Computed Tomography-derived Fractional Flow Reserve in the Systematic Triage of Emergency Department Acute Chest Pain Patients to Treatment. (The CTFFR-STAT Trial)
Phase: NA
Conditions: Heart Disease, Coronary, Chest Pain, Acute Coronary Syndrome
Sponsor: Corewell Health East

 
 
 
Study Protocol 
 
Study Title: Computed Tomography-derived Fractional Flow Reserve in the 
Systematic Triage of emergency department Acute chest pain patients to 
Treatment. (The CTFFR-STAT trial).  
Version Date:  January 26, 2018 
IRB Number:   2017-272 
NCT Number:  NCT03263806 
 
Principal Investigator: Gilbert Raff, MD  
Co-Investigators: 
 
Amr Abbas, MD 
Neil Bilolikar, MD 
Kavitha Chinnaiyan, MD 
David Forst, MD 
Michael Gallagher, MD 
Robert Safian, MD  
Mazen Shoukfeh, MD 
Robert Swor, DO  
 
Hospital Address: William Beaumont Hospital 
                                   3601 West 13 Mile Road 
                                    Royal Oak, MI. 48085 
                                    U.S.A. 

 
 
The CT-STAT, ROMICAT and ACRIN randomized trials established that coronary CTA (CCTA) 
is safe and more efficient than alternative diagnostic strategies (such as stress testing) for 
low- intermediate risk acute chest pain (ACP) patients with suspected acute coronary 
syndromes1-3, and current Appropriate Use Criteria consider CCTA in ACP patients with low 
to intermediate pre-test probability as appropriate4,5. Studies at Beaumont and other 
institutions have shown that approximately 75% of patients undergoing CCTA for ED ACP can 
be immediately triaged to discharge and 10% triaged to admission due to severe CAD. 
However, approximately 15% of patients with intermediate level stenosis (>50% but <90%) 
need additional testing, as this degree of anatomic narrowing does not reliably predict flow 
limitation as the cause of symptoms. Consequently, many such patients are admitted for 
stress testing or invasive coronary angiography (CATH) with subsequent negative results. An 
admission for chest pain diagnosis commonly incurs costs between $12-25,000. Data from the 
National Cardiovascular Disease Registry in nearly 400,000 patients demonstrated that only 
38% of patients undergoing CATH for chronic chest pain had obstructive coronary disease in 
spite of routine stress testing in the majority, and recommended in a New England Journal 
article that “better strategies are needed to inform decisions…in routine clinical practice.”   
In September 2015, a new FDA-approved test became available at Beaumont, 
computed tomography-derived fractional flow reserve (CT-FFR, provided by 
HeartFlow, Inc.), that provides flow information directly from computational fluid 
dynamic analysis of CCTA images without further testing7- 15.This analysis does not 
involve any additional imaging, contrast or medications. CT-FFR has been shown to 
be more accurate in predicting the presence of true ischemia on invasive fractional 
flow reserve testing in the invasive catheterization laboratory (CATH-FFR). Patients 
managed by CATH-FFR have been shown to have better outcomes than patients 
managed using visual inspection of CATH stenosis alone. The standard cutoff for an 
abnormal CATH-FFR and CT-FFR is the measurement of a blood pressure drop of 
≥20% (FFR ≤0.80) across a given stenosis. 
For Beaumont ED patients, CT-FFR has been in use on a research basis since 
September, 2015, but is not considered standard of care. Since September 2015 
we have conducted a study to analyze clinical outcomes after CT-FFR, (a sub-
analysis of HIC #2016-157, the Beaumont CT Registry). We have collected, 
analyzed data and submitted for publication, data on 147 ED patients with CCTA 
stenosis of 25-99% managed with CT-FFR and followed for a minimum of 90 
days. These data show no evidence to date of increased risk, but do show 
improved prediction of the need for revascularization using CT-FFR (see 
Appendix, submitted for publication). 
The objective of the present trial is to evaluate the CATH rate and diagnostic 
effectiveness of CT-FFR as compared to a standard of care diagnostic strategy (SOC) 
in the management of ACP patients with intermediate-to-severe stenosis on CCTA. 
 
