Local Coverage Article Response to Comments

Response to Comments: Non-Invasive Fractional Flow Reserve (FFR) for Ischemic Heart Disease


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Response to Comments: Non-Invasive Fractional Flow Reserve (FFR) for Ischemic Heart Disease
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Response to Comments
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As an important part of Medicare Local Coverage Determination (LCD) development, National Government Services solicits comments from the provider community and from members of the public who may be affected by or interested in our LCDs. The purpose of the advice and comment process is to gain the expertise and experience of those commenting.
We would like to thank those who suggested changes to the draft of the Non-Invasive Fractional Flow Reserve (FFR) for Ischemic Heart Disease LCD.
The official notice period for the final LCD begins on 02/09/2023 and the final determination will become effective on 04/01/2023.

Response To Comments


American College of Cardiology (ACC)

ACC welcomes that many of the proposed changes to the LCD align with the 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain. We support the update to the definitions of intermediate and high-risk to reflect the definitions in the 2021 AHA/ACC/multisociety Chest Pain Guideline. We also support the expansion of the stenosis range to 40-90% and the vessel-specific limitations to align with the guidelines. Fractional flow reserve with computed tomography (FFR-CT) is most useful to guide clinical decision-making for proximal-mid vessel stenoses of 40-90% severity.

1 FFR-CT turnaround times may impact prompt clinical care decisions. However, the use of FFR-CT does not require additional testing, as would be the case when adding stress testing. ACC supports the indication in the proposed LCD of FFR-CT usage as an alternative to stress testing. The College also supports the removal of the BMI limitations based on new data. Contemporary scanners contain improved hardware and software components, such as dual-source CT and wide-detector scanners, which allow quality imaging of the most difficult patient anatomies. As for aortic stenosis (AS), we welcome the removal from the exclusion. However, the College also recognizes that further research is necessary to continue to assess the clinical utility, safety, and feasibility of FFR-CT in this patient cohort and that administration of nitroglycerin to this subset of patients for diagnostic imaging is controversial.

2 In addition to the studies noted in the proposed LCD’s summary of evidence on the optimal cutoff value of FFR derived from FFR-CT, the College would like to bring your attention to additional evidence. A 2019 study by Matsumura-Nakano, et al. concluded “referral to invasive coronary angiography should be considered individually in the range of FFR-CT 0.71 to 0.80, whereas dichotomous decision could be made in FFR-CT ≤0.70 and >0.80. Future prospective studies evaluating clinical outcomes are needed to establish optimal FFR-CT-based diagnostic algorithm.”

3 A 2022 study by Mickley, et al. concluded “most patients with Agatston Score (AS) >399 had FFRCT ≤0.80. Using ICA/FFR as the reference revealed a moderate diagnostic accuracy of colocation FFR-CT. Compared with the lowest per-patient FFR-CT, colocation FFR-CT measurement improved diagnostic accuracy and specificity. The 90-day follow-up was favorable with few coronary revascularizations and no major clinical events occurring in patients with FFR-CT>0.80.”

4 This study showed low specificity (32%) of FFR-CT compared to invasive FFR in patients with AS >399, the population where FFR-CT is used most often. As optimal cutoff values of FFR-CT have not yet been adequately defined, the decision to perform FFR-CT should not be tied to a specific action item and decision making cut points must reflect the current state of the evidence. Appropriate use of FFR-CT can lead to fewer unnecessary diagnostic catheterizations making it a cost-effective diagnostic test. ACC supports the expansion of the coverage criteria for FFR-CT to reflect the 2021 AHA/ACC/Multisociety Chest Pain Guideline and the current state of the evidence.

NGS appreciates the comments and additional supporting literature sent in by the American College of Cardiology.


