A quick bedside assessment may one day help determine the long-term prognosis for patients undergoing coronary artery bypass graft (CABG) surgery. According to the results of an observational study, poor functional status before CABG was associated with significantly increased risk for long-term mortality.
“We demonstrated that poor baseline functional status in CABG patients is associated with higher long-term mortality following surgery,” said Hanjo Ko, MD, critical care medicine and cardiac anesthesia fellow at Brigham and Women’s Hospital, in Boston. “These patients represent a high-risk group for adverse outcomes following CABG that is not well captured by standard risk assessment. Further study is needed to determine if pre-CABG functional status is a modifiable risk factor for outcomes following CABG,” Dr. Ko reported at the 2016 annual meeting of the Society of Cardiovascular Anesthesiologists (abstract 5).
While there are well-established risk assessments to predict mortality in cardiac surgical patients, such as the Society of Thoracic Surgeons (STS) score, limitations exist given their significant reliance on chronological age as a predictor of health.
In addition, Dr. Ko noted, there is limited information regarding the association between baseline functional status and mortality after CABG.
In order to ascertain this association, Dr. Ko and her colleagues performed a retrospective observational study on 722 adults who had undergone CABG at Brigham and Women’s Hospital between 2002 and 2014. All patients had a formal evaluation by a physical therapist three months before surgery. The researchers then looked at six-month mortality after surgery.
As Dr. Ko explained, a licensed physical therapist determined the functional status of the patients using the Functional Independence Measure (FIM). The pre-CABG FIM score ranged from 0 (excellent, a completely independent individual) to 62 (poor, someone who is completely dependent on others).
“I’m not talking about running on a treadmill,” said Dr. Ko. “I’m talking about whether or not you can get up from bed, walk to a chair and go to the bathroom. … It is a global representation of how well you can perform your activities of daily living (ADLs).”
Researchers also considered covariates, such as STS score, age, sex, race and New York Heart Association class. The demographics were similar to what would be expected for CABG patients, Dr. Ko reported.
Results Were Intuitive
The overall six-month mortality for the entire cohort was 6.5%. This percentage varied significantly, however, based on preoperative functional status, as patients were divided into “good,” “fair,” “marginal” or “poor” categories.
For 71 patients (9.8%) with an FIM score of 0 (excellent condition), the six-month mortality rate was 1.4%, which would be expected after a straightforward CABG. With any impairment in functional status, however, mortality increased to 3.4%.
Furthermore, in patients with poor functional status, six-month mortality was 17.4%—“which is huge. However, this is relatively intuitive,” she added, “since most of the clinicians would agree that if the patient cannot perform their ADLs preoperatively, it will be challenging for them to do so after a major surgery.
“What’s interesting about this study, though, is the extent to which outcomes are improved from poor to even just marginal functional status, because you could theoretically decrease one’s mortality rate from an overwhelming 17% to an acceptable 3%.”
According to Dr. Ko, this presents a potential modifiable risk factor for these patients.
“The idea of improving one’s functional status preoperatively—‘prehab’—has been getting a lot of traction in the surgical arena,” said Dr. Ko, “and this is consistent with the future direction of our studies.”
Dr. Ko acknowledged several limitations to the study, including selection bias, since not all CABG patients underwent physical therapy three months before surgery.
In addition, given the observational nature of the study, only association—and not causality—can be shown.
“It will be ideal if the assessment of one’s functional status becomes standard practice,” Dr. Ko concluded, “but this assessment needs to be simplified first. If it takes an hour and a half to do so, there’s no way that this could be translated into clinical practice.”
Easier Assessment Needed
Mark Stafford-Smith, MD, CM, FASE, FRCPC, director of the adult cardiac anesthesia and critical care fellowship at Duke University School of Medicine, in Durham, N.C., who was the session moderator, said while intuitive, these results could lead to practical changes in care. To be feasible as assessment, however, Dr. Stafford-Smith agreed that modifications must be made.
“Rather than have each patient visit a physiotherapist for a full assessment, this test would need to be simplified to a handful of questions, or even one question, that would give the clinician enough information,” he said.
“Given that the signal for the problem seemed to be patients with very, very low function, even a question like, ‘Do you need help to go to the bathroom?’ might be enoug h for a functional test of whether or not a patient has this disability.”
Dr. Stafford-Smith also noted the therapeutic potential of modifying preoperative functional status with rehab.
“Whether or not that would modify a patient’s risks of outcome is a very important question that needs to be addressed,” he concluded.
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