Dyspnea Among Patients With Chronic Total Occlusions Undergoing Percutaneous Coronary Intervention: Prevalence and Predictors of Improvement

Coronary Chronic Total Occlusion Revascularization: When, Who and How?

Coronary chronic total occlusions (CTO) are an increasingly frequent entity in clinical practice and represent a challenging percutaneous coronary intervention (PCI) scenario. Despite data from randomized trials that have not yet demonstrated a clear benefit of CTO recanalization, the widespread of CTO-PCI has substantially increased. The improvement in operators' techniques, equipment, and training programs has led to an improvement in the success rate and safety of these procedures, which will represent an important field of future development of PCI. The present review will summarize clinical outcomes and technical and safety issues of CTO revascularization with the aim to guide clinical daily cath-lab practice.

Evaluation and management of patients with coronary chronic total occlusions considered for revascularisation. A clinical consensus statement of the European Association of Percutaneous Cardiovascular Interventions (EAPCI) of the ESC, the European Association of Cardiovascular Imaging (EACVI) of the ESC, and the ESC Working Group on Cardiovascular Surgery

Chronic total occlusions (CTOs) of coronary arteries can be found in the context of chronic or acute coronary syndromes; sometimes they are an incidental finding in those apparently healthy individuals undergoing imaging for preoperative risk assessment. Recently, the invasive management of CTOs has made impressive progress due to sophisticated preinterventional assessment, including advanced non-invasive imaging, the availability of novel and dedicated tools for CTO percutaneous coronary intervention (PCI), and experienced interventionalists working in specialised centres. Thus, it is crucial that referring physicians who see patients with CTO be aware of recent developments and of the initial evaluation requirements for such patients. Besides a careful history and clinical examination, electrocardiograms, exercise tests, and non-invasive imaging modalities are important for selecting the patients most suitable for CTO PCI, while others may be referred to coronary artery bypass graft or optimal medical therapy only. While CTO PCI improves angina and reduces the use of antianginal drugs in patients with symptoms and proven ischaemia, hibernation and/or wall motion abnormalities at baseline or during stress, the effect of CTO PCI on major cardiovascular events is still controversial. This clinical consensus statement specifically focuses on referring physicians, providing a comprehensive algorithm for the preinterventional evaluation of patients with CTO and the current evidence for the clinical effectiveness of the procedure. The proposed care track has been developed by members and with the support of the European Association of Percutaneous Cardiovascular Interventions (EAPCI), the European Association of Cardiovascular Imaging (EACVI), and the European Society of Cardiology (ESC) Working Group on Cardiovascular Surgery.

Long-term improvement of symptoms of angina pectoris after successful revascularization of coronary artery chronic total occlusions

Objectives. To compare long-term angina pectoris relief of successful versus failed percutaneous coronary intervention of chronic total occlusions (CTO PCI). Background. Previous studies demonstrate better short-term angina pectoris relief of CTO PCI than with optimal medical treatment (OMT), however, data on the long-term effects are lacking. Methods. 295 patients undergoing CTO PCI were analyzed retrospectively, with a follow-up evaluation of symptoms of angina pectoris and all-cause death one to four years after the intervention. The primary outcome was long-term relief of symptoms of angina pectoris. Secondary outcomes included a composite of major adverse cardiovascular events (MACE), including all-cause death, myocardial infarction, stroke, and later target vessel revascularization (TVR). At follow-up, patients were interviewed for symptoms of angina pectoris at 1, 6, 12, and 22 to 48 months after the intervention. Results. CTO PCI was successful in 225 (76%) patients and failed in 70 (24%) patients. Short-term (six months) relief of angina pectoris was observed in both groups, but only the successful CTO PCI group showed long-term relief. The Kaplan-Meier curves of all-cause death did not differ between the groups (p = .715). The final follow-up was a mean (range) of 37 (25 to 44) months after the intervention in the successful CTO PCI group, and 33 (28 to 48) months in the failed CTO PCI group. Conclusions. Successful CTO PCI is associated with better long-term relief of symptoms of angina pectoris compared to failed CTO PCI.

Effects of percutaneous coronary intervention on dyspnea in stable coronary artery disease

BACKGROUND

Dyspnea is a frequent symptom in patients with stable coronary artery disease (CAD) and is recognized as a possible angina equivalent.

