Rationale: The chronotropic index quantifies the proportion of the expected heart rate increase that is attained during exercise. The relationship between the chronotropic index and acute exacerbations of chronic obstructive pulmonary disease (AECOPDs) has not been evaluated. Objectives: To determine whether a higher chronotropic index during a 6-minute walk (CI-6MW) is associated with lower risk of AECOPD and whether the CI-6MW is a marker of susceptibility to adverse effects of metoprolol in chronic obstructive pulmonary disease (COPD). Methods: We analyzed data from the BLOCK COPD (Beta-Blockers for the Prevention of AECOPDs) trial. We used Cox proportional hazards models to investigate the relationship between the CI-6MW and the time to AECOPDs. We also tested for interactions between study group assignment (metoprolol vs. placebo) and the CI-6MW on the time to AECOPDs. Results: Four hundred seventy-seven participants with exacerbation-prone COPD (mean forced expiratory volume in 1 second, 41% of predicted) were included in this analysis. A higher CI-6MW was independently associated with a decreased risk of AECOPDs of any severity (adjusted hazard ratio per 0.1 increase in CI-6MW of 0.88; 95% confidence interval, 0.80-0.96) but was not independently associated with AECOPDs requiring hospitalization (adjusted hazard ratio, 0.94; 95% confidence interval, 0.81-1.05). There was a significant interaction by treatment assignment, and in a stratified analysis, the protective effects of a higher CI-6MW on AECOPDs were negated by metoprolol use. Conclusions: A higher CI-6MW is associated with a decreased risk of AECOPDs and may be an indicator of susceptibility to the adverse effects of metoprolol.

Introduction

Autonomic dysfunction is common in chronic obstructive pulmonary disease (COPD), and worse autonomic function may be a marker of risk for acute exacerbations of COPD (AECOPD). Heart rate variability (HRV) is a measure of autonomic function. Our objective was to test whether lower (worse) HRV is a risk factor for AECOPD.

Methods

We measured standard deviation of normal RR intervals (SDNN) and root mean square of successive RR interval differences (RMSSD) on 10-second electrocardiograms (ECGs) performed at screening and day 42 in participants in the Beta Blockers for the Prevention of Acute Exacerbations of COPD trial ( BLOCK-COPD), a placebo-controlled trial of metoprolol for prevention of AECOPD. We used Cox-proportional hazards models to test if these HRV measures were associated with risk of any AECOPD, and separately, hospitalized AECOPD. We tested associations using baseline HRV measures and incorporating HRV measures from day 42 as a time-varying covariate. We also tested for interactions with metoprolol assignment.

Results

Of 532 trial participants, 529 (forced expiratory volume in 1 second [FEV₁ ]41 ± 16.3 % predicted) were included in this analysis. We did not find a significant association between HRV measures and risk of AECOPD when all participants were analyzed together. There was a significant interaction between RMSSD and assignment to metoprolol on time to first hospitalized AECOPD; in the placebo group greater RMSSD was associated with a lower risk of hospitalized AECOPD (adjusted hazard ratio0.71, 95% confidence interval: 0.52 to 0.96, per 10 ms increase) but there was no association in the metoprolol group.

Conclusions

Autonomic dysfunction as measured by HRV may be a risk factor for AECOPD. Future studies should analyze longer HRV recordings and their performance in broader samples of people with COPD, including those on beta-blockers.

Background

Access to healthcare delivery programs and systems is a primary correlate to the overall health and well-being of Veterans and the general population. Participation in clinical research is a gateway to novel therapies that are intended to address current global health issues. Meeting or exceeding recruitment goals in clinical research is one of the key determinants of the timely and successful completion of a study. The travel and time burdens experienced by study participants are often considered barriers to their enrollment into clinical research. The Department of Veterans Affairs (VA) Cooperative Studies Program (CSP) established a consortium of nine VA medical centers (VAMCs) called the Network of Dedicated Enrollment Sites (NODES). The NODES program provides study site-level expertise and innovative approaches that address challenges to clinical research execution. In alignment with our mission, our program developed an approach to increase study participant access to clinical research through implementing "Mobile Recruitment (MoRe)" units. This manuscript describes the utility and challenges associated with employing this strategy to address three common barriers to clinical research participation: 1) research participant travel burden, 2) participant access to study opportunities, and 3) low participant enrollment.

