American College of Cardiology/American Heart Association Clinical Competence Statement on Stress Testing. A Report of the American College of Cardiology/American Heart Association/American College of Physicians-American Society of Internal Medicine Task Force on Clinical Competence

Exercise Physiology and Cardiopulmonary Exercise Testing

Aerobic, or endurance, exercise is an energy requiring process supported primarily by energy from oxidative adenosine triphosphate synthesis. The consumption of oxygen and production of carbon dioxide in muscle cells are dynamically linked to oxygen uptake (V̇O2) and carbon dioxide output (V̇CO2) at the lung by integrated functions of cardiovascular, pulmonary, hematologic, and neurohumoral systems. Maximum oxygen uptake (V̇O2max) is the standard expression of aerobic capacity and a predictor of outcomes in diverse populations. While commonly limited in young fit individuals by the capacity to deliver oxygen to exercising muscle, (V̇O2max) may become limited by impairment within any of the multiple systems supporting cellular or atmospheric gas exchange. In the range of available power outputs, endurance exercise can be partitioned into different intensity domains representing distinct metabolic profiles and tolerances for sustained activity. Estimates of both V̇O2max and the lactate threshold, which marks the upper limit of moderate-intensity exercise, can be determined from measures of gas exchange from respired breath during whole-body exercise. Cardiopulmonary exercise testing (CPET) includes measurement of V̇O2 and V̇CO2 along with heart rate and other variables reflecting cardiac and pulmonary responses to exercise. Clinical CPET is conducted for persons with known medical conditions to quantify impairment, contribute to prognostic assessments, and help discriminate among proximal causes of symptoms or limitations for an individual. CPET is also conducted in persons without known disease as part of the diagnostic evaluation of unexplained symptoms. Although CPET quantifies a limited sample of the complex functions and interactions underlying exercise performance, both its specific and global findings are uniquely valuable. Some specific findings can aid in individualized diagnosis and treatment decisions. At the same time, CPET provides a holistic summary of an individual's exercise function, including effects not only of the primary diagnosis, but also of secondary and coexisting conditions.

Practices and Procedures in Clinical Pediatric Exercise Laboratories in North America

Interinstitutional differences in clinical pediatric exercise laboratory (CPEL) practices may affect patient care and efficacy of multicenter research.

PURPOSE

To describe current practices/procedures in CPELs and explore differences in CPELs employing exercise physiologists to those that do not.

METHODS

A 40-item survey was distributed to CPELs in North America focusing on (1) staffing; (2) exercise stress testing (EST) volumes, reporting, and interpretation; and (3) EST procedures/protocols.

RESULTS

Of the 55 responses, 89% were in the United States, 85% were children's hospitals with university affiliation, and 58% were cardiology specific. Exercise physiologists were employed in 56% of CPELs, and 78% had master's degrees or higher. Certifications were required in most CPELs (92% emergency life-support, 27% professional, and 21% clinical). Median volume was 201 to 400 ESTs per year, 80% used treadmill, and 10% used cycle ergometer as primary modalities. Ninety-three percent of CPELs offered metabolic ESTs, 87% offered pulmonary function testing, 20% used institution-specific EST protocols, and 72% offered additional services such as cardiac/pulmonary rehabilitation. CPELS staffing exercise physiologists performed higher volumes of ESTs (P = .004), were more likely to perform metabolic ESTs (P = .028), participated in more research (P < .001), and provided services in addition to ESTs (P = .001).

CONCLUSIONS

Heterogeneity in CPELs staffing and operation indicates need for standardization.

Exercise medicine and physical activity promotion: core curricula for US medical schools, residencies and sports medicine fellowships: developed by the American Medical Society for Sports Medicine and endorsed by the Canadian Academy of Sport and Exercise Medicine

