慢性うっ血性心不全における腎Mg代謝に関する検討

It is now known that the serum magnesium level is low in patients with chronic congestive heart failure (CHF). In this study, to clarify the role of renal magnesium handling in CHF, the following parameters were examined in normal subjects (control: n=28) and patients with CHF (n=37): serum magnesium (s-Mg), plasma aldosterone concentration (PAC), endogenous creatinine clearance (CCr), urinary excretions of magnesium (UMgV) and sodium (UNaV), and fractional excretions of magnesium (FEMg), sodium (FENa) and potassium (FEK). The relationship between s-Mg and the severity of cardiac dysfunction (NYHA subclass in CHF) was also investigated in CHF. All subjects were admitted to our hospital and given a standard diet including 120 mEq of Na and 75 mEq of K/day, and all the parameters were measured in the early morning after an overnight fast. Compared with the controls, the patients with CHF showed lower levels of s-Mg, CCr, UNaV and FENa, and higher levels of FEMg and PAC. On the other hand, there was no significant difference in UMgV between the controls and CHF patients. In both groups, significant positive correlations were observed between UMgV and FEMg, and between UMgV and CCr. FEMg correlated positively with FEK and PAC in patients with CHF, suggesting an important role of mineralocorticoids in magnesium handling in the distal renal tubules. In the severe CHF (NYHA II or III) subgroup, levels of s-Mg and FEMg were quite similar to those in the mild CHF (NYHA I) subgroup, but the sever CHF subgroup used potassium-magnesium sparing drugs (spironolactone, triamterene and angiotensin converting enzyme inhibitor) more frequently. In CHF patients, combined use of loop diuretics and potassium-magnesium sparing drugs did not show any significant influence on the levels of s-Mg and FEMg. These results suggest that the low level of s-Mg in CHF patients is attributable to enhancement of renal magnesium excretion by secondary aldosteronism, and that use of potassium-magnesium sparing drugs may be beneficial for prevention of magnesium deficiency in CHF