Left Ventricular Dysfunction Among Patients With Embolic Stroke of Undetermined Source and the Effect of Rivaroxaban vs Aspirin: A Subgroup Analysis of the NAVIGATE ESUS Randomized Clinical Trial

Key Points

Question  Is anticoagulation superior to aspirin in reducing recurrent stroke in patients with recent embolic stroke of undetermined source (ESUS) and left ventricular (LV) dysfunction?

Findings  Among 7213 participants of the New Approach Rivaroxaban Inhibition of Factor Xa in a Global Trial vs Aspirin to Prevent Embolism in ESUS (NAVIGATE ESUS) trial, 502 (7.1%) had evidence of LV dysfunction. Participants with LV dysfunction assigned to rivaroxaban vs aspirin had a lower risk of recurrent stroke or systemic embolism compared with those without LV dysfunction.

Meaning  Rivaroxaban was superior to aspirin at reducing the risk of recurrent stroke or systemic embolism among NAVIGATE ESUS participants with LV dysfunction in this post hoc exploratory analysis.

Importance  It is uncertain whether anticoagulation is superior to aspirin at reducing recurrent stroke in patients with recent embolic strokes of undetermined source (ESUS) and left ventricular (LV) dysfunction.

Objective  To determine whether anticoagulation is superior to aspirin in reducing recurrent stroke in patients with ESUS and LV dysfunction.

Design, Setting, and Participants  Post hoc exploratory analysis of data from the New Approach Rivaroxaban Inhibition of Factor Xa in a Global Trial vs Aspirin to Prevent Embolism in ESUS (NAVIGATE ESUS) trial, a randomized, phase 3 clinical trial with enrollment from December 2014 to September 2017. The study setting included 459 stroke recruitment centers in 31 countries. Patients 50 years or older who had neuroimaging-confirmed ESUS between 7 days and 6 months before screening were eligible. Of the 7213 NAVIGATE ESUS participants, 7107 (98.5%) had a documented assessment of LV function at study entry and were included in the present analysis. Data were analyzed in January 2021.

Interventions  Participants were randomized to receive either 15 mg of rivaroxaban or 100 mg of aspirin once daily.

Main Outcomes and Measures  The study examined whether rivaroxaban was superior to aspirin at reducing the risk of (1) the trial primary outcome of recurrent stroke or systemic embolism and (2) the trial secondary outcome of recurrent stroke, systemic embolism, myocardial infarction, or cardiovascular mortality during a median follow-up of 10.4 months. LV dysfunction was identified locally through echocardiography and defined as moderate to severe global impairment in LV contractility and/or a regional wall motion abnormality. A Cox proportional hazards model was used to assess for treatment interaction and to estimate the hazard ratios for those randomized to rivaroxaban vs aspirin by LV dysfunction status.

Results  LV dysfunction was present in 502 participants (7.1%). Of participants with LV dysfunction, the mean (SD) age was 67 (10) years, and 130 (26%) were women. Among participants with LV dysfunction, annualized primary event rates were 2.4% (95% CI, 1.1-5.4) in those assigned to rivaroxaban vs 6.5% (95% CI, 4.0-11.0) in those assigned aspirin. Among the 6605 participants without LV dysfunction, rates were similar between those assigned to rivaroxaban (5.3%; 95% CI, 4.5-6.2) vs aspirin (4.5%; 95% CI, 3.8-5.3). Participants with LV dysfunction assigned to rivaroxaban vs aspirin had a lower risk of the primary outcome (hazard ratio, 0.36; 95% CI, 0.14-0.93), unlike those without LV dysfunction (hazard ratio, 1.16; 95% CI, 0.93-1.46) (P for treatment interaction = .03). Results were similar for the secondary outcome.

Conclusions and Relevance  In this post hoc exploratory analysis, rivaroxaban was superior to aspirin in reducing the risk of recurrent stroke or systemic embolism among NAVIGATE ESUS participants with LV dysfunction.