Regular physical activity provides a variety of health benefits and is proven to treat and prevent several non-communicable diseases. Specifically, physical activity enhances muscular and osseous strength, improves cardiorespiratory fitness, and reduces the risk of hypertension, coronary heart disease, stroke, type 2 diabetes, mental health disorders, cognitive decline and several cancers. Despite these well-known benefits, physical activity promotion in clinical practice is underused due to insufficient training during medical education. Medical trainees in the USA receive relatively few hours of instruction in sports and exercise medicine (SEM). One reason for this shortage of instruction is a lack of curricular resources at each level of medical education. To address this need, the American Medical Society for Sports Medicine (AMSSM) assembled a group of SEM experts to develop curricular guidance for exercise medicine and physical activity promotion at the medical school, residency and sports medicine fellowship levels of training. After an evidence review of existing curricular examples, we performed a modified Delphi process to create curricula for medical students, residents and sports medicine fellows. Three training level-specific curricula emerged, each containing Domains, General Learning Areas, and Specific Learning Areas; options for additional training and suggestions for assessment and evaluation were also provided. Review and comment on the initial curricula were conducted by three groups: a second set of experts in exercise medicine and physical activity promotion, sports medicine fellowship directors representing a variety of fellowship settings and the AMSSM Board of Directors. The final curricula for each training level were prepared based on input from the review groups. We believe enhanced medical education will enable clinicians to better integrate exercise medicine and physical activity promotion in their clinical practice and result in healthier, more physically active patients.

Comparison of acute response of cardiac autonomic modulation between virtual reality-based therapy and cardiovascular rehabilitation: a cluster-randomized crossover trial

OBJECTIVE

To assess the acute response of cardiac autonomic modulation (ACAM) during and after a session of virtual reality-based therapy (VRBT) compared to a session of conventional cardiovascular rehabilitation (CR) and to evaluate the effects of 12 weeks of training on this response.

METHODS

We assessed 28 volunteers (63.4 ± 12.5 years). The ACAM was judged by linear indexes of heart rate variability (HRV) in VRBT and CR sessions. Later, patients completed 12 weeks of VRBT+CR and the assessment was repeated at the 12^th week.

RESULTS

Throughout the 1^st VRBT session vagal withdrawal occurred (RMSSD/HFnu); sympathetic nervous system stimulation (LFnu) and progressive decrease of global HRV (SDNN). During the recovery, the SDNN, HFnu, and LFnu improved from the 5^thminute on both therapies. After 12 weeks, the LFnu, HFnu, and the LF/HF-ratio revealed no significant changes in Ex3-Ex4 equated to Rep during VRBT. In recovery, the HFnu and LFnu improved before the 5^thminute on both therapies.

CONCLUSIONS

ACAM during and after the VRBT was comparable to CR, yet, the extents were greater in the VRBT. After 12 weeks of VRBT training, the subjects adapted to the exercises from the 15^thminute and exhibited faster recovery of HFnu and LFnu indexes compared to the 1^st week.

The Role of Gas Exchange Variables in Cardiopulmonary Exercise Testing for Risk Stratification and Management of Heart Failure with Reduced Ejection Fraction

Heart failure with reduced ejection fraction (HFrEF) is common in the developed world and results in significant morbidity and mortality. Accurate risk assessment methods and prognostic variables are therefore needed to guide clinical decision making for medical therapy and surgical interventions with the ultimate goal of decreasing risk and improving health outcomes. The purpose of this review is to examine the role of cardiopulmonary exercise testing (CPET) and its most commonly used ventilatory gas exchange variables for the purpose of risk stratification and management of HFrEF. We evaluated five widely studied gas exchange variables from CPET in HFrEF patients based on nine previously used systematic criteria for biomarkers. This paper provides clinicians with a comprehensive and critical overview, class recommendations and evidence levels. Although some CPET variables met more criteria than others, evidence supporting the clinical assessment of variables beyond peak V̇O₂ is well-established. A multi-variable approach also including the V̇_E-V̇CO₂ slope and EOV is therefore recommended.

