From the Guidelines
Coronary fractional flow reserve (FFR) studies are indicated in patients with intermediate coronary stenoses (50-70% narrowing) identified on CT coronary angiography, where the hemodynamic significance is uncertain, as evidenced by the 2012 ACCF/AHA/ACP/AATS/PCNA/SCAI/STS guideline 1. The role of FFR in these patients is to determine whether the identified stenoses are causing significant reduction in blood flow, which in turn guides decisions about revascularization. This is particularly important when multiple lesions are present or when the anatomical findings do not clearly correlate with the patient's symptoms.
Key Points:
- FFR is valuable for assessing the hemodynamic significance of intermediate coronary stenoses.
- The procedure involves measuring pressure differences across a stenosis during maximum hyperemia.
- An FFR value ≤0.80 generally indicates a flow-limiting lesion that would benefit from intervention, as suggested by the guideline 1.
- Coronary artery calcium (CAC) scoring plays a complementary role by quantifying atherosclerotic burden and predicting cardiovascular risk.
CAC Scoring:
CAC scoring is most useful for risk stratification in asymptomatic patients with intermediate cardiovascular risk, helping guide preventive therapy decisions.
- A high calcium score (>300 Agatston units) suggests significant coronary atherosclerosis, but does not necessarily indicate flow-limiting stenoses.
- The presence of a nonzero CAC score has a high sensitivity (98%) for detecting significant CAD on invasive coronary angiography, but a lower specificity (40%), as reported in a meta-analysis of 18 studies 1. While CAC identifies the presence of atherosclerosis, FFR determines the functional significance of specific lesions, making them complementary tools in coronary artery disease evaluation. In patients with a CAC score of zero, the frequency of false negative exams (i.e., significant CAD in the absence of CAC) is not well established, but it is more common in younger patients, as noted in the guideline 1.
From the Research
Indications of CFFR Studies
- CFFR (Coronary Computed Tomography Angiography-derived Fractional Flow Reserve) studies are used to evaluate the functional significance of coronary artery stenoses in patients with suspected coronary artery disease 2, 3.
- CFFR is a non-invasive method that combines anatomical and functional information to assess the hemodynamic severity of coronary artery disease 4, 5.
- The indications of CFFR studies include:
Role of CAC (Calcium Score)
- CAC (Coronary Artery Calcium) score is a measure of the amount of calcium in the coronary arteries, which is a marker of atherosclerotic plaque burden 2.
- CAC score is used to assess the risk of coronary artery disease and to guide further testing and treatment 2.
- However, the provided studies do not specifically discuss the role of CAC score in CFFR studies, but rather focus on the use of CFFR to evaluate the functional significance of coronary artery stenoses 2, 3, 4, 5, 6.
Diagnostic Accuracy of CFFR
- The diagnostic accuracy of CFFR has been evaluated in several studies, which have shown that it is a reliable method for detecting hemodynamically significant coronary artery disease 4, 5.
- CFFR has been compared to other imaging modalities, such as coronary computed tomography angiography (CCTA), single-photon emission computed tomography (SPECT), and positron emission tomography (PET), and has been shown to have higher diagnostic accuracy for vessel-specific ischemia 5.
- The prognostic value of CFFR has also been evaluated, and studies have shown that it is associated with clinical outcomes, such as all-cause mortality and myocardial infarction 6.