Risk factors for admission on an intensive care unit in patients hospitalized due to heart failure

Background: Heart failure (HF) is a clinical syndrome affecting 1-2% of the adult population and associated with high morbidity and increased mortality. HF is most prevalently driven by myocardial dysfunction but might also caused by pathologies of the heart valves, peri-, and endocardium, conduction and arrhythmias.

HF risk stratification is primarily based on symptoms (e.g. NYHA classification), laboratory markers (e.g. natriuretic peptides) and left ventricular ejection fraction. However, risk stratification and the ability to withstand the underlying stressors depend additionally on further parameters such as comorbidity burden. Thus, we aimed to identify patients’ characteristics, which are associated with admission on an intensive care unit (ICU) in HF.

Methods: The nationwide German inpatient sample (NIS) of the years 2005-2022 was used for statistical analysis (source: RDC of the Federal Statistical Office and the Statistical Offices of the federal states, DRG Statistics 2005-2022, and own calculations). Hospitalizations of patients, who were admitted due to HF in German hospitals, were stratified for ICU admission. Additionally, risk factors for ICU admission were analysed.

Results: Overall, 7,265,342 hospitalizations of patients admitted due to HF were counted in Germany during the observational period between 2005 and 2022; among them, 498,295 (6.9%) had to be treated in ICUs. HF patients admitted to ICU were slightly younger (76.0 [68.0-82.0] vs. 80.0 [73.0-86.0] years, P<0.001), more often of male sex (56.0% vs. 48.1%, P<0.001), obese (14.2% vs 10.5%, P<0.001), and had more frequently diabetes mellitus (45.2% vs 38.2%, P<0.001) than those without ICU treatment. Comorbidity burden was higher in HF patients who had to be admitted to an ICU, mirrored by a higher Charlson comorbidity index (7.0 [5.0-8.0] vs 6.0 [5.0-8.0], P<0.001), driven by the comorbidities of coronary artery disease (48.5% vs. 40.5%, P<0.001), chronic obstructive pulmonary disease (23.2% vs. 16.3%, P<0.001) and renal failure (61.4% vs. 47.6%, P<0.001). The case-fatality rate of HF patients with ICU treatment was substantially higher compared to those not treated in ICU (23.7% vs. 8.1%, P<0.001). The necessity of ICU treatment was independently associated with increased case fatality (OR 4.629 [4.594-4.665], P<0.001).

Besides adverse in-hospital events, which were strongly and independently associated with ICU admission in HF, such as myocardial infarction (OR 4.932 [95%CI 4.872-4.993], P<0.001) and pneumonia (OR 4.453 [95%CI 4.424-4.482], P<0.001), coronary (OR 1.263 [95%CI 1.255-1.270], <0.001) and peripheral artery disease (OR 1.233 [95%CI 1.220-1.246], P<0.001), atrial fibrillation/flutter (OR 1.203 [95%CI 1.196-1.210], P<0.001), chronic obstructive pulmonary disease (OR 1.441 [95%CI 1.431-1.451], P<0.001), chronic anemia (OR 1.521 [95%CI 1.509-1.533], P<0.001) and renal failure (OR 1.899 [95%CI 1.887-1.910], P<0.001) were independent risk factors for ICU admission.

Conclusion: In Germany, 6.9% of the hospitalizations of HF patients were afflicted by ICU admission. Our very large real-world study of more than 7 million patient-cases enables us to identify important risk factors for adverse outcome beyond ejection fraction and laboratory marker assessment. In this context our study emphasizes that patients’ comorbidity burden plays a crucial role in risk stratification of HF patients.