Provocation of left ventricular outflow tract obstruction using nitrate inhalation in hypertrophic cardiomyopathy: Relation to electromechanical delay

Background: Left ventricular outflow tract obstruction (LVOT) is an independent predictor of adverse outcome in hypertrophic cardiomyopathy (HCM). It is of major importance that the provocation modalities used are validated against each other. Aim: To define the magnitude of LVOT gradients provocation during both isosorbide dinitrate (ISDN) inhalation and treadmill exercise in non-obstructive HCM and analyze the correlation to the electromechanical delay using speckle tracking. Methods: We studied 39 HCM pts (64% males, mean age 38 ± 13 years) regional LV longitudinal strain and electromechanical delay (TTP) was analyzed at rest using speckle tracking. LVOT gradient was measured at rest and after ISDN then patients underwent a treadmill exercise echocardiography (EE) and LVOT gradient was measured at peak exercise. Results: The maximum effect of ISDN on LVOT gradient was obtained at 5 minutes, it increased to a significant level in 12 (31%) patients, and in 14 (36%) patients using EE, with 85.6% sensitivity & 100% specificity. Patients with latent obstruction had larger left atrial volume and lower E/A ratio compared to the non-obstructive group (p < 0.01). LVOTG using ISDN was significantly correlated with that using EE (p < 0.0001), resting LVOTG (p < 0.0001), SAM (p < 0.0001), EF% (p < 0.02) and regional electromechanical delay but not related to global LV longitudinal strain. Using multivariate regression, resting LVOTG (p = 0.006) & TTP mid septum (p = 0.01) were found to be independent predictors of latent LVOT obstruction using ISDN. Conclusion: There is a comparable diagnostic value of nitrate inhalation to exercise testing in provocation of LVOT obstruction in HCM. Latent obstruction is predominantly dependent on regional electromechanical delay.

Evidence-based risk recommendations for best practices in the training of qualified exercise professionals working with clinical populations

This systematic review examines critically "best practices" in the training of qualified exercise professionals. Particular attention is given to the core competencies and educational requirements needed for working with clinical populations. Relevant information was obtained by a systematic search of 6 electronic databases, cross-referencing, and through the authors' knowledge of the area. The level and grade of the available evidence was established. A total of 52 articles relating to best practices and (or) core competencies in clinical exercise physiology met our eligibility criteria. Overall, current literature supports the need for qualified exercise professionals to possess advanced certification and education in the exercise sciences, particularly when dealing with "at-risk" populations. Current literature also substantiates the safety and effectiveness of exercise physiologist supervised stress testing and training in clinical populations.

Design and implementation of a stand-alone chest pain evaluation center within an academic emergency department

Chest pain is a common presenting symptom for emergency department (ED) patients; however, a thorough cardiac evaluation can be difficult to complete within the ED setting. Implementation of a stand-alone unit for the evaluation of chest pain may improve care for patients with chest pain. We designed a protocol for identifying patients without an acute coronary syndrome and with low-to-intermediate likelihood of obstructive coronary artery disease (CAD). These patients were monitored in a stand-alone chest pain evaluation center (CPEC) staffed with a small group of providers and tested for CAD, if necessary. In the first 6 weeks of operation, 181 patients were evaluated in the CPEC. The prevalence of CAD risk factors was low. Of the 181 patients, 159 (88%) were discharged home and 22 (12%) required admission to the hospital for further care. We compared the number of chest pain evaluations and admissions for first 6 weeks of operation to the same 6-week period from the 2 previous years. Whereas ED chest pain evaluations increased 66% over the 2-year time frame, the proportion admitted to the hospital decreased from 53% to 42% (P < 0.0001). In conclusion, evidence-based evaluation of chest pain in patients without acute coronary syndrome and with low-to-intermediate likelihood of obstructive CAD can result in the significant majority of patients being discharged from the ED. Creation of a stand-alone CPEC in an academic hospital was associated with a significant reduction in hospital admissions.

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

BACKGROUND

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

METHODS AND RESULTS

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

CONCLUSIONS

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

Cardiopulmonary exercise testing in congenital heart disease: (contra)indications and interpretation

Cardiopulmonary exercise testing (CPET) in paediatric cardiology differs in many aspects from the tests performed in adult cardiology. Children's cardiovascular responses during exercise testing present different characteristics, particularly oxygen uptake, heart rate and blood pressure response, which are essential in interpreting haemodynamic data. Diseases that are associated with myocardial ischaemia are rare in children. The main indications for CPET in children are evaluation of exercise capacity and the identification of exercise-induced arrhythmias. In this article we will review the main indications for CPET in children with congenital heart disease, the contraindications for exercise testing and the indications for terminating an exercise test. Moreover, we will address the interpretation of gas exchange data from CPET in children with congenital heart disease. (Neth Heart J 2009;17:385-92.).

