Rheumatoid arthritis (RA) is a systemic inflammatory disease that affects \~1% of the population. Regardless of the novel therapies developed in the last decades, studies report an increased standard mortality ratio as high as 3.0 when compared with the general population. Cardiovascular disease (CVD) is the leading cause of mortality in RA subjects in whom the average lifespan is reduced by 8-15 years compared to matched controls. RA patients are at increased risk for developing heart failure and inflammatory myocarditis potentially contributes to this excess risk. Although subclinical myocarditis remains poorly characterized to date in RA, costimulatory molecules such as CD80/86 (B7s) and CD40 are known to play a pivotal role for cytokine production and antigen-specific T cell activation in viral myocarditis, and in murine models, blocking CD40L/B7-1 and CTLA4 significantly decreases myocardial inflammation, damage, and mortality. In addition, the recent increase in the use of immune checkpoint inhibitors for the treatment of numerous cancers, has raised awareness of the occurrence of fulminant autoimmune lymphocytic myocarditis as a complication of these drugs including anti-CTLA4 due to a presumed uncontrolled immune response resulting in T-cell mediated myocardial injury. Interestingly, pilot data showed lower myocardial FDG uptake in RA patients on the a CTLA4-Ig fusion protein abatacept compared with other DMARDs. These data raise the possibility of immunotherapy for the treatment of myocarditis in RA, suggesting a role for T cell infiltration in its pathogenesis, and a particular benefit for treatment with abatacept vs non-abatacept biologic DMARDs.

In a single RHeumatoid arthritis studY of THe Myocardium (RHYTHM study), a total of 119 RA patients without clinical CVD underwent cardiac FDG-PET/CT, with myocardial inflammation assessed qualitatively and quantitatively by visual inspection and by calculation of the standardized-uptake-value (SUV) units. Qualitative myocardial FDG uptake was observed in 39% of the patients. Animal data showing decreased myocardial inflammation, damage, and mortality, and improved cardiac function with CD40L/B7-1 and CTLA4 blockage, coupled with preliminary findings of lower myocardial inflammation in RA patients on abatacept vs other DMARDs, suggest that abatacept treatment has potential myocardial benefits. In RA patients, the proportion of peripheral T cell subsets significantly differs from normal controls and include differentiation to memory effector subsets, acquisition of natural killer (NK) receptors, exhaustion markers, and enhanced inflammatory cytokine expression. Importantly, T cell lymphocytic infiltration described in autoimmune myocarditis resulting as a complication of CTLA4 immune checkpoint inhibition, suggests a role for T cell subsets in the pathogenesis of myocarditis in RA with potential differences depending on mechanism of action of the DMARD in use. Studies that investigate the impact of treatment on subclinical myocarditis in RA, a possible contributor to heart failure, while exploring potential underlying mechanisms (i.e., different T cell subpopulations), are needed for a better understanding of their relevance in the pathogenesis of heart failure in RA and survival improvement in these patients with excess risk for cardiovascular death. If the investigator hypothesis is confirmed and treatment with abatacept decreases and/or suppresses or prevents myocardial inflammation in RA, this will have multidisciplinary implications that could lead to changes in the current management of RA patients at high risk for cardiovascular events. Similarly, identification of T cell subpopulations in RA patients with myocardial FDG uptake will shed light into the underlying cellular mechanisms of myocardial injury and serve to guide the use of therapies that prevent their pathogenicity.

This is a single-center study. Twenty RA patients will be recruited over a planned recruitment period of 24 months, and randomized with aims of enrolling 10 patients per year, the enrollment rate is estimated as 1 patient per month. The target population consists of patients who are deemed methotrexate-inadequate responders by the patient's treating rheumatologist, and who have not yet stepped up to additional treatment with a biologic DMARD.