Methods

A plan to introduce the Mobile Recruitment (MoRe) unit as a recruitment strategy was piloted for a high-volume, observational cohort study and mega biobank in the VA health care system, the "Million Veteran Program (MVP)". MoRe is a recruitment strategy for CSP research integrating mobile technology and atypical research recruitment locations. Recruitment locations include primary or main VA hospitals and their assigned VA Community-Based Outpatient Clinics (CBOCs). Each Node site (n = 9) received components of the MoRe unit including a laptop, printer, portable cart with storage space, cooler/ice packs for specimen storage and transport. Each site's usage of these components varied based on its respective needs. Activities focused on both VA main facilities and CBOC facilities for recruitment.

Results

Seven of the nine Node sites compared the effectiveness of the MoRe unit on MVP study enrollment outcomes over three-time points: pre-intervention period, intervention period, and post-intervention period. The utilization of MoRe in the intervention period demonstrated a 36.9% increase in enrollment compared to the previous six months (pre-intervention period). There was a 2% enrollment increase at the six-month post-intervention period as compared to the intervention period. When comparing the pre-intervention period to the post-intervention period (duration of eighteen months), enrollment increased by 38.9%.

Conclusion

Five of the seven sites experienced an increase in enrollment during the intervention and post-intervention periods. The two sites without an increase in enrollment experienced various extenuating factors. Characteristics of sites using MoRe included the ability to utilize a smaller, unconventional space, i.e. not a traditional clinical research exam space for recruitment. MoRe was utilized in hospital laboratory space, CBOCs, primary care clinics, and other subspecialty clinics that allowed recruitment activities but did not have dedicated space to offer the research teams for that purpose. This initiative successfully demonstrated the benefit of deploying the unit, proving its utility in cases in where there was a lack of space or alternative workstations for research activities. The implementation of MoRe by NODES as a recruitment strategy for MVP may be transferable to other VA clinical research studies, as well as to other healthcare settings executing similar clinical research activities.

Background

Few studies have examined the efficacy of drug-eluting stents (DES) for reducing aortocoronary saphenous vein bypass graft (SVG) failure compared with bare-metal stents (BMS) in patients undergoing stenting of de-novo SVG lesions. We assessed the risks and benefits of the use of DES versus BMS in de-novo SVG lesions.

Methods

Patients were recruited to our double-blind, randomised controlled trial from 25 US Department of Veterans Affairs centres. Eligible participants were aged at least 18 years and had at least one significant de-novo SVG lesion (50-99% stenosis of a 2·25-4·5 mm diameter SVG) requiring percutaneous coronary intervention with intent to use embolic protection devices. Enrolled patients were randomly assigned, in a 1:1 ratio, by phone randomisation system to receive a DES or BMS. Randomisation was stratified by presence or absence of diabetes and number of target SVG lesions requiring percutaneous coronary intervention (one or two or more) within each participating site by use of an adaptive scheme intended to balance the two stent type groups on marginal totals for the stratification factors. Patients, referring physicians, study coordinators, and outcome assessors were masked to group allocation. The primary endpoint was the 12-month incidence of target vessel failure, defined as the composite of cardiac death, target vessel myocardial infarction, or target vessel revascularisation. The DIVA trial is registered with ClinicalTrials.gov, number NCT01121224.

Findings

Between Jan 1, 2012, and Dec 31, 2015, 599 patients were randomly assigned to the stent groups, and the data for 597 patients were used. The patients' mean age was 68·6 (SD 7·6) years, and 595 (>99%) patients were men. The two stent groups were similar for most baseline characteristics. At 12 months, the incidence of target vessel failure was 17% (51 of 292) in the DES group versus 19% (58 of 305) in the BMS group (adjusted hazard ratio 0·92, 95% CI 0·63-1·34, p=0·70). Between-group differences in the components of the primary endpoint, serious adverse events, or stent thrombosis were not significant. Enrolment was stopped before the revised target sample size of 762 patients was reached.

Interpretation

In patients undergoing stenting of de-novo SVG lesions, no significant differences in outcomes between those receiving DES and BMS during 12 months of follow-up were found. The study results have important economic implications in countries with high DES prices such as the USA, because they suggest that the lower-cost BMS can be used in SVG lesions without compromising either safety or efficacy.

Funding

US Department of Veterans Affairs Cooperative Studies Program.