The 20 year evolution of dobutamine stress cardiovascular magnetic resonance

Over the past 20 years, investigators world-wide have developed and utilized dobutamine magnetic resonance stress testing procedures for the purpose of identifying ischemia, viability, and cardiac prognosis. This article traces these developments and reviews the data utilized to substantiate this relatively new noninvasive imaging procedure.

The future of aerobic exercise testing in clinical practice: is it the ultimate vital sign?

The four traditional vital signs: resting heart rate, blood pressure, respiratory rate and body temperature, serve as the cornerstone of a physical examination. Other assessments such as pain have been proposed as additional vital signs. To this point however, there has been limited consideration for aerobic exercise assessment as a vital sign. A wealth of literature demonstrating the prognostic, diagnostic and interventional value of the aerobic exercise assessment now exists, supporting its use in numerous clinical scenarios. Moreover, the assessment of the aerobic exercise response allows for the manifestation of physiologic abnormalities that are not readily apparent during the collection of resting data. This review will provide evidence supporting the assertion that the aerobic exercise assessment may be afforded vital sign status in future clinical practice.

Nurse-led pharmacological stress testing: an overview

Myocardial perfusion imaging (MPI) is a noninvasive diagnostic tool that can provide valuable information on coronary blood flow at rest and during stress. Dynamic exercise is the stress technique of choice with patients who can achieve an acceptable workload; for those unable to do so, pharmacological stress testing with adenosine or dobutamine can be used. Nurses trained in ECG interpretation and advanced resuscitation skills are increasingly involved in supervising pharmacological stress tests. This article provides an overview of nurse-led pharmacological stress testing.

The Clinical Utility of Cardiopulmonary Exercise Testing in Suspected or Confirmed Myocardial Ischemia

Heart disease is a major cause of morbidity and mortality in the United States, with coronary artery disease (CAD) representing more than half of all cardiovascular events. Stable patients presenting with symptoms suggestive of CAD are likely to undergo an exercise electrocardiogram (ECG) and/ or imaging study as a first-line diagnostic assessment. A cardiopulmonary exercise test (CPX) is an ECG stress test plus ventilatory gas analysis. Recently, CPX has been used to detect exercise-induced myocardial ischemia (EIMI) suggestive of underlying CAD. Two CPX variables, oxygen pulse (VO2/HR) and the slope of oxygen consumption versus work rate (Δ VO2/ Δ WR), have been identified to be especially indicative of EIMI. Currently, there are a number of diagnostic tests available for the identification of CAD, with the most widely used being stress ECG, stress myocardial perfusion imaging (MPI) and echocardiography, and cardiac catheterization. Exercise ECG, although inexpensive, has a number of well-recognized limitations, including low sensitivity resulting in false-negative results. Stress (exercise or pharmaceutically induced) MPI and catheterization are more accurate but also more invasive and expensive. It appears that CPX may improve the diagnostic accuracy of exercise ECG. This review will address the potential utility of CPX in patients with suspected or confirmed myocardial ischemia.

The Clinical Significance of Aerobic Exercise Testing and Prescription: From Apparently Healthy to Confirmed Cardiovascular Disease

Aerobic exercise testing clearly provides valuable clinical information in apparently healthy adults as well as a number of patient populations. Maximal aerobic capacity, either estimated from workload or measured directly, is perhaps the most frequently analyzed variable ascertained from such testing. This practice is warranted given the consistent prognostic significance of maximal aerobic capacity. Other variables obtained from the aerobic exercise test, such as the heart rate response during exercise and into recovery, the systolic and diastolic blood pressure responses during exercise, oxygen consumption at anaerobic threshold, and the ventilatory response to exercise, also provide important insight into an individual's health and prognosis. Furthermore, the aerobic exercise test is highly valuable in developing an individualized and safe exercise prescription. Aerobic exercise training goals, with respect to frequency, duration, frequency, and mode of exercise, are well established for the apparently healthy population as well as individuals at risk for or diagnosed with cardiovascular disease. Adherence to these physical activity recommendations clearly provides numerous health benefits, perhaps most important of which is a significant decrease in the risk for cardiovascular events and mortality. This review addresses concepts of aerobic exercise testing and training and discusses their clinical implications.

