When to assess for viability in patients with coronary artery disease (CAD) and left ventricular dysfunction (LVD)?

When to Assess for Viability in CAD with Left Ventricular Dysfunction

Viability assessment is reasonable when planning revascularization in heart failure patients with coronary artery disease and left ventricular dysfunction, but only if the patient is a revascularization candidate. 1

Clinical Algorithm for Viability Assessment

Step 1: Determine Revascularization Candidacy First

• Do not perform viability testing if the patient is not eligible for revascularization of any kind 1
• This is a Class IIa recommendation with Level of Evidence C, meaning viability assessment should be bypassed entirely in patients who cannot undergo revascularization due to comorbidities, surgical risk, or patient preference 1

Step 2: Assess Clinical Presentation

Patients WITH Angina:

• Proceed directly to coronary angiography without viability testing 1
• Revascularization is indicated for significant ischemic chest pain regardless of viability status 1
• There is little role for noninvasive cardiac testing in symptomatic patients with angina and impaired ventricular function 1

Patients WITHOUT Angina:

• Viability assessment is reasonable before considering revascularization 1
• This applies specifically to patients presenting with de novo heart failure who have known CAD but no anginal symptoms 1

Step 3: Consider the Evidence Base

The recommendation for viability testing carries important caveats:

• The STICH trial substudy (2011) found that viability assessment did not identify patients with differential survival benefit from CABG compared to medical therapy alone 1, 2
• However, observational studies demonstrate that patients with viable myocardium who undergo revascularization show recovery of function and clinical improvement 1
• The presence of viable myocardium was associated with greater likelihood of survival, though this relationship was not significant after adjustment for baseline variables 2

Step 4: Quantify Viability When Testing is Performed

If viability assessment is undertaken, the amount of viable myocardium matters:

• Large amounts of dysfunctional but viable myocardium (≥6 segments) predict the best outcomes after revascularization 3
• Patients with 2-5 viable segments have intermediate benefit 3
• Patients with predominantly non-viable myocardium have limited benefit from revascularization 4, 3

Step 5: Choose Appropriate Imaging Modality

Multiple modalities are reasonable (Class IIa):

• SPECT imaging with thallium-201 or Tc-99m sestamibi 1
• PET imaging with FDG (higher sensitivity than SPECT for detecting viable myocardium) 1
• Cardiac MRI with late gadolinium enhancement (assesses scar burden and viability) 1
• Dobutamine echocardiography (good positive predictive value but may miss 25-50% of viable segments) 1, 5

Critical Pitfalls to Avoid

• Do not perform routine viability testing in all heart failure patients with CAD - it should be selective and only when revascularization is being considered 1
• Do not delay angiography in patients with angina to perform viability testing first - proceed directly to catheterization 1
• Do not assume viability testing will definitively predict clinical outcomes - the STICH trial showed no differential survival benefit based on viability status 2
• Do not forget that at least 3 years of follow-up may be necessary to see the prognostic benefit of revascularization in patients with viable myocardium 4

Timing Considerations

The optimal timing is:

• Before making the final decision about revascularization in patients with known CAD, LV dysfunction, and no angina 1
• After establishing that the patient is medically suitable for revascularization 1
• When the presence or absence of viable myocardium would change management decisions 1

The evidence suggests a measured approach: viability testing has a role in select patients being considered for revascularization, but it is not a routine test and should not be performed when revascularization is either clearly indicated (angina present) or clearly not an option (patient ineligible) 1.