The utility of cardiopulmonary exercise testing in the assessment of suspected microvascular ischemia

The association between O2-pulse slope ratio and functional severity of coronary stenosis: A combined cardiopulmonary exercise testing and quantitative flow ratio study

Background

The role of cardiopulmonary exercise testing (CPET) parameters in evaluating the functional severity of coronary disease remains unclear. The aim of this study was to quantify the O2-pulse morphology and investigate its relevance in predicting the functional severity of coronary stenosis, using Murray law-based quantitative flow ratio (μQFR) as the reference.

Methods

CPET and μQFR were analyzed in 138 patients with stable coronary artery disease (CAD). The O2-pulse morphology was quantified through calculating the O2-pulse slope ratio. The presence of O2-pulse plateau was defined according to the best cutoff value of O2-pulse slope ratio for predicting μQFR ≤ 0.8.

Results

The optimal cutoff value of O2-pulse slope ratio for predicting μQFR ≤ 0.8 was 0.4, with area under the curve (AUC) of 0.632 (95 % CI: 0.505-0.759, p = 0.032). The total discordance rate between O2-pulse slope ratio and μQFR was 27.5 %, with 13 patients (9.4 %) being classified as mismatch (O2-pulse slope ratio > 0.4 and μQFR ≤ 0.8) and 25 patients being classified as reverse-mismatch (O2-pulse slope ratio ≤ 0.4 and μQFR > 0.8). Angiography-derived microvascular resistance was independently associated with mismatch (OR 0.07; 95 % CI: 0.01-0.38, p = 0.002) and reverse-mismatch (OR 9.76; 95 % CI: 1.47-64.82, p = 0.018).

Conclusion

Our findings demonstrate the potential of the CPET-derived O2-pulse slope ratio for assessing myocardial ischemia in stable CAD patients.

Men with nonobstructive coronary disease have higher burden of ischemic heart disease detected by cardiopulmonary exercise test

BACKGROUND

Nonobstructive coronary artery disease (NOCAD), characterized by the presence of myocardial ischemic symptoms and signs without obstructive coronaries, is a common clinical condition, but it is less well understood. Few studies have analyzed the gender differences in inducible myocardial ischemia assessed by cardiopulmonary exercise test (CPET) in NOCAD.

METHODS

We conducted a study of 289 NOCAD patients (mean age 60, 56% women) with ischemic symptoms and confirmed ⫹50% coronaries stenoses by coronary angiography who underwent symptom-limited CPET. We assessed ischemic response using predicted % peak VO2 , O2 pulse trajectory, and exercise ECG test.

RESULTS

Men with NOCAD had significantly lower predicted % peak VO2 (62% vs. 73%), higher proportions of flattening pattern (16% vs. 2%), and downward patterns of O2 pulse trajectory (2% vs. 0%) (p < .0001) compared with women. In contrast, women with NOCAD had a higher prevalence of shallow patterns of O2 pulse trajectory (21% vs. 6%, p < .0001). Men with NOCAD had a higher risk ischemic profile (medium risk: 63% vs. 54%, high risk: 18% vs. 4%, p < .0001). After adjustment, men with NOCAD had significantly lower predicted % peak VO2 (β -27.4, 95% CI -30.74 to -24.07), higher risk for abnormal O2 pulse trajectories (OR 4.21, 95% CI 1.93 to 9.19), and myocardial ischemia risk per CPET parameters (OR 3.14, 95% CI 1.78 to 5.54) (p < .0001).

CONCLUSION

Men with NOCAD had a higher risk profile for ischemic heart disease per CPET. Therefore, they should receive rigorous management and follow-up to prevent cardiovascular events.

The evolving role of cardiopulmonary exercise testing in ischemic heart disease - state of the art review

PURPOSE OF REVIEW

Cardiopulmonary exercise testing (CPET) is the gold standard for directly assessing cardiorespiratory fitness (CRF) and has a relatively new and evolving role in evaluating atherosclerotic heart disease, particularly in detecting cardiac dysfunction caused by ischemic heart disease. The purpose of this review is to assess the current literature on the link between cardiovascular (CV) risk factors, cardiac dysfunction and CRF assessed by CPET.