OBJECTIVES

This study was to assess the impact of percutaneous coronary intervention (PCI) on dyspnea, quality of life, and angina pectoris in patients with stable CAD.

METHODS

The prospective, multi-center PLA-pCi-EBO-pilot trial included 144 patients with symptomatic stable CAD and successful PCI. The prespecified endpoints angina pectoris (Seattle Angina Questionnaire-SAQ) and dyspnea (NYHA scale) were assessed 6 months after PCI. Predictors for symptomatic improvement were assessed with uni- and multivariable logistic regression analyses.

RESULTS

Patients with concomitant dyspnea had worse SAQ physical limitation scores at baseline (49.5 ± 21.0 vs 58.9 ± 22.0, p = 0.013) but showed no difference for angina frequency or quality of life. Overall, symptomatic burden of angina pectoris and dyspnea was alleviated by PCI. However, patients with concomitant dyspnea had markedly worse scores for physical limitation (78.9 ± 25.0 vs 94.3 ± 10.6, p < 0.001), angina frequency (77.9 ± 22.8 vs 91.1 ± 12.4, p < 0.001), and quality of life (69.4 ± 24.1 vs 82.5 ± 14.4, p < 0.001) after PCI. The prevalence of dyspnea (NYHA class ≥ 2) declined from 73% before PCI to 54%. Of 95 initially dyspneic patients, 57 (60%) improved at least one NYHA class 6 months after PCI. In a multivariable logistic regression analysis, "atypical angina pectoris" was associated with improved NYHA class, whereas "diabetes mellitus" had a negative association.

CONCLUSION

PCI effectively reduced dyspnea, which is a frequent and demanding symptom in patients with CAD. The German Clinical Trials Register registration number is DRKS0001752 ( www.drks.de ).

Multiple Biomarkers to Predict Major Adverse Cardiovascular Events in Patients With Coronary Chronic Total Occlusions

Background

There are limited tools available to predict the long-term prognosis of persons with coronary chronic total occlusions (CTO).

Objectives

We evaluated performance of a blood biomarker panel to predict cardiovascular (CV) events in patients with CTO.

Methods

From 1251 patients in the CASABLANCA study, 241 participants with a CTO were followed for an average of 4 years for occurrence of major adverse CV events (MACE, CV death, non-fatal myocardial infarction or stroke) and CV death/heart failure (HF) hospitalization. Results of a biomarker panel (kidney injury molecule-1, N-terminal pro-B-type natriuretic peptide, osteopontin, and tissue inhibitor of metalloproteinase-1) from baseline samples were expressed as low-, moderate-, and high-risk.

Results

By 4 years, a total of 67 (27.8%) MACE events and 56 (23.2%) CV death/HF hospitalization events occurred. The C-statistic of the panel for MACE through 4 years was 0.79. Considering patients in the low-risk group as a reference, the hazard ratio of MACE by 4 years was 6.65 (95% confidence interval [CI]: 2.98-14.8) and 12.4 (95% CI:5.17-29.6) for the moderate and high-risk groups (both P <0.001). The C-statistic for CVD/HF hospitalization by 4 years was 0.84. Compared to the low-risk score group, the moderate and high-risk groups had hazard ratios of 5.61 (95% CI: 2.33-13.5) and 15.6 (95% CI: 6.18, 39.2; both P value <0.001).

Conclusion

A multiple biomarker panel assists in evaluating the risk of adverse outcomes in patients with coronary CTO. These results may have implications for patient care and could have a role for clinical trial enrichment.

Clinical Trial

CASABLANCA, ClinicalTrials.gov Identifier: NCT00842868.

The challenges of a randomised placebo-controlled trial of CTO PCI vs. placebo with optimal medical therapy: The ORBITA-CTO pilot study design and protocol

Background

Percutaneous coronary intervention (PCI) for coronary chronic total occlusion (CTO) has been performed for the improvement of symptoms and quality of life in patients with stable angina. The ORBITA study demonstrated the role of the placebo effect in contemporary PCI in non-CTO chronic coronary syndromes. However, the benefit of CTO PCI beyond that of a placebo has not been demonstrated.

Aims

The ORBITA-CTO pilot study will be a double-blind, placebo-controlled study of CTO PCI randomising patients who have: (1) been accepted by a CTO operator for PCI; (2) experienced symptoms due to a CTO; (3) evidence of ischaemia; (4) evidence of viability within the CTO territory; and (5) a J-CTO score ≤3.

