Correlation Between Increased Urinary Sodium Excretion and Decreased Left Ventricular Diastolic Function in Patients with Type 2 Diabetes Mellitus

Background: Increased salt intake may induce hypertension, lead to cardiac hypertrophy, and exacerbate heart failure. When elderly patients develop heart failure, diastolic dysfunction is often observed, although the ejection fraction has decreased. Diabetes mellitus (DM) is an established risk factor for heart failure. However, little is known about the relationship between cardiac function and urinary sodium excretion (U-Na) in patients with DM. Methods: We measured 24-hour U-Na; cardiac function was evaluated directly during coronary catheterization in type 2 DM (n = 46) or non-DM (n = 55) patients with preserved cardiac systolic function (ejection fraction >= 60%). Cardiac diastolic and systolic function was evaluated as -dp/dt and +dp/dt, respectively. Results: The average of U-Na was 166.6 +/- 61.2 mEq/24 hour (mean +/- SD). In all patients, stepwise multivariate regression analysis revealed that -dp/dt had a negative correlation with serum B-type natriuretic peptide (BNP; beta = -0.23, P =.021) and U-Na (beta = -0.24, P = .013). On the other hand, +dp/dt negatively correlated with BNP (beta = -0.30, P < .001), but did not relate to U-Na. In the DM-patients, stepwise multivariate regression analysis showed that -dp/dt still had a negative correlation with U-Na (beta = -0.33, P = .025). Conclusion: The results indicated that increased urinary sodium excretion is associated with an impairment of cardiac diastolic function, especially in patients with DM, suggesting that a reduction of salt intake may improve cardiac diastolic function.