Emergency ultrasound usage among recent emergency medicine residency graduates of a convenience sample of 14 residencies

BACKGROUND

Emergency Medicine (EM) residency graduates are trained to perform Emergency Medicine bedside ultrasound (EMBU). However, the degree to which they use this skill in their practice after graduation is unknown.

OBJECTIVES

We sought to test the amount and type of usage of EMBU among recent residency graduates, and how usage and barriers vary among various types of EM practice settings.

METHODS

Graduates from 14 EM residency programs in 2003-2005 were surveyed on their current practice setting and use of EMBU.

RESULTS

There were 252 (73%) graduates who completed the survey. Of the 73% of respondents reporting access to EMBU, 98% had used it within the past 3 months. Access to EMBU was higher in academic (97%) vs. community teaching (79%) vs. community non-teaching settings (62%) (p < 0.001), and in Emergency Departments (EDs) where yearly census exceeded 60,000 visits (87% vs. 65%, p < 0.001). Physicians in academic settings reported "high use" of EMBU more frequently than those in community settings for most modalities. FAST (focused assessment by sonography in trauma) was the most common high-use application and the most useful in practice. The greatest impediment to EMBU use was "not enough time" (61%).

CONCLUSIONS

Ultrasound usage among recent EM residency graduates is significantly higher in teaching than in community settings and in high-volume EDs. Its use is more widespread than in previous reports in all types of practice. There is a wide range of utilization of ultrasound in the various applications in emergency practice, with the evaluation of trauma being the most common.

Clinical competence in myocardial perfusion scintigraphic stress testing: general training guidelines and assessment

The suggestion by the National Institute for Clinical Excellence (NICE) to more than triple the number of myocardial perfusion scintigraphy (MPS) procedures carried out by the NHS each year is a challenge both in terms of numbers of gamma cameras available to carry out the scans and qualified staff to supervise stress tests. In the past, exercise and pharmacological stress testing have been supervised only by doctors but, increasingly, this is taken on by suitably trained non-medical professionals such as nurses, radiographers and clinical technologists. The expansion of the numbers of non-medical professionals qualified to supervise stress testing will be key to meeting NICE's recommendations. This paper sets out how potential new stressors should be identified, what their training should cover and discusses the standards of competence they should meet. It provides guidelines for training non-medical stressors to perform a safe and efficient stress test during MPS and advice for maintaining competency.

Stress Testing in Patients With Implantable Cardioverter-Defibrillators: A Preliminary Report

This retrospective study was undertaken to assess the responses to, and complications associated with, stress testing in patients with implantable cardioverter-defibrillators (ICDs). Primary end points were occurrence of malignant ventricular arrhythmias, onset of burst pacing or ICD firing, cardiopulmonary resuscitation, or death during or soon after stress testing. Secondary end points were urgent coronary revascularization and/or hospital readmission for cardiovascular complications. During a 4-year period, 1734 patients underwent ICD implantation or generator replacement at our institution; 84 patients (mean age +/- SD, 67+/-12 years; 76% men) subsequently underwent 107 stress tests, including 44 exercise and 63 pharmacologic (22 dobutamine, 41 dipyridamole) evaluations. None of the ICDs were inactivated before testing. All tests were supervised by specially trained paramedical personnel, with a physician immediately available. Four patients had self-terminating, nonsustained ventricular tachycardia at peak stress. None had sustained ventricular tachycardia requiring emergent therapy. There were no deaths or hospital readmissions for ventricular arrhythmias. These findings suggest that stress testing is feasible in patients with ICDs and that it can be performed without pretest inactivation.