RECENT FINDINGS

We summarize the basics of exercise physiology and the key determinants of CRF. Prognostically, several studies have been published relating directly measured CRF by CPET and outcomes allowing for more precise risk assessment. Diagnostically, this review describes in detail what is considered healthy and abnormal cardiac function assessed by CPET. New studies demonstrate that cardiac dysfunction on CPET is a common finding in asymptomatic individuals and is associated with CV risk factors and lower CRF. This review covers how key CPET parameters change as individuals transition from the asymptomatic to the symptomatic stage with progressively decreasing CRF. Finally, a supplement with case studies with long-term longitudinal data demonstrating how CPET can be used in daily clinical decision making is presented.

SUMMARY

In summary, CPET is a powerful tool to provide individualized CV risk assessment, monitor the effectiveness of therapeutic interventions, and provide meaningful feedback to help patients guide their path to improve CRF when routinely used in the outpatient setting.

Early flattening of the oxygen pulse during the cardiopulmonary exercise test in asymptomatic adults and its association with cardiovascular risk factors

BACKGROUND

Individuals with cardiovascular exercise limitations present oxygen pulse morphology with early flattening (plateau) during the cardiopulmonary exercise test (CPET). Although this oxygen pulse response is well known in cardiac patients, these changes' prevalence and clinical relevance in asymptomatic individuals are not known. We aimed to quantify the proportion of asymptomatic adults with an early flattening of the oxygen pulse and investigate its association with classical cardiovascular risk factors.

METHODS

We carried out a cross-sectional study with a sample of 824 adults aged between 18 and 80 years. We assessed anthropometry, body composition, and cardiovascular risk. In addition, we obtained cardiorespiratory and metabolic responses during a ramp protocol treadmill CPET.

RESULTS

The prevalence of early flattening of the oxygen pulse was 36.8%. These participants were predominantly females, older, less educated, with a higher body mass and percentage of fat and a lower percentage of lean body mass. After a multinominal multiple logistic regression analysis, we identified female sex (odds ratio, 5.46: 95% confidence interval, 3.73-7.99), low education (2.24: 1.47-3.42), dyslipidemia (1.67: 1.14-2.45), smoking (1.64: 1.00-2.69), and physical inactivity (1.39: 1.02-1.96) as the leading independent predictors of the early flattening of oxygen pulse.

CONCLUSION

The early flattening of oxygen pulse is common in asymptomatic adults and is highly determined by modifiable cardiovascular risk factors. These results suggest that identifying the early flattening of oxygen pulse may be helpful in the prevention of cardiovascular diseases.

Cardiopulmonary exercise test in myocardial ischemia detection

Exercise electrocardiography has low sensitivity for detection of myocardial ischemia. However, when combined with cardiopulmonary exercise testing (CPEX), the sensitivity and specificity of ischemia detection improves significantly. CPEX offers unique advantages over imaging techniques in tricky situations such as balanced ischemia. Early abnormal oxygen uptake would point toward profound coronary stenosis that could be missed in perfusion imaging. CPEX could be an invaluable tool in asymptomatic left bundle branch block pattern, without exposing patients to the risks of computerized tomography or invasive coronary angiography. Normal oxygen uptake curves would rule out significant coronary stenosis as the cause of left bundle branch block pattern. Elseways, abnormal oxygen uptake in patients with normal coronary arteries could indicate microvascular angina. Furthermore, exercise capacity is an excellent predictor of cardiovascular risk in those with and without heart disease. Using two clinical cases we introduce the concept of gas-exchange and hemodynamic changes encountered in ischemic heart disease.

