/- 3.2 cm(3) m(-2), P < 0.01). The ACTEF was lower in IDDC than ISDC and the controls at rest (20 +/- 10% vs. 33 +/- 8% vs. 36 +/- 10%, P < 0.01). Dobutamine infusion was associated with no significant increase in ACTEF in IDDC (25 +/- 12%, P = NS vs. rest), and with an increase in this variable in ISDC (39 +/- 10%, P < 0.05) and the controls (49 +/- 12%, P < 0.01).

CONCLUSIONS

Dobutamine infusion is associated with an increase in LA ACTEV and fraction in ISDC and no significant change in these indices in IDDC. These findings indicate a reduced LA systolic reserve in IDDC.

Comparing stress testing methods. Available techniques and their use in CAD evaluation

Exercise stress testing remains one of the most widely used techniques in assessing functional capacity and in confirming a diagnosis of CAD. Its sensitivity and specificity are approximately 63% and 74%, respectively. The technique is safe when administered and supervised by qualified personnel who are trained to recognize contraindications and other reasons for termination of the test. More recently, echocardiography has been combined with exercise stress testing. It is a well-tolerated and valuable procedure for noninvasive evaluation of CAD. The sensitivity and specificity of stress echocardiography are higher than those of exercise stress testing and comparable to those of nuclear perfusion imaging. Continuing improvements in digital image analysis, cost, and the availability of contrast agents promise to make noninvasive stress testing even more useful in the years to come. Newer contrast and concomitant perfusion agents are on the horizon and may prove to be a reality in the echocardiographic laboratories of the future.

Outcomes of patients with reduced exercise capacity at time of exercise echocardiography

OBJECTIVE

To characterize the prognostic implications of exercise echocardiography in patients who have reduced exercise capacity at the time of testing.

PATIENTS AND METHODS

We examined the outcomes of 941 patients at the Mayo Clinic in Rochester, Minn, between January 1, 1990, and December 31, 1995, who had reduced exercise capacity on exercise echocardiography (women, <5 metabolic equivalents; men, <7 metabolic equivalents) and evaluated the potential association between clinical, electrocardiographic, and echocardiographic variables and outcomes for patients with normal vs abnormal exercise echocardiograms. We used variables of independent prognostic value to estimate cardiac risk.

RESULTS

For patients with normal exercise echocardiograms (n=282), the rate of cardiac death or nonfatal myocardial infarction was 09% per person-year of follow-up, and previous coronary revascularization was the only predictor of the time to cardiac event. For patients with abnormal exercise echocardiograms (n=659), the cardiac event rate was 4.4%. Independent predictors of outcome were exercise left ventricular (LV) ejection fraction (risk ratio, 1.44 per 10% decrement; 95% confidence interval, 1.2-1.7; P<.001) and an increase or no change in LV end-systolic size in response to exercise (risk ratio, 2.22; 95% confidence interval, 1.2-4.1; P=.01).

CONCLUSION

Exercise echocardiographic findings have important prognostic implications for patients who have reduced exercise capacity on testing. Echocardiographic descriptors of LV systolic function and dysfunction obtained immediately after exercise can be used to stratify cardiac risk of patients who do not achieve a level of exercise ordinarily considered to be of "diagnostic" value.

Exercise echocardiography reflects cumulative anthracycline exposure during childhood

BACKGROUND

Low and moderate dose anthracycline therapy used in current treatment protocols, may be associated with subclinical abnormalities of cardiac function and late presentation with congestive heart failure. Exercise echocardiography is a useful and non-invasive means of uncovering latent cardiac dysfunction in other settings. The purpose of this study is to determine whether exercise echocardiography has the potential to detect subclinical abnormalities of cardiac function in children treated with anthracyclines.

PROCEDURE

One hundred ten children previously treated with anthracycline, in remission and off treatment for >12 months were assessed, together with 31 control subjects. Each subject had a resting ECG and echocardiogram performed, and following exercise on a treadmill according to the Bruce protocol, a repeat echocardiogram was performed.