Trial Registration  ClinicalTrials.gov Identifier: NCT02313909

Approximately 2 million ischemic strokes that occur each year worldwide lack an identifiable cause.¹ These strokes are classified as cryptogenic and represent approximately 17% of all ischemic strokes.² A subset of cryptogenic strokes often appear to be embolic and are referred to as embolic strokes of undetermined source (ESUS).³Quiz Ref ID Two recent randomized clinical trials (the New Approach Rivaroxaban Inhibition of Factor Xa in a Global Trial vs Aspirin to Prevent Embolism in ESUS [NAVIGATE ESUS] trial and the Dabigatran Etexilate for Secondary Stroke Prevention in Patients With Embolic Stroke of Undetermined Source [RESPECT-ESUS] trial) found that anticoagulation was no better than aspirin at reducing the risk of recurrent stroke and systemic embolism among all patients with ESUS.^4,5 However, patients included in these trials had heterogeneous potential etiologies of ESUS,⁶ and anticoagulation was not an effective overarching treatment strategy for this undifferentiated population.⁷

There are several well-established, albeit infrequent, sources of cardiac embolism and subsequent stroke that arise from the left ventricle (LV), such as those resulting from recent acute myocardial infarction or severe LV systolic dysfunction.^3,8 On the other hand, LV regional wall motion abnormalities and impaired LV contractility are commonly found in patients with ESUS and may similarly have the propensity to lead to thrombus formation, cardiac embolism, and stroke.^9,10 These forms of LV dysfunction, however, are not currently considered high-risk sources of cardiac embolism. As a result, patients with stroke who have these abnormalities are considered to have ESUS and are not routinely prescribed anticoagulation.³ In this post hoc exploratory analysis, we hypothesized that anticoagulation would be superior to antiplatelet therapy in reducing the risk of cardiac embolism and subsequent stroke in patients with ESUS and evidence of LV dysfunction. We evaluated this hypothesis among the participants included in the NAVIGATE ESUS trial.

This study was a post hoc exploratory analysis of the NAVIGATE ESUS trial data. NAVIGATE ESUS was an international, multicenter phase 3 trial in which patients with recent ESUS were randomly assigned (double-blind) to either 15 mg of rivaroxaban or 100 mg of aspirin once daily for the prevention of recurrent stroke. The design, rationale, baseline patient characteristics, and primary results of the trial have been previously published.^4,11 Trial enrollment took place from December 2014 to September 2017, and data were analyzed in January 2021. The study setting included 459 stroke recruitment centers in 31 countries. The mean (SD) age of participants was 67 (10) years, and 4436 participants (61.5%) were male. Of the 7213 NAVIGATE ESUS participants, 7107 (98.5%) had a documented assessment of LV function at study entry and were included in the present analysis. All patients provided written informed consent before participation. The protocol was approved by the institutional review board at each trial site, and the study followed the Consolidated Standards of Reporting Trials (CONSORT) reporting guideline.

Quiz Ref IDPatients with ischemic stroke confirmed by cerebral imaging within 7 days to 6 months of symptom onset were eligible to participate in NAVIGATE ESUS. The qualifying ischemic stroke was considered to be ESUS if it was (1) not lacunar; (2) not associated with more than 50% luminal stenosis of the artery supplying the area of ischemia; (3) not associated with identified high-risk sources of cardiac embolism, including atrial fibrillation, LV thrombus, mechanical cardiac valve, or severe mitral stenosis; and (4) no other source of stroke was identified by the time of randomization.⁴ In addition, participants were required to be older than 49 years at the time of stroke. If participants were aged 50 to 59 years at the time of stroke, at least 1 additional risk factor for stroke was necessary, defined as previously reported.⁴

For this post hoc exploratory analysis of NAVIGATE ESUS, all participants with a documented assessment of LV function via transthoracic echocardiogram or transesophageal echocardiogram were included. Global LV contractility was graded as normal, mildly impaired, moderate to severely impaired, or uncertain. If the global assessment of LV contractility was marked as uncertain or not reported, an LV ejection fraction less than 40% was used to define global moderate to severely impaired LV contractility. While LV ejection fraction is the most commonly used method for the assessment of LV systolic function, it is influenced by LV loading conditions. In contrast, LV intrinsic contractility is not an afterload-dependent measure and thus provides a more complete characterization of LV function.^12,13 Regional wall motion abnormalities were noted as either present, absent, or not reported. Echocardiograms were performed at participating sites, and case report forms were filled out by local investigators.