Hypotheses: 
 
Primary Hypothesis: 
 
Cardiac Catheterization Rate: Use of CT-FFR will reduce the CATH rate in ACP 
patients with >50% stenosis on CCTA. There will be a pre-specified subset analysis of 
the Intermediate (51-70%) and Severe (71-90%) stenosis groups. 
 
 

 
 
Secondary Hypotheses: 
 
1. Diagnostic Effectiveness: CT-FFR results will more accurately triage patients to 
CATH compared to patients triaged by SOC. True flow-limiting coronary stenosis 
will be defined by CATH-FFR as the gold standard in patients undergoing CATH. 
Accurate triage will be calculated as the proportion of patients with correct triage 
to CATH based on CATH-FFR results: 
 
CT-FFR group:  
 
True positive case: CT-FFR positive and CATH-FFR positive 
 
True negative case: CT-FFR negative and CATH-FFR negative 
Proportion of correct CT-FFR triage = (True positive + True negative)/ All 
CATH 
 
SOC group: 
True positive case: SOC chosen by attending physician for CATH confirmed by 
CATH-FFR. By definition, the clinicians’ decision to CATH based on clinical 
evidence is considered an SOC positive case, there can be no SOC true negative 
cases that go to CATH. 
 
Proportion of correct SOC triage = True positive/All CATH 
 
2. Safety: Patients following CT-FFR-guided management will have similar MACE 
rates, including death, ACS and unanticipated late revascularization when 
compared to SOC-guided patients. 
 
 
Methods 
 
Study Population 
 
The study population will be drawn from ED ACP who have already undergone 
CCTA for diagnosis, and have been found to have 50% or greater stenosis but less 
than 90% of at least one coronary branch. Two-hundred patients meeting entry 
criteria will be enrolled from a sample of ED ACP patients at Beaumont Hospital 
(Royal Oak).These patients will be randomized 1:1 using sealed envelopes 
provided by the study statistician, to either standard of care (SOC) or CT-FFR 
management. (See Figure 1. Study Diagram) 
 
Inclusion Criteria 
 
1. Emergency department or inpatients admitted through the ED with chest pain 
suspicious for ACS based on history and physical examination. 
2. At least one biomarker (troponin) and electrocardiogram with no evidence 
of definite ACS. 
3. A completed CCTA demonstrating ≥50% but <90% stenosis of at least one 
coronary artery branch. 
4. CCTA test images with sufficient diagnostic quality for CT-FFR analysis. 
5. Ability and willingness to provide informed consent. 

 
 
Exclusion Criteria 
 
1. Left main coronary stenosis of 50% or greater. 
2. CCTA lesions demonstrating stenosis >90% (“subtotal”), or complex, high-
risk plaque characteristics resulting in an a priori recommendation for 
triage to CATH by CCTA interpreting physician. 
3. Attending physician a priori decision for CATH. 
4. Prior coronary stent, coronary bypass or prior known myocardial infarction.  
5. Clinical instability, such as hypotension, signs of shock, and/or unrelieved or 
accelerating chest pain.  
6. Pregnancy 
Obtaining Consent 
Consent will be obtained by a co-investigator. Patients will have at least 20 minutes 
to consider whether they wish to consent. 
 
Screening Log 
 
A screening log will be maintained by research coordinators of all patients who 
were considered for enrollment and their demographics, clinical characteristics and 
the reason for their exclusion. 
 
Sample Size 
 
Our primary outcome is the CATH rate at 3 months. Based on our previous analyses 
from our IRB 2016-157 study (the FFR-ACP study), the SOC arm had a 89.5% CATH 
rate in the 71-99% stenosis group and 58.3% in the 51-70% stenosis group. With the 
51-70% stenosis group having twice as many patients as the 71-99% group, we 
anticipate 68.7% of CATHs in all SOC controls. In our previous CT-FFR negative 
patients, there were 65.6% CATHs in the 71-99% stenosis group and 21.3% in the 51-
70% stenosis group. Again with a 2 to 1 ratio, we anticipate an overall CATH rate of 
36.1% in the FFR patients. Since these are estimates for the FFR group, we calculated 
several possibilities. All have 90% power with a significance level of 0.05%.   
  