The functional assessment of patients with non-obstructive coronary artery disease: expert review from an international microcirculation working group

Symptomatic non-obstructive coronary artery disease (NOCAD) is an increasingly recognised entity that is associated with poor cardiovascular outcomes. Nearly half of those undergoing coronary angiography for appropriate indications, such as typical angina, or a positive stress test have no obstructive lesion. There are no guideline recommendations as to how to care properly for these patients. Physiologic assessment of the coronary arteries beyond two-dimensional angiography is not standardised, yet it can provide valuable information in patients presenting with typical angina in the setting of NOCAD. In this consensus document, we detail steps for the interventional cardiologist to evaluate the patient with symptomatic NOCAD in the cardiac catheterisation laboratory, first with the assessment of coronary flow reserve (CFR), and then with delineation of deficiencies in non-endothelium-dependent CFR (CFRne) versus endothelium-dependent CFR (CFRe) using provocative agents such as adenosine and acetylcholine, respectively, followed by the evaluation of smooth muscle function with nitroglycerine (NTG). Once the mechanism behind the anginal symptoms is established, one can identify the appropriate treatment strategies to address the physiologic deficiency that is present. Despite an established safety profile, a comprehensive assessment may be considered for selected patients which requires an understanding of the appropriate invasive evaluation by the practising interventional cardiologist when evaluating not only patients with obstructive CAD but also those with NOCAD.

A practical clinical approach to utilize cardiopulmonary exercise testing in the evaluation and management of coronary artery disease: a primer for cardiologists

PURPOSE OF REVIEW

There is growing clinical interest for the use of cardiopulmonary exercise testing (CPET) to evaluate patients with or suspected coronary artery disease (CAD). With mounting evidence, this concise review with relevant teaching cases helps to illustrate how to integrate CPET data into real world patient care.

RECENT FINDINGS

CPET provides a novel and purely physiological basis to identify cardiac dysfunction in symptomatic patients with both obstructive-CAD and nonobstructive-CAD (NO-CAD). In many cases, abnormal cardiac response on CPET may be the only objective evidence of potentially undertreated ischemic heart disease. When symptomatic patients have NO-CAD on coronary angiogram, they are still at increased risk for cardiovascular events. This problem appears to be more common in women than men and may warrant more aggressive risk factor modification. As the main intervention is lifestyle (diet, smoking cessation, exercise) and medical therapy (statins, angiotensin-converting enzyme inhibitors, beta-blockers), serial CPET testing enables close surveillance of cardiovascular function and is responsive to clinical status.

SUMMARY

CPET can enhance outpatient evaluation and management of CAD. Diagnostically, it can help to identify physiologically significant obstructive-CAD and NO-CAD in patients with normal routine cardiac testing. CPET may be of particular value in symptomatic women with NO-CAD. Prognostically, precise quantification of improvements in exercise capacity may help to improve long-term lifestyle and medication adherence for this chronic condition.

CO2 pulse and acid-base status during increasing work rate exercise in health and disease

The CO2 pulse (VCO2/heart rate), analogous to the O2 pulse (VO2/heart rate), was calculated during cardiopulmonary exercise testing and evaluated in normal and diseased states. Our aim was to define its application in its release in excess of that from VCO2/heart rate in the presence of impaired cardiovascular and lung function. In the current study, forty-five patients were divided into six physiological states: normal, exercise-induced myocardial ischemia, chronic heart failure, pulmonary vasculopathy, chronic obstructive pulmonary disease, and interstitial lung disease. We subtracted the O2 pulse from the CO2 pulse to determine the exhaled CO2 that could be attributed to CO2 pulse of buffering of lactic acid. The difference between the CO2 pulse and O2 pulse (VCO2/heart rate-VO2/heart rate) includes CO2 generated from HCO3(-) buffering of lactic acid. The accumulated CO2 per body mass was found to be significantly correlated with the corresponding [HCO3(-)] decrease (R(2)=0.72; P<0.0001). In summary, the increase in CO2 pulse over the O2 pulse accounted for the anaerobically-generated excess-CO2 in each of the physiological states and correlated with the decreases in the arterial Bicarbonate concentration.

