What is the approach to risk stratify a patient for cardiac catheterization (cardiac cath)?

Risk Stratification for Cardiac Catheterization

Risk stratification for cardiac catheterization should integrate clinical presentation, ECG findings, cardiac biomarkers, and validated risk scores to determine urgency and appropriateness of invasive evaluation.

Initial Clinical Assessment

Determine the clinical scenario first, as this dictates the entire approach:

• Acute presentations (UA/NSTEMI) require immediate risk stratification using the TIMI or GRACE risk scores, with urgent catheterization indicated for refractory angina, hemodynamic instability, life-threatening arrhythmias, or recurrent angina with ST-depression ≥2mm 1
• Chronic coronary syndrome requires assessment of symptom severity, functional capacity, and noninvasive testing results before considering catheterization 1
• Pre-transplant evaluation (liver or kidney) requires screening based on multiple CAD risk factors (≥3 factors including diabetes, age >60 years, smoking, hypertension, prior CVD) 1

Risk Score Calculation for Acute Coronary Syndromes

Use the TIMI risk score for UA/NSTEMI patients, assigning 1 point for each of 7 variables:

• Age ≥65 years 1
• ≥3 CAD risk factors (family history, hypertension, hypercholesterolemia, diabetes, smoking) 1
• Known CAD (stenosis ≥50%) 1
• Aspirin use in prior 7 days 1
• Severe angina (≥2 episodes within 24 hours) 1
• ST-segment deviation ≥0.5mm 1
• Elevated cardiac biomarkers 1

Interpret TIMI score to determine catheterization timing:

• Score 0-2 (low risk): Conservative strategy acceptable with stress testing before discharge; catheterization only if positive stress test 1
• Score 3-4 (intermediate risk): Early invasive strategy within 72 hours recommended 1
• Score 5-7 (high risk): Urgent invasive strategy within 24 hours indicated 1

High-Risk Features Requiring Urgent Catheterization

Proceed immediately to catheterization (within 2 hours) if any of these features are present:

• Refractory angina despite maximal medical therapy 1
• Hemodynamic instability or cardiogenic shock 1
• Sustained ventricular tachycardia or ventricular fibrillation 1
• Acute heart failure with pulmonary edema likely due to ischemia 1
• Recurrent angina with dynamic ST-segment changes (≥2mm depression) 1

Intermediate-Risk Features for Early Invasive Strategy

Plan catheterization within 24-72 hours if any of these are present:

• Elevated troponin levels without high-risk features 1
• Dynamic ST or T-wave changes (≥0.5mm) even if asymptomatic 1
• Diabetes mellitus with positive biomarkers 1
• Reduced renal function (GFR <60 mL/min/1.73m²) 1
• Depressed LV ejection fraction <40% 1
• Early post-MI angina 1
• Prior PCI within 6 months or prior CABG 1

Low-Risk Criteria for Conservative Strategy

Avoid early catheterization if ALL of the following are present:

• No recurrence of chest pain during observation 1
• No signs of heart failure 1
• Normal or unchanged ECG at presentation and 6-12 hours later 1
• Negative troponins at presentation and 8-12 hours after symptom onset 1
• TIMI risk score 0-2 1

For these patients, perform stress testing before discharge; catheterization only if stress test is positive for inducible ischemia 1

Special Populations Requiring Modified Risk Assessment

Liver transplant candidates with coagulopathy:

• Expect higher bleeding complications (14.8% vs 3.7% in controls) and vascular complications (5.7% pseudoaneurysms) 1
• Anticipate transfusion requirements: RBC (16%), FFP (51.7%), platelets (48.3%) 1
• Proceed with catheterization despite coagulopathy if noninvasive testing suggests high-risk CAD 1

Patients with preserved functional capacity:

• Good functional capacity (≥4 METs) does not eliminate need for catheterization if objective ischemia is documented (e.g., abnormal FFR ≤0.80) 2
• Minimal symptoms with abnormal physiologic testing still warrant intervention 2

Contraindications to Outpatient/Ambulatory Catheterization

Absolute contraindications (must be inpatient):

• Any interventional procedure planned (PCI, valvuloplasty) 1, 3
• Geographic remoteness (>1 hour from facility) 1
• Suspected severe pulmonary hypertension 1
• Recent stroke (<1 month) 1
• Severe peripheral vascular disease 1
• LV ejection fraction ≤35% 1
• Uncontrolled systemic hypertension 1
• Active anticoagulation or bleeding diathesis 1

Common Pitfalls to Avoid

• Do not rely on traditional CAD risk factors alone in acute presentations—symptoms, ECG, and biomarkers are far more predictive of ACS than risk factor profiles 1
• Do not delay catheterization in high-risk patients based on weekend presentation—although timing may be delayed on weekends (median 46.3 vs 23.4 hours), outcomes remain similar if performed within 48 hours 1
• Do not assume normal initial troponin excludes ACS—remeasure at 8-12 hours after symptom onset as sensitivity improves with serial measurements 1
• Do not use stress testing in unstable patients—proceed directly to catheterization if high-risk features are present 1
• Do not discharge patients with positive biomarkers without definitive evaluation—elevated troponin mandates either early invasive strategy or very close observation with repeat risk assessment 1