Admission Heart Rate Can Be Used as an In-Hospital Mortality Risk Marker in Patients With AECOPD, RF

Admission heart rate (AHR) may be used to predict in-hospital mortality of patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) and respiratory failure (RF), according to a study published in BMC Pulmonary Medicine.

The researchers explained that AECOPD, which may be classified as mild, moderate, or severe, is one of the most common causes of hospital admission, with patients with severe AECOPD often experiencing rapid deterioration and requiring hospitalization. They noted that those with frequent AECOPD experience reduced quality of life and an accelerated decline in lung function, with RF contributing the most to the high mortality and poor prognosis of these patients.

Previous studies linked AHR, which the researchers defined as the first available heart rate measured from initial hospital admission, with increased short- and long-term mortality in patients discharged after acute myocardial infarction. The researchers noted that previous studies also found that patients with COPD have a higher cardiovascular risk as they die more frequently from cardiovascular diseases than from respiratory diseases. Consequently, the researchers expressed the need for an analysis of the relationship between AHR and in-hospital mortality in patients with AECOPD/RF.

Hospital bed | Image Credit: catinsyrup - stock.adobe.com

To explore this relationship, the researchers conducted a single-center retrospective analysis, which included patients older than 40 years old who were diagnosed with AECOPD and RF at the First Affiliated Hospital of Jinzhou Medical University in China between January 2021 and March 2023. The primary outcome measure was all-cause, in-hospital mortality.

They enrolled all patients admitted to the hospital with a primary diagnosis of AECOPD based on the Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria, along with a confirmed RF diagnosis through arterial blood gas analysis. Conversely, the researchers excluded those younger than 40 years old, those with unavailable heart rate data, those with a history of multiple admissions, those with incomplete data, and those with an AHR of less than 35 beats/minute.

For their analysis, the researchers used patients’ demographics, vital signs, laboratory investigations, outcomes, and diagnostic and treatment information. All patient demographic information and laboratory data were extracted from the hospital’s electronic medical system, and comorbidities were diagnosed based on the patient's medical history or medication use.

Initially, the researchers identified 510 eligible patients, but they only included 397 in their analysis. The mean (standard deviation [SD]) age of patients in the study cohort was 72.6 (9.5) years, and 49.4% of patients were female. Also, the study population’s disease history included type II RF (n = 266), cor pulmonale (n = 187), heart failure (n = 167), hypertension (n = 135), type I RF (n = 131), and diabetes mellitus (n = 43). Additionally, 261 patients used inhaled corticosteroids (ICS), and 199 used a ventilator.

Overall, the in-hospital mortality rate was 5%. The researchers explained that the hospital nonsurvivor group was older and had shorter hospital stays than the hospital survivor group (P < .05). In terms of mean (SD) AHR, that of patients in the non-survival group (107.0 [21.8] beats/minute) were higher than that of the survivor group (96.2 [18.2] beats/minute; P = .011).

Both a multivariate logistic regression analysis and smooth curve fitting revealed a nonlinear association between AHR and in-hospital mortality among the study population, with 100 beats/minute representing the inflection point. They noted that each beat/minute AHR increase above 100 beats/minute resulted in an odds ratio (OR) of 1.094 (95% CI, 1.01-1.186; P = .0281). In other words, having an AHR greater than 100 beats/minute was a predictor of potential mortality, which, the researchers claimed, increased by 9.4% for every 1 beat/minute increase in AHR.

Conversely, for patients with an AHR below 100 beats/minute, the effect size (OR) was 0.474 (95% CI, 0.016-13.683; P = .6635); there were no significant differences in survival among patients with AHRs below 100 beats/minute.

The researchers acknowledged their study’s limitations, one being that it was a single-center study with a small sample size. Consequently, the possibility of selection bias and lack of a validation cohort must be considered. Also, they could not obtain all baseline characteristics of the patients, which may have led to biased results.

To validate and expand on their findings, the researchers suggested designing future studies to address these limitations. However, they expressed confidence in their findings despite the limitations.

“AHR was associated with increased all-cause, in-hospital mortality in patients with AECOPD and RF,” the authors concluded. “Therefore, as a simple and accessible parameter, an elevated AHR should be a risk signal to alert respiratory physicians to perform intervention(s) early.”

Reference

Zhou R, Pan D. Association between admission heart rate and in-hospital mortality in patients with acute exacerbation of chronic obstructive pulmonary disease and respiratory failure: a retrospective cohort study. BMC Pulm Med. 2024;24(1):111. doi:10.1186/s12890-024-02934-w