RESULTS

Cumulative anthracycline dose was the only patient variable related to any of the outcome measures. Resting fractional shortening was normal in the majority of treated patients but was inversely related to cumulative anthracycline dose (rate of decline 1.2%/100 mg/m(2)). Following peak exercise, the inverse relationship between fractional shortening and anthracycline dose was more pronounced (rate 2.7%/100 mg/m(2)).

CONCLUSIONS

Higher anthracycline doses are associated with a greater difference in peak fractional shortening between treated subjects and controls. Exercise echocardiography is a simple, relatively inexpensive tool that may enhance the detection of latent cardiac dysfunction after anthracycline administration during childhood.

akinesia becoming dyskinesia after exercise testing: prevalence and relationship to clinical outcome

OBJECTIVES

The aim of this study was to determine the prevalence and prognostic implications of dyskinesia developing after exercise.

BACKGROUND

The prevalence and prognostic implications of new-onset dyskinesia with exercise testing have not been previously described.

METHODS

We considered 1005 consecutive patients who underwent exercise echocardiography and had akinetic segments at rest. Patients were divided according to the presence or absence of exercise-induced dyskinesia. Baseline clinical and echocardiographic parameters were compared, and patients were followed up for a median of 2.7 years.

RESULTS

One hundred four (10%) patients developed dyskinesia after exercise. Compared to patients with segments that remained akinetic, these patients were more likely to have electrocardiographic (ECG) evidence of prior myocardial infarction and, during exercise, had a less pronounced rise in systolic blood pressure and more often had ECG evidence of ischemia. Their resting left ventricular (LV) ejection fraction was worse and improved little after exercise. However, all-cause mortality and the incidence of major adverse cardiac events were similar in the two groups, even after correction for age, gender, and resting LV function (hazard ratio for major adverse cardiac events = 1.36, 95% confidence interval [CI] 0.82 to 2.26, p = 0.23; hazard ratio for total mortality = 1.20, 95% CI 0.75 to 1.94, p = 0.45).

CONCLUSIONS

One in 10 patients with akinetic myocardium at rest will develop dyskinesia after exercise. This is associated with poorer LV function at rest and little improvement in systolic function after exercise. However, this response has no impact on prognosis.

Transitions: noninvasive coronary angiography using electron beam computed tomography: technique, clinical application, future prospective

Electron beam computed tomography has been available clinically for 20 years. It is the only computed tomography scanner specifically developed for cardiac imaging. Over the past decade, with improvements in methodology and computer software, electron beam computed tomography has been shown to provide an excellent method to perform noninvasive coronary angiography. This article looks at the historical aspects of electron beam computed tomography and comments on how to perform and interpret electron beam angiography studies. The expanding development of noninvasive coronary and peripheral angiography methods using computed tomography will have a significant influence on cardiovascular specialists and their practices.

Interpretation of Left Ventricular Wall Motion During Stress Testing

This article describes the obstacles to stress echocardiographic interpretation, and reviews the techniques currently available that offer a more objective approach to stress wall motion analysis than the conventional visual methodology. These techniques include Doppler-based methods, such as myocardial Doppler velocity and strain rate imaging, as well as automated border detection techniques, such as acoustic quantification and color kinesis.

Valvular flow abnormalities are often identified by a resting focused Doppler examination performed at the time of stress echocardiography

BACKGROUND

Patients are usually referred for stress echocardiography to assess whether there is inducible myocardial ischemia. At some centers, a focused Doppler examination is also performed. We sought to determine the clinical value of this additional study by examining how often valvular flow abnormalities were identified that might affect clinical care.

METHODS

We reviewed 1272 consecutive stress echocardiogram reports from a 1-year period, including 1223 tests that contained focused Doppler data. Important Doppler findings were defined as at least moderate mitral regurgitation, at least mild aortic regurgitation, any aortic or mitral valve stenosis, or any resting left ventricular outflow tract gradient.