Statement on cardiopulmonary exercise testing in chronic heart failure due to left ventricular dysfunction: recommendations for performance and interpretation Part II: How to perform cardiopulmonary exercise testing in chronic heart failure

Basic and practical information related to equipment, methodology, exercise protocols, conduct of the test and quality control issues for cardiopulmonary exercise testing (CPET) will be addressed in this II part of the statement. CPET users have the responsibility for assuring that measurements remain accurate. CPT, especially when it features breath-by-breath gas exchange analysis, requires meticulous attention to calibration procedures to assure accurate and reproducible measurements. Skills and knowledge of personnel for supervision and test interpretation, as well as patient preparation and information are key features for a correct CPET conduction: all these issues will be faced. Finally, after the test, the investigator needs to format the results in a manner that optimises the ability to discriminate essential response features; that is, to establish 'interpretive clusters' of the variables of interest. An example of a cardiopulmonary summary exercise test data report will be provided, defining the most important information that should be incorporated in a final report.

Electrocardiographic exercise stress testing: an update beyond the ST segment

Routine exercise testing is frequently ordered to evaluate a patient's cardiovascular performance. The test is more direct and less expensive than imaging technology, and derives valuable information. New variables such as dyspnea and heart rate recovery, as well as integrated scores, provide incremental value to conventional analysis of exercise-induced angina or electrocardiographic changes. Considerations relating to test accuracy in women need to be weighed. This paper seeks to make physicians aware of the current status of the test, and improve their understanding of and ability to integrate new variables and scores to more effectively manage their patients.

Cardiac stress MR imaging with dobutamine

Stress testing for detection of ischemia-induced wall-motion abnormalities has become a mainstay for noninvasive diagnosis and risk stratification of patients with suspected coronary artery disease (CAD). Recent technical developments in magnetic resonance imaging (MRI), including the adoption of balanced steady-state free precession (b-SSFP) sequences-preferentially in combination with parallel imaging techniques-have led to a significant reduction of imaging time and improved patient safety. The stress protocol includes application of high-dose dobutamine (up to 40 microg/kg/min) combined with fractionated atropine (up to a maximal dose of 1.0 mg). High-dose dobutamine stress MRI revealed good sensitivity (83-96%) and specificity (80-100%) for detection of significant CAD. Myocardial tagging methods have been shown to further increase sensitivity for CAD detection. Severe complications (sustained tachycardia, ventricular fibrillation, myocardial infarction, cardiogenic shock) are rare but may be expected in 0.1-0.3% of patients. Dobutamine stress MRI has emerged as a reliable and safe clinical alternative for noninvasive assessment of CAD. New pulse sequences, such as real-time imaging, might obviate the need for breath holding and electrocardiogram (ECG) triggering in patients with severe dyspnoea and cardiac arrhythmias, which may further improve the clinical impact and acceptance of stress MRI in the future.

Pacing stress echocardiography

Background

High-rate pacing is a valid stress test to be used in conjunction with echocardiography; it is independent of physical exercise and does not require drug administration. There are two main applications of pacing stress in the echo lab: the noninvasive detection of coronary artery disease through induction of a regional transient dysfunction; and the assessment of contractile reserve through peak systolic pressure/ end-systolic volume relationship at increasing heart rates to assess global left ventricular contractility.

Methods

The pathophysiologic rationale of pacing stress for noninvasive detection of coronary artery disease is obvious, with the stress determined by a controlled increase in heart rate, which is a major determinant of myocardial oxygen demand, and thereby tachycardia may exceed a fixed coronary flow reserve in the presence of hemodynamically significant coronary artery disease. The use of pacing stress echo to assess left ventricular contractile reserve is less established, but promising. Positive inotropic interventions are mirrored by smaller end-systolic volumes and higher end-systolic pressures. An increased heart rate progressively increases the force of ventricular contraction (Bowditch treppe or staircase phenomenon). To build the force-frequency relationship, the force is determined at different heart rate steps as the ratio of the systolic pressure (cuff sphygmomanometer)/end-systolic volume index (biplane Simpson rule). The heart rate is determined from ECG.

Conclusion

Two-dimensional echocardiography during pacing is a useful tool in the detection of coronary artery disease. Because of its safety and ease of repeatability noninvasive pacing stress echo can be the first-line stress test in patients with permanent pacemaker.