We determined a sample size of 87 patients per arm are needed to detect this 
difference. We intend to randomize 100 patients per arm to adjust for any lost to 
follow-up. We used PASS 15 Power Analysis and Sample Size Software (2017). NCSS, 
LLC. Kaysville, Utah, USA, ncss.com/software/pass. 
  
Numeric Results for Testing Two Proportions using the Z-Test with Unpooled Variance 
H0: P1 - P2 = 0.   H1: P1 - P2 = D1 ≠ 0. 
Target             Actual                                                                                                                         
Diff                                              
Power           Power*              N1                N2                  N                  P1                P2                 D1            
Alpha                       
0.90              0.90148               44                44                88          0.6870        0.3600          0.3270          
0.0500                       
0.90              0.90458               59                59              118          0.6870        0.4000          0.2870          
0.0500                       

 
 
0.90              0.90155               87                87              174          0.6870        0.4500          0.2370          
0.0500                       
* Power was computed using the normal approximation method. 
 
Randomization 
 
We intend to include 200 patients (100 per arm). Patients will be randomized in a 
1:1 ratio to Standard of Care (SOC) or CT-FFR-guided management, in alternating 
block design to ensure equal groups periodically. The order of randomization will be 
generated using SAS for Windows 9.3, Cary, NC. Randomization envelopes will be 
generated by a Beaumont Research Biostatistician and will be opened in sequential 
order. Once the patient has met all the inclusion criteria, none of the exclusion 
criteria and has signed the informed consent, the next envelope will be opened which 
will contain a slip indicating the patients assigned study number and to which arm 
they are being randomized. 
 
SOC Group Management 
 
Attending physicians will dictate SOC management according to their own clinical 
judgment. This could include discharge without further testing, EKG-only stress 
testing, stress echocardiography, stress myocardial perfusion imaging, direct 
admission and further noninvasive testing or CATH. In addition to standard 
testing, a blinded CT-FFR will be obtained for post hoc analysis, but it will not be 
used for patient management. Image data from our CT workstation will be sent 
directly to HeartFlow, Inc. over a secure research transfer node. 
If attending physicians decide that SOC Group patients should undergo 
CATH, the protocol will specify an invasive fractional flow reserve will be 
performed on all lesions over 30% stenosis severity, to confirm the presence or 
absence of flow-limiting stenosis. This may be waived without protocol deviation 
if deemed unsafe by the severity of stenosis or due to clinical circumstances, as 
documented in a completed Physician Study Questionnaire. 
 
CT-FFR-Guided Group Management 
 
Patients in this group will be triaged using CT-FFR. Image data from our CT 
workstation will be sent directly to HeartFlow, Inc. over a secure Priority (STAT) 
transfer node. Interpreting physician will categorize CT-FFR results as follows: 
 
1. CT-FFR >0.80. All CT-FFR segmental values are >0.80, with no indication of flow 
limiting ischemia. A non-binding recommendation that the patient undergo an 
initial trial of medical therapy will be made by the interpreting co-investigator. 
Attending physicians will be asked to complete a study Physician Questionnaire 
to determine whether they followed this recommendation or not, and if not, why 
not.  
2. CT-FFR 0.70-0.80. These will be reported as values in the abnormal range 
without specific recommendations about whether CATH should be performed. 
Attending physicians will decide triage in consideration with other clinical data. 
Attending physicians will be asked to complete a study Physician Questionnaire 
to determine what clinical factors influenced their triage decision. 

 
 
3. CT-FFR <0.70. These are abnormal values that are will be reported as high-risk. A non-
binding recommendation that the patient undergo CATH will be made by the 
interpreting co-investigator. Attending physicians will be asked to complete a 
study Physician Questionnaire to determine whether they followed this 
recommendation or not, and if not, why not.  
 
