What is the recommended evaluation and treatment approach for patients suspected of having coronary artery disease in a cardiac lab?

Cardiac Lab Evaluation for Suspected Coronary Artery Disease

For patients with suspected coronary artery disease presenting to a cardiac lab, non-invasive functional imaging for myocardial ischemia or coronary CT angiography (CTA) is the recommended initial diagnostic test, with selection based on pre-test probability of obstructive CAD. 1, 2

Initial Clinical Assessment

Obtain specific chest pain characteristics to classify presentation:

• Quality, location, duration, and triggering/relieving factors to categorize as typical angina (substernal chest discomfort provoked by exertion/emotion, relieved by rest/nitroglycerin), atypical angina (meets 2 of 3 criteria), or non-cardiac chest pain 1, 2
• Assess for angina equivalents including dyspnea with minimal exertion (such as dyspnea while talking), which is particularly significant when associated with other ischemic symptoms 3
• Determine stability: stable versus unstable angina (rest pain, accelerating pattern, or new-onset severe angina) 1, 3

Evaluate cardiovascular risk factors systematically:

• Smoking status, hyperlipidemia, diabetes mellitus, hypertension, family history of premature CAD, and postmenopausal status in women 1, 2
• Diabetes is particularly critical as it confers high risk for both macrovascular disease and concurrent hypertension/hyperlipidemia 1

Identify conditions that may precipitate functional angina:

• Increased oxygen demand: hyperthyroidism, hyperthermia, cocaine use, aortic stenosis, severe uncontrolled hypertension 1
• Decreased oxygen supply: anemia, hypoxemia from pulmonary disease, increased blood viscosity 1

Mandatory Initial Testing

Perform these tests immediately in all patients:

• 12-lead ECG within 10 minutes of presentation to distinguish STEMI from non-ST-elevation ACS 1, 4
• Resting echocardiography to quantify left ventricular function in all patients with suspected CAD 1, 2
• Full blood count including hemoglobin and white cell count 1
• Fasting plasma glucose and HbA1c; add oral glucose tolerance test if both are inconclusive 1
• Creatinine measurement with estimated renal function 1
• Lipid panel 1

If clinical instability or acute coronary syndrome is suspected:

• Repeated high-sensitivity troponin measurements to rule out myocardial necrosis 1, 3
• Continuous ST-segment monitoring during pain episodes 3

Diagnostic Test Selection Algorithm

For low to moderate pre-test probability (>5%-50% likelihood of obstructive CAD):

• Coronary CTA is the preferred initial test (Class I, Level B recommendation) 1, 5
• CTA provides anatomical assessment and plaque burden quantification for risk stratification 5
• CTA demonstrates mortality and morbidity benefits through enhanced preventive therapy, with long-term reduction in death and nonfatal MI 5

For moderate to high pre-test probability (>15%-85% likelihood of obstructive CAD):

• Functional imaging is recommended (stress SPECT, PET, stress cardiac MRI, or stress echocardiography) 1, 5
• Nuclear stress testing (SPECT or preferably PET) directly quantifies myocardial ischemia and scar, estimating risk of major adverse cardiac events 5
• Area of ischemia ≥10% of LV myocardium on SPECT/PET identifies high-risk patients requiring invasive evaluation 5

Critical contraindications to coronary CTA:

• Extensive coronary calcification, irregular heart rate, atrial fibrillation, significant obesity, or inability to cooperate with breath-hold commands 1, 5

Exercise Testing Indications

Exercise ECG is appropriate for:

• Patients without previous revascularization who have significant change in clinical status, can exercise, and have interpretable baseline ECG 1
• Assessment of exercise tolerance, symptoms, arrhythmias, blood pressure response, and event risk 1

Stress imaging (radionuclide or echocardiography) is required for:

• Patients who cannot exercise 1
• Baseline ECG abnormalities: Wolff-Parkinson-White syndrome, electronically paced ventricular rhythm, >1mm ST-segment depression at rest, or complete left bundle-branch block 1
• Previous revascularization with significant change in clinical status 1
• Equivocal or intermediate-risk results with exercise ECG 1

Sequential Testing Strategy

If coronary CTA shows CAD of uncertain functional significance:

• Proceed with functional imaging for myocardial ischemia (Class I recommendation) 1, 5
• Consider FFR-CT for stenoses 40-90% to assess functional significance, avoiding unnecessary invasive procedures 5

If stress testing is negative but symptoms persist:

• Consider coronary CTA to detect obstructive CAD and atherosclerotic plaque 5

Invasive Coronary Angiography Indications

Direct referral to invasive angiography is appropriate for:

• High clinical likelihood with severe symptoms refractory to medical therapy 1
• Typical angina at low exercise level with clinical evaluation indicating high event risk 1
• Marked limitation of ordinary activity (Canadian Cardiovascular Society class III) despite maximal medical therapy 1
• High-risk clinical profile with inadequate symptom response to medical treatment when revascularization is considered for prognosis improvement 1

For unstable angina with high-risk features:

• Accelerating symptoms, prolonged rest pain, pulmonary edema, new mitral regurgitation murmur, or significant ECG changes warrant coronary angiography 3

Invasive functional assessment (FFR) must be available and used to evaluate stenoses before revascularization, unless very high grade (>90% diameter stenosis). 1

Common Pitfalls to Avoid

• Do not rely solely on resting ECG for diagnosis: More than 50% of patients with chronic stable angina have normal resting ECG 1, 2
• Avoid coronary calcium scoring alone to identify obstructive CAD 1, 2
• Do not perform routine periodic cardiac testing without change in clinical status 1
• Test selection must be based on pre-test likelihood, not simply availability 5

Risk Stratification for Prognosis

Risk stratification should be based on:

• Clinical assessment combined with results of initial diagnostic tests 1, 2
• Stress imaging or coronary CTA (if local expertise permits), or exercise stress ECG (if significant exercise possible and ECG interpretable) 1, 2

High-risk features requiring aggressive management:

• Left ventricular dysfunction on echocardiography 1
• Extensive ischemia (≥10% of LV myocardium) on functional imaging 5
• Multi-vessel disease or left main stenosis on CTA or angiography 1