What is the best initial diagnostic test for a patient with congestive heart failure (CHF) and a low ejection fraction (EF), considering options such as myocardial perfusion scan, coronary angiography (coronary angio), or computed tomography angiography (CT angio)?

Coronary Angiography is the Best Initial Diagnostic Test for CHF with Low EF

For patients with congestive heart failure and low ejection fraction, invasive coronary angiography should be performed to identify revascularizable coronary artery disease, as this is the gold standard test that directly impacts treatment decisions and prognosis. 1

Why Coronary Angiography Takes Priority

The fundamental question in a patient with new-onset or established heart failure with reduced ejection fraction is whether the underlying etiology is ischemic, because this determination fundamentally changes management and prognosis. 1, 2

Coronary angiography receives a Class I recommendation (Level B) from the American College of Cardiology for patients with heart failure and low ejection fraction when:

• The patient has angina or chest pain symptoms 3, 1
• There is suspected or known coronary artery disease 3, 2
• The patient would be a candidate for revascularization 1

The European Society of Cardiology similarly gives a Class I recommendation (Level B) for invasive coronary angiography in heart failure patients with LVEF ≤35% when obstructive CAD is suspected, specifically with a view toward improving prognosis through coronary artery bypass grafting. 3

The Critical Clinical Decision Point

The key determining factor is whether the patient is a revascularization candidate—not symptom severity alone. 1 If the patient has absolute contraindications to revascularization (severe comorbidities, advanced age with poor functional status, patient preference), then invasive angiography is not indicated regardless of symptoms. 1

However, if the patient is medically stable enough for angiography and would be a candidate for revascularization based on age, comorbidities, and functional status, then coronary angiography should be performed. 1

Why Non-Invasive Tests Are Secondary Options

Myocardial Perfusion Scan (SPECT)

While myocardial perfusion imaging can assess ischemia and viability, it serves a different role. 3 The guidelines position non-invasive stress imaging as a Class IIa recommendation (reasonable to consider) rather than the primary diagnostic approach. 3

Non-invasive stress testing may be considered (Class IIb) before revascularization decisions to assess myocardial ischemia and viability, but this is a weaker recommendation than proceeding directly to angiography. 3

The REVIVED-BCIS2 trial notably showed that viability testing did not offer prognostic benefit in patients with severe LV systolic dysfunction, which has tempered enthusiasm for viability-first approaches in the United States. 3

CT Angiography

Cardiac CT angiography is recommended primarily for patients with low-to-intermediate pre-test probability of coronary artery disease or those with equivocal non-invasive stress tests. 3

For patients with heart failure and LVEF >35% with low or moderate (>5%-50%) pre-test likelihood of obstructive CAD, CCTA or functional imaging receives a Class I recommendation. 3 However, in patients with low EF (typically ≤35-40%), the pre-test probability of significant CAD is inherently higher, making invasive angiography more appropriate. 3

CT angiography has limitations including radiation exposure, contrast nephropathy risk, and inability to provide hemodynamic information or immediate revascularization options. 3

The Evidence Supporting Revascularization in Viable Myocardium

Surgical coronary revascularization in patients with HFrEF due to ischemic cardiomyopathy leads to lower long-term all-cause mortality and cardiovascular hospitalizations. 4 The STICHES trial demonstrated that CABG plus medical therapy was superior to medical therapy alone in HFrEF patients with CAD amenable to CABG. 3

Historical data shows that among patients with chronic coronary artery disease and depressed LVEF presenting with heart failure symptoms, 61% had viable myocardium and could be considered for coronary revascularization. 5 Revascularization improves left ventricular ejection fraction, heart failure symptoms, and prognosis in patients with viable myocardium. 6

Practical Algorithm for Your Patient

1. First, establish that echocardiography has confirmed low EF (this should already be done as a Class I recommendation for all suspected HF patients). 3, 7

2. Assess revascularization candidacy: Consider age, comorbidities, functional status, and patient goals. 1

3. If revascularization candidate → Proceed directly to invasive coronary angiography (Class I recommendation for LVEF ≤35% with suspected CAD). 3, 1

4. If NOT a revascularization candidate → Skip angiography and focus on guideline-directed medical therapy. 1

5. Non-invasive testing (perfusion scan or CT angio) is reserved for:

   • Patients with LVEF >35% and low-to-intermediate pre-test probability of CAD 3
   • Situations where invasive angiography carries prohibitive risk but revascularization might still be considered 3
   • Equivocal clinical scenarios where establishing ischemic etiology would change management 3

Common Pitfalls to Avoid

Do not delay coronary angiography in favor of non-invasive testing when the patient is a clear revascularization candidate with low EF and suspected ischemic etiology. 1, 2 The guidelines have moved away from mandatory viability testing before revascularization decisions, particularly after REVIVED-BCIS2. 3

Do not order coronary angiography if the patient has absolute contraindications to revascularization—this exposes them to procedural risk without therapeutic benefit. 1

Ensure optimal medical therapy is initiated regardless of the diagnostic pathway, including ACE inhibitors, beta-blockers, mineralocorticoid receptor antagonists, and SGLT2 inhibitors. 3, 2