Determining the efficacy of cardiac surgery involves considering several risk factors and numerous patient outcomes [1] [2] [3] [4] [5] . Mortality and morbidity risk after surgery are measures cardiac surgeons universally calculate to estimate patient outcomes [6] [7] [8] [9] . Cardiac risk scores do not include functional status [10] [11] [12] [13] , despite evidence that adding this component would enhance mortality and morbidity risk prediction [14] [15] [16] [17] [18] . Varley et al. demonstrated one-year mortality risk was significantly reduced when preoperative frailty (i.e. poor functional status) was identified in elective surgery patients [18] . Moreover, poor preoperative functional mobility has been correlated to a decline in physical function after cardiac surgery [19] [20] . Researchers found functional status was more predictive of mortality than a patient’s principal admitting diagnosis [21] , was strongly associated with increased mortality risk among geriatric surgical populations at 2-months postoperative [22] and at 6-months postoperative [23] and had increased 90-day and 6-month mortality, respectively [21] [24] , among the hospitalized elderly population.

Functional status is defined as an individual’s ability to perform activities within their regular environment, an ability potentially limited by cardiac disease, perceived symptoms, and environmental, social and psychological factors [25] . Researchers have historically measured functional status using self-report questionnaires to calculate physical health, well-being, and quality of life [26] - [31] . Consensus is lacking on a standardized outcome measure to use. Self-report questionnaires such as the Short Form 36 (SF-36) and Katz Index of Independence in Activities of Daily Living (Katz ADL), have been used in several studies on “functional status,” [26] - [31] however, they lack specificity, as seen by their use in research to measure quality of life [29] [30] [32] , general health [13] , postoperative pain [32] , and functional capacity [22] [28] . While these studies may shed some light on patient recovery symptoms over time, the tools used were not validated to measure functional status, but rather health-related quality of life.

Incongruencies also exist in research concerning the time lapse until functional status improvement appears and full recovery restores following coronary artery bypass graft (CABG) surgery. Based on gaps in prospective research, Ballan et al. [33] recommended exploring function preoperative to six-week post-CABG surgery. Ballan et al. detected functional improvement at six weeks, but patient-perceived pain remained notable [33] . LaPierand Mizner [27] used several functional status measures and found patients continued to report moderate deficits in performing daily activities and function at 6 months post-CABG. Based on Katz ADL and FIM scores, Niemeyer-Guimarães, Cendoroglo, and Almada-Filho [31] found “slow recovery” in functional status at 1 month and 6 months post-CABG compared to discharge, but not back to baseline. In contrast, Barnason et al. [26] utilized SF-36 questionnaire and concluded baseline functional status responses were surpassed by 6 to 12 months. Hunt, Hendrata and Myles [32] detected gains in function but not patient-perceived quality of life at 12 months, while Joskowiak et al. [29] concluded physical and mental health status improved within the first year after cardiac surgery, both using the SF-36 tool. Without using a validated tool designed to measure function it remains unclear if significant functional gains occur in the early postoperative phase and if they surpass baseline levels by 12 months postoperative. Rigorous studies examining this very question about patient-reported functional status remain lacking [34] .

One validated functional status measure is the Late-Life Function and Disability Instrument (LLFDI), a self-report questionnaire which targets a variety of physical activities and social life tasks [function component], as well as assesses participation ability and frequency in different social activities [disability component]. The LLFDI has established valid and reliable function and disability components that, when combined, yield outcome measures for functional status [27] [35] - [40] . The LLFDI has been used by LaPier et al. [27] [41] to assess preoperative/postoperative functional status change in cardiac surgery patients, but to date, the LLFDI has not been used to track functional status changes over time with this population.

The purpose of this study was to assess functional status changes over time among patients who underwent elective cardiac surgery using the LLFDI.

This study’s findings indicated that by one-year postoperative, individuals surpassed their preoperative functional status. These findings are consistent with a few longitudinal studies that have explored functional status changes after CABG surgery [15] [23] [28] [29] . These studies, however, differed in study duration and/or outcome measure selection and did not include either preoperative or prospective data. A few studies only tracked functional status to six months post-CABG [21] [30] [31] . Bӓck et al. [15] captured functional mobility pre-cardiac surgery using Functional Independence Measure (FIM) scores but estimated one-year postoperative outcomes. Ko et al. [23] conducted a retrospective study in which preoperative functional status was derived from admission FIM scores to estimate postoperative major cardiac events and mortality risk six months following cardiac surgery and no patient-response data were collected. Joskowiak et al. [29] concluded “functional status” improved within the first year after cardiac surgery but examined health-related quality of life rather than function. Douki et al. [28] determined functional status at 18 months surpassed baseline scores, however no time points between were assessed.

