What is the pre-operative risk for a patient with a Metabolic Equivalent of Task (METS) of approximately 4?

From the Guidelines

A patient with a Metabolic Equivalent of Task (METS) of approximately 4 is at relatively low risk for perioperative cardiac events. This is based on the 2024 AHA/ACC/ACS/ASNC/HRS/SCA/SCCT/SCMR/SVM guideline for perioperative cardiovascular management for noncardiac surgery, which states that stable patients with exercise capacity ≥4 METs are at relatively low risk for perioperative cardiac events 1.

Key Points to Consider

• The patient's functional capacity indicates they can perform activities like light housework, climbing a flight of stairs, or walking at a moderate pace, which suggests a relatively low risk for perioperative cardiac events.
• According to the guideline, routine preoperative stress testing should not be performed in patients with adequate functional capacity, such as those with a METS of 4 or higher 1.
• The benefits of preoperative revascularization appear to be limited, and routine coronary revascularization does not reduce mortality or risk for MI, as demonstrated by large RCTs 1.

Recommendations

• Proceed with surgery without additional cardiac testing for low-to-moderate risk procedures, as the patient's METS of 4 indicates a relatively low risk for perioperative cardiac events.
• Consider additional cardiac testing for high-risk surgeries or if the patient has multiple cardiac risk factors, such as coronary artery disease, heart failure, diabetes, renal insufficiency, or cerebrovascular disease.
• The patient's functional capacity correlates with cardiovascular reserve, and those with higher METS have better ability to increase cardiac output during the stress of surgery 1.

From the Research

Pre-operative Risk Assessment

The pre-operative risk for a patient with a Metabolic Equivalent of Task (METS) of approximately 4 can be assessed based on various studies.

• A study published in 2021 2 found that patients with <4 METs had a higher incidence of diabetes mellitus, peripheral arterial disease, history of smoking, obesity, and chronic obstructive pulmonary disease.
• The same study found that there was no significant difference in survival between patients with a functional capacity of more than 4 METs and those with less than 4 METs.
• Another study published in 2018 3 compared estimates of patients' METs between preoperative assessment by medical history and quantified assessment of METs via exercise cardiac stress testing, and found that exercise cardiac stress test quantified METs were on average 3.3 METs higher than the METs estimated by preoperative evaluation history.
• A study published in 2022 4 found that the MET-REPAIR Questionnaire correlates with measured METs, but all utilized forms of self-reported physical activity overestimate measured METs.

Risk Factors

Patients with a METS of approximately 4 may have a higher risk of:

• Diabetes mellitus
• Peripheral arterial disease
• History of smoking
• Obesity
• Chronic obstructive pulmonary disease
• These risk factors can be assessed using various tools, such as the MET-REPAIR Questionnaire 4 or exercise cardiac stress testing 3.

Assessment Tools

Various assessment tools can be used to evaluate pre-operative risk, including:

• The MET-REPAIR Questionnaire 4
• Exercise cardiac stress testing 3
• The PRO-score 5
• The pre-operative fitness score 6
• These tools can help identify patients who may be at higher risk of complications or mortality, and guide further evaluation and management.