Background/Purpose:  Patients with rheumatoid arthritis (RA) are at increased risk for myocardial infarction (MI), which is often silent. Heart rate adjusted ST segment (ST/HR index) is a novel method for assessing myocardial ischemic changes during exercise testing. This index has been related to MI risk and has been shown to have greater sensitivity in detecting ischemic changes than conventional ST segment depression, which relies on reaching maximal workload intensity during exercise tolerance test (ETT). ST/HR index takes heart rate responses to exercise into account, which means that it is not necessary for study participants to reach maximal workload. This is particularly important for patients with RA, who might have limited exercise ability due to joint problems. Reduced heart rate variability (HRV) at rest is an indicator of reduced parasympathetic activity and poorer cardiac autonomic balance, and it has been suggested to contribute to the risk of developing MI. Both ST/HR index and HRV are related to MI, but little is known about their associations. Thus, this study is aimed to explore the association between resting HRV indices and ST/HR index in patients with RA.

Methods:  Two minutes beat to beat R-R interval data from ECG were recorded in 96 RA patients (54.4±12.6 years, 68% women). ST/HR index was measured as the difference between ST-segment depression at rest and maximum ST-segment depression during ETT, divided by the absolute change from resting heart rate (HR) to the HR at maximum ST depression during the ETT. Low frequency (LF; 0.04-0.15 Hz) and high frequency (HF; 0.15-0.40 Hz) spectral powers, LF/HF ratio, and the normalised units (nu) of LF and HF were used as HRV indices to measure cardiac autonomic control.

Results:  Mean ST/HR index was 2.6 ± 1.7v µV/beats/min. Mean or median values for HRV indices were LF (nu) [60.4 (41.7-76.1)], HF (nu) (43.0 ± 24.4), LF/HF ratio [1.5 (0.7-3.1)]. Pearson moment correlation (controlling for gender) revealed that LF/HF ratio (r (81) = .28, p= .01) and LF (r (81) = .23, p= .03) were positively and HF (r (81) = -.27, p= .01) was negatively associated with ST/HR index.

Conclusion:  This is the first study to report an association between ST/HR index, parasympathetic activity and autonomic balance in patient with RA. Measuring ST/HR index during ETT could be a particularly relevant indicator for p with RA who might not be able to exercise to their maximal HR due to joint problems. Thus, the use of ST/HR index during exercise testing may help in early detection of risk for MI in people with RA. Further research is needed to explore the associations between ST/HR index and clinical cardiac endpoints.

« Back to 2016 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/associations-between-heart-rate-adjusted-st-segment-and-heart-rate-variability-in-patients-with-rheumatoid-arthritis/