Based on results from this study, no improvement in any aspect of functional status was detected at 6-week postoperative. Minimal research to date has been conducted examining functional changes this early post-surgery. Niemeyer-Guimarães et al. [31] explored functional status changes from preadmission to one and six-month postoperative using Katz ADL Scale and FIM scores and concluded slow recovery without return to baseline scores. Mori et al. [30] found of subjects post-CABG (n = 362), that 14% still had difficulty in at least one ADL at six months. These results are consistent with the findings from this study. Cardiac surgery is a major operation which typically includes sternal precautions for six weeks and this may help to explain why patients did not report significant improvement 6 weeks post-surgery.

The relatively small sample impacted the statistical power of the study, and possibly explains the inability to reach any of the standardized minimally detectable change (MDC) levels, according to a validation study by LaPier and Mizner [27] for the LLFDI tool, despite reaching statistical significance on Disability Frequency and Function Total with the data. Based on 95% confidence interval, LaPier and Mizner calculated MDC for the Disability Limitation component as 16.7 and in high contrast to 7.8 for Disability Frequency component and 4.3 for the Function component [27] . Given the wide variance in response noted for Disability Limitation, the change needed to exceed level of measurement error in order to detect meaningful change in Disability Limitation was not likely to be reached with the relatively small sample size here. Unlike the frequency to which one participates in personal and social life tasks, Disability Limitation refers to one’s capability in participating. Since people participate in activities with great variance in capability, a wide range of scores is not unexpected. However, this may have reduced the power and inflated the risk of a type II error.

Although MDC was not reached, minimum clinically important difference (MCID) was reached according to Beauchamp et al. [43] , with MCID for each LLFDI sub-group between 2 (small) and 5 (large/significant) and considered clinically meaningful to the participants. In terms of clinical relevance in this research field, this study was one of the first to collect prospective patient data on cardiac surgery recovery with respect to functional status changes from preoperative to six weeks postoperative and as far out as one-year postoperative. Further, this study used an outcome tool specifically designed to measure functional status and one tested on patients with cardiovascular disease [27] [35] [36] [38] [39] [41] .

Attrition rate from consent to preoperative LLFDI was 29% (n = 22). One explanation may have been that subjects were met just after news received of cardiac surgery recommended, without much time to process information. Further, there was a small window of time (roughly two hours) to obtain informed consents before subjects were discharged home. Conducting this study at a single site with a sample of convenience without a control group limits the generalizability of the findings. Closer examination of the data revealed that all but six of the participating subjects underwent CABG surgery (n = 37) and only one of the six valve procedures was a combination valve/CABG surgery; therefore, the sub-groups were too small for comparative analysis. This research did not consider other factors that also may have influenced postoperative functional status such as whether subjects participated in cardiac rehabilitation. Tahir et al. [44] noted a positive correlation between cardiac rehabilitation participation and improved physical function following CABG. Future studies would benefit from exploring cardiac rehabilitation’s influence on functional status changes over time and conducting a multi-center study to fully examine cardiac surgery sub-groups.

Although cardiac surgery patients’ difficulties with various social life tasks (disability limitation) failed to significantly improve by one-year postoperative, the extent of participation in their social life tasks (disability frequency) and their ability to perform routine physical activities (function) significantly improved over time, specifically from preoperative to one-year postoperative. For individuals and their loved ones, cardiac surgery is a serious conversation with the medical team and one that should be patient-centered [45] [46] . Having as much information as possible is of the utmost importance [45] . Understanding functional status changes over time may assist patients and their families in elective cardiac surgery decisions and with what to expect for recovery [16] [45] . American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines, published December 2023, is the first to recognize the importance of functional status and recommend its inclusion among other risk factors [47] . Cardiac risk scores have yet to include functional status and a standardized outcome tool has yet to be established [47] .