Methods

Patients will undergo medication optimisation that will ensure they are on at least a minimum amount of anti-anginals and complete questionnaires. Patients will record their symptoms on an app daily throughout the study. Patients will undergo randomisation procedures, including an overnight stay, and be discharged the following day. All anti-anginals will be stopped after randomisation and re-initiated on a patient-led basis during the 6-month follow-up period. At follow-up, patients will undergo repeat questionnaires and unblinding, with a further 2-week unblinded follow-up.

Results

The co-primary outcomes are feasibility (blinding) in this cohort and angina symptom score using an ordinal clinical outcome scale for angina. Secondary outcomes include changes in quality-of-life measures, Seattle Angina Questionnaire (SAQ), peak VO2, and anaerobic threshold on the cardiopulmonary exercise test.

Conclusion

The feasibility of a placebo-controlled CTO PCI study will lead to future studies assessing efficacy. The impact of CTO PCI on angina measured using a novel daily symptom app may provide improved fidelity in assessing symptoms in patients with CTO's.

Recanalisation of coronary chronic total occlusions

Percutaneous treatment of coronary chronic total occlusions (CTO) has advanced greatly since its advent in the late 1970s through the development of dedicated wires and microcatheters, the improved skills of highly experienced operators and the adoption of new sophisticated strategies to guide procedural planning. The contemporary procedural success rate is 80-90% with a reduction in complications. Although there has been no improvement in prognosis in randomised trials to date, they, and other controlled registries of thousands of patients, confirm the pivotal role of CTO recanalisation in the treatment of angina and dyspnoea and an improvement in quality of life. Despite this evidence, CTO recanalisation is grossly underutilised. This review reports a detailed overview of the history, indications and treatment strategies for CTO recanalisation and hopes to increase interest among new, and especially young, operators in this demanding, rapidly evolving field of interventional cardiology.

Assessing health-related quality of life among patients with peripheral artery disease: A review of the literature and focus on patient-reported outcome measures

Peripheral artery disease (PAD) is a progressive atherosclerotic disease associated with high rates of morbidity and mortality. Symptomatic PAD typically presents with claudication, and symptom severity strongly associates with reduced health-related quality of life (HRQoL). Existing treatment strategies for PAD are aimed at reducing symptom severity and improving functional outcomes. However, there is a need to incorporate patient-reported outcome measures (PROMs) into PAD treatment and research in order to provide more patient-centered care. This review will discuss the impact of PAD on HRQoL, existing PROMs available to assess PAD-related HRQoL, utilization of PROMs in research studies and registries, and challenges and solutions related to the integration of PROMs into research and clinical settings.

Interpretation of the Seattle Angina Questionnaire as an Outcome Measure in Clinical Trials and Clinical Care: A Review

Importance

Patient-reported outcomes are increasingly used as end points in clinical trials, assessments in clinical care, and tools for population health, with an increasing role in quality assessment. For patients with coronary artery disease, the Seattle Angina Questionnaire (SAQ) has emerged as the most commonly used measure of disease-specific health status to quantify patients' symptoms of angina and the extent to which their angina affects their functioning and quality of life. This review explains how to interpret the SAQ and describes the construction and face validity of the SAQ, focusing on aligning scores and changes in scores with clinical constructs.

Observations

The SAQ asks questions similar to those an experienced clinician would ask of a patient with stable ischemic heart disease. Therefore, SAQ scores can be aligned with clinical constructs (eg, scores on the SAQ angina frequency scale of 0-30 points indicate daily angina, 31-60 points indicate weekly angina, 61-99 points indicate monthly angina, and 100 points indicate no angina), and changes in scores can be described by aligning them with changes in question responses. After clinical thresholds are defined, it is important for clinical trials to not simply report mean differences between treatment arms but to also report the distributions of patients who have had clinically important benefits so that a number needed to treat can be generated.

Conclusions and Relevance

The widespread use of the SAQ is a consequence of its well-established validity, reproducibility, prognostic importance, and sensitivity to clinical change. Nevertheless, interpreting the SAQ can be challenging because of lack of familiarity with the clinical importance of its domains, either cross-sectionally or longitudinally. This review provides an overview of the interpretability of the SAQ as a foundation for its use as an end point in clinical trials, a tool to support more patient-centered care, and a means of facilitating population health strategies to provide a better foundation for the integration of patient experiences with clinical care.