RESULTS

Overall, focused Doppler identified an important Doppler abnormality in 214 patients (17%). At least moderate mitral regurgitation was identified in 67 patients (5%) and at least mild aortic regurgitation was identified in 163 patients (13%). In addition, aortic stenosis (n = 14; 1%), mitral stenosis (n = 5; 0.4%), and resting outflow tract gradient (n = 2; 0.2%) were noted. A prior echocardiogram had been performed at our institution in 317 patients (26%). For this subset, a new important Doppler finding, a two-step change in regurgitant grade, or a one-step change in stenosis severity was noted in 28 patients (9%). Among patients who had a previous study, the prevalence of new findings was the same (9%) in those who had been studied within the previous year as in those whose previous study had been performed more than 2 years before.

CONCLUSION

Focused Doppler documents valvular flow abnormalities in 17% of patients referred for stress echocardiography, thereby enhancing the potential overall value of the test. The frequency of new findings was independent of the time interval from the previous Doppler study. These data should be considered when clinicians choose a stress imaging modality.

Prognostic significance of the location of wall motion abnormalities during exercise echocardiography

OBJECTIVES

Our aim was to determine whether location of wall motion abnormalities (WMAs) during exercise echocardiography provides independent prognostic value.

BACKGROUND

The effect of the location of WMAs during stress echocardiography on prognostic outcome is unknown.

METHODS

We studied 4,347 patients (mean age, 61 +/- 12 years; 2,230 men) with known or suspected coronary artery disease by symptom-limited exercise echocardiography. An abnormal result was defined as resting or exercise-induced WMA. End points were cardiac death and nonfatal myocardial infarction (MI).

RESULTS

There were 133 cardiac events (54 cardiac deaths and 79 nonfatal MIs) during follow-up (median, three years). In a multiple-stepwise multivariate analysis model, clinical and exercise electrocardiography predictors of cardiac events were age, gender, hypertension, typical chest pain, previous MI, smoking, and resting ejection fraction. The percentage of ischemic segments at peak exercise provided additional information to the model (p = 0.0001). The presence of abnormalities in the left anterior descending (LAD) coronary artery distribution had an additional independent effect for the prediction of cardiac events (p = 0.001). Among patients with exercise echocardiographic abnormalities in a single vascular region, those with abnormalities in the left anterior descending coronary artery distribution had a higher event rate than patients with abnormalities elsewhere (3.2% vs. 2.1% at three years and 10.8% vs. 2.1% at five years; p = 0.009). CONCLUSIONS; Exercise WMAs in the distribution of the LAD coronary artery are associated with an increased risk of cardiac death and nonfatal MI. This risk is independent of the resting ejection fraction and the extent of WMAs during exercise.

Outcome after abnormal exercise echocardiography for patients with good exercise capacity: prognostic importance of the extent and severity of exercise-related left ventricular dysfunction

OBJECTIVES

We sought to define the prognostic implications of the extent and severity of exercise echocardiographic abnormalities in patients with good exercise capacity. BACKGROUND; The exercise capacity of patients with known or suspected coronary artery disease (CAD) is of prognostic importance, as is the extent of exercise-related left ventricular (LV) hypoperfusion or dysfunction.

METHODS

We examined the outcomes of 1,874 patients with known or suspected CAD (mean age 64 +/- 10 years, 64% men) who had good exercise capacity (> or = 5 metabolic equivalents [METs] for women, > or = 7 METs for men) but abnormal exercise echocardiograms and analyzed the potential association between clinical, exercise and echocardiographic variables and subsequent cardiac events.

RESULTS

Multivariate predictors of time to cardiac death or nonfatal myocardial infarction (MI) were diabetes mellitus (risk ratio [RR] 1.88; 95% confidence interval [CI] 1.2 to 3.0), history of MI (RR 2.44; 95% CI 1.6 to 3.6) and an increase or no change in LV end-systolic size in response to exercise (RR 1.61; 95% CI 1.1 to 2.5). Using echocardiographic variables that were of incremental prognostic value, we were able to stratify the cardiac risk of the study population; cardiac death or nonfatal MI rate per person-year of follow-up was 1.6% for patients who had a decrease in LV end-systolic size in response to exercise (n = 1,330) and 1.2% for patients who did not have any severely abnormal LV segments immediately after exercise (n = 868).

