The "binary switch" of vascular aging: coronary artery calcium presence, but not density or volume, predicts exaggerated blood pressure response during exercise

Background Exaggerated blood pressure response (EBPR) during exercise is a validated marker of increased cardiovascular risk and arterial stiffness. While the Agatston score is the gold standard for structural plaque burden, the relationship between its individual components—volume and density—and functional vascular impairment (EBPR) remain poorly understood. Objective To investigate whether EBPR correlates more closely with the total structural burden(volume), the plaque stability (density), or the simple presence (CAC > 0) of coronary artery calcium Method We conducted a cross-sectional analysis of 351 patients (mean age 54.7 ± 10.9 years) who attended a heart screening program and underwent both coronary CT calcium scoring and exercise stress testing within the same day. CAC was decomposed into total volume (mm³) and mean density score (Agatston/Volume ratio). EBPR was defined as peak systolic blood pressure ≥ 210 mmHg (males) or ≥ 190 mmHg (females). The association was assessed via chi-square and Mantel-Haenszel odds ratios. Differences in continuous variables (volume, density, and score) were analyzed using independent samples T-tests. Results The transition from a zero (15 of 157 pts) to a non-zero CAC score (59 of 194 pts) was the single most potent predictor of exercise-induced hypertension, carrying a 4.14-fold increase in the odds of EBPR (95% CI: 2.24–7.64, p < .001). However, once this threshold was crossed, the "severity" of the disease appeared to reach a functional plateau. We observed no statistically significant differences in the mean calcium density between patients with and without EBPR (0.98 ± 0.22 vs 1.00 ± 0.30, p = 0.628), nor were there significant differences in mean calcium volume (291 ± 549 vs 254 ± 547, p = 0.668) or total Agatston Score (342 ± 675 vs 305 ± 685, p = 0.724). Conclusion Coronary calcification acts as a "binary switch" for functional vascular impairment. Our findings identify a "threshold phenomenon" where the mere presence of plaque— regardless of its mineral density or total volume—predicts an exaggerated blood pressure response (OR 4.14). This suggests that the transition to a calcified phenotype represents a critical loss of arterial compliance, necessitating aggressive BP monitoring for any patient with a non-zero CAC score.