In this analysis, participants were considered to have LV dysfunction if they had moderate to severely impaired global LV contractility and/or a regional wall motion abnormality. We considered any degree or type of wall motion abnormality to be indicative of LV dysfunction. These markers of LV dysfunction were selected because they had been previously found to be associated with LV thrombus formation and stroke.^9,10 We defined LV dysfunction status a priori into the following 3 mutually exclusive categories: (1) normal to mildly impaired LV contractility without regional wall motion abnormalities noted, (2) normal to mildly impaired LV contractility with regional wall motion abnormalities noted, and (3) moderate to severely impaired LV contractility with or without regional wall motion abnormalities. We considered categories 2 and 3 to constitute LV dysfunction.

Quiz Ref IDThe primary outcome of this study was the primary efficacy outcome of the trial: the composite end point of recurrent stroke or systemic embolism. The specific definitions of the components of the primary outcome based on clinical and radiographic findings have been previously described.^4,11 In brief, ischemic stroke recurrence was defined as a sudden focal neurological deficit due to arterial occlusion and persisting for more than 24 hours without evidence of primary hemorrhage on brain imaging. If neurological deficits lasted less than 24 hours, evidence of acute brain infarction was necessary by neuroimaging. Hemorrhagic strokes included symptomatic nontraumatic intracerebral and subarachnoid hemorrhage. The secondary outcome of this study was the main secondary efficacy outcome of the trial; that is, the composite of first recurrent stroke, systemic embolism, myocardial infarction, or death from cardiovascular causes. The safety outcome of interest of this study was the trial primary safety outcome, specifically major bleeding according to International Society of Thrombosis and Hemostasis criteria.¹⁴ All outcomes were centrally adjudicated, and reviewers were blinded to the treatment assignments.

Analyses were performed on the intention-to-treat population. Participant characteristics at study entry were described using means with SDs for continuous variables and proportions for discrete variables. To describe time-to-event data, annualized event rates were calculated by dividing the number of participants with an event by the total number of patient years of observation with CIs estimated by assuming a Poisson distribution. Kaplan-Meier curves are also presented. To describe the relative risk of outcome by assigned treatment, hazard ratios (HRs) and 95% CIs from the Cox proportional hazards model were computed. Heterogeneity of treatment effect across LV dysfunction groups was assessed by the statistical significance of the interaction term in the model after adjusting for main effects. A sensitivity analysis was planned a priori to adjust the model for any imbalance of baseline characteristics across assigned treatment groups. All reported P values were 2-sided, and significance was set at P < .05. Statistical analysis was done using SPSS for Windows version 27.0.1 (IBM Corp) and MedCalc Statistical Software version 19.6.4 (MedCalc Software Ltd).

Among the 7213 participants of NAVIGATE ESUS, 7107 (98.5%) had a documented assessment of LV function and were included in this exploratory analysis (Figure 1). A total of 4374 of 7107 participants with LV dysfunction (62%) were male. The mean (SD) age of participants with LV dysfunction was 67 (10) years. Of the 7107 participants in this analysis, 5504 (77%) had hypertension, and 594 (8%) had a history of coronary artery disease. Participants excluded from the analysis had similar demographic characteristics and factors associated with vascular disease compared with participants included (eTable 1 in the Supplement).

Among the 7107 participants, 502 (7%) had LV dysfunction reported. Of the 502, 405 (81%) had normal to mildly impaired LV contractility with a regional wall motion abnormality, while 97 (19%) had moderate to severely impaired LV contractility with or without a regional wall motion abnormality. Normal to mildly impaired LV contractility without a regional wall motion abnormality was observed in 6605 patients (93%). Quiz Ref IDPatients with evidence of LV dysfunction were more likely to be male, have coronary artery disease, and have a history of stroke or transient ischemic attack prior to the qualifying stroke compared with those without LV dysfunction (Table 1).

Over a median (IQR) follow-up of 10.4 (5.2-17.0) months, the primary outcome of recurrent stroke or systemic embolism occurred in 321 (4.9% per year) of the 7107 participants included in the analysis: 299 had ischemic strokes, 15 hemorrhagic strokes, 4 unknown strokes, and 3 systemic emboli.