CONCLUSIONS

In patients with good exercise capacity, echocardiographic descriptors of the extent and severity of exercise-related LV dysfunction were of independent and incremental prognostic value. Stratification of patients into low- and higher risk subgroups was possible using these exercise echocardiographic characteristics.

Prognostic value of exercise echocardiography in 5,798 patients: is there a gender difference?

OBJECTIVES

This study was designed to determine the effect of gender on the prognostic value of exercise echocardiography.

BACKGROUND

Limited information exists regarding gender differences in prognostic value of exercise echocardiography.

METHODS

We obtained follow-up (3.2 +/- 1.7 years) in 5,798 consecutive patients who underwent exercise echocardiography for evaluation of known or suspected coronary artery disease.

RESULTS

There were 3,322 men (mean age 62 +/- 12 years) and 2,476 women (mean age 62 +/- 12 years) (p = 0.7). New or worsening wall motion abnormalities developed with exercise in 35% of men and 25% of women (p = 0.001). Cardiac events, including cardiac death (107 patients) and nonfatal myocardial infarction (148 patients), occurred in 5.3% of men and 3.1% of women (p = 0.001). Addition of the percentage of ischemic segments to the clinical and rest echocardiographic model provided incremental information in predicting cardiac events for both men (chi(2) = 137 to 143, p = 0.014) and women (chi(2) = 72 to 76, p = 0.046). By multivariate analysis, exercise electrocardiographic and exercise echocardiographic predictors of cardiac events in both men and women were workload and exercise wall motion score index. There was no significant interaction effect of rest echocardiography (p = 0.79), exercise electrocardiography (p = 0.38) or exercise echocardiography (p = 0.67) with gender.

CONCLUSIONS

Although cardiac events occurred more frequently in men, the incremental value of exercise echocardiography was comparable in both genders. Of all exercise electrocardiographic and exercise echocardiographic variables, workload and exercise wall motion score index had the strongest association with outcome. The results of exercise echocardiography have comparable implications in both men and women.

Hypertensive response to exercise: a potential cause for new wall motion abnormality in the absence of coronary artery disease

OBJECTIVES

We sought to characterize patients with a hypertensive response during exercise echocardiography and its effect on results of the test.

BACKGROUND

A hypertensive response to exercise has been shown to cause false-positive results in perfusion imaging, radionuclide angiography and exercise electrocardiography, but its influence on exercise echocardiography has not been reported.

METHODS

We identified 548 of 6,686 patients who had coronary angiography within four weeks after exercise echocardiography from 1992 through 1996. Echocardiographic results from 132 patients (24%) with a hypertensive response to exercise, defined as systolic blood pressure (SBP) >220 mm Hg for men and SBP >190 mm Hg for women or as an increase in diastolic blood pressure (DBP) >10 mm Hg or DBP >90 mm Hg during exercise echocardiography, were compared with those from 416 patients without a hypertensive response.

RESULTS

Of 132 patients with a hypertensive response to exercise, 108 patients had exercise echocardiographic results positive for ischemia. Of these patients, 24 (22%) were found to have no significant coronary artery disease (CAD). In contrast, of 320 patients with positive exercise echocardiographic results without a hypertensive response, 39 (12%) patients did not have significant CAD. Among the false-positive results, new wall motion abnormalities were extensive in 15 of 24 (63%) hypertensive responders involving >25% of segments compared with 14 of 39 non-hypertensive responders (36%, p = 0.012).

CONCLUSIONS

An excessive rise in blood pressure during exercise is associated with a greater likelihood of new or worsening abnormalities with exercise, which may be observed in the absence of angiographically significant coronary artery stenosis.

Enhancement of contrast echocardiography by image variability analysis

BACKGROUND

Although there have been recent advances in echocardiography, many studies remain suboptimal due to poor image quality and unclear blood-myocardium border. We developed a novel image processing technique, cardiac variability imaging (CVI), based on the variance of pixel intensity values during passage of ultrasound microbubble contrast into the left ventricle chamber, with the aim of enhancing endocardial border delineation and image quality.

