The Role of the Three‐Dimensional Systolic Dyssynchrony Index and Autonomic Dysfunction Parameters in Detecting Subclinical Cardiac Involvement in Ankylosing Spondylitis

OBJECTIVE: Ankylosing spondylitis (AS) is associated with an increased risk of cardiovascular complications, often subclinical. This study aimed to comprehensively investigate subclinical cardiac dysfunction using two- and three-dimensional echocardiography (2DE, 3DE) and its relationship with autonomic dysfunction parameters and disease activity in AS patients without overt heart disease. METHODS: This cross-sectional study included 50 AS patients and 31 age- and sex-matched healthy controls. All participants underwent 2DE, 3DE (for EF, left ventricular systolic dyssynchrony index, 16-Segment Systolic Dyssynchrony Index [16-SDI]), 24-hour Holter monitoring (for heart rate variability [HRV]), clinical evaluation (Bath AS Disease Activity Index [BASDAI]), and biochemical testing. RESULTS: Conventional systolic functions (2DE/3DE LVEF) was comparable between groups; however, AS patients exhibited significantly higher 16-SDI values compared with controls (median 3.48% [2.4-5.2] vs. 1.64% [1.3-2.4], p < 0.001), indicating greater ventricular mechanical dispersion despite preserved ejection fraction. HRV indices including standard deviation of all normal-to-normal intervals (SDNN), triangular index, and low frequency (LF)/high frequency (HF) ratio, showed relatively lower values in AS patients (p < 0.01 for all), although within generally accepted physiological ranges. BASDAI correlated positively with 16-SDI (r = 0.650, p < 0.001) and remained an independent predictor of increased mechanical dispersion in multivariable analysis (β = 1.98, 95% CI 0.98-2.98; p < 0.001). CONCLUSION: AS patients demonstrate a significant subclinical shift toward increased left ventricular mechanical dyssynchrony detectable by 3DE despite normal ejection fraction. This alteration is independently associated with disease activity, suggesting a potential link with systemic inflammatory burden and early myocardial mechanical impairment. These findings indicate that 3DE-derived mechanical dyssynchrony may represent an early and sensitive marker of subclinical cardiovascular involvement in selected AS patients, warranting confirmation in longitudinal studies.