The overall annualized rates of the primary outcome did not differ appreciably across the 3 LV dysfunction categories (Table 2). Although not prespecified in our analysis plan, because of the small number of observed events in the 2 groups having prespecified LV dysfunction (14 of 405 individuals with normal to mildly impaired contractility with regional wall motion abnormality noted and 8 of 97 individuals with moderate to severely impaired contractility with or without regional wall motion abnormality noted), these 2 groups were combined prior to performing subsequent analyses (n = 502; 22 events).

Among the 7107 participants, 167 participants assigned to rivaroxaban vs 154 participants assigned to aspirin experienced the primary outcome (5.1% vs 4.7% per year, respectively). For the 502 participants (7.1%) with LV dysfunction, rates were 2.4% per year (95% CI, 1.1-5.4) in those assigned to rivaroxaban vs 6.5% (95% CI, 4.0-11) in those assigned to aspirin (Table 2). In contrast, among the 6605 participants without LV dysfunction, annualized primary event rates were similar between those assigned to rivaroxaban (5.3% per year; 95% CI, 4.5-6.2) vs aspirin (4.5% per year; 95% CI, 3.8-5.3) (Table 2; Figure 2). This observed heterogeneity of treatment effect was statistically significant (P = .03 for interaction) after adjusting for the main effects of assigned treatment and LV dysfunction. Participants with LV dysfunction randomized to rivaroxaban vs aspirin had a significantly lower risk of the primary outcome (HR, 0.36; 95% CI, 0.14-0.93), whereas those without LV dysfunction had similar risk (HR, 1.16; 95% CI, 0.93-1.46).

Of the 15 patients with a hemorrhagic stroke as the primary outcome, 1 occurred in the 502 patients with LV dysfunction (0.2%), while 14 occurred in the 6605 patients with normal to mildly impaired LV contractility without regional wall motion abnormality noted (0.2%). Of the 14 occurring in this latter group, 12 occurred in participants assigned to rivaroxaban and 2 occurred in participants assigned to aspirin.

A total of 390 of 7107 participants (5.5%) experienced a secondary outcome. Secondary event rates were similar across LV function groups with participants in the normal to mildly impaired LV contractility with a regional wall motion abnormality group and in the moderate to severely impaired LV contractility with or without a regional wall motion abnormality group having a limited number of events (Table 3). For this reason, although not prespecified in our analysis plan, we again combined the 2 LV dysfunction groups (n = 502; 35 events) before performing additional analysis.

Among the 7107 participants, 201 assigned to rivaroxaban vs 189 assigned to aspirin experienced a secondary outcome (6.1% vs 5.7% per year, respectively). For the 502 participants with LV dysfunction (7.1%), rates were 4.9% per year (95% CI, 2.8-8.6) in those assigned to rivaroxaban vs 9.5% per year (95% CI, 6.3-14) in those assigned to aspirin (Table 3). In contrast, among the 6605 participants without LV dysfunction, annualized primary event rates were similar between those assigned to rivaroxaban (6.2% per year; 95% CI, 5.4-7.1) vs aspirin (5.4% per year; 95% CI, 4.7-6.3) (Table 3). After adjusting for main effects of assigned treatment and LV dysfunction status, the P value for interaction for treatment effect was .05. Participants with LV dysfunction assigned to rivaroxaban had a lower risk of experiencing the secondary outcome compared with those assigned to aspirin (HR, 0.51; 95% CI, 0.3-1.0) whereas there was no significant difference by assigned treatment among those without LV dysfunction (HR, 1.1; 95% CI, 0.9-1.4).

A major bleeding event occurred in 83 of the 7107 participants. Nearly 95% (n = 78) of events occurred in participants without evidence of LV dysfunction (55 assigned to rivaroxaban and 23 assigned to aspirin) with the remaining 5 occurring in participants with evidence of LV dysfunction (5 assigned to rivaroxaban and 0 assigned to aspirin).

Baseline characteristics of participants with LV dysfunction appeared similar across assigned treatment groups with the exception that those randomized to rivaroxaban were less likely to have diabetes (23% vs 35%; eTable 2 in the Supplement). After adjusting for the main effects of diabetes in addition to assigned treatment and LV dysfunction status in a Cox proportional hazard model, the heterogeneity of treatment effect with LV dysfunction remained (P = .04 for interaction). Among participants with LV dysfunction, after adjusting for diabetes, rivaroxaban remained associated with a lower risk of the primary outcome (HR, 0.35; 95% CI, 0.14-0.9).

