METABOLIC SYNDROME IS CHARACTERIZED BY INCREASED VENTRICULAR SYSTOLIC STIFFENING AND VENTRICULO-ARTERIAL MISMATCH

Background: Left ventricular (LV) end-systolic stiffness (Ees) reflects LV contractility, geometry and mass. With aging, Ees maintains constant ratio to total arterial load (arterial elastance, Ea), so that ventriculo-vascular coupling is preserved and cardiac performance is optimized. We tested the hypothesis that metabolic syndrome (MS) adversely impacts this coupling relationship.
Methods: Ea and Ees were estimated by single-beat methods (Chen CH, JACC 2001, 38(7):2028-34)based on resting BP and echocardiograms from 176 ambulatory participants (age 64 ± 13 y, 51% females) in the Baltimore Longitudinal Study of Aging. MS status and score were determined according to ATP III-NCEP.
Results: MS+ subjects had higher Ees (3.1 vs. 2.6 mmHg/ml, p=0.002) and Ees/Ea ratio (2.1 vs. 1.9, p=0.02) than MS-, while Ea was similar in both groups (1.5 vs. 1.4 mmHg/ml, p=0.07). MS score correlated with Ees (r=0.27, p<0.001, Figure). Pulse pressure and relative LV wall thickness were higher in MS+, while systemic resistance, LV mass, age and gender were similar (p>0.1) in both groups. Ees and Ees/Ea ratio correlated with peak VO2 (r= - 0.33 and - 0.29, p<0.001), which was lower in MS+ subjects (19 vs. 25 ml/kg/min, p<0.001).
Conclusions: In MS, ventricular stiffening rises beyond that predicted by arterial load. This implies less systolic reserve, and the corresponding ventricular-arterial mismatch likely contributes to exercise intolerance. Neurohumoral and metabolic factors promoting disproportionate higher Ees in MS need to be identified.