American Society of Nuclear Cardiology,

ASNC is supportive of CCTA for appropriate, proven indications and agrees that CCTA is a useful diagnostic tool that physicians frequently use in daily clinical practice. However, ASNC has concerns about overuse of FFR-CT in certain circumstances.
First, there are challenges associated with FFR-CT and logistics of use. The service costs more than three times the CCTA itself and adds only one additional metric (simulation of FFR based on static anatomic images). We are concerned that recommending a test with a low specificity and low positive predictive value (as mentioned in the NCD for common use), could lead to unnecessary resource utilization. A multicenter study from the UK recently presented in abstract form shows that FFR-CT increased the cost of chest pain evaluation in the UK by 1700 UK pounds, mainly due to the low specificity and low positive predictive value (specificity was less than 30%).
1 The low specificity was also demonstrated in the DEFACTO study, in which the core lab specificity of FFR-CT versus invasive FFR was 54%.

2 In addition, FFR-CT does not provide a true physiologic assessment or evaluate coronary microvascular dysfunction as can be done with standard functional testing. There is significant imprecision at the intermediate range of stenosis (Heartflow lists one standard deviation as 0.09 - 0.10 at intermediate range).

3 This imprecision makes FFR-CT inadequate for guiding management of individual patients with intermediate coronary stenoses, which is the patient population in which physiologic assessment of stenosis severity is most needed for guiding revascularization.
1 Hothi et. al. 136 The use and efficacy of ffr-ct – a real-world multi-centre audit of clinical data and cost-analysis,
10.1136/heartjnl-2022-BCS.136 available at https://heart.bmj.com/content/108/Suppl_1/A102
2 Min, James K., et al. "Diagnostic accuracy of fractional flow reserve from anatomic CT angiography." Jama 308.12
(2012): 1237-1245.
3 https://www.accessdata.fda.gov/cdrh_docs/reviews/DEN130045.pdf

From the summary of evidence section, the writers cite only the studies that are positive and funded by HeartFlow. Published studies that are not funded by HeartFlow show significantly lower accuracy are not included. Balanced evidence should be presented. The FACC study shows low specificity (32%) of FFR-CT compared to invasive FFR in patients with CAC>400, a population where FFR-CT is often used despite expert recommendations against use of FFR-CT for patients with heavily calcified coronary arteries.

4 A meta-analysis by Cook et al. demonstrated that the pooled accuracy of FFR-CT is 46.1% (95% CI, 42.9%-49.3%) for FFR-CT values ranging from 0.70 to 0.80, which are often found in the setting of intermediate coronary stenoses when an accurate functional assessment is required. The diagnostic accuracy of FFRCT is much less clinically relevant in the setting of obviously normal arteries (with normal FFRCT and critically stenotic lesions (with very low FFR-CT).

5 There is concern that cardiologists less familiar with the strengths and limitations of FFR-CT will refer all patients with an FFR-CT < 0.80 for invasive coronary angiography, despite the low accuracy of FFR-CT of only 46%. This will result in increased healthcare costs (as documented in the UK study referenced above).

Finally, we have concerns about the use of FFR-CT for patients with severe aortic stenosis. The LCD cites a small study of 42 patients with aortic stenosis who were administered sublingual nitroglycerin prior to CCTA6 . The accuracy of FFR-CT is further reduced if nitroglycerin is not used prior to CCTA. The US FDA approval and HeartFlow's prescribing guidance recommend against using FFR-CT if nitroglycerin is not administered prior to the CCTA. Most CCTA laboratories do not feel comfortable administering nitroglycerin to patients with severe aortic stenosis and these CCTA studies should not be sent for FFR-CT measurements. CCTA is a useful tool which we support for patients with appropriate indications, but are concerned about the potential overuse of FFR-CT.

NGS appreciates the comments sent in by the American Society of Nuclear Cardiology and would like to refer to the additional literature sent in by the ACC to answer some of the concerns namely the fact that there is now a non HeartFlow sponsored, 260 patient study which showed moderate diagnostic accuracy of colocation FFR-CT. When it comes to patients with severe aortic stenosis we feel that providers would need to use their discretion as to whether nitroglycerin can be tolerated by their patient or not. NGS is updating this policy to be in line with the 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain.

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