Quiz Ref IDIn this exploratory analysis of the NAVIGATE ESUS trial, rivaroxaban was associated with a reduced risk of recurrent stroke or systemic embolism compared with aspirin among the 7% of participants with reported LV dysfunction.

The results of this study should be considered in the context of prior studies evaluating the optimal antithrombotic therapy for patients with ESUS. Two randomized clinical trials have concluded that anticoagulation is not superior to antiplatelet therapy among all patients with ESUS^4,5; however, the etiologies of ESUS in these trials were heterogeneous, and the risk of recurrent stroke among patients without sources of cardiac embolism may not necessarily be reduced by anticoagulation.⁷ Certain rare forms of LV dysfunction, such as recent acute myocardial infarction or severe LV systolic dysfunction, are considered to be high-risk cardioembolic sources of stroke that respond to anticoagulation.^3,8,15,16 Other more common forms of LV dysfunction, including impaired LV contractility or regional wall motion abnormalities, are not currently considered high-risk sources of cardiac embolism and yet appear to be associated with LV thrombus formation and recurrent stroke.^9,10 A previously published subgroup analysis of NAVIGATE ESUS reported that rivaroxaban was not superior to aspirin in participants with any type of LV disease. In that analysis, LV disease was liberally defined to include diastolic dysfunction and LV hypertrophy, neither of which has been found to be associated with cardiac embolism, and 36% of participants met this broad definition.⁶ Rather than evaluating all types of LV disease, we tested the hypothesis that specific forms of LV dysfunction previously found to be associated with LV thrombus formation and stroke would respond to anticoagulation.^9,10 In this context, our results provide novel data suggesting that ESUS patients with evidence of impaired LV contractility and/or regional wall motion abnormalities may benefit from anticoagulation.

Impaired LV contractility and/or regional wall motion abnormalities may be an independent risk factor for recurrent ischemic stroke. Impaired LV contractility and regional wall motion abnormalities are prevalent in patients with stroke.^9,17 In NAVIGATE ESUS, 7% of participants had evidence of this type of LV dysfunction. Other studies have suggested that these common forms of LV dysfunction may pose a relatively similar risk of thrombus formation and stroke compared with more severe but rarer forms of LV dysfunction, such as acute myocardial infarction or severely depressed ejection fraction (less than 30%).¹⁸ A prior study evaluating the use of cardiac magnetic resonance imaging in patients with stroke found that 40% of LV thrombi were detected in patients who had an ejection fraction greater than 30% and that most of these thrombi were not visualized by standard transthoracic echocardiogram.¹⁰ Another study demonstrated that regional wall motion abnormalities were independently associated with a 1.7-fold increased risk of recurrent stroke.⁹ Taken together, these data suggest that certain forms of LV dysfunction, including impaired LV contractility and regional wall motion abnormalities may be associated with LV thrombus formation and recurrent ischemic stroke.

Secondary stroke prevention guidelines remain noncommittal regarding the treatment of patients who have had stroke and who have LV dysfunction, including depressed LV ejection fraction, impaired LV contractility, and regional wall motion abnormalities.^19,20 As far back as 2012, the double-blind, multicenter Warfarin and Aspirin in Patients With Heart Failure and Sinus Rhythm (WARCEF) study demonstrated a reduced risk of ischemic stroke, albeit offset by an increased risk of major hemorrhage, for participants with an ejection fraction less than 35% who were assigned to warfarin vs aspirin.²¹ A recent meta-analysis of 5 randomized clinical trials (including WARCEF) of patients with heart failure with an ejection fraction less than 35% to 40% demonstrated that anticoagulation was superior to aspirin and placebo at reducing risk of ischemic stroke risk during follow-up (HR, 0.63; 95% CI, 0.49-0.81).²² Despite the heightened propensity for thrombus formation in patients with depressed LV ejection fraction, the American Heart Association/American Stroke Association Guidelines and Canadian Stroke Best Practice Recommendations are equivocal with regard to the optimal secondary stroke prevention therapy in this population, likely owing to the lack of level 1 evidence from a dedicated trial of secondary stroke prevention in patients with LV dysfunction and excess reported rates of major bleeding.^19,20 To our knowledge, there are no recommendations or guidelines regarding use of anticoagulation for patients with impaired LV contractility or segmental wall motion abnormalities. Additionally, the high risk of bleeding found in older trials, such as WARCEF, may be offset by the use of novel anticoagulants, which have a more favorable risk-benefit profile compared with warfarin.²³ The results of this study may therefore provide the rationale and justification for a randomized clinical trial evaluating the efficacy of anticoagulation compared with antiplatelet therapies in reducing recurrent stroke risk in patients with recent stroke and evidence of LV dysfunction.

