Metabolic alkalosis (MA) is the most common acid-base disorder and when it's severe it can have effects on cellular function and contribute to an increase in mortality.

MA is a common complication of heart failure (HF) especially when patients are treated with diuretics, but few studies have analyzed the prevalence of acid-base disorders in patients with HF.

All these studies have shown that MA is more common in patients with HF in more advanced stages and that the use of diuretics increases the prevalence of MA.

The study hypothesis, based on clinical experience and the few data that exist in the scientific literature, is that MA is a frequent analytical disorder in patients admitted for decompensated HF and that its presence entails a worse short-term vital prognosis.

The ALCALOTIC study is an observational cohort and prospective study.

The main objectives of the study are the following:

1. To determine the prevalence of MA in patients admitted for decompensated HF
2. To analyze if there are differences in patients admitted for HF according to the presence of MA on admission
3. To determine if the presence of MA has an influence on the short-term prognosis in patients admitted for decompensated HF

Inclusion Criteria:

• Patient admitted for decompensated HF (main admission diagnosis), who meet the diagnostic criteria of the 2016 European HF Guidelines and who sign the informed consent to participate in the study
• Patients must give their written consent to participate in the study

Exclusion Criteria:

• Patients whose main reason for admission is not decompensated HF. Those patients who are admitted for another reason and who also have decompensated HF secondarily cannot be included
• Patients who do not strictly meet the diagnostic criteria for HF of the European HF Guidelines.
• Patients for whom analytical values are not available in relation to acid-base balance at the time of admission
• Patients with a pathological history that can clearly justify metabolic alkalosis, such as primary or secondary hyperaldosterism
• Patients who were taking sodium bicarbonate prior to admission
• Patients with factors present at admission that may justify the presence of metabolis alkalosis: vomiting, diarrea, etc.
• Patients who do not give their consent to participate in the study

The patients will be recruited from the Internal Medicine Services of Spanish Hospitals whose researchers are active members of the Working Group on Heart Failure and Atrial Fibrillation of the Spanish Society of Internal Medicine