The force-frequency can be defined as up- sloping (normal) when the peak stress pacing systolic pressure/end-systolic volume index is higher than baseline and intermediate stress values, biphasic with an initial up- sloping followed by a later down-sloping trend, or flat or negative when peak stress pacing systolic pressure/end-systolic volume index is equal or lower than baseline stress values. This approach is certainly highly feasible and allows a conceptually immaculate definition of contractility with prognostic usefulness, but its therapeutic implications remains to be established. Bowditch treppe, assessed with pacing stress, can be used to assess the optimal stimulation frequency and to optimise the patient's chronotropic response in programming rate-adaptive pacemakers.

Exercise testing in pediatrics

This article discusses exercise physiology and its application in the pediatric population. This article discusses exercise physiology and its application in the pediatric population. The authors briefly review the normal physiologic response to exercise. They then discuss populations in which exercise testing is most useful, the indications and contraindications for graded exercise, and the usual parameters that are measured during testing. Finally, the authors review some of the recent data on exercise performance in specific pediatric populations.

High-Dose Dobutamine-Atropine Stress Cardiovascular MR Imaging after Coronary Revascularization in Patients with Wall Motion Abnormalities at Rest

PURPOSE

To determine the value of high-dose dobutamine-atropine stress cardiovascular magnetic resonance (MR) imaging for diagnosis of ischemia in patients with coronary artery disease (CAD) who had undergone revascularization and have wall motion abnormalities at rest, with quantitative invasive coronary angiography serving as reference standard.

MATERIALS AND METHODS

One hundred sixty consecutive patients (mean age, 59 years +/- 8 [standard deviation]) who had undergone revascularization for CAD and have wall motion abnormalities at rest underwent stress cardiovascular MR imaging prior to clinically indicated invasive coronary angiography. Turbo gradient-echo MR images were acquired at rest and during a standardized high-dose dobutamine-atropine protocol with three short-axis and two long-axis views. Regional wall motion was assessed by a blinded observer by using a 16-segment model and a four-point scoring system. New or worsening wall motion abnormality in at least one segment was considered positive for myocardial ischemia.

RESULTS

Significant CAD (stenoses of at least 50% diameter at angiography) was found in 119 patients (74%). Target heart rate was not reached in nine patients (6%). Overall sensitivity and specificity for detection of significant CAD were 89% and 84%, respectively. Diagnostic accuracy was 88%, and positive and negative predictive values were 94% and 73%, respectively. Overall sensitivity for detection of significant CAD in patients with single-, double-, and triple-vessel disease was 87%, 88%, and 100%, respectively.

CONCLUSION

High-dose stress cardiovascular MR imaging can be used for follow-up of patients after coronary revascularization procedures. Diagnostic accuracy is similar to stress cardiovascular MR imaging data for patients suspected of having CAD and compares favorably with that of other established noninvasive techniques.

Feasibility to detect severe coronary artery stenoses with upright treadmill exercise magnetic resonance imaging

We performed treadmill exercise magnetic resonance imaging in 27 patients with exertional chest pain who were referred for contrast coronary angiography to determine the feasibility of this method to identify severe coronary artery stenoses. The sensitivity and specificity for detecting >70% coronary artery luminal diameter narrowings on contrast coronary angiography were 79% and 85%, respectively.

Force-frequency relationship in the echocardiography laboratory: a noninvasive assessment of Bowditch treppe?

BACKGROUND

Estimation of contractility of the left ventricle is an important, and as yet elusive, goal with noninvasive techniques.

OBJECTIVE

We sought to assess the feasibility of a totally noninvasive estimation of force-frequency relation (FFR) during exercise stress in the echocardiography laboratory.

METHODS

We enrolled 13 healthy control patients (12 men, age 38 +/- 15 years) as group I, and 50 patients (38 men, age 64 +/- 11 years) referred for exercise echocardiography as group II. To build the FFR, the force was determined at each step as the ratio of the systolic pressure (cuff sphygmomanometer)/end-systolic volume index (biplane Simpson's rule/body surface area). The slope of the relationship was calculated with the linear best fit of the FFR.

