Correlation of FFR CT With Invasive FFR in Multi-ethnic Cohort- a Retrospective Study

This retrospective study will analyse the existing Computed Tomography Coronary Angiogram (CTCA) database for patients treated at Sandwell and West Birmingham (SWBH) National Health Service (NHS) Trust between January 1, 2019, and December 31, 2023, with the clinical team screening the database to identify patients who fit with the eligibility criteria.

The proposed study is a retrospective analysis of the clinical and imaging data over a five-year period in patients with stable chest pain (approximately 500 patients), who underwent CTCA, FFR CT, and invasive FFR at SWBH NHS Trust. The study will assess the correlation between these diagnostic measures. The aim of this investigation is to address the ongoing discrepancies in the diagnostic accuracy of FFR CT compared to the gold standard invasive FFR, which persist despite the increasing adoption of FFR CT in clinical practice. While initial trials indicated promising sensitivity and specificity for FFR CT, recent observational studies including one involving 2,298 patients who underwent FFR CT, reported varying positive and negative predictive values, with a low positive predictive value of 49% (24). This variability raised concerns about the reliability of FFR CT across different patient populations, and the real-world accuracy and cost-effectiveness of FFR CT remain subjects of ongoing debate.

This study aims to examine the correlation between FFR CT and invasive FFR in a real-world setting using existing data, providing practical insights directly applicable to patient care. By confirming or examining the accuracy of FFR CT in a clinical setting, our analysis could support its broader adoption as a routine non-invasive diagnostic tool potentially (a) reducing the need for invasive testing (b) minimising associated risks, and(c) lowering healthcare costs and provide fresh insights into non-invasive coronary diagnostics. Our findings will also help understand the relevance of these tests across different ethnic groups and the population the investigators serve.

The patient data will be identified by accessing the CTCA database, and the study will adhere to the STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) guidelines (25).

The eligibility criteria are as follows:

• Patients aged 18 years and above.
• Patients presenting to the hospital with stable chest pain.
• Patients who have undergone both FFR CT and invasive FFR. Ethical approval will be obtained through the Integrated Research Application System (IRAS).

The patient's information will be collected by members of the research team, including demographic data such as age, gender, body mass index (BMI), and cardiovascular risk factors (e.g., smoking, hypertension, and diabetes). Vessel characteristics, including the coronary artery involved, location, and degree of stenosis, will also be recorded. Results of FFR CT and Invasive Coronary Angiogram (ICA) findings (if performed), as well as diagnostic performance metrics-sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of FFR CT in comparison to invasive FFR-along with downstream testing and imaging data, will be extracted from the CTCA database. All data will be coded and anonymised to ensure patient confidentiality and stored on NHS Trust computers with individual, password-protected logins. Only members of the research team involved in the study will have access to these computers.

The investigators will ensure all data collected, stored, and used complies with data protection laws, including the General Data Protection Regulation (GDPR) and the UK Data Protection Act 2018. Patient information will be anonymised to maintain confidentiality. The data will be securely stored on NHS computers at SWBH and used solely for this research.

An overview of the patient cohort will be provided, including demographics and clinical characteristics. Additionally, a detailed comparison of the diagnostic accuracy of FFR CT versus invasive FFR will be presented, including sensitivity, specificity, PPV, NPV, and overall accuracy.

Furthermore, the correlation between FFR CT and invasive FFR values will be explored, with a focus on any significant findings or discrepancies that may arise, offering insights into the diagnostic performance of FFR CT in comparison to the gold standard.

Statistical analysis will be performed using SPSS software, version 27. Continuous variables will be presented as mean ± standard deviation (SD) and compared using the Mann-Whitney U test or Analysis of Variance (ANOVA), as appropriate. Categorical variables will be expressed as percentages and compared using the chi-square test. Sensitivity, specificity, PPV, and NPV will be calculated based on the correlation between FFR CT and invasive FFR.

Inclusion Criteria:

Patients meeting all the below criteria will be included.

•≥18 years

• Stable •patients with suspected CAD
• Patients who underwent CTCA, FFR CT and had an invasive FFR.
• CTCA images of high-quality for analysis, with clear visualisation of coronary arteries and minimal artifacts.

Exclusion criteria:

Patients meeting any of the following criteria will be excluded.

• <18 years of age
• Did not undergo FFR CT
• Inadequate quality/degraded CTCA images Online database on password protected NHS TRUST computer to collect demographic parameters of all patients i.e. age, sex, BMI along with history of disease, coexisting morbidities like hypertension, diabetes and hyperlipidaemia procedural and outcome information.

Demographics (age, gender, ethnicity socio economic status), BMI and cardiovascular risk factors) vessel characteristics, FFR CT values and invasive FFR values will be obtained.

Categorical variables will be compared by chi square test or Fisher's test and continuous variables will be compared by Mann Whitney U test Ethical approval for this retrospective study will be obtained through IRAS application.

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