METHODS AND RESULTS

CVI analysis was performed on simulated data to test and verify the mechanism of image enhancement. Then CVI analysis was applied to echocardiographic images obtained in two different clinical studies, and still images were interpreted by expert reviewers. In the first study (N = 15), using contrast agent EchoGen, the number of observable wall segments in end-diastolic images, for example, was significantly increased by CVI (4.93) as compared to precontrast (3.28) and contrast images (3.36), P < 0.001 for both comparisons to CVI. In the second study (N = 8), using contrast agent Optison, interobserver variability of manually traced end-diastolic volumes was significantly decreased using CVI (22.3 ml) as compared to precontrast (63.4) and contrast images (49.0), P < 0.01 for both comparisons to CVI.

CONCLUSION

CVI can substantially enhance endocardial border delineation and improve echocardiographic image quality and image interpretation.

Effect of tissue Doppler on the accuracy of novice and expert interpreters of dobutamine echocardiography

The subjective interpretation of dobutamine echocardiography (DBE) makes the accuracy of this technique dependent on the experience of the observer, and also poses problems of concordance between observers. Myocardial tissue Doppler velocity (MDV) may offer a quantitative technique for identification of coronary artery disease, but it is unclear whether this parameter could improve the results of less expert readers and in segments with low interobserver concordance. The aim of this study was to find whether MDV improved the accuracy of wall motion scoring in novice readers, experienced echocardiographers, and experts in stress echocardiography, and to identify the optimal means of integrating these tissue Doppler data in 77 patients who underwent DBE and angiography. New or worsening abnormalities were identified as ischemia and abnormalities seen at rest as scarring. Segmental MDV was measured independently and previously derived cutoffs were applied to categorize segments as normal or abnormal. Five strategies were used to combine MDV and wall motion score, and the results of each reader using each strategy were compared with quantitative coronary angiography. The accuracy of wall motion scoring by novice (68 +/- 3%) and experienced echocardiographers (71 +/- 3%) was less than experts in stress echocardiography (88 +/- 3%, p <0.001). Various strategies for integration with MDV significantly improved the accuracy of wall motion scoring by novices from 75 +/- 2% to 77 +/- 5% (p <0.01). Among the experienced group, accuracy improved from 74 +/- 2% to 77 +/- 5% (p <0.05), but in the experts, no improvement was seen from their baseline accuracy. Integration with MDV also improved discordance related to the basal segments. Thus, use of MDV in all segments or MDV in all segments with wall motion scoring in the apex offers an improvement in sensitivity and accuracy with minimal compromise in specificity.

Prediction of mortality by exercise echocardiography: a strategy for combination with the duke treadmill score

BACKGROUND

In studies generally involving short follow-up, exercise echocardiography has been shown to predict composite end points. We sought to study the prediction of mortality with this test and to devise a strategy for combination with standard exercise testing.

METHODS AND RESULTS

Clinical, exercise testing, and echocardiographic data were collected in 5375 patients (aged 54+/-14 years, 3880 men) undergoing exercise echocardiography. The Duke treadmill score was derived from the results of treadmill exercise testing. Resting left ventricular (LV) function and the presence and severity of ischemia were interpreted by expert observers. Follow-up at 10.6 years (mean 5.5+/-1.9 years) was complete in 5211 patients (97%). The Duke score classified 59% of patients as low risk, 39% as intermediate risk, and 2% as high risk. Resting LV dysfunction was present in 1445 patients (27%), and the exercise echocardiogram was abnormal in 2525 patients (47%). Death occurred in 649 patients (12%). Over the first 6 years of follow-up, those with normal exercise echocardiograms had a mortality of 1% per year. Ischemia was an independent predictor of mortality. In sequential Cox models, the predictive power of clinical data was strengthened by adding the Duke score, resting LV function, and the results of exercise echocardiography. Exercise echocardiography was able to substratify patients with intermediate-risk Duke scores into groups with a yearly mortality of 2% to 7%.

CONCLUSIONS

A normal exercise echocardiogram confers a low risk of death, and positive results are an independent predictor of death; ischemia is incremental to other data. This test may be particularly useful in patients with intermediate-risk Duke treadmill scores.