If attending physicians decide that study patients should undergo CATH, the 
protocol will specify that CATH-FFR will be performed on all lesions over 30% 
stenosis severity, to confirm the presence or absence of flow-limiting stenosis 
prior to coronary intervention or triage to medical therapy. This may be waived 
without protocol deviation if deemed unsafe due to the severity of stenosis or due 
to other clinical circumstances, as documented on the Physician Study 
Questionnaire. 
 
Clinical Follow-up 
 
Patients will be followed at 1 month, 3 month and 1 year using a chart review and 
structured telephone interviews. Permission will be requested from patients for 
examination of outside medical records including office records and hospital 
records related to coronary artery disease. 
 
Risks of the Study 
 
Both the SOC and CT-FFR management strategies are currently used routinely at 
Beaumont Health, where ED patients’ diagnostic strategy is selected according to the 
preference of their individual attending physician.  There is no risk from the research 
study associated with CCTA testing, as patients will already have completed a 
clinically ordered CCTA test prior to their eligibility for the study. 
Both SOC and CT-FFR Group patients will undergo CATH if indicated by the 
results of noninvasive evaluation by CT-FFR or SOC physicians’ clinical judgment. 
Based on the baseline year prior to CT-FFR (Sept. 2014 – Aug. 2015), the CATH rate 
in SOC group patients was 58%. The CATH rate in CT-FFR patients during the 
previous research period (IRB #2016-157) from Sept. 2015 – Dec. 2016 was 
similar, at 79/147 patients, or 54%. Thus, the risk from the incidence of CATH was 
similar in the two groups. The study protocol does require CATH-FFR in patients 
undergoing CATH (unless there are no lesions >30%). There is a theoretical risk of 
rare (<1%) vascular injury due to the CATH-FFR catheter, however, CATH-FFR is a 
standard clinically recommended procedure prior to revascularization in CATH 
patients to insure accurate diagnosis of flow-limiting stenosis. If attending 
physicians believe there is a clinical reason that CATH-FFR should not be done, such 
as a lesion that is too severe, it may be omitted without protocol deviation, as long 
as the reason is documented in the Physician Study Questionnaire. The additional 
radiation risk added by CATH-FFR is estimated at <1 mSv, equivalent to <1 year of 
annual background radiation from environmental sources. 
 
 
 

 
 
Risks Associated with Heart Catheterization and Invasive Fractional Flow Reserve 
 
Common (more than 10%) 
• warm feeling or flushed feeling during adenosine infusion (which is 
part of the FFR study) 
• lightheadedness 
• nausea 
• pain 
• discomfort 
• bruising or bleeding where the catheter is inserted in the groin 
• radiation equivalent to 3-5 years of natural background radiation 
 
 
Rare (less than 1%) 
• contrast (dye) allergy 
• diaphoresis (temporary excessive sweating) 
• atrioventricular block -impaired conduction of the impulse that regulates 
the heartbeat (from adenosine) 
• contrast induced nephropathy (deterioration of kidney function 
due to contrast exposure) 
• hives (for those allergic to contrast dye) 
• thrombosis (blood clots resulting in reduced blood flow) 
 
• artery dissection (damage to the artery wall) 
• 
perforation (a hole in the artery) 
• 
stroke 
• 
myocardial infarction (heart attack) 
• 
death 
 
Internal Safety Monitoring Committee 
 
An Internal Safety Monitoring Committee will conduct regularly scheduled reviews 
of the safety of patients. Two physicians and a statistician who are not co-
investigators will be included. Members will monitor safety outcomes, enrollment 
and completeness of follow-up. The Committee will meet after the first 20 patients 
and after each 40 subsequent patients till the study is completed. Any MACE event 
or major adverse outcome will be reported immediately to the Committee. The 
results of all Committee meetings will be provided to the IRB. 
Data Analysis 
 
Descriptive statistics will be given for all variables collected including indications 
for the test, demographics, patient history, CTA tech information, details from the 
physicians reading form, and from the CT-FFR. Missing data will remain missing 
and will not be replaced by substitutions or interpolation. Categorical variables will 
be summarized as counts and percentages. All continuous variables will be 

 
 
summarized as means+/- the standard deviation where normal or median and 25th, 
75th percentiles if not normal.  The minimum and maximum will also be provided. 
 