Impact of body mass index on outcome and health status after chronic total occlusion percutaneous coronary intervention: Insights from the OPEN-CTO study

BACKGROUND

The effect of body mass index (BMI) on the procedural outcomes and health status (HS) change after chronic total occlusion (CTO) percutaneous coronary intervention (PCI) is largely unknown.

METHODS

Thousand consecutive patients enrolled in a 12-center prospective CTO PCI study (Outcomes, Patient Health Status, and Efficiency in Chronic Total Occlusion Hybrid Procedures [OPEN-CTO]) were categorized into three groups by baseline BMI (obese ≥30, overweight 25-30, and normal 18.5-25), after excluding seven patients with BMI <18.5. Baseline and follow-up HS at 1 year were quantified using the Seattle Angina Questionnaire, Rose Dyspnea Score, and Personal Health Questionnaire-8 (PHQ-8). Hierarchical, multivariable logistic, and repeated measures linear regression models were used to assess procedural success, major adverse cardiovascular and cerebrovascular events (MACCE), and HS outcomes, as appropriate.

RESULTS

The obese and overweight were 47.6% and 37.4%, respectively. While procedure time and contrast dose were similar among the groups, total radiation dose (mGy) was higher with increased BMI (3,019 ± 2,027, 2,267 ± 1,714, 1,642 ± 1,223, p < .01). Procedural success rates, as well as MACCE rates, were similar among the three groups (obese 83.1%, overweight 79.8%, normal 81.9%, p = .47 and 5.1, 8.4, and 8.7%, p = .11). These rates remained similar after adjustment for baseline characteristics. The HS improvement from baseline to 12 months after adjustment was similar in obese and overweight patients compared to normal weight patients.

CONCLUSIONS

CTO PCI in obese and overweight patients can be performed with similar success and complication rates. Obese and overweight patients derive similar HS benefit from CTO PCI compared to normal weight patients.

Definitions and Clinical Trial Design Principles for Coronary Artery Chronic Total Occlusion Therapies: CTO-ARC Consensus Recommendations

Over the past 2 decades, chronic total occlusion (CTO) percutaneous coronary intervention has developed into its own subspecialty of interventional cardiology. Dedicated terminology, techniques, devices, courses, and training programs have enabled progressive advancements. However, only a few randomized trials have been performed to evaluate the safety and efficacy of CTO percutaneous coronary intervention. Moreover, several published observational studies have shown conflicting data. Part of the paucity of clinical data stems from the fact that prior studies have been suboptimally designed and performed. The absence of standardized end points and the discrepancy in definitions also prevent consistency and uniform interpretability of reported results in CTO intervention. To standardize the field, we therefore assembled a broad consortium comprising academicians, practicing physicians, researchers, medical society representatives, and regulators (US Food and Drug Administration) to develop methods, end points, biomarkers, parameters, data, materials, processes, procedures, evaluations, tools, and techniques for CTO interventions. This article summarizes the effort and is organized into 3 sections: key elements and procedural definitions, end point definitions, and clinical trial design principles. The Chronic Total Occlusion Academic Research Consortium is a first step toward improved comparability and interpretability of study results, supplying an increasingly growing body of CTO percutaneous coronary intervention evidence.

Association of Long-Term Exposure to Particulate Matter and Ozone With Health Status and Mortality in Patients After Myocardial Infarction

BACKGROUND

Long-term exposure to particulate matter <2.5 µm in diameter (PM_2.5) and ozone has been associated with the development and progression of cardiovascular disease and, in the case of PM_2.5, higher cardiovascular mortality. Whether exposure to PM_2.5 and ozone is associated with patients' health status and quality of life is unknown. We used data from 2 prospective myocardial infarction (MI) registries to assess the relationship between long-term PM_2.5 and ozone exposure with health status outcomes 1 year after an MI.

