Cardiac Risk Assessment in Noncardiac Surgery
Immediate Assessment: Identify Active Cardiac Conditions
First, determine if active cardiac conditions are present that mandate intensive management and may require delay or cancellation of elective surgery. These conditions include unstable coronary syndromes, unstable or severe angina, recent MI (within 30 days), decompensated heart failure, significant arrhythmias, and severe valvular disease 1. If any of these are present, surgery should be postponed unless emergent 1.
Step-by-Step Risk Stratification Algorithm
Step 1: Assess Surgical Risk
Categorize the planned surgery by 30-day cardiac event rate 1:
Low-risk surgery (<1% cardiac event rate): Endoscopic procedures, superficial procedures, cataract surgery, breast surgery, ambulatory surgery 1. These patients can proceed directly to surgery without further cardiac testing 1.
Intermediate-risk surgery (1-5% cardiac event rate): Intraperitoneal and intrathoracic surgery, carotid endarterectomy, head and neck surgery, orthopedic surgery, prostate surgery 1.
High-risk surgery (>5% cardiac event rate): Aortic and major vascular surgery, peripheral vascular surgery 1.
Step 2: Calculate Clinical Risk Using the Revised Cardiac Risk Index (RCRI)
The RCRI is the ACC/AHA-endorsed primary risk stratification tool and should be calculated for all patients. 2 Assign one point for each of the following six factors 1, 2:
- History of ischemic heart disease (prior MI, positive stress test, current angina, pathologic Q waves on ECG)
- History of compensated or prior heart failure
- History of cerebrovascular disease (stroke or TIA)
- Diabetes mellitus requiring insulin therapy
- Chronic renal insufficiency (creatinine >2 mg/dL)
- High-risk surgery (as defined above)
Risk stratification by RCRI score 2:
- 0-1 points: Low risk (<1% major adverse cardiac events)
- 2 points: Moderate risk
- ≥3 points: High risk
Step 3: Assess Functional Capacity
Functional capacity is a critical determinant—patients who can climb 2 flights of stairs or achieve ≥4 METs during normal daily activities can generally proceed to surgery without further cardiac testing, even with known cardiovascular disease. 1, 3, 4, 5
Functional capacity categories 1:
- Poor (<4 METs): Cannot walk 1-2 blocks on level ground or climb 1 flight of stairs
- Moderate (4-10 METs): Can climb stairs, do heavy housework, play golf or doubles tennis
- Excellent (>10 METs): Can participate in strenuous sports like swimming, singles tennis, or skiing
If functional capacity is ≥4 METs and the patient is asymptomatic, proceed to surgery regardless of clinical risk factors 1, 4.
Step 4: Determine Need for Further Testing
For patients with poor functional capacity (<4 METs), symptomatic status, or unknown functional capacity 1, 4:
0-1 clinical risk factors: Proceed to surgery without further testing 1, 4
2 clinical risk factors: Either proceed to surgery with beta-blocker therapy OR consider noninvasive stress testing only if results would change management 1, 4
≥3 clinical risk factors undergoing vascular surgery: Consider noninvasive testing only if it will change management 1. Note that RCRI performs poorly in vascular surgery populations; consider using the NSQIP calculator instead 2.
≥3 clinical risk factors undergoing intermediate-risk surgery: Insufficient data exist to determine optimal strategy; consider proceeding with tight heart rate control or testing if it will change management 1
Essential Preoperative Testing
Baseline Studies
12-lead ECG: Obtain for patients with recent chest pain or ischemic symptoms undergoing intermediate- or high-risk surgery, asymptomatic patients with diabetes mellitus, and patients with cardiovascular risk factors undergoing intermediate- or high-risk procedures 1, 2, 3
Complete blood count: Order for patients with diseases increasing anemia risk (liver disease, hematologic disorders, chronic kidney disease) or when significant blood loss is anticipated, as hematocrit <28% increases perioperative ischemia risk 1, 3
Electrolytes and creatinine: Obtain for patients with chronic kidney disease, hypertension, heart failure, complicated diabetes, liver disease, or those taking diuretics, ACE inhibitors, ARBs, NSAIDs, or digoxin 3
Advanced Risk Assessment
For patients with RCRI ≥2, measuring preoperative NT-proBNP and/or troponin enhances risk prediction, improving discrimination by a median delta c-statistic of 0.12 over RCRI alone. 2 Consider troponin testing both preoperatively and 48-72 hours postoperatively in high-risk patients 1, 3.
The NSQIP Surgical Risk Calculator may offer superior discrimination compared to RCRI (median delta c-statistic 0.11 higher), particularly for procedure-specific risk assessment. 2
Cardiac Imaging
Resting echocardiography: Obtain for patients with current or poorly controlled heart failure, and consider for patients with prior heart failure or dyspnea of unknown origin 1, 3
Stress testing: Reserve for patients at higher risk with poor functional capacity (<4 METs) undergoing high-risk surgery, and only if results would change perioperative medical, anesthesia, or surgical approaches 1, 4, 5. Routine stress testing is not predictive and should not be performed routinely 4.
Critical Pitfalls to Avoid
Do not perform routine coronary revascularization before noncardiac surgery solely to reduce perioperative cardiac events—it does not reduce risk and should only be done for independent cardiac indications like unstable angina 4, 5
Emergency surgery patients should proceed immediately—focus on perioperative medical optimization rather than extensive testing, as consequences of delay outweigh benefits 2
Elective surgery must be delayed if dual antiplatelet therapy cannot be continued: 14 days after balloon angioplasty, 30 days after bare-metal stent, and optimally 365 days after drug-eluting stent 4
Age is an independent risk factor: Patients 66-85 years have OR 2.67 for delirium, and those >85 years have OR 6.24 compared to patients ≤65 years 2
Male sex independently increases risk (OR 1.28) and BMI <18.5 substantially increases delirium risk (OR 2.25) 2