Retrospective Analysis Of Hyponatremia In Patients With Chronic Heart Failure In Late 30 Years

Objective: To investigate the prevalence of hyponatremia in chronic heart failure(CHF) and analyse the changes of prevalence in recent 30 years, also explore the possible causes and estimate the influences of hyponatremia on days of hospitalization and in-hospital mortality of patients with chronic heart failure.Methods: 2555 cases with chronic heart failure were collected in research from the Second Hospital of Tianjin Medical University from January 1980 to August 2007. Detailed clinical data were recorded including patients age, gender, etiology of heart failure, heart function, complications, medication use and clinical outcomes. According to admission serum sodium concentration, patients were categorized into two groups: NA<135mmol/L (the hyponatremic group)and NA>135mmol/L(the normonatraemic group). The differences of clinical characteristic and pharmaceutical application between two groups were compared. Also the data were sorted into >60 years old and <60 years old, course of disease >7 years and <7 years. Prevalence of hyponatremia was analysed within different etiologies, heart function, gender, age, course of diseases, pre-admission medication use, respectively. The impact of atrial fibrillation, renal dysfunction and anemia on the proportion of hyponatremia was also analysed. And the data were categorised into group A(from January 1980 to December 1989), group B(from January 1990 to December 1999) and group C(from January 2000 to August 2007). The changes of prevalence of hyponatremia, heart failure etiology and medication application were estimated within a decade interval. The relationship between admission sodium and prognosis of hospitalization were also analysed.Results: 2465 cases were inrolled, among which there were male 1274 and female 1191. The serum sodium ranged (98.2-154)mmol/L, with a median 138.8mmol/L. The hyponatremic group included 618 patients(acounting for 25.1%), and the proportion on admission decreased year by year. Patients with hyponatremia were more likely to have higher grade of NYHA functional class, lower systolic blood pressure and lower left ventricular ejection fraction. More hyponatremic patients had atrial fibrillation, renal dysfunction and anemia. Lower admission sodium leval was also related with higher concentration of angiotensin, aldosterone and higher activity of renin. Compared with normonatraemic patients, hyponatremic patients received more digitalis and more diuretics, but lessβ-blockers and calcium channel blockers (P=0.000). There were no significant diffrences in the use of Angiotensin-converting enzyme inhibitors(ACEI) and Angiotensin receptor blockers(ARB) between two groups, but the application proportion of ACEI or ARB was still higher in hyponatremic patients than others. Dilated cardiomyopathy, pulmonary heart disease and rheumatic heart disease, which demonstrated a trend of decrease when analysed by a decade group, were associated with higher ratios of hyponatremia than CHD, while prevalence of CHD increased gradually. The lesser use ofβ-blockers, ACEI or ARB during pre-admission, the more likely to combine with hyponatremia. But the application of ACEI, ARB andβ-blockers was increased year after year. There was a negative correlation between admission serum sodium leval and activity of renin, angiotensin and aldosterone. Hyponatremic group had significantly longer hospital stays and higher rate of in-hospital mortality than other patients. After adjusting to other risk factors with multivariable analysis, lower admission serum sodium leval was an independent risk factor of hospital stays and in-hospital mortality. There was a negative correlation between admission sodium leval and days of hospitalization. The partial coefficient was -0.132. The risk of in-hospital mortality increased by 24.7% for each 3mmol/L decrease in admission serum sodium leval. The in-hospital mortality was 2.5 folds higher in persistent hyponatremic patients than in patients whose serum sodium leval were corrected during hospitalization.Conclusions: Hyponatremia in hospitalized patients with chronic heart failure is relatively common and the proportion is decreased year by year, which may be associated with the change of etiology and the increasing application of ACEI, ARB andβ-blockers year after year. Hyponatremia is associated with poorer heart function, higher activity of neural hormone, longer stays and higher in-hospital mortality. Lower admission serum sodium leval may be an independent risk factor of hospital stays and in-hospital mortality.