METHODS AND RESULTS

TRIUMPH (Translational Research Investigating Underlying Disparities in Acute Myocardial Infarction) and PREMIER (Prospective Registry Evaluating Myocardial Infarction: Events and Recovery) enrolled patients presenting with MI at 31 US hospitals between 2003 and 2008. One year later, patients were assessed with the disease-specific Seattle Angina Questionnaire, and 5-year mortality was assessed with the Centers for Disease Control's National Death Index. Individual patients' exposures to PM_2.5 and ozone over the year after their MI were estimated from the Environment Protection Agency's Fused Air Quality Surface Using Downscaling tool that integrates monitoring station data and atmospheric models to predict daily air pollution exposure at the census tract level. We assessed the association of exposure to ozone and PM_2.5 with 1-year health status and mortality over 5 years using regression models adjusting for age, sex, race, socioeconomic status, date of enrollment, and comorbidities. In completely adjusted models, higher PM_2.5 and ozone exposure were independently associated with poorer Seattle Angina Questionnaire summary scores at 1-year (β estimate per +1 SD increase =-0.8 [95% CI, -1.4 to -0.3; P=0.002] for PM_2.5 and -0.9 [95% CI, -1.3 to -0.4; P<0.001] for ozone). Moreover, higher PM_2.5 exposure, but not ozone, was independently associated with greater mortality risk (hazard ratio =1.13 per +1 SD [95% CI, 1.07-1.20; P<0.001]).

CONCLUSIONS

In our study, greater exposure to PM_2.5 and ozone was associated with poorer 1-year health status following an MI, and PM_2.5 was associated with increased risk of 5-year death.

Outcomes of Chronic Total Occlusion Percutaneous Coronary Intervention in Patients With Renal Dysfunction

Although contemporary chronic total occlusion (CTO) percutaneous coronary intervention (PCI) is performed with high success rates, 10% to 13% of patients presenting with CTOs have chronic kidney disease (CKD), and the comparative safety, efficacy, and health status benefit of CTO PCI in these patients, has not been well defined. We examined the association of baseline renal function with periprocedural major adverse cardiovascular and cerebral events and health status outcomes in 957 consecutive patients (mean age 65.3 ± 10.3 years, 19.4% women, 90.3% white, 23.6 CKD [estimated glomerular filtration rate {eGFR} < 60]) in the OPEN-CTO (Outcomes, Patients Health Status, and Efficiency in Chronic Total Occlusions Registry) study. Hierarchical multivariable regression models were used to examine the independent association of baseline eGFR with technical success, periprocedural complications and change in health status, using Seattle Angina Questionnaire (SAQ) over 1 year. Crude rates of acute kidney injury were higher (13.5% vs 4.4%, p <0.001) and technical success lower (81.8% vs 88.4%, p = 0.01) in patients with CKD. There were no significant differences in other periprocedural complications. After adjustment for confounding factors, there was no significant association of baseline eGFR with technical success or periprocedural major adverse cardiovascular and cerebral events (death, myocardial infarction, emergent bypass surgery, stroke, perforation), whereas patients with lower eGFR had higher rates of acute kidney injury. The difference in SAQ summary score, between patients on the 10th and 90th percentile for baseline eGFR distribution was not clinically significant (1 month: -0.91; 1 year: -3.06 points). In conclusion, CTO PCI success, complication rates, and the health status improvement after CTO PCI are similar in patients across a range of baseline eGFRs.

Health Status Benefits of Successful Chronic Total Occlusion Revascularization Across the Spectrum of Left Ventricular Function: Insights From the OPEN-CTO Registry

OBJECTIVES

This study sought to describe the association between chronic total occlusion (CTO) revascularization (CTO percutaneous coronary intervention [PCI]) and health status in patients with and without cardiomyopathy.

BACKGROUND

Prior PCI trials for cardiomyopathy have excluded CTO patients. Whether patients with reduced left ventricular ejection fraction (LVEF) receive similar health status benefit from CTO-PCI compared with patients with normal LVEF is unclear.

METHODS

We assessed health status change, using the Seattle Angina Questionnaire (SAQ) Summary, SAQ Angina Frequency, and Rose Dyspnea Scale scores, among patients undergoing successful CTO PCI in the OPEN-CTO (Outcomes, Patient Health Status, and Efficiency in Chronic Total Occlusion) Registry. Participants were classified by LVEF (normal, ≥50%; mild-moderate, 30% to 49%; and severe, <30%), with higher SAQ and lower Rose Dyspnea Scale scores indicating better health status. Differences in 1-year outcomes were compared using hierarchical multivariable regression.

