Machine learning-based CT fractional flow reserve assessment in acute chest pain: first experience

Abstract

Background: Computed tomography (CT)-derived fractional flow reserve (FFRCT) enables the non-invasive functional assessment of coronary artery stenosis. We evaluated the feasibility and potential clinical role of FFRCT in patients presenting to the emergency department with acute chest pain who underwent chest-pain CT (CPCT).

Methods: For this retrospective IRB-approved study, we included 56 patients (median age: 62 years, 14 females) with acute chest pain who underwent CPCT and who had at least a mild (≥25% diameter) coronary artery stenosis. CPCT was evaluated for the presence of acute plaque rupture and vulnerable plaque features. FFRCT measurements were performed using a machine learning-based software. We assessed the agreement between the results from FFRCT and patient outcome (including results from invasive catheter angiography and from any non-invasive cardiac imaging test, final clinical diagnosis and revascularization) for a follow-up of 3 months.

Results: FFRCT was technically feasible in 38/56 patients (68%). Eleven of the 38 patients (29%) showed acute plaque rupture in CPCT; all of them underwent immediate coronary revascularization. Of the remaining 27 patients (71%), 16 patients showed vulnerable plaque features (59%), of whom 11 (69%) were diagnosed with acute coronary syndrome (ACS) and 10 (63%) underwent coronary revascularization. In patients with vulnerable plaque features in CPCT, FFRCT had an agreement with outcome in 12/16 patients (75%). In patients without vulnerable plaque features (n=11), one patient showed myocardial ischemia (9%). In these patients, FFRCT and patient outcome showed an agreement in 10/11 patients (91%).

Conclusions: Our preliminary data show that FFRCT is feasible in patients with acute chest pain who undergo CPCT provided that image quality is sufficient. FFRCT has the potential to improve patient triage by reducing further downstream testing but appears of limited value in patients with CT signs of acute plaque rupture.

Keywords: Acute coronary syndrome (ACS); computed tomography angiography; fractional flow reserve; machine learning; myocardial.

Conflict of interest statement

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/cdt-20-381). The authors have no conflicts of interest to declare.

2020 Cardiovascular Diagnosis and Therapy. All rights reserved.

Figures

Figure 1

Study flow chart. A positive FFRCT (FFRCT+) result was defined as ≤0.8, a negative FFRCT (FFRCT-) as >0.8. CABG, coronary artery bypass grafting; CT, computed tomography; ECG, electrocardiogram; FFRCT, CT-derived fractional flow reserve; ICA, invasive coronary angiography; MRI, magnetic resonance imaging; PCI, percutaneous coronary intervention; SPECT, single-photon emission CT.

Figure 2

A 32-year-old male patient presenting to the emergency department with acute chest pain, slightly elevated cardiac biomarkers, and a history of pulmonary embolism. After leaving the emergency department against medical advice, the patient returned two days later with persistent symptoms. Cardiovascular risk factors were a positive family history, dyslipidemia, and smoking. The patient refused to undergo invasive coronary angiography (ICA) but agreed on having CT. Chest-pain CT was performed to rule-out recurrent pulmonary embolism and acute coronary syndrome. CT showed hazy intraluminal hypodense material in the mid RCA with positive remodelling, suspicious for acute plaque rupture (A-C). Lesion specific FFRCT was 0.89 (D), which indicates the absence of lesion-specific ischemia. ICA confirmed a thrombus in the mid RCA most probably due to acute plaque rupture (E). Subsequent coronary intervention with stent placement was performed.

Figure 3

A 52-year-old male patient presenting to the emergency department with acute chest pain, dyspnea, and vagal symptoms after a transatlantic flight. The patient had a short episode of dyspnea and chest pain while running some hours before the flight. Laboratory tests revealed borderline troponin elevation with normal creatine kinase levels. ECG showed sinus rhythm with ST-segment depression in leads I and II. To rule out pulmonary embolism, acute aortic syndrome, and acute coronary syndrome the patient underwent chest-pain CT. CT ruled out acute aortic syndrome and pulmonary embolism, but showed a severe stenosis in the mid LAD (A and B) with a lesion-specific FFRCT of 0.73 (C). Invasive coronary angiography confirmed an 80% stenosis of the mid LAD (D), which was successfully treated with a bioabsorbable vascular scaffold (E).