RESULTS

Noninvasive systolic pressure/end-systolic volume ratio was obtained in all patients. The slope of the linear best fit of the force-frequency curve was lower in group II compared with group I (group II = 10.1 +/- 9.3 x 10(-2) vs group I = 14.9 +/- 9.9 x 10(-2) group I, P =.04). By regional wall-motion analysis, 2 subgroups were identified in group II: group IIA (n = 8) had a positive echocardiogram; and group IIB (n = 42) had a negative echocardiogram. The slope of the force-frequency curve was lower in patients with ischemia compared with those without (group IIA = 3.5 +/- 4.2 x 10(-2) vs group IIB = 11.4 +/- 9.5 x 10(-2); P =.012). Heart rate-systolic pressure/end-systolic volume index relation was biphasic, with an initial positive slope and a subsequent negative slope in 1 patient of group I, 4 patients of group IIA, and 15 patients of group IIB (P <.05 vs group I).

CONCLUSION

A noninvasive estimation of FFR can be easily determined during exercise echocardiography. This index of global contractility is theoretically appealing for identification of limited contractile reserve and latent global left ventricular dysfunction.

Critical pathway for an aggressive diagnostic strategy for patients who present with chest pain but a nondiagnostic electrocardiogram to the emergency department

BACKGROUND

The prolonged length of stay for patients who seek treatment in the emergency department with chest pain and normal or nondiagnostic electrocardiogram has led to a backlog of patients in the emergency department and the telemetry unit. Correct early management requires risk stratification processes that can effectively separate the majority of these patients into low-risk, low/intermediate-risk, intermediate-risk, and high-risk subsets.

METHODS AND RESULTS

Patients who seek treatment in the emergency department with chest pain are risk-stratified into low-risk, low/intermediate-risk, and high-risk categories using a Risk Score to determine who would benefit from immediate exercise stress testing. Nurse-directed exercise stress testing using the Duke Treadmill Score is used to risk-stratify intermediate-risk patients further "on-the-fly". Intermediate-risk Duke Treadmill Score patients are injected during exercise with a Tc-myocardial perfusion agent and undergo a gated single-photon emission computed tomography study. Normal exercise and single-photon emission computed tomography perfusion patients are discharged home. The overall length of stay and 30-day outcomes of these facilitated patients were compared with those of patients treated with a conservative approach using sequential electrocardiograms and cardiac enzymes. Patients who were evaluated using the facilitated approach had a shorter mean length of stay than those using a conservative method, with similar outcomes at 30 days.

CONCLUSIONS

A facilitated approach incorporating on-demand nurse-directed early exercise stress testing with the injection of a Tc-myocardial perfusion agent on the fly in intermediate-risk patients is safe and has decreased the backlog of patients in the emergency department and telemetry unit and expedited appropriate treatment of patients with acute chest pain and nondiagnostic electrocardiograms.

Do vascular surgery patients need a cardiology work-up? A review of pre-operative cardiac clearance guidelines in vascular surgery

OBJECTIVES

to outline the appropriate pre-operative cardiac work-up for patients who are scheduled for major peripheral vascular surgery.

DESIGN

review of the literature.

MATERIALS AND METHODS

a review of the literature focusing on studies that have correlated the pre-operative cardiac work-up patients receive to the cardiac morbidity and mortality following vascular surgery. Only studies with level A evidence were included.

RESULTS

peri-operative beta blockade has been shown to decrease cardiac complications after vascular surgery in all risk groups. Non-invasive cardiac testing is only necessary for patients in the intermediate/high risk group. Coronary revascularization should only be considered after a positive non-invasive cardiac test.

CONCLUSIONS

patients must be risk stratified pre-operatively based on history and physical examination. Low risk patients should receive peri-operative beta blockade only with no further non-invasive testing. On the other hand, intermediate and high risk patients should undergo non-invasive cardiac testing before going to the operating room.

Guidelines for pediatric cardiovascular centers

Pediatric cardiovascular centers should aim to provide high-quality therapeutic outcomes for infants and children with congenital and acquired heart diseases. This policy statement describes critical elements and organizational features of centers in which high-quality outcomes have the greatest likelihood of occurring. Center elements include noninvasive diagnostic modalities, cardiac catheterization, cardiovascular surgery, and cardiovascular intensive care. These elements should be organizationally united in centers in which pediatric cardiac physician specialists and specialized pediatric staff work together to achieve and surpass existing quality-of-care benchmarks.