There are several limitations to this study. Most importantly, this was an exploratory analysis in the setting of a negative overall trial, and our results should be considered hypothesis generating. In addition, determination of LV dysfunction was not standardized across all participating sites, and there was no requirement to document echocardiographic parameters. Furthermore, we lacked granular data on the presence or extent of myocardial scar, which may serve as a nidus for thrombus formation and affect the propensity of cardiac embolism. We may also have been limited in our ability to detect associations because of the relatively small number of participants with LV dysfunction (7%).

In this analysis, we found that rivaroxaban, a factor Xa inhibitor, was superior to aspirin in reducing recurrent stroke or systemic embolism among patients with recent ESUS and evidence of LV dysfunction. A dedicated secondary stroke prevention trial in patients with LV dysfunction should be considered to evaluate the efficacy and safety of anticoagulation to prevent cardiac embolism and subsequent stroke.

Accepted for Publication: August 30, 2021.

Published Online: October 25, 2021. doi:10.1001/jamaneurol.2021.3828

Corresponding Author: Alexander E. Merkler, MD, MS, Department of Neurology, Weill Cornell Medical College, 525 E 68th St, Room F610, New York, NY 10065 (alm9097@med.cornell.edu).

Author Contributions: Drs Kamel and Sharma had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Merkler, Shoamanesh, Birnbaum, Sheth.

Acquisition, analysis, or interpretation of data: Pearce, Kasner, Shoamanesh, Kamel, Sharma.

Drafting of the manuscript: Merkler, Sharma.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Pearce.

Administrative, technical, or material support: Birnbaum.

Supervision: Sheth, Sharma.

Conflict of Interest Disclosures: Dr Merkler reports grants from the American Heart Association during the conduct of the study and has served as an expert witness regarding neurological disorders outside the submitted work. Dr Kasner reports grant support from Bayer during the conduct of the study and grant support from W.L. Gore & Associates, Medtronic, Genentech, and Bristol-Myers Squibb; consulting fees from Medtronic, Bristol-Myers Squibb, and Abbott; and royalties from UpToDate outside the submitted work. Dr Shoamanesh reports grant support from Bayer during the conduct of the study and grant support from Bayer, Daiichi Sankyo Company, Bristol-Myers Squibb, Servier Canada, Portola Pharmaceuticals, and Octapharma and consulting fees from Bayer, Daiichi Sankyo Company, and Servier Canada outside the submitted work. Dr Kamel serves as co–principal investigator for the National Institutes of Health–funded ARCADIA trial, which receives in-kind study drugs from the Bristol-Myers Squibb–Pfizer Alliance for Eliquis and ancillary study support from Roche Diagnostics; serves as Deputy Editor for JAMA Neurology; as a steering committee member of Medtronic’s Stroke AF trial (uncompensated); serves on an end point adjudication committee for a trial of empagliflozin for Boehringer-Ingelheim; and has served on an advisory board for Roivant Sciences related to Factor XI inhibition outside the submitted work. Dr Sheth reports grants from Hyperfine Research Inc, Bard, Biogen, and Novartis; personal fees from Zoll for service as chair of the data and safety monitoring board; personal fees from Ceribell and NControl; and other support from Alva outside the submitted work. No other disclosures were reported.

Funding/Support: Dr Merkler is supported by American Heart Association grant 18CDA34110419. Dr Kamel is supported by National Institutes of Health grants K23NS082367, R01NS097443, and U01NS095869, as well as the Michael Goldberg Research Fund. Dr Sheth is supported by National Institutes of Health grants U24NS107136, U24NS107215, R01NR018335, R01NS107215, U01NS106513, and R03NS112859 and American Heart Association grants 18TPA34170180 and 17CSA33550004.

Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Additional Contributions: We thank Kelsey Lansdale, BS, and Natalie LeMoss, BS, for their administrative assistance.