The lack of reliable risk assessment scales to stratify patients with infective endocarditis (IE) requiring surgery remains a challenge for multidisciplinary IE teams, especially in cardiac surgery settings. This study aims to address this need by analyzing data from the U.S. National Inpatient Sample (NIS) database. A retrospective analysis was conducted on over seven million annual hospitalizations from 2016 to 2019, including 53,275 adults with a primary diagnosis of IE. Frailty in this cohort was assessed using the Hospital Frailty Risk Score, categorizing patients as low, intermediate, and high risk. Valvular surgery was identified through ICD-10 procedure codes, and inverse probability of treatment weighting (IPTW) was applied to balance baseline differences between intervention groups (valvular surgery vs. non-surgical candidates). The analysis was stratified by frailty levels. The study focused on in-hospital mortality, with no follow-up data. Secondary outcomes included the need for renal replacement therapy (RRT), circulatory support, and/or permanent pacemaker placement. 

From the 53,275 patients coded with IE, the mean age was 52 years (34–68), with 59% males. The Elixhauser Comorbidity Index was 5 (3–6), 9% of patients had a previous valvular prosthesis, and 39% were identified as intravenous drug users (IDUs). Valvular surgery was performed in 18.3% of cases, with surgical patients being younger, having longer hospital stays, and higher frailty scores. However, data on the proportion of the overall IE cohort that had surgical indications were not provided. Aortic valve surgery was performed in 55% of cases, mitral valve surgery in 46%, combined mitral-aortic surgery in 16%, and pulmonary valve surgery in 1%. Right-sided surgeries were performed in 12% of cases, and left-right surgeries in 4%. 

In the overall cohort, 42.7% had low frailty risk, 53.1% intermediate risk, and 4.2% high risk. After IPTW adjustment, there were no statistically significant differences in in-hospital mortality between valvular and non-valvular surgery groups for the entire cohort (3.7% vs. 4.1%, p = .483), or for patients with low (1% vs. 0.9%, p = .952) or moderate (5.4% vs. 6%, p = .548) frailty risk. However, patients with high frailty risk showed significantly lower in-hospital mortality in the valvular surgery group (4.6% vs. 13.9%, p = .016). There was a higher incidence of septic shock, need for mechanical circulatory support, and pacemaker placement in the surgical group, particularly in patients with low and intermediate frailty risk. 

The authors conclude that in IE patients at high frailty risk, “the decision to proceed with valvular surgery should be made cautiously,” as a mortality reduction benefit has been observed despite the predicted risk. Furthermore, they conclude that surgery was associated with an increased need for pacemaker implantation and mechanical circulatory support, similarly across all frailty risk groups. 

COMMENTARY: 

IE is a complex disease with significant interindividual clinical variability, requiring a multidisciplinary approach for diagnosis and treatment. Although the study’s objective is relevant, the analysis of retrospective administrative data from a large registry not designed specifically for IE, combined with a lack of follow-up, limits its precision. Moreover, it may introduce biases in diagnosis coding, procedure interpretation, and results extraction. 

First, this study does not enable adequate case definition. It does not account for Duke diagnostic criteria, so it is not possible to classify cases as definite, possible, or rejected IE. Secondly, not all relevant clinical information is provided. Microbiological data, which undoubtedly influence the disease’s aggressiveness and impact surgical decision-making and mortality—as demonstrated with S. aureus IE in various international and multicenter registries—are unknown. Additionally, echocardiographic variables, structural complications, distant embolisms, heart failure, and cardiogenic shock are not considered. This, along with the lack of data on specific surgical indications, affects the interpretation of both primary and secondary study outcomes. Thirdly, it is crucial to know the percentage of patients in the cohort with surgical indication who underwent surgery versus those who did not, to properly evaluate the impact of frailty on surgical decision-making. 

In contrast, the general cohort results differ from other recognized multicenter IE registries, such as the ICE (International Collaborative Endocarditis Prospective Cohort Study) enrolling patients from 2000 to 2012, or the EUROENDO study conducted from 2016 to 2018. This study describes a younger cohort with a notably lower surgery rate (18%) and lower mortality (4%) than reported in the literature. In the ICE and EUROENDO registries, respective surgery rates were 52% and 51%, with in-hospital mortality rates of 19% and 17%, reaching 22% at six months in ICE and 23% at one year in EUROENDO. The authors suggest these differences may be due to better representativeness of community-acquired IE in lower-risk patients, typically excluded from tertiary university hospital studies. This cohort also includes a high percentage of IDUs (39%), who are generally younger and present with right-sided IE, usually not referred for surgery. 

In summary, frailty assessment is a key factor in IE management, helping to identify patients who may benefit from surgery despite high risk. Early-stage surgery, when indicated, has shown a positive impact on prognosis. Integrating frailty assessment into preoperative risk models could enhance outcome prediction accuracy and facilitate therapeutic decision-making. However, given the rarity of surgery in high-risk patients in this study, no robust evidence supports general recommendations. 

REFERENCE: 

Diaz-Arocutipa C, Moreno G, Vicent L. Impact of valvular surgery according to frailty risk in patients with infective endocarditis. Clin Cardiol. 2024 May;47(5):e24268. doi: 10.1002/clc.24268.

Chu VH, Park LP, Athan E, Delahaye F, Freiberger T, Lamas C, et al. Association between surgical indications, operative risk, and clinical outcome in infective endocarditis: a prospective study from the International Collaboration on Endocarditis. Circulation. 2015 Jan 13;131(2):131-40. doi: 10.1161/CIRCULATIONAHA.114.012461.

Habib G, Erba PA, Iung B, Donal E, Cosyns B, Laroche C, et al; EURO-ENDO Investigators. Clinical presentation, aetiology and outcome of infective endocarditis. Results of the ESC-EORP EURO-ENDO (European infective endocarditis) registry: a prospective cohort study. Eur Heart J. 2019 Oct 14;40(39):3222-3232. doi: 10.1093/eurheartj/ehz620.