Hyponatraemia on admission to hospital is associated with increased long-term risk of mortality in survivors of myocardial infarction.
BACKGROUND
Hyponatremia is associated with an increased risk of mortality in patients with heart failure and in acute ST-segment elevation myocardial infarction (STEMI). The aim was to assess the impact of hyponatremia on admission on long-term mortality of patients with first ever STEMI or non-STEMI (NSTEMI).


METHODS
This was a longitudinal observation study


METHODS
The study population consisted of 3558 patients, aged 25-74 years, with an incident acute myocardial infarction (AMI) in the years 2000-2008 who survived for at least 28 days. All consecutive patients were registered through the Cooperative Health Research in the Region of Augsburg (KORA) Myocardial Infarction Registry. Serum sodium levels were obtained on admission. The association with long-term-mortality was examined using Cox regression models.


RESULTS
Hyponatraemia, defined as a sodium level less than 136 mmol/l, was present in 658 (18.5%) patients on admission. During a median follow-up period of six years (interquartile range (IQR) 4.0-8.2 years), 526 patients (14.8%) died. Hyponatraemia was significantly associated with long-term mortality by an 83% higher risk in the age- and sex-adjusted analysis. After further adjustment for reduced left ventricular ejection fraction (LVEF), glomerular filtration rate, haemoglobin, hypertension, hyperlipidaemia, any recanalization therapy, diabetes, medication with diuretics and angiotensin-converting enzyme (ACE) inhibitor/angiotensin-receptor blocker before admission and other parameters hyponatraemia remained a strong predictor for higher long-term mortality (hazard ratio 1.61; 95% confidence interval 1.32-1.97).


CONCLUSIONS
Patients with incident AMI and hyponatraemia on admission showed a significantly higher risk of long-term mortality than patients without. This strong predictive value was independent of a number of prognostic factors, including diabetes, glomerular filtration rate or reduced LVEF.
Department of Laboratory Medicine and Microbiology, Central Hospital of Augsburg, Germany.
Katrin
K
Burkhardt
MONICA/KORA Myocardial Infarction Registry, Central Hospital of Augsburg, Germany Institute of Epidemiology II, Helmholtz Zentrum München, German Research Center for Envirionmental Health (GmbH), Germany inge.kirchberger@Helmholtz-muenchen.de.
Inge
I
Kirchberger
MONICA/KORA Myocardial Infarction Registry, Central Hospital of Augsburg, Germany Institute of Epidemiology II, Helmholtz Zentrum München, German Research Center for Envirionmental Health (GmbH), Germany.
Margit
M
Heier
Institute of Epidemiology II, Helmholtz Zentrum München, German Research Center for Envirionmental Health (GmbH), Germany.
Angelika
A
Zirngibl
Department of Laboratory Medicine and Microbiology, Central Hospital of Augsburg, Germany.
Elisabeth
E
Kling
Department of Internal Medicine I - Cardiology, Central Hospital of Augsburg, Germany.
Wolfgang
W
von Scheidt
Department of Internal Medicine I - Cardiology, Central Hospital of Augsburg, Germany Department for Internal Medicine/Cardiology, Donau-Ries-Kliniken, Germany.
Bernhard
B
Kuch
MONICA/KORA Myocardial Infarction Registry, Central Hospital of Augsburg, Germany Institute of Epidemiology II, Helmholtz Zentrum München, German Research Center for Envirionmental Health (GmbH), Germany.
Christa
C
Meisinger
D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D016009:Chi-Square Distribution; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D007010:Hyponatremia / Q000097:blood / Q000175:diagnosis / Q000401:mortality*; D015994:Incidence; D053208:Kaplan-Meier Estimate; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis / Q000401:mortality* / Q000503:physiopathology / Q000628:therapy; D010343:Patient Admission; D011379:Prognosis; D016016:Proportional Hazards Models; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D012964:Sodium / Q000097:blood; D013318:Stroke Volume; D013997:Time Factors; D016277:Ventricular Function, Left
D015415:Biomarkers; D012964:Sodium
Cooperative Health Research in the Region of Augsburg; Hyponatraemia; mortality; myocardial infarction