Catheterization Rate: The primary outcome will be examined between the 2 
randomization arms using Pearson’s Chi-square test. The Odds ratio and 95% 
confidence interval will also be reported. 
 
Diagnostic Effectiveness: The secondary outcome will be defined as the proportion of 
accurate triage using CATH-FFR as the gold standard among all patients triaged to 
CATH by each strategy. 
 
The SOC group will be analyzed according to actual triage decisions, as well as the 
hypothetical results of triage using a blinded CT-FFR analysis collected on those 
patients. The accuracy of triage between these two methods will then be compared. 
 
Safety: The secondary outcome will be safety, as defined by the incidence of death, 
ACS or late unscheduled revascularization in each group. 
 
Additional data analysis: 
 
The Total length of stay, with sub-analysis of ED and inpatient length of stay will be 
reported as medians, 25th and 75th percentiles and minimum to maximum. The 2 
randomization arms will be examined for each of these using Wilcoxon rank sum 
tests. 
 
The hospital admission rate, the proportion of patients going to CATH in either arm 
who are found to have significant coronary stenosis (>50 stenosis), proportion of 
patients going to CATH who have a positive invasive FFR, percentage of patients 
undergoing PCI or CABG within 3 months, secondary diagnostic testing during 
index visit or within 3 months follow-up, including: recurrent ED visits, inpatient 
admissions for suspected acute coronary syndromes and/or CATH, outpatient or 
inpatient evaluation with cardiac CCTA or stress testing, cardiac surgery or PCI and 
MACE events (including all cause death, acute myocardial infarction, acute coronary 
syndromes, unscheduled revascularization after index visit) will be examined 
between the 2 arms using Pearson’s Chi-square test where appropriate (Expected 
frequency>5 in all cells), otherwise Fisher’s Exact tests will be used. The Odds ratios 
and 95% confidence intervals will also be reported. 
 
Estimated costs of care: including all estimated charges based on Beaumont 
hospital analysis multiplied by the standard Medicare cost/charge ratio will be 
reported as medians, 25th and 75th percentiles and minimum to maximum. The 2 
randomization arms will be examined using Wilcoxon rank sum tests. 
 
We may explore possible associations between patient characteristics demographics, 
prior history or testing indications and the randomization groups, safety outcomes, 

 
 
or events using contingency table methods, t tests or Wilcoxon Rank Sum, as 
appropriate. 
Associations 
between 
radiation 
dose/efficiency 
and 
patient 
characteristics may be explored with nonparametric methods. We may also explore 
possible relationships between the CTA stenosis categories (0%, 1-49%, 50- 100%) 
and the CT-FFR final test results categories and CATH and revascularization results. 
The occurrence of clinical events recorded at the 3 month chart review and 
structured patient questionnaire will be related to the category of final noninvasive 
results (Normal, Probably Normal, Equivocal, Probably Abnormal and Abnormal) 
using methods for contingency tables which incorporate the natural ordering of test 
categories. Odds ratios (ORs) with associated 95% confidence intervals (CIs) may be 
shown relating the occurrence of safety outcomes to test response categories with 
the normal category as the reference point. 
 
Analysis will be completed by a Beaumont Research Institute biostatistician using 
The SAS System for Windows version 9.3 (or higher). 

 
 
 
Figure 1 - Study Diagram 
 

 
 
 
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Appendix: Graph of Revascularization Rate by CT-FFR Results 
 
From: Utility of Fractional Flow Reserve by Coronary CT Angiography in Acute 
Chest Pain. Chinnaiyan, Raff, et al. Submitted to Journal American College of 
Cardiology, July 2017 
 
 
 
The relationship between cumulative revascularization with CT-FFR results among the three 
stenosis categories. In stenosis <50%, two patients underwent PCI, of which one had positive 
FFRCT. Among patients with 50-70% and >70% stenosis, those with positive CT-FFR had higher 
revascularization (68.2% vs. 9.1%, p<0.0001 and 86.4% vs. 30%, p=0.003). The low rate of 
revascularization in CT-FFR negative patients suggests that a trial of medical therapy in such 
patients will be safe.