RESULTS

Of 762 patients, 506 (66.4%), 193 (25.3%), and 63 (8.3%) had normal, mild-moderate, and severely reduced LVEF. SAQ Summary score improvements were observed in each group (27.1 ± 20.4, 26.7 ± 21.2, and 20.3 ± 18.1, respectively). Compared with patients with LVEF ≥50%, those with LVEF <30% had less improvement in SAQ Summary Score (-5.2 points; 95% confidence interval: -9.0 to -1.5; p = 0.01) and Rose Dyspnea Scale (+0.5 points; 95% confidence interval: 0.1 to 0.8; p = 0.01), with no difference in odds of angina (odds ratio: 1.3; 95% confidence interval: 0.6 to 3.0; p = 0.48). Health status improvement was similar between patients with LVEF ≥50% and LVEF 30% to 49%.

CONCLUSIONS

Although health status improvement was less in patients with severely reduced LVEF compared with those with normal LVEF, each group experienced large health status improvements after CTO-PCI.

Differences between experienced and recalled breathlessness: a review

PURPOSE OF REVIEW

Experienced breathlessness and recalled breathlessness are two different entities, which may be associated with different factors and might have different impacts on function for the individual. The aim was to review the knowledge from the last 2 years concerning experienced breathlessness and recalled breathlessness and related factors.

RECENT FINDINGS

Experienced breathlessness was most often induced or measured during exercise testing in a lab environment using a modified Borg scale. It was associated with both psychological factors, such as social rejection, presence of others, psychosocial stress and prenatal exposure to stress, as well as physical factors, such as hypoxia and frequent exacerbations.Recalled breathlessness was most often measured in epidemiological studies, most commonly using the modified Medical Research Council scale. It was associated with lung volumes, overweight, exercise training, frailty, smoking, personality traits, behavior and marital and occupational status.

SUMMARY

No studies during the review period had directly compared experienced breathlessness and recalled breathlessness. Several factors were related to either experienced breathlessness or recalled breathlessness but no clear differences between factors were found in this review. There is a need for comparative studies using the same measurement methods and in the same settings in order to examine their relation.

Patient Characteristics Associated With Antianginal Medication Escalation and De-Escalation Following Chronic Total Occlusion Percutaneous Coronary Intervention

Background Prior research has shown that providers may infrequently adjust antianginal medications (AAMs) following chronic total occlusion (CTO) percutaneous coronary intervention (PCI). Patient characteristics associated with AAM titration and the variation in postprocedure AAM management after CTO PCI across hospitals have not been reported. We sought to determine the frequency and potential correlates of AAM escalation and de-escalation after CTO PCI. Methods and Results Using the 12-center OPEN CTO registry (Outcomes, Patient Health Status, and Efficiency iN Chronic Total Occlusion Hybrid Procedures), we assessed AAM use at baseline and 6 months after CTO PCI. Escalation was defined as any addition of a new class of AAM or dose increase, whereas de-escalation was defined as a reduction in the number of AAMs or dose reduction. Angina was assessed 6 months after the index CTO PCI attempt using the Seattle Angina Questionnaire Angina Frequency domain. Potential correlates of AAM escalation (vs no change) or de-escalation (vs no change) were evaluated using multivariable modified Poisson regression models. Adjusted variation across sites was evaluated using median rate ratios. AAMs were escalated in 158 (17.5%), de-escalated in 351 (39.0%), and were unchanged at 6-month follow-up in 392 (43.5%). Patient characteristics associated with escalation included lung disease, ongoing angina, and periprocedural major adverse cardiac and cerebral events (periprocedural myocardial infarction, stroke, death, emergent cardiac surgery, or clinically significant perforation), whereas de-escalation was more frequent among patients taking more AAMs, those treated with complete revascularization, and after treatment of non-CTO lesions at the time of the index procedure. There was minimal variation in either escalation (median rate ratio, 1.11; P=0.36) or de-escalation (median rate ratio, 1.10; P=0.20) compared to no change of AAMs across sites. Conclusions Escalation or de-escalation of AAMs was less common than continuation following CTO PCI, with little variation across sites. Further research is needed to identify patients who may benefit from AAM titration after CTO PCI and develop strategies to adjust these medications in follow-up. Clinical Trial Registration URL: https://www.clinicaltrials.gov . Unique identifier: NCT02026466.