Impact of completeness of revascularization by coronary intervention on exercise capacity early after acute ST-elevation myocardial infarction

Background

The importance of achieving complete revascularization by percutaneous coronary intervention (PCI) in patients with acute myocardial infarction (MI) on exercise capacity remains unclear.

Objective

To compare exercise capacity early after acute ST-elevation myocardial infarction (STEMI), in patients receiving PCI with stenting, between those completely revascularized (CR) and those incompletely revascularized (IR).

Methods

We retrospectively reviewed 326 patients [single-vessel disease (SVD) group, 118 patients; multivessel disease (MVD) with CR group, 112 patients; MVD with IR group, 96 patients] who underwent cardiopulmonary exercise testing 7–30 days after STEMI to measure peak oxygen uptake (VO_2peak), oxygen uptake at anaerobic threshold (VO_2AT), and peak oxygen pulse. Demographic data, presence of concomitant diseases, STEMI characteristics, and echocardiography and angiography findings were evaluated.

Results

Most patients were male (89.0%) and mean age was 55.6 ± 11.2 years. Ischemic ST deviation occurred in 7.1%, with no significant difference between groups. VO_2peak and VO_2AT did not differ significantly between groups, despite a trend to be lower in the CR and IR groups compared with the SVD group. Peak oxygen pulse was significantly higher in the SVD group than in the IR group (p = 0.005). After adjustment for age, gender, body mass index, cardiovascular risk factors, MI characteristics and echocardiography parameters, CR was not an independent predictor of VO_2peak (OR = −0.123, 95% confidence interval [CI] -2.986 to 0.232, p = 0.093), VO_2AT (OR = 0.002, 95% CI 1.735 to 1.773, p = 0.983), or peak oxygen pulse (OR = −0.102, 95% CI −1.435 to 0.105, p = 0.090).

Conclusion

CR in patients with STEMI treated with PCI for multivessel disease might show no benefit on short-term exercise tolerance over IR.

Clinical usefulness of response profiles to rapidly incremental cardiopulmonary exercise testing

The advent of microprocessed "metabolic carts" and rapidly incremental protocols greatly expanded the clinical applications of cardiopulmonary exercise testing (CPET). The response normalcy to CPET is more commonly appreciated at discrete time points, for example, at the estimated lactate threshold and at peak exercise. Analysis of the response profiles of cardiopulmonary responses at submaximal exercise and recovery, however, might show abnormal physiologic functioning which would not be otherwise unraveled. Although this approach has long been advocated as a key element of the investigational strategy, it remains largely neglected in practice. The purpose of this paper, therefore, is to highlight the usefulness of selected submaximal metabolic, ventilatory, and cardiovascular variables in different clinical scenarios and patient populations. Special care is taken to physiologically justify their use to answer pertinent clinical questions and to the technical aspects that should be observed to improve responses' reproducibility and reliability. The most recent evidence in favor of (and against) these variables for diagnosis, impairment evaluation, and prognosis in systemic diseases is also critically discussed.

The utility of cardiopulmonary exercise testing to detect and track early-stage ischemic heart disease

Evidence demonstrating the potential value of noninvasive cardiopulmonary exercise testing (CPET) to accurately detect exercise-induced myocardial ischemia is emerging. This case-based concept report describes CPET abnormalities in an asymptomatic at-risk man with suspected early-stage ischemic heart disease. When CPET was repeated 1 year after baseline assessment, his cardiovascular function had worsened, and an anti-atherosclerotic regimen was initiated. When the patient was retested after 3.3 years, the diminished left ventricular function had reversed with pharmacotherapy directed at decreasing cardiovascular events in patients with coronary artery disease. Thus, in addition to identifying appropriate patients in need of escalating therapy for atherosclerosis, CPET was useful in monitoring progression and reversal of abnormalities of the coronary circulation in a safe and cost-effective manner without the use of radiation. Serial CPET parameters may be useful to track changes marking the progression and/or regression of the underlying global ischemic burden.