LAUSR

There are reasons to pursue the study of myocardial blood flow and its alterations in patients with rheumatic diseases (RDs) not the least of which is the fact that cardiovascular (CV) disease is a leading cause of morbidity and mortality in patients with RDs. Findings in RDs include endothelial dysfunction, arterial stiffness, and accelerated atherosclerosis. For example, Mehta et al. identified 3603 subjects with severe psoriasis in the U.K. General Practice Research Database and compared cardiovascular outcomes to a control group (4 subjects for each psoriasis subject) of 14,330 individuals from the same database. They found that the adjusted hazard ratio for CV mortality was 1.57 in those with severe psoriasis compared to controls. The risk was independent of conventional risk factors. The adjusted relative risk of CV mortality was age related, RR 2.7 for a 40yo patient with severe psoriasis compared to a 1.9 for a 60yo patient with severe psoriasis. The same group also showed that the risk of CV mortality in patients with mild psoriasis was no different than that of the controls. In a meta-analysis of patients with rheumatoid arthritis, Avina-Zubieta et al. concluded that there was a 68% increase in the risk of myocardial infarction and stroke with RR of 1.93 and 1.67 in women and men, respectively. Furthermore, there was an 87% increase in the risk of congestive heart failure in patients with RA. In addition, it appeared that patients with RA presented with more multivessel disease at the time of their initial diagnosis of CAD compared to matched controls in a case–control study done in Olmsted County, Minnesota. The impact of RDs on coronary events was independent of traditional risk factors. Survival probability was lower for patients with CAD and rheumatoid arthritis than for those with CAD and no RA. RDs are characterized by autoimmunity and inflammation, and the now accepted role of inflammation in both the development of coronary plaque and the instability of coronary plaque has led to increased interest in the RDs as models of inflammation and plaque development. Understanding the mechanisms by which inflammation participates in the early and more severe appearance of CAD and in the development of HFpEF may inform our approach to the mitigation of atherosclerotic diseases and heart failure in patients with and without RDs. One line of investigation into the effects of RDs on vascular biology has been the study of myocardial blood flow(MBF). Multiple modalities have been used to study MBF in patients with RDs, including coronary doppler velocity with transthoracic echo, PET tracer kinetics with NH3, Rb, and O water and MRI contrast kinetics. However, it must be said at the outset that MBF, especially hyperemic MBF, and myocardial or coronary flow reserve, MFR or CFR, may be affected by a variety of factors that can confound the interpretation of results and which are difficult or impossible to control especially in retrospective studies. Table 1 is a partial list of the factors that have been identified that can alter MBF. So, one must be cautious entering those waters, so as not to reach conclusions that will not hold up to independent confirmation. Those precautions notwithstanding, Weber et al., in this issue of the Journal, present a retrospective study of 62 consecutive patients studied with NH3 or Rb PET MPI over a 13-year period. All data were acquired on a PET/CT system with a 64-slice CT scanner that allowed for semi-quantitative estimation of the extent and severity of coronary artery calcification. Control patients included 112 individuals selected using propensity score matching. Resting MBF was similar in the two groups. Hyperemic flows were also similar in the two groups, 2.0 ± 0.4 vs 2.2 ± 0.7 ml/min/gm in patients and controls. However, despite similar average resting and hyperemic flows, the MFR was statistically lower in the Reprint requests: Steven C. Port, MD, AdvocateAuroraHealth: Aurora Cardiovascular Services, Milwaukee, WI; [email protected] J Nucl Cardiol 2022;29:43–5. 1071-3581/$34.00 Copyright 2020 American Society of Nuclear Cardiology.