What are the indications for CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) studies in a patient with computed tomography (CT) coronary angiography?

From the Guidelines

Coronary Fractional Flow Reserve (CFFR) studies are indicated in patients who have undergone CT coronary angiography when there is intermediate coronary stenosis and the functional significance of the lesion remains uncertain, as recommended by the 2019 ESC guidelines 1. The indications for CFFR studies in patients with CT coronary arteries done include:

• Evaluating borderline lesions
• Assessing multiple stenoses to identify the culprit lesion
• Determining the need for revascularization in patients with stable coronary artery disease
• Guiding decision-making in patients with discordance between symptoms and anatomical findings CFFR provides a physiological assessment by measuring pressure differences across a stenosis during maximum hyperemia, typically induced with adenosine 140 mcg/kg/min intravenously 1. According to the 2019 ESC guidelines, a CFFR value ≤0.80 indicates a hemodynamically significant stenosis that would likely benefit from revascularization, while values >0.80 suggest medical therapy may be sufficient 1. The use of CFFR is supported by the European Heart Journal, which recommends invasive functional assessment, including CFFR, to evaluate stenoses before revascularization, unless very high grade (>90% diameter stenosis) 1. In patients with mild or no symptoms, ICA complemented by invasive physiological guidance (FFR/iwFR) is recommended for patients on medical treatment in whom non-invasive risk stratification indicates a high event risk and revascularization is considered for improvement of prognosis 1. Overall, CFFR studies are a valuable tool in the management of patients with coronary artery disease, allowing for a more personalized and effective treatment approach, and ultimately improving patient outcomes and resource utilization 1.

From the Research

Indications of CFFTR Studies

The indications of CFFTR studies in a patient who has undergone CT coronary arteries are not directly related to the coronary artery disease diagnosis. However, the studies provide insight into the relationship between CFTR function and sweat chloride levels.

• CFFTR studies, such as those using ivacaftor, have shown a decrease in sweat chloride levels, which is a measure of CFTR function 2.
• The relationship between sweat chloride levels and CFTR function is complex, and multiple factors can influence disease severity 2.
• Recent guidelines for the diagnosis of cystic fibrosis have changed the intermediate sweat chloride concentration range, which may impact the detection of cystic fibrosis among patients 3.
• Coronary CT angiography is a useful tool for assessing suspected coronary artery disease, but its relationship to CFFTR studies is not directly relevant 4, 5.
• The CHEC-SC study aims to determine the relationship between sweat chloride response and clinical outcomes in people with cystic fibrosis on commercially approved CFTR modulators, which may provide further insight into the indications of CFFTR studies 6.

Relationship between CFFTR Studies and Coronary Artery Disease

There is no direct relationship between CFFTR studies and coronary artery disease diagnosis. However, the use of CT coronary angiography for evaluating coronary artery disease may provide additional information on the patient's cardiovascular health 4, 5.

• CT coronary angiography can detect coronary artery stenoses and provide information on the coronary artery wall 5.
• The high negative predictive value of a normal CT coronary angiogram may be useful for reliable exclusion of coronary artery stenosis 5.
• The relationship between CFFTR studies and coronary artery disease is not well established, and further research is needed to understand any potential connections 2, 3, 6.