Ankylosing spondylitis and muscle sympathetic nerve activity: a case study

Inflammatory diseases are associated with elevated cardiovascular (CV) risk, and heightened muscle sympathetic nerve activity (MSNA) is a potential contributor. This case study characterized MSNA in two patients with ankylosing spondylitis (AS) and evaluated the effect of TNF-α blockade therapy. Two males diagnosed with AS (Case 1: 34 years, 26kg/m 2 ; Case 2: 22 years, 31kg/m 2 ) participated. In Case 1, 10-minutes of continuous beat-to-beat blood pressure, heart rate (HR), and MSNA were recorded on two occasions 3-months apart. Case 2 similarly underwent 10-minutes of autonomic monitoring before and after 6-months of routine-care TNF-α blockade. In Case 1, systolic (SBP: 120 vs. 121 mmHg) and diastolic (DBP: 64 vs. 70 mmHg) blood pressure, HR (58 vs. 59 beats/min), and MSNA (32 vs. 37 bursts/min) were similar across the two visits, suggesting reliable MSNA in our AS patient. Case 2 also demonstrated higher-than-expected resting MSNA (45 bursts/min) when considering age and BMI, and further demonstrated marked reductions in SBP (146 vs. 124 mmHg), DBP (84 vs. 70 mmHg), HR (76 vs. 69 beats/min), and MSNA (45 vs. 26 bursts/min) following 6-mo of TNF-α blockade. The present case study indicates that heightened sympathetic activity is a potential physiological mechanism contributing to increased CV disease in populations with AS. Furthermore, suppression of inflammation or symptom amelioration may help attenuate the increased sympathetic activity and potentially lower cardiovascular risk over time within this unique rheumatic population. While caution is necessary given the case study approach, future work examining neural cardiovascular control in AS patients appears warranted.